THE ELECTRIC LIGHT.
VOLTAIC ARC BY SIR HUMPHREY DAVY--THE JABLOCHKOFF CANDLE--PATENTS OF
BRUSH, WESTON AND OTHERS--SEARCH LIGHTS--GROVE’S FIRST INCANDESCENT
LAMP--STARR-KING LAMP--MOSES FARMER LIGHTS FIRST DWELLING WITH
ELECTRIC LAMPS--SAWYER-MAN LAMP--EDISON’S INCANDESCENT LAMP--
EDISON’S THREE-WIRE SYSTEM OF CIRCUITS--STATISTICS.
The popular idea of the electric light is, that it is a very recent
invention, since even the younger generation remembers when there was no
such thing in general use. It will surprise many readers, then, to know
that the electric light had its birth in the first decade of the
Nineteenth Century. In 1809 Sir Humphrey Davy discovered that when two
pieces of charcoal, which formed the terminals of a powerful voltaic
battery, were separated after having been brought into contact with each
other, at the moment of separation a brilliant arc of flame passed from
one piece of charcoal to the other, producing a temperature of 4,800°
F., and that the intensity of the light exceeded all other known forms
of light. Various improvements in the organization of devices were made
for holding the two pieces of carbon, which in time assumed the form of
two pencils in alignment, as in Fig. 40, and devices were provided for
feeding one carbon toward the other as they burned away. Clock mechanism
for thus regulating the feed was first employed, which served to
automatically keep the carbons a definite distance apart, this being a
necessary condition of the arc. For many years, however, the use of such
a light was confined to laboratory illustration, for the reason that it
could only be produced at great expense by a large number of voltaic
batteries. Nevertheless very efficient electric lamps working by voltaic
batteries were devised by Foucault, Duboscq, Deleuil and others as early
as 1853. With the advent of the dynamo, however, the electric light grew
rapidly and developed into conspicuous use. Even before the true dynamo
was invented the magneto-electric machine was employed for producing an
electric current to supply electric light. The so-called “Alliance”
generator was, in 1858, used in the South Foreland lighthouse in England
to supply the arc lamps, and the beams of the electric light then, for
the first time, were turned seaward as a beacon for the mariner.
[Illustration: FIG. 40.--SIMPLE ELECTRIC ARC LAMP.]
[Illustration: FIG. 41.--JABLOCHKOFF CANDLE.]
[Illustration: FIG. 42.--WESTON ARC LAMP.]
Among the early developments of the electric light was the Jablochkoff
candle, see Fig. 41, brought out in 1877. In this device two parallel
sticks of carbon G G were separated by a non-conducting layer of kaolin
I, and were held in an asbestos ferrule A. Metal tubes T T connected the
conducting wires F F to the carbons. The arc of flame passed from the
top of one carbon to the other, fusing the separating layer of kaolin,
and the whole burned down together as a candle. This form of electric
light was extensively used in Paris in 1877, and also in London, and
attracted considerable attention.
[Illustration: FIG. 43.--ARC LAMP FEED MECHANISM.]
From the Jablochkoff candle the arc light has resumed the form of two
vertically aligned carbons, and after passing through various forms and
patterns, of which the Weston lamp, Fig. 42, is a modern type, has come
into such universal and conspicuous use for lighting the streets of our
cities, and is so well known to-day, that but little need be said of its
development, since its real character has undergone no change in
principle, the improvements relating chiefly to means for regulating the
feed of the carbons and maintaining them at a uniform distance apart, so
as to avoid flickering. This result is obtained by automatic mechanism
operated by the electric current acting upon electro-magnets, as shown
in Fig. 43, in which the electro-magnets raise the upper carbon when it
is too close to the lower carbon, and lower the upper carbon when the
space becomes too great from burning away. Among those who have
contributed to the development of the arc light the names of Brush,
Weston, and Thomson and Houston are most conspicuous, and the patents of
Brush, No. 203,411, May 7, 1878, and No. 212,183, Feb. 11, 1879, and
Weston, No. 285,451, Sept. 25, 1883, are the most representative
developments.
