this metal was scarce, for iron is everywhere. "Wherever, as we go up
and down, we see a red-colored surface, or a reddish tint upon the solid
substances of the earth, we see iron--the bank of red clay, the red
brick, the red paint upon the house wall, the complexion of rosy youth,
or my lady's ribbon. Even the rosy apple derives its tint from iron
which it contains."[8] But although iron is so abundant it is seldom
found in its pure or natural state. It is nearly always mixed with other
substances, the mixture being known as iron ore. Primitive man could
find copper and tin in their pure state but the only pure iron he could
find was the little which fell from heaven in the form of meteors, and
even this was not perfectly pure for meteoric iron is also mixed
slightly with other metals.
The iron which lay about primitive man in such abundance was buried and
locked tightly in an _ore_. To separate the iron from the other
substances of the ore was by no means an easy thing to do. Iron can best
be extracted from the ore by putting the ore in a fire and melting out
the iron. Place some iron ore in a fire and if the fire is hot
enough--and it must be very hot indeed--the iron will leave the ore and
will gather into a lump at the bottom of the fire. To separate the iron
from its ore in this way is to make iron. When and where man first
learned the secret of making iron is of course unknown. A camp-fire in
some part of the world may have shown to man the first lump of iron, or
a forest fire sweeping along and melting ores in its path may have given
the first hint for the manufacture of iron.
[Illustration: FIG. 3.--THE PRIMITIVE FORGE.]
Iron making at first doubtless consisted in simply melting the ore in an
open heap of burning wood or charcoal, for charcoal is an excellent fuel
for smelting (melting) ores. But this open-fire method was wasteful and
tedious and at a very early date the smelting of the ore was done in a
rude sort of a furnace. A hole ten or twelve feet deep was dug in the
side of a hill. In the hole were placed charcoal and iron ore, first a
layer of charcoal, then a layer of the ore. At the top of the mass there
was an opening and at the bottom there were several openings. When the
mass was set on fire the openings produced a good strong draft, the
charcoal was consumed, and the ore was smelted. The product was a lump
of _wrought iron_, known as the _bloom_.
[Illustration: FIG. 4.--BELLOWS WORKED BY THE FEET.]
The hillside furnace worked well enough when the wind was favorable, but
when the wind was unfavorable there was no draft and no iron could be
made. So ironmakers found a way by which the air could be driven into
the furnace by artificial means. They invented the _bellows_, a blowing
apparatus (Fig. 3) which was usually made of goat skins sewed together
and which was operated either by the hands or by the feet (Fig. 4).
Sometimes the bellows consisted of a hollow log in which a piston was
worked up and down (Fig. 5). After the invention of the bellows,
ironmakers could make their iron whenever and wherever they pleased, for
they could force air into their furnaces at any time and at any place.
This rude bellows forcing a draft of air into a half-closed furnace
filled with a burning mass of charcoal and iron ore was the first form
of the forge, one of the greatest of all inventions.
[Illustration: FIG. 5.--THE WOODEN BELLOWS.]
With the invention of the forge the stone age gradually passed away and
the iron age was ushered in. Tools and weapons could now be made of
iron. And great was the difference between iron tools and stone tools.
To cut down a tree with a flint hatchet required the labor of a man for
a month, while to clear a forest with such an implement was an
impossible task. But the forge gave to man iron for the sharp cutting
tools, for the ax and knife and chisel and saw. With these he became the
master of wood and he could now easily cut down trees and build houses
and make furniture and wagons and boats.
As time went on and man advanced in civilization, iron was found to be
the most useful of metals. Iron can be shaped into many forms. It can be
drawn into wire of any desired length or fineness, it may be bent in any
direction, it may be sharpened, or hardened, or softened, at pleasure.
"Iron accommodates itself to all our wants and desires and even to our
caprices. It is equally serviceable to the arts, the sciences, to
agriculture and war; the same ore furnishes the sword, the plowshare,
the scythe, the pruning-hook, the needle, the spring of a watch or of a
carriage, the chisel, the chain, the anchor, the compass and the bomb.
