TRANSCRIBER'S NOTES
Italic text is denoted by _underscores_.
The oe ligature has been expanded to 'oe'.
Subscripts in chemical formulas are denoted by normal numbers;
for example CaC2.
Obvious typographical and punctuation errors have been corrected
after careful comparison with other occurrences within the text
and consultation of external sources.
More detail can be found at the end of the book.
[Illustration: A PRIMITIVE USE OF THE ANIMAL MACHINE THAT IS STILL IN
VOGUE IN MANY EUROPEAN COUNTRIES.
(From the painting by J. Didier, in the _Musée du Luxembourg_, Paris.)]
EVERY-DAY SCIENCE
BY
HENRY SMITH WILLIAMS, M.D., L.L.D.
ASSISTED BY
EDWARD H. WILLIAMS, M.D.
VOLUME VI
THE CONQUEST OF NATURE
ILLUSTRATED
NEW YORK AND LONDON
THE GOODHUE COMPANY
PUBLISHERS MDCCCCIX
Copyright, 1910, by THE GOODHUE CO.
_All rights reserved_
CONTENTS
CHAPTER I
MAN AND NATURE
The Conquest of Nature, p. 4--Man's use of Nature's gifts, p.
6--Man the "tool-making animal," p. 7--Science and Civilization,
p. 8--Clothing and artificially heated dwellings of primitive man,
p. 10--Early domestication of animals, p. 11--Early development to
the time of gunpowder, p. 12--The coming of steam and electricity,
p. 15--Mechanical aids to the agriculturist, p. 19--The development
of scientific agriculture, p. 20--Difficulties of the early
manufacturer, p. 21--The development of modern manufacturing, p.
24--The relation of work to human development, p. 25--The decline of
drudgery and the new era of labor-saving devices, p. 27.
CHAPTER II
HOW WORK IS DONE
Primitive man's use of the lever, p. 29--The use of the lever as
conceived by Archimedes, p. 21--Wheels and pulleys, p. 32--Other
means of transmitting power, p. 35--Inclined planes and derricks, p.
37--The steam-scoop, p. 38--Friction, p. 39--Available sources of
energy, p. 41.
CHAPTER III
THE ANIMAL MACHINE
The oldest machine in existence, p. 43--The relation of muscle
to machinery, p. 44--How muscular energy is applied, p. 44--The
two types of muscles, p. 45--How the nerve-telegraph controls the
muscles, p. 47--The nature of muscular action, p. 49--Applications
of muscular energy, p. 52--The development of the knife and saw, p.
53--The wheel and axle, p. 55--Modified levers, p. 57--Domesticated
animals, p. 59--Early application of horse-power, p. 60--The
horse-power as the standard of the world's work, p. 61.
CHAPTER IV
THE WORK OF AIR AND WATER
First use of sails for propelling boats, p. 62--The fire engine of
Ctesibius, p. 63--Suction and pressure as studied by the ancients, p.
64--Studies of air pressure, p. 65--The striking demonstration of Von
Guericke, p. 66--The sailing chariot of Servinus, 1600 A.D.,
p. 68--The development of the windmill, p. 69--The development of the
water-wheel, p. 70--The invention of the turbine, p. 72--Different
types of turbines, p. 73--Hydraulic power and its uses, p. 74--The
hydraulic elevator, p. 76--Recent water motors, p. 77.
CHAPTER V
CAPTIVE MOLECULES: THE STORY OF THE STEAM ENGINE
The development of the steam engine, p. 79--The manner in which
energy is generated by steam, p. 80--Action of cylinder and piston,
p. 81--Early attempts to utilize steam, p. 82--Beginnings of modern
discovery, p. 83--The "engine" of the Marquis of Worcester, p.
84--Thomas Savery's steam pump, p. 85--Denis Papin invents the piston
engine, p. 88--Newcomen's improved engine, p. 89--The use of these
engines in collieries, p. 90--The wastefulness of such engines, p.
92--The coming of James Watt, p. 93--Early experiments of Watt, p.
95--The final success of Watt's experiments, p. 97--Some of his early
engines, p. 98--Rotary motion, p. 99--Watt's engine, "Old Bess,"
p. 101--Final improvements and missed opportunities, p. 102--The
personality of James Watt, p. 107.
CHAPTER VI
THE MASTER WORKER
Improvements on Watt's engines, p. 110--Engines dispensing with the
walking beam, p. 111--The development of high-pressure engines, p.
112--Advantages of the high-pressure engine, p. 114--How steam acts
in the high-pressure engine, p. 116--Compound engines, p. 117--Rotary
engines, p. 119--Turbine engines, p. 124--The _Turbinia_ and other
turbine boats, p. 125--The action of steam in the turbine engine, p.
126--Advantages of the turbine engine, p. 127.
CHAPTER VII
GAS AND OIL ENGINES
Some early gas engines, p. 133--Dr. Stirling's hot-air engine, p.
133--Ericsson's hot-air engines, p. 134--The first practical gas
engine, p. 135--The Otto gas engine, p. 136--Otto's improvement by
means of compressed gas, p. 138--The "Otto cycle," p. 139--Adaptation
of gas engines to automobiles, p. 140--Rapid increase in the use
of gas engines, p. 141--Defects of the older hot-air engines, p.
145--Recent improvements and possibilities in the use of hot-air
engines, p. 146.
CHAPTER VIII
THE SMALLEST WORKERS
The relative size of atoms and electrons, p. 148--What is
electricity? p. 149--Franklin's one-fluid theory, p. 150--Modern
views, p. 153--Cathode rays and the X-ray, p. 156--How electricity
is developed, p. 159--The work of the dynamical current, p.
162--Theories of electrical action, p. 165--Practical uses of
electricity, p. 168.
CHAPTER IX
MAN'S NEWEST CO-LABORER: THE DYNAMO
The mechanism of the dynamo, p. 173--The origin of the dynamo, p.
176--The work of Ampère, Henry, and Faraday, p. 177--Perfecting the
dynamo, p. 178--A mysterious mechanism, p. 180--Curious relation
between magnetism and electricity as exemplified in the dynamo, p.
182.
CHAPTER X
NIAGARA IN HARNESS
The volume of water at the falls, p. 184--The point at which
the falls are "harnessed," p. 185--Within the power-house, p.
186--Penstocks and turbines, p. 188--A miraculous transformation
of energy, p. 189--Subterranean tail-races, p. 191--The effect on
the falls, p. 192--The transmission of power, p. 194--"Step-up" and
"step-down" transformers, p. 198.
CHAPTER XI
THE BANISHMENT OF NIGHT
Primitive torch and open lamp, p. 202--Tallow candle and perfected
lamp, p. 205--Gas lighting, p. 207--The incandescent gas mantle, p.
208--Early gas mantles, p. 209--How the incandescent gas mantle is
made, p. 211--The introduction of acetylene gas, p. 212--Chemistry
of acetylene gas, p. 214--Practical gas-making, p. 215--The triumph
of electricity, p. 218--Davy and the first electric light, p.
220--Helpful discoveries in electricity, p. 222--The Jablochkoff
candle, p. 223--Defects of the Jablochkoff candle, p. 225--The
improved arc light, p. 226--Edison and the incandescent lamp, p.
228--Difficulties encountered in finding the proper material for
a practical filament, p. 230--"Parchmentized thread" filament, p.
233--The tungsten lamp, p. 234--The mercury-vapor light of Peter
Cooper Hewitt, p. 236--Advantages and peculiarities of this light, p.
240.
CHAPTER XII
THE MINERAL DEPTHS
Early mining methods, p. 242--Prospecting and locating mines, p.
243--"Booming," p. 246--Conditions to be considered in mining,
p. 248--Dangerous gases in mines, p. 249--Artificial lights and
lighting, p. 251--Ventilation and drainage, p. 252--Electric
machinery in mining, p. 253--Electric drills, p. 254--Traction in
mining, p. 256--Various types of electric motors, p. 257--"Telphers,"
p. 261--Electric mining pumps, p. 263--Some remarkable demonstrations
of durability of electric pumps, p. 265--Electricity in coal mining,
p. 266--Electric lighting in mines, p. 269.
CHAPTER XIII
THE AGE OF STEEL
Rapid growth of the iron industry in recent years, p. 271--The Lake
Superior mines, p. 272--Methods of mining, p. 273--"Open-pit" mining,
p. 274--Mining with the steam shovel, p. 276--From mine to furnace,
p. 278--Methods of transportation, p. 279--Vessels of special
construction, p. 281--The conversion of iron ore into iron and steel,
p. 283--Blast furnaces, p. 284--Poisonous gases and their effect
upon the workmen, p. 286--From pig iron to steel, p. 287--Modern
methods of producing pig iron, p. 288--The Bessemer converter, p.
289--Sir Henry Bessemer, p. 291--The "Bessemer-Mushet" process, p.
293--Open-hearth method, p. 294--Alloy steels, p. 295.
CHAPTER XIV
SOME RECENT TRIUMPHS OF APPLIED SCIENCE
The province of electro-chemistry, p. 298--Linking the laboratory
with the workshop, p. 299--Soda manufactories at Niagara Falls, p.
300--Producing aluminum by the electrolytic process, p. 300--Old and
new methods compared, p. 301--Nitrogen from the air, p. 303--What
this discovery means to the food industries of the world, p.
304--Prof. Birkeland's method, p. 307--Another method of nitrogen
fixation, p. 309--Cost of production, p. 312--Electrical energy,
p. 313--Production of high temperatures with the electric arc, p.
314--The production of artificial diamonds by the explosion of
cordite, p. 315--Industrial problems of to-day and to-morrow, p. 316.
ILLUSTRATIONS
A PRIMITIVE USE OF THE ANIMAL MACHINE THAT IS
STILL IN VOGUE IN MANY EUROPEAN COUNTRIES _Frontispiece_
HORSE AND CATTLE POWER _Facing p._ 32
CRANES AND DERRICKS " 38
A BELGIAN MILK-WAGON " 56
TWO APPARATUSES FOR THE UTILIZATION OF ANIMAL
POWER " 60
WINDMILLS OF ANCIENT AND MODERN TYPES " 68
WATER WHEELS " 72
HYDRAULIC PRESS AND HYDRAULIC CAPSTAN " 76
THOMAS SAVERY'S STEAM ENGINE " 86
DIAGRAMS OF EARLY ATTEMPTS TO UTILIZE THE POWER
OF STEAM " 88
A MODEL OF THE NEWCOMEN ENGINE " 92
WATT'S EARLIEST TYPE OF PUMPING-ENGINE " 96
WATT'S ROTATIVE ENGINE " 100
JAMES WATT " 108
OLD IDEAS AND NEW APPLIED TO BOILER CONSTRUCTION " 114
COMPOUND ENGINES " 118
ROTARY ENGINES " 122
THE ORIGINAL PARSONS' TURBINE ENGINE AND THE RECORD-BREAKING
SHIP FOR WHICH IT IS RESPONSIBLE " 128
GAS AND OIL ENGINES " 136
AN ELECTRIC TRAIN AND THE DYNAMO THAT PROPELS IT " 174
WILDE'S SEPARATELY EXCITED DYNAMO " 178
THE EVOLUTION OF THE DYNAMO " 180
VIEW IN ONE OF THE POWER HOUSES AT NIAGARA " 186
ELECTRICAL TRANSFORMERS " 198
THOMAS A. EDISON AND THE DYNAMO THAT GENERATED
THE FIRST COMMERCIAL INCANDESCENT LIGHT " 228
A FLINT-AND-STEEL OUTFIT, AND A MINER'S STEEL MILL " 248
THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN
COLLIERY TROLLEY " 258
THE CONQUEST OF NATURE
In the earlier volumes we have been concerned with the growth of
knowledge. For the most part the scientific delvers whose efforts have
held our attention have been tacitly unmindful, or even explicitly
contemptuous, of the influence upon practical life of the phenomena to
the investigation of which they have devoted their lives. They were and
are obviously seekers of truth for the mere love of truth.
But the phenomena of nature are not dissociated in fact, however
much we may attempt to localize and classify them. And so it chances
that even the most visionary devotee of abstract science is forever
being carried into fields of investigation trenching closely upon the
practicalities of every-day life. A Black investigating the laws of
heat is preparing the way explicitly, however unconsciously, for a Watt
with his perfected mechanism of the steam engine.
Similarly a Davy working at the Royal Institution with his newly
invented batteries, and intent on the discovery of new elements and the
elucidation of new principles, is the direct forerunner of Jablochkoff,
Brush, and Edison with their commercial revolution in the production of
artificial light.
Again Oersted and Faraday, earnestly seeking out the fundamental facts
as to the relations of electricity and magnetism, invent mechanisms
which, though they seem but laboratory toys, are the direct forerunners
of the modern dynamos that take so large a share in the world's work.
In a word, all along the line there is the closest association
between what are commonly called the theoretical sciences and what
with only partial propriety are termed the applied sciences. The
linkage of one with the other must never be forgotten by anyone who
would truly apprehend the status of those practical sciences which
have revolutionized the civilization of the nineteenth and twentieth
centuries in its most manifest aspects.
Nevertheless there is, to casual inspection, a somewhat radical
distinction between theoretical and practical aspects of science--just
as there are obvious differences between two sides of a shield.
And as the theoretical aspects of science have largely claimed our
attention hitherto, so its practical aspects will be explicitly
put forward in the pages that follow. In the present volume we are
concerned with those primitive applications of force through which
man early learned to add to his working efficiency, and with the
elaborate mechanisms--turbine wheels, steam engines, dynamos--through
which he has been enabled to multiply his powers until it is scarcely
exaggeration to say that he has made all Nature subservient to his
will. It is this view which justifies the title of the volume, which
might with equal propriety have been termed the Story of the World's
Work.
THE CONQUEST OF NATURE
I
MAN AND NATURE
"Young men," said a wise physician in addressing a class of graduates
in medicine, "you are about to enter the battle of life. Note that I
say the 'battle' of life. Not a playground, but a battlefield is before
you. It is a hard contest--a battle royal. Make no mistake as to that.
Your studies here have furnished your equipment; now you must go forth
each to fight for himself."
The same words might be said to every neophyte in whatever walk of
life. The pursuit of every trade, every profession is a battle--a
struggle for existence and for supremacy. Partly it is a battle against
fellow men; partly against the contending powers of Nature. The
physician meets rivalry from his brothers; but his chief battle is with
disease. In the creative and manufacturing fields which will chiefly
concern us in the following volumes, it is the powers of Nature that
furnish an ever-present antagonism.
No stone can be lifted above another, to make the crudest wall or
dwelling, but Nature--represented by her power of gravitation--strives
at once to pull it down again. No structure is completed before the
elements are at work defacing it, preparing its slow but certain ruin.
Summer heat and winter cold expand and contract materials of every
kind; rain and wind wear and warp and twist; the oxygen of the air
gnaws into stone and iron alike;--in a word, all the elements are at
work undoing what man has accomplished.
THE STRUGGLE FOR EXISTENCE
In the field of the agriculturist it is the same story. The earth which
brings forth its crop of unwholesome weeds so bountifully, resists
man's approaches when he strives to bring it under cultivation. Only by
the most careful attention can useful grains be made to grow where the
wildlings swarmed in profusion. Not only do wind and rain, blighting
heat and withering cold menace the crops; but weeds invade the fields,
the germs of fungoid pests lurk everywhere; and myriad insects attack
orchard and meadow and grain field in devastating legions.
Similarly the beasts which were so rugged and resistant while in
the wild state, become tender and susceptible to disease when made
useful by domestication. Aforetime they roamed at large, braving every
temperature and thriving in all weathers. But now they must be housed
and cared for so tenderly that they become, as Thoreau said, the
keepers of men, rather than kept by men, so much more independent are
they than their alleged owners. Tender of constitution, domesticated
beasts must be housed, to protect them from the blasts in which of yore
their forebears revelled; and man must slave day in and day out to
prepare food to meet the requirements of their pampered appetites.
He must struggle, too, to protect them from disease, and must care for
them in time of illness as sedulously as he cares for his own kith and
kin. Truly the ox is keeper of the man, and the seeming conquest that
man has wrought has cost him dear.
But of course the story has another side. After all, Nature is not so
malevolent as at first glance she seems. She has opposed man at every
stage of his attempted progress; yet at the same time she has supplied
him all his weapons for waging war upon her. Her great power of
gravitation opposes every effort he makes; yet without that same power
he could do nothing--he could not walk or stay upon the earth even; and
no structure that he builds would hold in place for an instant.
So, too, the wind that smites him and tears at his handiwork, may be
made to serve the purposes of turning his windmills and supplying him
with power.
The water will serve a like purpose in turning his mills; and, changed
to steam with the aid of Nature's store of coal, will make his steam
engines and dynamos possible. Even the lightning he will harness and
make subject to his will in the telegraphic currents and dynamos.
And in the fields, the grains which man struggles so arduously to
produce are after all no thing of his creating. They are only adopted
products of Nature, which he has striven to make serve his purpose by
growing them under artificial conditions. So, too, the domesticated
beasts are creatures that belong in the wilds and in distant lands. Man
has brought them, in defiance of Nature, to uncongenial climes, and
made them serve as workers and as food-suppliers where Nature alone
could not support them. Turn loose the cow and the horse to forage for
themselves here in the inhospitable north, and they would starve. They
survive because man helps them to combat the adverse conditions imposed
by Nature, yet no one of them could live for an hour were not the vital
capacities supplied by Nature still in control.
Everywhere, then, it is the opposing of Nature, up to certain limits,
with the aid of Nature's own tools, that constitutes man's work in the
world. Just in proportion as he bends the elements to meet his needs,
transforms the plants and animals, defies and exceeds the limitations
of primeval Nature--just in proportion as he conquers Nature, in a
word, is he civilized.
Barbaric man is called a child of Nature with full reason. He must
accept what Nature offers. But civilized man is the child grown to
adult stature, and able in a manner to control, to dominate--if you
please to conquer--the parent.
If we were to seek the means by which developing man has gradually
achieved this conquest, we should find it in the single word, Tools;
that is to say, machines for utilizing the powers of Nature, and, as
it were, multiplying them for man's benefit. So unique is the capacity
that man exerts in this direction, that he has been described as
"the tool-making animal." The description is absolutely accurate; it
is inclusive and exclusive. No non-human animal makes any form of
implement to aid it in performing its daily work; and contrariwise
every human tribe, however low its stage of savagery, makes use of more
or less crude forms of implements. There must have been a time, to be
sure, when there existed a man so low in intelligence that he had not
put into execution the idea of making even the simplest tool. But the
period when such a man existed so vastly antedates all records that it
need not here concern us. For the purpose of classifying all existing
men, and all the tribes of men of which history and pre-historic
archæology give us any record, the definition of man as the tool-making
animal is accurate and sufficient.
At first thought it might seem that an equally comprehensive definition
might describe man as the working animal. But a moment's consideration
shows the fallacy of such a suggestion. Man is, to be sure, the animal
that works effectively, thanks to the implements with which he has
learned to provide himself; but he shares with all animate creatures
the task of laboring for his daily necessities. This is indeed a
work-a-day world, and no creature can live in it without taking
its share in that perpetual conflict which bodily necessities make
imperative. Most lower animals confine their work to the mere securing
of food, and to the construction of rude habitations. Some, indeed,
go a step farther and lay up stores of food, in chance burrows or
hollow trees; a few even manufacture relatively artistic and highly
effective receptacles, as illustrated by the honeycomb made by the
bees and their allies. Again, certain animals, of which the birds
are the best representatives, construct temporary structures for the
purpose of rearing their young that attain a relatively high degree of
artistic perfection. The Baltimore oriole weaves a cloth of vegetable
fibre that is certainly a wonderful texture to be made with the aid of
claws and bill alone. It may be doubted whether human hands, unaided by
implements, could duplicate it. But it is crude enough compared with
even the coarsest cloth which barbaric races manufacture with the aid
of implements.
So it is with any comparison of animal work with the work of man, in
whatever field. The crudest human endeavor is superior to the best
non-human efforts; and the explanation is found always in the fact that
the ingenuity of man has enabled him to find artificial aids that add
to his power of manipulation. So large a share have these artificial
aids taken in man's evolution, that it has long been customary, in
studying the development of civilization, to make the use of various
types of implements a test of varying stages of human progress.
SCIENCE AND CIVILIZATION
The student of primitive life assures us, basing his statements on the
archæological records, that there was a time when the most advanced of
mankind had no tools made of better material than chipped stone. By
common consent that time is spoken of as the Rough Stone Age.
We are told that then in the course of immeasurable centuries man
learned to polish his stone implements, doubtless by rubbing them
against another stone, or perhaps with the aid of sand, thus producing
a new type of implement which has given its name to the Age of Smooth
or Polished Stone.
Then after other long centuries came a time when man had learned
to smelt the softer metals, and the new civilization which now
supplanted the old, and, thanks to the new implements, advanced upon it
immeasurably, is called the Age of Bronze.
At last man learned to accomplish the wonderful feat of smelting the
intractable metal, iron, and in so doing produced implements harder,
sharper, and cheaper than his implements of bronze; and when this
crowning feat had been accomplished, the Age of Iron was ushered in.
By common consent, students of the history of the evolution of society
accept these successive ages, each designated by the type of implements
with which the world's work was accomplished, as representing real and
definite stages of human progress, and as needing no better definition
than that supplied by the different types of implements.
Could the archæologist trace the stream of human progress still farther
back toward its source, he would find doubtless that there were several
great epochal inventions preceding the time of the Rough Stone Age,
each of which was in its way as definitive and as revolutionary in
its effects upon society, as these later inventions which we have just
named. To attempt to define them clearly is to enter the field of
uncertainty, but two or three conjectures may be hazarded that cannot
be very wide of the truth.
It is clear, for example, that if we go back in imagination to the very
remotest ancestors of man that can be called human, we must suppose a
vast and revolutionary stage of progress to have been ushered in by the
first race of men that learned to make habitual use of the simplest
implement, such as a mere club. When man had learned to wield a club
and to throw a stone, and to use a stone held in the hand to break the
shell of a nut, he had attained a stage of culture which augured great
things for the future. Out of the idea of wielded club and hurled stone
were to grow in time the ideas of hammer and axe and spear and arrow.
Then there came a time--no one dare guess how many thousands of years
later--when man learned to cover his body with the skin of an animal,
and thus to become in a measure freed from the thraldom of the weather.
He completed his enfranchisement by learning to avail himself of the
heat provided by an artificial fire. Equipped with these two marvelous
inventions he was able to extend the hitherto narrow bounds of his
dwelling-place, passing northward to the regions which at an earlier
stage of his development he dared not penetrate. Under stress of more
exhilarating climatic conditions, he developed new ideals and learned
to overcome new difficulties; developing both a material civilization
and the advanced mentality that is its counterpart, as he doubtless
never would have done had he remained subject to the more pampering
conditions of the tropics.
The most important, perhaps, of the new things which he was taught
by the seemingly adverse conditions of an inhospitable climate, was
to provide for the needs of a wandering life and of varying seasons
by domesticating animals that could afford him an ever-present food
supply. In so doing he ceased to be a mere fisher and hunter, and
became a herdsman. One other step, and he had conceived the idea of
providing for himself a supply of vegetable foods, to take the place
of that which nature had provided so bountifully in his old home in
the tropics. When this idea was put into execution man became an
agriculturist, and had entered upon the high road to civilization.
All these stages of progress had been entered upon prior to the time of
which the oldest known remains of the cave-dweller give us knowledge.
It were idle to conjecture the precise sequence in which these earliest
steps toward civilization were taken, and even more idle to conjecture
the length of time which elapsed between one step and its successor.
But all questions of precise sequence aside, it is clear that here were
four or five great ages succeeding one to another, that marked the
onward and upward progress of our primeval ancestor before he achieved
the stage of development that enabled him to leave permanent records of
his existence. And--what is particularly significant from our present
standpoint--it is equally clear that each of the great ages thus
vaguely outlined was dependent upon an achievement or an invention
that facilitated the carrying out of that scheme of never-ending work
which from first to last has been man's portion. How to labor more
efficiently, more productively; how to produce more of the necessaries
and of the luxuries that man's physical and mental being demands,
with less expenditure of toil--that from first to last has been the
ever-insistent problem. And the answer has been found always through
the development of some new species of mechanism, some new labor-saving
device, some ingenious manipulation of the powers of Nature.
If, turning from the hypothetical period of our primitive ancestor,
we consider the sweep of secure and relatively recent history, we
shall find that precisely the same thing holds. If we contrast the
civilization of Old Egypt and Babylonia--the oldest civilizations of
which we have any secure record--with the civilization of to-day, we
shall find that the differences between the one and the other are such
as are due to new and improved methods of accomplishing the world's
work.
Indeed, if we view the subject carefully, it will become more and
more evident that the only real progress that the historic period has
to show is such as has grown directly from the development of new
mechanical inventions. The more we study the ancient civilizations
the more we shall be struck with their marvelous resemblance, as
regards mental life, to the civilization of to-day. In their moral
and spiritual ideals, the ancient Egyptians were as brothers to the
modern Europeans. In philosophy, in art, in literature, the Age of
Pericles established standards that still remain unexcelled. In all the
subtleties of thought, we feel that the Greeks had reached intellectual
bounds that we have not been able to extend.
But when, on the other hand, we consider the material civilization of
the two epochs, we find contrasts that are altogether startling. The
little world of the Greeks nestled about the Mediterranean, bounded
on every side at a distance of a few hundred leagues by a _terra
incognita_. The philosophers who had reached the confines of the
field of thought, had but the narrowest knowledge of the geography of
our globe. They traversed at best a few petty miles of its surface
on foot or in carts; and they navigated the Mediterranean Sea, or at
most coasted out a little way beyond the Pillars of Hercules in boats
chiefly propelled by oars. By dint of great industry they produced a
really astonishing number of books, but the production of each one was
a long and laborious task, and the aggregate number indited during
the Age of Pericles in all the world was perhaps not greater than an
afternoon's output of a modern printing press.
In a word, these men of the classical period of antiquity, great as
were their mental, artistic, and moral achievements, were as children
in those matters of practical mechanics upon which the outward
evidences of civilization depend. Should we find a race of people
to-day in some hitherto unexplored portion of the earth--did such
unexplored portions still exist--living a life comparable to that
of the Age of Pericles, we should marvel no doubt at their artistic
achievements, while at the same time regarding them as scarcely better
than barbarians. Indeed this is more than unsupported hypothesis;
for has it not been difficult for the Western world to admit the
truly civilized condition of the Chinese, simply because that highly
intellectual race of Orientals has not kept abreast of the Occidental
changes in applied mechanics? Say what we will, this is the standard
which we of the Western world apply as the test of civilization.
If, sweeping over in retrospect the history of the world since the time
when the Egyptian and Babylonian civilizations were at their height,
we attempt some such classification of the stages of progress as that
which we a moment ago applied to pre-historic times, we shall be led to
some rather startling conclusions. In the broadest view, it will appear
that the age which ushered in the historic period continued unbroken
by the advance of any great revolutionary invention throughout the
long centuries of pre-Christian antiquity, and well into the so-called
Middle Ages of our newer era. Then came the invention of gunpowder, or
at least its introduction to the Western world--since the Chinaman here
lays claim to vague centuries of precedence. Following hard upon the
introduction of gunpowder, with its capacity to add to the destructive
efficiency of man's most sinister form of labor, came a mechanism no
less epoch-making in a far different field--the printing press.
But even these inventions, great as was their influence upon the
progress of civilization, can scarcely be considered, it seems to me,
as taking rank with the great epochal discoveries that gave their
names to the preceding ages. Nor can any invention of the sixteenth
or seventeenth century be hailed as really ushering in a new era. The
invention for which that honor was reserved was a development of the
eighteenth century; and did not come fully to its heritage until the
early days of the nineteenth century. The invention was the application
of steam to the purposes of mechanics. When this application was made,
as wide a gap was crossed as that which separated the Stone Age from
the Age of Metal; then the epoch in which the world was living when
history begins was brought to a close, and a new era, the Age of Steam,
was ushered in.
Scarcely had the world begun to adjust itself to the new conditions of
the Age of Steam, when yet another power was made subservient to man's
needs, and the Age of Steam was supplemented, not to say supplanted, by
the Age of Electricity. Of course the new progressive movements did not
necessarily imply elimination of old conditions; they imply merely the
subordination of old powers to newer and better ones. Stone implements
by no means ceased to have utility at once when metal implements came
into vogue. Bronze long held its own against iron, and still has its
utility. And iron itself finds but an added sphere of usefulness in the
Age of Steam and Electricity.
All great changes are relatively slow. It is only as we look back upon
them and view them in perspective that they seem cataclysmic. Gunpowder
did not at once supplant the crossbow, and the cannon was long held
to be inferior to the catapult. The printed book did not instantly
make its way against the work of the scribe. Neither did the steam
engine immediately supplant water power and the direct application of
human labor. But in each case the new invention virtually rang the
death knell of the old method from the hour of its inauguration, and
the end was no less sure because it was delayed. And it requires no
great powers of divination to foretell that in the coming age, the
electric dynamo driven by water power may take the place of the steam
engine. The Age of Steam may pass, with only at most a few generations
of domination. And it is within the possibilities that the Age of
Electricity will scarcely come into its own before it may be displaced
by an Age of Radio-Activity. To press that point, however, would be to
enter the field of prophecy, which is no part of my present purpose.
All that I have wished to point out is that for some thousands of
years after man learned to make implements of iron, the industrial
world and the human civilization that depends upon it, pursued a
relatively static course, like a broad, sluggish current, with no
new revolutionary discovery to impel it into new channels; and that
then one revolutionary discovery succeeded another with bewildering
suddenness, so that we of the early days of the twentieth century
are farther removed, in an industrial way, from our forerunners of
two hundred years ago, than those children of the eighteenth century
were from the earliest civilization that ever developed on our globe.
Indeed, this startling contrast would still hold true, were we to
consider the newest era as compassing only the period of a single
life. There are men living to-day who were born in that epoch when
the steam engine was for the first time used to turn the wheels of
factories. There are many men who can well remember the first practical
application of steam to railway traffic. Hosts of men can remember when
the first commercial message was transmitted by electricity along a
wire. Even middle-aged men recall the first cable message that linked
the old world with the new. And the application of the dynamo to the
purposes of the world's work is an affair of but yesterday.
The historian of the future, casting his eye back across the long
perspective of history, will find civilized man pursuing an even and
unbroken course across the ages from the time of the pyramids of Egypt
to about the time of the French Revolution. There will be no dearth
of incident to claim his attention in the way of wars and conquests,
and changing creeds, and the rise and fall of nations, each pursuing
virtually the same course of growth and decay as all the others. But
when he comes to the close of the eighteenth century, it will not be
the social paroxysm of a nation, or the meteoric career of a Napoleon
that will claim his attention so much as the introduction of that new
method of utilizing the powers of Nature which found its expression in
the mechanism called the steam engine.
If the name of any individual stands out as the great and memorable one
of that epoch of transition, at which the static current of previous
civilization changed suddenly to a Niagara-current of progress, it will
be the name of the great scientific inventor, rather than that of the
great military conqueror--the name of James Watt, rather than that of
Napoleon.
The military conqueror had his day of surpassing glory and departed,
to leave the world only a little worse than he found it. But the
mechanical inventor left a heritage that was to add day by day to the
wealth and happiness of humanity, supplying millions of artificial
hands, and making possible such beneficent improvements as no previous
age had dreamed of. Tasks that human hands had performed slowly,
laboriously, and inadequately, were now to be performed swiftly, with
ease, and well by the artificial hands provided with the aid of the new
power. Where carts drawn by horses had toiled slowly across the land,
and ships driven by the wind had drifted slowly through the waters,
massive trains of cars were to hurtle to the four corners of the earth
with inconceivable speed, and floating palaces were to course the
waters with almost equal defiance to the limitations of time and space.
And then there came that still weirder conquest of time and space,
wrought by the electric current. The moment when man first spoke with
man from continent to continent in defiance of the oceans, marked
the dawning of that larger day when all mankind shall constitute one
brotherhood and all peoples but a single nation. Within a half century
the sun of that new day has risen well above the horizon, and far
sooner than even the optimist of to-day dare predict with certainty, it
seems destined to reach its zenith.
But here again we verge upon the dangerous field of prophecy. Let
us turn from it and cast an eye back across the most wonderful of
centuries, contrasting the conditions of to-day in each of a half-dozen
fields of the world's work, with the conditions that obtained at the
close of the eighteenth century. Such a brief survey will show us
perhaps more vividly than we could otherwise be shown, how vast has
been the progress, how marvelous the development of civilization, in
the short decades that have elapsed since the coming of the Age of
Steam.
Let us pay heed first to the world of the agriculturist. Could we
turn back to the days of our grandparents, we should find farming a
very different employment from what it is to-day. For the most part
the farmer operated but a few small fields; if he had thirty or forty
acres of ploughed land, he found ample employment for his capacities.
He ploughed his fields with the aid of either a yoke of oxen or a
team of horses; he sowed his grain by hand; he cultivated his corn
with a hoe; he reaped his oats and wheat with a cradle--a device but
one step removed from a sickle; he threshed his grain with a flail;
he ground such portion of it as he needed for his own use with the
aid of water power at a neighboring mill; and such portion of it as
he sold was transported to market, be it far or near, in wagons that
compassed twenty or thirty miles a day at best. As regards live stock,
each farmer raised a few cattle, sheep, and hogs, and butchered them
to supply his own needs, selling the residue to a local dealer who
supplied the non-agricultural portion of the neighborhood. Any live
stock intended for a distant market was driven on foot across the
country to its destination. Each town and city, therefore, drew almost
exclusively for its supply from the immediately surrounding country.
To-day the small farmer has become almost obsolete, and the farms
of the eastern states that were the nation's chief source of supply
a century ago are largely allowed to lie fallow, it being no longer
possible to cultivate them profitably in competition with the rich
farm lands of the middle west. In that new home of agriculture, the
farm that does not comprise two or three hundred acres is considered
small; and large farms are those that number their acres by thousands.
The soil is turned by steam ploughs; the grain is sown with mechanical
seeders and planters; the corn is cultivated with a horse-drawn
machine, having blades that do the work of a dozen men; harvesters
drawn by three or four horses sweep over the fields and leave the grain
mechanically tied in bundles; the steam thresher places the grain in
sacks by hundreds of bushels a day; and this grain is hurried off in
steam cars to distant mills and yet more distant markets.
Meantime the raising of live stock has become a special department,
with which the farmer who deals in cereals often has no concern.
The cattle roam over vast pastures and are herded in the winter for
fattening in great droves, and protected from the cold in barns
that, when contrasted with the sheds of the old-time farmer, seem
almost palatial. When in marketable condition, cattle are no longer
slaughtered at the farm, but are transported in cars to one of the
few great centres, chief of which are the stock yards of Chicago and
of Kansas City. At these centres, slaughter houses and meat-packing
houses of stupendous magnitude have been developed, capable of
handling millions of animals in a year. From these centres the meat is
transported in refrigerator cars to the seaboards, and in refrigerator
ships to all parts of the world. Beef that grew on the ranges of the
far west may thus be offered for sale in the markets of New England
villages, at a price that prohibits local competition.
A more radical metamorphosis in agricultural conditions than all this
implies could not well be conceived. And when we recall once more that
the agricultural conditions that obtained at the beginning of the
nineteenth century were closely similar to those that obtained in each
successive age for a hundred preceding centuries, we shall gain a vivid
idea of the revolutionizing effects of new methods of work in the most
important of industries. It is little wonder that in this short time
the world has not solved to the satisfaction of the economists all the
new problems thus so suddenly developed.
Turn now to the manufacturing world. In the days of our
great-grandparents almost every household was a miniature factory where
cotton and wool were spun and the products were woven into cloth.
It was not till toward the close of the eighteenth century--just at
the time when Watt was perfecting the steam engine--that Arkwright
developed the spinning-frame, and his successors elaborated the
machinery that made possible the manufacture of cloth in wholesale
quantities; and the nineteenth century was well under way before
the household production of cloth had been entirely supplanted by
factory production. It is nothing less than pitiful to contemplate in
imagination our great-great-grandmothers--and all their forebears of
the long centuries--drudging away day after day, year in and year out,
at the ceaseless task of spinning and weaving--only to produce, as the
output of a lifetime of labor, a quantity of cloth equivalent perhaps
to what our perfected machine, driven by steam, and manipulated by
a factory girl, produces each working hour of every day. Similarly,
carpets and quilts were of home manufacture; so were coats and dresses;
and shoes were at most the product of the local shoemaker around the
corner.
In the kitchen, food was cooked over the coals of a great fireplace
or in the brick oven connected with that fireplace. Meat was supplied
from a neighboring farm; eggs were the product of the housewife's own
poultry yard; the son or daughter of the farmer milked the cow and
drove her to and from the pasture; the milk was "set" in pans in the
cellar--on a swinging shelf, preferably, to make it inaccessible to the
rats; and twice a week the cream was made into butter in a primitive
churn, the dasher of which was operated by the vigorous arm of the
housewife herself, or by the unwilling arms of some one of her numerous
progeny.
To give variety to the dietary, fruits grown in the local garden
or orchard were preserved, each in its season, by the industrious
housewife, and stored away in the capacious cellar; where also might be
found the supply of home-grown potatoes, turnips, carrots, parsnips,
and cabbages to provide for the needs of the winter. Fuel to supply
the household needs, both for cooking and heating, was cut in the
neighboring woodland, and carefully corded in the door-yard, where it
provided most uncongenial employment for the youth of the family after
school hours and of a Saturday afternoon.
The ashes produced when this wood was burned in the various fireplaces,
were not wasted, but were carefully deposited in barrels, from which
in due course lye was extracted by the simple process of pouring water
over the contents of the barrel. Meantime scraps of fat from the table
were collected throughout the winter and preserved with equal care; and
in due course on some leisure day in the springtime--heaven knows how a
leisure day was ever found in such a scheme of domestic economy!--the
lye drawn from the ash-barrels and the scraps of fat were put into a
gigantic kettle, underneath which a fire was kindled; with the result
that ultimately a supply of soft soap was provided the housewife, with
which her entire establishment, progeny included, could be kept in a
state of relative cleanness.
The reader of these pages has but to cast his eye about him in the
household in which he lives, and contrast the conditions just depicted
with those of his every-day life, to realize what change has come over
the aspects of household economy in the course of a short century.
Nor need he be told in each of the various departments of which the
activities are here outlined, that the changes which he observes have
been due to the application of machinery in all the essential lines of
work in question. We need not pause to detail the multitudinous devices
for the economy of household labor which owe their origin to the same
agency. There still remains, to be sure, enough of drudgery in the task
of the housewife; yet her most strenuous day seems a mere playtime in
comparison with the average day of her maternal forebear of three or
four generations ago.
But we must not here pause for further outlines of a subject which it
is the purpose of this and succeeding volumes to explicate in detail.
All our succeeding chapters will but make it more clear how marvelous
are the elaborations of method and of mechanism through which the
world's work of to-day is accomplished. We shall consider first the
mechanical principles that underlie work in general, passing on to
some of the principal methods of application through which the powers
of Nature are made available. We shall then take up in succession
the different fields of industry. We shall ask how the work of the
agriculturist is done in the modern world; how the multitudinous lines
of manufacture are carried out; how transportation is effected; we
shall examine the _modus operandi_ of the transmission of ideas; we
shall even consider that destructive form of labor which manifests
itself in the production of mechanisms of warfare. As we follow out the
stories of the all-essential industries we shall be led to realize more
fully perhaps than we have done before, the meaning of work in its
relations to human development; and in particular the meaning of modern
work, as carried out with the aid of modern mechanical contrivances, in
its relations to modern civilization.
The full force of these relations may best be permitted to unfold
itself as the story proceeds. There is, however, one fundamental
principle which I would ask the reader to bear constantly in mind, as
an aid to the full appreciation of the importance of our subject. It
is that in considering the output of the worker we have constantly to
do with one form or another of property, and that property is the very
foundation-stone of civilization. "It is impossible," says Morgan,
in his work on Ancient Society, "to overestimate the influence of
property in the civilization of mankind. It was the power that brought
the Aryan and Semitic nations out of barbarism into civilization.
The growth of the idea of property in the human mind commenced in
feebleness and ended in becoming its master passion. Governments and
laws are instituted with primary reference to its creation, protection,
and enjoyment. It introduced human slavery in its production; and,
after the experience of several thousand years, it caused the
abolition of slavery upon the discovery that the freeman was a better
property-making machine." If, then, we recall that without labor there
is no property, we shall be in an attitude of mind to appreciate the
importance of our subject; we shall realize, somewhat beyond the bounds
of its more tangible and sordid relations, the essential dignity, the
fundamental importance--in a word, the true meaning--of Work.
Undoubtedly there is a modern tendency to accept this view of the
dignity of physical labor. At any rate, we differ from the savage in
thinking it more fitting that man should toil than that his wife should
labor to support him--though it cannot be denied that even now the
number of physical toilers among women greatly exceeds the number of
such toilers among men. But in whatever measure we admit this attitude
of mind, there can be no question that it is exclusively a modern
attitude. Time out of mind, physical labor has been distasteful to
mankind, and it is a later development of philosophy that appreciates
the beneficence of the task so little relished.
The barbarian forces his wife to do most of the work, and glories in
his own freedom. Early civilization kept conquered foes in thraldom,
developing an hereditary body of slaves, whose function it was to do
the physical work.
The Hebrew explained the necessity for labor as a curse imposed upon
Father Adam and Mother Eve. Plato and Aristotle, voicing the spirit of
the Greeks, considered manual toil as degrading.
To-day we hear much of the dignity of labor; but if we would avoid cant
we must admit that now--scarcely less than in all the olden days--the
physical toiler is such because he cannot help himself. Few indeed are
the manual laborers who know any other means of getting their daily
bread than that which they employ. The most strenuous advocates of the
strenuous life are not themselves tillers of the soil or workers in
factories or machine shops.
The farm youth of intelligence does not remain a farmer; he goes to
the city, and we find him presently at the head of a railroad or a
bank, or practising law or medicine. The more intelligent laborer
becomes finally a foreman, and no longer handles the axe or sledge. We
should think it grotesque were we to see a man of intellectual power
obstinately following a pursuit that cost him habitual physical toil.
When now and then a Tolstoi offers an exception to this rule, we feel
that he is at least eccentric; and we may be excused the doubt whether
he would follow the manual task cheerfully if he did not know that he
could at any moment abandon it. It is because he knows that the world
understands him to be only a dilettante that he rejoices in his task.
After all, then, judged by the modern practice, rather than by the
philosopher's precept, the old Hebrew and Greek ideas were not so
far wrong. Using the poetical language which was so native to them,
it might be said that the necessity for physical labor is a curse--a
disgrace.
A partial explanation of this may be found in the fact that the most
uncongenial tasks are also the worst paid, while the congenial tasks
command the high emoluments. Generally speaking there is no distinction
between one laborer and another in the same field--except where the
eminently fair method of piece work can be employed. Even the skilled
laborer is usually paid by the day, and the amount he is to receive is
commonly fixed by a Union regardless of his efficiency as compared with
other laborers of the same class. And there is no possibility of his
receiving any such sums as the man who plans the work, but does nothing
with his own hands.
It has always been so. Just as "those who think must govern those that
toil," so the thinker must command the high reward. Partly this is
because man, considered as a mere toiler, is so relatively inefficient
a worker. When he strives to work with his hands, his effort is but a
pitiful one; he can by no possibility compete (as regards mere quantity
of labor) with the ox and the horse. He is impatient of his own puerile
efforts. It is only when he brings the products of ingenuity to his
aid that he is able to show his superiority, and to justify his own
egotism. So it is that in every age he has striven to find means of
adding to his feeble powers of body through the use of his relatively
gigantic powers of mind. And in proportion as he thus is able to "make
his head work for his hands" as the saying goes, he verges toward the
heights of civilization. To accomplish this more and more fully has
ever been the task of science as applied to the industries.
It will be our object in the ensuing chapters to inquire how far
science has accomplished the protean task thus set for it. We shall see
that much has been done; but that much still remains to be done. In
proportion as the problems are unsolved, science is reproached for its
shortcomings--and stimulated to new efforts.
In proportion as labor has been minimized and production increased--in
just that proportion has science justified itself; and in the same
proportion has the Conquest of Nature been carried toward completion.
II
HOW WORK IS DONE
The word energy implies capacity to do work. Work, considered in
the abstract, consists in the moving of particles of matter against
some opposing force, or in aid of previously acting forces. In the
last analysis, all energy manifests itself either as a push or as a
pull. But there is a modification of push and pull which is familiar
to everyone in practice under the name of prying. Illustrations may
be seen on every hand, as when a workman pries up a stone, or when
a housewife pries up a tack with the aid of a hammer. The principle
here involved is that of the lever--a principle which in its various
practical modifications is everywhere utilized in mechanics. Very
seldom indeed is the direct push or pull utilized; since the modified
push or pull, as represented by the lever in its various modifications
of pulley, ratchet-wheel, and the like, has long been known to meet the
needs of practical mechanics.
The very earliest primitive man who came to use any implement whatever,
though it were only a broken stick, must have discovered the essential
principle of the lever, though it is hardly necessary to add that he
did not know his discovery by any such high-sounding title. What he
did know, from practical experience, was that with the aid of a stick
he could pry up stones or logs that were much too heavy to be lifted
without this aid.
This practical knowledge no doubt sufficed for a vast number of
generations of men who used the lever habitually, without making
specific study of the relations between the force expended, the lengths
of the two ends of the lever, and the weight raised. Such specific
experiments were made, however, more than two thousand years ago by the
famous Syracusan, Archimedes. He discovered--or if some one else had
discovered it before him, he at least recorded and so gains the credit
of discovery--the specific laws of the lever, and he also pointed out
that levers, all acting on the same principle, may be different as to
their practical mechanism in three ways.
First, the fulcrum may lie between the power and the weight, as in the
case of the balance with which we were just experimenting. This is
called a lever of the first class, and familiar illustrations of it are
furnished by the poker, steelyard, or a pair of scissors. The so-called
extensor muscles of the body--those for example, that cause the arm to
extend--act on the bones in such a way as to make them levers of this
first class.
The second type of lever is that in which the weight lies between the
force and the fulcrum, as illustrated by the wheelbarrow, or by an
ordinary door.
In the third class of levers the power is applied between weight and
fulcrum, as illustrated by a pair of tongs, the treadle of a lathe,
or by the flexor muscles of the arm, operating upon the bones of the
forearm.
But in each case, let it be repeated, precisely the same principles are
involved, and the same simple law of the relations between positions
of power, weight, and fulcrum are maintained. The practical result
is always that a weight of indefinite size may be moved by a power
indefinitely long. If one arm of the lever is ten times as long as the
other, the power of one pound will lift or balance a ten-pound weight;
if the one arm is a thousand times as long as the other the power of
one pound will lift or balance a thousand pounds. If the long arm of
the lever could be made some millions of miles in length, the power
that a man could exert would balance the earth.
How fully Archimedes realized the possibilities of the lever is
illustrated in the classical remark attributed to him, that, had he
but a fulcrum on which to place his lever, he could move the world. As
otherwise quoted, the remark of Archimedes was that, had he a place
on which to stand, he could move the world, a remark which even more
than the other illustrates the full and acute appreciation of the
laws of motion; since, as we have already pointed out, action and
reaction being equal, the most infinitesimal push must be considered as
disturbing even the largest body.
Tremendous as is the pull of gravity by which the earth is held in
its orbit, yet the smallest push, steadily applied from the direction
of the sun, would suffice ultimately to disturb the stability of our
earth's motion, and to push it gradually through a spiral course
farther and farther away from its present line of elliptical flight.
Or if, on the other hand, the persistent force were applied from the
side opposite the sun, it would suffice ultimately to carry the earth
in a spiral course until it plunged into the sun itself. Indeed it has
been questioned in modern times whether it may not be possible that
precisely this latter effect is gradually being accomplished, through
the action of meteorites, some millions of which fall out of space into
the earth's atmosphere every day. If these meteorites were uniformly
distributed through space and flying in every direction, the fact that
the sun screens the earth from a certain number of them, would make
the average number falling on the side away from the sun greater, and
thus would in the course of ages produce the result just suggested. All
that could save our earth from such a fate would be the operation of
some counteracting force. Such a counteracting force is perhaps found
in solar radiation. It may be added that the distribution of meteorites
in space is probably too irregular to make their influence on the earth
predicable in the present state of science; but the principle involved
is no less sure.
WHEELS AND PULLEYS
Returning from such theoretical applications of the principle of
motion, to the practicalities of every-day mechanisms, we must note
some of the applications through which the principle of the lever is
made available. Of these some of the most familiar are wheels, and the
various modifications of wheels utilized in pulleys and in cogged
and bevelled gearings. A moment's reflection will make it clear that
the wheel is a lever of the first class, of which the axle constitutes
the fulcrum. The spokes of the wheel being of equal length, weights
and forces applied to opposite ends of any diameter are, of course,
in equilibrium. It follows that when a wheel is adjusted so that a
rope may be run about it, constituting a simple pulley, a mechanism is
developed which gives no gain in power, but only enables the operator
to change the direction of application of power. In other words, pound
weights at either end of a rope passed about a simple pulley are
in equilibrium and will balance each other, and move through equal
distances in opposite directions.
[Illustration: HORSE AND CATTLE POWER.
The large picture shows a model of a familiar mechanism for utilizing
horse power. The small picture shows a similar apparatus in actual
operation, actuated by cattle, in contemporary Brittany.]
If, however, two or more pulley wheels are connected, to make the
familiar apparatus of a compound pulley, we have accomplished by an
interesting mechanism a virtual application of the principle of the
long and short arm of the lever, and the relations between the weight
at the loose end of the rope and the weight attached to the block
which constitutes virtually the short end of the lever, may be varied
indefinitely, according to the number of pulley-wheels that are used.
