consisted of an indefinite number of inventions, all aiming at economy,
brilliancy, steadiness, convenience, beauty, and so on. But in no
respect has this improvement been more rapid and radical than in the
adaptation of lamps to the various combustible fluids that have bid
for favor. While the various oils, animal and vegetable, were almost
solely in vogue as illuminants at the beginning of the century, they
were largely superseded at a later period by the burning-fluid known
as camphene. This was a purified oil of turpentine, which found
great favor on account of its economy, convenience, cleanliness, and
brilliancy of light. But it was very volatile, and its vapors formed
with air a dangerously explosive mixture. Yet with all this it might
have held its own for a long time, had not Gesner, in 1846, discovered
that a superior mineral oil, which he called “kerosene,” could be
readily and profitably distilled from the coal found on Prince Edward
Island. This kerosene or hydrocarbon oil speedily displaced camphene
as an illuminant. Its manufacture rapidly developed into an important
industry in the United States, and large distilling establishments
arose, both on the Atlantic coast, where foreign coal was used, and
throughout the country, wherever cannel or other convertible coal
was found. With the discovery of petroleum in paying quantities on
Oil Creek, Pa., in 1859, there came about a great change in kerosene
lamp-lighting. It was found, upon analysis, that crude petroleum
contained about fifty-five per cent of kerosene, which constituted its
most important product. The manufactories of kerosene from cannel or
other coal, therefore, went out of existence, and new ones, larger in
size and greater in number, sprung up for the manufacture of kerosene
or, popularly speaking, coal oil, from petroleum. This illuminant
came into almost universal favor for lamp use, owing to its cheapness
and brilliancy. It is not free from danger when improperly distilled,
but under the operation of stringent laws governing its preparation
and testing, danger from its use has been reduced to a minimum. In
rural districts, in smaller towns and villages, wherever economy
and convenience are essentials, and when beauty in lamp effects is
desirable, the kerosene illuminant has become indispensable.
The discovery of petroleum helped further to light the world and
distinguish the century. It gave us gasolene, naphtha, gas oil,
astral oil, and the very effective “mineral sperm,” which is almost
universally used in lighthouses and as headlights for locomotives. With
the addition of kerosene, a favorite light of the beginning of the
century—the tallow dip of our grandmothers—began to fall into disuse.
The homelike pictures of housewives at their annual candle-dippings,
or in the manipulation of their moulds, became venerable antiques.
Candle-light paled in the presence of the higher illuminants. Though
still a convenient light under certain circumstances, it plays a
gradually diminishing part amid its superiors.
One of the signal triumphs of the century has been the introduction of
gas-lighting. Though illuminating gas made from coal was known as early
as 1691, it did not come into use, except for experiments or in a very
special way, until the beginning of the nineteenth century. In 1809, a
few street lamps were lit with gas in London. An unsuccessful attempt
was made to introduce gas into Baltimore in 1821. Between 1822 and
1827, the gas-light began to have a feeble foothold in Boston and New
York. Other cities began to introduce it as an illuminant in streets
and, eventually, in houses. But the process was very slow, owing to
intense opposition on the part of both savants and common people, who
saw in it a sure means of destruction by poison, explosion, or fire. It
was not much before the middle of the century that prejudice against
illuminating gas was sufficiently allayed to admit of its general
use. But meanwhile many valuable experiments as to its production and
adaptation were going on. The most productive source of illuminating
gas was found to be bituminous coal. Though gas could be produced by
distillation from other substances, such as shale, lignite, petroleum,
water, turf, resins, oils, and fats, none could compete in quality,
quantity, and economy with what is known as ordinary coal gas, at
least, not until the time came, quite late in the century, when it was
found that non-luminous gases, such as water gas, could be rendered
luminous by impregnating them with hydrocarbon vapor. This became known
commercially as water gas, and it is now largely used in place of coal
gas, because it is cheaper and, for the most part, equally effective as
a luminant.