[Illustration: FIG. 44.--NINE THOUSAND CANDLE POWER ARC LAMP.]
The applications of the arc light have been brilliant beyond the dreams
of the most sanguine inventor. In the illustrations number 44, 45 and
46, is shown a gigantic electric light beacon manufactured by Henry
Lepaute, of Paris, and first exhibited in this country at the Chicago
World’s Fair, in 1893. It consists of two great lenses, each nine feet
in diameter, between which, in their focus, is placed a 9,000 candle
power arc light. The great lantern, Fig. 45, is carried by a vertical
shaft, which terminates at its lower end in a hollow drum, which latter
floats in a bath of mercury. Although the weight is estimated at several
tons, so sensitive is its poise on the mercury that the enormous lantern
may be easily rotated by the pressure of one’s finger. Each lens
consists of concentric segments, see Fig. 46, 190 in number, surrounding
a central disk, which together cause the rays to issue in parallel
lines. The nine-foot beam of light thus projected is of 90,000,000
candle power, and if placed at a sufficient altitude to avoid the
curvature of the earth’s surface, its light would be visible at the
range of 146.9 nautical miles.
[Illustration: FIG. 45.--NINETY MILLION CANDLE POWER BIVALVE LENS.]
[Illustration: FIG. 46.--FRONT VIEW OF LENS.]
Better known to the patrons of our excursion boats and the visitors to
our splendid battleships, are the electric search lights. The greatest
example of all search lights, however, is not to be found on the sea,
but in the picturesque altitudes of the Sierra Madres in Southern
California. At the summit of Mount Lowe, in the neighborhood of
Pasadena, is the largest search light in the world, shown in
illustration, Fig. 48. It is of 3,000,000 candle power, stands eleven
feet high, and its total weight is 6,000 pounds. Its light may be seen
for 150 miles out on the ocean, and as its powerful beam is thrown from
mountain top to mountain top hundreds of miles apart, it adds the
illumination of art to the sublimity of nature, and seems a fitting
jewel to this lofty crown of Mother Earth.
[Illustration: FIG. 47.--SEARCH LIGHT WITH MACHINE GUN REPELLING NIGHT
ATTACK OF TORPEDO BOAT.]
[Illustration: FIG. 48.--SEARCH LIGHT ON MOUNT LOWE, CALIFORNIA.]
Brilliant as is the arc lamp, far more in evidence is the incandescent
lamp. The little glass bulb with its tiny thread of light we find
everywhere. Popular opinion and the decision of the courts accord this
invention to Thomas A. Edison. The evolution of the incandescent lamp
is, however, interesting, and may be briefly sketched as follows:
[Illustration: FIG. 49.--FIRST INCANDESCENT LAMP, BY PROFESSOR GROVE,
1840.]
[Illustration: FIG. 50.--STARR-KING LAMP.]
In 1845 there appeared in the _Philosophical Magazine_ a description of
what was probably the first incandescent electric light. It was devised
in 1840 by William Robert Grove, the inventor of the Grove battery, and
is illustrated in Fig. 49. It is stated that he experimented and read by
it for hours. It was described as follows:
“A coil of platinum wire is attached to two copper wires, the lower
parts of which, or those most distant from the platinum, are well
varnished; these are fixed erect in a glass of distilled water, and
another cylindrical glass, closed at the upper end, is inverted over
them, so that its open mouth rests on the bottom of the former glass;
the projecting ends of the copper wires are connected with a voltaic
battery (two or three pairs of the nitric acid combination), and the
ignited wire now gives a steady light. Instead of making the wires pass
through the water, they may be fixed to metallic caps well luted to the
necks of a glass globe.”