A pound weight may be made to balance a thousand-pound weight; but,
of course, our familiar principle still holding, the pound weight
must move through a distance of a thousand feet in order to move
a thousand-pound weight through a distance of one foot. Familiar
illustrations of the application of this principle may be seen on every
hand; as when, for example, a piano or a safe is raised to the upper
window of a building by the efforts of men whose power, if directly
expended, would be altogether inefficient to stir the weight.
The pulley was doubtless invented at a much later stage of human
progress than the simple lever. It was, however, well known to the
ancients. It was probably brought to its highest state of practical
perfection by Archimedes, whose experiments are famous through the
narrative of Plutarch. It will be recalled that Archimedes amazed
the Syracusan general by constructing an apparatus that enabled
him, sitting on shore, to drag a ponderous galley from the water.
Plutarch does not describe in detail the apparatus with which this
was accomplished, but it is obvious from his description of what took
place, that it must have been a system of pulleys.
It will be observed that the pulley is a mechanism that enables the
user to transmit power to a distance. But this indeed is true in a
certain sense of every form of lever. Numberless other contrivances
are in use by which power is transmitted, through utilization of the
same principle of the lever, either through a short or through a
relatively long distance. A familiar illustration is the windlass,
which consists of a cylinder rotating on an axis propelled by a long
handle, a rope being wound about the cylinder. This is a lever of
the second class, the axis acting as fulcrum, and the rope operating
about the circumference of the cylinder typifying the weight, which
may be actually at a considerable distance, as in the case of the
old-fashioned well with its windlass and bucket, or of the simple form
of derrick sometimes called a sheerlegs.
OTHER MEANS OF TRANSMITTING POWER
Power is transmitted directly from one part of a machine to another,
in the case of a great variety of machines, with the aid of cogged
gearing wheels of various sizes. The modifications of detail in the
application of these wheels may be almost infinite, but the principle
involved is always the same. The case of two wheels toothed about
the circumference, the teeth of the two wheels fitting into one
another, illustrates the principle involved. A consideration of the
mechanism will show that here we have virtually a lever fixed at both
ends, represented by the radii of the two wheels, the power being
applied through the axle of one wheel, and the weight, for purposes
of calculation, being represented by the pressure of the teeth of one
wheel upon those of the other. So this becomes a lever of the second
class, and the relations of power between the two wheels are easily
calculated from the relative lengths of the radii. If, for example,
one radius is twice as long as the other, the transmission of power
will be, obviously, in the proportion of two to one, and meantime the
distance traversed by the circumference of one wheel will be twice as
great as that traversed by the other.
A modification of the toothed wheel is furnished by wheels which may be
separated by a considerable distance, and the circumferences of which
are connected by a belt or by a chain. The principle of action here
is precisely the same, the belt or chain serving merely as a means of
lengthening out our lever. The relative sizes of the wheels, and not
the length of the belt or chain, is the determining factor as regards
the relative forces required to make the wheels revolve.
It is obvious all along, of course, since action and reaction
are equal, that all of the relations in question are reciprocal.
When, for example, we speak of a pound weight on the long end of a
lever balancing a ten-pound weight on the short end, it is equally
appropriate to speak of the ten-pound weight as balancing the one-pound
weight. Similarly, when power is applied to the lever, it may be
applied at either end. Ordinarily, to be sure, the power is applied
at the long end, since the object is to lift the heavy weight; but in
complicated machinery it quite as often happens that these conditions
are reversed, and then it becomes desirable to apply strong power to
the short end of the lever, in order that the relatively small weight
may be carried through the long distance. In the inter-relations of
gearing wheels, such conditions very frequently obtain, practical ends
being met by a series of wheels of different sizes. But the single
rule, already so often outlined, everywhere holds--wherever there is
gain of power there is loss of distance, and we can gain distance only
by losing power. The words gain and loss in this application are in a
sense misnomers, since, as we have already seen, gain and loss are only
apparent, but their convenience of application is obvious.
A familiar case in which there is first loss of speed and gain of
power, and then gain of speed at the expense of power in the same
mechanism, is furnished by the bicycle, where (1) the crank shaft
turns the sprocket wheel that constitutes a lever of the second class
with gain of power; where (2) power is further augmented through
transmission from the relatively large sprocket wheel to the small
sprocket of the axle; and where (3) there is great loss of power and
corresponding gain of speed in transmitting the force from the small
sprocket wheel at the axle to the rubber rim of the bicycle proper,
this last transmission representing a lever of the third class. The net
gain of speed is tangibly represented by the difference in distance
traversed by the man's feet in revolving the pedals, and the actual
distance covered by the bicycle.
INCLINED PLANES AND DERRICKS
A less obvious application of the principle of reciprocal equivalence
of distance and weight is furnished by the inclined plane, a familiar
mechanism with the aid of which a great gain of power is possible. The
inclined plane, like the lever, has been known from remotest antiquity.
Its utility was probably discovered by almost the earliest builders.
Diodorus Siculus tells us that the great pyramids of Egypt were
constructed with the aid of inclined planes, based on a foundation of
earth piled about the pyramids. Diodorus, living at a period removed by
some thousands of years from the day of the building of the pyramids,
may or may not have voiced and recorded an authentic tradition, but we
may well believe that the principle of the inclined plane was largely
drawn upon by the mechanics of old Egypt, as by later peoples.
The law of the inclined plane is that in order to establish equilibrium
between two weights, the one must be to the other as the height of
the inclined plane is to its length. The steeper the inclined plane,
therefore, the less will be the gain in power; a mechanical principle
which familiar experience or the simplest experiment will readily
corroborate.
In its elemental form the inclined plane is not used very largely in
modern machinery, but its modified form of the wedge and the screw have
more utility. The screw, indeed, which is obviously an inclined plane
adjusted spirally about a cylinder or a cone, is familiar to everyone,
and is constantly utilized in applying power.
The crane or derrick furnishes a familiar but relatively elaborate
illustration of a mechanism for the transmission of power, in which
all the various devices hitherto referred to are combined, without the
introduction of any new principle.
Derricks have been employed from a very early day. The battering-rams
of the ancient Egyptians and Babylonians, for example, were virtually
derricks; and no doubt the same people used the device in raising
stones to build their temples and city walls, and in putting into
position such massive sculptures as the obelisks of Egypt and the
monster graven bulls and lions of Nineveh and Babylon.
[Illustration: CRANES AND DERRICKS.
The upper figure shows a floating derrick, the lower right-hand figure
a combined derrick and weighing machine, and the lower left-hand figure
a so-called sheerlegs, which is a simple derrick and windlass operated
by hand or by steam power with the aid of compound pulleys.]
The modern derrick, made of steel, and operated by steam or
electricity, capable of lifting tons, yet absolutely obedient to the
hand of the engineer, is a really wonderful piece of mechanism. A
steam-scoop, for example, excavating a gravel bank, seems almost
a thing of intelligence; as it gores into the bank scooping up
perhaps a half ton of earth, its upward sweeping head reminds one of
an angry bull. Then as it swings leisurely about and discharges its
load at just the right spot into an awaiting car, its hinged bottom
swings back and forth two or three times before closing, with curious
resemblance to the jaw of a dog; the similarity being heightened
by the square bull-dog-headed shape of the scoop itself. Yet this
remarkable contrivance, with all its massive steel beams and chains
and cog wheels, employs no other principles than the simple ones of
lever and pulley and inclined plane that we have just examined. The
power that must be applied to produce a given effect may be calculated
to a nicety. The capacities of the machine are fully predetermined
in advance of its actual construction. But of course this is equally
true of every other form of power-transmitter with which the modern
mechanical engineer has to deal.
FRICTION
In making such calculations, however, there is an additional element
which the engineer must consider, but which we have hitherto
disregarded. In all methods of transmission of power, and indeed in all
cases of the contact of one substance with another, there is an element
of loss through friction. This is due to the fact that no substance
is smooth except in a relative sense. Even the most highly polished
glass or steel, when viewed under the microscope, presents a surface
covered with indentations and rugosities. This granular surface of
even seemingly smooth objects, is easily visualized through the analogy
of numberless substances that are visibly rough. Yet the vast practical
importance of this roughness is seldom considered by the casual
observer. In point of fact, were it not for the roughened surface of
all materials with which we come in contact, it would be impossible for
any animal or man to walk, nor could we hold anything in our hands.
Anyone who has attempted to handle a fish, particularly an eel, fresh
from the water, will recall the difficulty with which its slippery
surface was held; but it may not occur to everyone who has had this
experience that all other objects would similarly slip from the hand,
had their surfaces a similar smoothness. The slippery character of the
eel is, of course, due in large part to the relatively smooth surface
of its skin, but partly also to the lubricant with which it is covered.
Any substance may be rendered somewhat smoother by proper lubrication;
it is necessary, however, that the lubricant should be something
which is not absorbed by the substance. Thus, wood is given increased
friction by being moistened with oil, but, on the other hand, is made
slippery if covered with graphite, soap, or any other fatty substances
that it does not absorb.
Recalling the more or less roughened surface of all objects, the source
of friction is readily understood. It depends upon the actual jutting
of the roughened surfaces, one upon the other. It virtually constitutes
a force acting in opposition to the motion of any two surfaces
upon each other. As between any different materials, under given
conditions, it varies with the pressure, in a definite and measurable
rate, which is spoken of as the coefficient of friction for the
particular substances. It is very much greater where the two substances
slide over one another than where the one rolls upon the other, as in
the case of the wheel. The latter illustrates what is called rolling
friction, and in practical mechanics it is used constantly to decrease
the loss--as, for example, in the wheels of wagons and cars. The use of
lubricants to decrease friction is equally familiar. Without them, as
everyone knows, it would be impossible to run any wheel continuously
upon an axle at high speed for more than a very brief period, owing
to the great heat developed through friction. Friction is indeed a
perpetual antagonist of the mechanician, and we shall see endless
illustrations of the methods he employs to minimize its influence. On
the other hand, we must recall that were it rendered absolutely _nil_,
his machinery would all be useless. The car wheel, for example, would
revolve indefinitely without stirring the train, were there absolutely
no friction between it and the rail.
AVAILABLE SOURCES OF ENERGY
We have pointed out that every body whatever contains a certain store
of energy, but it has equally been called to our attention that, in
the main, these stores of energy are not available for practical use.
There are, however, various great natural repositories of energy upon
which man is able to draw. The chief of these are, first, the muscular
energy of man himself and of animals; second, the energy of air in
motion; third, the energy of water in motion or at an elevation; and
fourth, the molecular and atomic energies stored in coal, wood, and
other combustible materials. To these we should probably add the energy
of radio-active substances--a form of energy only recently discovered
and not as yet available on a large scale, but which may sometime
become so, when new supplies of radio-active materials have been
discovered. It will be the object of succeeding chapters to point out
the practical ways in which these various stores of energy are drawn
upon and made to do work for man's benefit.
III
THE ANIMAL MACHINE
The muscular system is not only the oldest machine in existence,
but also the most complex. Moreover, it is otherwise entitled to
precedence, for even to-day, in this so-called age of steam and
electricity, the muscular system remains by far the most important of
all machines. In the United States alone there are some twenty million
horses doing work for man; and of course no machine of any sort is
ever put in motion or continues indefinitely in operation without
aid supplied by human muscles. All in all, then, it is impossible to
overestimate the importance of this muscular machine which is at once
the oldest and the most lasting of all systems of utilizing energy.
The physical laws that govern the animal machine are precisely similar
to those that are applied to other mechanisms. All the laws that have
been called to our attention must therefore be understood as applying
fully to the muscular mechanism. But in addition to these the muscular
system has certain laws or methods of action of its own, some of which
are not very clearly understood.
The prime mystery concerning the muscle is its wonderful property of
contracting. For practical purposes we may say that it has no other
property; the sole function of the muscle is to contract. It can, of
course, relax, also, to make ready for another contraction, but this
is the full extent of its activities. A microscopic examination of
the muscle shows that it is composed of minute fibres, each of which
on contraction swells up into a spindle shape. A mass of such fibres
aggregated together constitutes a muscle, and every muscle is attached
at either extremity, by means of a tendon, to a bone. Both extremities
of a muscle are never attached to the same bone--otherwise the muscle
would be absolutely useless. Usually there is only a single bone
between the two ends of a muscle, but in exceptional cases there may be
more. As a rule, the main body of a muscle lies along the bone to which
one end of it is attached, the other end of the muscle being attached
to the contiguous bone placed not far from the point. The first bone,
then, serves as a fulcrum on which the second bone moves as a lever,
and, as already pointed out, the familiar laws of the lever operate
here as fully as in the inanimate world. But a moment's reflection
will make it clear that the object effected by this mechanism is the
increase of motion with relative loss of energy. In other words, the
muscular force is applied to the short end of the lever, and a far
greater expenditure of force is required when the muscle contracts than
the power externally manifested would seem to indicate.
A moment's consideration of the mechanism of the arm, having regard to
the biceps muscle which flexes the elbow, will make this clear. If a
weight is held in the hand it is perhaps twelve inches from the elbow.
If, while holding the weight, you will grasp the elbow with the other
hand, you will feel the point of attachment of the biceps, and discover
that it does not seem to be, roughly speaking, more than about an inch
from the joint. Obviously, then, if you are lifting a pound weight, the
actual equivalent of energy expended by the contracting biceps must
be twelve pounds. But, in the meantime, when the pound weight in your
hand moves through the space of one inch, the muscle has contracted by
one-twelfth of an inch; and you may sweep the weight through a distance
of two feet by utilizing the two-inch contraction, which represents
about the capacity of the muscle.
A similar consideration of the muscles of the legs will show how the
muscular system which is susceptible of but trifling variation in size,
gives to the animal great locomotive power. With the aid of a series of
levers, represented by the bones of our thighs, legs, and feet, we are
able to stride along, covering three or four feet at each step, while
no set of the muscles that effect this propulsion varies in length by
more than two or three inches. It appears, then, that the muscular
system gives a marvelous illustration of capacity for storing energy in
a compact form and utilizing it for the development of motion.
THE TWO TYPES OF MUSCLES
The muscles of animals and men alike are divided into two systems,
one called voluntary, the other involuntary. The voluntary muscles,
as their name implies, are subject to the influence of the will,
and under ordinary conditions contract in response to the voluntary
nervous impulses. Certain sets of them, indeed, as those having to
do with respiration, have developed a tendency to rhythmical action
through long use, and ordinarily perform their functions without
voluntary guidance. Their function may, however, become voluntary
when attention is directed toward it, and is then subject to the
action of the will within certain bounds. Should a voluntary attempt
be made, however, to prevent their action indefinitely, the so-called
reflex mechanism presently asserts itself. All of which may be easily
attested by anyone who will attempt to stop breathing. All systems of
voluntary muscles are subject to the influence of habit, and may assume
activities that are only partially recognized by consciousness. As an
illustration in point, the muscles involved in walking come, in the
case of every adult, to perform their function without direct guidance
of the will. Such was not the case, however, in the early stage of
their development, as the observation of any child learning to walk
will amply demonstrate. In the case of animals, however, even those
muscles are so under the impress of hereditary tendencies as to perform
their functions spontaneously almost from the moment of birth. These,
however, are physiological details that need not concern us here. It
suffices to recall that the voluntary muscles may be directed by the
will, and indeed are always under what may be termed subconscious
direction, even when the conscious attention is not directed to them.
The strictly involuntary muscles, however, are placed absolutely beyond
control of the will. The most important of these muscles are those
that constitute the heart and the diaphragm, and that enter into the
substance of the walls of blood vessels, and of the abdominal organs.
It is obvious that the functioning of these important organs could not
advantageously be left to the direction of the will; and so, in the
long course of evolution they have learned, as it were, to take care
of themselves, and in so doing to take care of the organism, to the
life of which they are so absolutely essential. As the physiologist
views the matter, no organism could have developed which did not
correspondingly develop such involuntary action of the vital organs.
It will be seen that the involuntary muscles differ from the voluntary
muscles in that they are not connected with bones. Instead of being
thus attached to solid levers, they are annular in structure, and in
contracting virtually change the size of the ring which their substance
constitutes. Each fibre in contracting may be thought of as pulling
against other fibres, instead of against a bony surface, and the joint
action changes the size of the organ, as is obvious in the pulsing of
the heart.
Though the rhythmical contractions of the involuntary muscles are
independent of voluntary control, it must not be supposed that they
are independent of the control of the central nervous mechanism. On
the contrary, the nerve supply sent out from the brain to the heart
and to the abdominal organs is as plentiful and as important as that
sent to the voluntary muscles. There is a centre in the brain scarcely
larger than the head of a pin, the destruction of which will cause the
heart instantly to cease beating forever. From this centre, then, and
from the other centres of the brain, impulses are constantly sent to
the involuntary muscles, which determine the rate of activity. Nor are
these centres absolutely independent of the seat of consciousness, as
anyone will admit who recalls the varied changes in the heart's action
under stress of varying emotions.
That the voluntary muscles are controlled by the central nervous
mechanism needs no proof beyond the appeal to our personal experiences
of every moment. You desire some object that lies on the table in front
of you, and immediately your hand, thanks to the elaborate muscular
mechanism, reaches out and grasps it. And this act is but typical of
the thousand activities that make up our every-day life. Everyone is
aware that the channel of communication between the brain and the
muscular system is found in a system of nerves, which it is natural
now-a-days to liken to a system of telegraph wires. We speak of the
impulse generated in the brain as being transmitted along the nerves to
the muscle, causing that to contract. We are even able to measure the
speed of transfer of such an impulse. It is found to move with relative
slowness, compassing only about one hundred and twelve feet per second,
being in this regard very unlike the electric current with which it is
so often compared. But the precise nature of this impulse is unknown.
Its effect, however, is made tangible in the muscular contraction
which it is its sole purpose to produce. The essential influence of
the nerve impulse in the transaction is easily demonstrable; for if
the nerve cord is severed, as often happens in accidents, the muscle
supplied by that nerve immediately loses its power of voluntary
contraction. It becomes paralyzed, as the saying is.
THE NATURE OF MUSCULAR ACTION
Paying heed, now, to the muscle itself, it must be freely admitted
that, in the last analysis, the activities of the substance are as
mysterious and as inexplicable as are those involved in the nervous
mechanism. It is easy to demonstrate that what we have just spoken
of as a muscle fibre consists in reality of a little tube of liquid
protoplasm, and that the change in shape of this protoplasm constitutes
the contraction of which we are all along speaking. But just what
molecular and atomic changes are involved in this change of form of the
protoplasm, we cannot say. We know that the power to contract is the
one universal attribute of living protoplasm. This power is equally
wonderful and equally inexplicable, whether manifested in the case
of the muscle cell or in the case of such a formless single-celled
creature as the amoeba. When we know more of molecular and atomic
force, we may perhaps be able to form a mental picture of what goes on
in the structure of protoplasm when it thus changes the shape of its
mass. Until then, we must be content to accept the fact as being the
vital one upon which all the movements of animate creatures depend.
But if, here as elsewhere, the ultimate activities of molecules and
atoms lie beyond our ken, we may nevertheless gain an insight into
the nature of the substances involved. We know, for example, that the
chief constituents of all protoplasm are carbon, hydrogen, oxygen, and
nitrogen; and that with these main elements there are traces of various
other elements such as iron, sulphur, phosphorus, and sundry salts.
We know that when the muscle contracts some of these constituents
are disarranged through what is spoken of as chemical decomposition,
and that there results a change in the substance of the protoplasm,
accompanied by the excretion of a certain portion of its constituents,
and by the liberation of heat. Carbonic acid gas, for example, is
generated and is swept away from the muscular tissues in the ever
active bloodstreams, to be carried to the lungs and there expelled--it
being a noxious poison, fatal to life if retained in large quantities.
Equally noxious are other substances such as uric acid and its
compounds, which are also results of the breaking down of tissue that
attends muscular action. In a word, there is an incessant formation of
waste products, due to muscular activity, the removal of which requires
the constant service of the purifying streams of blood and of the
various excretory organs.
But this constant outflow of waste products from the muscle
necessitates, of course, in accordance with the laws of the
conservation of matter and of energy, an equally constant supply
of new matter to take the place of the old. This supply of what is
virtually fuel to be consumed, enabling the muscle to perform its
work, is brought to the muscle through the streams of blood which flow
from the heart in the arterial channels, and in part also through the
lymphatic system. The blood itself gains its supply from the digestive
system and from the lungs. The digestive system supplies water, that
all-essential diluent, and a great variety of compounds elaborated into
the proper pabulum; while the vital function of the lungs is to supply
oxygen, which must be incessantly present in order that the combustion
which attends muscular activity may take place. What virtually happens
is that fuel is sent from the digestive system to be burned in the
muscular system, with the aid of oxygen brought from the lungs.
In this view, the muscular apparatus is a species of heat engine. In
point of fact, it is a curiously delicate one as regards the range of
conditions within which it is able to act. The temperature of any given
organism is almost invariable; the human body, for example, maintains
an average temperature of 98-2/5 degrees, Fahrenheit. The range of
variation from this temperature in conditions of health is rarely
more than a fraction of a degree; and even under stress of the most
severe fever the temperature never rises more than about eight degrees
without a fatal result. That an organism which is producing heat in
such varying quantities through its varying muscular activities should
maintain such an equilibrium of temperature, would seem one of the most
marvelous of facts, were it not so familiar.
The physical means by which the heat thus generated is rapidly given
off, on occasion, to meet the varying conditions of muscular activity,
is largely dependent upon the control of the blood supply, in which
involuntary muscles, similar to those of the heart, are concerned.
In times of great muscular activity, when the production of heat is
relatively enormous, the arterioles that supply the surface of the
body are rapidly dilated so that a preponderance of blood circulates
at the surface of the body, where it may readily radiate its heat into
space; the vast system of perspiratory ducts, with which the skin is
everywhere supplied, aiding enormously in facilitating this result,
through the secretion of a film of perspiration, which in evaporating
takes up large quantities of heat.
The flushed, perspiring face of a person who has violently exercised
gives a familiar proof of these physiological changes; and the contrary
condition, in which the peripheral circulation is restricted, and in
which the pores are closed, is equally familiar. Moreover, the same
cutaneous mechanism is efficient in affording the organism protection
from the changes of external temperature; though the human machine,
thanks to the pampering influence of civilization, requires additional
protection in the form of clothing.
APPLICATIONS OF MUSCULAR ENERGY
Having thus outlined the conditions under which the muscular machine
performs its work, we have now to consider briefly the external
mechanisms with the aid of which muscular energy is utilized.
Of course, the simplest application of this power, and the one
universally employed in the animal world is that in which a direct
push or pull is given to the substance, the position of which it
is desired to change. We have already pointed out that there is no
essential difference between pushing and pulling. The fact receives
another illustration in considering the muscular mechanism. We speak
of pushing when we propel something away from a body, of pulling when
we draw something toward it, yet, as we have just seen, each can be
accomplished merely through the contraction of a set of muscles, acting
on differently disposed levers. All the bodily activities are reducible
to such muscular contractions, and the diversified movements in which
the organism constantly indulges are merely due to the large number and
elaborate arrangement of the bony levers upon which these muscles are
operated.
We may well suppose that the primitive man continued for a long
period of time to perform all such labors as he undertook without
the aid of any artificial mechanism; that is to say, without having
learned to gain any power beyond that which the natural levers
of his body provided. A brief observation of the actions of a
man performing any piece of manual labor will, however, quickly
demonstrate how ingeniously the bodily levers are employed, and how
by shifting positions the worker unconsciously makes the most of a
given expenditure of energy. By bending the arms and bringing them
close to the body, he is able to shorten his levers so that he can
lift a much greater weight than he could possibly raise with the arms
extended. On the other hand, with the extended arm he can strike a
much more powerful blow than with the shorter lever of the flexed
arm. But however ingenious the manipulation of the natural levers, a
full utilization of muscular energy is possible only when they are
supplemented with artificial aids, which constitute primitive pieces of
machinery.
These aids are chiefly of three types, namely, inclined planes,
friction reducers, and levers. The use of the inclined plane was very
early discovered and put into practise in chipped implements, which
took the form of the wedge, in such modifications as axes, knives, and
spears of metal. All of these implements, it will be observed, consist
essentially of inclined planes, adapted for piercing relatively soft
tissues of wood or flesh, and hence serving purposes of the greatest
practical utility.
The knife-blade is an extremely thin wedge, to be utilized by force of
pushing, without any great aid from acquired momentum. The hatchet, on
the other hand--and its modification the axe--has its blunter blade
fastened to a handle; that the principle of the wedge may be utilized
at the long end of a lever and with the momentum of a swinging blow.
Ages before anyone could have explained the principle involved in such
obscuring terms as that, the implement itself was in use for the same
purpose to which it is still applied. Indeed, there is probably no
other implement that has played a larger part in the history of human
industry. Even in the Rough Stone Age it was in full favor, and the
earliest metallurgists produced it in bronze and then in iron. The
blade of to-day is made of the best tempered steel, and the handle
or helve of hickory is given a slight curve that is an improvement on
the straight handle formerly employed; but on the whole it may be said
that the axe is a surviving primitive implement that has held its own
and demonstrated its utility in every generation since the dawn, not of
history only, but of barbarism, perhaps even of savagery.
The saw, consisting essentially of a thin elongated blade, one ragged
or toothed edge, is a scarcely less primitive and an equally useful and
familiar application of the principle of the inclined plane--though it
requires a moment's reflection to see the manner of application. Each
tooth, however minute, is an inclined plane, calculated to slide over
the tissue of wood or stone or iron even, yet to tear at the tissue
with its point, and, with the power of numbers, ultimately wear it away.
THE WHEEL AND AXLE
The primitive friction reducer, which continues in use to the present
day unmodified in principle, is the wheel revolving on an axle.
Doubtless man had reached a very high state of barbarism before he
invented such a wheel. The American Indian, for example, knew no
better method than to carry his heavy burdens on his shoulders, or
drag them along the ground, with at most a pair of parallel poles or
runners to modify the friction; every move representing a very wasteful
expenditure of energy. But the pre-historic man of the old world had
made the wonderful discovery that a wheel revolving on an axle vastly
reduces the friction between a weight and the earth, and thus enables
a man or a woman to convey a load that would be far beyond his or her
unaided powers. It is well to use both genders in this illustration,
since among primitive peoples it is usually the woman who is the bearer
of burdens. And indeed to this day one may see the women of Italy and
Germany bearing large burdens on their backs and heads, and dragging
carts about the streets, quite after the primitive method.
The more one considers the mechanism, the more one must marvel at the
ingenuity of the pre-historic man who invented the wheel and axle. Its
utility is sufficiently obvious once the thing has been done. In point
of fact, it so enormously reduces the friction that a man may convey
ten times the burden with its aid that he can without it. But how was
the primitive man, with his small knowledge of mechanics, to predict
such a result? In point of fact, of course, he made no such prediction.
Doubtless his attention was first called to the utility of rolling
bodies by a chance observation of dragging a burden along a pebbly
beach, or over rolling stones. The observation of logs or round stones
rolling down a hill might also have stimulated the imagination of some
inventive genius.
[Illustration: A BELGIAN MILK-WAGON.
In many of the countries of Europe the dog plays an important part as
a beast of burden. Stringent laws are enforced in these countries to
prevent possible abuse or neglect of the animals.]
Probably logs placed beneath heavy weights, such as are still employed
sometimes in moving houses, were utilized now and again for many
generations before the idea of a narrow section of a log adjusted on
an axis was evolved. But be that as it may, this idea was put into
practise before the historic period begins, and we find the earliest
civilized races of which we have record--those, namely, of Old Egypt
and of Old Babylonia--in full possession of the principle of the wheel
as applied to vehicles. Modern mechanics have, of course, improved the
mechanism as regards details, but the wheels depicted in Old Egyptian
and Babylonian inscriptions are curiously similar to the most modern
types. Indeed, the wheel is a striking illustration of a mechanism
which continued century after century to serve the purposes of the
practical worker, with seemingly no prospect of displacement.
MODIFIED LEVERS
For the rest, the mechanisms which primitive man learned early to
use in adding to his working efficiency, and which are still used by
the hand laborer, are virtually all modifications of our familiar
type-implement, the lever. A moment's reflection will show that the
diversified purposes of the crowbar, hoe, shovel, hammer, drill,
chisel, are all accomplished with the aid of the same principles.
The crowbar, for example, enables man to regain the power which he
lost when his members were adapted to locomotion. His hands, left
to themselves, as we have already pointed out, give but inadequate
expression to the power of his muscles. But by grasping the long end of
such a lever as the crowbar, he is enabled to utilize his entire weight
in addition to his muscular strength, and, with the aid of this lever,
to lift many times his weight.
The hoe, on the other hand, becomes virtually a lengthened arm,
enabling a very slight muscular motion to be transformed into the
long sweep of the implement, so that with small expenditure of energy
the desired work is accomplished. Similarly, the sledge and the axe
lengthen out the lever of the arms, so that great momentum is readily
acquired, and with the aid of inertia a relatively enormous force can
be applied. It will be observed that a laborer in raising a heavy
sledge brings the head of the implement near his body, thus shortening
the leverage and gaining power at the expense of speed; but extends his
arms to their full length as the sledge falls, having now the aid of
gravitation, to gain the full advantage of the long arm of the lever in
acquiring momentum.
Even such elaborately modified implements as the treadmill and the
rowboat are operated on the principle of the lever. These also are
mechanisms that have come down to us from a high antiquity. Their
utility, however, has been greatly decreased in modern times, by
the substitution of more elaborate and economical mechanisms for
accomplishing their respective purposes. The treadmill, indeed--which
might be likened to an overshot waterwheel in which the human foot
supplied the place of the falling water in giving power--has become
obsolete, though a modification of it, to be driven by animal power, is
still sometimes used, as we shall see in a moment.
All these are illustrations of mechanisms with the aid of which human
labor is made effective. They show the devices by which primitive man
used his ingenuity in making his muscular system a more effective
machine for the performance of work. But perhaps the most ingenious
feat of all which our primitive ancestor accomplished was in learning
to utilize the muscular energy of other animals. Of course the example
was always before him in the observed activity of the animals on every
side. Nevertheless, it was doubtless long before the idea suggested
itself, and probably longer still before it was put into practise, of
utilizing this almost inexhaustible natural supply of working energy.
DOMESTICATED ANIMALS
The first animal domesticated is believed to have been the dog, and
this animal is still used, as everyone knows, as a beast of burden in
the far North, and in some European cities, particularly in those of
Germany. Subsequently the ox was domesticated, but it is probable that
for a vast period of time it was used for food purposes, rather than as
a beast of burden. And lastly the horse, the worker _par excellence_,
was made captive by some Asiatic tribes having the genius of invention,
and in due course this fleetest of carriers and most efficient of
draught animals was introduced into all civilized nations.
Doubtless for a long time the energy of the horse was utilized in an
uneconomical way, through binding the burden on its back, or causing it
to drag the burden along the ground. But this is inferential, since,
as we have seen, the wheel was invented in pre-historic times, and at
the dawn of history we find the Babylonians driving harnessed horses
attached to wheeled vehicles. From that day to this the method of
using horse-power has not greatly changed. The vast majority of the
many millions of horses that are employed every day in helping on the
world's work, use their strength without gain or loss through leverage,
and with only the aid of rolling friction to increase their capacity as
beasts of burden.
To a certain extent horse-power is still used with the aid of the
modified treadmill just referred to--consisting essentially of an
inclined plane of flexible mechanism made into an endless platform,
which the horse causes to revolve as he goes through the movements of
walking upon it. In agricultural districts this form of power is still
sometimes used to run threshing machines, cider mills, wood-saws,
and the like. Another application of horse-power to the same ends
is accomplished through harnessing a horse to a long lever like the
spoke of a wheel, fastened to an axis, which is made to revolve as the
horse walks about it. Several horses are sometimes hitched to such
a mechanism, which becomes then a wheel of several spokes. But this
mechanism, which was common enough in agricultural districts two or
three decades ago, has been practically superseded in recent years by
the perambulatory steam engine.
[Illustration: TWO APPARATUSES FOR THE UTILIZATION OF ANIMAL POWER.
The upper figure shows the type of portable horse-power machine used
for threshing grain in 1851. The lower figure is an inclined-plane
horse-gear. The horse stands on the sloping platform tied to the bar in
front, so that it is compelled to walk as the platform recedes.]
It is obvious that the amount of work which a horse can accomplish
must vary greatly with the size and quality of the horse, and with the
particular method by which its energy is applied. For the purposes
of comparison, however, an arbitrary amount of work has been fixed
upon as constituting what is called a horse-power. This amount is the
equivalent of raising thirty-three thousand pounds of weight to the
height of one foot in one minute. It would be hard to say just why this
particular standard was fixed upon, since it certainly represents more
than the average capacity of a horse. It is, however, a standard which
long usage (it was first suggested by Watt, of steam-engine fame) has
rendered convenient, and one which the machinist refers to constantly
in speaking of the efficiency of the various types of artificial
machines. All questions of the exact legitimacy of this particular
standard aside, it was highly appropriate that the labor of the horse,
which has made up so large a share of the labor of the past, and which
is still so extensively utilized, should continue to be taken as the
measuring standard of the world's work.
IV
THE WORK OF AIR AND WATER
The store of energy contained in the atmosphere and in the waters of
the globe is inexhaustible. Its amount is beyond all calculation; or if
it were vaguely calculated the figures would be quite incomprehensible
from their very magnitude. It is not, however, an altogether simple
matter to make this energy available for the purposes of useful work.
We find that throughout antiquity comparatively little use was made of
either wind or water in their application to machinery.
Doubtless the earliest use of air as a motive power was through the
application of sails to boats. We know that the Phoenicians used a
simple form of sail, and no doubt their example was followed by all the
maritime peoples of subsequent periods. But the use of the sail even by
the Phoenicians was as a comparatively unimportant accessory to the
galaxies of oars, which formed the chief motive power. The elaboration
of sails of various types, adequate in extent to propel large ships,
and capable of being adjusted so as to take advantage of winds blowing
from almost any quarter, was a development of the Middle Ages.
The possibilities of work with the aid of running water were also but
little understood by the ancients. In the days of slave labor it was
scarcely worth while to tax man's ingenuity to invent machines, since
so efficient a one was provided by nature. Yet the properties of both
air and water were studied by various mechanical philosophers, at the
head of whom were Archimedes, whose work has already been referred to,
and the famous Alexandrian, Ctesibius, whose investigations became
familiar through the publications of his pupil, Hero.
Perhaps the most remarkable device invented by Ctesibius was a
fire-engine, consisting of an arrangement of valves constituting a
pump, and operating on the principle which is still in vogue. It is
known, however, that the Egyptians of a much earlier period used
buckets having valves in their bottoms, and these perhaps furnished the
foundation for the idea of Ctesibius. It is unnecessary to give details
of this fire-engine. It may be noted, however, that the principle of
the lever is the one employed in its operation to gain power. A valve
consists essentially of any simple hinged substance, arranged so that
it may rise or fall, alternately opening and closing an aperture.
A mere flap of leather, nailed on one edge, serves as a tolerably
effective valve. At least one of the valves used by Ctesibius was a
hinged piece of smooth metal. A piston fitted in a cylinder supplies
suction when the lever is raised, and pressure when it is compressed,
alternately opening the valve and closing the valve through which the
water enters the tube. Meantime a second valve alternating with the
first permits the water to enter the chamber containing air, which
through its elasticity and pressure equalizes the force of the stream
that is ejected from the chamber through the hose.
SUCTION AND PRESSURE
In the construction of this and various other apparatus, Ctesibius and
Hero were led to make careful studies of the phenomena of suction. But
in this they were not alone, since numerous of their predecessors had
studied the subject, and such an apparatus as the surgeon's cupping
glass was familiarly known several centuries before the Christian era.
The cupping glass, as perhaps should be explained to the reader of the
present day--since the apparatus went out of vogue in ordinary medical
practise two or three generations ago--consists of a glass cup in which
the air is exhausted, so as to suck blood from any part of the surface
of a body to which it is applied. Hero describes a method of exhausting
air by which such suction may be facilitated. But neither he nor any
other philosopher of his period at all understood the real nature of
this suction, notwithstanding their perfect familiarity with numerous
of its phenomena. It was known, for example, that when a tube closed
at one end is filled with water and inverted with the open end beneath
the surface of the water, the water remains in the tube, although one
might naturally expect that it would obey the impulses of gravitation
and run out, leaving the tube empty. A familiar explanation of this and
allied phenomena throughout antiquity was found in the saying that
"Nature abhors a vacuum." This explanation, which of course amounts
to no explanation at all, is fairly illustrative of the method of
metaphysical word-juggling that served so largely among the earlier
philosophers in explanation of the mysteries of physical science.
The real explanation of the phenomena of suction was not arrived
at until the revival of learning in the seventeenth century. Then
Torricelli, the pupil of Galileo, demonstrated that the word suction,
as commonly applied, had no proper application; and that the phenomena
hitherto ascribed to it were really due to the pressure of the
atmosphere. A vacuum is merely an enclosed space deprived of air, and
the "abhorrence" that Nature shows to such a space is due to the fact
that air has weight and presses in every direction, and hence tends
to invade every space to which it can gain access. It was presently
discovered that if the inverted tube in which the water stands was
made high enough, the water will no longer fill it, but will sink to a
certain level. The height at which it will stand is about thirty feet;
above that height a vacuum will be formed, which, for some reason,
Nature seems not to abhor. The reason is that the weight of any given
column of water about thirty feet in height is just balanced by the
weight of a corresponding column of atmosphere. The experiments that
gave the proof of this were made by the famous Englishman, Boyle. He
showed that if the heavy liquid, mercury, is used in place of water,
then the suspended column will be only about thirty inches in height.
The weight or pressure of the atmosphere at sea level, as measured by
these experiments, is about fifteen pounds to the square inch.
Boyle's further experiments with the air and with other gases developed
the fact that the pressure exerted by any given quantity of gas is
proportional to the external pressure to which it is subjected, which,
after all, is only a special application of the law that action and
reaction are equal. The further fact was developed that under pressure
a gas decreases at a fixed rate in bulk. A general law, expressing
these facts in the phrase that density and elasticity vary inversely
with the pressure in a precise ratio, was developed by Boyle and the
Frenchman, Mariotte, independently, and bears the name of both of its
discoverers. No immediate application of the law to the practical
purposes of the worker was made, however, and it is only in recent
years that compressed air has been extensively employed as a motive
power. Even now it has not proved a great commercial success, because
other more economical methods of power production are available. In
particular cases, however, it has a certain utility, as a relatively
large available source of energy may be condensed into a very small
receptacle.
A very striking experiment illustrating the pressure of the air was
made by a famous contemporary of Boyle and Mariotte, by the name of
Otto von Guericke. He connected an air pump with a large brass sphere,
composed of two hemispheres, the edges of which fitted smoothly, but
were not connected by any mechanism. Under ordinary conditions the
hemispheres would fall apart readily, but von Guericke proved, by
a famous public demonstration, that when the air was exhausted in
the sphere, teams of horses pulling in opposite directions on the
hemispheres could not separate them. This is famous as the experiment
of the Magdeburg spheres, and it is often repeated on a smaller scale
in the modern physical laboratory, to the astonishment of the tyro in
physical experiments.
The first question that usually comes to the mind of anyone who has
personally witnessed such an experiment, is the question as to how
the human body can withstand the tremendous force to which it is
subjected by an atmosphere exerting a pressure of fifteen pounds on
every square inch of its surface. The explanation is found in the
uniform distribution of the pressure, the influence of which is thus
counteracted, and by the fact that the tissues themselves contain
everywhere a certain amount of air at the same pressure. The familiar
experiment of holding the hand over an exhausted glass cylinder--which
experiment is indeed but a modification of the use of the cupping
glass above referred to--illustrates very forcibly the insupportable
difficulties which the human body would encounter were not its entire
surface uniformly subjected to the atmospheric pressure.
AIR IN MOTION
At about the time when the scientific experiments with the pressure of
gases were being made, practical studies of the effects of masses of
air in motion were undertaken by the Dutch philosopher, Servinus. The
use of the windmill in Holland as a means of generating power doubtless
suggested to Servinus the possibility of attaching a sail to a land
vehicle. He made the experiment, and in the year 1600 constructed a
sailing car which, propelled by the wind, traversed the land to a
considerable distance, on one occasion conveying a company of which
Prince Maurice of Orange was a member. But his experiments have seldom
been repeated, and indeed their lack of practical feasibility scarcely
needs demonstration.
The utility of the wind, however, in generating the power in a
stationary mechanism is familiar to everyone. Windmills were
constructed at a comparatively early period, and notwithstanding all
the recent progress in the development of steam and electrical power,
this relatively primitive so-called prime mover still holds its own in
agricultural districts, particularly in its application to pumps. A
windmill consists of a series of inclined planes, each of which forms
one of the radii of a circle, or spokes of a wheel, to the axle of
which a gearing is adjusted by which the power generated is utilized.
The wheel is made to face the wind by the wind itself blowing against a
sort of rudder which projects from the axis. The wind blowing against
the inclined surfaces or vanes of the wheel causes each vane to move in
accordance with the law of component forces, thus revolving the wheel
as a whole.
[Illustration: WINDMILLS OF ANCIENT AND MODERN TYPES.
The smaller figures show Dutch windmills of the present day, many of
which are identical in structure with the windmills of the middle ages.
It will be seen that the sails can be furled when desired to put the
mill out of operation. In the mill of modern type (large figure) the
same effect is produced by slanting the slats of the wheel.]
It has been affirmed that the Romans had windmills, but "the silence of
Vitruvius, Seneca, and Chrysostom, who have spoken of the advantages of
the wind, makes this opinion questionable." It has been supposed by
other writers that windmills were used in France in the sixth century,
while still others have maintained that this mechanism was unknown in
Europe until the time of the Crusades. All that is tolerably certain
is that in the twelfth century windmills were in use in France and
England. It is recorded that when they began to be somewhat common
Pope Celestine III. determined that the tithes of them belonged to the
clergy.
INHERENT DEFECTS OF THE WINDMILL
The mediæval European windmill was supplied with great sails of cloth,
and its picturesque appearance has been made familiar to everyone
through the famous tale of _Don Quixote_. The modern windmill, acting
on precisely the same principle, is a comparatively small affair,
comprising many vanes of metal, and constituting a far more practical
machine. The great defect of all windmills, however, is found in the
fact that of necessity they furnish such variable power, since the
force of the wind is incessantly changing. Worst of all, there may be
protracted periods of atmospheric calm, during which, of course, the
windmill ceases to have any utility whatever. This ineradicable defect
relegates the windmill to a subordinate place among prime movers, yet
on the other hand, its cheapness insures its employment for a long time
to come, and the industry of manufacturing windmills continues to be an
important one, particularly in the United States.
RUNNING WATER
The aggregate amount of work accomplished with the aid of the wind is
but trifling, compared with that which is accomplished with the aid of
water. The supply of water is practically inexhaustible, and this fluid
being much more manageable than air, can be made a far more dependable
aid to the worker. Every stream, whatever its rate of flow, represents
an enormous store of potential energy. A cubic foot of water weighs
about sixty-two and a half pounds. The working capacity of any mass
of water is represented by one-half its weight into the square of its
velocity; or, stated otherwise, by its weight into the distance of its
fall. Now, since the interiors of the continents, where rivers find
their sources, are often elevated by some hundreds or even thousands
of feet, it follows that the working energy expended--and for the most
part wasted--by the aggregate water current of the world is beyond all
calculation. Meantime, however, a portion of the energy which in the
aggregate represents an enormous working power is utilized with the aid
of various types of water wheels.
Watermills appear to have been introduced in the time of Mithridates,
Julius Cæsar, and Cicero. Strabo informs us that there was a watermill
near the residence of Mithridates; and we learn from Pomponius Sabinus,
that the first mill seen at Rome was erected on the Tiber, a little
before the time of Augustus. That they existed in the time of Augustus
is obvious from the description given of them by Vitruvius, and the
epigram of Antipater, who is supposed to have lived in the time of
Cicero. But though mills driven by water were introduced at this early
period, yet public mills did not appear till the time of Honorius and
Arcadius. They were erected on three canals, which conveyed water to
the city, and the greater number of them lay under Mount Janiculum.
When the Goths besieged Rome in 536, and stopped the large aqueduct and
consequently the mills, Belisarius appears to have constructed, for the
first time, floating mills upon the Tiber. Mills driven by the tide
existed at Venice in the year 1046, or at least in 1078.
The older types of water wheel are exceedingly simple in construction,
consisting merely of vertical wheels revolving on horizontal axes,
and so placed as to receive the weight or pressure of the water on
paddles or buckets at their circumference. The water might be allowed
to rush under the wheel, thus constituting an under-shot wheel; or
more commonly it flows from above, constituting an over-shot wheel.
Where the natural fall is not available, dams are employed to supply an
artificial fall.
This primitive type of water wheel has been practically abandoned
within the last generation, its place having been taken by the much
more efficient type of wheel known as the turbine. This consists of
a wheel, usually adjusted on a vertical axis, and acting on what is
virtually the principle of a windmill. To gain a mental picture of the
turbine in its simplest form, one might imagine the propelling screw
of a steamship, placed horizontally in a tube, so that the water could
rush against its blades. The tiny windmills which children often make
by twisting pieces of paper illustrate the same principle. Of course,
in its developed form the turbine is somewhat elaborated, in the aim to
utilize as large a proportion of the energy of the falling water as is
possible; but the principle remains the same.
The turbine wheel was invented by a Frenchman named Fourneyron, about
three-quarters of a century ago (1827), but its great popularity, in
America in particular, is a matter of the last twenty or thirty years.
To-day it has virtually supplanted every other type of water wheel.
To use any other is indeed a wasteful extravagance, as the perfected
turbine makes available more than eighty per cent. of the kinetic
energy of any mass of falling water. A turbine wheel two feet in
diameter is able to do the work of an enormous wheel of the old type.
Turbine wheels are of several types, one operating in a closed tube to
which air has no access, and another in an open space in the presence
of air. The water may also be made to enter the turbine at the side
or from below, thus serving to support the weight of the mechanism--a
consideration of great importance in the case of such gigantic turbines
as those that are employed at Niagara Falls, which we shall have
occasion to examine in detail in a later chapter.
[Illustration: WATER WHEELS.
Fig. 1 shows a model of the so-called breast wheel, a familiar type of
water wheel that has been in use since the time of the Romans. Figs.
2 and 3 show similar wheels as used to-day in Belgium. Fig. 4 shows a
model of Fourneyron's turbine. This wheel was made in 1837, but the
original turbine was introduced by Fourneyron in 1827. The turbine
wheel has now almost supplanted the other forms of water wheel except
in rural districts.]
The power generated by a revolution of the turbine wheel may, of
course, be utilized directly by belts or gearings attached to its
axle, or it may be transferred to a distance, with the aid of a
dynamo generating electricity. The latter possibility, which has only
recently been developed, and which we shall have occasion to examine
in detail in connection with our studies of the power at Niagara, gives
a new field of usefulness to the turbine wheel, and makes it probable
that this form of power will be vastly more used in the future than
it has been in the past. Indeed, it would not be surprising were it
ultimately to become the prime source of working energy as utilized in
every department of the world's work.
Mr. Edward H. Sanborn, in an article on Motive Power Appliances in the
Twelfth Census Report of the United States, comments upon the recent
advances in the use of water wheels as follows:
"One notable advance in turbine construction has been the production
of a type of wheel especially designed for operating under much higher
heads of water than were formerly considered feasible for wheels of
this type. Turbines are now built for heads ranging from 100 to 1,200
feet, and quite a number of wheels are in operation under heads of from
100 to 200 feet. This is an encroachment upon the field occupied almost
exclusively by wheels variously known as the 'impulse,' 'impact,'
'tangential,' or 'jet' type, the principle of which is the impact of
a powerful jet of water from a small nozzle upon a series of buckets
mounted upon the periphery of a small wheel."
"The impact water wheel," Mr. Sanborn continues, "has come largely
into use during the last ten years, principally in the far West,
where higher heads of water are available than can be found in other
parts of the country. With wheels of this type, exceedingly simple
in construction and of comparatively small cost, a large amount of
power is developed with great economy under the great heads that are
available. With the tremendous water pressure developed by heads of
1,000 feet and upward, which in many cases are used for this purpose,
wheels of small diameter develop an extraordinary amount of power.
To the original type of impact wheel which first led the field have
been added several styles embodying practically the same principle.
Considerable study has been given to the designing of buckets with a
view to securing free discharge and the avoidance of any disturbing
eddies, and important improvements have resulted from the thorough
investigation of the action of the water during, and subsequent to,
its impact on the buckets. The impact wheel has been adapted to a wide
range of service with great variation as to the conditions under which
it operates, wheels having been made in California from 30 inches to
30 feet in diameter, and to work under heads ranging from 35 to 2,100
feet, and at speeds ranging from 65 to 1,100 revolutions per minute. A
number of wheels of this type have been built with capacities of not
less than 1,000 horse-power each."
HYDRAULIC POWER
A few words should be said about the familiar method of transmitting
power with the aid of water, as illustrated by the hydrostatic press.
This does not indeed utilize the energy of the water itself, but it
enables the worker to transmit energy supplied from without, and to
gain an indefinite power to move weights through a short distance,
with the expenditure of very little working energy. The principle on
which the hydrostatic press is based is the one which was familiar to
the ancient philosophers under the name of the hydrostatic paradox.
It was observed that if a tube is connected with a closed receptacle,
such as a strong cask, and cask and tube are filled with water, the
cask will presently be burst by the pressure of the water, provided the
tube is raised to a height, even though the actual weight of water in
the tube be comparatively slight. A powerful cask, for example, may be
burst by the water poured into a slender pipe. The result seems indeed
paradoxical, and for a long time no explanation of it was forthcoming.