Gas-lighting has, of course, its limitations. It is not adapted for use
beyond the range of cities or towns whose populations are sufficient
to warrant the large expenditures necessary for gas plants. It is a
special rather than general light. Yet within its limited domain of use
it has proved of wonderful utility,—a source of cheer for millions, a
clean, safe, and economic light, a convenience far beyond the candle,
the lamp, or any previous lighting appliance. In the street, it is a
source of safety against thieves and way-layers. In the slums, it is
both policeman and missionary, baffling the wrong-doer, exposing the
secrecy that conduces to crime, laying bare the hotbeds of shame. It
is as well a source of heat as light, and consequently convertible into
power for light mechanical purposes. In the kitchen, it is more and
more becoming a boon to the housewife, who by means of the gas range
escapes, in cooking, much of the dust, smoke, worry, and even expense
of the coal cook stove and range. In the parlor, library, or sick-room,
it is a cheerful and effective substitute for the coal grate, and
may be made to assume the cosy qualities and fantastic shapes of the
old-fashioned wood fire. Coincident with the discovery of petroleum,
its inseparable companion, natural gas, came into prominence as a
source of both light and heat, or this became true, at least, after it
was ascertained that natural gas regions existed which could be tapped
by wells, and made to give forth their gaseous product independent of
the oil that may have at one time existed near or in connection with
it. This natural source of light and heat became as interesting to the
geologist, explorer, and capitalist as the source of petroleum itself,
and soon every likely section was prospected, with the hope of finding
and tapping those mysterious caverns of earth in which the pent-up
luminant abounded in paying quantities. It was found that workable
natural gas regions were numerous in the United States, especially in
proximity to petroleum or bituminous coal deposits, and little time
was lost in their development. As if by magic, a new and profitable
industry sprang into existence. The natural gas well became almost
as common as the oil well, and at times far more awe-inspiring as
it shot into space its volcanic blasts which, when ignited through
carelessness, as sometimes happened, carried to the vicinage all the
dangers and terrors of Vesuvius or Stromboli. Powerful as was the
force with which natural gas sought its freedom, wonderful as was
the phenomenon of its escape from the subterranean alembic in which
it was distilled, human genius quickly harnessed it by appliances
for conservation and carriage to places where it could be utilized.
Sometimes great industries sprang up contiguous to the wells; at
others, it was carried through pipes to cities many miles distant,
where it became a light for street, home, and store, and a prodigious
energy in factory, furnace, forge, and rolling-mill. In fact, no marvel
of the century has been at once so weird and inscrutable in its origin
as natural gas, or more potential as an agency within the areas to
which its use is limited. The question is ever uppermost in connection
with natural gas, will it last? The gas springs of the Caucasus
Mountains have been burning for centuries. But that is where nature’s
internal forces have their correlations and compensations. Where it is
quite otherwise, that is, where the vents of natural gas reservoirs
are abnormally numerous, or where those reservoirs are drained to the
extreme for commercial purposes, not to say through sheer wastefulness,
the geologist is ready to surmise that the natural gas supply cannot be
a perpetual one.
But one of the most magnificent triumphs of the century in the matter
of light came about through the agency of electricity. We have already
seen the beginnings of electric lighting in the discovery of Sir
Humphrey Davy, in 1809, that when the ends of two conducting wires,
mounted with charcoal pieces, were brought close together, a brilliant
light, in the shape of an arc or curve, leaped from one piece of
charcoal to the other. Davy’s charcoal pieces or carbons were consumed
by the fierce heat evolved; but the principle was established that an
electric current, so interrupted, was a vivid light-producer, and
might be made permanently so if a substance capable of resisting the
heat could be substituted for his charcoal tips, and a generator of
electricity of sufficient power and economy in use could be substituted
for his voltaic batteries or cells.
Upon these two essentials hung the future of the electric light. The
first essential, that of a substance at the ends of the wires or in the
midst of the electric circuit which would resist the heat, was soon met
by the use of specially prepared and hard graphite carbon tips, in the
shape of candles. But the second essential, a generator of electricity
cheaper and more powerful than the voltaic cell, was not met with till
the dynamo machine reached an advanced stage of perfection; that is,
about 1867.
[Illustration: ELECTRIC ARC LIGHT.]
The two grand essentials now being at command, invention of electric
light appliances went on rapidly upon two lines, eventuating in two
systems, which became known as arc lighting and incandescent lighting.