It is a medicine of much virtue and the only metal friendly to the human
frame."[9]
A metal that was so useful was needed in large quantities, yet the
primitive forge could turn out only small quantities of iron. A day's
labor at the bellows would produce a lump weighing only fifteen or
twenty pounds. As a result of this slowness in manufacture there was
always in primitive and ancient times a scarcity of iron. Indeed in some
countries iron was a precious metal, almost as precious as silver or
gold. In many countries, it is true, there were thousands of forges at
work, but in no country was the supply of iron equal to the demand. The
old forge could not supply the demand, yet centuries passed before any
great improvement was made in the progress of iron making.
[Illustration: FIG. 6.--A BLAST FURNACE OF THE MIDDLE AGES.]
Near the close of the Middle Ages improvements upon the primitive forge
began to be made. In the sixteenth century ironmakers in Germany began
to smelt ore in closed furnaces and to build their furnaces higher and
to make them larger (Fig. 6). Sometimes they built their furnaces to a
height of twenty or thirty feet. About this time also a better and a
stronger blast was invented. Water-power instead of hand-power began to
be used for operating the bellows. In some cases wooden bellows--great
wooden pistons working in tubs--were substituted for the old bellows of
leather. By the end of the sixteenth century so many improvements had
been made upon the primitive forge that it no longer resembled the forge
of ancient times. So the new forge received a new name and was called a
_blast furnace_.[10] You should observe, however, that the blast furnace
was simply the old forge built with a large closed furnace and provided
with a more powerful blast.
The invention of the blast furnace marked the beginning of a new era in
the history of iron making. In the first place there was produced in the
blast furnace a kind of iron that was entirely different from that which
was produced in the primitive forge. In the primitive forge there was
made a lump of practically pure unmelted iron, known as wrought iron. In
the blast furnace there was produced a somewhat impure grade of melted
iron, known as _cast_ iron, or _pig_[11] iron. In the second place, the
blast furnace produced iron in quantities vastly greater than it was
ever produced by the old forge. In the blast furnace more iron could be
made in a day than could be made by the forge in a month. In some of the
early blast furnaces a thousand pounds of iron could be made at one
melting and we read of one early furnace that produced 150 tons of iron
in a year.
[Illustration: FIG. 7.--MAKING CHARCOAL.]
But even with the blast furnace it was still difficult to make enough
iron to supply the ever-increasing demands of the industrial world. In
the sixteenth and seventeenth centuries machinery was brought into use
more than ever before and of course more iron was needed for the
construction of the machines. There was ore enough for all the iron that
was needed but it was difficult to get fuel enough to smelt the ore.
Charcoal was still used as the fuel for smelting (Fig. 7), and in order
to get wood for the charcoal great inroads were made upon the forests.
In England in the early part of the eighteenth century Parliament had to
put a check upon the manufacture of iron in certain counties in order to
save the forests of those counties from utter destruction. It then
became plain that if iron making were to be continued on a large scale a
new kind of fuel would have to be used in the furnaces. So men set their
wits to work to find a new kind of fuel. As far back as 1619 Dud Dudley
in the county of Warwick, England, undertook to use ordinary soft coal
in his furnaces but his experiment was not very successful or very
profitable. More than a century after this an English ironmaker named
Abraham Darby began (in 1735) to use _charred coal_ in his blast
furnaces, and his experiments were successful. Here was the new fuel
which was so badly needed. Charred coal is simply _coke_ and coke could
be had in abundance. So the new fuel was soon used in all parts of
England and by the end of the eighteenth century coke was driving
charcoal out of blast furnaces (Fig. 8).
About the time the use of coke for smelting became general, an
Englishman named Neilson brought about another great change in the
process of iron making. Before Neilson's time the blast driven into the
furnace had always been one of cold air. Neilson learned that if the air
before entering the furnace were heated to a temperature of 600 degrees
it would melt twice the amount of ore and thus produce twice the amount
of iron without any increase in the amount of fuel. So he invented (in
1828) a _hot blast_ for the blast furnace (Fig. 9). With the use of coke
and with the hot blast the production of iron increased enormously. But
there was need for all the iron that could be made. Indeed it seems that
the world can never get too much iron. About the time the hot blast was
invented iron chains instead of ropes began to be used for holding
anchors, iron plows began to be made in great numbers (p. 83), iron
pipes instead of hollow wooden logs began to be used as water-mains in
cities, and iron rails began to be used on railroads. To supply iron for
all these purposes kept ironmakers busy enough, even though they burned
coke in their furnaces and made use of the hot air blast.