It remained for Servinus, whose horseless wagon is elsewhere noticed,
to discover that the water at any given level presses equally in all
directions, and that its pressure is proportionate to its depth, quite
regardless of its bulk. Then, supposing the tube in our experiment to
have a cross-section of one square inch, a pressure equal to that in
the tube would be transmitted to each square inch of the surface of the
cask; and the pressure might thus become enormous.
If, instead of a tube lifted to a height, the same tube is connected
with a force pump operated with a lever--an apparatus similar to the
fire-engine of Ctesibius--it is obvious that precisely the same effect
may be produced; whatever pressure is developed in the piston of the
force pump, similar pressure will be transferred to a corresponding
area in the surface of the cask or receptacle with which the force pump
connects. In practise this principle is utilized, where great pressure
is desired, by making a receptacle with an enormous piston connecting
with the force pump just described.
An indefinite power may thus be developed, the apparatus constituting
virtually a gigantic lever. But the principle of the equivalence of
weight and distance still holds, precisely as in an actual lever,
and while the pressure that may be exerted with slight expenditure
of energy is enormous, the distance through which this pressure acts
is correspondingly small. If, for example, the piston of the force
pump has an area of one square inch, while the piston of the press
has an area of several square feet, the pressure exerted will be
measured in tons, but the distance through which it is exerted will be
almost infinitesimal. The range of utility of the hydrostatic press
is, therefore, limited, but within its sphere, it is an incomparable
transmitter of energy.
[Illustration: HYDRAULIC PRESS AND HYDRAULIC CAPSTAN.
The upper figure shows Bramah's original hydraulic pump and press,
now preserved in the South Kensington Museum, London. The machine was
constructed in 1796 by Joseph Bramah to demonstrate the principle of
his hydraulic press. The discrepancy in size between the small lever
worked by hand and the enormous lever carrying a heavy weight gives a
vivid impression of the gain in power through the use of the apparatus.
The lower figure shows the hydraulic capstan used on many modern ships,
in which the same principle is utilized.]
Moreover, it is possible to reverse the action of the hydraulic
apparatus so as to gain motion at the expense of power. A familiar type
of elevator is a case in point. The essential feature of the hydraulic
elevator consists of a ram attached to the bottom of the elevator and
extending down into a cylinder, slightly longer than the height to
which the elevator is to rise. The ram is fitting into a cylinder with
water-tight packing, or a cut leather valve. Water under high pressure
is admitted to the cylinder through the valve at the bottom, and the
pressure thus supplied pushes up the ram, carrying the elevator with
it, of course. Another valve allows the water to escape, so that ram
and elevator may descend, too rapid descent being prevented by the
partial balancing of ram and elevator with weights acting over pulleys.
The ram, to the end of which pressure is thus applied, need be but a
few inches in diameter. Water pressure is secured by bringing water
from an elevation. Such an elevator acts slowly, but is a very safe
and in many ways satisfactory mechanism. Such elevators are still used
extensively in Europe, but have been almost altogether displaced in
America by the electric elevator.
The hydraulic elevator just described is virtually a water engine, the
ram acting as piston. A veritable engine, of small size, to perform
any species of mechanical work, may be constructed on precisely the
same principle, the piston in this case acting in a cylinder similar to
that of the ordinary steam engine. Such an engine operates slowly but
with great power. It has special utility where it is desirable to apply
power intermittently, as in various parts of a dockyard, or in handling
guns and ammunition on shipboard. In the former case in particular,
it is often inconvenient to use steam power, as steam sent from a
central boiler condenses in a way to interfere with its operation. In
such a case any number of small water-pressure engines may be operated
from a single tank where water is at a high elevation, or where the
requisite pressure is secured artificially. In the latter case, the
water is kept under pressure by a large piston or ram heavily weighted,
the entire receptacle being, of course, of water-tight construction
and adapted to withstand pressure. The pump that supplies the tank is
ordinarily made to work automatically, ceasing operation as soon as the
ram rises to the top of the receptacle, and beginning again whenever,
through use of water, the ram begins to descend. Such an apparatus is
called an accumulator. Such water engines have come into vogue only in
comparatively recent times, being suggested by the steam engine. As
already pointed out, their utility is restricted, yet the total number
of them in actual use to-day is large, and their share in the world's
work is not altogether inconsiderable.
V
CAPTIVE MOLECULES: THE STORY OF THE STEAM ENGINE
We come now to that all-important transformer of power, the steam
engine. Everybody knows that steam is a state of water in which,
under the influence of heat, the molecules have broken away from the
mutual attraction of cohesion, and are flying about at inconceivable
speed, rebounding from one another after collision, in virtue of their
elasticity, exerting in the aggregate an enormous pressure in every
direction. It is this consideration of the intimate character of steam
that justifies the title of the present chapter; a title that has
further utility as drawing a contrast between the manner of working
with which we are now to be concerned, and the various types of workers
that we have previously considered.
In speaking of the animal machine and of work accomplished by the air
and the water, we have been concerned primarily with masses of matter,
possessing and transmitting energy. Of course molecules--since they
make up the substance of all matter--could not be altogether ignored,
but in the main we have had to do with molar rather than with molecular
motion. Now, however, we are concerned with a mechanism in which the
molecular activities are directly concerned in performing work.
Even in the aggregate the molecules make up a mere intangible gas,
which requires to be closely confined in order that its energy may be
made available. Once the molecules have performed their work, they
are so changed in their activities that they sink back, as it were,
exhausted, into a relatively quiescent state, which enables their
latent cohesive forces to reduce them again to the state of a liquid.
In a word, we are concerned with the manifestation of energy which
depends upon molecular activities in a way quite different from what
has been the case with any of the previously considered mechanisms.
The tangible manifestation of energy which we term heat is not merely
a condition of action and a by-product, as it was in the case of
the animal machine; it is the essential factor upon which all the
efficiency of the mechanism depends.
It should perhaps be stated that this explanation of the action of
the steam engine is a comparatively modern scientific interpretation.
The earlier experimenters brought the steam engine to a high state of
efficiency, without having any such conception as this of the nature
of steam itself. For practical purposes it suffices to note that water
when heated takes the form of steam; that this steam has the property
of powerful and indefinite expansion; and thirdly, that when allowed to
escape from a state of pressure, sudden expansion of the steam cools it
sufficiently to cause the recondensation of part of its substance, thus
creating a vacuum.
Stated in few words, the entire action of the steam depends upon these
simple mechanical principles. The principles are practically applied
by permitting the steam to enter the cylinder where it can act on
a piston, to which it gives the thrust that is transmitted to an
external mechanism by means of a rod attached to the piston. When the
piston has been driven to the end of the desired thrust, the valve is
opened automatically, permitting the steam to escape, thus producing a
vacuum, and insuring the return thrust of the piston, which is further
facilitated, ordinarily, by the admission of steam to the other side
of the piston. Practical operation of this mechanism is familiar to
everyone, though the marvel of its power and efficiency seems none the
less because of its familiarity.
It is not too much to say that this relatively simple device, in its
first general application, marked one of the most important turning
points in the history of civilization. To its influence, more than to
any other single cause, must be ascribed the revolutionary change that
came over the character of practical life in the nineteenth century.
From prehistoric times till well toward the close of the eighteenth
century, there was scarcely any important change in carrying out the
world's work. And in the few generations that have since elapsed, the
entire aspect of the mechanical world has been changed, the working
efficiency of the individual has been largely increased; mechanical
tasks have become easy which hitherto were scarcely within the range of
human capacity.
Before we go on to the detailed study of the machine which has produced
these remarkable results, it is desirable to make inquiry as to the
historical development of so important an invention.
The practical steam engine in its modern form dates, as just mentioned,
from the latter part of the eighteenth century, and was perfected by
James Watt, who is commonly thought of as being its inventor. In point
of fact, however, the history of most inventions is duplicated here, as
on examination it appears that various forerunners of Watt had been on
the track of the steam engine, and some of them, indeed, had produced a
workable machine of no small degree of efficiency.
The very earliest experiments were made away back in the Alexandrian
days in the second century before the Christian era, the experimenter
being the famous Hero, whose work in an allied field was referred to
in the preceding chapter. Hero produced--or at least described and so
is credited with producing, though the actual inventor may have been
Ctesibius--a little toy mechanism, in which a hollow ball was made to
revolve on an axis through the agency of steam, which escaped from
two bent tubes placed on opposite sides of the ball, their orifices
pointing in opposite directions. The apparatus had no practical
utility, but it sufficed to establish the principle that heat, acting
through the agency of steam, could be made to do mechanical work. Had
not the age of Hero been a time of mental stasis, it is highly probable
that the principle he had thus demonstrated would have been applied
to some more practical mechanism in succeeding generations. As it
was, however, nothing practical came of his experiment, and the steam
turbine engine was remembered only as a scientific toy.
No other worker continued the experiments, so far as is known, until
the time of the great Italian, Leonardo da Vinci, who, late in the
fifteenth century, gave a new impulse to mechanical invention. Leonardo
experimented with steam, and succeeded in producing what was virtually
an explosion engine, by the agency of which a ball was propelled along
the earth. But this experiment also failed to have practical result.
BEGINNINGS OF MODERN DISCOVERY
Such sporadic experiments as these have no sequential connection with
the story of the evolution of the steam engine. The experiments which
led directly on to practical achievements were not begun until the
seventeenth century. In the very first year of that century, an Italian
named Giovanni Battista della Porta published a treatise on pneumatics,
in which the idea of utilizing steam for the practical purpose of
raising water was expressly stated. The idea of this inventor was put
into effect in 1624 by a French engineer and mathematician, Solomon de
Caus. He invented two different machines, the first of which required a
spherical boiler having an internal tube reaching nearly to the bottom;
a fire beneath the boiler produced steam which would force the water in
the boiler to a height proportional to the pressure obtained. In the
other machine, steam is led from the boiler into the upper part of a
closed cistern containing water to be elevated. To the lower portion of
the cistern a delivery pipe was attached so that water was discharged
under a considerable pressure. This arrangement was precisely similar
to the apparatus employed by Hero of Alexandria in various of his
fountains, as regards the principle of expanding gas to propel water.
An important difference, however, consists in the fact that the
scheme of della Porta and of de Caus embodied the idea of generating
pressure with the aid of steam, whereas Hero had depended merely on the
expansive property of air compressed by the water itself.
While these mechanisms contained the germ of an idea of vast
importance, the mechanisms themselves were of trivial utility. It is
not even clear whether their projectors had an idea of the properties
of the condensation of vapor, upon which the working of the practical
steam engine so largely depends. This idea, however, was probably
grasped about half a century later by an Englishman, Edward Somerset,
the celebrated Marquis of Worcester, who in 1663 described in his
_Century of Inventions_ an apparatus for raising water by the expansive
force of steam. His own account of his invention is as follows:
"An admirable and most forcible way to drive up water by fire; not by
drawing or sucking it upwards, for that must be as the philosopher
calleth it, _intra sphæram activitatis_, which is but at such a
distance. But this way hath no bounder, if the vessel be strong enough:
for I have taken a piece of whole cannon, whereof the end was burst,
and filled it three-quarters full of water, stopping and screwing up
the broken end, as also the touch-hole; and making a constant fire
under it, within twenty-four hours it burst and made a great crack; so
that having a way to make my vessels so that they are strengthened by
the force within them, and the one to fill after the other, I have seen
the water run like a constant stream, forty feet high: one vessel of
water, rarefied by fire, driveth up forty of cold water; and the man
that tends the work is but to turn two cocks, that one vessel of water
being consumed, another begins to force and refill with cold water,
and so successively; the fire being tended and kept constant, which
the self-same person may likewise abundantly perform in the interim,
between the necessity of turning the said cocks."
It is unfortunate that the Marquis did not give a more elaborate
description of this remarkable contrivance. The fact that he treats it
so casually is sufficient evidence that he had no conception of the
possibilities of the mechanism; but, on the other hand, his description
suffices to prove that he had gained a clear notion of, and had
experimentally demonstrated, the tremendous power of expansion that
resides in steam. No example of his steam pump has been preserved, and
historians of the subject have been left in doubt as to some details
of its construction, and in particular as to whether it utilized the
principle of a vacuum created through condensation of the steam.
THOMAS SAVERY'S STEAM PUMP
This principle was clearly grasped, however, by another Englishman,
Thomas Savery, a Cornish mine captain, who in 1698 secured a patent for
a steam engine to be applied to the raising of water, etc. A working
model of this machine was produced before the Royal Society in 1699.
The transactions of the Society contain the following: "June 14th,
1699, Mr. Savery entertained the Royal Society with showing a small
model of his engine for raising water by help of fire, which he set to
work before them: the experiment succeeded according to expectation,
and to their satisfaction."
The following very clear description of Savery's engine is given in the
introduction to Beckmann's _History of Inventions_:
"This engine, which was used for some time to a considerable extent for
raising water from mines, consisted of a strong iron vessel shaped like
an egg, with a tube or pipe at the bottom, which descended to the place
from which the water was to be drawn, and another at the top, which
ascended to the place to which it was to be elevated. This oval vessel
was filled with steam supplied from a boiler, by which the atmospheric
air was first blown out of it. When the air was thus expelled and
nothing but pure steam left in the vessel, the communication with the
boiler was cut off, and cold water poured on the external surface. The
steam within was thus condensed and a vacuum produced, and the water
drawn up from below in the usual way by suction. The oval vessel was
thus filled with water; a cock placed at the bottom of the lower pipe
was then closed, and steam was introduced from the boiler into the
oval vessel above the surface of the water. This steam being of high
pressure, forced the water up the ascending tube, from the top of
which it was discharged, and the oval vessel being thus refilled with
steam, the vacuum was again produced by condensation, and the same
process was repeated. By using two oval steam vessels, which would act
alternately--one drawing water from below, while the other was forcing
it upwards, an uninterrupted discharge of water was produced. Owing to
the danger of explosion, from the high pressure of the steam which was
used, and from the enormous waste of heat by unnecessary condensation,
these engines soon fell into disuse."
[Illustration: THOMAS SAVERY'S STEAM ENGINE.
The principle involved is that of the expansion of steam exerting a
propulsive force and its subsequent condensation to produce a vacuum.
These are the principles employed in the modern steam engine, but the
only use to which they were put in Savery's engine was the elevation of
water by suction.]
This description makes it obvious that Savery had the clearest
conception of the production of a vacuum by the condensation of steam,
and of the utilization of the suction thus established (which suction,
as we know, is really due to the pressure of outside air) to accomplish
useful work. Savery also arranged this apparatus in duplicate, so that
one vessel was filling with water while the other was forcing water
to the delivery pipe. This is credited with being the first useful
apparatus for raising water by the combustion of fuel. There was a
great waste of steam, through imparting heat to the water, but the
feasibility of the all-important principle of accomplishing mechanical
labor with the aid of heat was at last demonstrated.
As yet, however, the experimenters were not on the track of the
method by which power could be advantageously transferred to outside
machinery. An effort in quite another direction to accomplish this
had been made as early as 1629 by Giovanni Branca, an Italian
mathematician, who had proposed to obtain rotary motion by allowing
a jet of steam to blow against the vanes of a fan wheel, capable of
turning on an axis. In other words, he endeavored to utilize the
principle of the windmill, the steam taking the place of moving air.
The idea is of course perfectly feasible, being indeed virtually that
which is employed in the modern steam turbine; but to put the idea
into practise requires special detailed arrangements of steam jet and
vanes, which it is not strange the early inventor failed to discover.
His experiments appear not to have been followed up by any immediate
successor, and nothing practical came of them, nor was the principle
which he had attempted to utilize made available until long after a
form of steam engine utilizing another principle for the transmission
of power had been perfected.
DENIS PAPIN INVENTS THE PISTON ENGINE
The principle in question was that of causing expanding steam to press
against a piston working tightly in a cylinder, a principle, in short,
with which everyone is familiar nowadays through its utilization in
the ordinary steam engine. The idea of making use of such a piston
appears to have originated with a Frenchman, Denis Papin, a scientific
worker, who, being banished from his own country, was established as
professor of mathematics at the University of Marburg. He conceived the
important idea of transmitting power by means of a piston as early as
1688, and about two years later added the idea of producing a vacuum in
a cylinder, by cooling the cylinder,--the latter idea being, as we have
just seen, the one which Savery put into effect.
[Illustration: DIAGRAMS OF EARLY ATTEMPTS TO UTILIZE THE POWER OF
STEAM. GIOVANNI BRANCA 1629 GUILLAUME AMONTONS 1699 Two attempts
to give rotation to a mechanical apparatus through the action of
heated air or steam. Nothing practical came of either effort, but the
mechanisms depicted are of historical interest.]
It will be noted that Papin's invention antedated that of Savery; to
the Frenchman, therefore, must be given the credit of hitting upon two
important principles which made feasible the modern steam engine. Papin
constructed a model consisting of a small cylinder in which a solid
piston worked. In the cylinder beneath the piston was placed a small
quantity of water, which, when the cylinder was heated, was turned
into steam, the elastic force of which raised the piston. The cylinder
was then cooled by removing the fire, when the steam condensed, thus
creating a vacuum in the cylinder, into which the piston was forced by
the pressure of the atmosphere.
Such an apparatus seems crude enough, yet it incorporates the essential
principles, and required but the use of ingenuity in elaborating
details of the mechanism, to make a really efficient steam engine.
It would appear, however, that Papin was chiefly interested in the
theoretical, rather than in the really practical side of the question,
and there is no evidence of his having produced a working machine of
practical power, until after such machines worked by steam had been
constructed elsewhere.
THOMAS NEWCOMEN'S IMPROVED ENGINE
As has happened so often in other fields, Englishmen were the first
to make practical use of the new ideas. In 1705 Thomas Newcomen, a
blacksmith or ironmonger, and John Cawley, a plumber and glazier,
patented their atmospheric engine, and five years later, in the year
1710, namely, Newcomen had on the market an engine which is described
in the _Report of the Department of Science and Arts of the South
Kensington Museum_, as "the first real pumping engine ever made."
The same report describes the engine as "a vertical steam cylinder
provided with a piston connected at one end of the beam, having a
pivot or bearing in the middle of its length, and at the other end of
the beam pump rods for working the pump. The cylinder was surrounded
by a second cylinder or jacket, open at the top, and cold water could
be supplied to this outer cylinder at pleasure. The single or working
cylinder could be supplied with steam when desired from a boiler below
it. There was a drain pipe from the bottom of the working cylinder,
and one from the outer cylinder. For the working of the engine steam
was admitted to the working cylinder, so as to fill it and expel all
the air, the piston then being at the top, owing to the weight of the
pump rods being sufficient to lift it; then the steam was shut off and
the drain cocks closed and cold water admitted to the outer cylinder,
so that the steam in the working cylinder condensed, and, leaving a
partial vacuum of pressure of the atmosphere, forced the piston down
and drew up the pump rods, thus making a stroke of the pump. Then the
water was drawn off from the outer cylinder and steam admitted to the
working cylinder before allowing the piston to return to the top of its
stroke, ready for the next down stroke."
It will be observed that this machine adopts the principle, with only
a change of mechanical details, of the Papin engine just described. A
later improvement made by Newcomen did away with the outer cylinder
for condensing the steam, employing instead an injection of cold water
into the working cylinder itself, thus enabling the engine to work more
quickly. It is said that the superiority of the internal condensing
arrangement was accidentally discovered through the improved working
of an engine that chanced to have an exceptionally leaky piston or
cylinder. Many engines were made on this plan and put into practical
use.
Another important improvement was made by a connection from the beam
to the cocks or valves, so that the engine worked automatically,
whereas in the first place it had been necessary to have a boy or man
operate the valves,--a most awkward arrangement, in the light of modern
improvements. As the story is told, the duty of opening and closing
the regulating and condensing valves was intrusted to boys called
cock boys. It is said that one of these boys named Humphrey Potter
"wishing to join his comrades at play without exposing himself to the
consequences of suspending the performance of the engine, contrived, by
attaching strings of proper length to the levers which governed the two
cocks, to connect them with the beam, so that it should open and close
the cocks as it moved up and down with the most perfect regularity."
This story has passed current for almost two centuries, and it has been
used to point many a useful moral. It seems almost a pity to disturb
so interesting a tradition, yet it must have occurred to more than one
iconoclast that the tale is almost too good to be true. And somewhat
recently it has been more than hinted that Desaguliers, with whom the
story originated, drew upon his imagination for it. A print is in
existence, made so long ago as 1719, representing an engine erected
by Newcomen at Dudley Castle, Staffordshire, in 1712, in which an
automatic valve gear is clearly shown, proving that the Newcomen engine
was worked automatically at this early period. That the admirable
story of the inventive youth, whose wits gave him leisure for play,
may not be altogether discredited, however, it should be added that
unquestionably some of the early engines had a hand-moved gear, and
that at least one such was still working in England after the middle of
the nineteenth century. It seems probable, then, that the very first
engines were without the automatic valve gear, and there is no inherent
reason why a quick-witted youth may not have been the first to discover
and remedy the defect.
According to the Report of the Department of Science and Arts of
the South Kensington Museum: "The adoption of Newcomen's engine was
rapid, for, commencing in 1711 with the engine at Wolverhampton, of
twenty-three inch diameter and six foot stroke, they were in common use
in English collieries in 1725; and Smeaton found in 1767 that, in the
neighborhood of Newcastle alone there were fifty-seven at work, ranging
in size from twenty-eight inch to seventy-five inch cylinder diameter,
and giving collectively about twelve hundred horse-power. As Newcomen
obtained an evaporation of nearly eight pounds of water per pound of
coal, the increase of boiler efficiency since his time has necessarily
been but slight, although in other requisites of the steam generator
great improvements are noticeable."
[Illustration: A MODEL OF THE NEWCOMEN ENGINE.
This engine has particular interest not only because it was a practical
pumping engine, but also because it was while repairing an engine of
this type that Watt was led to the experiments that resulted in his
epoch-making discovery.]
THE COMING OF JAMES WATT
The Newcomen engine had low working efficiency as compared with the
modern engine; nevertheless, some of these engines are still used in a
few collieries where waste coal is available, the pressure enabling the
steam to be generated in boilers unsafe for other purposes. The great
importance of the Newcomen engine, however, is historical; for it was
while engaged in repairing a model of one of these engines that James
Watt was led to invent his plan of condensing the steam, not in the
working cylinder itself, but in a separate vessel,--the principle upon
which such vast improvements in the steam engine were to depend.
It is impossible to overestimate the importance of the work which Watt
accomplished in developing the steam engine. Fully to appreciate it,
we must understand that up to this time the steam engine had a very
limited sphere of usefulness. The Newcomen engine represented the
most developed form, as we have seen; and this, like the others that
it had so largely superseded, was employed solely for the pumping of
water. In the main, its use was confined to mines, which were often
rendered unworkable because of flooding. We have already seen that a
considerable number of engines were in use, yet their power in the
aggregate added but a trifle to man's working efficiency, and the work
that they did accomplish was done in a most uneconomical manner. Indeed
the amount of fuel required was so great as to prohibit their use in
many mines, which would have been valuable could a cheaper means have
been found of freeing them from water. Watt's inventions, as we shall
see, accomplished this end, as well as various others that were not
anticipated.
It was through consideration of the wasteful manner of action of the
steam engine that Watt was led to give attention to the subject.
The great inventor was a young man at the University of Glasgow. He
had previously served an apprenticeship of one year with a maker of
philosophical instruments in London, but ill health had prevented him
from finishing his apprenticeship, and he had therefore been prohibited
from practising his would-be profession in Glasgow. Finally, however,
he had been permitted to work under the auspices of the University;
and in due course, as a part of his official duties, he was engaged
in repairing a model of the Newcomen engine. This incident is usually
mentioned as having determined the line of Watt's future activity.
It should be recalled, however, that Watt had become a personal friend
of the celebrated Professor Black, the discoverer of latent heat, and
the foremost authority in the world, in this period, on the study of
pneumatics. Just what share Black had in developing Watt's idea, or
in directing his studies toward the expansive properties of steam,
it would perhaps be difficult to say. It is known, however, that the
subject was often under discussion; and the interest evinced in it by
Black is shown by the fact that he subsequently wrote a history of
Watt's inventions.
It is never possible, perhaps, for even the inventor himself to re-live
the history of the growth of an idea in his own mind. Much less is it
possible for him to say precisely what share of his progress has been
due to chance suggestions of others. But it is interesting, at least,
to recall this association of Watt with the greatest experimenter of
his age in a closely allied field. Questions of suggestion aside,
it illustrates the technical quality of Watt's mind, making it
obvious that he was no mere ingenious mechanic, who stumbled upon his
invention. He was, in point of fact, a carefully trained scientific
experimenter, fully equipped with all the special knowledge of his time
in its application to the particular branch of pneumatics to which he
gave attention.
The first and most obvious defect in the Newcomen engine was, as Watt
discovered, that the alternating cooling and heating of the cylinder
resulted in an unavoidable waste of energy. The apparatus worked, it
will be recalled, by the introduction of steam into a vertical cylinder
beneath the piston, the cylinder being open above the piston to admit
the air. The piston rod connected with a beam suspended in the middle,
which operated the pump, and which was weighted at one end in order
to facilitate the raising of the piston. The steam, introduced under
low pressure, scarcely more than counteracted the pressure of the air,
the raising of the piston being largely accomplished by the weight in
question.
Of course the introduction of the steam heated the cylinder. In order
to condense the steam and produce a vacuum, water was injected, the
cylinder being thereby cooled. A vacuum being thus produced beneath
the cylinder, the pressure of the air from above thrust the cylinder
down, this being the actual working agent. It was for this reason
that the Newcomen engine was called, with much propriety, a pneumatic
engine. The action of the engine was very slow, and it was necessary to
employ a very large piston in order to gain a considerable power.
The first idea that occurred to Watt in connection with the probable
improvement of this mechanism did not look to the alteration of any of
the general features of the structure, as regards size or arrangement
of cylinder, piston, or beam, or the essential principle upon which
the engine worked. His entire attention was fixed on the discovery
of a method by which the loss of heat through periodical cooling of
the cylinder could be avoided. We are told that he contemplated the
subject long, and experimented much, before he reached a satisfactory
solution. Naturally enough his attention was first directed toward the
cylinder itself. He queried whether the cylinder might not be made of
wood, which, through its poor conduction of heat, might better equalize
the temperature. Experiments in this direction, however, produced no
satisfactory result.
[Illustration: WATT'S EARLIEST TYPE OF PUMPING ENGINE.
The lower figure shows the ruins of Watt's famous engine "Old Bess."
The upper figure shows a reconstructed model of the "Old Bess" engine.
It will be noted that the walking beam is precisely of the Newcomen
type. In fact, the entire engine is obviously only a modification
of the Newcomen engine. It had, however, certain highly important
improvements, as described in the text.]
Then at last an inspiration came to him. Why not connect the cylinder
with another receptacle, in which the condensation of the steam could
be effected? The idea was a brilliant one, but neither its originator
nor any other man of the period could possibly have realized its vast
and all-comprehending importance. For in that idea was contained the
germ of all the future of steam as a motive power. Indeed, it scarcely
suffices to speak of it as the germ merely; the thing itself was
there, requiring only the elaboration of details to bring it to
perfection.
Watt immediately set to work to put his brilliant conception of the
separate condenser to the test of experiment. He connected the cylinder
of a Newcomen engine with a receptacle into which the steam could be
discharged after doing its work on the piston. The receptacle was
kept constantly cooled by a jet of water, this water and the water
of condensation, together with any air or uncondensed steam that
might remain in the receptacle, being constantly removed with the
aid of an air pump. The apparatus at once demonstrated its practical
efficiency,--and the modern steam engine had come into existence.
It was in the year 1765, when Watt was twenty-nine years old, that he
made his first revolutionary experiment, but his first patents were
not taken out until 1769, by which time his engine had attained a
relatively high degree of perfection. In furthering his idea of keeping
the cylinder at an even temperature, he had provided a covering for it,
which might consist of wood or other poorly conducting material, or a
so-called jacket of steam--that is to say, a portion of steam admitted
into the closed chamber surrounding the cylinder. Moreover, the
cylinder had been closed at the top, and a portion of steam admitted
above the piston, to take the place of the atmosphere in producing the
down stroke. This steam above the piston, it should be explained, did
not connect with the condensing receptacle, so the engine was still
single-acting; that is to say it performed work only during one stroke
of the piston. A description of the mechanism at this stage of its
development may best be given in the words of the inventor himself, as
contained in his specifications in the application for patent on his
improvements in 1769.
"My method of lessening the consumption of steam, and consequently
fuel, in fire-engines, consists of the following principles:
"First, That vessel in which the powers of steam are to be employed to
work the engine, which is called the cylinder in common fire-engines,
and which I call the steam vessel, must, during the whole time the
engine is at work, be kept as hot as the steam that enters it; first
by enclosing it in a case of wood, or any other materials that
transmit heat slowly; secondly, by surrounding it with steam or other
heated bodies; and, thirdly, by suffering neither water nor any other
substance colder than the steam to enter or touch it during that time.
"Secondly, In engines that are to be worked wholly or partially
by condensation of steam, the steam is to be condensed in vessels
distinct from the steam vessels or cylinders, although occasionally
communicating with them; these vessels I call condensers; and, whilst
the engines are working, these condensers ought at least to be kept as
cold as the air in the neighborhood of the engines, by application of
water or other cold bodies.
"Thirdly, Whatever air or other elastic vapor is not condensed by the
cold of the condenser, and may impede the working of the engine, is to
be drawn out of the steam vessels or condensers by means of pumps,
wrought by the engines themselves, or otherwise.
"Fourthly, I intend in many cases to employ the expansive force of
steam to press on the pistons, or whatever may be used instead of them,
in the same manner in which the pressure of the atmosphere is now
employed in common fire-engines. In cases where cold water can not be
had in plenty, the engines may be wrought by this force of steam only,
by discharging the steam into the air after it has done its office.
"Sixthly, I intend in some cases to apply a degree of cold not capable
of reducing the steam to water, but of contracting it considerably,
so that the engines shall be worked by the alternate expansion and
contraction of the steam.
"Lastly, Instead of using water to render the pistons and other parts
of the engine air-and steam-tight, I employ oils, wax, resinous bodies,
fat of animals, quicksilver and other metals in their fluid state."
ROTARY MOTION
It must be understood that Watt's engine was at first used exclusively
as an apparatus for pumping. For some time there was no practical
attempt to apply the mechanism to any other purpose. That it might
be so applied, however, was soon manifest, in consideration of the
relative speed with which the piston now acted. It was not until 1781,
however, that Watt's second patent was taken out, in which devices are
described calculated to convert the reciprocating motion of the piston
into motion of rotation, in order that the engine might drive ordinary
machinery.
It seems to be conceded that Watt was himself the originator of the
idea of making the application through the medium of a crank and
fly-wheel such as are now universally employed. But the year before
Watt took out his second patent, another inventor named James Picard
had patented this device of crank and connecting rod, having, it is
alleged, obtained the idea from a workman in Watt's employ. Whatever
be the truth as to this point, Picard's patent made it necessary for
Watt to find some alternative device, and after experimenting, he hit
upon the so-called sun and planet gearing, and henceforth this was used
on his rotary engines until the time for the expiration of Picard's
patent, after which the simpler and more satisfactory crank and
fly-wheel were adopted.
In the meantime, Watt had associated himself with a business partner
named Boulton, under the firm name of Boulton and Watt. In 1776 a
special act of legislation extending the term of Watt's original patent
for a period of twenty-five years had been secured. All infringements
were vigorously prosecuted, and the inventor, it is gratifying to
reflect, shared fully in the monetary proceeds that accrued from his
invention.
[Illustration: WATT'S ROTATIVE ENGINE.
The lower figure shows the earliest type of mechanism through which
Watt applied his engine to other uses than that of pumping. The
so-called sun-and-planet gearing, through which rotary motion was
attained, is seen at the lower right-hand corner of the figure. The
upper figure shows a later and much improved type of the Watt engine,
in which the sun-and-planet gearing has been supplanted by a simple
crank.]
Notwithstanding the early recognition of the possibility of securing
rotary motion with Watt's perfected Newcomen engine, it was long
before the full possibilities of the application of this principle
were realized, even by the most practical of machinists. Watt himself
apparently appreciated the possibilities no more fully than the
others, as the use of his famous engines "Beelzebub" and "Old Bess"
in the establishment of Boulton and Watt amply testifies. It appears
that Boulton had been an extensive manufacturer of ornamental metal
articles. To drive his machinery at Soho he employed two large water
wheels, twenty-four feet in diameter and six feet wide. These sufficed
for his purpose under ordinary conditions, but in dry weather from
six to ten horses were required to aid in driving the machinery. When
Watt's perfected engine was available, however, this was utilized to
pump water from the tail race back to the head race, that it might be
used over and over. "Old Bess" had a cylinder thirty-three inches in
diameter with seven-foot stroke, operating a pump twenty-four inches
in diameter; it therefore had remarkable efficiency as a pumping
apparatus. But of course it utilized, at best, only a portion of the
working energy contained in the steam; and the water wheels in turn
could utilize not more than fifty per cent. of the store of energy
which the pump transferred to the water in raising it. Therefore, such
use of the steam engine involved a most wasteful expenditure of energy.
It was long, however, before the practical machinists could be made to
believe that the securing of direct rotary power from the piston could
be satisfactorily accomplished. It was only after the introduction of
higher speed and heavier fly-wheels, together with improved governors,
that the speed of rotation was so equalized as to meet satisfactorily
the requirements of the practical engineer, and ultimately to displace
the wasteful method of securing rotary motion indirectly through the
aid of pump and water wheel. It may be added, that the centrifugal
governor, with which modern engines are provided to regulate their
speed, was the invention of Watt himself.
FINAL IMPROVEMENTS AND MISSED OPPORTUNITIES
In the year 1782 Watt took out patents which contained specifications
for the two additional improvements that constituted his final
contribution to the production of the steam engine. The first of these
provided for the connection of the cylinder chamber on each side of the
piston with the condenser, so that the engine became double acting. The
second introduced the very important principle,--from the standpoint of
economy in the use of steam--of shutting off the supply of steam from
the cylinder while the piston has only partially traversed its thrust,
and allowing the remainder of the thrust to be accomplished through
the expansion of the steam. The application of the first of these
principles obviously adds greatly to the efficiency of the engine, and
in practise it was found that the application of the second principle
produces a very great saving in steam, and thus adds materially to the
economical working of the engine.
All of Watt's engines continued to make use of the walking beam
attached to the piston for the transmission of power; and engineers
were very slow indeed to recognize the fact that in many--in fact in
most--cases this contrivance may advantageously be done away with. The
recognition of this fact constitutes one of the three really important
advances that have been made in the steam engine since the time of
Watt. The other two advances consist of the utilization of steam under
high pressure, and of the introduction of the principle of the compound
engine.
Neither of these ideas was unknown to Watt, since the utilization
of steam under high pressure was advocated by his contemporary,
Trevithick, while the compound engine was invented by another
contemporary named Hornblower. Perhaps the very fact that these rival
inventors put forward the ideas in question may have influenced Watt
to antagonize them; in particular since his firm came into legal
conflict with each of the other inventors. At any rate, Watt continued
to the end of his life to be an ardent advocate of low pressure for
the steam engine, and his firm even attempted to have laws passed
making it illegal--on the ground of danger to human life--to utilize
high-pressure steam, such as employed by Trevithick.
Possibly the conservatism of increasing age may also have had its
share in rendering Watt antagonistic to the new ideas; for he was
similarly antagonistic to the idea of applying steam to the purposes
of locomotion. Trevithick, among others, had, as we shall see in due
course, made such application with astonishing success, producing
a steam automobile which traversed the highway successfully. In
his earlier years Watt had conceived the same idea, and had openly
expressed his opinion that the steam engine might be used for this
purpose. But late in life he was so antipathetic to the idea that he
is said to have put a clause in the lease of his house, providing that
no steam carriage should under any pretext be allowed to approach it.
These incidents have importance as showing--as we shall see illustrated
again and again in other fields--the disastrous influence in retarding
progress that may be exercised by even the greatest of scientific
discoverers, when authority well earned in earlier years is exercised
in an unfortunate direction later in life. But such incidents as
these are inconsequential in determining the position among the
world's workers of the man who was almost solely responsible for the
transformation of the steam engine from an expensive and relatively
ineffective pumping apparatus, to the great central power that has ever
since moved the major part of the world's machinery.
THE SUPREME IMPORTANCE OF WATT
It is speaking well within bounds to say that no other invention
within historical times has had so important an influence upon the
production of property--which, as we have seen, is the gauge of the
world's work--as this invention of the steam engine. We have followed
the history of that invention in some detail, because of its supreme
importance. To the reader who was not previously familiar with that
history, it may seem surprising that after a lapse of a little over
a century one name and one alone should be popularly remembered in
connection with the invention; whereas in point of fact various workers
had a share in the achievement, and the man whose name is remembered
was among the last to enter the field. We have seen that the steam
engine existed as a practical working machine several decades before
Watt made his first invention; and that what Watt really accomplished
was merely the perfecting of an apparatus which already had attained a
considerable measure of efficiency.
There would seem, then, to be a certain lack of justice in ascribing
supreme importance to Watt in connection with the steam engine. Yet
this measure of injustice we shall find, as we examine the history of
various inventions, to be meted always by posterity in determining the
status of the men whom it is pleased to honor. One practical rule, and
one only, has always determined to whom the chief share of glory shall
be ascribed in connection with any useful invention.
The question is never asked as to who was the originator of the idea,
or who made the first tentative efforts towards its utilization,--or,
if asked by the historical searcher, it is ignored by the generality of
mankind.
So far as the public verdict, which in the last resort determines
fame, is concerned, the one question is, Who perfected the apparatus
so that it came to have general practical utility? It may be, and
indeed it usually is the case, that the man who first accomplished the
final elaboration of the idea, made but a comparatively slight advance
upon his predecessors; the early workers produced a machine that was
_almost_ a success; only some little flaw remained in their plans. Then
came the perfecter, who hit upon a device that would correct this last
defect,--and at last the mechanism, which hitherto had been only a
curiosity, became a practical working machine.
In the case of the steam engine, it might be said that even a smaller
feat than this remained to be accomplished when Watt came upon the
scene; since the Newcomen engine was actually a practical working
apparatus. But the all-essential thing to remember is that this
Newcomen engine was used for a single purpose. It supplied power for
pumping water, and for nothing else. Neither did it have possibilities
much beyond this, until the all-essential modification was suggested by
Watt, of exhausting its steam into exterior space.
This modification is in one sense a mere detail, yet it illustrates
once more the force of Michelangelo's famous declaration that trifles
make perfect; for when once it was tested, the whole practical
character of the steam engine was changed. From a wasteful consumer of
fuel, capable of running a pump at great expense, it became at once a
relatively economical user of energy, capable of performing almost any
manner of work.
Needless to say, its possibilities in this direction were not
immediately realized, in theory or in practise; yet the conquest that
it made of almost the entire field of labor resulted in the most
rapid transformation of industrial conditions that the world has ever
experienced. After all, then, there is but little injustice in that
public verdict which remembers James Watt as the inventor, rather than
as the mere perfecter, of the steam engine.
THE PERSONALITY OF JAMES WATT
The man who occupies this all-important position in the industrial
world demands a few more words as to his personality. His work we have
sufficiently considered, but before we pass on to the work of his
successors, it will be worth our while to learn something more of the
estimate placed upon the man himself. Let us quote, then, from some
records written by men who were of the same generation.
"Independently of his great attainments in mechanics, Mr. Watt was
an extraordinary and in many respects a wonderful man. Perhaps no
individual in his age possessed so much, or remembered what he had read
so accurately and well. He had infinite quickness of apprehension, a
prodigious memory, and a certain rectifying and methodizing power of
understanding which extracted something precious out of all that was
presented to it. His stores of miscellaneous knowledge were immense,
and yet less astonishing than the command he had at all times over
them. It seemed as if every subject that was casually started in
conversation had been that which he had been last occupied in studying
and exhausting; such was the copiousness, the precision, and the
admirable clearness of the information which he poured out upon it
without effort or hesitation. Nor was this promptitude and compass of
knowledge confined, in any degree, to the studies connected with his
ordinary pursuits.
"That he should have been minutely and extensively skilled in
chemistry, and the arts, and in most of the branches of physical
science, might, perhaps, have been conjectured; but it could not have
been inferred from his usual occupations, and probably is not generally
known, that he was curiously learned in many branches of antiquity,
metaphysics, medicine, and etymology, and perfectly at home in all
the details of architecture, music, and law. He was well acquainted,
too, with most of the modern languages, and familiar with their most
recent literature. Nor was it at all extraordinary to hear the great
mechanician and engineer detailing and expounding, for hours together,
the metaphysical theories of the German logicians, or criticizing the
measures or the matter of the German poetry.
"It is needless to say, that with those vast resources, his
conversation was at all times rich and instructive in no ordinary
degree. But it was, if possible, still more pleasing than wise, and
had all the charms of familiarity, with all the substantial treasures
of knowledge. No man could be more social in his spirit, less assuming
or fastidious in his manners, or more kind and indulgent towards
all who approached him. His talk, too, though overflowing with
information, had no resemblance to lecturing, or solemn discoursing;
but, on the contrary, was full of colloquial spirit and pleasantry.
He had a certain quiet and grave humor, which ran through most of his
conversation, and a vein of temperate jocularity, which gave infinite
zest and effect to the condensed and inexhaustible information which
formed its main staple and characteristic. There was a little air of
affected testiness, and a tone of pretended rebuke and contradiction,
which he used towards his younger friends, that was always felt by
them as an endearing mark of his kindness and familiarity, and prized
accordingly, far beyond all the solemn compliments that proceeded from
the lips of authority. His voice was deep and powerful; though he
commonly spoke in a low and somewhat monotonous tone, which harmonized
admirably with the weight and brevity of his observations, and set off
to the greatest advantage the pleasant anecdotes which he delivered
with the same grave tone, and the same calm smile playing soberly on
his lips.
[Illustration: JAMES WATT.]
"There was nothing of effort, indeed, or of impatience, any more than
of pride or levity, in his demeanor; and there was a finer expression
of reposing strength, and mild self-possession in his manner, than we
ever recollect to have met with in any other person. He had in his
character the utmost abhorrence for all sorts of forwardness, parade,
and pretension; and indeed never failed to put all such impostors out
of countenance, by the manly plainness and honest intrepidity of his
language and deportment.
"He was twice married, but has left no issue but one son, associated
with him in his business and studies, and two grandchildren by a
daughter who predeceased him. He was fellow of the Royal Societies both
of London and Edinburgh, and one of the few Englishmen who were elected
members of the National Institute of France. All men of learning and
of science were his cordial friends; and such was the influence of his
mild character, and perfect fairness and liberality, even upon the
pretender to these accomplishments, that he lived to disarm even envy
itself, and died, we verily believe, without a single enemy."
VI
THE MASTER WORKER
We have already pointed out at some length that, in the hands of Watt,
the steam engine came at once to be a relatively perfect apparatus, and
that only three really important modifications have been applied to it
since the day of its great perfecter. These modifications, as already
named, are the doing away with the walking beam, the utilization of
high pressure steam, and the development of the compound engine. Each
of these developments requires a few words of explanation.
The retention of the heavy walking beam for so long a time after the
steam engine of Watt had been applied to the various purposes of
machinery, illustrates the power of a pre-conceived idea. With the
Newcomen engine this beam was an essential, since it was necessary
to have a weight to assist in raising the piston. But with the
introduction of steam rather than air as the actual power to push the
piston, and in particular with the elaboration of the double-chamber
cylinder, with steam acting equally on either side of the piston, the
necessity for retaining this cumbersome contrivance no longer existed.
Yet we find all the engines made by Watt himself, and nearly all those
of his contemporaries, continuing to utilize this means of transmitting
the power of the piston. Even the road locomotive, as illustrated by
that first wonderful one of Trevithick's and such colliery locomotives
as "Puffing Billy" and "Locomotion," utilized the same plan. It was not
until almost a generation later that it became clear to the mechanics
that in many cases, indeed in most cases, this awkward means of
transmitting power was really a needlessly wasteful one, and that with
the aid of fly-wheel and crank-shaft the thrust of the piston might be
directly applied to the wheel it was destined to turn, quite as well as
through the intermediary channel of the additional lever.
The utility of the beam has, indeed, still commended it for certain
purposes, notably for the propulsion of side-wheel steamers, such as
the familiar American ferryboat. But aside from such exceptional uses,
the beam has practically passed out of existence.
There was no new principle involved in effecting this change. It was
merely another illustration of the familiar fact that it is difficult
to do things simply. As a rule, inventors fumble for a long time with
roundabout and complex ways of doing things, before a direct and simple
method occurs to them. In other words, the highest development often
passes from the complex to the simple, illustrating, as it were, an
oscillation in the great law of evolution. So in this case, even so
great an inventor as Watt failed to see the utility of doing away with
the cumbersome structure which his own invention had made no longer
a necessity, but rather a hindrance to the application of the steam
engine. However, a new generation, no longer under the thraldom of
the ideas of the great inventor, was enabled to make the change,
gradually, but in the end effectively.
HIGH-PRESSURE STEAM
As regards the use of steam under high pressure, somewhat the same
remarks apply, so far as concerns the conservatism of mankind, and
the influence which a great mind exerts upon its generation. Just why
Watt should have conceived an antagonism to the idea of high-pressure
steam is not altogether clear. It has been suggested, indeed, that
this might have been due to the fact that a predecessor of Watt had
invented a high-pressure engine which did not use the principle of
condensation, but exhausted the steam into open space. As early as
1725, indeed, Leupold in his _Theatrum Machinarum_, had described
such a non-condensing engine, which, had it been made practically
useful, would have required a high pressure of steam. Partly through
the influence of this work, perhaps, there came to be an association
between the words high pressure and non-condensing, so that these terms
are considered to be virtually synonymous; and since Watt's great
contribution consisted of an application of the idea of condensation,
he was perhaps rendered antagonistic to the idea of high pressure,
through this psychological suggestion. In any event, the antagonism
unquestionably existed in his mind; though it has often enough been
pointed out that this seems the more curious since high-pressure steam
would so much better have facilitated the application of that other
famous idea of Watt, the use of the expansive property of steam.
Curiously enough, however, the influence of Watt led to experiments
in high-pressure steam through an indirect channel. The contemporary
inventor, Trevithick, in connection with his partner, Bull, had made
direct-acting pumping engines with an inverted cylinder, fixed in line
with the pump rod, and actually dispensing with the beam. But as these
engines used a jet of cold water in the exhaust pipe to condense the
steam, Boulton and Watt brought suit successfully for infringement of
their patent, and thus prevented Trevithick from experimenting further
in that direction. He was obliged, therefore, to turn his attention to
a different method, and probably, in part at least, in this way was
led to introduce the non-condensing, relatively high-pressure engine.
This was used about the year 1800. At the same time somewhat similar
experiments were made by Oliver Evans in America.
Both Trevithick and Evans applied their engines to the propulsion of
road vehicles; and Trevithick is credited with being the first man
who ran a steam locomotive on a track,--a feat which he accomplished
as early as the year 1804. We are not here concerned with the details
of this accomplishment, which will demand our attention in a later
chapter, when we come to discuss the entire subject of locomotive
transportation. But it is interesting to recall that the possibilities
of the steam engine were thus early realized, even though another
generation elapsed before they were finally demonstrated to the
satisfaction of the public. It is particularly interesting to note that
in his first locomotive engine, Trevithick allowed the steam exhaust
to escape into the funnel of the engine to increase the draught,--an
expedient which was so largely responsible for Stephenson's success
with his locomotive twenty years later, and which retains its utility
in the case of the most highly developed modern locomotive.
Trevithick was, however, entirely subordinated by the great
influence of Watt, and the use of high pressure was in consequence
discountenanced by the leading mechanical engineers of England for some
decades. Meantime, in America, the initiative of Evans led to a much
earlier general use of high-pressure steam. In due course, however, the
advantages of steam under high pressure became evident to engineers
everywhere, and its conquest was finally complete.
The essential feature of super-heated steam is that it contains, as
the name implies, an excess of heat beyond the quantity necessary to
produce mere vaporization, and that the amount of water represented
in this vapor is not the maximum possible under given conditions. In
other words, the vapor is not saturated. It has been already explained
that the amount of vapor that can be taken up in a given space under a
given pressure varies with the temperature of the space. Under normal
conditions, when a closed space exists above a liquid, evaporation
occurs from the surface of the liquid until the space is saturated,
and no further evaporation can occur so long as the temperature and
pressure are unchanged. If now the same space is heated to a higher
degree, more vapor will be taken up until again the point of saturation
is attained. But, obviously, if the space were disconnected with the
liquid, and then heated, it would acquire a capacity to take up more
vapor, and so long as this capacity was latent, the vapor present would
exist in a super-heated condition.
[Illustration: OLD IDEAS AND NEW APPLIED TO BOILER CONSTRUCTION.
The lower figure shows Robert Trevithick's famous boiler, used in
operating his locomotive about the year 1804. The original is preserved
in the South Kensington Museum, London. The upper figure shows a modern
tubular boiler, by way of contrast.]
It will be understood from what has been said before, that with all
accessions of heat, the expansive power of the vapor is increased,--its
molecules becoming increasingly active; hence one of the very obvious
advantages of super-heated steam for the purpose of pushing a piston.
There are other advantages, however, which are not at first sight
so apparent, having to do with the properties of condensation. To
understand these, we must pay heed for a few moments to the changes
that take place in steam itself in the course of its passage through
the cylinder, where it performs its work upon the piston.