In 1845 August King patented, in England, an incandescent lamp, having
an unsealed platinum burner, and also a carbon in a vacuum. Mr. King
acted as agent for an American inventor, Mr. Starr, and the lamp came
to be known as the Starr-King lamp, shown in Fig. 50. The burner was a
thin plate or pencil of carbon B, enclosed in a Torricellian vacuum at
the end of an inverted barometer tube, and held between the terminals of
the connecting wires leading to a battery. In 1859 Moses G. Farmer
lighted his house at Salem, Mass., by a series of subdivided electric
lights, which was the first private dwelling lighted by electricity, and
probably the first illustration of the feasibility of subdividing the
electric current through a number of electric lamps.
In 1877 William E. Sawyer applied for a United States patent for an
electric engineering and lighting system, and in January, 1878, entered
into a partnership with Albon Man, and the “Sawyer-Man” lamp, see Fig.
51, was produced. In this an incandescent rod of carbon was inclosed in
an atmosphere of nitrogen. This marked the beginning of a period of
great activity in this field, which finally resulted in the well known
form of electric lamp shown in Fig. 52, which was patented by Edison,
No. 223,898, January 27, 1880. The distinctive features of this lamp
consisted in a bowed filament of carbon of very thin, thread-like
character, which was made of paper or carbonized cellulose. This, when
sealed in a vacuum, would not burn away, but would give the proper
incandescence, and by its small transverse dimension and high
resistance to the current, permitted a proper distribution of the
electric current to a number of lamps, without a special regulator for
each lamp; and which could also be made so cheaply that the lamp could
be thrown away when the burner was finally broken. Edison’s claim on
this feature of the electric lamp was sharply contested in an
interference in the Patent Office by Sawyer and Man, with the decisions
alternating first in favor of one and then of the other, but which
finally resulted in the grant of a patent to Sawyer and Man, on May 12,
1885. A struggle then began in the courts, which on October 4, 1892,
terminated in a decision by the United States Court of Appeals (Edison
Electric Light Company vs. United States Lighting Company), awarding the
incandescent lamp to Edison.
[Illustration: FIG. 51.--SAWYER-MAN LAMP.]
[Illustration: FIG. 52.--EDISON’S ELECTRIC LAMP.
_A_--Exhausted globe. _B_--Carbon filament. _CC_--Wires sealed in glass.
_D_--Line of fusion of two parts of globe. _EF_--Insulating material.
_G_--Screw-threads. _HI_--Metal socket. _J_--Fixture arm _K_--Circuit
controlling key.]
In the early demonstration given by Edison great disturbance was caused
in the stock exchanges among the holders of gas shares, as the
sensational reportings in the press seemed to indicate that gas was to
be superseded entirely. This uneasiness on the London Stock Exchange
amounted on October 11, 1878, to a veritable panic, but while the
electric light has more than fulfilled the prophecy made for it in many
directions, gas shares still continue to be good stocks.
[Illustration: FIG. 53.--ELECTRIC LIGHT CIRCUIT.]
[Illustration: FIG. 54.--EDISON’S THREE WIRE SYSTEM OF ELECTRIC LIGHT
CIRCUITS.]
Closely allied to the practical use of the incandescent lamp is the
method of supplying and regulating the current from the dynamo. Although
the alternating current is used for arc light, only the continuous
current can be used for the incandescent lights, and the relation of
the dynamo and the incandescent lamps is shown in Fig. 53, in which L
represents the lamps between the main conducting wires leading from the
dynamo, which latter has the coils of the field magnets arranged in a
shunt or branch circuit, in which is interposed a regulator R in the
form of a resistance coil with movable switch lever, by which more or
less of the current is allowed to flow through the field magnet coils to
suit the work being done. In late years automatic regulators have been
provided for accomplishing this result. In Fig. 54 is shown what is
known as the Edison “three wire system,” patented March 20, 1883, No.