[Illustration: FIG. 8.--A PITTSBURGH COKE OVEN.]
[Illustration: FIG. 9.--A MODERN BLAST FURNACE.]
But ironmakers were soon to become busier than ever before. About the
middle of the nineteenth century Sir Henry Bessemer invented a new
process of making steel. Steel is only iron mixed with a small amount of
carbon. Ironmakers have known how to make steel--and good steel,
too--for thousands of years, but before the days of Bessemer the process
had always been slow and tedious, and the cost of steel had always been
very great. Bessemer undertook to make steel in large quantities and
at low prices. In his experiments amid showers of molten metal he often
risked his life, but his perseverance and courage were rewarded. By 1858
he had invented a process by which tons of molten iron could be run into
a furnace and in a few minutes be converted into a fine quality of
steel. This invention of Bessemer was the last great step in the history
of the forge.
[Illustration:
From copyright stereograph by Underwood & Underwood, N. Y.
FIG. 10.--GREAT STEEL RAIL PASSING THROUGH ROLLER STEEL MILL.]
Now that steel could be made in great quantities and at a low cost it
was put to uses never dreamed of in former times. Soon the railroad rail
was made of steel (Fig. 10), bridges were made of steel, ships of war
were plated with steel. Then ocean grayhounds and battleships were made
of steel, still later steel freight cars and steel passenger coaches
were introduced, while in our own time we see vast quantities of steel
used in the building of houses. So while the invention of Bessemer
marked the last step in the history of the forge it also marked the
ending of the Age of Iron and the beginning of the wonderful age in
which we live--the Age of Steel.
FOOTNOTES:
[8] J. R. Smith, "The Story of Iron and Steel," p. 3.
[9] From "Five Black Arts," p. 311.
[10] The old forge continued to be used by the side of the blast furnace
for centuries, and of course where it was used it was still called a
forge. Thus we are told that in Maryland in 1761, there were eight
furnaces and ten forges. It is said that as late as twenty-five years
ago in certain parts of the Appalachian regions the American mountaineer
still worked the little primitive forge to make his iron.
[11] It was given the name of _pig_ iron because when the molten metal
ran into the impressions made for it upon the sanded floor and cooled,
it assumed a shape resembling a family of little pigs.
THE STEAM-ENGINE
We have now traced the steps by which man mastered the art of kindling a
fire quickly and easily and have followed the progress that has been
made in the most common uses of fire. But the story of a most important
use of fire remains to be told, the story of its use in doing man's
_work_. How important this use is, how much of the world's work is done
through the agency of fire, a little reflection will make plain. Fire
makes steam and what does steam do? Its services are so many you could
hardly name all of them. The great and many services of steam are made
possible by the fire-engine, or _steam-engine_, and the story of this
wonderful invention will now be told.
That steam has the power to move things must have been learned almost as
soon as fire was used to boil water. Heat water until it boils and the
steam that is formed is bound to move something unless it is allowed to
escape freely. It will burst the vessel if an outlet is not provided.
That is why a spout has been placed on the tea-kettle. Where there is
cooking, steam is abundant and the first experiments in steam were
doubtless made in the kitchen (Fig. 1). It has been said that the idea
of the steam-engine first occurred to Adam as he watched his wife's
kettle boil.
[Illustration: FIG. 1.--FIRST EXPERIMENTS WITH STEAM.]
Whatever may have happened in ancient kitchens, we are certain that
there were no steam-engines until many centuries after Adam. The
beginnings of this invention are not shrouded in so much mystery as are
those of the match and the lamp and the forge. In giving an account of
the steam-engine we can mention names and give dates from the very
beginning of the story. We know what the first steam-engine was like
and we know who made it and when and where it was made. It was made
120 B. C. by Hero, a philosopher of Alexandria in Egypt. It was like
the one shown in Figure 2. The boy applies the fire to the steam-tight
vessel _p_ and when steam is formed it passes up through the tube
_o_ and enters the globe which turns easily on the pivots. The steam,
when it has filled the globe, rushes out of the short tubes _w_ and _z_
projecting from opposite sides of the globe and bent at the end in
opposite directions. As it rushes out of the tubes the steam strikes
against the air and the reaction causes the globe to revolve, just as in
yards we sometimes see jets of water causing bent tubes to revolve. This
was Hero's engine, the first steam-engine ever made.