Many of these changes were not fully understood by the earlier
experimenters, including Watt. Indeed the theory of the steam engine,
or rather the general theory of the heat engine, was not worked out
until the year 1824, when the Frenchman Carnot took the subject in
hand, and performed a series of classical experiments, which led to a
nearly complete theoretical exposition of the subject. It remained,
however, for the students of thermo-dynamics, about the middle of the
nineteenth century, with Clausius and Rankine at their head, to perfect
the theory of the steam engine, and the general subject of the mutual
relations of heat and mechanical work.
We are not here concerned with any elaboration of details, but merely
with a few of the essential principles which enter practically into
the operation of the steam engine. It appears, then, that when steam
enters the cylinder and begins to thrust back the piston of the steam
engine, a portion of the steam is immediately condensed on the walls
of the cylinder, owing to the fact that previous condensation of steam
has cooled these walls to a certain extent. We have already pointed
out that Watt endeavored in his earlier experiments to overcome this
difficulty, by equalizing the temperature of the cylinder walls to the
greatest practicable extent.
Notwithstanding his efforts, however, and those of numberless later
experimenters, it still remains true that under ordinary conditions,
particularly if steam enters the cylinder at the saturation point,
a very considerable condensation occurs. Indeed this may amount to
from thirty to fifty per cent. of the entire bulk of water contained
in the quantity of steam that enters the cylinder. This condensation
obviously militates against the expansive or working power of the
steam. But now as the steam expands, pushing forward the cylinder, it
becomes correspondingly rarefied, and immediately a portion of the
condensed steam becomes again vaporized, and in so doing it takes up
a certain amount of heat and renders it latent. This disadvantageous
cycle of molecular transformations is very much modified in the case of
super-heated steam, for the obvious reason that such steam may be very
much below the saturation point, and hence requires a very much greater
lowering of temperature in order to produce condensation of any portion
of its mass. Without elaborating details, it suffices to note that in
all highly efficient modern engines, steam is employed at a relatively
high pressure, and that sometimes this pressure becomes enormous.
COMPOUND ENGINES
As to the compound engine, that also, as has been pointed out, was
invented by a contemporary of Watt, Jonathan Hornblower by name, whose
patent bears date of 1781. In Hornblower's engine, steam was first
admitted to a small cylinder, and then, after performing its work on
the piston, was allowed to escape, not into a condensing receptacle,
but into a larger cylinder where it performed further work upon another
piston. This was obviously an instance of the use of steam expansively,
and it has been pointed out that, in consequence, Hornblower was
the first to make use of this idea in practise, although it is said
that Watt's experiments had even at that time covered this field.
The application of the idea to the movement of the second cylinder,
however, appears to have been original with Hornblower. Certainly it
owed nothing to Watt, who refused to accept the idea, and continued
throughout his life to frown upon the compound engine.
Nevertheless, the device had great utility, as subsequent experiments
were very fully to demonstrate. The compound engine was revived by
Woolf in 1804, and his name rather than Hornblower's is commonly
associated with it. The latter experimenter demonstrated that the
compound engine has two important merits as against the simple engine.
One of these is that the sum of the two forces exerted by the joint
action results in a more even and continuous pressure throughout the
cycle than could be accomplished by the action of a single cylinder.
To understand this it must be recalled that when using the expansive
property of steam, the piston thrust could not possibly be uniform,
since the greatest pressure exerted by the steam would be exerted at
the moment before it was shut off from the boiler, and its pressure
must then decrease progressively, as it exerts more and more work upon
the piston and becomes more expanded, thus obviously retaining less
elastic energy. The operation of the fly-wheel largely compensates
this difference of pressure in practise, but it would be obviously
advantageous could the pressure be equalized; and, as just stated, the
compound engine tends to produce this result.
The second, and perhaps the more important merit of the compound
engine is, that it is found in practise to keep the cylinders at a
more uniform temperature. A moment's reflection makes it clear why
this should be the case, since in a single-cylinder engine the exhaust
connects with the cool condenser, whereas in the compound engine the
exhaust from the first cylinder connects with the second cylinder at
only slightly lower temperature.
In many modern engines a third cylinder and sometimes even a fourth
is added, constituting what are called respectively triple-expansion
and quadruple-expansion engines. The triple-expansion system is very
generally employed, especially where it is peculiarly desirable to
economize fuel, as, for example, in the case of ships.
[Illustration: COMPOUND ENGINES.
The lower figure illustrates the use of a modern compound engine,
directly operating the propeller shaft of a steamship. The middle
figure shows a similarly direct application of power to the axes of
paddle wheels. The upper figure shows the application of power through
a walking beam similar in principle to that of the original Newcomen
and Watt engines.]
ROTARY ENGINES
All these improvements, it will be observed, have to do with details
that do not greatly modify the steam engine from the original type. The
cylinder with its closely fitting piston, as introduced in the Newcomen
engine, is retained and constitutes the essential mechanism through
which the energy of steam is transferred into mechanical energy. But
from a comparatively remote period the idea has prevailed that it might
be possible to utilize a different principle; that, in short, if the
steam instead of being made to press against a piston were allowed
to rush against fan-like blades, adjusted to an axle, it might cause
blades and axle to revolve, precisely as a windmill is made to revolve
by the pressure of the wind, or the turbine wheel by the pressure of
water.
In a word, it has been believed that a turbine engine might be
constructed, which would utilize the energy of the steam as
advantageously as it is utilized in the piston engine, and at the same
time would communicate its power as a direct rotation, instead of as a
straight thrust that must be translated into a rotary motion by means
of a crank or other mechanism.
In point of fact, James Watt himself invented such an engine, and
patented it in 1782, though there is no evidence that he ever
constructed even a working model. His patent specifications show "a
piston in the form of a closely-fitting radial arm, projecting from an
axial shaft in a cylinder. An abutment, arranged as a flap is hinged
near a recess in the side of the cylinder, and swings while remaining
in contact with the piston. Steam is admitted to the chamber on one
side of the flap, and so causes an unbalanced pressure upon the radial
arm."
This arrangement has been re-invented several times. Essentially the
same principle is utilized by Joshua Routledge, whose name is well
known in connection with the engineer's slide-rule. A model of this
engine is preserved in the South Kensington Museum, and the apparatus
is described in the catalogue of the Museum as follows:
"The piston revolves on a shaft passing through the centre of the
cylinder casing. The flap or valve hinged to the casing, with its free
end resting upon the piston, acts like the bottom of an ordinary engine
cylinder. The steam inlet port is on one side of the hinge, and the
exhaust port on the other. The admission of steam is controlled by a
side valve, actuated by an eccentric on the fly-wheel shaft, so that
the engine could work expansively, and the steam pressure resisting the
lifting of the flap would also be greatly reduced, so diminishing the
knock at this point, which, however, would always be a serious cause
of trouble. The exhaust steam passes down to a jet condenser, provided
with a supply of water from a containing tank, from which the injection
is admitted through a regulating valve. The air pump, which draws the
air and water from the condenser and discharges them through a pipe
passing out at the end of the tank, is a rotary machine constructed
like the engine and driven by spur gearing from the fly-wheel shaft.
Some efforts have been made to prevent leakage by forming grooves in
the sides of the revolving piston and filling them with soft packing."
Sundry other rotary engines, some of them actual working models, are
to be seen at the South Kensington Museum. There is, for example, one
invented by the Rev. Patrick Bell, a gentleman otherwise known to fame
as one of the earliest inventors of a practical reaping machine. In
this apparatus, "A metal disc is secured to a horizontal axis carried
in bearings, and the lower half of the disc is enclosed by a chamber
of circular section having its axis a semi-circle. One end of this
chamber is closed and provided with a pipe through which steam enters,
the exhaust taking place through the open end. The disc is provided
with three holes, each fitted with a circular plate turning on an
axis radial to the disc, and these plates when set at right angles
to the disc become pistons in the lower enclosing chamber. Toothed
gearing is arranged to rotate these pistons into the plane of the disc
on leaving the cylinder and back again immediately after entering,
locking levers retaining them in position during the intervals. The
steam pressure upon these pistons forces the disc round, but the engine
is non-expansive, and although some provision for packing has been
made, the leakage must have been considerable and the wear and tear
excessive."
It is stated that almost the same arrangement was proposed by Lord
Armstrong in 1838 as a water motor, and that a model subsequently
constructed gave over five horse-power at thirty revolutions per
minute, with an efficiency of ninety-five per cent.
Another working model of a rotary engine shown at the Museum is one
loaned by Messrs. Fielding and Platt in 1888. "The action of this
engine depends upon the oscillating motion which the cross of a
universal joint has relative to the containing jaws when the system is
rotated.
"Two shafts are set at an angle of 165 deg. to each other and connected
by a Hooke's joint; one serves as a pivot, the power being taken from
the other. Four curved pistons are arranged on the cross-piece, two
pointing towards one shaft and two towards the other, and on each
shaft or jaw are formed two curved steam cylinders in which the curved
pistons work. The steam enters and leaves the base of each cylinder
through ports in the shaft, which forms a cylindrical valve working in
the bearing as a seating.
"On the revolution of the shafts the pistons reciprocate in their
cylinders in much the same way as in an ordinary engine, and the
valve arrangement is such that while each piston is receding from its
cylinder the steam pressure is driving it, and during the in-stroke
of each, its cylinder is in communication with the exhaust. There are
thus four single-acting cylinders making each a double stroke for one
revolution of the driving-shaft. The engine has no dead centres, and
has been at 1,000 revolutions per minute."
[Illustration: ROTARY ENGINES.
The three types of rotary engines here shown are similar in principle,
and none of them is of great practical value, though the upper figure
shows an engine that has met with a certain measure of commercial
success.]
It is not necessary to describe other of the rotary engines that have
been made along more or less similar lines by numerous inventors,
models of which are for the most part, as in the case of those just
described, to be seen more commonly in museums than in practical
workshops. Reference may be made, however, to a rotary engine
which was invented by a Mr. Hoffman, of Buffalo, New York, about the
beginning of the twentieth century, an example of which was put into
actual operation in running the machinery of a shop in Buffalo, in 1905.
This engine consists of a solid elliptical shaft of steel, fastened to
an axle at one side of its centre, which axis is also the shaft of the
cylinder, which revolves about the central ellipse in such a way that
at one part of the revolution the cylinder surface fits tightly against
the ellipse, while the opposite side of the cylinder supplies a free
chamber between the ellipse and the cylinder walls. Running the length
of the cylinder are two curved pieces of steel, like longitudinal
sections of a tube. These flanges are adjusted at opposite sides of
the cylinder and so arranged that their sides at all times press
against the ellipse, alternately retreating into the substance of the
cylinder, and coming out into the free chamber. Steam is admitted to
the free chamber through one end of the shaft of ellipse and cylinder
and exhausted through the other end. The pressure of the steam against
first one end and then the other of the flanges supplies the motive
power. This pressure acts always in one direction, and the entire
apparatus revolves, the cylinder, however, revolving more rapidly than
the central ellipse.
For this engine the extravagant claim is made that there is no limit
to its speed of revolution, within the limit of resistance of steel
to centrifugal force. It has been estimated that a locomotive might
be made to run two hundred or three hundred miles an hour without
difficulty, with the Hoffman engine. Such estimates, however, are
theoretical, and it remains to be seen what the engine can do in
practise when applied to a variety of tasks, and what are its
limitations. Certainly the apparatus is at once ingenious and simple in
principle, and there is no obvious theoretical reason why it should not
have an important future.
TURBINE ENGINES
Whatever the future may hold, however, it remains true that the first
practical solution of the problem of securing direct rotary motion from
the action of steam, on a really commercial scale, was solved with an
apparatus very different from any of those just described, the inventor
being an Englishman, Mr. C. A. Parsons, and the apparatus the steam
turbine, the first model of which he constructed in 1884, and which
began to attract general attention in the course of the ensuing decade.
Public interest was fully aroused in 1897, when Mr. Parson's boat, the
_Turbinia_, equipped with engines of this type, showed a trial speed
of 32-3/4 knots per hour, a speed never hitherto attained by any other
species of water craft. More recently, a torpedo boat, the _Viper_,
equipped with engines developing about ten thousand horse-power,
attained a speed of 35-1/2 knots. The success of these small boats led
to the equipment of large vessels with the turbine, and on April first,
1905, the first transatlantic liner propelled by this form of engine
steamed into the harbor of Halifax, Nova Scotia.
This first ocean liner equipped with the turbine engine is called the
_Victorian_. She is a ship five hundred and forty feet long and sixty
feet wide, carrying fifteen hundred passengers. The _Victorian_ had
shown a speed of 19-1/2 knots an hour on her trial trip, and it had
been hoped that she would break the transatlantic record. On her first
trip, however, she encountered adverse winds and seas, and did not
attain great speed. Her performance was, however, considered entirely
satisfactory and creditable.
In the ensuing half-decade several large ships were equipped with
engines of the same type, the most famous of these being the Cunard
liners, _Carmania_, _Lusitania_, and _Mauretania_. The two last-named
ships are sister craft, and they are the largest boats of any kind
hitherto constructed. The _Lusitania_ was first launched and she
entered immediately upon a record-breaking career, only to be surpassed
within a few months by the _Mauretania_, which soon acquired all
records for speed and endurance.
Fuller details as to the performance of these vessels will be found in
another place. Here we are of course concerned with the Parsons turbine
engine itself rather than with its applications.
This turbine engine constitutes the first really important departure
from the old-type steam engine, thus realizing the dream of the
seventeenth-century Italian, Branca, to which reference was made
above. Mr. Parsons' elaboration of the idea developed a good deal of
complexity as regards the number of parts involved, yet his engine
is of the utmost simplicity in principle. It consists of a large
number of series of small blades, each series arranged about a drum
which revolves. Between the rings of revolving blades are adjusted
corresponding rings of fixed blades, which project from the casing
to the cylinder, and by means of which the steam is regulated in
direction, so that it strikes at the proper angle against the revolving
blades of the turbine.
In practise, three series of cylindrical drums are used, each
containing a large number of rings of blades of uniform size; but each
successive drum having longer blades, to accommodate the greater volume
of the expanding steam. The steam is fed against the first series of
blades in gusts, which may be varied in frequency and length to meet
the requirements of speed. After impinging on the first circle of
blades, the steam passes to the next under slightly reduced pressure,
and the pressure is thus successively stepped down from one set of
blades to another until it is ultimately reduced from say two hundred
pounds to the square inch, to one pound to the square inch before it
passes to the condenser and ceases to act.
There is thus a fuller utilization of the kinetic energy of the gas,
through carrying it from high to low pressure, than is possible with
the old type of cylinder-and-piston engine. On the other hand, there is
a constant loss due to the fact that the blades of the turbine can not
fit with absolute tightness against the cylinder walls. The net result
is that the compound turbine, as at present developed, appears to have
about the same efficiency as the best engine of the old type.
One capital advantage of the turbine is that it keeps the cylinder
walls at a more uniform temperature than is possible even with a
compound engine of the old type. Another advantage is that the power
of the turbine is applied directly to cause rotation of the shaft,
whereas no satisfactory means has ever been discovered hitherto of
making the action of the steam engine rotary, except with the somewhat
disadvantageous crank-shaft. This fact of adjustment of the turbine
blades to the revolving shaft seems to make this form of engine
particularly adapted to use in steamships. It is also highly adapted
to revolving the shaft of a dynamo, and has been largely applied to
this use. Needless to say, however, it may be applied to any other
form of machinery. It would be difficult at the present stage of
its development to predict the extent to which the turbine will
ultimately supersede the old type of engine. Its progress has already
been extraordinary, however, as an engineer pointed out in the London
_Times_ of August 14, 1907, in the following words:
"When the steam turbine was introduced by Mr. Parsons some 25 years
ago, in the form of a little model, which is now in the South
Kensington Museum, and the rotor of which may easily be held stationary
by the hand against the full blast of the steam, who would have been
rash enough to predict, except perhaps the far-seeing inventor himself,
that a vessel 760 feet long, loaded to 37,000 tons displacement,
drawing 32 ft. 9 in. of water, and providing accommodation for 2,500
people, could be propelled at a speed of 24.5 knots per hour, which it
is hoped she may maintain over the 3,000 miles of the Atlantic voyage?
"From this small model, which will in time become as historic as the
_Rocket_ of Stephenson, and which is only some few inches in diameter,
the turbine has been developed gradually in size. The cylindrical
casings which take the place of the complicated machinery of the
piston engine in the engine room of the _Lusitania_ contain drums,
which in the high-pressure turbines are 8 feet in diameter and in the
low-pressure 11 ft. 8 in., and from which thousands of curved blades
project, the longest of which are 22 inches, and against which the
steam impinges in its course from the boiler to the condenser.
"Not only has the steam turbine justified the confidence of those who
have labored so successfully in its development, but no other great
invention has proceeded from the laboratory stage to such an important
position in the engineering world in such a short space of time. This
would not have happened if some inherent drawback, such as lack of
economy in steam consumption, existed, and as the turbine has been
proved to be, for land purposes, very economical, there seems to be
no reason to doubt that marine turbines, working as they do at full
load almost continually, will show likewise that the coal bill is not
increased, but perhaps diminished by their use.
"The records of the vibrations of the hull which were taken during the
trials by Schlick's instruments showed that the vertical vibration
was 60 per minute on the run, which was due to the propellers, and
which may be further modified. The horizontal vibration was almost
unnoticeable, while the behavior of the ship in the heavy seas she
encountered in her long-distance runs was good, the roll from side to
side having a period of 18 seconds. The great length of this ship and
the gyrostatic action of the heavy rotating masses of the machinery
ought to render her almost insensible to the heaviest Atlantic rollers;
certainly as far as pitching is concerned."
[Illustration: THE ORIGINAL PARSON'S TURBINE ENGINE AND THE
RECORD-BREAKING SHIP FOR WHICH IT IS RESPONSIBLE.
This small turbine engine, with which Mr. Parson's early experiments
were made in 1884, is preserved in the South Kensington Museum, London.
At the time when it was made it seemed scarcely more than a toy, and
engineers in general doubted that the principle it employed could ever
be made commercially available. Yet within the lifetime of its inventor
engines built on this model have come to be the most powerful of force
transmuters. The "Mauretania," the largest, and thanks to her turbine
engines the speediest, of ships, is here presented on the same page
with the little original turbine model, as illustrating vividly the
practical development of a seemingly visionary idea.]
A more general comment upon the turbine engine, with particular
reference to its use in America, is made by Mr. Edward H. Sanborn in an
article on _Motive Power Appliances_, in the Twelfth Census Report of
the United States, Vol. X. part IV.
"Apart from its demonstrated economy," says Mr. Sanborn, "other
important advantages are claimed for the steam turbine, some of which
are worthy of brief mention.
"There is an obvious advantage in economy of space as compared with
the reciprocating engine. The largest steam turbine constructed in the
United States is one of 3,000 horse-power, which is installed in the
power house of the Hartford Electric Light Company, Hartford, Conn. The
total weight of this motor is 28,000 pounds, its length over all is 19
feet 8 inches, and its greatest diameter six feet. With the generator
to which it is directly connected, it occupies a floor space of 33 feet
3 inches long by 8 feet 9 inches wide.
"Friction is reduced to a minimum in the steam turbine, owing to the
absence of sliding parts and the small number of bearings. The absence
of internal lubrication is also an important consideration, especially
when it is desired to use condensers.
"As there are no reciprocating parts in a steam turbine, and as a
perfect balance of its rotating parts is absolutely essential to its
successful operation, vibration is reduced to such a small element that
the simplest foundations will suffice, and it is safe to locate steam
turbines on upper floors of a factory if this be desirable or necessary.
"The perfect balance of the moving parts and the extreme simplicity
of construction tend to minimize the wear and increase the life of a
turbine, and at the same time to reduce the chance of interruption
in its operation through derangement of, or damage to, any of its
essential parts.
"Although hardly beyond the stage of its first advent in the
motive-power field, the steam turbine has met with much favor, and
there is promise of its wide use for the purposes to which it is
particularly adapted. At present, however, its uses are restricted to
service that is continuous and regular, its particular adaptability
being for the driving of electrical generators, pumps, ventilating
fans, and similar work, especially where starting under load is not
essential.
"Steam turbines are now being built in the United States in all sizes
up to 3,000 horse-power. Their use abroad covers a longer period and
has become more general. The largest turbines thus far attempted
are those of the Metropolitan District Electric Traction Company,
of London, embracing four units of 10,000 horse-power each. Several
turbines of large size have been operated successfully in Germany."
It should be added that the compound turbine wheel of Parsons is not
the only turbine wheel that has proved commercially valuable. There
is a turbine consisting of a single ring of revolving blades, the
invention of Dr. Gustav De Laval, which has proved itself capable of
competing with the old type of engine. To make this form of single
turbine operate satisfactorily, it is necessary to have steam under
high pressure, and to generate a very high speed of revolution. In
practice, the De Laval machines sometimes attain a speed of thirty
thousand revolutions per minute. This is a much higher rate of speed
than can advantageously be utilized directly in ordinary machinery, and
consequently the shaft of this machine is geared to another shaft in
such a way as to cause the second shaft to revolve much more slowly.
VII
GAS AND OIL ENGINES
Just at the time when the type of piston-and-cylinder engine has thus
been challenged, it has chanced that a new motive power has been
applied to the old type of engine, through the medium of heated gas.
The idea of such utilization of a gas other than water vapor is by no
means new, but there have been practical difficulties in the way of the
construction of a commercial engine to make use of the expansive power
of ordinary gases.
The principle involved is based on the familiar fact that a gas expands
on being heated and contracts when cool. Theoretically, then, all that
is necessary is to heat a portion of air confined in a cylinder, to
secure the advantage of its expansion, precisely as the expansion of
steam is utilized, by thrusting forward a piston. Such an apparatus
constitutes a so-called "caloric" or hot-air engine. As long ago
as the year 1807 Sir G. Cayley in England produced a motor of this
type, in which the heated air passed directly from the furnace to the
cylinder, where it did work while expanding until its pressure was not
greater than that of the atmosphere, when it was discharged. The chief
mechanical difficulty encountered resulted from the necessity for the
employment of very high temperatures; and for a long time the engine
had no great commercial utility. The idea was revived, however, about
three-quarters of a century later and an engine operated on Cayley's
principle was commercially introduced in England by Mr. Buckett. This
engine has a cold-air cylinder above the crank-shaft and a large
hot-air cylinder below, while the furnace is on one side enclosed in an
air-tight chamber. The fuel is supplied as required through a valve and
distributing cone arranged above the furnace and provided with an air
lock in which the fuel is stored. At about the time when this hot-air
engine was introduced, however, gas and oil engines of another and more
important type were developed, as we shall see in a moment.
Meantime, an interesting effort to utilize the expansive property of
heated air was made by Dr. Stirling in 1826; his engine being one
in which heat was distributed by means of a displacer which moved
the mass of air to and fro between the hot and cold portions of the
apparatus. He also compressed the air before heating it, thus making a
distinct advance in the economy and compactness of the engine. From an
engineering standpoint his design has further interest in that it was
a practical attempt to construct an engine working on the principle
of the theoretically perfect heat engine, in which the cycle of
operations is closed, the same mass of air being used throughout. In
the theoretically perfect heat engine, it may be added, the cycle of
operations may be reversed, there being no loss of energy involved; but
in practice, of course, an engine cannot be constructed to meet this
ideal condition, as there is necessarily some loss through dissipation
of heat. Dr. Stirling's practical engine had its uses, but could not
compete with the steam engine in the general field of mechanical
operations to which that apparatus is applied.
Another important practical experimenter in the construction of
hot-air engines was John Ericsson, who in 1824 constructed an engine
somewhat resembling the early one of Cayley, and in 1852 built caloric
engines on such a scale as to be adapted to the propulsion of ships.
Notwithstanding the genius of Ericsson, however, engines of this
type did not prove commercially successful on a large scale, and
in subsequent decades the hot-air motors constructed for practical
purposes seldom exceeded one horse-power. Such small engines as
these are comparatively efficient and absolutely safe, and they are
thoroughly adapted for such domestic purposes as light pumping.
The great difficulty with all these engines operated with heated air
has been, as already suggested, that their efficiency of action is
limited by the difficulties incident to applying high temperatures
to large masses of the gas. There is, however, no objection to the
super-heating of small quantities of gas, and it was early suggested
that this might be accomplished by exploding a gaseous mixture
within a cylinder. It was observed by the experimenters of the
seventeenth century that an ordinary gun constitutes virtually an
internal-combustion engine; and such experimenters as the Dutchman
Huyghens, and the Frenchmen Hautefeuille and Papin, attempted to make
practical use of the power set free by the explosion of gunpowder,
their experiments being conducted about the years 1678 to 1689.
Their results, however, were not such as to give them other than an
historical interest. About a century later, in 1794, the Englishman
Robert Street suggested the use of inflammable gases as explosives, and
ever since that time there have been occasional experimenters along
that line. In 1823 Samuel Brown introduced a vacuum gas engine for
raising water by atmospheric pressure. The first fairly practical gas
engine, however, was that introduced by J. J. E. Lenoir, who in 1850
proposed an engine working with a cycle resembling that of a steam
engine. His engine patented in 1860 proved to be a fairly successful
apparatus. This engine of Lenoir prepared the way for gas engines that
have since become so enormously important. Its method of action is this:
"To start the engine, the fly-wheel is pulled round, thus moving the
piston, which draws into the cylinder a mixture of gas and air through
about half its stroke; the mixture is then exploded by an electric
spark, and propels the piston to the end of its stroke, the pressure
meanwhile falling, by cooling and expansion, to that of the atmosphere
when exhaust takes place. In the return stroke the process is repeated,
the action of the engine resembling that of the double-acting steam
engine, and having a one-stroke cycle. The cylinder and covers are
cooled by circulating water. The firing electricity was supplied by two
Bunsen batteries and an induction coil, the circuit being completed at
the right intervals by contact pieces on an insulating disc on the
crank-shaft; the ignition spark leaped across the space between two
wires carried about one-sixth of an inch apart in a porcelain holder."
In 1865 Mons. P. Hugon patented an engine similar to that of Lenoir,
except that ignition was accomplished by an external flame instead of
by electricity. The ignition flame was carried to and fro in a cavity
inside a slide valve, moved by a cam so as to get a rapid cut-off, and
permanent lights were maintained at the ends of the valve to re-light
the flame-ports after each explosion. The gas was supplied to the
cylinder by rubber bellows, worked by an eccentric on the crank-shaft.
This engine could be operated satisfactorily, except as to cost, but
the heavy gas consumption made it uneconomical.
An important improvement in this regard was introduced by the Germans,
Herrn. E. Langen and N. A. Otto, who under patents bearing date of
1866 introduced a so-called "free" piston arrangement--that is to say
an arrangement by which the piston depends for its action partly upon
the momentum of a fly-wheel. This principle had been proposed for a
gas engine as early as 1857, but the first machine to demonstrate its
feasibility was that of Langen and Otto. Their engine greatly decreased
the gas consumption and hence came to be regarded as the first
commercially successful gas engine. It was, however, noisy and limited
to small sizes. The cycle of operations of an engine of this type is
described as follows:
[Illustration: GAS AND OIL ENGINES.
Lower right-hand figure, a very early type of commercially successful
gas engine. It has a "free" piston, an arrangement that was first
proposed for a gas engine in 1857, but only brought into practical form
by Langen & Otto under their patent of 1866. Upper figure, the gas
engine patented by Lenoir in 1860, one of the very first practically
successful engines. Lower left-hand figure, a sectional view of a
modern gas engine of the type used as the motor of the automobile.]
"(a) The piston is lifted about one-tenth of its travel by the momentum
of the fly-wheel, thus drawing in a charge of gas and air.
"(b) The charge is ignited by flame carried in by a slide valve.
"(c) Under the impulse of the explosion, the piston shoots upward
nearly to the top of the cylinder, the pressure in which falls by
expansion to about 4 lbs. absolute, while absorbing the energy of the
piston.
"(d) The piston descends by its own weight and the atmospheric
pressure, and in doing so causes a roller-clutch on a spur-wheel
gearing with a rack on the piston-rod to engage, so that the fly-wheel
shaft shall be driven by the piston; during this down-stroke the
pressure increases from 4 lbs. absolute to that of the atmosphere, and
averages 7 lbs. per square inch effective throughout the stroke.
"(e) When the piston is near the bottom of the cylinder, the pressure
rises above atmospheric, and the stroke is completed by the weight of
the piston and rack, and the products of combustion are expelled.
"(f) The fly-wheel now continues running freely till its speed, as
determined by a centrifugal governor, falls below a certain limit when
a trip gear causes the piston to be lifted the short distance required
to recommence the cycle.
"Ignition is performed by an external gas jet, near a pocket in the
slide valve by which the charge is admitted; this pocket carries flame
to the charge, thus igniting it without allowing any escape. The valve
also connects the interior of the cylinder with the exhaust pipe,
and a valve in the latter controlled by the governor throttles the
discharge, and so defers the next stroke until the speed has fallen
below normal. To run the engine empty about four explosions per minute
are necessary, and at full power 30 to 35 are made, so that about 28
explosions per minute are available for useful work under the control
of the governor."
The definitive improvement in this gas engine was introduced in 1876
by Dr. N. A. Otto, when he compressed the explosive mixture in the
working cylinder before igniting it. This expedient--so all-important
in its results--had been suggested by William Barnett in 1838, but at
that time gas engines were not sufficiently developed to make use of
the idea. Now, however, Dr. Otto demonstrated that by compressing the
gas before exploding it a much more diluted mixture can be fired, and
that this gives a quieter explosion, and a more sustained pressure
during the working stroke, while as the engine runs at a high speed the
fly-wheel action is generally sufficient to correct the fluctuations
arising from there being but one explosion for four strokes of the
piston.
In this perfected engine, then, the method of operation is as follows:
The piston is pulled forward with the application of some outside
force, which in practice is supplied by the inertia of the fly-wheel,
or in starting the engine by the action of a crank with which every
user of an automobile is familiar. In being pulled forward, the piston
draws gas into the cylinder; as the piston returns, this gas is
compressed; the compressed gas, constituting an explosive mixture, is
then ignited by a piece of incandescent metal or by an electric spark;
the exploding gas expands, pushing the piston forward, this being the
only thrust during which work is done; the returning piston expels the
expanded gas, completing the cycle. Thus there are three ineffective
piston thrusts to one effective thrust. Nevertheless, the engine has
proved a useful one for many purposes.
This so-called Otto cycle has been adopted in almost all gas and oil
engines, the later improvements being in the direction of still higher
compression, and in the substitution of lift for slide valves. There
has been a steady increase in the size and power of such engines, the
large ones usually introducing two or more working cylinders so as to
secure uniform driving. Cheap forms of gas have been employed such as
those made by decomposing water by incandescent fuel, and it has been
proved possible thus to operate gas-power plants on a commercial scale
in competition with the most economical steam installations.
A practical modification of vast importance was introduced when it
was suggested that a volatile oil be employed to supply the gas for
operation in an internal combustion engine. There was no new principle
involved in this idea, and the Otto cycle was still employed as
before; but the use of the volatile oil--either a petroleum product
or alcohol--made possible the compact portable engine with which
everyone is nowadays familiar through its use in automobiles and
motor boats. The oil commonly used is gasoline which is supplied to
the cylinder through a so-called carburettor in which the vapors of
gasoline are combined with ordinary air to make an explosive mixture.
The introduction of this now familiar type of motor is to a large
extent due to Herr G. Daimler, who in 1884 brought out a light and
compact high-speed oil engine. About ten years later Messrs. Panhard
and Levassor devised the form of motor which has since been generally
adopted. Few other forms of mechanisms are better known to the general
public than the oil engine with its two, four, six, or even eight
cylinders, as used in the modern automobile. As everyone is aware, it
furnishes the favorite type of motor, combining extraordinary power
with relative lightness, and making it feasible to carry fuel for a
long journey in a receptacle of small compass.
With the gas engines a complication arises precisely opposite to that
which is met with in the case of the cylinder of the steam engine--the
tendency, namely, to overheating of the cylinder. To obviate this it
is customary to have the cylinder surrounded by a water jacket, though
air cooling is used in certain types of machines. About fifty per cent.
of the total heat otherwise available is lost through this unavoidable
expedient.
The rapid introduction of the gas engine in recent years suggests that
this type of engine may have a most important future. It has even
been predicted that within a few years most trans-Atlantic steamers
will be equipped with this type of engine, producing their own gas
in transit. It is possible, then, that through this medium the old
piston-and-cylinder engine may retain its supremacy, as against the
turbine. For the moment, at any rate, the gas engine is gaining
popularity, not merely in its application to the automobile, but for
numerous types of small stationary engines as well.
In this connection it will be interesting to quote the report of the
Special Agent of the Twelfth Census of the United States, as showing
the status of gas engines and steam engines in the year 1902.
"The decade between 1890 and 1900," he says, "was a period of marked
development in the use of gas engines, using that term to denote all
forms of internal combustible engines, in which the propelling force
is the explosion of gaseous or vaporous fuel in direct contact with
a piston within a closed cylinder. This group embraces those engines
using ordinary illuminating gas, natural gas, and gas made in special
producers installed as a part of the power plant, and also vaporised
gasoline or kerosene. This form of power for the first time is an item
of consequence in the returns of the present census, and the very large
increase in the horse-power in 1900 as compared with 1890 indicates the
growing popularity of this class of motive power.
"In 1890 the number of gas engines in use in manufacturing plants
was not reported, but their total power amounted to only 8,930
horse-power, or one-tenth of one per cent of the total power utilized
in manufacturing operations. In 1900, however, 14,884 gas engines were
reported, with a total of 143,850 horse-power, or 1.3 per cent of the
total power used for manufacturing purposes. This increase from 8,930
horse-power to 143,850 horse-power, a gain of 134,920 horse-power, is
proportionately the largest increase in any form of primary power shown
by a comparison of the figures of the Eleventh and Twelfth censuses,
amounting to 1,510.9 per cent.
"Within the past decade, and more particularly during the past
five years, there has been a marked increase in the use of this
power in industrial establishments for driving machinery, for
generating electricity, and for other kindred uses. At the same time,
internal-combustion engines have increased in popularity for uses apart
from manufacturing, and the amount of this kind of power in use for all
purposes in 1900 was, doubtless, very much larger than indicated by the
figures relating to manufacturing plants alone.
"The average horse-power per gas engine in 1900 was 9.7 horse-power.
There are no available statistics upon which to base a comparison of
this average with the average for 1890, but it is doubtful if there
has been any very material change in ten years; for while gas engines
are built in much larger sizes than ever before, there has been also a
great increase in the number of small engines for various purposes.
"The large increase in the use of internal-combustion engines has
been due to the rapid improvements that have been made in them, their
increased efficiency and economy, their decreased cost, and the wider
range of adaptability that has been made practicable.
"Steam still continues to be preeminently the power of greatest
importance, and the census returns indicate that the proportion of
steam to the total of all powers has increased very largely in the past
thirty years. In 1870 steam furnished 1,215,711 horse-power, or 51.8
per cent of a total of 2,346,142; in 1880 the amount of steam power
used was 2,185,458 horse-power out of a total of 3,410,837, or 64.1 per
cent; in 1890 out of an aggregate of 5,954,655 horse-power, 4,581,595,
or 76.9 per cent was steam; while in 1900 steam figured to the extent
of 8,742,416 horse-power, or 77.4 per cent, in a total of 11,300,081.
This increase in thirty years, from 51.8 per cent to 77.4 per cent of
the total power, shows how much more rapidly the use of steam power has
increased than other primary sources of power.
"The tendency toward larger units in the use of steam power is shown
inadequately by the increase in the average horse-power per engine from
39 horse-power in 1880, to 51 horse-power in 1890, and 56 horse-power
in 1900.
"The tendency toward great operations which has been such a conspicuous
feature of industrial progress during the past ten years, has shown
itself strikingly in the use of units of larger capacity in nearly
every form of machinery, and nowhere has this tendency been more marked
than in the motive power by which the machinery is driven. At the same
time there has been an increase in the use of small units, which tends
to destroy the true tendency in steam engineering in these statistics.
For example, a steam plant consisting of one or more units of several
thousand horse-power may also embrace a number of small engines of
only a few horse-power each, the use of which is necessitated by the
magnitude of the plant, for the operation of mechanical stokers, the
driving of draft fans, coal and ash conveyors, and other work requiring
power in small units. On this account the average horse-power of steam
engines in use at different census periods fails to afford a true
basis for measuring progress toward larger units during the past ten
years.
"Developments of the past few years in the distribution of power by the
use of electric motors have served to accelerate the tendency toward
larger steam units and the elimination of small engines in large plants
and to change completely the conditions just described. For example:
In one of the largest power plants in the world, which is now being
installed, all the stokers, blowers, conveyors, and other auxiliary
machinery are to be driven by electric motors. Such rapidly changing
conditions tend to invalidate any comparisons of statistical averages
deduced from figures for periods even but a few years apart.
"Comparison of two important industries will illustrate the foregoing.
The average horse-power of the steam engine used in the cotton mills of
the United States in 1890 was 198, and in 1900 it was 300.
"In the iron and steel industry the average horse-power per engine in
1890 was 171, and in 1900 it was 235. In the cotton mills the use of
single large units of motive power, with few auxiliary engines of small
capacity, gives the largest horse-power per engine of any industry;
while in the iron and steel industry the average of the motive power
proper, although probably larger than in the manufacture of cotton
goods, is reduced by the large number of small engines which are used
for auxiliary purposes in every iron and steel plant."
It will be understood that the object of exploding the mixed gases in
the oil engine is to produce sudden heating of the entire gas. There
is no reason whatever for introducing the gasoline beyond this. Could
a better method of heating air be devised, the oil might be entirely
dispensed with, and the safety of the apparatus enhanced, as well as
the economy of operation. Efforts have been made for fifty years to
construct a hot-air engine that would compete with steam successfully.
In the early fifties, as already noted, Ericsson showed the feasibility
of substituting hot air for steam, but although he constructed large
engines, their power was so slight that he was obliged to give up the
idea of competing with steam, and to use his engines for pumping where
very small power was required.
The great difficulty was that it was not found practicable to heat
the air rapidly. All subsequent experimenters have met with the same
difficulty until somewhat recently. It is now claimed, however, that
a means has been found of rapidly heating the air, and it is even
predicted that the hot-air engine will in due course entirely supersede
the steam engine. Mr. G. Emil Hesse, in an article in _The American
Inventor_, for April 15, 1905, describes a Svea caloric engine as
having successfully solved the problem of rapidly heating air. The
methods consist in breaking up the air into thin layers and passing
it over hot plates, where it rapidly absorbs heat. It passes from the
heater to the power cylinder which resembles the cylinder of a steam
engine; thence after expanding and doing its work it is exhausted into
the atmosphere. Large engines may use the same air over and over again
under pressure of one hundred pounds per square inch, alternately
heating and cooling it. A six horse-power engine of this type is
said to have a cylinder four and one-half inches in diameter and a
stroke of four and seven-eighth inches, and makes four hundred and
fifty revolutions per minute. The heater is twenty inches in diameter,
sixteen inches long, and has a heating surface of sixty square feet.
The total weight of heater and engine complete is four hundred pounds
for a half horse-power Ericsson engine.
"The Svea heater," says Mr. Hesse, "absorbs the heat as perfectly
as an ordinary steam boiler, and the heat-radiating surface of both
heater and engine is not larger than that of a steam plant of the same
power, thereby placing the two motors on the same basis, as far as the
utilization of the heat in the fuel itself is concerned.
"The advantage which every hot-air engine has over the steam engine is
the amount of heat saved in the vaporization of the water. It is now
well known that one gas is as efficient as another for the conversion
of heat into power. Air and steam at 100° C. are consequently on the
same footing and ready to be superheated. The amount of heat required
to bring the two gases to this temperature is, however, very different.
"With an initial temperature of 10° C. for both air and water, we find
that one kilogram of steam requires 90 + 537 = 627 thermal units,
and one kilogram of air 0.24 × 90 = 21.6 thermal units. Some heat is
recovered if the feed water is heated and the steam condensed, but
the difference is still so great as to altogether exclude steam as a
competitor, provided air can be as readily handled.
"Having now the means to rapidly heat the air, the outlook for the
external-combustion engine is certainly very promising.
"The saving of more than half the coal now used by the steam engine
will be of tremendous importance to the whole world."
To what extent this optimistic prediction will be verified is a problem
for the future to decide.
VIII
THE SMALLEST WORKERS
In our studies of the steam engine and gas engine we have been
concerned with workers of infinitesimal size. Yet, if we are to believe
the reports of the modern investigator, the molecules of steam or of
ignited gas are small only in a relative sense, and there is a legion
of workers compared with which the molecules are really gigantic in
size. These workers are the atoms, and the yet more minute particles
of which, according to the most recent theories, they are themselves
composed.
These smallest conceivable particles, the constituents of the atoms,
are called electrons. They are a discovery of the physicists of the
most recent generation. According to the newest theories they account
for most--perhaps for all--of the inter-molecular and inter-atomic
forces; they are indeed the ultimate repositories of those stores of
energy which are known to be contained in all matter. The theories
are not quite as fully developed as could be wished, but it would
appear that these minutest particles, the electrons, are the essential
constituents of the familiar yet wonderful carrier of energy which
we term electricity. In considering the share of electricity in
the world's work, therefore, we shall do well at the outset to put
ourselves in touch with recent views as to the nature of this most
remarkable of workers.
On every side in this modern world we are confronted by this strange
agent, electricity. The word stares us in the face on every printed
page. The thing itself is manifest in all departments of our every-day
life. You go to your business in an electric car; ascend to your
office in an electric elevator; utilize electric call-bells; receive
and transmit messages about the world and beneath the sea by electric
telegraph. Your doctor treats you with an electric battery. Your
dentist employs electric drills and electric furnaces. You ride in
electric cabs; eat food cooked on electric stoves; and read with the
aid of electric light. In a word, the manifestations of electricity are
so obvious on every side that there can be no challenge to the phrasing
which has christened this the Age of Electricity.
But what, then, is this strange power that has produced all these
multifarious results? It would be hard to propound a scientific query
that has been more variously answered. Ever since the first primitive
man observed the strange effect produced by rubbing a piece of amber,
thoughtful minds must have striven to explain that effect. Ever since
the eighteenth-century scientist began his more elaborate studies of
electricity, theories in abundance have been propounded. And yet we
are not quite sure that even the science of to-day can give a correct
answer as to the nature of electricity. At the very least, however, it
is able to give some interesting suggestions which seem to show that
we are in a fair way to solve this world-old mystery. And, curiously
enough, the very newest explanations are not so very far away from
some eighteenth-century theories which for a long time were looked
at askance if not altogether discarded. In particular, the theory of
Benjamin Franklin, which considered electricity as an immaterial fluid
bearing certain curious relations to tangible matter, is found to serve
singularly well as an aid to the interpretation of the very newest
experiments.
FRANKLIN'S ONE-FLUID THEORY
Such being the case, we must consider this theory of Franklin's
somewhat in detail. Perhaps we cannot do better than state the theory
in the words of the celebrated physicist, Dr. Thomas Young, as given
in his work on natural philosophy, published in 1807. By quoting from
this old work we shall make sure that we are not reading any modern
interpretations into the theory. "It is supposed," says Young, "that a
peculiar ethereal fluid pervades the pores, if not the actual substance
of the earth and of all other material bodies, passing through them
with more or less facility, according to their different powers of
conducting it; that particles of this fluid repel each other, and are
attracted by particles of common matter; that particles of common
matter also repel each other; and that these attractions and repulsions
are equal among themselves, and vary inversely as to squares of the
distances of the particles. The effects of this fluid are distinguished
from those of all other substances by an attractive or repulsive
quality, which it appears to communicate to different bodies, and
which differs in general from other attractions and repulsions by
its immediate diminution or cessation when the bodies, acting on
each other, come into contact, or are touched by other bodies.... In
general, a body is said to be electrified when it contains, either as
a whole or in any of its parts, more or less of the electric fluid
than is natural to it.... In this common neutral state of all bodies,
the electrical fluid, which is everywhere present, is so distributed
that the various forces hold each other exactly in equilibrium and
the separate results are destroyed, unless we choose to consider
gravitation itself as arising from a comparatively slight inequality
between the electrical attractions and repulsions."
The salient and striking feature of this theory, it will be observed,
is that the electrical fluid, under normal conditions, is supposed to
be incorporated everywhere with the substance of every material in
the world. It will be observed that nothing whatever is postulated as
to the nature or properties of this fluid beyond the fact that its
particles repel each other and are attracted by the particles of common
matter; it being also postulated that the particles of common matter
likewise repel each other under normal conditions.
At the time when Franklin propounded his theory, there was a rival
theory before the world, which has continued more or less popular ever
since, and which is known as the two-fluid theory of electricity.
According to this theory, there are two uncreated and indestructible
fluids which produce electrical effects. One fluid may be called
positive, the other negative. The particles of the positive fluid are
mutually repellent, as also are the particles of the negative fluid,
but, on the other hand, positive particles attract and are attracted by
negative particles. We need not further elaborate the details of this
two-fluid theory, because the best modern opinion considers it less
satisfactory than Franklin's one-fluid theory. Meantime, it will be
observed that the two theories have much in common; in particular they
agree in the essential feature of postulating an invisible something
which is not matter, and which has strange properties of attraction and
repulsion.
These properties of attraction and repulsion constituted in the
early day the only known manifestations of electricity; and the same
properties continue to hold an important place in modern studies of
the subject. Electricity is so named simply because amber--the Latin
_electrum_--was the substance which, in the experience of the ancients,
showed most conspicuously the strange property of attracting small
bodies after being rubbed. Modern methods of developing electricity
are extremely diversified, and most of them are quite unsuggestive
of the rubbing of amber; yet nearly all the varied manifestations of
electricity are reducible, in the last analysis, to attractions and
repulsions among the particles of matter.
As to the alleged immaterial fluids which, according to the theories
just mentioned, make up the real substance of electricity, it was
perfectly natural that they should be invented by the physicists of the
elder day. All the conceptions of the human mind are developed through
contact with the material world; and it is extremely difficult to get
away, even in theory, from tangible realities. When the rubbed amber
acquires the property of drawing the pith ball to it, we naturally
assume that some change has taken place in the condition of the amber;
and since the visible particles of amber appear to be unchanged--since
its color, weight, and friability are unmodified--it seems as if some
immaterial quality must have been added to, or taken from it. And it
was natural for the eighteenth-century physicist to think of this
immaterial something as a fluid, because he was accustomed to think of
light, heat, and magnetism as being also immaterial fluids. He did not
know, as we now do, that what we call heat is merely the manifestation
of varying "modes" of motion among the particles of matter, and that
what we call light is not a thing _sui generis_, but is merely our
recognition of waves of certain length in the all-pervading ether.
The wave theory of light had, indeed, been propounded here and
there by a philosopher, but the theory which regarded light as a
corpuscular emanation had the support of no less an authority than
Sir Isaac Newton, and he was a bold theorist that dared challenge it.
When Franklin propounded his theory of electricity, therefore, his
assumption of the immaterial fluid was thoroughly in accord with the
physical doctrines of the time.
MODERN VIEWS
But about the beginning of the nineteenth century the doctrine
of imponderable fluids as applied to light and heat was actively
challenged by Young and Fresnel and by Count Rumford and Humphry Davy
and their followers, and in due course the new doctrines of light and
heat were thoroughly established. In the light of the new knowledge,
the theory of the electric fluid or fluids seemed, therefore, much
less plausible. Whereas the earlier physicists had merely disputed as
to whether we must assume the existence of two electrical fluids or
of only one, it now began to be questioned whether we need assume the
existence of any electrical fluid whatever. The physicists of about
the middle of the nineteenth century developed the wonderful doctrine
of conservation of energy, according to which one form of force may be
transformed into another, but without the possibility of adding to, or
subtracting from, the original sum total of energy in the universe.
It became evident that electrical force must conform to this law.
Finally, Clerk-Maxwell developed his wonderful electromagnetic theory,
according to which waves of light are of electrical origin. The work of
Maxwell was followed up by the German Hertz, whose experiments produced
those electromagnetic waves which, differing in no respect except in
their length from the waves of light, have become familiar to everyone
through their use in wireless telegraphy. All these experiments showed
a close relation between electrical phenomena, and the phenomena of
light and of radiant heat, and a long step seemed to be taken toward
the explanation of the nature of electricity.
The new studies associated electricity with the ether, rather than with
the material substance of the electrified body. Many experiments seemed
to show that electricity in motion traverses chiefly the surface of
the conductor, and it came to be believed that the essential feature of
the "current" consists of a condition of strain or stress in the ether
surrounding a conductor, rather than of any change in the conductor
itself. This idea, which is still considered valid, has the merit of
doing away with the thought of action at a distance--the idea that was
so repugnant to the mind of Faraday.
So far so good. But what determines the ether strain? There is
surely _something_ that is not matter and is not ether. What is this
something? The efforts of many of the most distinguished experimenters
have in recent years been directed toward the solution of that
question; and these efforts, thanks to the new methods and new
discoveries, have met with a considerable measure of success. I must
not attempt here to follow out the channels of discovery, but must
content myself with stating briefly the results. We shall have occasion
to consider some further details as to the methods in a later chapter.
Briefly, then, it is now generally accepted, at least as a working
hypothesis, that every atom of matter--be it oxygen, hydrogen, gold,
iron, or what not--carries a charge of electricity, which is probably
responsible for all the phenomena that the atom manifests. This charge
of electricity may be positive or negative, or it may be neutral, by
which is meant that the positive and negative charges may just balance.
If the positive charge has definite carriers, these are unknown except
in association with the atom itself; but the negative charge, on the
other hand, is carried by minute particles to which the name electron
(or corpuscle) has been given, each of which is about one thousand
times smaller than a hydrogen atom, and each of which carries uniformly
a unit charge of negative electricity.