By 1879–80, the arc light was sufficiently advanced to meet with
favor as an illuminant for streets, railway stations, markets, and
any large spaces, in which places it became a substitute for gas and
other lights. The essential features of the arc light are: (1.) The
dynamo machine, situated in some central place, for the generation of
electricity. (2.) Conducting wires to carry the electricity throughout
the areas or to the places to be lighted. (3.) The arc lamp, which
may be suspended upon poles in the streets, or upon wires in stores
and other covered places. Its mechanism consists of two pencils or
candles of graphite carbon, very hard and incombustible, adjusted
above and below each other so that their tips or ends are very close
together, but not in contact. By means of a clockwork or simple gravity
device these carbon tips are brought into contact at the moment the
electric current is turned on, and then are slightly separated as
soon as the current has heated them. The air between the heated tips,
having also reached a high temperature, becomes a conductor, and the
electricity leaps in the form of an arc or curve through it, rendering
it brilliantly incandescent. Should the current be diminished in
strength for any reason, the above-mentioned clockwork or gravity
device brings the carbons a little closer together; and should the
current be increased, the carbons are separated a little wider; thus
the steadiness of the light is regulated. There are also various
automatic devices for thus regulating the proximity of the carbons
and maintaining the evenness of the glow. The power of an arc light
is measured by candles. An ordinary arc light under two amperes of
current gives a light equal to twenty-five candles, while under fifty
amperes of current it gives a light equal to twenty thousand candles.
In searchlights on board vessels, and where very large areas are to
be lighted, both heavier currents and larger carbons are used than
in the arc lamps for ordinary street purposes. No light surpasses
the arc light in brilliancy, excepting the magnesium light. There are
few cities in this country and Europe that do not employ the arc lamp
as a means of street, station, and large-area lighting, owing to its
superiority as an illuminant and the wonderful policing effect it has
upon the slum sections.
The incandescent lamp, or electric lighting by incandescence, underwent
a somewhat longer evolution at the hands of inventors than the arc
lamp, owing to the difficulty of finding a substance suitable for the
production of the necessary glow. The discovery of such substance may
be accredited to Edison more fully than to any other. The incandescent
or glow lamp is a glass bulb from which the air is exhausted. There
passes into the bulb a filament of carbon, which, after a turn or two
inside the bulb, passes out at the end through which it entered. When
a current from a voltaic battery is sent through this carbon filament,
it brings it, in the absence of oxygen within the bulb, to a high white
heat without combustion. The portion of this high white heat which is
radiated is the light-giving energy of the incandescent lamp. Metal
filaments were at first tried in the bulb, but they quickly burned
out. Carbon filaments were at length found to be the only ones capable
of resisting the heat. They moreover had the advantage of cheapness,
and of greater radiating energy than metals. Many substances, such as
silk, cotton, hair, etc., were used in the preparation of the carbon
filaments, but it was found that strips cut from the inside bark of the
bamboo gave, when brought to a white heat by an electric current and
then properly treated, the most tenacious and best conducting carbon
filament.
The quality of light produced by an incandescent lamp is a gentler glow
than that produced by the arc lamp, and in color more nearly resembles
the light of gas or the oil lamp. The incandescent light speedily
became for the home, hotel, hall, and limited covered area what the arc
light became for the street and railway station, and, if anything, the
former outstripped the latter in the extent and value of the industry
it gave rise to.
In the arc lamp, the carbon pencils have to be renewed daily. In the
incandescent lamp, the carbon filament, though very delicate, may last
for quite a time, because incandescence takes place in the absence
of oxygen. If the favor in which the electric light is held, and the
great extent of its use, rested solely on the question of cheapness of
production, such question would give rise to interesting debate. And,
indeed, the debate would continue, if the question were the superior
fitness of electric lighting for lighthouses and like service, where
extreme brilliancy does not seem to penetrate a thick atmosphere as
effectively as the more subdued glow of the oil lamp. But the debate
ceases when the question is as to the beauty and efficiency of the
electric light in the home, street, station, mine, on shipboard, and
the thousand and one other places in which it has come to be deemed
an essential equipment. In all such places the question of economy of
production and use is subordinate to the higher question of utility and
indispensability.