[Illustration: FIG. 2.--HERO'S ENGINE, 120 B. C.]
Hero's engine was used only as a toy and it seems to represent all the
ancients knew about the power of steam and all they did with it. It is
not strange that they did not know more for there is no general rule by
which discoveries are made. Sometimes even enlightened peoples have for
centuries remained blind to the simplest principles of nature. The
Greeks and Romans with all their culture and wisdom were ignorant of
some of the plainest facts of science. It is a little strange, however,
that after Hero's discovery was made known, men did not profit by it. It
would seem that eager and persistent attempts would have been made at
once to have steam do useful work, as well as furnish amusement. But
such was not the case. Hero's countrymen paid but little attention to
his invention and the steam-engine passed almost completely out of men's
minds and did not again attract attention for nearly seventeen hundred
years.
About the end of the fifteenth century Europe began to awaken from a
long slumber and by the end of the sixteenth century its eyes were wide
open. Everywhere men were now trying to learn all they could. The study
of steam was taken up in earnest about the middle of the sixteenth
century and by the middle of the next century quite a little had been
learned of its nature and power. In 1629 an Italian, Branca by name,
described in a book a steam-engine which would furnish power for
pounding drugs in a mortar. There was no more need for such a machine
then than there is now and of course the inventor aroused no interest
in his engine. You can easily understand how Branca's engine (Fig. 3)
works. The steam causes the wheels and the cylinder to revolve. As the
cylinder revolves, a cleat on it catches a cleat on the pestle and lifts
the pestle a short distance and then lets it fall. Here the pestle
instead of being raised by a human hand is raised by the force of steam.
This engine would be more interesting if an engine had actually been
made, but there is no reason to believe that Branca ever made the engine
he described. We owe much to him, nevertheless, for suggesting how steam
might be put to doing useful work.
[Illustration: FIG. 3.--BRANCA'S ENGINE, 1629.]
It was not very long before an Englishman put into practice what the
Italian had only suggested. Edward Somerset, the Second Marquis of
Worcester, in 1663 built a steam-engine that raised to the height of
forty feet four large buckets of water in four minutes of time. This was
the first useful work ever done by steam. Figure 4 shows the
construction of Worcester's engine.
[Illustration: FIG. 4.--WORCESTER'S ENGINE, 1663.]
In this engine there was one improvement over former engines which was
of the greatest importance: there was one vessel in which the steam was
generated and another in which the steam did its work. The steam-engine
now consisted of two great divisions, the boiler and the engine proper.
Worcester spent a large part of his fortune in trying to improve the
steam-engine, yet he received neither profit nor honor as a reward. He
died poor and his name was soon forgotten. His service to the world was
nevertheless very great. In his time the mines of England had been sunk
very deep into the earth; and the deeper they were sunk the greater was
the difficulty of lifting the water out of them and keeping them dry.
The water was lifted up from the mines by means of buckets drawn by
horses or oxen (Fig. 5). Sometimes it took several hundred horses to
keep the water out of a single mine. It was Worcester's object to
construct an engine that would do the work of the horses. The engine he
built could not do this, yet it furnished the idea--and the idea is
often the most important thing. It was not long before engines built
upon Worcester's plan were doing useful work at the mines. At the
opening of the eighteenth century the steam-engine had been put to work
and was serving man in England and throughout the continent of Europe.
[Illustration: FIG. 5.--AN ANCIENT METHOD OF DRAWING WATER.]
[Illustration: FIG. 6.--PAPIN'S ENGINE, 1690.]