274,290. In this two dynamos are used as at D¹ D², and the three wires
emerge from the dynamos, one from the negative pole of one dynamo,
another from the positive pole of the other dynamo, and the third or
middle one is connected to both the other poles (positive and negative),
of the two dynamos. For purposes of illustration, this may be compared
to a three-storied arrangement of current, the upper wire representing
the third story, the middle wire the second story, and the bottom one
the first story. The fall from either story to the next represents the
working energy, but from the top wire to the bottom would be equal to a
fall from the third story to the first. The purpose of this arrangement
is to save expense in copper wire, for while three main wires are used
instead of two, the aggregate weight of the wires (when the lamps are
arranged as shown), may be made so much less than two heavy wires as to
make a very great saving in copper.
The uses of the incandescent light are legion. Besides those which are
of common observation it is used for lighting the interior of mines,
caves, and the dark apartments of ships, and does not foul the air. It
is also used by divers in submarine operations; in the formation of
advertising signs, and in pyrotechnics, but perhaps one of the most
extraordinary uses to which it has been put is in exploring the interior
of the human stomach and other cavities of the body, a patent for which
was granted to M. C. F. Nitze, No. 218,055, July 29, 1879.
When an electric lamp is arranged with the opposite ends of the carbon
burner connected, one to the outgoing, the other to the incoming wires
from a dynamo, so as to be bridged across, this arrangement is said to
be “in multiple” or “in parallel,” and the lamps bear the analogy of
horses drawing abreast, and when the opposite ends of the carbon burner
are placed in a gap or break in either the outgoing or the incoming
wire, the arrangement is said to be “in series,” and the lamps bear the
analogy of horses in tandem.
Explanation of electric nomenclature can best be given by the analogy in
hydrostatics of a stream of water passing in the hose pipe from a
fire-engine. The “watt” indicates the sum total unit of electrical power
for a definite period of time, and in the hose pipe would be
represented by the effective force of a definite volume of water,
passing at a definite pressure, during a definite period of time. “Volt”
is a pressure unit of electro-motive force, and would be represented by
the power of the engine. “Ampere” would be the quantity, or volume unit,
or cross section of the hose pipe, and the “ohm” would be the unit of
frictional resistance. The “watt” then would be the “volt” multiplied by
the “ampere”; thus 500 watts would be 10 amperes at 50 volts, or 50
amperes at 10 volts. Low tension circuits, such as are used for
incandescent lights, range from 100 to 240 volts and are harmless.
Trolley circuits are usually 500 volts, and will kill an animal, but are
not necessarily fatal to man. High tension currents from 2,000 to 5,000
volts, such as are used for arc lights, are fatal.
Of all modern inventions, not one has advertised itself in such a
spectacular way as the electric light. Those who have seen the
magnificent electrical displays at the Chicago Fair, the electrical
celebrations in New York, and the Omaha Exhibition, need no introduction
to its marvelous splendors and beauties. In the annual report for 1898
of the Edison Electric Illuminating Company of New York, its statement
shows that for that city alone the gross earnings were $2,898,021. There
were 9,990 users of the electric light, 443,074 incandescent lamps, and
7,353 arc lights. It is estimated that the electric light stations and
plants in the United States alone amount to $600,000,000. In the year
1899 a single manufacturing concern (The General Electric Company)
received orders for 10,000,000 incandescent lamps, which is about
one-half of the present annual production. Sixteen years ago the lamps
were $1 each; to-day they can be bought for 18 cents.
What the future has in store for the further development of the electric
light no one may dare predict. Already a different form or manifestation
of electric light has been demonstrated, in which neither the electric
arc nor the incandescent filament is used, but a peculiar glow is seen
disassociated from a direct material habitation, and produced by
currents of enormous frequency and high potential, in accordance with
the patent to Tesla, No. 454,622, June 23, 1891. Other worthy inventors
in this field are at work, and its development will be one of the
interesting problems of the Twentieth Century.