VII. ELECTRIC LOCOMOTION.
The dawn of the nineteenth century saw, as vehicles of locomotion,
the saddled hackney, the clumsy wagon, the ostentatious stage-coach,
the primitive dearborn, the lumbering carriage, the poetic “one-hoss
shay.” The universal energy was the horse. A new energy came with the
application of steam, and with it new vehicular locomotion,—easier,
swifter, stronger, for the most part cheaper, rendering possible what
was hitherto impossible as to time and distance.
This signal triumph of the century may not have been eclipsed by
the introduction of subsequent locomotive changes, but it was to be
supplemented by what, at the beginning, would have passed for the
idle dream of a visionary. The horse-car came, had its brief day, and
went out with all its inconveniences, cruelties, and horrors before,
in part, the traction-car, and, in part, the rapidly revolutionizing
energy of electricity.
[Illustration: ELECTRIC LOCOMOTIVE.]
The first conception of a railway to be operated by electricity dates
from about 1835, when Thomas Davenport, of Brandon, Vt., contrived
and moved a small car by means of a current from voltaic cells placed
within it. In 1851, Professor Page, of the Smithsonian Institution,
ran a car propelled by electricity upon the steam railway between
Washington and Baltimore, but though he obtained a high rate of speed,
the cost of supplying the current by means of batteries—the only means
then known—prohibited the commercial use of his method.
With the invention of the dynamo as an economic and powerful generator
of electricity, and also the invention of the motor as a means of
turning electrical energy to mechanical account, the way was open,
both in the United States and Europe, for more active investigation
of the question of electric-car propulsion. Between 1872 and 1887,
different inventors, at home and abroad, placed in operation several
experimental electric railways. Few of them proved practical, though
each furnished a fund of valuable experience. An underground electric
street railway was operated in Denver as early as 1885; but the one
upon the trolley plan, which proved sufficiently successful to warrant
its being called the first operated in the United States, was built
in Richmond, Va., in 1888. It gave such impetus to electric railway
construction that, in five years’ time, enormous capital was embarked,
and the new means of propulsion was generally accepted as convenient,
safe, and profitable.
The essential features of the electric railway are: (1.) The track of
two rails, similar to the steam railway, (2.) The cars, lightly yet
strongly built. (3.) The power-house, containing the dynamos which
generate the electricity. (4.) The feed-wire, usually of stout copper,
running the length of the tracks of the system, and supported on
poles or laid in conduits. (5.) The trolley-wire over the centre of
the track, supported by insulated cross-wires passing from poles on
opposite sides of the tracks, and connected at proper intervals with
the feed-wire. (6.) The trolley-pole of metal jointed to the top of
the car, and fitted with a spring which presses the wheel on the end
of the pole up against the trolley-wire with a force of about fifteen
pounds, and which also serves to conduct the electricity down through
the car to the motor. (7.) The motor, which is suspended from the car
truck, and passes its power to the car axle by means of a spur gearing.
The power requisite for an ordinary trolley-car is about fifteen
horse-power. The speed of trolley-cars is regulated in cities to from
five to seven miles per hour, but they may be run, under favorable
conditions, at a speed equal to, or in excess of, that of the steam-car.
As a means of city transit, and of rapid, convenient, and economic
intercourse between suburban localities and rural towns and villages,
the electric traction system ranks as one of the greatest wonders of
the century. The speed with which it found favor, the enormous capital
it provoked to activity, the stimulus it gave to further study and
invention, the surprising number of passengers carried, go to make
one of the most interesting chapters in electric annals. The end of
the century sees thousands of these electric roads in existence; a
comparatively new industry involving over $100,000,000; a passenger
traffic running into the billions of people; a prospect that the
trolley will succeed the steam-car for all utilizable purposes within
the gradually extending influence of cities and towns upon their rural
surroundings.