The first engines were not safe. Often the steam pressed too heavily
upon the sides of the vessel in which it was compressed and there were
explosions. About 1680 Denis Papin, a Frenchman, invented the _safety
valve_, that is a valve that opens of its own accord and lets out steam
when there is more in the vessel than ought to be there. About ten years
later Papin gave the world another most valuable idea. In Worcester's
engine the steam in the steam chest pressed directly on the water that
was to be forced up. Papin showed a better way. He invented the engine
shown in Figure 6. In this engine a small quantity of water was placed
in the bottom of the cylinder _A_. Fitting closely in the cylinder was a
_piston_ _B_ such as Papin had seen used in ordinary pumps. We will
suppose that the piston is near the bottom of the cylinder and that a
fire is built underneath. The bottom being made of very thin metal the
water is rapidly converted into steam and thus drives the piston up to
the top as shown in the figure. Here a latch _E_ catches the piston-rod
_H_ and holds the piston up until it is time for it to descend. Now the
fire is removed and the steam, becoming cold, is condensed and a vacuum
is formed below the piston. The latch _E_ now releases the rod _H_ and
the piston is driven down by the air above it, pulling with it the rope
_L_ which passes over the pulleys _TT_. As the rope descends it lifts a
weight _W_ or does other useful work. As the inventor of the piston
Papin ranks among the greatest of those whose names are connected with
the development of the steam-engine.
Our story has now brought us to the early part of the eighteenth
century. Everywhere men were now trying to make the most of the ideas of
Worcester and Papin. The mines were growing very deep. As the water in
them was getting beyond control something extraordinary had to be done.
Now it seems that whenever the world is in need of an extraordinary
service someone is found to render that service. The man who built the
engine that was needed was a humble blacksmith of Dartmouth, England,
Thomas Newcomen. This master mechanic in 1705 constructed the best
steam-engine the world had yet seen. We must study Newcomen's engine
(Fig. 7) very carefully. The large beam _ii_ moved freely up and down on
the pivot _v_. One end of the beam was connected with the heavy pump-rod
_k_ by means of a rope or chain working in a groove and the other end
was connected with the rod _r_ in the same way. When steam from the
boiler _b_ passed through the valve _d_ into the cylinder (steam-chest)
_a_ it raised the piston _s_ and with it the piston-rod _r_ thus
slackening the rope and allowing the opposite end of the beam to be
pulled down by the weight of the pump-rod _k_. As soon as the piston _s_
reached the top of the cylinder the steam was shut off by means of the
valve _d_ and the valve _f_ was turned and a jet of cold water from the
tank _g_ was injected into the cylinder _a_ with the steam. The jet of
cold water condensed the steam rapidly--steam is always condensed
rapidly when anything cold comes in contact with it--and the water
formed by the condensation escaped through the pipe _p_ into the tank
_o_. As soon as the steam in _a_ is condensed, a vacuum was formed in
the cylinder and the atmosphere above forced the piston down and at the
same time pulled the pump-rod _k_ up and lifted water from the well or
mine. When the piston reached the bottom of the cylinder the valve _d_
was opened and the piston again ascended. Thus the beam is made to go up
and down and the pumping goes on. Notice that steam pushes the piston
one way and the atmosphere pushes it back.
[Illustration: FIG. 7.--NEWCOMEN'S ENGINE, 1705.]
In Newcomen's engine the valves (_f_ and _d_) at first were opened and
shut (at each stroke of the piston) by an attendant, usually a boy. In
1713 a boy named Humphrey Potter, in order to get some time for play, by
means of strings and latches, caused the beam in its motion to open and
shut the valves without human aid. We must not despise Humphrey because
his purpose was to gain time for play. The purpose of almost all
inventions is to save human labor so that men may have more time for
amusement and rest. Humphrey Potter ought to be remembered not as a lazy
boy but as a great inventor. His strings and latches improved the engine
wonderfully (Fig. 8). Before his invention the piston made only six or
eight strokes a minute; after the valves were made to open and shut by
the motion of the beam, it made fifteen or sixteen strokes a minute and
the engine did more than twice as much work.
[Illustration: FIG. 8.--HUMPHREY POTTER'S LATCHES AND STRINGS.]
Newcomen's engine as improved by Potter and others grew rapidly into
favor. It was used most commonly to pump water out of the mines but it
was put to other uses. In and about London it was used to supply water
to large houses and in 1752 a flour mill near Bristol was driven by a
steam-engine. In Holland Newcomen's engines were used to assist the
wind-mills in draining lakes.
[Illustration: FIG. 9.--JAMES WATT STRIVING TO IMPROVE NEWCOMEN'S
ENGINE.]