Electrons are combined, in what may be called planetary systems, in the
substance of the atom; indeed, it is not certain that the atom consists
of anything else but such combinations of electrons, held together
by the inscrutable force of positive electricity. Some, at least, of
the electrons within the atom are violently active--perhaps whirling
in planetary orbits,--and from time to time one or more electrons may
escape from the atomic system. In thus escaping an electron takes away
its charge of negative electricity, and the previously neutral atom
becomes positively electrified. Meanwhile the free electron may hurtle
about with its charge of negative electricity, or may combine with some
neutral atom and thus give to that neutral atom a negative charge.
Under certain conditions myriads of these electrons, escaped thus from
their atomic systems, may exist in the free state. For example, the
so-called _beta_ (ß) rays of radium and its allies consist of such
electrons, which are being hurtled off into space with approximately
the speed of light. The cathode rays, of which we have heard so much in
recent years, also consist of free electrons.
But, for that matter, all currents of electricity whatever, according
to this newest theory, consist simply of aggregations of free
electrons. According to theory, if the electrons are in uniform motion
they produce the phenomena of constant currents of electricity; if
they move non-uniformly they produce electromagnetic phenomena (for
example, the waves used in wireless telegraphy); if they move with
periodic motion they produce the waves of light. Meanwhile stationary
aggregations of electrons produce the so-called electrostatic
phenomena. All the various ether waves are thus believed to be produced
by changes in the motions of the electrons. A very sudden stoppage,
such as is produced when the cathode ray meets an impassable barrier,
produces the X-ray.
With these explanations in mind, it will be obvious how closely this
newest interpretation of electricity corresponds in its general
features with the old one-fluid theory of Franklin. The efforts of
the present-day physicist have resulted essentially in an analysis of
Franklin's fluid, which gives to this fluid an atomic structure. The
new theory takes a step beyond the old in suggesting the idea that
the same particles which make up the electric fluid enter also into
the composition--perhaps are the sole physical constituents--of every
material substance as well. But while the new theory thus extends
the bounds of our vision, we must not claim that it fully solves the
mystery. We can visualize the ultimate constituent of electricity as
an electron one thousand times smaller than the hydrogen atom, which
has mass and inertia, and which possesses powers of attraction and
repulsion. But as to the actual nature of this ultimate particle we are
still in the dark. There are, however, some interesting theories as to
its character, which should claim at least incidental attention.
We have all along spoken of the electron as an exceedingly minute
particle, stating indeed, that in actual size it is believed to be
about one thousand times smaller than the hydrogen atom, which hitherto
had been considered the smallest thing known to science. But we have
now to offer a seemingly paradoxical modification of this statement.
It is true that in _mass_ or weight the electron is a thousand times
smaller than the hydrogen atom, yet at the same time it may be
conceived that the limits of space which the electron occupies are
indefinitely large. In a word, it is conceived (by Professor J. J.
Thomson, who is the chief path-breaker in this field) that the electron
is in reality a sort of infinitesimal magnet, having two poles joined
by lines or tubes of magnetic force (the so-called Faraday tube), which
lines or tubes are of indefinite number and extent; precisely as, on
a large scale, our terrestrial globe is such a magnet supplied with
such an indefinite magnetic field. That the mass of the electron is so
infinitesimally small is explained on the assumption that this mass
is due to a certain amount of universal ether which is bound up with
the tubes where they are thickest; close to the point in space from
which they radiate, which point in space constitutes the focus of the
tangible electron.
It will require some close thinking on the part of the reader to gain
a clear mental picture of this conception of the electron; but the
result is worth the effort. When you can clearly conceive all matter as
composed of electrons, each one of which cobwebs space with its system
of magnetic tubes, you will at least have a tangible picture in mind of
a possible explanation of the forces of cohesion and gravitation--in
fact, of all the observed cases of seeming action at a distance. If
at first blush the conception of space as filled with an interminable
meshwork of lines of force seems to involve us in a hopeless mental
tangle, it should be recalled that the existence of an infinity of such
magnetic lines joining the poles of the earth may be demonstrated at
any time by the observation of a compass, yet that these do not in any
way interfere with the play of other familiar forces. There is nothing
unthinkable, then, in the supposition that there are myriads of minor
magnetic centres exerting lesser degrees of force throughout the same
space.
All that can be suggested as to the actual nature of the Faraday
tubes is that they perhaps represent a condition of the ether. This,
obviously, is heaping hypothesis upon hypothesis. Yet it should be
understood that the hypothesis of the magnetic electron as the basis of
matter, has received an amount of experimental support that has raised
it at least to the level of a working theory. Should that theory be
demonstrated to be true, we shall apparently be forced to conclude not
merely that electricity is present everywhere in nature, but that, in
the last analysis, there is absolutely no tangible thing other than
electricity in all the universe.
HOW ELECTRICITY IS DEVELOPED
Turning from this very startling theoretical conclusion to the
practicalities, let us inquire how electricity--which apparently
exists, as it were, in embryo everywhere--can be made manifest. In so
doing we shall discover that there are varying types of electricity,
yet that these have a singular uniformity as to their essential
properties. As usually divided--and the classification answers
particularly well from the standpoint of the worker--electricity is
spoken of as either statical or dynamical. The words themselves are
suggestive of the essential difference between the two types. Statical
electricity produces very striking manifestations. We have already
spoken of it as theoretically due to the conditions of the electrons
at rest. It must be understood, however, that the statical electricity
will, if given opportunity, seek to escape from any given location to
another location, under certain conditions, somewhat as water which is
stored up in a reservoir will, when opportunity offers, flow down to a
lower level. The pent-up static electricity has, like the water in the
reservoir, a store of potential energy. The physicist speaks of it as
having high tension. In passing to a condition of lower tension, the
statical electricity may give up a large portion of its energy.
If, for example, on a winter day in a cold climate, you walk briskly
along a wool carpet, the friction of your feet with the carpet
generates a store of statical electricity, which immediately passes
over the entire surface of your body. If now you touch another person
or a metal conductor, such as a steam radiator or a gas pipe, a
brilliant spark jumps from your finger, and you experience what is
spoken of as an electrical shock. If the day is very cold, and the air
consequently very dry, and if you will take pains to rub your feet
vigorously or slide along the carpet, you may light a gas jet with
the spark which will spring from your finger to the tip of the jet,
provided the latter is of metal or other conducting substance; and even
if you attempt to avoid the friction between your feet and the carpet
as much as possible, you may be constantly annoyed by receiving a shock
whenever you touch any conductor, since, in spite of your efforts, the
necessary amount of friction sufficed to generate a store of statical
electricity.
An illustration of the development of this same form of electricity,
on a large scale, is supplied by the familiar statical machine, which
consists of a large circle of glass, so adjusted that it may be
revolved rapidly against a suitable friction producer. With such a
machine a powerful statical current is produced, capable of generating
a spark that may be many inches or even several feet in length,--a
veritable flash of lightning. It is with such a supply of electricity
conducted through a vacuum tube that the cathode ray and the Roentgen
ray are produced.
Such effects as this suggest considerable capacity for doing work.
Yet in reality, notwithstanding the very sporadical character of the
result, the quantity of electricity involved in such a statical current
may be very slight indeed. Even a lightning flash is held to represent
a comparatively small amount of electricity. Faraday calculated that
the amount of electricity that could be generated from a single drop
of water, through chemical manipulation, would suffice to supply the
lightning for a fair-sized thunder-storm. Nevertheless the destructive
work that may be done by a flash of lightning may be considerable, as
everyone is aware. But, on the other hand, while the visible effect of
a stroke of lightning on a tree trunk, for example, makes it seem a
powerful agency, yet the actual capacity to do work--the power to move
considerable masses of matter--is extremely limited. The effect on a
tree trunk, it will be recalled, usually consists of nothing more than
the stripping off of a channel of bark. In other words, the working
energy contained in a seemingly powerful supply of statical electricity
commonly plays but an insignificant part.
The working agent, and therefore the form of electricity which concerns
us in the present connection, is the dynamical current. This may be
generated in various ways, but in practice these are chiefly reducible
to two. One of these depends upon chemical action, the other upon the
inter-relations of mechanical motion and magnetic lines of force. A
common illustration of the former is supplied by the familiar voltaic
or galvanic battery. The electromagnetic form has been rendered
even more familiar in recent times by the dynamo. This newest and
most powerful of workers will claim our attention in detail in the
succeeding chapter. Our present consideration will be directed to the
older method of generating the electric current as represented by the
voltaic cell.
THE WORK OF THE DYNAMICAL CURRENT
Let us draw our illustration from a familiar source. Even should your
household otherwise lack electrical appliances, you are sure to have
an electric call-bell. The generator of the electric current, which
is stored away in some out-of-the-way corner, is probably a small
so-called "dry-cell" which you could readily carry around in your
pocket; or it may consist of a receptacle holding a pint or two of
liquid in which some metal plates are immersed. Such an apparatus
seems scarcely more than a toy when we contrast it with the gigantic
dynamos of the power-house; yet, within the limits of its capacities,
one is as surely a generator of electricity as the other. If we are
to accept the latest theory, the electrical current which flows from
this tiny cell is precisely the same in kind as that which flows from
the five-thousand-horse-power dynamo. The difference is only one of
quantity.
To understand the operation of this common household appliance we must
bear in mind two or three familiar experimental facts in reference
to the action of the voltaic cell. Briefly, such a cell consists of
two plates of metal--for example, one of copper and the other of
zinc--with a connecting medium, which is usually a liquid, but which
may be a piece of moistened cloth or blotting-paper. So long as the two
plates of metal are not otherwise connected there is no electricity in
evidence, but when the two are joined by any metal conductor, as, for
example, a piece of wire--thus, in common parlance, "completing the
circuit"--a current of electricity flows about this circuit, passing
from the first metal plate to the second, through the liquid and back
from the second plate to the first through the piece of wire. The wire
may be of any length. In the case of your call-bell, for example, the
wire circuit extends to your door, and is there broken, shutting off
the current.
When you press the button you connect the broken ends of the wire, thus
closing the circuit, as the saying is, and the re-established current,
acting through a little electromagnet, rings the bell. In another case,
the wire may be hundreds of miles in length, to serve the purposes of
the telegrapher, who transmits his message by opening and closing the
circuit, precisely as you operate your door-bell. For long-distance
telegraphy, of course, large cells are required, and numbers of them
are linked together to give a cumulative effect, making a strong
current; but there is no new principle involved.
The simplest study of this interesting mechanism makes it clear that
the cell is the apparatus primarily involved in generating the electric
current; yet it is equally obvious that the connecting wire plays an
important part, since, as we have seen, when the wire is broken there
is no current in evidence. Now, according to the electron theory, as
previously outlined, the electric current consists of an actual flow
along the wire of carriers of electricity which are unable to make
their way except where a course is provided for them by what is called
a conductor. Dry air, for example, is, under ordinary circumstances,
quite impervious to them. This means, then, that the electrons flow
freely along the wire when it is continuous, but that they are
powerless to proceed when the wire is cut. When you push the button of
your call-bell, therefore, you are virtually closing the switch which
enables the electrons to proceed on their interrupted journey.
THEORIES OF ELECTRICAL ACTION
But all this, of course, leaves quite untouched the question of the
origin of the electrons themselves. That these go hurtling from one
plate or pole of the battery to the other, along the wire, we can
understand at least as a working theory; that, furthermore, the
electrons have their origin either in the metal plates or in the liquid
that connects them, seems equally obvious; but how shall we account for
their development? It is here that the chemist with his atomic theory
of matter comes to our aid. He assures us that all matter consists
in the last analysis of excessively minute particles, and that these
particles are perpetually in motion. They unite with one another to
form so-called molecules, but they are perpetually breaking away from
such unions, even though they re-establish them again. Such activities
of the atoms take place even in solids, but they are greatly enhanced
when any substance passes from the solid into the liquid state.
When, for example, a lump of salt is dissolved in water, the atoms of
sodium and of chlorine which joined together make up the molecules of
salt are held in much looser bondage than they were while the salt
was in a dry or crystalline form. Could we magnify the infinitesimal
particles sufficiently to make them visible we should probably see
large numbers of the molecules being dissociated, the liberated atoms
moving about freely for an instant and then reuniting with other atoms.
Thus at any given instant our solution of salt would contain numerous
free _atoms_ of sodium and of chlorine, although we are justified in
thinking of this substance as a whole as composed of sodium-chlorine
_molecules_. It is only by thus visualizing the activity of the atoms
in a solution that we are able to provide even a thinkable hypothesis
as to the development of electricity in the voltaic cell.
What puts us on the track of the explanation we are seeking is the
fact that the diverse atoms are known to have different electrical
properties. In our voltaic cell, for example, sodium atoms would
collect at one pole and chlorine atoms at the other. Humphry Davy
discovered this fact in the early days of electro-chemistry, just about
a century ago. He spoke of the sodium atom as electro-positive, and
of the chlorine atom as electro-negative, and he attempted to explain
all chemical affinity as merely due to the mutual attraction between
positively and negatively electrified atoms. The modern theorist goes
one step farther, and explains the negative properties of the chlorine
atom by assuming the presence of one negative electron or electricity
in excess of the neutralizing charge. The assumption is, that the
sodium atom has lost this negative electron and thus has become
positively electrified. The chlorine atom, harboring the fugitive
electron, becomes negatively electrified. Hence the two atoms are
attracted toward opposite poles of the cell.
This disunion of atoms, be it understood, must be supposed to take
place in the case of any solution of common salt, whether it rests
in an ordinary cup or forms a part of the ocean. Here we have, then,
material for the generation of the electrical current, if some means
could be found to induce the chlorine atom to give up the surplus
electron which from time to time it carries. And this means is provided
when two pieces of metal of different kinds, united with a metal
conductor, are immersed in the liquid. Then it comes to pass that the
electrons associated with the chlorine atoms that chance to lie in
contact with one of these plates of metal, find in this metal an avenue
of escape. They rush off eagerly along the metal and the connecting
wire, and in so doing establish a current which acts--if we may venture
a graphic analogy from an allied field of physics--as a sort of
suction, attracting other chlorine atoms from the body of the liquid
against the metal plate that they also may discharge their electrons.
In other words, the electrical current passes through the liquid as
well as through the outside wire, thus completing the circuit.
According to this theory, then, the electrical energy in evidence in
the current from the voltaic cell, is drawn from a store of potential
energy in the atoms of matter composing the liquid in the cell. In
practice, as is well known, the liquid used is one that affects one
of the metal poles more actively than the other, insuring vigorous
chemical activity. But the principle of atomic and electrical
dissociation just outlined is the one involved, according to theory,
in every voltaic cell, whatever the particular combination of metals
and liquids of which it is composed. It should be added, however,
that while we are thus supplied with a thinkable explanation of the
origin of this manifestation of electrical energy, no explanation is
forthcoming, here any more than in the case of the dynamo, as to why
the electrons rush off in a particular direction and thus establish an
electrical current. Perhaps we should recall that the very existence of
this current has at times been doubted. Quite recently, indeed, it has
been held that the seeming current consists merely of a condition of
strain or displacement of the ether. But we are here chiefly concerned
with the electron theory, according to which, as we have all along
noted, the seeming current is an actual current; the ether strain, if
such exists, being due to the passage of the electrons.
PRACTICAL USES OF ELECTRICITY
Various effects of the current of electrons have been hinted at above.
Considered in detail, the possible ways in which these currents may be
utilized are multifarious. Yet, they may be all roughly classified into
three divisions as follows:
First, cases in which the current of electricity is used to transmit
energy from one place to another, and reproduce it in the form of molar
motion. The dynamo, in its endless applications, illustrates one phase
of such transportation of energy; and the call-bell, the telegraph,
and the telephone represent another phase. In one case a relatively
large quantity of electricity is necessary, in the other case a small
quantity; but the principle involved--that of electric and magnetic
induction--is the same in each.
The second method is that in which the current, generated by either
a dynamo or a battery of voltaic cells, is made to encounter a
relatively resistant medium in the course of its flow along the
conducting circuit. Such resistance leads to the production of active
vibrations among the particles of the resisting medium, producing the
phenomena of heat and, if the activity is sufficient, the phenomena of
light also. It will thus appear that in this class of cases, as in the
other, there is an actual re-transformation of electrical energy into
the energy of motion, only in this case the motion is that of molecules
and not of larger bodies. The principle is utilized in the electrical
heater, with which our electric street-cars are commonly provided,
and which is making its way in the household for purposes of general
heating and of cooking. It is utilized also in various factories,
where the very high degree of heat attainable with the electrical
furnace is employed to produce chemical dissociation and facilitate
chemical combinations. By this means, for example, a compound of
carbon and silicon, which is said to be the hardest known substance,
except the diamond, is produced in commercial quantities. A familiar
household illustration of the use of this principle is furnished by the
electric light. The carbon filament in the electric bulb furnishes such
resistance to the electric current that its particles are set violently
aquiver. Under ordinary conditions the oxygen of the air would
immediately unite with the carbon particles, volatilizing them, and
thus instantly destroying the filament; but the vacuum bulb excludes
the air, and thus gives relative permanency to the fragile thread.
The third class of cases in which the electric current is commercially
utilized is that in which the transformations it effects are produced
in solutions comparable to those of the voltaic cell, the principles
involved being those pointed out in the earlier part of the present
chapter. By this means a metal may be deposited in a pure state upon
the surface of another metal made to act as a pole to the battery; as,
for example, when forks, spoons, and other utensils of cheap metals
are placed in a solution of a silver compound, and thus electroplated
with silver. To produce the powerful effects necessary in the various
commercial applications of this principle, the poles of the voltaic
cell--which cell may become in practice a large tank--are connected
with the current supplied by a dynamo. Various chemical plants at
Niagara utilize portions of the currents from the great generators
there in this way. Another familiar illustration of the principle is
furnished by the copper electroplates from which most modern books are
printed.
It appears, then, that all the multifarious uses of electricity in
modern life are reducible to a few simple principles of action, just
as electricity itself is reduced, according to the analysis of the
modern physicist, to the activities of the elementary electron. There
is nothing anomalous in this, however, for in the last analysis the
mechanical principles involved in doing all the world's work are few
and relatively simple, however ingenious and relatively complex may be
the appliances through which these principles are made available.
IX
MAN'S NEWEST CO-LABORER: THE DYNAMO
As you stand waiting for your train at elevated or subway station you
must have noticed the third rail. To outward appearance it is not
different from the other rails. It seems a mere inert piece of steel.
Yet you are well aware that a strange power abides there unseen--a
power that pulls the train, and that lurks in hiding to strike a
death-blow to any chance unfortunate whose foot or hand comes in
contact with the rail. As the heavy train dashes up, dragged by this
unseen power, probably you, in common with the rest of the world, have
been led to remark, "Is it not marvelous?"
Marvelous it surely seems. Yet the cause of our astonishment is to be
sought in the relative newness of the phenomena rather than in the
nature of the phenomena themselves. At first glance it may seem that
the intangible character of the electrical power gives it a unique
claim on our wonderment. But a moment's reflection dispels this
illusion. After all, electricity is no more intangible than heat.
Neither the one nor the other can be seen or heard, but each alike may
be felt. Yet we observe without astonishment a locomotive propelled
by the power of heat--simply because the locomotive has become an old
story. Again, electricity is far less intangible than gravitation.
Not merely may electricity be felt, but it may be generated through
transformation of other forms of energy; it may be stored away and
measured; may be conducted at will through tortuous channels, or
obstructed in its flight by the intervention of non-conductors. But
gravitation submits to no such restrictions. It eludes all of our
senses, and it absolutely disregards all barriers. To its catholic
taste all substances are alike. It holds in bondage every particle of
matter in the universe, and can enforce its influence over every kind
of atom with an impartiality that is as astounding as it is inexorable.
Moreover, this weird force, gravitation, has thus far evaded all man's
efforts to classify or label it. No man has the slightest inkling as
to what gravitation really is. If, as you glance at these lines, you
should chance to release your hold and allow the volume to drop to the
floor, you will have performed a miracle which no scientist in the
world can even vaguely explain.
As regards our electric train, then, the fact that it stands there
firmly, held fast to the rails by gravitation, is in reality as great
and as inexplicable a marvel as the fact that the electric current
gives it propulsion. Not only so, but the fact that the train goes
forward of its own inertia, as we say, for a time after the current
is shut off, presents to us yet another inexplicable marvel. It is a
fundamental property of matter, we say, when once in motion to continue
in motion until stopped by some counter-force; but that phrasing,
expressive though it be of a fact upon which so many physical phenomena
depend, is in no proper sense of the word an explanation.
Once for all, then, there is nothing unique, nothing preternaturally
marvelous, about the phenomena of electricity. And indeed, it is
interesting to note how quickly we become accustomed to these
phenomena, and how little wonder they excite so soon as they cease
to be novel. Even imaginative people have long since ceased to give
thought to the trolley car; and within a week of the opening of New
York's subway the average man came to regard it as much as a matter of
course as if he had been accustomed to it from boyhood.
And yet, in another sense of the word, the electric motor is a
wonderful contrivance. As an example of what man's ingenuity can
accomplish toward transforming the powers of nature and adapting them
to his own use, it is fully entitled to be called a marvel. Moreover,
in the last analysis, we are as helpless to explain the nature of
electricity as we are to explain the nature of gravitation. It is only
the proximal phenomena of the electric current that can be explained.
These phenomena, however, are full of interest. Let us examine them
somewhat in detail, allowing them to lead us back from electric train
to power-house and dynamo, and from dynamo as far toward the mystery of
electric energy as present-day science can guide us.
THE MECHANISM OF THE DYNAMO
If we could look into the interior of a mechanism in connection with
the trucks beneath the car, we should find an apparatus consisting
essentially of coils of wire adjusted compactly about an axis, and
closely fitted between the poles of a powerful electromagnet. These
coils of wire constitute what is called an armature. When the current
is switched on it passes through this armature, as well as through the
electromagnet, and the mutual attractions and repulsions between the
magnetic poles and the electric current in the coils of wire, cause
the armature to revolve with such tremendous energy as to move the
train--the motion of its axis being transmitted to the axle of the
car-wheels by a simple gearing.
All this is simple enough if we regard only the _how_ and not the _why_
of the phenomena. Ignoring the _why_ for the moment, let us seek the
origin of the current which, by being conducted through the armature,
has produced the striking effect we have just witnessed. This current
reaches the car through an overhead or underground wire. All that is
essential is that some conducting medium, such as an iron rail, or
a copper wire, shall form an unbroken connection between the motor
apparatus and the central dynamo where the power is generated--the
return circuit being made either by another wire or by the ordinary
rails.
The central dynamo in question will be found, if we visit the
power-house, to be a ponderous affair, suggestive to the untechnical
mind of impenetrable mysteries. Yet in reality it is a device
essentially the same in construction as the motor which drives
the train. That is to say, its unit of construction consists of a
wire-wound armature revolving on an axis and fitted between the
poles of an electromagnet. Here, however, the sequence of phenomena
is reversed, for the armature, instead of receiving a current of
electricity, is made to revolve by a belt adjusted to its axis and
driven by a steam engine. The wire coils of the armature thus made to
revolve cut across the so-called lines of magnetic force which connect
the two poles of the magnet, and in so doing generate a current of
induced electricity, which flows away to reach in due course the third
rail or the trolley-wire, and ultimately to propel the motor.
[Illustration: Lower figure copyrighted by N. Y. Edison Co.
AN ELECTRIC TRAIN AND THE DYNAMO THAT PROPELS IT.
The lower figure gives an interior view of a power house of the
Manhattan Elevated Railway Company. The upper figure shows one of the
electric engines operating on the New York Central Lines just outside
of New York. The power is conveyed to the engine by a third rail
clearly shown in the picture.]
It is hardly necessary to state that in actual practice this generating
dynamo is a complex structure. The armature is a complex series of
coils of wire; the electromagnets surrounding the armature are several
or many; and there is an elaborate system of so-called commutators
through which the currents of electricity--which would otherwise
oscillate as the revolving coil cuts the lines of magnetic force in
opposite directions--are made to flow in one direction. But details
aside, the foundation facts upon which everything depends are (1) that
a coil of wire when forced to move so that it cuts across the lines of
force in any magnetic field develops a so-called induced current of
electricity; and (2) that such an induced current possesses power of
magnetic attraction and repulsion. These facts were discovered more
than sixty years ago, and carefully studied by Michael Faraday, Joseph
Henry, and others. Faraday found that such an induced current could be
produced not merely with the aid of an iron magnet, but even by causing
a wire to cut the lines of force that everywhere connect the north and
south poles of the earth,--the earth being indeed, as William Gilbert
long ago demonstrated, veritably a gigantic magnet. Moreover, these
relations are reciprocal; so that if a wire through which a current
of electricity is passing is placed across a magnetic field, the wire
is impelled to move in a plane at right angles to the direction of the
lines of force. It is forcibly thrust aside. This side-thrust acting on
coils of wire is what produces the revolution of the armature of the
electric motor.
THE ORIGIN OF THE DYNAMO
The very first studies that had to do with the mutual relations
of electricity and magnetism were made by Hans Christian Oersted,
the Dane, as early as 1815. He discovered that a magnetic needle
is influenced by the passage near it of a current of electricity,
demonstrating, therefore, that the electric current in some way invades
the medium surrounding any conductor along which it is passing.
Oersted's experiments were repeated, and some new phenomena observed by
the Frenchman André Marie Ampère and Dominique François Arago. Arago
constructed an interesting device, in which a metal disk was made to
revolve in the presence of a current of electricity; but neither he nor
anyone else at the time was able to explain the phenomenon.
In 1824 an advance was made through the construction of the first
electric magnet by Sturgeon. Hitherto it had not been known that a
magnet could be made artificially, except by contact with a previously
existing magnet. Sturgeon showed that any core of iron may be rendered
magnetic if wound with a conducting wire, through which a current
of electricity is passed. The experiments thus inaugurated were
followed up in America by Joseph Henry of Albany who made enormous
electromagnets, capable of sustaining great weights. One of his
magnets, operated by a single cell, was able to lift six hundred and
fifty pounds of metal.
It was this apparatus which was subsequently to make possible the
utilization of electricity as a working force, but as yet no one
suspected its possibilities in this direction.
It remained for Michael Faraday, in 1831, to make the final
experiment which laid the secure foundation for the new science of
electrodynamics. Faraday constructed a tiny apparatus, consisting of a
magnet between the poles of which a metal disk was placed in such a way
that it could revolve on an axis, the disk being connected with a wire
conveying an electric current.
The details as to this most ingenious mechanism need not be given here.
Suffice it that Faraday demonstrated the interrelations of magnetism
and electricity and the possibility of causing a metal disk to revolve
through this mutual interaction. In so doing he constructed the first
dynamo-electric machine. In his hands it was a mere laboratory toy,
but the principles involved were fully elaborated by the original
experimenter, and stated in precise language which modern investigators
have not been able to improve upon.
Several decades elapsed after Faraday's initial experiment before the
phenomena of magneto-electricity were proved to have any considerable
commercial significance. A vast amount of ingenuity was required to
devise a mechanism which could advantageously utilize the principle
in question for commercial purposes. Indeed the early experimenters
did not at once get upon the right track, as their efforts were
influenced disadvantageously by an attempt to follow the principle of
the steam engine. Some interesting mechanisms were devised whereby the
motion of an armature in being drawn toward an electromagnet could be
translated into rotary motion through the use of crank-shafts and even
of beams, precisely comparable to those employed in the steam engine.
Such devices worked with a comparatively low degree of efficiency and
were totally abandoned so soon as the idea of getting rotary motion
directly from the magnet or armature was made feasible. The names of
Saxton, Clarke, Woolrich, Wheatstone, and Werner Siemens are intimately
connected with the early efforts at utilization of magneto-electric
power. The shuttle-wound armature of Siemens, invented in 1854, marked
an important progressive step.
PERFECTING THE DYNAMO
The first separately excited dynamos were constructed by Dr. Henry
Wilde, F.R.S., between 1863 and 1865, and this invention paved the way
for rapid progress. In 1866-7 Varley, Siemens, Wheatstone, and Ladd
constructed machines with several iron electromagnets, self-excited,
which were described as dynamo-electric machines, a term afterward
contracted to dynamos. In 1867 Dr. Wilde improved the armature by
introducing several coils arranged around a cylinder; the current
from a few of the coils was rectified and used to excite the field
magnet, while the main current as given off by the rest of the coils
was taken off by ring-contacts, the machine being a self-exciting,
alternating-current dynamo.
[Illustration: WILDE'S SEPARATELY EXCITED DYNAMO.
Dr. Wilde invented and patented (1863-5) the first separately excited
dynamo, with which he demonstrated that the feeble current from a small
magneto-electric machine would, by the expenditure of mechanical power,
produce currents of great strength from a large dynamo.]
The Italian, Picnotti, in 1864 invented a ring armature which,
although provided with teeth was wound with coils in such a way as to
obtain a very uniform current; but the practical introduction of the
continuous-current machines dates from 1870, when Gramme re-invented
the ring and gave it the form which is still in vogue. Von Alteneck in
1873 converted the Siemens shuttle armature along the same lines and so
introduced the drum arrangement which has since been very extensively
adopted.
Thus through the efforts of a great number of workers the idea of
utilizing electromagnetic energy for the purposes of the practical
worker came to be a reality. Numberless machines have been made
differing only as to details that need not detain us here. Everyone
is familiar with sundry applications of the dynamo to the purposes of
to-day's applied science. It must be understood, of course, that the
amount of electricity generated in any dynamo is precisely measurable,
and that by no possibility could the energy thus developed exceed
the energy required to move the coils of wire. Were it otherwise the
great law of the conservation of energy would be overthrown. In actual
practice, of course, there is loss of energy in the transaction. The
current of electricity that flows from the very best dynamo represents
considerably less working power than is expended by the steam engine in
forcibly revolving the armature. In the early days of experiments the
loss was so great as to be commercially prohibitive. With the perfected
modern dynamo the loss is not greater than fifteen per cent; but even
this, it will be noted, makes electricity a relatively expensive power
as compared with steam,--except, indeed, where some natural power, like
the Falls of Niagara, can be utilized to drive the armature.
A MYSTERIOUS MECHANISM
The efficiency of the modern dynamo is due largely to the fact that
when the poles of the magnet are made to face each other, the lines
of magnetic force passing between these poles are concentrated into a
narrow compass. With the ordinary bar magnet, as everyone is aware,
these lines of force circle out in every direction from the poles in
an almost infinite number of loops, all converging at the poles, and
becoming relatively separated at the equator in a manner which may be
graphically illustrated by the lines of longitude drawn on an ordinary
globe.
It is obvious that with a magnet of such construction only a small
proportion of the lines of magnetic force could be utilized in
generating electricity. But, as already mentioned, when the magnet
is so curved that its poles face each other, the lines of force,
instead of widely diverging, pass from pole to pole almost in a direct
stream. The strength of this magnetic stream may be increased almost
indefinitely by winding the iron core of the magnet with the coil of
wire through which the electric current is passed, thus constituting
the electromagnet which has replaced the old permanent magnet in all
modern commercial dynamos.
[Illustration: THE EVOLUTION OF THE DYNAMO.
Fig. 1.--A small example of the original commercial form of the drum
armature machine, patented in 1873 by Dr. Werner Siemens and F. Von
Hefner Alteneck. The armature is a development of the Siemens shuttle
form of 1856, and gives a nearly continuous current. Fig. 2.--An early
experimental dynamo. Fig. 3.--Ferranti's original dynamo, patented in
1882-1883. The field magnets are stationary and consist of two sets
of electro-magnets each with 16 projecting pull pieces, between which
the armature revolves. Fig. 4.--The gigantic rotary converters of the
Manhattan Elevated Railway.]
An electromagnet may be sufficiently powerful to lift tons of iron.
The force it exerts, therefore, is very tangible in its results. Yet
it seems mysterious, because so many substances are unaffected by it.
You may place your head, for example, between the poles of the most
powerful magnet without experiencing any sensation or being in any
obvious way affected. You may wave your hand across the lines of force
as freely as you may wave it anywhere else in space. Apparently nothing
is there. But were you to attempt to pass a dumb-bell or a bar of iron
across the same space, the unseen magnetic force would wrench it from
your grasp with a power so irresistible as to be awe-inspiring.
Similarly, the armature, when its coils of wire are adjusted between
the poles of the magnet, is held in a vise-like grip by the invisible
but potent lines of magnetic force which tend to make it revolve.
It requires a tremendous expenditure of energy--supplied by the
steam-engine or by water power--to enable the coiled wires of the
generating armature to stem the current of magnetic force, which is
virtually what is done when the armature revolves in such a way as to
produce electrical energy. Part of the mechanical energy thus expended
is transformed into heat and dissipated into space; but the main
portion is carried off, as we have seen, through the coiled wires of
the armature in the form of what we term the current of electricity, to
be re-transformed in due course into the mechanical energy that moves
the car.
It appears, then, that the phenomena of the electric dynamo depend upon
the curious relations that exist between magnetism and electricity.
Granted the essential facts of magneto-electric induction, all the
phenomena of the dynamo are explicable. But how explain these facts
themselves? Why is an electric current generated in a coil of wire
moving in a magnetic field? And why is a wire carrying a current of
electricity, when placed across a magnetic field, impelled to move at
right angles to the lines of magnetic force? No thoughtful person can
consider the subject without asking these questions. But as yet no
definitive answer is forthcoming. Some suggestive half-explanations,
based on an assumed condition of torsion or strain in the ether, have
been attempted, but they can hardly be called more than scientific
guesses.
Meanwhile, it may be understood that the mutual relations of the
magnetic and electrical forces just referred to are not at all
dependent upon the manner in which the electric current is generated.
The magneto-electric motor may be operated as well with a chemical
battery as with such a mechanical generating dynamo as has just been
described. The storage-batteries which have been employed in some
street railways and those which propel the electric cabs about our
city streets furnish cases in point. The only reason these are not
more generally employed is that the storage battery has not yet been
perfected so that it can produce a large supply of electricity in
proportion to its weight, and produce it economically.
X
NIAGARA IN HARNESS
"Harnessing Niagara"--the phrase has been a commonplace for a
generation; but until very recently indeed it was nothing more than a
phrase. Almost since the time when the Falls were first viewed by a
white man the idea of utilizing their powers has been dreamed of. But
until our own day--until the last decade--science had not shown a way
in which the great current could be economically shackled. A few puny
mill-wheels have indeed revolved for thirty years or so, but these
were of no greater significance than the thousands of others driven by
mountain streams or by the currents of ordinary rivers. But about a
decade ago the engineering skill of the world was placed in commission,
and to-day Niagara is fairly in harness.
If you have ever seen Niagara--and who has not seen it?-you must have
been struck with the metamorphosis that comes over the stream about
half a mile above the falls. Above this point the river flows with a
smooth sluggish current. Only fifteen feet have the waters sunk in
their placid flowing since they left Lake Erie. But now in the course
of half a mile they are pitched down more than two hundred feet. If
you follow the stream toward this decline you shall see it undergo
a marvelous change. Of a sudden the placid waters seem to feel the
beckoning of a new impulse. Caught with the witchery of a new motion,
they go swirling ahead with unwonted lilt and plunge, calling out with
ribald voices that come to the ear in an inchoate chorus of strident,
high-pitched murmurings. Each wavelet seems eager to hurry on to the
full fruition of the cataract. It lashes with angry foam each chance
obstruction, and gurgles its disapproval in ever-changing measures.
Even to the most thoughtless observer the mighty current thus unchained
attests the sublimity of almost irresistible power. Could a mighty
mill-wheel be adjusted in that dizzy current, what labors might it
not perform? Five million tons of water rush down this decline each
hour, we are told; and the force that thus goes to waste is as if
three million unbridled horses exhausted their strength in ceaseless
plunging. This estimate may be only a guess, but it matters not whether
it be high or low; all estimates are futile, all comparisons inadequate
to convey even a vague conception of the majesty of power with which
the mighty waters rush on to their final plunge into the abysm.
It is here, you might well suppose, where the appalling force of the
current is made so tangible, that man would place the fetters of his
harness, making the madcap current subject to his will. You will
perhaps more than half expect to see gigantic mechanisms of man's
construction built out over the rapids or across the face of the
cataract--so much has been said of æstheticism versus commercialism in
connection with the attempt to utilize Niagara's power. But whatever
your fears in this regard, they will not be realized. Inspect the
rapids and the falls as you may, you will see no evidence that man
has tampered with their pristine freedom. Subtler means have been
employed to tame the wild steed. The mad waves that go dashing down
the rapids are as free and untrammeled to-day as they were when the
wild Indian was the only witness of their tempestuous activity. Such
portions of the current as reach the rapids have full license to pass
on untrammeled, paying no toll to man. The water which is made to pay
tribute is drawn from the stream up there above the rapids, where it
lies placid and as yet unstirred by the beckoning incline. To see
Niagara in harness, then, you must leave the cataract and the rapids
and pass a full mile up the stream where the great river looks as calm
as the Hudson or the Mississippi, and where, under ordinary conditions,
not even the sound of the falls comes to your ear.
Prosaic enough it seems to observe here nothing more startling than a
broad _cul de sac_ of stagnant water, like the beginning of a broad
canal, extending in for a few hundred yards only from the main stream;
its waters silent, currentless, seemingly impotent. This stagnant
pool, then, not the whirling current below, is to furnish the water
whose reserve force of energy of position is drawn upon to serve man's
greedy purpose. Coming from the rapids and cataract to this stagnant
canal, you seem to step from the realm of poetic beauty to the sordid
realities of the work-a-day world. Of a truth it would seem that
"harnessing Niagara" is but a far-fetched metaphor.
WITHIN THE POWER-HOUSE
And yet if you will turn aside from the canal and enter one of the
long, low buildings that flank it on either side, you will soon be
made to feel that the metaphor was amply justified. Little as there
was exteriorly to suggest it, you are entering a fairyland of applied
science, and within these plain walls you shall witness evidences
of the ingenuity of man that should appeal scarcely less to your
imagination than the sight of the cataract itself in all its sublimity
of power.
For within these walls, by a miracle of modern science, the potential
energy which resides in the water of the canal is transformed into
an electrical current which is sent out over a network of wires to
distant cities to perform a thousand necromantic tasks,--propelling a
street car in one place, effecting chemical decompositions in another;
turning the wheels of a factory here and lighting the streets of a city
there; in short, subserving the practical needs of man in devious and
wonderful ways.
Even as you gazed disdainfully at the stagnant canal, its waters,
miraculously transformed, were propelling the trolley cars along the
brink of the cliff over there on the Canadian shore, and at the same
time were turning the wheels in many a factory in the distant city of
Buffalo. After all, then, the quiet pool of water was not so prosaic as
it seemed.
As you stand in the building where this wonderful transformation of
power is effected, the noble simplicity of the vista heightens the
mystery. The most significant thing that strikes the eye is a row
of great mushroom-like affairs, for all the world like giant tops,
that stand spinning--and spinning. These great tops are about a dozen
feet in diameter. They are whirling, so we are told, at a rate of two
hundred and fifty revolutions per minute. Hour after hour they spin on,
never varying in speed, never faltering; day and night are alike to
them, and one day is like another. They are as ceaselessly active, as
unwearying as Niagara itself, whose power they symbolize; and, like the
great Falls, they murmur exultingly as they work.
[Illustration: VIEW IN ONE OF THE POWER HOUSES AT NIAGARA.
Each of the top-like dynamos generates 5000 horse-power.]
The giant tops which thus seem to bid defiance to the laws of motion
are in reality electric dynamos, no different in principle from the
electric generators with which some visit to a street-car power-house
has doubtless made you familiar. The anomalous feature of these
dynamos--in addition to their size--is found in the fact that they
revolve on a vertical shaft which extends down into a hole in the earth
for more than a hundred feet, and at the other end of which is adjusted
a gigantic turbine water-wheel. Water from the canal is supplied this
great turbine wheel through a steel tube or penstock, seven feet in
diameter. As the turbine revolves under stress of this mighty column
of water, the long shaft revolves with it, thus turning the electric
generator at the other end of the shaft--the generator at which we
are looking, and which we have likened to a giant top--without the
interposition of any form of gearing whatever.
To gain a vivid mental picture of the apparatus, we must take an
elevator and descend to the lower regions where the turbine wheel is
in operation. As we pass down and down, our eyes all the time fixed on
the vertical revolving shaft, which is visible through a network of
bars and gratings, it becomes increasingly obvious that to speak of
this shaft as standing in "a hole in the ground" is to do the situation
very scant justice. A much truer picture will be conceived if we think
of the entire power-house as a monster building, about two hundred feet
high, all but the top story being underground. What corresponds to
the ground floor of the ordinary building is located one hundred and
fifty feet below the earth's surface; and it is the top story which we
entered from the street level, thus precisely reversing the ordinary
conditions.
PENSTOCKS AND TURBINES
As we descend now and reach at last the lowest floor of the building,
we step out into a long narrow room, the main surface of which is taken
up with a series of gigantic turnip-shaped mechanisms, each one having
a revolving shaft at its axis; while from its side projects outward and
then upward a seven-foot steel tube, for all the world like the funnel
of a steamship. This seeming funnel--technically termed a penstock--is
in reality the great tube through which the massive column of water
finds access to the turbine wheel, which of course is incased within
the turnip-shaped mechanism at its base.
As you stand there beside this great steel mechanism a sense of
wonderment and of utter helplessness takes possession of you. As you
glance down the hall at this series of great water conduits, and
strain your eyes upward in the endeavor to follow the great funnel to
its very end, an oppressive sense of the irresistible weight of the
great column of water it supports comes to you, and you can scarcely
avoid a feeling of apprehension. Suppose one of the great tubes were to
burst?--we should all be drowned like rats in a hole. There is small
danger, to be sure, of such a contingency; but it is well worth while
to have stood thus away down here at the heart of the great power-house
to have gained an awed sense of what man can accomplish toward rivaling
the wonders of nature. To have stood an hour ago on the ice bridge at
the foot of the most tremendous cataract in the world, where Nature
exhausts her powers amidst the mad rush and roar of seething waters;
and now to stand beneath this other column of water which effects a no
less wonderful transformation of energy, serenely, silently,--is to
have run such a gamut of emotions as few other hours in all your life
can have in store for you.
A MIRACULOUS TRANSFORMATION OF ENERGY
There are eleven of these great turbine mechanisms, each with a
supplying funnel of water and a revolving shaft extending upward to its
companion dynamo, in the room in which we stand. Energy representing
fifty-five thousand horse-power is incessantly transformed and made
available for man's use in the subterranean building in which we stand.
And there is not a pound of coal, not a lick of flame, not an atom
of steam involved in the transformation. There are no dust-grimed
laborers; there is no glare of furnace, no glow of heat, no stifling
odor of burning fuel;--there is only the restful hum of the machinery
that responds to the ceaseless flow of the silent and invisible waters.
Day and night the mighty river here pulls away at its turbine harness;
and man, having once adjusted that harness, may take his ease and enjoy
the fruits of his ingenuity.
As we return now to the top of the building, we shall view the spinning
dynamos with renewed interest, and a few facts regarding their output
of energy may well claim our attention. In their principle of action,
as we have seen, all dynamos are alike,--depending upon the mutual
relations between the wire-wound armature and a magnetic field. In the
present case the magnets are made to revolve and the armatures are
stationary, but this is a mere detail. There is one feature of these
dynamos, however, which is of greater importance,--the fact namely that
they operate without commutators, and therefore produce alternating
currents. This fact has an important bearing upon the distribution of
the current. Each of the dynamos before us generates the equivalent
of five thousand horse-power of energy. There are eleven such dynamos
here before us; there are ten more in the power-house on the other
side of the canal, giving a total of one hundred and five thousand
horse-power for this single plant; and there are five such plants now
in existence or in course of construction to utilize the waters of
Niagara, three being on the Canadian shore. When in full operation the
aggregate output of these plants will be six or seven hundred thousand
horse-power.
SUBTERRANEAN TAIL-RACES
As we step from the door of the power-house and stand again beside the
canal whose waters produce the wonderful effects we have witnessed
in imagination, one question remains to be answered: What becomes of
the water after it has passed through the turbine wheels down there
in the depths? The answer is simple: All the water from the various
turbines flows away into a great subterranean canal which passes down
beneath the city of Niagara Falls, and discharges finally at the level
of the rapids a few hundred yards below the Falls. The construction of
this subterranean canal would in itself have been considered a great
engineering feat a few decades ago; but of late years mountain tunnels,
such subterranean railways as the London "tube system" and tunnels
beneath rivers have robbed such structures of their mystery. It may be
added that another such subterranean canal, to serve as a tail-race for
one of the new Canadian plants, extends beneath the cataract itself,
discharging not far from the centre of the Horseshoe Falls. Another of
the power companies utilizes the water of the old surface canal which
extends to the brink of the gorge some distance below the Falls. Yet
another company on the Canadian side conveys water from far above the
rapids in a gigantic closed tube to the brink of the gorge just below
the Canadian Falls, above the point where their power-house is located.
But the principle involved is everywhere the same. The idea is merely
to utilize the weight of falling water. The water of Niagara River
is of course no different from any other body of water of equal size.
It is merely that its unique position gives the engineer an easy
opportunity to utilize the potential energy that resides in any body
of water--or, for that matter, in any other physical substance--lying
at a high level. In due course, doubtless, other bodies of water,
such as mountain lakes and mountain streams will be similarly put
into electrical harness. The electrical feature is of course the one
that most appeals to the imagination. But it may be well to recall
that the ultimate source of all the power in question is gravitation.
People fond of philosophical gymnastics may reflect with interest that,
according to the newest theory, gravitation itself is, in the last
analysis, an electrical phenomenon--a reflection which, it will be
noted, leads the mind through a very curious cycle.
THE EFFECT ON THE FALLS
Much solicitude has been expressed as to the possible effect, upon the
Falls themselves, of this withdrawal of water. For the present, it is
admitted, there is no visible effect; and to the casual observer it
may seem that almost any quantity of water the power-houses are likely
to need might be withdrawn without seriously marring the wonderful
cataract. But the statistics supplied by the power companies, taken in
connection with estimates as to the bulk of water that passes over the
Falls, do not support this optimistic view. Taking what seems to be a
reasonable estimate for a basis of computation it would appear that
when the power-houses now rapidly approaching completion are in full
operation, the total withdrawal of water from the stream will represent
a very appreciable fraction of its entire bulk--one-twenty-fifth at
the very least, perhaps as much as one-tenth. Such a diminution as
this will by no means ruin the Falls, yet it would seem as if it must
sensibly affect them, particularly at some places near Goat Island,
where the water flows at present in a very shallow stream. Be that as
it may, however, the power-houses are there, and it is probable that
their number will be added to as years go on. Whether commercialism or
æstheticism will win in the end, it remains for the legislators of the
future to decide.
Meanwhile, it is gratifying to reflect that for the present the Falls
retain their pristine beauty, even though part of the water that is
their normal due is turned aside and made to do service for man in
another way. There is only one reason why the Falls have escaped
desecration so long as they have; that reason being the very practical
one that until quite recently man has not known how to utilize their
powers to advantage. The effort was indeed made, a full generation
ago, through the construction of the canal leading from the upper
river to the bluffs overlooking the gorge below the cataract. Here
a few mill-wheels were set whirling, and a tiny fraction of the
potential energy of the water was utilized. There was no mechanical
difficulty involved in the utilization of this power. Mill-wheels are
a familiar old-time device, and even the turbine wheel is modern only
in a relative sense of the word. And it must be understood that the
turbine water-wheel utilizes the greatest proportion of the power of
falling water of any contrivance as yet known to mechanics. It was
possible, then, to utilize the water of Niagara with full effectiveness
fifty years ago, so far as the direct action of the water-wheel upon
machinery near at hand was concerned. The sole difficulty lay in the
fact that only a small amount of machinery can be placed in any one
location. The real problem was not how to produce the power, but how to
transmit it to a distance.
THE TRANSMISSION OF POWER
For fifty years mechanical engineers have looked enviously upon
unshackled Niagara, and have striven to solve the problem of
transmitting its power. It were easy enough to harness the great Fall,
but futile to do so, so long as the power generated must be used in the
immediate vicinity. So, many schemes for transmitting power were tried
one after another, and as often laid aside. There was one objection
to even the best of them--the cost. At one time it was thought that
compressed air might solve the problem. But repeated experiments did
not justify the hope. Then it was believed that the storage battery
might be made available. The storage battery, it might be explained,
does not really store electricity in the sense in which the Leyden
jar, for example, stores it. Rather is it to be likened to an ordinary
voltaic cell, the chemical ingredients of which have been rendered
active by the passage of the electric current. The active ingredients
of the storage battery are usually lead compounds, which through action
of the electric currents have been decomposed and placed in a state of
chemical instability. The dissociated molecule of the lead compound,
when permitted to reunite with the atoms with which it was formerly
associated, will give up electrical energy.
Such a storage battery might readily be charged with electricity
generated at Niagara Falls. It might then be conveyed to any part of
the world, and, its poles being connected, the charge of electricity
would be made available. Such storage batteries are in common use
in connection with electric automobiles, as we have seen. But the
great difficulty is that they are enormously heavy in proportion to
the amount of electricity that they can generate; therefore, their
transportation is difficult and expensive. In practice it is cheaper
to produce electricity through the operation of a steam engine in a
distant city than to transmit the electricity with the aid of a storage
battery from Niagara. So the storage battery served as little as
compressed air to solve the engineer's problem.
When the electric dynamo became a commercial success for such purposes
as the operation of trolley lines it seemed as if the Niagara problem
was on the verge of solution. And so, in point of fact, it really was,
though more time was required for it than at first seemed needed. The
power generated by the dynamo could, indeed, be transmitted along a
wire, but not without great loss. Sir William Siemens, in 1877, had
pointed out in connection with this very subject of the wasted power
of Niagara, that a thousand horse-power might be transmitted a distance
of, say, thirty miles over a copper rod three inches in diameter. But a
copper rod three inches in diameter is enormously expensive, and when
Siemens further stated that sixty per cent of the power involved would
be lost in transmission, it was obvious that the method was far too
wasteful to be commercially practicable.
