THE INVENTION OF THE INCANDESCENT LAMP
IT is possible to imagine a time to come when the hours of work and rest
will once more be regulated by the sun. But the course of civilization
has been marked by an artificial lengthening of the day, and by a
constant striving after more perfect means of illumination. Why mankind
should sleep through several hours of sunlight in the morning, and
stay awake through a needless time in the evening, can probably only be
attributed to total depravity. It is certainly a most stupid, expensive,
and harmful habit. In no one thing has man shown greater fertility of
invention than in lighting; to nothing does he cling more tenaciously
than to his devices for furnishing light. Electricity to-day reigns
supreme in the field of illumination, but every other kind of artificial
light that has ever been known is still in use somewhere. Toward its
light-bringers the race has assumed an attitude of veneration, though it
has forgotten, if it ever heard, the names of those who first brightened
its gloom and dissipated its darkness. If the tallow candle, hitherto
unknown, were now invented, its creator would be hailed as one of the
greatest benefactors of the present age.
Up to the close of the eighteenth century, the means of house and street
illumination were of two generic kinds--grease and oil; but then came
a swift and revolutionary change in the adoption of gas. The ideas and
methods of Murdoch and Lebon soon took definite shape, and "coal smoke"
was piped from its place of origin to distant points of consumption.
As early as 1804, the first company ever organized for gas lighting was
formed in London, one side of Pall Mall being lit up by the enthusiastic
pioneer, Winsor, in 1807. Equal activity was shown in America, and
Baltimore began the practice of gas lighting in 1816. It is true that
there were explosions, and distinguished men like Davy and Watt opined
that the illuminant was too dangerous; but the "spirit of coal" had
demonstrated its usefulness convincingly, and a commercial development
began, which, for extent and rapidity, was not inferior to that marking
the concurrent adoption of steam in industry and transportation.
Meantime the wax candle and the Argand oil lamp held their own bravely.
The whaling fleets, long after gas came into use, were one of the
greatest sources of our national wealth. To New Bedford, Massachusetts,
alone, some three or four hundred ships brought their whale and sperm
oil, spermaceti, and whalebone; and at one time that port was accounted
the richest city in the United States in proportion to its population.
The ship-owners and refiners of that whaling metropolis were slow to
believe that their monopoly could ever be threatened by newer sources of
illumination; but gas had become available in the cities, and coal-oil
and petroleum were now added to the list of illuminating materials. The
American whaling fleet, which at the time of Edison's birth mustered
over seven hundred sail, had dwindled probably to a bare tenth when he
took up the problem of illumination; and the competition of oil from the
ground with oil from the sea, and with coal-gas, had made the artificial
production of light cheaper than ever before, when up to the middle
of the century it had remained one of the heaviest items of domestic
expense. Moreover, just about the time that Edison took up incandescent
lighting, water-gas was being introduced on a large scale as a
commercial illuminant that could be produced at a much lower cost than
coal-gas.
Throughout the first half of the nineteenth century the search for a
practical electric light was almost wholly in the direction of employing
methods analogous to those already familiar; in other words, obtaining
the illumination from the actual consumption of the light-giving
material. In the third quarter of the century these methods were
brought to practicality, but all may be referred back to the brilliant
demonstrations of Sir Humphry Davy at the Royal Institution, circa
1809-10, when, with the current from a battery of two thousand cells, he
produced an intense voltaic arc between the points of consuming sticks
of charcoal. For more than thirty years the arc light remained an
expensive laboratory experiment; but the coming of the dynamo placed
that illuminant on a commercial basis. The mere fact that electrical
energy from the least expensive chemical battery using up zinc and
acids costs twenty times as much as that from a dynamo--driven by
steam-engine--is in itself enough to explain why so many of the electric
arts lingered in embryo after their fundamental principles had been
discovered. Here is seen also further proof of the great truth that one
invention often waits for another.
From 1850 onward the improvements in both the arc lamp and the dynamo
were rapid; and under the superintendence of the great Faraday, in 1858,
protecting beams of intense electric light from the voltaic arc were
shed over the waters of the Straits of Dover from the beacons of South
Foreland and Dungeness. By 1878 the arc-lighting industry had sprung
into existence in so promising a manner as to engender an extraordinary
fever and furor of speculation. At the Philadelphia Centennial
Exposition of 1876, Wallace-Farmer dynamos built at Ansonia,
Connecticut, were shown, with the current from which arc lamps were
there put in actual service. A year or two later the work of Charles F.
Brush and Edward Weston laid the deep foundation of modern arc lighting
in America, securing as well substantial recognition abroad.
Thus the new era had been ushered in, but it was based altogether on the
consumption of some material--carbon--in a lamp open to the air. Every
lamp the world had ever known did this, in one way or another. Edison
himself began at that point, and his note-books show that he made
various experiments with this type of lamp at a very early stage.
Indeed, his experiments had led him so far as to anticipate in 1875 what
are now known as "flaming arcs," the exceedingly bright and generally
orange or rose-colored lights which have been introduced within the last
few years, and are now so frequently seen in streets and public places.
While the arcs with plain carbons are bluish-white, those with carbons
containing calcium fluoride have a notable golden glow.
He was convinced, however, that the greatest field of lighting lay in
the illumination of houses and other comparatively enclosed areas,
to replace the ordinary gas light, rather than in the illumination
of streets and other outdoor places by lights of great volume
and brilliancy. Dismissing from his mind quickly the commercial
impossibility of using arc lights for general indoor illumination,
he arrived at the conclusion that an electric lamp giving light by
incandescence was the solution of the problem.