In speaking of the passing of the horse-car and its substitution by
the trolley, a distinguished writer has well said: “Humanity in an
electric-car differs widely from that in the horse-car, propelled
at the expense of animal life. It is more cheerful, more confident,
more awake to the energy at command, more imbued with the subtlety
and majesty of the propelling force. The motor confirms the ethical
fact that each introduction of a higher material force into the daily
uses of humanity lifts it to a broader, brighter plane, gives its
capabilities freer and more wholesome play, and opens fresh vistas for
all possibilities. We applaud Franklin for seizing the lightning in
the heavens, dragging it down to earth, and subjugating it to man. Let
this pass as part of the poetry of physics. But when ethics comes to
poetize, let it be said that electricity as an applied force lifts man
up toward heaven, quickens all his appreciations of divine energy,
draws him irresistibly toward the centre and source of nature’s forces.
There is no dragging down and subjugation of a physical force. There
is only a going out, or up, of genius to meet and to grasp it. Its
universal application means the raising of mankind to its plane. If
electricity be the principle of life, as some suppose, what wonder that
we all feel better in an electric-car than any other? The motor becomes
a sublime motive. God himself is tugging at the wheels, and we are
riding with the Infinite.”
[Illustration: ELECTRIC RAILWAY. THIRD RAIL SYSTEM.]
Enthusiasts say the trolley is only the beginning of electric
locomotion, and that there is already in rapid evolution an electric
system which will supersede steam even for trunk-line purposes. In
vision, it presumes a speed of one hundred and twenty-five miles an
hour instead of forty; greater safety, cleanliness, and comfort; and
what is most momentous and startling, an economy in construction and
operation which will warrant the sacrifice of the billions of dollars
now invested in steam-railway properties. The proposition is not to
sacrifice the steam-railway track, but to add to it a third rail, which
is to carry the electric current. Then, by means of feed-conduits
alongside of the track, and specially constructed electric locomotives
and cars, the system is supposed to reach the practical perfection
claimed for it. Experiments with such an electrical system, made upon
branch lines of some of our trunk-line railways, as the Pennsylvania,
New York Central, and New Haven & Hartford, give much encouragement to
the hypothesis that it may become the next great step in the evolution
of electrical science.
Another means of electric propulsion was provided by the investigations
of Planté, which resulted in his invention of the “accumulator” or
“storage battery,” in 1859. His battery consists of plates of lead
immersed in dilute sulphuric acid. By the passage of an electric
current through the acid, it is electrolytically decomposed. By
continuing the current for a time, first in one direction and then in
another, the lead plates become changed, the one at the point where
the current leaves the cell taking on a deposit of spongy lead, and
the one at the point where the current enters the cell taking on a
coating of oxide of lead. When in this condition, the battery is said
to be stored, and is capable of sending out an electric current in any
circuit with which it may be connected. After exhausting itself, it can
be re-stored or re-charged in the same way as at first. Faure greatly
improved on Planté’s storage battery in 1880, by spreading the oxide
of lead over the plates, thus greatly reducing the time in forming the
plates. Subsequently, further improvements were made, till batteries
came into existence capable of supplying a current of many hundred
amperes for several hours. One of the first practical uses to which the
storage battery was put was in the propulsion of street-cars; but its
weight proved a drawback. It was found better adapted for the running
of boats on rivers, and, in the business of water-freightage for short
distances, has in many instances become a rival of steam. It found one
of its most interesting applications in helping to solve the problem
of the _automobile_, or “horseless carriage,” either for pleasure
purposes or for street traffic. In this problem it has, at the end of
the century, an active rival in compressed air; but as the “horseless
carriage” is rapidly coming into demand, means may soon be found to
utilize the strong and persistent energy of the storage battery,
without the drawback found in its great weight.
VIII. THE X RAY.
An astounding electrical revelation came during the last years of the
century through the discovery of the X, or unknown, or Roentgen ray. A
hint of this discovery was given by Faraday during his investigation
of the effect of electric discharges within rarefied gases. He also
invented the terms _anode_ and _cathode_, both of which are in
universal use in connection with instruments for producing the X rays;
the anode being the positive pole or electrode of a galvanic battery,
or, in general, the terminal of the conductor by which a current enters
an electrolytic cell; and the cathode being the negative pole or
electrode by which a current leaves said cell.