For a time the experimenters with the transmission of electricity
along a wire were on the wrong track. They were experimenting with a
continuous current which, as we have seen, is produced from an ordinary
dynamo with the aid of a commutator. But hosts of experiments finally
made it clear that this form of current, no matter how powerful it
might be, is unable to traverse considerable distance without great
loss, being frittered away in the form of heat.
But the very term "continuous current" implies the existence of a
current that is not continuous. In point of fact, we have already
seen that a dynamo, if not supplied with a commutator, will produce
what is called an alternating current, and such a current has long
been known to possess properties peculiar to itself. It is, in
effect, an interrupted current, and it is sometimes spoken of as if
it really consisted of an alternation of currents which move first in
one direction and then in another. Such a conception is not really
justifiable. The more plausible explanation is that the alternating
current is one in which the electrons are not evenly distributed and
move with irregular motion. Perhaps we may think of the individual
electrons of such a current as oscillating in their flight, and, as
it were, boring their way into the resisting medium. In any event,
experience shows that such a current, under proper conditions, may be
able to traverse a conducting wire for a long distance with relatively
small loss.
It must be understood, however, that the mere fact that a current
alternates is not in itself sufficient to make feasible its
transmission to a remote distance. To meet all the requirements a
current must be of very high voltage. This means, in so far as we
can represent the conditions of one form of energy in the terms of
another, that it shall be under high pressure. Fortunately a relatively
simple apparatus enables the electrician to transform a current from
low to high voltage without difficulty. And so at last the problem
of transmitting power to a distance of many miles has been solved.
Electrical currents representing thousands of horse-power are to-day
transmitted from Niagara Falls to the city of Buffalo over ordinary
wires, with a loss that is relatively insignificant. A plant is in
process of construction that will similarly transmit the power to
Toronto; and it is predicted that in the near future the powers of
Niagara will be drawn upon by the factories of cities even as far
distant as New York and Chicago. Practical difficulties still stand in
the way of such very distant transmission, to be sure, but these are
matters of detail, and are almost certain to be overcome in the near
future.
All this being explained, it will be understood that the sole reason
why the new power-houses at Niagara generate electricity is that
electricity is the one readily transportable carrier of energy. We have
already explained that there is loss of energy when the steam engine
operates the dynamo. At Niagara, of course, no steam is involved; it
is the energy of falling water that is transformed into the energy of
the electrical current. Moreover, the revolving dynamo is attached to
the same shaft with the turbine water-wheel, so that there is no loss
through the interposition of gearing. Yet even so, the electric current
that flows from the dynamo represents somewhat less of energy than
the water current that flows into the turbine. This loss, however, is
compensated a thousandfold by the fact that the energy of the electric
current may now be distributed in obedience to man's will.
"STEP UP" AND "STEP DOWN" TRANSFORMERS
The dynamos in operation at Niagara do not differ in principle from
those in the street-car power-house, except in the fact that they
are not supplied with commutators. We have seen that these dynamos
are of enormous size. Those already in operation generate five
thousand horse-power; others in process of construction will develop
ten thousand. The generator which produces this enormous current is
about eleven feet in diameter, and it makes two hundred and fifty
revolutions per minute. The armatures are so wound that the result is
an alternating current of electricity of twenty-two hundred volts.
This current represents, it has been said, raw material which is to
be variously transformed as it is supplied to different uses. To
factories near at hand, indeed, the current of twenty-two hundred
volts is supplied unchanged; but for more distant consumption it is
raised to ten thousand volts; and that portion which is sent away to
the factories of Buffalo and other equally distant places is raised to
twenty-two thousand volts.
[Illustration: ELECTRICAL TRANSFORMERS.
The upper figure shows Ferranti's experimental transformer built in
1888. It has a closed iron circuit, built up of thin strips filling the
interior of the coil and having their ends bent over and overlapping
outside. The lower figure shows a simple transformer known as
Sturgeon's induction coil. The middle figure gives a view of the series
of converters in the power house of the Manhattan Elevated Railway.]
The transformation from a relatively low voltage to the high one
is effected by means of what is called a step-up transformer. This
is an apparatus which brings into play a principle of electric
induction not very different from that which was responsible for the
generation of the current of electricity in the dynamo. The principle
is that evidenced in the familiar laboratory apparatus known as the
Ruhmkorff coil. The transformer consists essentially of a primary
coil of relatively large wire, surrounded by, but insulated from, a
secondary coil of relatively fine wire. When the interrupted current
is sent through the primary coil of such an apparatus, an induced
counter-current is generated in the secondary coil. Of course there is
no gain in the actual quantity of electricity, but the voltage of the
current generated in the finer wire is greatly increased. For example,
as we have seen, the current that came from the dynamo at twenty-two
hundred volts is raised to ten thousand or twenty-two thousand volts.
These proportions may be varied indefinitely by varying the relative
sizes and lengths of the primary and secondary coils.
How shall we picture to ourselves the actual change in the current
represented by this difference in voltage? We might prove, readily
enough, that the difference is a real one, since a wire carrying a
current of low voltage may be handled with impunity, while a similar
wire carrying a current of high voltage may not safely be touched. But
when we attempt to visualize the difference in the two currents we are
all at sea. We may suppose, of course, that electrons spread out over a
long stretch of the secondary coil must be more widely scattered. One
can conceive that the electrons, thus relatively unimpeded, may acquire
a momentum, and hence a penetrative power, which they retain after they
are crowded together in a straight conductor. But this suggestion at
best merely hazards a guess.
Arrived at the other end of its journey, the current which travels
under this high voltage is retransformed into a low-voltage current
by means of an apparatus which simply reverses the conditions
of the step-up transformer, and which, therefore, is called a
step-down transformer. The electricity which came to Buffalo as a
twenty-two-thousand-volt current is thus reduced by any desired
amount before it is applied to the practical purposes for which it is
designed. It may, for example, be "stepped-down" to two thousand volts
to supply the main wires of an electric-lighting plant; and then again
"stepped-down" to two hundred volts to supply the electric lamps of an
individual house.
Who that reads by the light of one of these electric lamps, let us say
in Buffalo, and realizes that he is reading by the transformed energy
of Niagara River, dare affirm that in our day there is nothing new
under the sun?
XI
THE BANISHMENT OF NIGHT
One great fundamental advantage that man has won over the other
animals is that although by nature a diurnal animal he has made night
almost equally subject to his dominion through the use of artificial
light. He thus establishes an average day of sixteen or eighteen
hours in place of the twelve-hour day within which his activities
would otherwise be restricted. Of course this conquest of the night
began at an early stage of the human development, since a certain
familiarity with the uses of fire was attained long before man came out
of the ages of savagery. But when the transition had been made from
the primitive torch to the simplest type of lamp, there was for many
centuries a cessation of progress in this direction, and it remained
for comparatively recent generations to provide more efficient methods
of lighting. Indeed, the culminating achievements are matters which
make the most recent history. It is the purpose of the ensuing pages
to narrate the story of the successive practical achievements through
which man has been enabled virtually to turn night into day.
PRIMITIVE TORCH AND OPEN LAMP
To moderns, in an age when even the time-honored gas jets and kerosene
lamps are regarded as obsolescent, that ancient form of illuminant,
the candle, seems about the most primitive form of light-producing
apparatus. In point of fact, however, the candle holds no such place
in the chronological order of lighting-device discovery, being a
relatively late innovation. Indeed, lamps of various kinds, even those
burning petroleum, were used thousands of years before the relatively
clean and effective candle was invented.
The camp fires of primitive man must have suggested the use of a
fire-brand for lighting purposes almost as soon as the discovery of
fire itself; but the development of any means of lighting his caves or
rude huts, even in the form of torches, was probably a slow process.
For our earliest ancestors were not the nocturnal creatures their
descendants became early in the history of civilization. To them the
period of darkness was the time for sleeping, and their waking hours
were those between dawn and dusk. It was only when man had reached a
relatively high plane above the other members of the animal kingdom,
therefore, that he would wish to prolong the daylight, and then the use
of the torch made of some resinous wood would naturally suggest itself.
Just when the ancient lamp was invented in the form of a vessel
filled with oil into which some kind of wick was dipped, cannot be
ascertained, but its invention certainly antedated the Christian Era
by several centuries. And it is equally certain that once this smoky,
foul-smelling lamp had been discovered, it remained in use, practically
without change or improvement, until the end of the twelfth century,
the date of the invention of the candle. Such lamps were used by the
Greeks and Romans, great quantities of them being still preserved. They
were simply shallow, saucer-like vessels for holding the oil, into
which the wick was laid, so arranged that the upper end rested against
the edge of the vessel. Here the oil burned and smoked, capillarity
supplying oil to the burning end of the wick, which was pulled up from
time to time as it became shortened by burning, either with pincers
made for the purpose, or perhaps more frequently by the ever useful
hairpin of the matron.
As the thick wick did not allow the air to penetrate to burn the carbon
of the oil completely, a nauseous smoke was given off constantly which
was stifling when a draught of air prevented its escape through the
hole in the roof--the only chimney used by the Greeks. And since this
was the only kind of lamp known at the time, the palace of the Roman
Emperor and hut of the Roman peasant were necessarily alike in their
methods of lighting if in little else. The Emperor's lamps might be
modeled of gold and set with precious stones, while those of the
peasant were of rudely modeled clay; but each must have evoked, along
with its dim light, an unwholesome modicum of smoke and malodor.
It was this form of lamp, practically unaltered except occasionally in
design, that remained in common use during the Middle Ages; and when,
at the close of the twelfth century, the "tallow candle" was invented,
that now despised device must have been almost as revolutionary in its
effect as the incandescent burner and the electric bulb were destined
to be in a more recent generation. It burned with dazzling brilliancy
in comparison with the oil lamp; it gave off no smoke and little smell;
it needed no care, and it occupied little space. Then for the first
time in the history of the world reasonably good house illumination
became possible. Several additional centuries elapsed, however, before
the idea was developed of placing a candle in a covered glass-sided
receptacle, to form a lantern or a street lamp.
For generations the candle held supreme place, though its cost made it
something of a luxury; doubly so if wax was substituted for tallow in
its composition. But toward the close of the eighteenth century, when
the action of combustion had begun to be better understood, attempts
were made to improve the wicks and burners of oil lamps. In 1783, an
inventor named Leger, of Paris, produced a burner using a broad, flat,
ribbonlike wick in which practically every part of the oil supply was
brought into contact with the air, producing, therefore, a steady flame
relatively free from smoke. The flame, while broad, was extremely thin,
and its light was consequently radiated very unevenly. Portions of a
room lying in the direction of the long axis of the flame were but
poorly lighted. To overcome this difficulty, a curved form of burner
was adopted; and this led eventually to the invention of the circular
Argand burner, the prototype of the best modern lamp-burners.
TALLOW CANDLE AND PERFECTED OIL LAMP
Stated in scientific terms, the problem of the ideal lamp-wick resolves
itself into a question of how to supply oxygen to every portion of
the flame in sufficient quantities to bring all the carbon particles
to a temperature at which they are luminous. It occurred to Argand
that this could be done by giving the wick a circular form like a
cylindrical tube, giving the air free access to the centre of the tube
as well as to its outer surface. In his lamp the reservoir of oil was
placed at a little distance from, and slightly above, the tube holding
the burner, connected with it by a small tube much as the tank of
the modern "student lamp" connects with the burner. In this manner a
fairly good lamp was produced,--a decided improvement over any made
heretofore,--and when, in 1765, Quinquet added a glass chimney to this
lamp a new epoch of artificial lighting was inaugurated. "This date is
of as much importance in artificial lighting as is 1789 in politics,"
says one writer. "Between the ancient lamps and the lamps of Quinquet
there is as much difference as between the chimney-place of our parlors
and the fireplaces of our original Aryan ancestors, formed by a hole
dug in the ground in the centre of their cabins."
A little later Carcel still further improved the Quinquet lamp by
adapting a clock movement that forced the oil to rise to the wick,
so that it was no longer necessary to have the burner and the
reservoir separated by a tube. This was still further improved upon
by substituting a spring for the clockwork, the result being a lamp
of great simplicity, yet one which gave such results that it replaced
the candle as a unit for measuring the illuminating power of different
sources of light.
These various burners should not be confused with the modern burners of
the ordinary kerosene lamps. Mineral oils had not as yet come into use
for illuminating purposes, except as torches or in simple lamps like
those of the Romans, as refining processes had not been perfected, and
the smoke and odors from crude petroleum were absolutely intolerable in
closed rooms.
Many other substances were tried in place of the heavy oils, such as
the volatile hydrocarbons and alcohols, but with no great success.
Early in the nineteenth century a lamp burning turpentine, under
the name of "camphine," was invented that gave a good light and was
smokeless; but like most others of its type, it was dangerous owing
to its liability to explode. And it was not until methods of refining
petroleum had been improved that "mineral-oil lamps"--the predecessors
of the modern type of lamps--came into use.
The invention of this type of lamp was a relatively easy task--a
simple transition and adaptation as processes of refining the oil were
perfected. The principle of combustion was, of course, the same as in
the Argand type of lamps burning animal and vegetable oils; but mineral
oils are of such consistency that capillarity causes an abundant supply
of oil to rise in the wick, so that clockwork and spring devices, such
as were used in the Carcel lamps, could be dispensed with.
GAS LIGHTING
While the rivalry between the candle and the new forms of lamps was at
its height, and just as the lamp was gaining complete supremacy, a new
method of artificial illumination was discovered that was destined to
eclipse all others for half a century, and then finally to succumb to a
still better form. As early as the beginning of the eighteenth century
the Rev. Joseph Clayton, in England, had made experiments in the
distillation of coal, producing a gas that was inflammable. A little
later Dr. Stephen Hales published his work on _Vegetable Staticks_, in
which he described the process of distilling coal in which a definite
amount of gas could be obtained from a given quantity of coal.
No practical use was made of this discovery, however, until over
half a century later. But just at the close of the century a Scot,
William Murdoch, became interested in the possibilities of gases
as illuminants, and finally demonstrated that coal gas could be
put to practical use. In 1798, being employed in the workshops of
Boulton and Watt in Birmingham, he fitted up an apparatus in which he
manufactured gas, lighting the workshops by means of jets connected by
tubes with this primitive plant. Shortly after this, a Frenchman, M.
Lebon, lighted his house in Paris with gas distilled from wood, and
the Parisians soon became interested in the new illuminant. England
seems to have been the first country to use it extensively in public
buildings, however, the London Lyceum Theatre being lighted with gas
in 1803. By 1810 the great Gas-Light and Coke Company was formed, and
within the next five years gas street-lamps had become familiar objects
in the streets of London, and house illumination by this means a common
thing among the wealthier classes.
In the early days of gas-lighting the results were frequently
disappointing, because no suitable and efficient type of burner had
been devised; but in 1820 Neilson of Glasgow discovered the principle
of the now familiar flat burner, of which more examples still remain
in use the world over than of all other kinds combined. Indeed, this
simple, but as we now regard it, inefficient burner, would probably
have remained the best-known type for many years longer than it did
had not the possibilities of lighting by electricity aroused persons
interested in the great gas-plants to the fact that the new illuminant
was jeopardizing their enormous investments; making it clear that they
must bestir themselves and improve their flat burners if they would
arrest disaster. To be sure, several modifications of the round Argand
burner had been introduced from time to time, some of them being a
distinct improvement over the flat burner, but these did not by any
means seriously compete with electric light. And it was not until the
incandescent mantle was perfected that gas as a brilliant illuminant
was able to make a stand against its new competitor.
THE INCANDESCENT GAS MANTLE
It has been known almost since the beginnings of civilization that all
solids can be made to emit light when heated to certain temperatures.
Some substances were known to be peculiarly adapted to this purpose,
such as lumps of lime, and for many years the calcium light or
"lime-light" as it is popularly called, had been in use for special
purposes, and was the most intense light known. This light is made by
heating a block of lime to the highest practicable temperature by means
of a blast of oxygen and coal gas; but such lights were too complicated
and expensive for general purposes. It had been determined even as
early as the beginning of the nineteenth century, however, that the
high temperature necessary for producing this light was due in part at
least to the fact that such a large amount of material had to be raised
to incandescence. It was evident, therefore, that if a small amount
of some such substance as lime and magnesia could be spread out so as
to present a large surface in a small space, such as is represented
by basket-work, sufficient heat for making it incandescent might be
obtained from an ordinary gas-and-air blowpipe.
Here then was the germ of the "mantle" idea; and such an apparatus,
known as the Clamond mantle, which was made of threads of calcined
magnesia, was shown at the Crystal Palace Exhibition, in London, in
1882. Curiously enough, this mantle and burner worked in an inverted
position, the mantle being suspended bottom upwards below the burner
through which the blast of gas was forced. The light given by this
mantle was most brilliant--little short of the older calcium light,
in fact--but the device itself was too complicated to be of service
for ordinary lighting purposes. The principle was correct, but the
construction of the mantle was defective.
Meanwhile a German scientist, Dr. Auer von Welsbach, who had become
famous in the scientific world for his researches on rare metals, was
experimenting with certain oxides of different metals, and developing
a method of handling them that finally resulted in the perfected
incandescent burner in use at present. His process, which in theory at
least was not entirely original with him, was to dip an open fabric
of cotton into a solution of the nitrates of the metals to be used,
drying it, and converting the nitrates into oxides by burning; the
cotton fabric disappearing but leaving the skeleton of the oxide, which
retained its original shape.
At the same time corresponding improvements were made in the type of
burner, which is quite as essential to success as the mantle itself.
It had been found that it was absolutely essential for such a burner
to give a practically non-luminous flame, as otherwise the deposit of
carbon particles will ruin the mantle. Two ways of obtaining this are
possible; one by mixing a certain quantity of air with the gas before
combustion, the other to burn the gas in so thin a flame that the air
permeates it freely. Several burners of both types were used at first,
but gradually the burners in which the air is mixed with the gas became
the more popular, and most of the incandescent burners now on the
market are of this type.
In the construction of mantles at the present time, while the principle
of their use remains the same as that of the lime-light, lime itself
is not used, the oxides of certain other metals having proved better
adapted for the purpose. Thus the Welsbach patent of 1886 covered the
use of thoria, either alone or mixed with other substances such as
zirconia, alumina, magnesia, etc.; thoria being considered as having
a very high power of light emission. Later it was discovered that
pure thoria emits very little light by itself, although it possesses
a refractory nature that gives a stability to the mantle unequalled
by any other material as yet discovered. When combined with a small
trace of the oxides of certain rare metals, however, such as uranium,
terbium, or cerium, thoria mantles have a very high power of light
emission, most modern mantles being composed of about ninety-nine per
cent. thoria with one per cent. cerium.
In the ordinary method of manufacturing such mantles, a cotton-net
cylinder about eight inches long, more or less according to the size
of mantle required, is made, one end being contracted by an asbestos
thread. A loop of the same material, or in some cases a platinum wire,
is fastened across the opening, to be used for suspending the mantle
when in use. The cotton-thread cylinder is soaked in a solution of
the nitrates of the metals thorium and cerium, and is then wrung out
to remove the excess, stretched on a conical mold, and dried. The
flame of an atmospheric burner being applied to the upper part at the
constricted position, the burning extends downward, converting the
nitrates into oxides, and removing the organic matter. Considerable
skill is required in this part of the process, as the regular shape of
the mantle is largely dependent upon the regularity of the burning.
As a finishing process a flame is applied to the inside of the mantle
after it has cooled, to remove all traces of carbon that may remain.
The mantle is now ready for use, but is so fragile that it can scarcely
be touched without breaking, and such handling as would be necessary
for shipment would be out of the question. It is therefore strengthened
temporarily by being dipped into a mixture of collodion and castor oil,
which, when dry, forms a firm but elastic jacket surrounding all parts.
It is this collodion jacket that is burned away when the new mantle is
placed on the burner before the gas is turned on.
Quite recently the method of manufacturing mantles used by Clamond has
been revived. In this method the cotton thread is dispensed with, the
thread used being made from a paste containing the mantle material
itself. The paste is placed in a proper receptacle the bottom of
which is perforated with minute openings, and subjected to pressure,
squeezing out the material in long filaments. When dry these are wound
on bobbins, and, after being treated by certain chemical processes, are
ready for weaving into mantles. It is claimed for mantles made on this
principle that they last much longer and retain their light-emitting
power more uniformly than mantles made by the older process.
THE INTRODUCTION OF ACETYLENE GAS
When the incandescent mantle had been perfected so as to be an
economical as well an as efficient light-giver, the position of coal
gas as an illuminant seemed again secured against the encroachments
of its rivals, the arc and incandescent electric lights. But just at
this time another rival appeared in the field that not only menaced
the mantle lamp but the arc and incandescent light as well. Curiously
enough, this new rival, acetylene gas, had been brought into existence
commercially by the electric arc itself. For although it had been
known as a possible illuminant for many years, the calcium carbide for
producing it could not be manufactured economically until the advent of
the electric furnace, itself the outcome of Davy's arc light.
Even as early as 1836 an English chemist had made the discovery that
one of the by-products of the manufacture of metallic potassium would
decompose water and evolve a gas containing acetylene; and this was
later observed independently from time to time by several chemists in
different countries. No importance was attached to these discoveries,
however, and nothing was done with acetylene as an illuminant until the
last decade of the nineteenth century. By this time electric furnaces
had come into general use, and it was while working with one of these
furnaces in 1892 that Mr. Thomas F. Wilson, in preparing metallic
calcium from a mixture of lime and coal, produced a peculiar mass of
dark-colored material, calcium carbide, which, when thrown into water,
evolved a gas with an extremely disagreeable odor. When lighted, this
gas burned with astonishing brilliancy, and, as its cost of production
was extremely small, the idea of utilizing it for illuminating was at
once conceived and put into practice.
The secret of the cheap manufacture of the carbide lies in the
fact that the extremely high temperature required--about 4500°
Fahrenheit--can be obtained economically in the electric furnace,
but not otherwise. Thus electricity created its own greatest rival
as an illuminant. It followed naturally that the ideal place for
manufacturing the carbide would be at the source of the cheapest supply
of electricity, and as the "harnessed" Niagara Falls represented the
cheapest source of electric supply, this place soon became the centre
of the carbide industry. Here the process of manufacture is carried out
on an enormous scale. In practice, lime and ground coke are thoroughly
mixed in the proportion of about fifty-six parts of lime to thirty-six
parts of coke. When this mixture has been subjected to the heat of the
electric furnace for a short time an ingot of pure calcium carbide is
formed, surrounded by a crust of less pure material. The ingot and
crust together represent sixty-four parts of the original ninety-two
parts of lime and coke, the remaining twenty-eight parts being
liberated as carbon-monoxide gas.
Calcium carbide as produced by this process is a dark-brown crystalline
substance which may be heated to redness without danger or change. It
will not burn except when heated in oxygen, and will keep indefinitely
if sealed from the air. Chemically it consists of one atom of lime
combined with two atoms of carbon (CaC2); and to produce acetylene
gas, which is a combination of carbon and hydrogen (C2H2) it is
only necessary to bring it into contact with water, acetylene gas and
slaked lime being formed. One pound of pure carbide will produce five
and one half cubic feet of gas of greater illuminating power than
any other known gas. The flame is absolutely white and of blinding
brilliancy, giving a spectrum closely approximating that of sunlight.
The light is so strongly actinic that it is excellent for photography.
Here was a gas that could be made in any desired quantities simply by
adding water to a substance costing only about three cents a pound;
its cost of production, therefore, representing only about one sixth
of the dollar-per-thousand-feet rate usually charged for illuminating
gas in our cities. It could be used in lamps and lanterns made with
special burners and with the simple mechanism of a small water tank
which allowed water to drip into a receptacle holding the carbide;
or--reversing the process--an apparatus that dropped pieces of carbide
into the water tanks. It was, in short, the cheapest illuminant known,
generated by an apparatus that was simplicity itself.
There were, however, two defects in this gas: its odor was
intolerable--the "smell of decayed garlic," it has been aptly
called--and when mixed with air it was highly explosive. The first of
these defects could be overcome easily; when the burner consumed all
the gas there was no odor. The second, the explosive quality, presented
greater difficulties. These were emphasized and magnified by the number
of defective lamps that soon flooded the market, many of these being so
badly constructed that explosions were inevitable. As a result a strong
prejudice quickly arose against the gas, some countries passing laws
prohibiting its use.
But further inquiry into the cause of the frequent disasters revealed
the fact that when the burner of a lamp was constructed so that the air
for combustion was supplied after the gas issued from the jet, there
was no danger of explosion. And as lamps carefully constructed on this
principle replaced the early ones of faulty construction, confidence
in acetylene was restored. Methods were devised for supplying the gas
for house-illumination like ordinary gas, and the occupants of country
houses were afforded a means of lighting their houses on a scale of
brilliancy hitherto unapproached, yet with economy and relative safety.
It was found also that the brilliancy of the acetylene flame was of
such intensity that it could be used, like the electric arc light, as a
search-light. It thus furnished a simple means of supplying small boats
and vehicles with such lights, which they could not otherwise have
had. It also supplied army signal-corps with an apparatus for flashing
messages--an apparatus that was ideal on account of its simplicity and
small size.
At the Pan-American Exhibition at Buffalo the various illuminating
exhibits were among the most conspicuous and attractive features. But
even amid the dazzling electrical displays the Acetylene Building was
a noteworthy object. "It was the most brilliantly and beautifully
lighted building in the grounds," declared one observer. "It sparkled
like a diamond, and was the admiration of all visitors. In it were
generators of all types--most of them supplying the gas for their own
exhibits--several being the latest exponents of the art, so simple that
they can be safely managed by unskilled labor; in fact, 'the brains are
in the machines,' and when the attendant has charged them with carbide
and filled them with water--given them food and drink--they will work
steadily until they need another meal." Indeed, these exhibits at the
Pan-American Exhibition demonstrated conclusively that acetylene gas
occupies a field by itself as a practical illuminant.
At the same exposition a standard was established for good stationary
acetylene generators for house-lighting, and the fact that a large
number of generators fulfilled the requirements of the set of rules
laid down showed how thoroughly the problem of handling this gas has
been solved. Some of these rules used as tests are instructive to
anyone interested in the subject, and a few of them are given here.
They specified, for example, that--
"The carbide should be dropped into the water," the reverse process of
letting the water drip on the carbide, as was done in most of the early
generators, being condemned. "There must be no possibility of mixing
air with the acetylene gas. Construction must be such that an addition
to the charge of carbide can be made at any time without affecting the
lights. Generators must be entirely automatic in their action--that is
to say: after a generator has been charged, it must need no further
attention until the carbide has been entirely exhausted. The various
operations of discharging the refuse, filling with fresh water,
charging with carbide, and starting the generator must be so simple
that the generator can be tended by an unskilled workman without danger
of accident. When the lights are out, the generation of gas should
cease. The carbide should be fed automatically into the water in
proportion to the gas consumed."
Perhaps the most significant thing, showing the stage of progress that
has been made in overcoming the danger of explosions from acetylene
gas, is that the use of generators meeting some such requirements as
the above is not prohibited by fire underwriters. This in itself is
very convincing evidence of their safety.
THE TRIUMPH OF ELECTRICITY
Throughout the ages primitive man had had constantly before him two
sources of light other than that of the sun, moon, and stars. One
of these, the fire of ordinary combustion, he could understand and
utilize; the other, more powerful and more terrible, which flashed
across the heavens at times, he could not even vaguely understand, and,
naturally, did not attempt to utilize. But early in the seventeenth
century some scientific discoveries were made which, although their
destination was not even imagined at the time, pointed the way that
eventually led to man's imitating in the most striking manner Nature's
electrical illumination.
About this time Otto von Guericke, the burgomaster-philosopher of
Magdeburg, in the course of his numerous experiments, had discovered
some of the properties of electricity, by rubbing a sulphur ball, and
among other things had noticed that when the ball was rubbed in a
darkened room, a faint glow of light was produced. He was aware, also,
that in some way this was connected with the generation of electricity,
but in what manner he had no conception. In the opening years of the
following century Francis Hauksbee obtained somewhat similar results
with glass globes and tubes, and made several important discoveries
as to the properties of electricity that stimulated an interest in
the subject among the philosophers of the time. Gray in England, and
Dufay in France, who became enthusiastic workers in the field, soon
established important facts regarding conduction and insulation, and
by the middle of the eighteenth century the production of an electric
spark had become a commonplace demonstration.
But until this time it had not been demonstrated that this electric
spark was actual fire, although there was no disputing the fact that
it produced light. In 1744, however, this point was settled definitely
by the German, Christian Friedrich Ludolff, who projected a spark
from a rubbed glass rod upon the surface of a bowl of ether, causing
the liquid to burst into flame. A few years later Benjamin Franklin
demonstrated with his kite and key that lightning is a manifestation of
electricity.
But neither the galvanic cell nor the dynamo had been invented at
that time, and there was no possibility of producing anything like a
sustained artificial light with the static electrical machines then
in use. It was not until the classic discovery of Galvani and the
resulting invention of the voltaic, or galvanic, cell shortly after,
that the electric light, in the sense of a sustained light, became
possible. And even then, as we shall see in a moment, such a light was
too expensive to be of any use commercially.
DAVY AND THE FIRST ELECTRIC LIGHT
As soon as Volta's great invention was made known a new wave of
enthusiasm in the field of electricity swept over the world, for the
constant and relatively tractable current of the galvanic battery
suggested possibilities not conceivable with the older friction
machines. Batteries containing large numbers of cells were devised; one
having two thousand such elements being constructed for Sir Humphry
Davy at the Royal Institution, of London. By bringing two points of
carbon, representing the two poles of the battery, close together, Davy
caused a jet of flame to play between them--not a momentary spark, but
a continuous light--a true voltaic arc, like that seen in the modern
street-light to-day.
"When pieces of charcoal about an inch long and one-sixth of an inch in
diameter were brought near each other (within the thirtieth or fortieth
of an inch)," wrote Davy in describing this experiment, "a bright
spark was produced, and more than half the volume of charcoal became
ignited to whiteness; and, by withdrawing the points from each other, a
constant discharge took place through the heated air, in a space equal
to at least four inches, producing a most brilliant ascending arch of
light, broad and conical in form in the middle. When any substance was
introduced into this arch, it instantly became ignited; platina melted
in it as readily as wax in a common candle; quartz, the sapphire,
magnesia, lime, all entered into fusion; fragments of diamond and
points of charcoal and plumbago seemed to evaporate in it, even when
the connection was made in the receiver of an air-pump; but there was
no evidence of their having previously undergone fusion. When the
communication between the points positively and negatively electrified
was made in the air rarefied in the receiver of the air-pump, the
distance at which the discharge took place increased as the exhaustion
was made; and when the atmosphere in the vessel supported only
one-fourth of an inch of mercury in the barometrical gauge, the sparks
passed through a space of nearly half an inch; and, by withdrawing the
points from each other, the discharge was made through six or seven
inches, producing a most brilliant coruscation of purple light; the
charcoal became intensely ignited, and some platina wire attached to
it fused with brilliant scintillations and fell in large globules upon
the plate of the pump. All the phenomena of chemical decomposition were
produced with intense rapidity by this combination."
It will be seen from this that as far as the actual lighting-part of
Davy's apparatus was concerned, it was completely successful. But the
source of the current--the most essential part of the apparatus--was
such that even the wealthy could hardly afford to indulge in it as a
luxury. The initial cost of two thousand cells was only a small item of
expense compared with the cost of maintaining them in working order,
and paying skilled operators to care for them. So that for the moment
no practical results came from this demonstration, conclusive though
it was, and the introduction of a commercial electric light was of
necessity deferred until a cheaper method of generating electricity
should be discovered.
This discovery was not made for another generation, but then, as
seems entirely fitting, it was made by Davy's successor and former
assistant at the Royal Institution, Sir Michael Faraday. His discovery
of electromagnetic induction in 1831 for the first time made possible
the electric dynamo, although still another generation passed before
this invention took practical form. In the meantime, however, the
magneto-electric machine of Nollet was used for generating an electric
current for illuminating purposes as early as 1863; and when finally
the dynamo-electric machine was produced by Gramme in 1870, engineers
and inventors had at their disposal everything necessary for producing
a practical electric illuminant.
It must not be supposed, however, that inventors stood by patiently
with folded hands waiting for the coming of a machine that would
furnish them with an adequate current without attempting to produce
electric lamps. On the contrary, they were constantly wrestling with
the problem, in some instances being fairly successful, even before the
invention of the magneto-electric machine. Great advances had been made
in batteries and cell construction over the primitive cells of the time
of Davy, and for exhibition purposes, and even for lighting factories
and large buildings, fairly good electric lights had been used before
1863.
The first practical application of electric lighting seems to have
been made in France in 1849. During the production of the opera "The
Prophet" the sun was to appear, and for this purpose an electric arc
light was used. The success of this effort--an artificial sun being
produced that seemed almost as dazzling to the astonished audience as
Old Sol himself--stimulated further efforts in the same direction. The
previous year W. E. Staite in England made experiments along similar
lines in the large hall of the hotel of Sunderland. He generated a
light "resembling the sun, or the light of day, and making candles
appear as obscure as they do by daylight," according to the _Times_ of
the following morning. The electric light was therefore proved to be a
practical illuminator, although it was not until the introduction of
the Gramme dynamo-electric machine that its great economic utility was
demonstrated.
THE JABLOCHKOFF CANDLE
In Sir Humphry Davy's experiments with his arc light he was led to
believe that the light between the two points of carbon would be
produced even in an absolute vacuum, if it were possible to create one.
Several scientists at the time disputed this contention, and M. Masson,
Professor of Physics in the _École Centrale des Arts et Manufactures_
in Paris was particularly active in combatting the idea, maintaining
that the arc had the same cause as the electric spark--the transport
by electricity of the incandescent particles of the electrodes through
the atmosphere. It was certain, at any rate, that no light was produced
when the opposing carbons were brought into contact with each other,
or were, on the other hand, separated too widely; and since there
was a constant wearing away and shortening of the points, and thus
a constantly increasing space between them, the great difficulty in
making a practical lamp lay in regulating this distance automatically.
It was finally accomplished, however, by the invention of a Russian
officer, M. Jablochkoff, in 1876. The "Jablochkoff candle," as his
lamp was called, marked an epoch in the history of electric lighting.
One great merit of this invention was its simplicity, and while it
has long since gone out of use, having been superseded by still
simpler and better devices, it must always be recalled as an important
stepping-stone in the progress of artificial illumination.
The name "candle" for Jablochkoff's lamp was suggested by the fact
that the two carbons were placed side by side, instead of point to
point, the light at the top thus suggesting a candle. Between these
two carbons, and extending their whole length except at the very tips,
was an insulating material that the arc could not pierce, but which
burned away at a rate commensurate with the shortening of the carbons.
In this manner the points were kept constantly at the proper distance
without regulating-machinery of any kind. This ingenious apparatus
had the additional advantage that it could be placed on any kind of a
bracket or chandelier that was properly wired, thus dispensing with the
cumbersome frames and machines of the point-to-point carbon arc lights
then being introduced.
One difficulty at first encountered in using the Jablochkoff candle was
the starting of the voltaic arc. In doing this it was necessary that
contact be made between two carbon points, whether they lie parallel or
point to point, and the necessary slight separation for producing the
light effected later. To accomplish this Jablochkoff joined the tips of
the carbons of his candle with a thin strip of carbon, which quickly
burned away when the current was turned on, leaving the necessary space
between the points for the arc.
There was one difficulty with the "candle" that seemed insurmountable
for a time--the wasting of the two carbons was unequal, as in any arc
light, the points thus gradually drawing apart until the passage of the
current was no longer possible. To overcome this the rapidly wasting
positive carbon was made double the thickness of its mate; but while
this answered fairly well the thinner negative carbon gradually became
heated by the increased resistance, and burned up too rapidly. The
difficulty was finally overcome by the simple expedient of alternating
the flow of the current, so that each carbon was alternately a
positive and a negative pole. As the magneto-electric machines then in
use produced alternating currents it was only necessary to use such
machines for generating the current to produce an equal destruction of
both carbons.
The simplicity and excellence of the light of these "candles" brought
them at once into general popularity, not only in the large cities of
Europe, but in many out-of-the-way places. Greece, Portugal, and other
obscure European countries adopted them, and even Brazil, La Plata,
and Mexico installed many plants. But stranger still, they were soon
used for illuminating the palaces of the Shah of Persia and the King
of Cambodia, and a little later were introduced into the residence of
the savage King of Burma. In short, their use became universal almost
immediately.
THE IMPROVED ARC LIGHT
About the time that Jablochkoff's candles were making such a sensation
in Europe, Charles F. Brush, of Cleveland, Ohio, invented an arc light
in which the carbons were set point to point, the distance being
maintained and the necessary feed produced automatically in much the
same manner as in the lamps used at present. Other inventions soon
followed, some of the lamps being regulated by clockwork, some by
electricity and magnetism.
The advantage of this type of arc lamp over the candle type--an
advantage that led to its general adoption--was largely that of
efficiency, a far greater amount of light being obtainable from the
same expenditure of power by the point-to-point type of lamp.
In this lamp it is necessary that the points of carbon shall come in
contact when the current is off, but be drawn apart a moment after the
current is turned on, and remain at this fixed distance. To accomplish
this, the lower carbon is usually made stationary, the feeding being
regulated by the position of the upper carbon. In the usual type of
modern lamp the passage of the current causes the points to separate
the required distance through the action of an electromagnet the coils
of which are traversed by the current. A clutch holds the carbon in
place, the position of this being also determined by an electromagnet.
The action is regulated by the difference in the resistance to the
passage of the current caused by the increase in the separation of the
points.
In the older type of arc lamp it was necessary to "trim" the lights by
replacing the carbons every day; but recently lamps have been perfected
in which the carbons last from one hundred to one hundred and twenty
hours. In these the arc is enclosed in a glass globe which is made as
nearly air-tight as possible with the necessary feed devices. This
closed chamber is fitted with a valve opening outward, which allows
the air to be forced out by the heat of the lamp, but does not admit a
return current. In this manner a rarefied chamber is produced in which
the carbons are oxidized very slowly; yet there is no diminution in the
brilliancy of the light.
Early in the history of electric lighting it became apparent that the
proper construction of the carbon electrodes was a highly important
item in the manufacture of a lighting apparatus. The value of carbons
depends largely upon their purity and freedom from ash in burning, and
it required a countless number of experiments to develop the highly
efficient carbons now in general use. Davy made use of pieces of wood
charcoal in his experiments, but these were too fragile to be of
practical value, even if their other qualities had been ideal. Later
experimenters tried various compounds, and in 1876 Carré in France
produced excellent carbons made of coke, lampblack, and syrup. From
these were developed the present carbons, usually made by mixing some
finely divided form of carbon, such as soot or lampblack made from
burning paraffin or tar, with gum or syrup to form a paste. Rods of
proper size and shape are made by forcing this paste through dies by
hydraulic pressure, subsequently baking them at a high temperature.
Sometimes they are given a coating of copper, a thin layer of the metal
being deposited upon them by electrolysis.
EDISON AND THE INCANDESCENT LAMP
The familiar incandescent electric-light bulb seems such a simple
apparatus to-day, being nothing apparently but a small wire enclosed in
an ordinary glass bulb, that it is almost impossible to realize what
an enormous amount of money, energy, and that particular quality of
mentality which we call "genius" has been required to produce it. First
and foremost among the names of the men of genius who finally evolved
this lamp is that of Thomas A. Edison; and only second to this foremost
name are those of Swan, Lane-Fox, and Hiram Maxim. But Edison's name
must stand preeminent; and there are probably very few, even among
Europeans, who would attempt or wish to deny him the enviable place as
the actual perfecter of the incandescent-light bulb.
[Illustration: THOMAS A. EDISON AND THE DYNAMO THAT GENERATED THE FIRST
COMMERCIAL ELECTRIC LIGHT.]
It is said that Edison first conceived the idea of an incandescent
electric light while on a trip to the Rocky Mountains in company
with Draper, in 1878. Be this as it may, he certainly set to work
immediately after completing this journey, and never relaxed or ceased
his efforts until a practical incandescent lamp had been produced. His
idea was to perfect a lamp that would do everything that gas could do,
and more; a lamp that would give a clear, steady light, without odor,
or excessive heat such as was given by the arc lights--in short, a
household lamp.
Early in his experiments he abandoned the voltaic arc, deciding that
a successful lamp must be one in which incandescence is produced by a
strong current in a conductor, the heat caused by the resistance to
the current producing the glow and light. But when search was made for
a suitable substance possessing the necessary properties to be the
incandescent material, the inventor was confronted by a vast array of
difficulties. It was of course essential that the substance must remain
incandescent without burning, and at the same time offer a resistance
to the passage of the current precisely such as would bring about
the heating that produced incandescence. It should be infusible even
under this high degree of heat, or otherwise it would soon disappear;
and it must not be readily oxidizable, or it would be destroyed as
by ordinary combustion. It should also be of material reducible to
a filament as fine as hair, but capable of preserving a rigid form.
These, among others, were the qualities to be considered in selecting
this apparently simple filament for the incandescent lamp. It was not a
task for the tyro, therefore, that Edison undertook when he began his
experiments for producing an "ideal lamp."
The substance in nature that seemed to possess most of the necessary
qualities just enumerated was the metal platinum, and Edison began
at once experimenting with this. He made a small spiral of very fine
platinum wire, which he enclosed in a glass globe about the size of an
ordinary baseball. The two ends of the wires connected with outside
conducting wires, which were sealed into the base of the bulb. The air
in the bulb had to be exhausted and a vacuum maintained to diminish the
loss of heat and of electricity and to prevent the oxidation of the
platinum. But when the current was passed through the spiral wire in
this vacuum a peculiar change took place in the platinum itself. The
gases retained in the pores of the metal at once escaped, and the wire
took on such peculiar physical properties that it was supposed for a
time by some physicists that a new metal had been produced. The metal
acquired a very high degree of elasticity and became susceptible of a
high polish like silver, at the same time becoming almost as hard as
steel. It also acquired a greater calorific capacity so that it could
be made much more luminous without fusing. To diminish the loss of
heat the wire was coated with some metallic oxide, and the slope of
the spiral also aided in this as each turn of the spiral radiated heat
upon its neighbor, thus utilizing a certain amount that would otherwise
have been lost. But despite all this, Edison found, after tedious
experimenting, that platinum did not fulfil the requirements of a
practical filament for his lamp; it either melted or disintegrated in a
short time and became useless; and the other experimenters had met with
the same obstacles to its use, and were forced to the same conclusion.
Some other substance must be found. The use of carbon for arc lights
and Edison's own experiments with carbon in his work on the telephone
naturally suggested this substance as a possibility. It is said that
this idea was brought forcibly to the inventor's attention by noticing
the delicate spiral of vegetable carbon left in his hand after using
a twisted bit of paper, one day, for lighting a cigar. This spiral of
carbon was, of course, too fragile to be of use in its ordinary form.
But it occurred to Edison that if a means of consolidating it could
be found, there was reason to hope that it would answer the purpose.
Experiments were begun at once, therefore, not only with processes of
consolidation but also with various kinds of paper, and neither effort
nor expense was spared to test every known variety of paper. Moreover,
many new varieties of paper were manufactured at great expense from
substances having peculiar fibres. One of these, made from a delicate
cotton grown on some little islands off South Carolina, gave a carbon
free from ash, and seemed to promise good results; but later it was
found that the current of electricity did not circulate through this
substance with sufficient regularity to get protracted and uniform
effects. Nevertheless, since many things pointed to this fibre carbon
as the ideal substance, Edison set about determining the cause of the
irregularity in the circulation of the current in the filament, and a
number of other experimenters soon became interested in the problem.
It was soon determined that the arrangement of the fibres themselves
were directly responsible for the difficulty. In ordinary paper the
fibres are pressed together without any special arrangement, like wool
fibres in felting. In passing through such a substance, therefore, the
current cannot travel along a continuous fibre, but must jump from
fibre to fibre, "like a man crossing a brook on stepping-stones." Each
piece of fibre constitutes a lamp or miniature voltaic arc, so that the
current is no longer a continuous one; and the little interior sparks
thus generated quickly destroy the filament. This discovery made it
apparent that such an artificial, feltlike substance as paper could not
be made to answer the purpose, and Edison set about searching for some
natural substance having fibres sufficiently long to give the necessary
homogeneity for the passage of the current.
For this purpose specimens of all the woods and fibre-substances of
all countries were examined. Special agents were sent to India, China,
Japan, South America, in quest of peculiar fibrous substances. The
various woods thus secured were despatched to the Edison plant at Menlo
Park and there carefully examined and tested. Without dwelling on the
endless details of this tedious task, it may be said at once that only
three substances out of all the mass withstood the tests reasonably
well. Of these, a species of Japanese bamboo was found to answer the
purpose best. Thus the practical incandescent lamp, which had cost so
much time, ingenuity, and money, came into existence, fulfilling the
expectation of the most sanguine dream of its inventor.
In using these bamboo carbon filaments the original spiral form of
filament was abandoned, the now familiar elongated horseshoe being
adopted, as the carbon could not be bent into the tortuous shapes
possible with platinum. Later various modifications in the shape of the
filament were made, usually as adaptations to changes in the shape of
the bulbs.
At the same time that Edison was succeeding with his bamboo carbon
filaments, J. W. Swan had been almost as successful with a filament
formed by treating cotton thread with sulphuric acid, thus producing a
"parchmentized thread," which was afterwards carbonized. A modification
of this process eventually supplanted the Edison bamboo filament; and
the filament now in common use--the successor of the "parchmentized
thread"--is made of a form of soluble cellulose prepared by dissolving
purified cotton wool in a solution of zinc chloride, and then pressing
the material out into long threads by pressing it through a die.
The long thread so obtained is a semi-transparent substance, resembling
catgut, which when carbonized at a high temperature forms a very
elastic form of carbon filament. To prepare the filament the cellulose
threads are cut into the proper lengths, bent into horseshoe shape,
double loops, or any desired form, and then folded round carbon formers
and immersed in plumbago crucibles. On heating these crucibles to a
high temperature the organic matter of the filaments is destroyed,
the carbon filaments remaining. These filaments are then ready for
attachment to the platinum leading-in wires, which is accomplished
either by means of a carbon cement or by a carbon-depositing process.
They are then placed in the glass bulbs and the wires hermetically
sealed, after which the bulbs are exhausted, tested, fitted with the
familiar brass collars, and are ready for use.
The combined discoveries of all experimenters had made it evident
that certain conditions were necessary to success, regardless of
the structure of the carbon filament. It was essential that the
vessel containing the filament should be entirely of glass; that the
current should be conveyed in and out this by means of platinum wires
hermetically sealed through the glass; and that the glass globe must
be as thoroughly exhausted as possible. This last requirement proved
a difficult one for a time, but by improved methods it finally became
possible to produce almost a perfect vacuum in the bulbs, with a
corresponding increase in the efficiency of the lamps.
THE TUNGSTEN LAMP
For twenty years the carbon-filament lamp stood without a rival.
But meanwhile the science of chemistry was making rapid strides and
putting at the disposal of practical inventors many substances hitherto
unknown, or not available in commercial quantities. Among these were
three metals, osmium, tantalum, and tungsten, and these metals soon
menaced the apparently secure position of the highly satisfactory,
although expensive, Edison lamp.
It will be recalled that the early experimenters had used two metals,
platinum and iridium, for lamp filaments; and that these two, although
unsatisfactory, were the only ones that had given even a promise
of success. But in 1898 Dr. Auer von Welsbach took out patents, and
in 1903 produced a lamp using an osmium filament. Its advent marked
the beginning of the return to metal-filament lamps, although the
lamp itself did not prove to be very satisfactory and was quickly
displaced by a lamp invented by Messrs. Siemens and Halske, having
a tantalum filament. On account of its ease to manufacture, its
brilliant light, and relatively low consumption of power, this lamp
gained great popularity at once, and for a single year was practically
without a rival. Then, in 1904, patents were taken out by Just and
Hanaman, Kuzel, and Welsbach, for lamps using filaments of tungsten,
and the superiority of these lamps over the tantalum lamps gave
them an immediate popularity never attained by either of the other
metal-filament lamps.
Needless to say there is good ground for this popularity, which may be
explained by the simple statement that the tungsten lamp gives more
light with much less consumption of power per candle power than any of
its predecessors. Unlike the carbon filament, which projects in the
familiar elongated horse-shoe loop, or double loop, into the exhausted
bulb, the tungsten filament is wound on a frame, so that several
filaments (usually eight or more) are used for producing the light
in each bulb. The chief defect of this lamp is the fragility of the
filament, which breaks easily when subjected to mechanical vibration.
On the other hand, tungsten lamps can be used in places at a long
distance from the central generating plant, where the electric current
is too weak for carbon-filament lamps.
THE MERCURY-VAPOR LIGHT OF PETER COOPER HEWITT
"On an evening in January, 1902, a great crowd was attracted to the
entrance of the Engineers' Club in New York city. Over the doorway
a narrow glass tube gleamed with a strange blue-green light of such
intensity that print was easily readable across the street, and yet
so softly radiant that one could look directly at it without the
sensation of blinding discomfort which accompanies nearly all brilliant
artificial lights. The hall within, where Mr. Hewitt was making the
first public announcement of his great discovery, was also illuminated
by the wonderful new tubes. The light was different from anything ever
seen before, grateful to the eyes, much like daylight, only giving the
face a curious, pale-green, unearthly appearance. The cause of this
phenomenon was soon evident; the tubes were seen to give forth all the
rays except red,--orange, yellow, green, blue, violet,--so that under
its illumination the room and the street without, the faces of the
spectators, the clothing of the women, lost all their shades of red;
indeed, changing the face of the world to a pale green-blue.
"The extraordinary appearance of this lamp and its profound
significance as a scientific discovery at once awakened a wide
public interest, especially among electricians who best understood
its importance. Here was an entirely new sort of electric light.
The familiar incandescent lamp, though the best of all methods of
illumination, is also the most expensive. Mr. Hewitt's lamp, though
not yet adapted to all the purposes served by the Edison lamp, on
account of its peculiar color, produces eight times as much light with
the same amount of power. It is also practically indestructible, there
being no filament to burn out; and it requires no special wiring. By
means of this invention electricity, instead of being the most costly
means of illumination becomes the cheapest--cheaper even than kerosene.
No further explanation than this is necessary to show the enormous
importance of this invention."
As just stated, the defect of the Edison incandescent lamp is its
cost, due to its utilizing only a small fraction of the power used
in producing the incandescence, and, of much less importance, the
relatively short life of the filament itself. Only about three per
cent. of the actual power is utilized by the light, the remaining
ninety-seven per cent. being absolutely wasted; and it was this
enormous waste of energy that first attracted the attention of Mr.
Hewitt, and led him to direct his energies to finding a substitute that
would be more economical. A large part of the waste in the Edison bulb
is known to be due to the conversion of the energy into useless heat,
instead of light, as shown by the heated glass. Mr. Hewitt attempted to
produce a light that would use up the power in light alone--to produce
a cool light, in short.
Instead of directing his efforts to the solids, Mr. Hewitt turned his
attention to gaseous bodies, believing that an incandescent gas would
prove the more nearly ideal substance for a cool light. The field of
the passage of electricity through gases was by no means a virgin
one, but was nevertheless relatively unexplored: and Mr. Hewitt was,
therefore, for the most part obliged to depend upon his own researches
and experiments. In these experiments hundreds of gases were examined,
some of them giving encouraging results, but most of them presenting
insurmountable difficulties. Finally mercury vapor was tried, with the
result that the light just referred to was produced.
The possibilities of mercury-vapor gas had long been vaguely
suspected--suspected, in fact, since the early days of electrical
investigation, two centuries before. The English philosopher, Francis
Hauksbee, as early as 1705 had shown that light could be produced by
passing air through mercury in an exhausted receiver. He had discovered
that when a blast of air was driven up against the sides of the glass
receiver, it appeared "all round like a body of fire, consisting of an
abundance of glowing globules," and continuing until the receiver was
about half full of air. Hauksbee called this his "mercurial fountain,"
and although he was unable to account for the production of this
peculiar light, which he remarked "resembled lightning," he attributed
it to the action of electricity.
Between Hauksbee's "mercurial fountain" and Hewitt's mercury-vapor
light, however, there is a wide gap, and, as it happened, this gap
is practically unbridged by intermediate experiments, for Mr. Hewitt
had never chanced to hear anything of Hauksbee's early experiments,
or of any of the tentative ones of later scientists. But this, on the
whole, may have been rather advantageous than otherwise, as, being
ignorant, he was perhaps in a more receptive state of mind than if
hampered by false or prejudicial conceptions. Be this as it may, he
began experimenting with mercury confined in a glass tube from which
the air had been exhausted, the mercury being vaporized either by
heating, or by a current of electricity. No results of any importance
came of his numerous experiments for a time, but at last he made the
all-important discovery that once the high resistance of the cold
mercury was overcome, a comparatively weak current would then be
conducted, producing a brilliant light from the glow of the mercury
vapor. Here, then, was the secret of the use of mercury vapor for
lighting--a powerful current of electricity for a fraction of a second
passed through the vapor to overcome the initial resistance, and then
the passage of an ordinary current to produce the light.
In practice this apparent difficulty in overcoming the initial
resistance with a strong current is easily overcome by the use of a
"boosting coil," which supplies the strong current for an instant, and
is then shut off automatically, the ordinary current continuing for
producing the light. The mechanism is hardly more complex than that of
the ordinary incandescent light, but the current of ordinary strength
produces an illumination about eight times as intense as the ordinary
incandescent bulb of equal candle-power.
The form of lamp used is that of a long, horizontal tube suspended
overhead in the room, a brilliant light being diffused, which, lacking
the red rays of ordinary lights, gives a bluish-green tone to objects,
and a particularly ghastly and unpleasant appearance to faces and
hands, as referred to a moment ago. In many ways this feature of the
light is really a peculiarity rather than a defect, and for practical
purposes in work requiring continued eye-strain the absence of the
red rays is frequently advantageous. In such close work as that of
pen-drawing, for example, some artists find it advantageous to use
globes filled with water tinted a faint green color, placed between
the lamps and their paper, the effect produced being somewhat the same
as that of the mercury-vapor light. For such work the absence of the
red rays of the Hewitt light would not be considered a defect; and in
workshops and offices where Mr. Hewitt's lamps are used the workmen
have become enthusiastic over them.
On the other hand, the fact that the color-values of objects are so
completely changed makes this light objectionable for ordinary use;
so much so, in fact, that the inventor was led to take up the problem
of introducing red rays in some manner so as to produce a pure white
light. He has partly accomplished this by means of pink cloth colored
with rhodium thrown around the glass; but this causes a distinct loss
of brilliancy.
The most natural method of introducing the red rays, it would seem,
would be to use globes of red glass; but a moment's reflection will
show that this would not solve the difficulty. Red glass does not
change light waves, but simply suppresses all but the red rays; and
since there are no red rays in the mercury-vapor light the result of
the red globe would be to suppress all the light. Obviously, therefore,
this apparently simple method does not solve the difficulty; but those
familiar with Mr. Hewitt's work will not be surprised any day to hear
that he has finally overcome all obstacles, and produced a perfectly
white light. In the meantime the relatively expensive arc light and
the incandescent bulb with its filament of carbon or metal hold
unchallenged supremacy in the commercial field.
XII
THE MINERAL DEPTHS
Ages before the dawn of civilization, primitive man had learned to
extract certain ores and metals from the earth by subterranean mining.
Such nations as the Egyptians, for example, understood mining in most
of its phases, and worked their mines in practically the same manner as
all succeeding nations before the time of the introduction of the steam
engine. The early Britons were good miners and the products of their
mines were carried to the Orient by the Phoenicians many centuries
before the Christian era. The Romans were, of course, great miners, and
remains of the Roman mines are still in existence, particularly good
examples being found in Spain.
Even the aborigines of North America possessed some knowledge of
mining, as attested by the ancient copper mines in the Lake Superior
region, although by the time of the discovery of America, and probably
many centuries before, the interloping races of Indians who had driven
out or exterminated the Lake Superior copper mines had forgotten the
art of mining, if indeed they had ever learned it. But the fact that
their predecessors had worked the copper mines is shown by the number
of stone mining implements found in the ancient excavations about Lake
Superior, these implements being found literally by cart loads in some
places.
The great progress in mining methods, however, as in the case of most
other mechanical arts, began with the introduction of steam as a means
of utilizing energy; and another revolution is in rapid progress owing
to the perfection of electrical apparatus for furnishing power, heat,
and light. Methods of mining a hundred years ago were undoubtedly
somewhat in advance of the methods used by the ancients; but the
gap was not a wide one, and the progress made by decades after the
introduction of steam has been infinitely greater than the progress
made by centuries previous to that time.
This progress, of course, applies to all kinds of mines and all phases
of mining; but steam and electricity are not alone responsible for
the great nineteenth-century progress. Geology, an unknown science
a century ago, has played a most active and important part; and
chemistry, whose birth as a science dates from the opening years of the
nineteenth century, is responsible for many of the great advances.
Obviously a very important feature of any mine must be its location,
and the determination of this must always constitute the principal
hazard in practical mining. Prospecting, or exploring for suitable
mining sites, has been an important occupation for many years, and
has in fact become a scientific one recently. Formerly mines were
frequently stumbled upon by accident, but such accidental discoveries
are becoming less and less frequent. The prospector now draws largely
upon the knowledge of the scientist to aid him in his search. Geology,
for example, assists him in determining the region in which his mines
may be found, if it cannot actually point out the location for sinking
his shaft; and at least a rough knowledge of botany and chemistry
is an invaluable aid to him. It is obvious that it would be useless
to prospect for coal in a region where no strata of rocks formed
during the Carboniferous or coal-forming age are to be found within a
workable distance below the surface of the earth. The prospector must,
therefore, direct his efforts within "geological confines" if he would
hope to be successful, and in this he is now greatly aided by the
geological surveys which have been made of almost every region in the
United States and Europe.
An example of what science has done in this direction was shown a few
years ago in a western American town during one of the "oil booms"
that excited so many communities at that time. In the neighborhood
of this town evidences of oil had been found from time to time--some
of them under peculiar and suspicious circumstances, to be sure--and
the members of the community were in an intense state of excitement
over the possibility of oil being found on their lands. Prices of land
jumped to fabulous figures, and the few land-owners that could be
induced to part with their farms became opulent by the transactions. An
"oil expert" appeared upon the scene about this time--just "happening
to drop in"--who declared, after an examination, that the entire region
abounded in oil. He backed up his assertion by offering to stake his
experience against the capital of a company which was formed at his
suggestion. Before any wells were actually started, however, a prudent
member of the company consulted the State geologist on the subject,
receiving the assurance that no oil would be found in the neighborhood.
Strangely enough the word of the man of science triumphed over that of
the "oil expert," and although some tentative borings were made on a
minor scale, no great amount of money was sunk. It developed afterwards
that the evidences of oil found from time to time had been the secret
work of the "expert."
In general, prospecting for oil differs pretty radically from
prospecting for most other minerals. A very common way of locating an
ore-mine is by the nature of the out-crop,--that is, the broken edges
of strata of rocks protruding from hillsides, or tilted at an angle on
level areas. If the ore-bearing vein is harder than the surrounding
strata it will be found as a jutting edge, protruding beyond the
surface of the other layers of rocks which, being softer, are more
easily worn away. On the other hand, if this stratum is soft or
decomposable it will show as a depression, or "sag" as it is called. Of
course such protrusions and depressions may only be seen and examined
where the rocks themselves are exposed; vegetation, drift, and snow
preventing such observations. But the vegetation may in itself serve
as a guide to the experienced prospector in determining the location
of a mine, peculiar mineral conditions being conducive to the growth
of certain forms of vegetation, or to the arrangement of such growth.
Alterations in the color of the rocks on a hillside are also important
guides, as such discolorations frequently indicate that oxidizable
minerals are located above.
In hilly or mountainous regions, where the underlying rocks are covered
with earth, portions of these surfaces are sometimes uncovered by the
method known as "booming." In using this method the prospector selects
a convenient depression near the top of a hill and builds a temporary
dam across the point corresponding to the lowest outlet. When snow and
rain have turned the basin so formed into a lake, the dam is burst
and the water rushing down the hillside cuts away the overlying dirt,
exposing the rocks beneath. This method is effective and inexpensive.
The beds of streams, particularly those in hilly and mountainous
regions, are fertile fields for prospecting, particularly for precious
metals. Stones and pebbles found in the bed are likely to reveal the
ore-foundations along the course of the stream, and the shape of
these pebbles helps in determining the approximate location of such
foundations. An ore-bearing pebble, well worn and rounded, has probably
traveled some little distance from its original source, being rounded
and worn in its passage down the stream. On the other hand, if it is
still angular it has come a much shorter distance, and the prospector
will be guided accordingly in his search for the ore-vein.
But prospecting is not limited to these simple surface methods. In
enterprises undertaken on a large scale, borings are frequently made
in regions where there are perhaps no specific surface indications.
In such regions a shaft may be sunk or a tunnel may be dug, and the
condition of the underlying strata thus definitely determined. This
last is, of course, a most expensive method, the simpler and more usual
way being that of making borings to certain depths. The difficulty with
such borings is that rich veins may be passed by the borer without
detection; or, on the other hand, a small vein happening to lie in the
same plane as the drill may give a wrong impression as to the extent of
the vein.
One of the most satisfactory ways of making borings is by means of the
diamond drill. This drill is made in the form of a long metal tube,
the lower edge of which is made into a cutting implement by black
diamonds fixed in the edge of the metal. By rotating this tube a ring
is cut through the layers of rock, the solid cylinder or core of rock
remaining in the hollow centre of the drill. This can be removed from
time to time, the nature and thickness of the geological formation
through which the drill is passing being thus definitely determined.
CONDITIONS TO BE CONSIDERED IN MINING
Three great problems always confront the mine operator--light, power,
and ventilation. Of these ventilation is the most important from the
workman's standpoint, although the problem of light is scarcely
less so. Obviously a cavity of the earth where hundreds of men are
constantly consuming the atmosphere and vitiating it, and where
thousands of lights are burning, would become like the black hole of
Calcutta in a few minutes if some means were not adopted to relieve
this condition. But besides this vitiation of the atmosphere caused by
the respiration of the men and the burning of lamps there are likely
to be accumulations of poisonous gases in mines, that are even more
dangerous. Of the two classes of dangerous gases--those that asphyxiate
and those that explode or burn--it may be said in a general way that
the suffocating or poisonous gases, such as carbonic acid, which is
known as black damp, or choke damp, are more likely to occur in ore
mines, while the explosive gases are found more frequently in coal
mines.
Choke damp, which is a gas considerably heavier than the atmosphere,
is usually found near the bottom of mines, running along declines and
falling into holes in much the same manner as a liquid. It kills by
suffocation, and, as it will not support combustion, it may be detected
by lowering a lighted candle into a suspected cavity, the light being
extinguished at once if the gas is present. To rid the cavity of it,
forced ventilation is used where possible, the gas being scattered by
draughts of fresh air. If this is impracticable, and the cavity small,
the choke damp may be dipped out with buckets.
But the problem of the mining engineer is not so much to rid cavities
of gas as to prevent its accumulation. In modern mining, with proper
ventilation and drainage, there is comparatively little danger of
extensive accumulation of this gas.
[Illustration: A FLINT-AND-STEEL OUTFIT, AND A MINER'S STEEL MILL.
The upper picture shows a flint-and-steel outfit, the implements for
lighting a fire before the days of matches. The lower picture shows a
miner's steel mill, which was used for giving light in mines before the
day of the safety-lamp. It consists of a steel disk which is rotated
rapidly against a piece of flint, producing a stream of sparks. It was
thought that such sparks would not ignite fire-damp--a belief which is
now known to be erroneous.]
The danger from this choke damp, therefore, is one that concerns the
individual workman rather than large bodies of men or the structure of
the mine itself. With fire damp, however, the case is different, as an
explosion of this gas may destroy the mine itself and all the workmen
in it. It is, therefore, the most dreaded factor in mining, and is the
one to which more attention has been directed than to almost any other
problem.
This fire damp is a mixture of carbonic oxide and marsh gas which,
being lighter than air, tends to rise to the upper part of the mines.
For this reason explosions are more likely to occur near the openings
of the mine, frequently entombing the workmen in a remote part of the
mine even when not actually killing them by the explosion. As this gas
is poisonous as well as explosive the miners who survive the explosion
may succumb eventually to suffocation.
Previous to the year 1816 no means had been devised for averting the
explosions of fire damp except the uncertain one of watching the flame
of the candle with which the miner was working. On coming in contact
with air mildly contaminated with fire damp the candle flame takes
on a blue tint and assumes a peculiarly elongated shape which may be
instantly detected by a watchful workman. But miners were, and still
are, a proverbially careless class of men even where a matter of life
and death is concerned, and too frequently gave no heed to the warning
flame. But in 1816 Sir Humphrey Davy invented his safety lamp, a
device that has been the means of saving thousands of lives, and which
has not as yet been entirely supplanted by any modern invention.
In making his numerous experiments, Davy had observed that iron-wire
gauze is such a good conductor of heat that a flame enclosed in
such gauze could not pass readily through meshes to ignite a gas on
the outside. He found by experiment that a considerable quantity of
explosive gas might be brought into contact with the gauze surrounding
a flame, and no explosion occur. At the same time this gas would give
warning of its presence by changing the color of the flame. When a
lamp was made with a surrounding gauze having seven hundred and eighty
meshes to the square inch, it was found to give sufficient light and
at the same time to be practically non-explosive in the presence of
ordinary quantities of gas.
One would suppose that such a life-saving invention would have been
eagerly adopted by the men whose lives it protected; but, as a matter
of fact, owing to certain inconveniences of Davy's lamps, many miners
refused to use them until forced to do so by the mine-owners. One
of these disadvantages was that this safety lamp gave a poor light
overhead. This is particularly annoying to the miner, who wishes always
to watch the condition of the ceiling under which he is working. When
not under constant observation, therefore, a miner would frequently
remove the gauze of the lamp and work by the open flame, regardless
of consequences. Or again, he would sometimes forgetfully use the
flame for lighting his pipe. To overcome the possibility of such
forgetfulness or wilful disobedience, it was found necessary to equip
safety lamps with locking devices, so that the miner had no means of
access to the open flame of his lamp once it had been lighted.
Since the time of the first Davy safety lamp there have been numerous
improvements in mechanical details, although the general principle
remains unchanged. One of these improvements is a device whereby the
lamp, when accidentally extinguished, may be relighted without opening
it, and without the use of matches. This is done by means of little
strips of paper containing patches of a fulminating substance which
is ignited by friction, working on the same principle as the paper
percussion caps used on toy pistols.
But even the improved safety lamp seems likely to disappear from mines
within the next few years, now that electricity has come into such
general use. As yet, however, no satisfactory portable electric lamp
or lantern has been perfected, such lamps being as a rule too heavy,
expensive, and unreliable. Even if these defects were remedied, the
advantage would still lie with the Davy lamp, since the electric lamp,
being enclosed, cannot be used for the detection of fire damp. But
this advantage of the safety lamp is becoming less important, since
well-regulated mines are now more thoroughly ventilated, and the danger
from fire damp correspondingly lessened.
In some Continental mines the experiment has been tried of constantly
consuming the fire damp, before it has had time to accumulate in
explosive quantities, by means of numerous open lights kept constantly
burning. This method is effective, but since the numerous lights
consume the precious oxygen of the air as well as the damp, the method
has never become popular. Obviously, then, the question of mine
ventilation is closely associated with that of lighting.
Probably the simplest method of properly ventilating a mine is that of
having two openings at the surface, one on a much higher level than
the other if the mine is on a hillside, the lower one corresponding to
the lowest portion of the mine where possible. By such an arrangement
natural currents will be established, and may be controlled and
distributed through the mine by doors or permanent partitions, or aided
by fans. But of course only a comparatively small number of mines are
so situated that this system can be used.
It is possible, of course, to ventilate a mine from a single shaft or
opening by use of double sets of pipes, one for admitting air and the
other for expelling it; but this system is obviously not an ideal one,
and is prohibited by law in most mining districts. Such laws usually
stipulate that there must be at least two openings situated at some
distance from each other.
The older method of creating air currents was by means of furnaces,
but this method, while very effective, is expensive and dangerous. In
using this system a furnace is built near the outlet of the air shaft,
the combustion of the fuel creating the necessary draught. But in the
nature of things this furnace is a constant menace to the mine, besides
being an extremely wasteful expenditure of energy. The modern method
of ventilating is by means of rotary fans, the electric fan having
practically solved the problem. The air currents established by such
fans are controlled either by the doors in the passages, or by means of
auxiliary fans. In addition, jets of compressed air are sometimes used,
and have become very popular.
Another important problem that constantly confronts the mining engineer
is that of drainage. Mines are, of course, great reservoirs for the
accumulation of water, which must be drained or pumped out continually;
and as the shafts are sunk deeper and deeper it becomes increasingly
difficult to raise the water to the surface. Special means and
machinery are employed for this purpose which will be considered more
in detail in a moment.
ELECTRIC MACHINERY IN MINING
Electricity is, of course, the great revolutionary factor in modern
mining. There is scarcely a department of mining in which electric
power has not wrought revolutionary changes in recent years; and the
subject has become so important and so thoroughly specialized as to
"create a literature and a technology of its own." From the electric
drill, working hundreds of feet below the surface of the earth, to the
delicate testing-instruments in the laboratory of the assaying offices,
the effect of this electrical revolution is being felt progressively
more and more every year.
Moreover, electricity, on account of its transmutability, has made
accessible many important mining sites hitherto unworkable. Rich mines
are now in operation on an economical basis which, thirty years ago,
were worthless on account of their isolation. When such mines were
situated in mountainous regions where there was no coal supply at hand
for creating steam power, and where the only available water power was
perhaps several miles away, operations on a paying basis were out of
the question before the era of electric power.
At present, however, the question of distance of the seat of power
has been practically eliminated by the possibilities of electric
conduction. A stream, situated miles away, when harnessed to a turbine
and electric motors may afford a source of power more economical than
could be furnished a few years ago by a power plant supplied with
fuel at the very door of the mine. We need not enter into the details
of this transmission of power, however, since the subject has been
discussed in a general way in another place. Our subject here is
rather to deal with the application of electricity to certain mining
implements of special importance.
One of the most useful acquisitions to the equipment of the modern
miner is a portable mechanical drill, which makes it possible for
him to dispense with the time-honored pick, hammer, and hand-drill.
But it is only recently that inventors have been able to produce
this implement. The great difficulty has lain in the fact that a
reciprocating motion, which is essential for certain kinds of drilling,
is not readily secured with electric power. The use of steam or
compressed air for operating such reciprocating drills presents no
mechanical difficulties, and the fact that power of this kind can be
transmitted long distances by the use of flexible tubes made such
drills popular for several years. But the cost of operating such drills
is so much greater than that of the new electric drills that they are
rapidly being replaced in mining work.
The first attempts to produce an electric drill with a reciprocating
motion were so unsuccessful that inventors turned their attention to
perfecting some rotary device. This proved more successful, and rotary
drills, operating long augers and acting like ordinary wood-boring
machines, are now used extensively for certain kinds of drilling. The
more recent forms perform the same amount of work as the air drill,
with a consumption of about one-tenth the power. Moreover, none of
the energy is lost at high altitudes as in the case of air drills,
and they are not affected by low temperatures which sometimes render
the air drill inoperable. On the other hand, the air drill is a hardy
implement, capable of withstanding very rough usage, whereas the
electric drill is probably the more economical, as well as the more
convenient drill of the two.
In certain kinds of mining, such as in the potash mines of Europe and
the coal mines of America, these electric drills operating their long
augers have been found particularly useful. The ordinary type of drill
is so arranged that it can be operated at any angle, vertically or
horizontally. The lighter forms are mounted on upright stands, with
screws at the ends for fastening to the floor and roof, although the
heavier types are sometimes mounted on trucks. The motor, which is
not much larger or heavier than an ordinary fan motor, is fastened to
the upright and is from four to six horse-power. This connects with a
flexible wire which transmits the power from the generating station,
frequently several miles away. The auger, which is about the largest
part of the machine and entirely out of proportion to the little motor
that drives it, is simply a long bar of steel, twisted spirally at the
cutting-end like an ordinary wood auger.
From the workman's standpoint these rotary drills are infinitely
superior to reciprocating or percussion drills, where the constant
jarring of the machine, besides being extremely tiresome, sometimes
produces the serious disease known as neuritis. Various means have
been attempted to prevent this, such as by overcoming the jar in a
measure by flexible levers which do not transmit the vibrations to the
hands and arms; but such attempts are only partially successful, and
a certain amount of jarring cannot be avoided. In the rotary electric
drills there is none of this, the workmen simply controlling the drill
and the motor with levers, and receiving at most only a slight jar from
the vibrations of the auger.
TRACTION IN MINING
In recent years electric traction engines for use in mines have been
rapidly replacing horse-and mule-power, and have become important
economic factors in mining operations. The pioneer of this type of
locomotive seems to have been one built by Mr. W. M. Schlessinger
for one of the collieries of the Pennsylvania Railroad about 1882,
and which has remained in active use ever since. The total weight of
this locomotive was five tons and it was equipped with thirty-two
horse-power electric motors. The current was supplied through a trolley
pole which took the current from a T-shaped rail placed above and at
one side of the track. The train hauled by this locomotive consisted of
fifteen cars, carrying from two to three tons of coal each.
Following this first mining-locomotive a great number were quickly
produced. In Pennsylvania alone something like four hundred are now
in use, and in Illinois two million tons of coal were hauled in this
manner in twelve mines in 1901. It was estimated at the beginning of
the present century that some 3,000 electric locomotives specially
built for mining were in use in the United States alone.
The earlier types of mining-locomotives were much higher and bulkier
than those of more recent construction, the motors being mounted above
the trucks and geared downward. Very soon, however, the "turtle-back"
or "terrapin-back" type was developed, with the motors brought close
to the ground, so that even quite a heavy locomotive might not be
much higher than the diameter of its driving-wheels. When these
queer-looking machines were boxed in so that even the wheels were
covered, they lost all resemblance to locomotives or vehicles of any
kind, appearing like low, rectangular metal boxes placed upon the car
tracks, that glided along the rails in some mysterious manner. The
presence of the trolley pole helped to dispel this illusion, but in
some instances this is wanting, the power being taken from a third rail.
With these locomotives, some of them not more than two and a half
feet high, it was possible to haul trains even in very low and narrow
passages--much lower, in fact, than could be entered by the little
mules used in former years. This in itself was revolutionary in its
effects, as many thin veins were thus made workable.
This type of low locomotive is the one that has come into general use
throughout the world. Such locomotives range in size from two to twenty
tons, with wheel gauges from a foot and a half wide to the standard
railway gauge of four feet, eight and a half inches. Locomotives
weighing more than twenty tons are not in general use on account of the
small size of the mine entrances.
In the ordinary types the motorman sits in front, controlling the
locomotive with levers and mechanical brakes placed within easy reach,
but sunk as low as possible. As a rule, the motors are geared to the
truck axles, either inside or outside the locomotive frame. An overhead
copper wire supplies the current by contact with a grooved trolley
wheel mounted on the end of the regulation trolley pole. An electric
headlight is used, and the ordinary speed attained by the compact
motors is from six to ten miles an hour.
The amount of work that can be performed by one of these little,
flat, box-like locomotives is entirely out of proportion to its size.
A 10-ton locomotive in a Pennsylvania mine hauled about 150,000
tons of coal in a year at a cost of less than one-tenth of a cent per
ton for repairs. The usual train was made up of thirty-five cars,
each loaded with about 3,700 pounds of coal, which was hauled up a
three-per-cent grade. The cost of such haulage was only about 2.76
cents per ton, as against 7.15 cents when hauled by mule-power. These
figures may be considered representative, as other mines show similar
results.
[Illustration: THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN COLLIERY
TROLLEY.
This locomotive was constructed in 1813 at Wylam Colliery, England,
by William Hedley. It was entirely successful, and was in operation
for almost half a century, up to the time of its removal in 1862 to
the South Kensington Museum. The vertical cylinders and arrangement of
walking beams for transmitting power are particularly interesting. The
power was transmitted through cogged wheels to the rear axle, as is
done with modern automobiles.]
A particular advantage has been gained by the use of electric
locomotives over older methods in the process of "gathering" the cars.
In many coal mines, even when the main hauling is done by electricity,
the gathering or collecting of cars from the working faces of the rooms
was formerly done either by mule-power or by hand. In some low-veined
mines, hand power alone was used, on account of the low roof.
In such places, low, compressed-air locomotives were sometimes used;
but these were very expensive. These have now been very generally
replaced by "turtle-back" electric locomotives, operated at a distance
from the main trolley wire by means of long, flexible cables, so geared
that they can be paid out or coiled as desired.
On the main line these locomotives take the current from the trolley
wire by means of the trolley pole, but when the place for gathering is
reached, the connection is made by means of the flexible cable, and the
trolley pole fastened down so as not to be in the way. This allows the
locomotive to push the little cars into the rooms far removed from the
main line, with passages too low and narrow to allow the use of the
trolley pole. By the time the last cars have been delivered the first
cars of the train have been filled, and the process of gathering may be
begun at once, and the loaded train made up for the return trip. With
such a locomotive two men can distribute and gather up from one hundred
to one hundred and twenty cars in an ordinary eight-hour working-day,
hauling from three hundred to three hundred and fifty tons of coal.
In certain regions, a system of third-rail current-supply is used, this
rail being also a tooth rail with which a cog on the locomotive works
frictionally. For climbing steep grades this system of cogged rails has
many advantages over other systems.
Another type of electric locomotive used in some mines is a
self-propelling or automobile one equipped with storage batteries. Such
locomotives do away with the inconvenience and dangers of contact rails
or trolley wires, but are heavy and expensive. A compromise locomotive,
particularly useful for gathering, is one equipped with both trolley
pole and storage batteries. This locomotive is so made that the storage
batteries are charged while it is running with the trolley connection,
so that no time is lost in the charging process. Such locomotives
have been found very satisfactory for many purposes, and but for the
imperfections common to all storage batteries would be ideal in many
ways. They can be worked over any improvised track, regardless of
distance, which is an advantage over the flexible-cable system where
distances are limited by the length of cable; and the first cost of
the battery is no more than the outlay on trolley wires and supports.
It is also claimed that the cost of maintenance is relatively low, but
it is doubtful if it equals the trolley or third-rail systems in this
respect.
Closely allied to the systems of traction by electric locomotives, is
the modern electric telpherage system. Until quite recently the haulage
of ores and other raw materials used in mining, when done aerially,
has been by means of travelling rope or cable. When distances to be
travelled in this manner are short, such as across streams or valleys,
where no supports are used, the term "cableway" is generally applied;
but where the distance is so long that supports are necessary, the term
"tramway cable" is used. It is to these longer systems that electric
telpherage is particularly applicable.
The advantage of such an electric system over the older method is
the same as the advantages of the trolley road over the cable, all
ropes and cables being stationary, the electric motor, or "telpher,"
travelling along on one cable and taking its current by means of a
trolley pole from a wire above. For heavier work metal rails supported
between posts are employed in place of a flexible cable, and over such
systems loads of several tons can be hauled.
Such an electric telpher system is used in one of the Cuban limestone
quarries, the telpher and cars travelling a long distance upon cables,
except at some of the curves, where solid rails are substituted,
hauling a load of a thousand pounds at a speed of from twelve to
fifteen miles an hour. The current comes from a distant source, and the
telpher is so arranged that it travels automatically when the current
is turned on, stopping when the current is cut off. This is quite a
common arrangement for smaller telphers, but in the larger ones a man
travels with the telpher and load, controlling the train just as in the
case of the ordinary trolley system.
The various processes of hoisting in mines by electricity is closely
akin to that of traction, since, after all, "an elevator is virtually a
railway with a 100-per-cent grade." As such work is done spasmodically,
long periods of rest intervening between actual periods of work, a
great deal of energy is wasted by steam hoisting engines, where a
certain pressure of steam in the boiler must be maintained at all
times. For this reason electrical energy for hoisting has come rapidly
into popularity in recent years. "The throttling of steam to control
speed," said Mr. F. O. Blackwell in addressing the American Institute
of Mining Engineers, "the necessity for reversing the engine, the
variation in steam pressure, the absence of condensing apparatus, the
cooling and large clearance of cylinders, and the condensation and
leakage of steam pipes when doing no work, are all against the steam
hoisting engine. One of the largest hoisting engines in the world was
recently tested and found to take sixty pounds of steam per indicated
horse-power per hour. The electric motor, on the other hand, is ideal
for intermittent work. It wastes absolutely no energy when at rest,
there being no leakage or condensation. Its efficiency is high, from
one-quarter load to twice full load."
There seems to be practically no difference as far as the element of
danger is concerned between steam and electric hoists. The difference
is largely one of economy. The importance of this is shown by the
recent comparisons in a gold mine which has replaced its steam
apparatus by electricity. In this mine the hoist moves through the
shaft at a rate of over twelve hundred feet per minute, elevating five
hundred tons of ore daily on double-decked cages. It is estimated that
this system shows an efficiency of 75 per cent, taking into account
losses of all kinds, with a resulting reduction of cost of from seven
to twenty dollars per horse-power per month.
Results comparing very favorably with these have been obtained also
in some of the mines in Germany and Bohemia, where electricity has
been introduced extensively in mining. In one of these mines the daily
hoisting capacity is twenty-seven hundred tons from a depth of over
sixteen hundred feet, at a speed of over fifty-two feet per second. In
the Comstock mine, at Virginia City, Nev., electric hoists are used
which obtain their power from a plant situated on the Truchee River
thirty-two miles away.
ELECTRIC MINING PUMPS
In pumping, which is always one of the important items in mining, the
use of electric power has been found quite as advantageous as in the
other fields of its application. No special features are embodied in
most of the types of mining pumps over the rotary and reciprocating
types used for ordinary purposes, except perhaps a type of pump known
as the sinking pump. This is a movable pump that can be easily lowered
from one place to another, and has proved to be a great time-saver over
steam or air pumps used for similar purposes.
For some time the question of the durability of electric pumps was in
dispute, but developments in quite recent years seem to prove that, in
some instances at least, such pumps are practically indestructible.
"The question of what would happen to an electric motor in a mine
if pumps and motors get flooded has often come up. From tests made
recently at the University of Liège, Belgium, it appears that a
suitably designed polyphase alternating-current motor of a type largely
used on the continent of Europe was completely submerged in water.
It was run for a quarter of an hour; it was then stopped and allowed
to remain submerged, under official seal, for twenty-four hours, at
the end of which time it was again run for a few minutes. It was next
removed from the water, again put under seal, and left to dry for
twenty-four hours. The insulation was then tested, and the motor was
found to be in perfect order. It would be hard to imagine a test more
severe than this.
"As bearing upon this question it is interesting to note that among
the pumps in use around Johannesburg, South Africa, at the beginning
of the Anglo-Boer War, there were twelve of a well-known American
make, each of which was operated by a 50-horse-power induction motor
of American construction with three 15-kilowatt transformers. When the
mines were shut down, upon the breaking out of the war, the water
rose so rapidly that it was impossible to remove the pumps, motors,
transformers, etc., and consequently they remained under 500 to 1,000
feet of water. Two and a half years later, when peace was declared in
South Africa, the water in the shaft was pumped out and the electrical
apparatus was removed to the surface. Three of the motors were stripped
and completely rewound, but to the general surprise of the experts the
condition of the insulation indicated that the rewinding might not be
absolutely necessary. Accordingly the other nine motors were thoroughly
dried in an oven and then soaked in oil. After this treatment they were
rigidly tested, proved to be all right, and were at once restored to
regular service in the mine. The transformers were treated in the same
manner as the motors, with equally gratifying results.
"An interesting illustration of the flexibility and adaptability of
electric motors for pumping purposes is furnished by the Gneisenau
mine, near Dortmund, Germany, where a very large electric mining plant
was installed in 1903. In this instance the pump is located more than
1,200 feet below the surface, and the difficulties of installing the
apparatus were so great, on account of the small cross section of the
shaft, that it was necessary to build up the motor in the pumping
chamber, the material being transported through the wet shaft and the
winding of the coils being performed _in situ_.
"An interesting use of the electric pump associated with the telephone
in connection with mining is noted by Mr. W. B. Clarke. In one coal
mine, where an electric pump is located in a worked-out portion of the
mine, the circuits are so arranged that the pump is started from the
power house, some distance away. Near the pump is placed a telephone
transmitter connected to a receiver in the power house. To start the
motors, or to ascertain whether the pumps are working properly, the
engineer merely listens at the telephone receiver, without leaving his
post."
ELECTRICITY IN COAL MINING
In coal mining the effect of the use of electrical machinery has been
revolutionary in recent years, particularly in the development of
electric coal cutters. The old method of picking out coal by hand,
where the miner labored with the heavy pick, working in all manner of
cramped and dangerous positions, was supplanted a few years ago by
the "puncher" machine, worked by steam or compressed air. With these
machines the coal was picked out just as in the case of the hand
method, except that the energy was derived from some power other than
muscular. So that while these machines worked more rapidly than the
hand picks, they utilized the same general principle in applying their
energy.
Within recent years, however, various coal-cutting machines have been
devised, with which the coal was actually cut, or sawed out, these
machines being peculiarly well adapted to using the electric current.
The most practical and popular form of machine is one in which the
sawing is done by an endless chain, the links of which are provided
with a cutting blade. These have been very generally replacing the
compressed-air or pick type of machine, and their popularity accounts
largely for the enormous increase in the use of coal-mining machinery
during the past decade. Thus in 1898 there were 2,622 coal-mining
machines in use in the United States. Four years later this number had
more than doubled, the increase being due largely to the adoption of
chain machines.
Like electric locomotives, and for similar reasons, the coal-cutting
machines are low, broad, flat machines, from eighteen to twenty-eight
inches high. They rest upon a flat shoeboard that can be moved
easily along the face of the coal. An ordinary machine weighs in the
neighborhood of a ton, and requires two men to operate. The apparatus
is described briefly as follows:
"On an outside frame, consisting of two steel channel bars and two
angle irons riveted to steel cross ties, rests a sliding frame
consisting of a heavy channel or centre rail, to which is bolted the
cutter head. The cutter head is made entirely of two milled steel
plates, which bolt together, forming the front guide for the cutter
chain. This chain, which is made of solid cast steel links connected
by drop forge straps, is carried around idlers or sprockets placed at
each end of the cutter head and along the chain guides at the side to
the rear of the machine, where it engages with and receives its power
from a third sprocket, under the motor. The electric motor, which is
of ironclad multipolar type, rests upon a steel carriage, which forms
the bearing for the main shaft.... A reversing switch is provided, so
that the truck can travel in either direction, and when the machine has
reached its stopping point, either forward or backward, it is checked
by an automatic cut-off. The return travel is made in about one-fourth
of the time required to make the cut."
In veins of coal of a thickness from twenty-eight to thirty inches,
such a machine will cut about one hundred tons of coal in a day. The
cost of production with such machines has been estimated at about
sixty-three cents a ton, as against ninety cents as the cost of pick
mining in rooms,--a saving of about twenty-seven cents a ton. Since it
is estimated that for a cost of $10,000 an electrical equipment can
be installed capable of working four such machines besides affording
power for lighting, pumping, ventilation of the mine, etc., thus saving
something like $100 a day for the operator, the great popularity of
these machines is readily understood.
After such a machine has been placed in position, a cut some four feet
wide, four or five inches high, and six feet deep can be made in five
minutes, with the expenditure of very little energy on the part of the
workmen. One of the largest cuttings ever recorded by one of these
machines is 1,700 square feet in nine and one-half hours, although this
may have been exceeded and not recorded.
Among the several advantages claimed for the chain machine over the
older pick machines is the small amount of slack coal produced, and
the absence of the racking vibrations that exhaust the workmen, and,
like the air drills, sometimes cause serious diseases. On the other
hand the advocates of the pick machines point out that they can be
used in mines too narrow for the introduction of chain machines. They
show also that there is a constant element of danger from motor-driven
machines in mines where the quantity of gas present makes it necessary
to use safety lamps, on account of the sparking of the machines which
may produce explosions. Both these claims are valid, but apply only
to special cases, or to certain mines, and do not affect the general
popularity of the chain machines.
There are several different types of chain cutting machines, such as
"long-wall machines," and "shearing machines," but these need not be
considered in detail here. The general principle upon which they work
is the same as the ordinary chain machine, the difference being in the
method of applying it for use in special situations.
ELECTRIC LIGHTING OF MINES
For many obvious reasons the ideal light for mining purposes is one
in which the danger from the open flame is avoided, particularly in
well-ventilated mines, or mines under careful supervision, where the
danger from inflammable gases is slight. The incandescent electric
light, therefore, has become practically indispensable in modern
mining operations. For certain purposes and in certain locations where
an intense light is desirable and where there is no danger from
combustible gases, arc lights are used to a limited extent. But there
is constant danger from the open flame in using such lights, and also
from the connecting wires leading to them. Furthermore, such intense
light is not usually necessary in the narrow passages of the mine.
To be sure, there is a certain element of danger even with incandescent
lights on account of the possibility of breakage of the globes, and of
short-circuiting where improper wiring has been done. To overcome as
much as possible the dangers from these sources, special precautions
are taken in wiring mines, and special bulbs are used. In general the
incandescent lamps as used in mining are made of stout round bulbs
of thick glass which are not likely to crack from the effects of
water dripping upon them while heated. As a further protection it is
customary to enclose the bulbs in wire cages. It is also customary to
use low-current lamps with a rather high voltage, although this must be
limited, as excessive voltage may in itself become a source of danger.
XIII
THE AGE OF STEEL
The iron industry has of late years become more and more merged into
the steel industry, as steel has been gradually replacing the parent
metal in nearly every field of its former usefulness. Steel is so much
superior to iron for almost every purpose and the process of making
it has been so simplified by Bessemer's discovery that it may justly
be said that civilization has emerged from the Iron Age, and entered
the Age of Steel. While iron is mined more extensively now than at
any time in the history of the world, the ultimate object of most of
this mining is to produce material for manufacturing steel. We still
speak of boiler iron, railroad iron, iron ships, etc., but these names
are reminiscent, for in the construction of modern boilers and modern
ships, steel is used exclusively. In the past decade it is probable
that no railroad rails even for the smallest and cheapest of tracks
have been made of anything but steel.
The last half of the nineteenth century has been one of triumph of
steel manufacture and production in America, and at the present time
the United States stands head and shoulders above any other nation in
this industry. In the middle of the century both Germany and England
were greater producers than America; but by the close of the century
the annual output in the United States was above fifteen million tons
as against England's ten and Germany's seven; and since 1900 this lead
has been greatly increased. The steel industry has become so great, in
fact, that it is "a sort of barometer of trade and national progress."
The great advances in the quantity of steel produced have been made
possible by corresponding advances in methods of winning the iron ore
from the earth. Mining machinery has been revolutionized at least twice
during the last half century, first by improved machines driven by
steam, and again by electricity and compressed air. Ore is still mined
to a limited extent by men with picks and shovels, but these implements
now play so insignificant a part in the process that they cannot be
considered as important factors. Steam shovels, automatic loaders and
unloaders, dynamite and blasting powder, have taken the place of brawn
and muscle, which is now mostly expended in directing and guiding
mining machinery rather than in actually handling the ore.
THE LAKE SUPERIOR MINES
At the present time the greatest iron-ore fields lie in the Lake
Superior region, and it is in this region that the greatest progress
in mining methods has been made in recent years. There are, of course,
extensive mines in other sections of the United States, but at least
three-quarters of all the iron produced in America comes from the
Lake Superior mines, and the systems of mining pursued there may be
considered as representative of the most advanced modern methods.
Where the iron ore of these mines is found near the surface of the
earth, the great system of "open-pit" mining is practised; but as only
a relatively small portion of the ore is so situated, modifications
of older mining methods are still employed. Of these the three most
important are known as "overhead scooping," "caving," and "milling."
In the overhead method a shaft is sunk into the earth to a depth of
several hundred feet, according to the depth of the ore, this shaft
being lined with timbers for support. From this shaft horizontal
tunnels are made in all directions in the ore deposits, and through
these tunnels the ore is conveyed to the shaft and thence to the
surface. As the ore is removed and the earth thus honeycombed in
all directions, supports of various kinds must be made to prevent
caving. For this purpose columns of the ore itself may be left, or
supports of masonry or wood or steel may be introduced. Under certain
circumstances, however, these supports are not employed, the earth
being allowed gradually to cave in at the surface as the ore is
removed, this being the method of mining known as "caving."
Where the ore deposit occurs in a favorable hillside the "milling"
system is frequently employed. In working this system a large
horizontal tunnel, twenty or more feet in diameter, is dug into the
hillside. Perpendicular shafts are then sunk from the top of the hill,
connected with openings leading directly into the top of the main
horizontal shaft. By this arrangement the ore, when loosened in these
perpendicular shafts, falls directly into the bins placed for its
reception about the openings, or into the rows of cars in waiting to
receive it. In this method dynamite and powder take the place of hand
labor, the main mass of ore being dislodged and thrown into the shaft
by blasting, instead of by hand labor.
But all these methods are overshadowed in magnitude by the great "open
pit" systems, where the ore is taken from the surface and handled
entirely by machinery, the only part played by the miner's pick being
that of assisting in loosing certain fragments so that they may be
more easily seized by the machines. Indeed, this system of mining
partakes of the nature of quarrying rather than that of mining in the
ordinary sense, the ore being scooped from the surface of the ground.
One naturally thinks of a mine as being subterranean; but in the great
open-pit mines in the Lake Superior region, which are the largest mines
in the world, all the mining is done at the surface of the earth.
It should not be understood, however, that in such mines nature has
left the red iron ore exposed at the surface in any great quantities.
On the contrary, it is usually covered by a layer of earth ranging from
a yard to ten or more yards in depth, and this, of course, must be
removed before open-pit methods can be practised. Prospecting for such
deposits is therefore just as necessary as in cases where the deposit
is situated much deeper in the earth; and the business of prospecting
by "test pit" men is as important an industry as ever.
When an available open-pit mine of sufficient extent has been located
the gigantic task of "stripping" or removing the overlying layer of
earth begins. Immense areas of land have been thus stripped in some of
these undertakings, no difficulties being considered insurmountable.
If a small river-bed lies in an unfavorable position, the course of
the river is changed regardless of expense. Farms and farm houses
are purchased and literally carted away, neither land nor houses
representing values worth considering when compared with the stratum
of ore beneath them. The single contract for stripping one area in the
Lake Superior region was let for a sum amounting to half a million
dollars.
As soon as a sufficiently large area has been stripped, railroads are
constructed into the pit, steam shovels are run into place, and the
actual work of mining begins. Five shovels full make a car-load, and
under ordinary circumstances the five loads may be delivered in as many
minutes.
The number of men required to manipulate one of these steam shovels is
from ten to twelve. The ore itself is frequently so hard that the scoop
of the shovel could not penetrate it until loosened and broken up, and
it is the business of the gang of workmen to do this and slide the ore
down within easy working distance of the shovel. This is mostly done
by blasting with dynamite and powder, little of the actual labor being
performed by hand. In blasting, a deep hole is first drilled into
the ore near the top of the embankment, and into this hole a stick of
dynamite is dropped and exploded. This enlarges the cavity sufficiently
so that a quantity of blasting powder may be poured in and set off,
tumbling the ore down within reach of the shovel.
This ore is frequently almost as hard as iron itself, many of the
pieces thus dislodged being too large for convenient handling, either
by the steam shovel or in the chutes at the wharves, and must be still
further broken up. This is sometimes done by the men with picks; but
in mining on a large scale, where the deposit is all of a very hard
nature, crushing machines are used.
In this manner the steam shovel is kept constantly supplied with ore
for the waiting train of cars. These trains are arranged on a track
running parallel with the track from which the steam shovel operates,
and at such a distance that the centre of the car will be directly
under the opening in the bottom of the shovel when it is swung around
on its crane. The engineer in charge of the locomotive drawing the
train stops it in a position so that the first shovelful of ore will
be dumped into the forward end of the first car. As each successive
shovelful is deposited, representing about one-fifth of a car-load,
the train is pulled or backed along the track about one-fifth of a
car-length. In this manner it is only necessary for the steam shovel to
be swung into the same position and dumped at the same point each time
to insure the proper loading of the cars.
From what has been said it will be seen that in this open-pit mining
the steam engine and steam locomotive still play a conspicuous part;
but in the other forms of iron mining, electric or compressed-air
motors are used, as much better adapted for underground work. In
the Lake Superior region, where everything is done by the most
modern methods, the use of horses and mules for hauling purposes is
practically unknown.
The cars used for hauling the ore are of peculiar construction. The
latest types are built of steel with a carrying capacity of fifty tons
of ore, and are so made that by simply knocking loose a few pins their
bottoms open and discharge the ore into the receiving bins on the
wharves, or into the chutes leading to the waiting boats.
A perennial problem in iron mining, whether surface or subterranean,
just as in all other kinds of mining, is the removal of accumulations
of water, some of these mines filling at the rate of from twenty-five
to thirty thousand gallons an hour. But an equally important problem
is that of removing moisture from the ore itself. Obviously every
additional pound of moisture adds to the cost and difficulty in
handling, and inasmuch as this ore must be transported a distance of
something like a thousand miles, necessitating three or four handlings
in the process, the aggregate amount of wasted energy caused by each
ton of water is enormous. It has been found that at least ten per
cent of the moisture may be dried out of the ore before shipping, and
that the ore does not tend to absorb moisture again under ordinary
circumstances once it has been dried. This is of course of great
advantage where it is found necessary to store it in heaps some little
time before shipping.
FROM MINE TO FURNACE
In most industries, particularly where the percentage of waste products
is large, it is found advantageous and economical to establish
factories as near the source of supply of raw material as possible. But
the iron ore mined in the Lake Superior region is transported something
like a thousand miles before being delivered to the factories. The
question naturally arises, Why is not the ore turned into pig iron or
steel ingots at once as near the mouths of the mines as possible, and
sent in this condensed form to the factories, thus saving more than
half the cost of transportation? The answer is simple: the coal mines
and steel factories lie in the East, one established by nature, the
other by man many years before iron ore was found in the Lake region.
And it is found just as cheap and easy to transport the iron to the
coal regions as it would be to transport the coal to the ore regions.
Furthermore, the factories in the neighborhood of Pittsburg and along
the southern shores of Lake Erie and Lake Ontario are near the great
centres of civilization, and are accessible the year round; while the
Lake Superior region is "frozen in" for at least three months in the
year.
And so, in place of a great traffic of coal westward to the Lake
Superior regions, there is a great eastward traffic of ore, by rail and
water, passing from the mines to furnaces and factories a thousand
miles away. Indeed, this is probably the greatest and most remarkable
system of transportation in the world. Specially constructed trains,
wharves, boats, and machinery, used for this single purpose, and not
duplicated either in design or extent, make this stupendous enterprise
a unique, as well as a purely American one.
The transportation begins with the train loads of ore that run from
the mines to the lake shore and out upon the wharves built to receive
them. These wharves are enormous structures, sometimes half a mile in
length, built up to about the height of the masts of ore boats. On the
sides and in the centres of these towering structures are huge bins for
holding the ore, these bins communicating directly with the holds of
the ore steamers tied up alongside. Four tracks are frequently laid on
the top of the wharves, and are so arranged that trains four abreast
can dump the ore into the bins, or waiting ships, at the same time.
If the bins are empty and boats waiting to receive a cargo, the ore
is discharged by long chutes into the holds from the cars. Otherwise
the bins are filled, the trains returning to the mines as quickly as
possible for fresh loads.
The boats for receiving this cargo are of special design, many of
them differing very greatly in appearance from ordinary ocean liners
of corresponding size. This is particularly true of the "whale-backs"
which have little in common in appearance with ordinary steamers except
in the matter of funnels; and even these are misplaced sternwards to
a distance quite out of drawing with the length of the hull. Their
shape is that of the ordinary type of submarine boat--that is,
cigar-shaped--this effect being obtained by a curved deck completely
covering the place ordinarily occupied by a flat deck. A wheel-house,
like a battle-ship's conning-tower, is placed well forward, supported
on steel beams some distance above the curved deck for observation
purposes; and engines, boilers, and coal bunkers occupy a small space
in the stern. The boat, therefore, is mostly hold.
But the "whale-backs" form only a small portion of the ore-fleet. The
ordinary type of boat conforms more nearly to the shape of ocean boats,
except that the bridge, wheel-house, and engines are located as in the
whale-backs. The bows of these boats are blunt, the desideratum in
such craft being hull-capacity rather than speed. For sea-worthiness
they are equal to any ocean boats, as the battering waves of Lake
Superior are quite as powerful and even more treacherous than those
of the Atlantic or Pacific. Some of these boats are five hundred feet
long, equal to all but the largest ocean vessels. Their coal-carrying
capacity is relatively small, since coaling stations are numerous at
various points on the journey, and every available inch of space is
utilized for the precious iron ore.
In order to facilitate loading, the decks are literally honey-combed
with hatches, some boats having fifteen or sixteen openings extending
the width of the deck. By this arrangement the time of loading is
reduced to a matter of a few hours, as a dozen chutes, each discharging
several tons of ore per minute, soon fill the yawning compartments
with the necessary six, eight, or nine thousand tons, that make up the
cargo.
Quite recently lake-navigators have learned, what rivermen have long
known, that cheap transportation may be effected on a large scale by
barges and towing. Before the outbreak of the Civil War forty years
ago, the Mississippi river swarmed with great cargo-carrying steamers,
employing armies of men and consuming enormous quantities of fuel.
But after the war the experiment was tried of hauling the cargoes on
barges towed by tug boats, and this proved to be so much cheaper that
the fleet of great river boats soon disappeared. In somewhat the same
way the barge has come into use of late years in the ore-traffic, and
the great ore-steamers now tow behind them one or two barges equal in
carrying capacity to themselves. In this way three ships' cargoes of
ore are transported a thousand miles by a score of men, a dozen on the
steamer and three or four on each of the barges. The barges themselves
are rigged as ships, and if necessary can shift for themselves by means
of sails attached to their stubby masts. But these are used only on
special and unusual occasions, as in case of accidental parting of the
hawsers during a storm.
The problem of loading the ships at the ore wharves is a simple one as
compared with the equally important one of transferring the ore from
the hold to trains of cars in waiting at the eastern end of the water
route. For four handlings of the ore are necessary before it is finally
deposited in the furnaces in the east. The first of these is from the
mine to cars; the second from the cars to the boats; the third from the
boats to cars; and the fourth from the cars to the blast furnaces.
For many years about the only hand work done in any of these processes
was that of transferring from the boats to the ore-trains, and even
here "automatic unloaders" are now rapidly supplanting the tedious hand
method. By the older methods a travelling crane, or swinging derrick,
dropped a bucket into the hold of the ore-vessel, where workmen
shovelled it full of the red ore. It was then lifted out by machinery
and the contents dumped into cars in much the same manner as that of
the steam shovel in the mines. Recently, however, a machine has been
perfected which scoops up the ore from the ship's hold and transfers
it to the cars without the aid of shovellers. The only human aid given
this gigantic machine is to guide it by means of controlling levers--to
furnish brains for it, in short--the "muscle" being furnished by steam
power. The great arm of this automatic unloader, resembling the sweep
of the old-fashioned well in principle, moves up and down, burying
the jaws of the shovel into the ore in the hold, and pulling them out
again filled with ore, with monotonous regularity, quickly emptying the
vessel under the guidance of half a dozen men, and performing the labor
of hundreds.
Thus the last field of activity for the laborer and his shovel, in the
iron-ore industry, has been usurped by mechanical devices. From the
time the ore is taken from the mine until it appears as molten metal
from the furnaces, it is not touched except by mechanisms driven by
steam, compressed air, or electricity. And yet, so rapid is the growth
of the iron and steel industry that there is almost always a demand for
more workmen.
For this reason, and perhaps because of the "American spirit" among
workmen, innovations in the way of labor-saving machinery are not
resisted among the mine laborers. The American workman seldom resists
or attacks machinery on the ground that it "throws him out of a job,"
as does his English cousin. It would be unjust to attribute this
attitude to superior acumen on the part of the American workman, and it
is probably a difference in conditions and surroundings that accounts
for the diametrically opposite views held by laborers on the two sides
of the Atlantic. But after all, results must speak for themselves, and
the advantage all lies in favor of the progressive attitude of the
western laborer, if we may judge by the relative social status and
financial standing of European and American workmen.
THE CONVERSION OF IRON ORE INTO IRON AND STEEL
Since steel is a compound substance composed essentially of two
elementary substances in varying proportions, it appears that the
name "steel," like wood, refers to a class of which there are several
varieties. This, of course, is the case, but for the moment we may
consider steel as a single substance composed chiefly of iron and
containing a certain percentage of carbon. In this respect it
resembles cast iron, steel having a smaller amount of carbon. Wrought
iron, on the other hand, contains no carbon at all, or at least only a
trace of it. But whatever the ultimate destiny of iron ore--whether it
is to become aristocratic manganese steel, or plebeian cast iron--it
must first pass through certain processes before being "converted."
To extract the pure iron from the iron ore it is necessary to heat
the ore in a furnace containing a certain quantity of coal, coke, or
charcoal, and limestone. The furnaces used in this process are known
as blast-furnaces, and in these about one ton of iron is extracted for
every two tons of Lake Superior ore, one and a quarter tons of coke,
and half a ton of limestone used. These quantities are by no means
constant, of course, but they may be taken as representing roughly the
relative amounts of material that must be fed into the furnaces.
Like everything else in the world of iron and steel, these
blast-furnaces have undergone revolutionary improvements during the
past quarter of a century. From being most dangerous and destructive
structures causing frightful loss of life and producing only about one
ton of iron a day for every man working about them, as formerly, they
have now become relatively harmless monsters, capable of turning out
six times that quantity of ore for each man employed.
The older blast-furnace was a huge, chimney-like structure, perhaps a
hundred feet high, into which the ore, coal, and limestone were poured.
Most of the work about these furnaces was done by manual labor, or
at least manual labor was an active assistant to the machinery used
in manipulating the furnaces. The top of the furnace was closed in by
a great movable lid, or "bell," and the material for charging it was
hauled up the sides by elevators and dumped in at the top. About the
top of the furnace was constructed a staging upon which the workmen
stood, an elevator shaft connecting the staging with the ground. The
ore and other materials were brought to the foot of the shaft on cars
from which it was shovelled into peculiarly designed wheelbarrows,
trundled to the elevator, and hauled to the top.
In order to dump the wheelbarrow loads into the furnaces it was
necessary to raise the bell. This was always dangerous, and frequently
resulted in the suffocation or injury of the workmen on the staging.
For when the bell was raised there was an escape of poisonous gases,
which might flare out in a sheet of flame, with the possibility of
burning or suffocating the workmen. The fumes from these gases, if
inhaled in small quantities, might simply cause coughing, hiccoughing,
or dizziness; but when inhaled in large quantities they struck down
a man like the fumes of chloroform, suffocating him in a few seconds
if he was not removed at once into a purer atmosphere. Indeed, the
likelihood of this was so great that at many of these furnaces a
special workman was detailed to take the position on the staging, well
out of range of the gas, his sole duty being to rescue any of the men
who might be overcome, and hurry them as quickly as possible down the
elevator shaft into the pure atmosphere below. It was not an uncommon
thing in the neighborhood of these older furnaces to see stretched
about on the ground at the base several workmen in various stages of
suffocation. Fortunately, by use of precautionary measures, fatal
accidents were rather unusual, the men being overcome only temporarily,
and usually recovering quickly and returning to work.
But the poisonous gas coming from the top of the furnace was not the
only, nor the worst, danger constantly menacing the men on the staging.
Their greatest dread was the possibility of explosions occurring in the
furnace, which might hurl the bell into the air and deluge the upper
structure with molten metal. Against this possibility there was no
safeguard in the older furnaces, explosions occurring without warning
and frequently with terrible effects. But fortunately these older types
of furnaces are being rapidly replaced by the newer forms in which the
danger to life, at least from gas and explosions, is minimized. And
even in the older furnaces, improvements in the structure of the bell
and in methods of filling have greatly lessened the dangers.
In the modern type of blast-furnace the work at the top formerly
performed by men on the staging is accomplished entirely by machinery.
The general appearance of these furnaces is that of huge iron pipes or
kettles mounted on several iron legs. The outer structure, or shaft,
is constructed of plate iron, but this is lined with fire brick of
considerable thickness, and may have a water jacket interposed between
these bricks and the shaft. About this large kettle are smaller
kettles of somewhat similar shape having pipes leading from their tops
to the larger structure. These smaller kettles are the "stoves" used in
producing the hot air for the furnace.
The working capacity of some of these furnaces is in the neighborhood
of a thousand tons of iron a day, although the average furnace produces
only about half that quantity. The powerful machinery used for charging
these monster caldrons hauls the ore and other charging materials to
the top and dumps it in car-load lots.
In the older methods of manufacturing steel, the contents of the
blast-furnaces were first drawn off into molds and allowed to cool
into what is known as pig-iron. It was then necessary to re-heat
this iron and treat it by the various methods for producing the kind
of steel desired. By the newer methods, however, time and money are
saved by converting the liquid iron from the blast-furnace directly
into steel without going through the transitional stage of cooling it
into pigs. Pigs of iron are still made in enormous quantities, to be
sure, but mostly for shipment to distant places or for stores as stock
material. For statistical purposes, however, the entire product of the
blast-furnace, whether liquid or solid, is known as "pig iron."
The older method of removing the iron from the blast furnaces was by
tapping at the opening near the bottom, the stream of liquid iron being
allowed to flow into a connected series of sand molds, each mold being
about three feet long by three or four inches wide. The bottom of
these molds was flat but as the metal cooled in them the upper surface
became round in shape, assuming a fanciful resemblance to a pig's back.
In this molding a great amount of time was wasted in the slow process
of cooling, and a large expenditure of energy wasted in this handling
and re-handling of the metal.
In modern smelting works, however, pigs are no longer cast in sand
molds, the molten metal from the furnace being discharged directly into
iron molds attached to an endless chain. These molds are long, narrow,
and shallow, having the general shape of sand molds. Each mold as it
passes beneath the opening in the furnace remains just long enough to
receive the requisite amount of metal to fill it, and then moves on to
a point where it is either sprayed with water, or cooled by actually
passing through a tank of water, emerging from this bath with the metal
sufficiently solidified so that it may be dropped into a waiting car at
the turning point of the endless chain. In this manner the charge from
the blast-furnace may be drawn, cooled, and converted into pigs, loaded
into cars, and hauled away without extra handlings or loss of time, the
whole process occupying practically no more time than the initial step
of tapping by the older method.
Where the contents of the blast-furnace are to be converted into
steel at once, the molten metal is run off into movable tanks which
carry it directly to the steel furnaces. These tanks, holding perhaps
twenty tons of metal, are made of thick iron lined with fire brick,
and arranged on low, flat cars designed specially for the purpose.
These tanks are run under the spout of the furnace, filled with molten
metal, and drawn to the steel works, possibly five miles away. As a
rule, the distance is much less, but as far as the condition of the
metal is concerned distance seems to make little difference, as even
at the extreme distance there is no apparent cooling of the seething
mass. The intense heat given off by these trains necessitates specially
constructed cars, tracks, bridges, and crossings.
The destination of this train load of iron pots is the "mixer"--a great
200-ton kettle in which the products from the various furnaces are
mixed and rendered uniform in quality. On the arrival of the train at
the mixer, Titanic machinery seizes the twenty-ton pots and dumps their
contents bodily into the glowing pool in the great crucible. Like the
filling process, this operation occupies only a few minutes.
From the mixer the metal is poured out into ladles and transferred
immediately to the "converter"--the important development of Sir Henry
Bessemer's discovery that has made possible the modern steel industry.
This converter resembles in shape some of the old mortars used in the
American Civil War--barrel-shaped structures suspended vertically by
trunnions at the middle and having an opening at the top. Into this
opening at the top the metal from the mixer is poured and when the
converter has been sufficiently charged a blast of cooled air is blown
in at the bottom through the molten metal. This blast emerges at the
top as a long roaring flame, of a red color at first but gradually
changing into white, and then faint blue. These changes in color are
indicative of the changes that are taking place in the metal, and the
appearance of a certain shade of color indicates that the conversion
into steel is complete, and that it is time for shutting off the blast
of air. Any mistake in this matter--even the variation of thirty
seconds' time--means a loss of thousands of dollars in the quality of
steel produced. The man whose duty it is to determine this important
point, therefore, holds an exceptionally delicate and responsible
position, and receives pay accordingly.
In deciding the exact moment when the blast shall be turned off, this
workman is guided entirely by the sense of sight. Mounted on a platform
commanding the best possible view of the mouth of the converter and
wearing green glass goggles of special construction, this man watches
the change of color in the flame until a certain shade is reached--a
shade that to the ordinary untrained observer does not differ in
appearance from that of a moment before--when he gives the signal to
shut off the blast. When this signal is given the contents of the
converter is no longer common-place cast iron, but steel, ready to be
molded into rails, boilers, or a thousand and one other useful things.
The contents of the converter may now be drawn off as liquid steel into
molds of any desired shape and size, and when cooled will be ready for
shipment. But in the great steel factories the metal is not ordinarily
allowed to cool completely before being sent to the rolling mills,
being drawn off into molds placed along the surface of small, flat
cars. These molds are rectangular, ordinarily four or five feet high by
less than two feet in diameter. The metal is poured into openings in
the top of each mold, and allowed to cool, solidify, and to contract
enough to permit the outer casings of the molds to be pulled off by
machinery, leaving the glowing "ingots" of steel ready for molding by
machinery in the mills.
The process just described is the one by which "Bessemer steel" is
made. There is another important process in use, the "open hearth"
method, which differs considerably from this; but before considering
this process something more should be said of the man whose discoveries
made possible the modern steel industry.
SIR HENRY BESSEMER
In the history of the progress of science and invention some one great
name is usually pre-eminently associated with epoch-marking advances,
although there may be a cluster of important but minor associates. This
is true in the history of the modern steel industry, and the central
name here is that of Sir Henry Bessemer.
Bessemer was born at Charlton, England, on Jan. 19, 1813. Always
of an inventive turn of mind, his attention was first directed to
improving the methods then in use for the manufacture of steel, while
experimenting with the manufacture of guns. After several years of
experimenting in his little iron works near London, he reached some
definite results which he announced to the British Association in 1856.
In this paper he described a process of converting cast iron into
steel by removing the excess of carbon in the molten metal by a blast
of air driven through it. This paper, in short, described the general
principles still employed in the Bessemer process of manufacturing
steel. And although the first simple process described by Bessemer has
been modified and supplemented in recent years, it was in this paper
that the process which placed steel upon the market as a comparatively
cheap, and infinitely superior, substitute for ordinary iron, was first
disclosed.
This famous paper before the British Association aroused great interest
among the English ironmasters, and applications for licenses to use
the new process were made at once by several firms. But the success
attained by these firms was anything but satisfactory, although
Bessemer himself was soon able to manufacture an entirely satisfactory
product. The disappointed ironmasters, therefore, returned to the
earlier processes, the inventor himself being about the only practical
ironmaster who persisted in using it.
Recognizing the defects in his process, Bessemer set about overcoming
them, and at the end of two years he had so succeeded in perfecting
his methods that his product, equal in every respect to that of the
older process, could be manufactured at a great saving of time and
money. But the ironmasters were now skeptical, and refused to be again
inveigled into applying for licenses. Bessemer, therefore, with the
aid of friends, erected extensive steel works of his own at Sheffield,
and began manufacturing steel in open competition with the other steel
operators. The price at which he was able to sell his product and
realize a profit was so much below the actual cost of manufacture by
the older process, that there was soon consternation in the ranks of
his rivals. For when it became known that the firm of Henry Bessemer &
Co. was selling steel at a price something like one hundred dollars a
ton less than the ordinary market price, there was but one thing left
for the ironmasters to do--surrender, and apply for licenses to be
allowed to use the new process.
By this means, and through the profits of his own establishment,
Bessemer eventually amassed a well-earned fortune. Moreover, he was
honored in due course by a fellowship in the Royal Society, and
knighted by his government.
One other name is usually associated with that of Bessemer in the
practical development of the inventor's original idea. That is the
name of Robert Mushet, and the "Bessemer-Mushet" process is still in
use. Mushet's improvement over Bessemer's original process was that
of adding a certain quantity of _spiegeleisen_, or iron containing
manganese, which, for some reason not well understood, simplifies the
process of steel making. Mushet, therefore, must be considered as the
discoverer of a useful, though not an absolutely essential, accessory
to the Bessemer process.
OPEN-HEARTH METHOD
In the open-hearth method the metal from the blast-furnaces is not
sent to the converter, but is poured into oven-like structures built
of fire brick, and in these heated to a terrific temperature. This
heat has the same effect upon the metal as the blast of air in the
Bessemer converter, and this open-hearth process has become very
popular for manufacturing certain kinds of steel. While in the method
of application this process differs greatly from that of Bessemer, it
differs largely in the fact that the oxygen necessary to burn off the
carbonic oxide, silicon, etc., is made to play over the molten mass
instead of passing through it.
It has been noted that the old type of blast-furnace gave off great
quantities of combustible gases which became waste products. Even gases
containing something like 20 or 25 per cent. of carbonic acid may be
highly inflammable, and thus an enormous quantity of valuable fuel
was constantly wasted. In some furnaces, to be sure, they were put to
practical use for heating the blast, but as the quantities given off
were greatly in excess of the amount necessary for this purpose, there
was a constant loss even with such furnaces.
Quite recently it has been found that the gases can be used directly
in gas engines, developing three or four times as much energy in this
way as if they were used as fuel under ordinary steam boilers. These
engines are now used for operating the rolling-mill machinery, and the
machinery of shops adjoining the furnaces, which, however, must not be
situated at any very great distances from the furnaces. This accounts
partly for the grouping together of blast-furnaces, rolling mills,
and machine shops, the economical feature of this arrangement being
so great that segregated establishments find it next to impossible to
compete in the open market with such "communities" under the conditions
prevailing in the steel industry.
ALLOY STEELS
The introduction of Krupp steel, or nickel, for armor plates, a few
years ago, called attention in a popular way to the fact that for
certain purposes pure steel--that is, iron plus a certain quantity of
carbon--was not as useful as an alloy of steel with some other metal.
An alloy was a great improvement over ordinary steel or iron plates
used in warfare; but in the more peaceful pursuits, as well as in
warfare, certain alloyed steels, such as chrome steel, tungsten steel,
and manganese steel play a very important part.
Chrome steel, for example, in the form of projectiles, is the most
dreaded enemy of nickel-steel armor plates, because of the hardness
and elasticity of armor-piercing projectiles made of it. Such a
steel contains about two per cent. of chromium with about one or
two per cent. of carbon, which when suddenly cooled is extremely
hard and tough. This kind of steel and manganese steel are the best
guards against the burglar and safe-blower, as they resist even very
highly tempered and hardened drills. As this steel is relatively
cheap to manufacture, it is frequently used in the construction of
safes and burglar-proof gratings. For this purpose, however, it is
sometimes combined in alternate layers with soft wrought iron, the
steel resisting the point of the drill, while the iron furnishes the
necessary elasticity to resist the blows of the sledge. The bars used
in modern jails and prisons are often made in a similar manner of
alternate sheaths of iron and chrome steel. Against the time-honored
"hack-saw," the bugbear of prison officials for generations, such
bars an inch and a quarter in diameter offer an almost insurmountable
obstacle; and they are equally effective against a heavy sledge hammer.
At least one case is recorded in which the use of these "composite"
bars resulted in a disastrous fire in a prison. A small blaze having
started in the basement of this prison, attempts to reach it with a
stream of water were defeated by the bars of the steel gratings at the
windows, which would not admit the nozzle of the hose. A corps of men
armed with hack-saws, crow-bars, and sledges attacked this grating,
which, if made of ordinary steel, could have been readily broken. But
against these composite bars they produced no appreciable effect.
Meanwhile the fire gained rapidly, threatening the building and its
eight hundred inmates, and was only checked after holes had been made
through fire-proof floors and ceilings for admitting the nozzle.
Manganese steel is peculiar in becoming ductile by sudden cooling, and
brittle on cooling slowly--precisely the reverse of ordinary steel. It
contains about 1.50 per cent. of carbon, and about 12 per cent. of
manganese. If a small quantity of manganese, that is, 1 or 2 per cent.,
is used the steel is very brittle, and becomes more so as greater
quantities of the manganese are used, up to about 5 per cent. From that
point, however, it becomes more ductile as the quantity of manganese
is increased, until at about 12 per cent. it reaches an ideal state.
When used for safes and money vaults this steel has one great advantage
over chrome steel--it is not affected by heat. By using a blow-pipe
and heating a limited area of steel, the burglar is able to "draw the
temper" of ordinary steel to a sufficient depth so that he can drill
a hole to admit a charge of dynamite; but manganese steel retains
its temper under the blow-pipe no matter how long it may be applied.
Against attacks of the sledge, however, it is probably inferior to
chrome steel.
Like manganese steel, tungsten steel retains its temper even when
heated to high temperatures. For this reason it is used frequently in
making tools for metal-lathe work where thick slices of iron are to be
cut, as even at red heat such a tool continues to cut off metal chips
as readily as when kept at a lower temperature. This steel contains
from 6 to 10 per cent. of tungsten, a metallic element with which we
have previously made acquaintance in our studies of the incandescent
lamp.
XIV
SOME RECENT TRIUMPHS OF APPLIED SCIENCE
Not long ago a little company of men met in a lecture hall of Columbia
University to discuss certain questions in applied science. It was
a small gathering, and its proceedings were so unspectacular as to
be esteemed worth only a few lines of newspaper space. The very
name--"Society of Electro-Chemistry"--seemed to mark it as having to do
with things that are caviar to the general. The name seems to smack of
fumes of the laboratory, far removed from the interests of the man in
the street. Yet Professor Chandler said in his address of welcome to
the members of the society, that though theirs was the very youngest
of scientific organizations, he could confidently predict for it a
future position outranking that of all its sister societies; and his
prediction was based on the belief that electro-chemistry is destined
to revolutionize vast and important departments of modern industry. A
majority of the heat-using methods of mechanics will owe their future
development to the new science.
In a word, then, despite its repellent name, the society in question
has to do with affairs that are of the utmost importance to the man in
the street. Though its members may sometimes deal in occult formulas
and abstruse calculations, yet the final goal of their studies has to
do not with abstractions but with practicalities,--with the saving
of fuel, the smelting of metals, the manufacture of commodities. But
theory in the main must precede practice--the child creeps before it
walks. "The later developments of industrial chemistry," says Sir
William Ramsey, "owe their success entirely to the growth of chemical
theory; and it is obvious," he adds significantly, "that that nation
which possesses the most competent chemists, theoretical and practical,
is destined to succeed in the competition with other nations for
commercial supremacy and all its concomitant advantages."
Fortunately this interdependence of science and industry is not a
mere matter of prophecy--for the future tense is never quite so
satisfying as the present. Vastly important changes have already
been accomplished; old industries have been revolutionized, and new
industries created. The commercial world of to-day owes vast debts to
the new science. Professor Chandler outlined the character of one or
two of these in the address just referred to. He cited in some detail,
for example, the difference between old methods and new in such an
industry as the manufacture of caustic soda. He painted a vivid word
picture of the distressing conditions under which soda was produced
in the old-time factories. Salt and sulphuric acid were combined to
produce sulphate of soda, which was mixed with lime and coal and heated
in a reverberatory furnace. Each phase of the process was laborious.
The workmen operating the furnaces sweltered all day long in an
almost unbearable atmosphere--stripped to the waist, dripping with
perspiration, sometimes overcome with heat. Their task was one of the
most trying to which a man could be subjected.
But to-day, in such establishments as the soda manufactories at Niagara
Falls, all this is changed. A salt solution circulates continuously in
retorts where it can be acted upon by electricity supplied from dynamos
operated by the waters of the Niagara River. The workmen, comfortably
dressed and moving about in a normal temperature, have really nothing
to do but refill the retorts now and then and remove the finished
product. "It almost seems," Professor Chandler added with a smile, "as
if workmen ought to be glad to pay for the privilege of participating
in so pleasant an occupation. At all events it is, in all seriousness,
a pleasure for the visitor who knows nothing of old practices to
witness this triumph of a modern scientific method."
Even more interesting, said Professor Chandler, are the processes
employed in the modern method of producing the metal aluminum by the
electrolytic process. The process is based on the discovery made
by Mr. Charles M. Hall while he was a student working in a college
laboratory, that the mineral cryolite will absorb alumina to the extent
of twenty-five per cent. of its bulk, as a sponge absorbs water. The
solution of this compound is then acted on by electricity, and the
aluminum is deposited as pure metal. A curiously interesting practical
detail of the process is based on the fact that pulverized coke remains
perfectly dry and rises to the surface when stirred into a crucible
containing the hot alumina solution: moreover, it rises to the surface
and remains there as a shield to protect the workmen against the heat
of the solution. It serves yet another purpose, as the powdered alumina
may be sifted upon it and left there to dry before being stirred into
the crucible. A most ingenious yet simple device tells the workman when
any particular crucible is in need of replenishing. A small, ordinary,
incandescent electric-light bulb is placed in circuit between the poles
that convey the electric current through the alumina solution. So long
as the crucible contains alumina, the bulb does not glow, because
twenty volts of electricity are required to make it incandescent,
whereas seven volts pass through the solution. But so soon as the
alumina becomes exhausted, resistance to the current rises in the
cryolite solution and, as it were, dams back the electric current
until it overflows into the wire at sufficient pressure to start the
signal lamp. Then it is necessary merely for a workman to stir into
the solution the dry alumina resting on the surface, along with the
coke that supports it. This, of course, reestablishes the electrolytic
process; the lamp goes out and the coke, unaffected by its bath, rises
to the surface to support a fresh supply of alumina.
Such a process as this, contrasted with the usual methods of smelting
metals in fiercely heated furnaces, seems altogether wonderful. Here
a pure metal is extracted from the clayey earth of which it formed
a part, without being melted or subjected to any of the familiar
processes of the picturesque, but costly, laborious, and even
dangerous, blast-furnaces. There is no glare and roar of fires; there
are no showers of sparks; there is no gush of fiery streams of molten
metal. A silent and invisible electric current, generated by the fall
of distant waters, does the work more expeditiously, more efficiently,
and more cheaply than it could be done by any other method as yet
discovered.
Fully to appreciate the importance of the method just outlined, we
must reflect that aluminum is a metal combining in some measure the
properties of silver, copper, and iron. It rivals copper as a conductor
of electricity; like silver it is white in color and little subject
to tarnishing; like iron it has great hardness and tensile strength.
True, it does not fully compete with the more familiar metals in their
respective fields; but it combines many valuable qualities in fair
degree; and it has an added property of extreme lightness that is all
its own. Add to this the fact that aluminum is extremely abundant
everywhere in nature--it is a constituent of nearly all soils and is
computed to form about the twelfth part of the entire crust of the
earth--whereas the other valuable metals are relatively rare, and it
will appear that aluminum must be destined to play an important part in
the mechanics of the future. There is every indication that the iron
beds will begin to give out at no immeasurably distant day; but the
supply of aluminum is absolutely inexhaustible. Until now there has
been no means known of extracting it cheaply from the clay of which
it forms so important a constituent. But at last electro-chemistry
has solved the problem; and aluminum is sure to take an important
place among the industrial metals, even should it fall short of
the preeminent position as "the metal of the future" that was once
prematurely predicted for it.
NITROGEN FROM THE AIR
There is a curious suggestiveness about this finding of aluminum at our
very door, so to speak, some scores of centuries after the relatively
rare and inaccessible metals had been known and utilized by man. But
there is another yet more striking instance of an abundant element
which man needed, but knew not how to obtain until the science of our
own day solved the problem of making it available. This is the case of
the nitrogen of the air. As every one knows, this gas forms more than
three-fourths of the bulk of the atmosphere. But, unlike the other
chief constituent, oxygen, it is not directly available for the use of
plants and animals. Yet nitrogen is an absolutely essential constituent
of the tissues of every living organism, vegetable and animal. Any
living thing from which it is withheld must die of starvation, though
every other constituent of food be supplied without stint; and the fact
that the starving organism is bathed perpetually in an inexhaustible
sea of atmosphere chiefly composed of nitrogen would not abate by one
jot the certainty of its doom.
To be made available as food for plants (and thus indirectly as food
for animals) nitrogen must be combined with some other element, to
form a soluble salt. But unfortunately the atoms of nitrogen are
very little prone to enter into such combinations; under all ordinary
conditions they prefer a celibate existence. In every thunder-storm,
however, a certain quantity of nitrogen is, through the agency
of lightning, made to combine with the hydrogen of dissociated
water-vapor, to form ammonia; and this ammonia, washed to the earth
dissolved in rain drops, will in due course combine with constituents
of the soil and become available as plant food. Once made captive
in this manner, the nitrogen atom may pass through many changes and
vicissitudes before it is again freed and returned to the atmosphere.
It may, for example, pass from the tissues of a plant to the tissues
of a herbivorous animal and thence to help make up the substance of a
carnivorous animal. As animal excreta or as residue of decaying flesh
it may return to the soil, to form the chief constituent of a guano
bed, or of a nitrate bed,--in which latter case it has combined with
lime or sodium to form a rocky stratum of the earth's crust that may
not be disturbed for untold ages.
A moment's reflection on the conditions that govern vegetable and
animal life in a state of nature will make it clear that a soil once
supplied with soluble nitrates is likely to be replenished almost
perpetually through the decay of vegetation. But it is equally clear
that when the same soil is tilled by man, the balance of nature is
likely to be at once disturbed. Every pound of grain or of meat
shipped to a distant market removes a portion of nitrogen; and unless
the deficit is artificially supplied, the soil becomes presently
impoverished.
But an artificial supply of nitrogen is not easily secured--though
something like twenty-five million tons of pure nitrogen are weighing
down impartially upon every square mile of the earth's surface. In the
midst of this tantalizing sea of plenty, the farmer has been obliged
to take his choice between seeing his land become yearly more and more
sterile and sending to far-off nitrate beds for material to take the
place of that removed by his successive crops. The most important of
the nitrate beds are situated in Chili, and have been in operation
since the year 1830. The draft upon these beds has increased enormously
in recent years, with the increasing needs of the world's population.
In the year 1870, for example, only 150,000 tons of nitrate were
shipped from the Chili beds; but in 1890 the annual output had grown
to 800,000 tons; and it now exceeds a million and a half. Conservative
estimates predict that at the present rate of increased output the
entire supply will be exhausted in less than twenty years. And for some
years back scientists and economists have been asking themselves, What
then?
But now electro-chemistry has found an answer--even while the alarmists
were predicting dire disaster. Means have been found to extract the
nitrogen from the atmosphere, in a form available as plant food, and at
a cost that enables the new synthetic product to compete in the market
with the Chili nitrate. So all danger of a nitrogen famine is now at
an end,--and applied science has placed to its credit another triumph,
second to none, perhaps, among all its conquests. The author of this
truly remarkable feat is a Swedish scientist, Christian Birkeland
by name, Professor of Physics in the University of Christiania. His
experiments were begun only about the year 1903, and the practical
machinery for commercializing the results--in which enterprise
Professor Birkeland has had the co-operation of a practical engineer,
Mr. S. Eyde--is still in a sense in the experimental stage,--albeit
a large factory was put in successful operation in 1905 at Notodden,
Norway.
Professor Birkeland has thus accomplished what many investigators in
various parts of the world have been striving after for years. The
significance of his accomplishment consists in the fact that he has
demonstrated the possibility of making nitrogen combine with oxygen in
large quantities and at a relatively low expense. The mere fact of the
combination, as a laboratory possibility, had been demonstrated in an
elder generation by Cavendish, and more recently by such workers as
Sir William Crookes, and Lord Rayleigh in England and Professors W.
Mutjmaan and H. Hofer in Germany. Moreover, the experiments of Messrs.
Bradley and Lovejoy, conducted on a commercial scale at Niagara Falls,
had seemed to give promise of a complete solution of the problem;
had, indeed, produced a nitrogen compound from the air in commercial
quantity, but not, unfortunately, at a cost that made competition
with the Chili nitrate possible. Equally unsuccessful in solving this
important part of the problem had been the experiments, conducted on a
large scale, of Professors Kowalski and Moscicki, at Freiburg.
All these experimenters had adopted the same agent as the means of, so
to say, forcing the transformation--namely, electricity. The American
investigators employed a current of ten thousand volts; the German
workers carried the current to fifty thousand volts. The flame of the
electric arc thus produced ignited the nitrogen with which it came in
contact readily enough; but the difficulty was that it came in contact
with so little. Despite ingenious arrangements of multiple poles, the
burning-surface of the multiple arc remained so small in proportion to
the expenditure of energy that the cost of the operation far exceeded
the commercial value of the product. Such, at least, must be the
inference from the fact that the establishments in question did not
attain commercial success.
The peculiarity of Professor Birkeland's method is based upon the
curious fact that when the electric arc is made to pass through a
magnetic field, its line of flame spreads out into a large disk--"like
a flaming sun." The sheet of flame thus produced represents no greater
expenditure of energy than the lightning flash of light that the same
current would produce outside the magnetic field; but it obviously
adds enormously to the arc-light surface that comes in contact with
the air, and hence in like proportion to the amount of nitrogen that
will be ignited. In point of fact, this burning of nitrogen takes
place so rapidly in laboratory experiments as to vitiate the air of
the room very quickly. In the commercial operation, with powerful
electro-magnets and a current of five thousand volts, operating, of
course, in closed chambers, the ratio between energy expended and
result achieved is highly satisfactory from a business standpoint,
and will doubtless become still more so as the apparatus is further
perfected.
To the casual reader, unaccustomed to chemical methods, there may seem
a puzzle in the explanation just outlined. He may be disposed to say,
"You speak of the nitrogen as being ignited and burned; but if it is
burned and thus consumed, how can it be of service?" Such a thought
is natural enough to one who thinks of burning as applied to ordinary
fuel, which seems to disappear when it is burned. But, of course, even
the tyro in chemistry knows that the fuel has not really disappeared
except in a very crude visual sense; it has merely changed its form.
In the main its solid substance has become gaseous, but every atom of
it is still just as real, if not quite so tangible, as before; and the
chemist could, under proper conditions, collect and weigh and measure
the transformed gases, and even retransform them into solids.
In the case of the atmospheric nitrogen, as in the case of ordinary
fuel, a burning "consists essentially in the union of nitrogen atoms
with atoms of oxygen." The province of the electric current is to
produce the high temperature at which alone such union will take place.
The portion of nitrogen that has been thus "burned" is still gaseous,
but is no longer in the state of pure nitrogen; its atoms are united
with oxygen atoms to form nitrous oxide gas. This gas, mixed with the
atmosphere in which it has been generated, may now be passed through a
reservoir of water, and the new gas combines with a portion of water
to form nitric acid, each molecule of which is a compound of one atom
of hydrogen, one atom of nitrogen, and three atoms of oxygen; and
nitric acid, as everyone knows, is a very active substance, as marked
in its eagerness to unite with other substances as pure nitrogen is in
its aloofness.
In the commercial nitrogen-plant at Notodden, the transformed nitrogen
compound is brought into contact with a solution of milk of lime,
with the resulting formation of nitrate of lime (calcium nitrate),
a substance identical in composition--except that it is of greater
purity--with the product of the nitrate beds of Chili. Stored in closed
cans as a milky fluid, the transformed atmosphere is now ready for the
market. A certain amount of it will be used in other manufactories for
the production of various nitrogenous chemicals; but the bulk of it
will be shipped to agricultural districts to be spread over the soil as
fertilizer, and in due course to be absorbed into the tissues of plants
to form the food of animals and man.
ANOTHER METHOD OF NITROGEN FIXATION
Just at the time when the Scandinavian experimenters were solving
the problem of securing nitrogen from the air, other experimenters
in Italy, operating along totally different lines, reached the same
important result. The process employed by these investigators is known
as the Frank and Caro process, and it bids fair to rival the Norwegian
method as a commercial enterprise. The process is described as
follows by an engineering correspondent of the London _Times_ in the
Engineering Supplement of that periodical for January 22, 1908:
"This process is based upon the absorption of nitrogen by calcium
carbide, when this gas, in the pure form, is passed over the carbide
heated to a temperature of 1,100 degrees centigrade in retorts of
special form and design. The calcium carbide required as raw material
for the cyanamide manufacture is produced in the usual manner by
heating lime and coke to a temperature of 2,500 degrees centigrade in
electric furnaces of the resistance type.
"The European patent rights of the Frank and Caro process have
been purchased by the Societa Generale per la Cianamide of Rome,
and the various subsidiary companies promoting the manufacture in
Italy, France, Switzerland, Norway, and elsewhere, are working under
arrangement with the parent company as regards sharing of profits.
"The first large installation of a plant for carrying out this process
was erected at Piano d'Orta, in Central Italy, and was put into
operation in December, 1905. The power for this factory is developed
by an independent company, and is obtained by taking water from the
river Pescara and leading it to a point above the generating station
at Tramonti. A head of 90 feet, equivalent to 8,400 horse-power, is
here made available for the industries of the district. The power of
the cyanamide factory is transmitted a distance of 6-1/4 miles at 6,000
volts. An aluminum and chemical works are also dependent upon the same
power station.
"The Piano d'Orta works contains six furnaces for the manufacture of
cyanamide, each furnace containing five retorts for absorption of the
nitrogen by the carbide. A retort is capable of working off three
charges of 100 kilograms (220 pounds) of carbide per day of 24 hours,
the weight of the charge increasing to 125 kilograms by the nitrogen
absorbed. The present carbide consumption of the Piano d'Orta factory
is, therefore, at the rate of about 3,000 tons per annum, and the
output of calcium cyanamide is about 3,750 tons per annum. The company
controlling the manufacture at Piano d'Orta is named the _Societa
Italiana per la Fabbricazione di Prodotti Azotati_. Extensions of
the factory at this place to a capacity of 10,000 tons per annum are
already in progress. Another company is also planning the erection
of similar works at Fiume and at Sebenico, on the eastern borders
of the Adriatic Sea. The additional electric power required will be
obtained by carrying out the second portion of the power development
scheme on the river Pescara. A fall of 235 feet, equivalent to 22,000
horse-power, is available at the new power station, which is being
erected at Piano d'Orta."
After stating that companies to operate the Frank and Caro process have
been organized in France, in Switzerland, in Germany, in England, and
in America,--the last-named plant being at Muscle Shoals, Tennessee
River, in Northern Alabama--the writer continues:
"These facts prove that the manufacture of the new nitrogenous manure
will soon be carried on in all the more important countries on
both sides of the Atlantic. If the financial results come up to the
promoter's expectations the industry in five years' time will have
become one of considerable magnitude.
"A modification of the original process of some importance has been
suggested by Polzeniusz. This chemist has found that the addition of
fluorspar (CaF2) to the carbide reduces the temperature required
for the absorption process by 400 degrees centigrade, while it also
produces a less deliquescent finished material.
"As regards cost of manufacture, no very reliable figures are yet
available, but the companies promoting the new manufacture are
regulating their sale prices by those of the two rival artificial
manures--ammonium sulphate and nitrate of soda. Calcium cyanamide is
now being sold in Germany at 1s. to 1s. 6d. (25 to 37 cents) per unit
of combined nitrogen cheaper than ammonium sulphate, and 3s. to 3s. 6d.
(75 to 87 cents) per unit cheaper than nitrate of soda. Whether the
manufacture will prove remunerative at this price of about £10 10s.
($102.50) per ton remains to be seen. It is evident that, as the raw
material of the cyanamide manufacture (calcium carbide) costs at least
£8 ($40) per ton to produce under the most favorable conditions, the
margin of profit will not be large, and that very efficient management
will be required to earn fair dividends on the capital sunk in the new
industry.
"It must be noted, however, that the processes are new and are
doubtless capable of improvement as experience is gained in working
them; while, on the other hand, the competition of the two rival
artificial manures is likely to diminish as the years pass on.
"The new industry is, therefore, likely to be a permanent addition to
the list of electro-metallurgical processes. But for the present its
success can only be expected in centres of very cheap water-power, as,
for instance, in those localities where the electric horse-power year
can be generated and transmitted to the cyanamide works at an inclusive
cost of £2 ($10) or under."
ELECTRICAL ENERGY AND HIGH TEMPERATURES
It will be observed that the active instrumentality by which the
industrial feats thus far outlined have been accomplished, is that
weird conveyer of energy known as electricity. In the case of the
aluminum manufacture, electricity operated according to the strange
process of electrolysis, in virtue of which certain atoms of matter
move to one pole of a battery while other atoms move to the opposite
pole, thus effecting a separation--the result being, in the case in
question, the deposit of pure aluminum at the negative pole. In the
case of the nitrogen factories, however, the manner of operation of
the electric current is quite different. Electricity, as such, is not
really concerned in the matter; the efficiency of the current depends
solely upon the production of heat. For example, any other agency
that brought the atmosphere to a corresponding temperature would be
equally efficacious in igniting the nitrogen. But in actual practice,
for this particular purpose, no other known means of producing high
temperatures could at all compete with the electric arc.
There are numerous other operations involving the employment of high
temperatures in which electricity is equally preeminent. It is feasible
with the electric arc to attain a temperature of about 3,600 degrees
centigrade--and even this might be exceeded were it not that carbon,
of which the electrodes are composed, volatilizes at that temperature.
Meantime, the highest attainable temperature with ordinary fuels in
the blast furnace is only about 1,800 degrees; and the oxy-hydrogen
flame is only about two hundred degrees higher. A mixture of oxygen and
acetylene, however, burns at a temperature almost equaling that of the
electric arc; and this flame, manipulated with the aid of a blowpipe,
offers a useful means of applying a high temperature locally, for such
processes as the welding of metals. The very highest temperatures yet
reached in laboratory or workshop, however, are due to the use of
explosive mixtures. Thus a mixture of the metal aluminum granulated,
and oxide of iron, when ignited by a fulminating powder, readjusts its
atoms to form oxide of aluminum and pure iron, and does this with such
fervor that a temperature of about three thousand degrees is reached,
the resulting iron being not merely melted but brought almost to the
boiling point. Practical advantage is taken of this reaction for the
repair of broken implements of iron or steel, the making of continuous
rails for trolleys, and the like.
This reaction of aluminum and iron does not, to be sure, give a higher
temperature than the electric arc; but this culminating feat has been
achieved, in laboratory experiments, through the explosion of cordite
in closed steel chambers; the experimenters being the Englishmen Sir
Andrew Noble and Sir F. Abel. It is difficult to estimate accurately
the degree of heat and pressure attained in these experiments; but it
is believed that the temperature approximated 5,000 degrees centigrade,
while the pressure represented the almost inconceivable push of ninety
tons to the square inch.
It may be of interest to explain that cordite is a form of smokeless
powder composed of gun cotton, nitroglycerine, and mineral jelly. No
doubt the extreme heat produced by its explosion is associated with
the suddenness of the reaction; corresponding to the efficiency as a
propellant that has led to the adoption of this powder for use in the
small arms of the British Army. No commercial use has yet been made
of cordite as a mere producer of heat; but there is an interesting
suggestion of possible future uses in the fact that crystals of diamond
have been found in the residue of the explosion chamber--microscopic
in size, to be sure, but veritable diamonds in miniature. Sir
William Crookes has suggested that, could the reaction be prolonged
sufficiently, "there is little doubt that the artificial formation of
diamonds would soon pass from the microscopic stage to a scale more
likely to satisfy the requirements of science, if not those of personal
adornment."
OTHER INDUSTRIAL PROBLEMS OF TO-DAY AND TO-MORROW
In attempting to suggest the importance of science in its relation
to modern industries, I have thought it better to cite three or
four illustrative cases in some detail rather than to attempt a
comprehensive summary of the almost numberless lines of commercial
activity that have a similar origin and dependence.
To attempt a full list of these would be virtually to give a catalogue
of mechanical industries. It may be well, however, to point out a few
familiar instances, in order to emphasize the economic importance of
the subject; and to suggest a few of the lines along which present-day
investigators are seeking further conquests.
Very briefly, then, consider how the application of scientific
knowledge has changed the aspect of the productive industries. Thanks
to science, farming is no longer a haphazard trade. The up-to-date
farmer knows the chemical constitution of the soil; understands what
constituents are needed by particular crops and what fertilizing
methods to employ to keep his land from deteriorating. He knows how
to select good seed according to the teaching of heredity; how to
combat fungoid and insect pests by chemical means; how to meet the
encroachments of the army of weeds. In the orchard, he can tell by the
appearance of leaf and bark whether the soil needs more of nitrogen,
of potash, or of humus; he uses sprays as a surgeon uses antiseptics;
he introduces friendly insects to prey on insect pests; he irrigates
or surface-tills or grows cover crops in accordance with a good
understanding of the laws of capillarity as applied to water in the
earth's crust. In barnyard and dairy he applies a knowledge of the
chemistry of foods in his treatment of flock and herd; he ventilates
his stables that the stock may have an adequate supply of oxygen; he
milks his cows with a mechanical apparatus, extracts the cream with a
centrifugal "separator," and churns by steam or by electric power.
In the affairs of manufacturer and transporter of commodities, methods
are no less revolutionary. Steam power and electric dynamo everywhere
hold sway; trolley and electric light and telephone have found their
way to the most distant hamlet; electricians and experimental chemists
are searching for new methods in the factories; artificial stone is
competing with the product of the quarries; artificial dyes have
sounded the doom of the madder and indigo industries.
And yet it requires no great gift of prophecy to see that what has been
accomplished is only an earnest of what is to come in the not distant
future. In every direction eager experimenters are on the track of new
discoveries. Any day a chance observation may open new and important
fields of exploration, just as Hall's observation about the power
of cryolite to absorb aluminum pointed the way to the new aluminum
industry; and as Birkeland's chance observation of the electric arc in
a magnetic field unlocked the secret of the unresponsive nitrogen. It
will probably not be long, for example, before a way will be found to
produce electric light without heat--in imitation of the wonderful lamp
of the glow-worm.
Then in due course we must learn to use fuel without the appalling
waste that at present seems unavoidable. A modern steam-engine makes
available only five to ten per cent. of the energy that the burning
fuel gives out as heat--the rest is dissipated without serving man the
slightest useful purpose. Moreover, the new studies in radio-activity
have taught us that every molecule of matter locks up among its
whirling atoms and corpuscles a store of energy compared with which
the energy of heat is but a bagatelle. It is estimated that a little
pea-sized fragment of radium has energy enough in store--could we
but learn to use it--to drive the largest steamship across the
ocean--taking the place of hundreds of tons of coal as now employed.
The mechanics of the future must learn how to unlock this treasury of
the molecule; how to get at these atomic and corpuscular forces, the
very existence of which was unknown to science until yesterday. The
generation that has learned that secret will look back upon the fuel
problems of our day somewhat as we regard the flint and steel and the
open fire of the barbarian.
If problems of energy offer such alluring possibilities as this,
problems of matter are even more inspiring. The new synthetic chemistry
sets no bounds to its ambitions. It has succeeded in manufacturing
madder, indigo, and a multitude of minor compounds. It hopes some day
to manufacture rubber, starch, sugar--even albumen itself, the very
basis of life. Rubber is a relatively simple compound of hydrogen and
carbon; starch and sugar are composed of hydrogen, carbon, and oxygen;
albumen has the same constituents, plus nitrogen. The raw materials
for building up these substances lie everywhere about us in abundance.
A lump of coal, a glass of water, and a whiff of atmosphere contain
all the nutritive elements, could we properly mix them, of a loaf of
bread or a beefsteak. And science will never rest content until it has
learned how to make the combination. It is a long road to travel, even
from the relatively advanced standpoint of to-day; but sooner or later
science will surely travel it.
And then--who can imagine, who dare predict, the social and economic
revolution that must follow? Our social and business life to-day
differs more widely from that of our grandfathers than theirs differed
from the life of the Egyptian and Babylonian of three thousand years
ago; but this gap is as ditch to cañon compared with the gap that
separates us from the life of that generation of our descendants which
shall have learned the secret of making food-stuffs from inorganic
matter in the laboratory and factory. It is a long road to travel, I
repeat; but modern science travels swiftly and with many short-cuts,
and it may reach this goal more quickly than any conservative dreamer
of to-day would dare to predict.
All speed to the ambitious voyager!
APPENDIX
REFERENCE LIST AND NOTES
CHAPTER I
MAN AND NATURE
For a general discussion of primitive conditions of labor and
prehistoric man's civilization, it will be of interest in connection
with this chapter to consult volume I., chapter I., which deals with
prehistoric science. The appendix notes on that chapter (vol. I.,
pp. 302, 303) refer to some books which may be consulted for fuller
information along the same lines.