Edison was familiar with the numerous but impracticable and commercially
unsuccessful efforts that had been previously made by other inventors
and investigators to produce electric light by incandescence, and at the
time that he began his experiments, in 1877, almost the whole scientific
world had pronounced such an idea as impossible of fulfilment. The
leading electricians, physicists, and experts of the period had been
studying the subject for more than a quarter of a century, and with but
one known exception had proven mathematically and by close reasoning
that the "Subdivision of the Electric Light," as it was then termed, was
practically beyond attainment. Opinions of this nature have ever been
but a stimulus to Edison when he has given deep thought to a subject,
and has become impressed with strong convictions of possibility, and
in this particular case he was satisfied that the subdivision of the
electric light--or, more correctly, the subdivision of the electric
current--was not only possible but entirely practicable.
It will have been perceived from the foregoing chapters that from the
time of boyhood, when he first began to rub against the world, his
commercial instincts were alert and predominated in almost all of the
enterprises that he set in motion. This characteristic trait had grown
stronger as he matured, having received, as it did, fresh impetus and
strength from his one lapse in the case of his first patented invention,
the vote-recorder. The lesson he then learned was to devote his
inventive faculties only to things for which there was a real, genuine
demand, and that would subserve the actual necessities of humanity; and
it was probably a fortunate circumstance that this lesson was learned
at the outset of his career as an inventor. He has never assumed to be a
philosopher or "pure scientist."
In order that the reader may grasp an adequate idea of the magnitude and
importance of Edison's invention of the incandescent lamp, it will be
necessary to review briefly the "state of the art" at the time he
began his experiments on that line. After the invention of the voltaic
battery, early in the last century, experiments were made which
determined that heat could be produced by the passage of the electric
current through wires of platinum and other metals, and through pieces
of carbon, as noted already, and it was, of course, also observed that
if sufficient current were passed through these conductors they could be
brought from the lower stage of redness up to the brilliant white heat
of incandescence. As early as 1845 the results of these experiments were
taken advantage of when Starr, a talented American who died at the early
age of twenty-five, suggested, in his English patent of that year, two
forms of small incandescent electric lamps, one having a burner made
from platinum foil placed under a glass cover without excluding the air;
and the other composed of a thin plate or pencil of carbon enclosed in
a Torricellian vacuum. These suggestions of young Starr were followed
by many other experimenters, whose improvements consisted principally in
devices to increase the compactness and portability of the lamp, in
the sealing of the lamp chamber to prevent the admission of air, and
in means for renewing the carbon burner when it had been consumed. Thus
Roberts, in 1852, proposed to cement the neck of the glass globe into a
metallic cup, and to provide it with a tube or stop-cock for exhaustion
by means of a hand-pump. Lodyguine, Konn, Kosloff, and Khotinsky,
between 1872 and 1877, proposed various ingenious devices for perfecting
the joint between the metal base and the glass globe, and also provided
their lamps with several short carbon pencils, which were automatically
brought into circuit successively as the pencils were consumed. In 1876
or 1877, Bouliguine proposed the employment of a long carbon pencil, a
short section only of which was in circuit at any one time and formed
the burner, the lamp being provided with a mechanism for automatically
pushing other sections of the pencil into position between the contacts
to renew the burner. Sawyer and Man proposed, in 1878, to make
the bottom plate of glass instead of metal, and provided ingenious
arrangements for charging the lamp chamber with an atmosphere of pure
nitrogen gas which does not support combustion.
These lamps and many others of similar character, ingenious as they
were, failed to become of any commercial value, due, among other things,
to the brief life of the carbon burner. Even under the best conditions
it was found that the carbon members were subject to a rapid
disintegration or evaporation, which experimenters assumed was due to
the disrupting action of the electric current; and hence the conclusion
that carbon contained in itself the elements of its own destruction, and
was not a suitable material for the burner of an incandescent lamp. On
the other hand, platinum, although found to be the best of all materials
for the purpose, aside from its great expense, and not combining with
oxygen at high temperatures as does carbon, required to be brought
so near the melting-point in order to give light, that a very slight
increase in the temperature resulted in its destruction. It was assumed
that the difficulty lay in the material of the burner itself, and not in
its environment.
It was not realized up to such a comparatively recent date as 1879 that
the solution of the great problem of subdivision of the electric current
would not, however, be found merely in the production of a durable
incandescent electric lamp--even if any of the lamps above referred to
had fulfilled that requirement. The other principal features necessary
to subdivide the electric current successfully were: the burning of an
indefinite number of lights on the same circuit; each light to give
a useful and economical degree of illumination; and each light to
be independent of all the others in regard to its operation and
extinguishment.
The opinions of scientific men of the period on the subject are well
represented by the two following extracts--the first, from a lecture at
the Royal United Service Institution, about February, 1879, by Mr. (Sir)
W. H. Preece, one of the most eminent electricians in England,
who, after discussing the question mathematically, said: "Hence the
sub-division of the light is an absolute ignis fatuus." The other
extract is from a book written by Paget Higgs, LL.D., D.Sc., published
in London in 1879, in which he says: "Much nonsense has been talked
in relation to this subject. Some inventors have claimed the power to
'indefinitely divide' the electric current, not knowing or forgetting
that such a statement is incompatible with the well-proven law of
conservation of energy."
"Some inventors," in the last sentence just quoted, probably--indeed,
we think undoubtedly--refers to Edison, whose earlier work in electric
lighting (1878) had been announced in this country and abroad, and
who had then stated boldly his conviction of the practicability of
the subdivision of the electrical current. The above extracts are good
illustrations, however, of scientific opinions up to the end of
1879, when Mr. Edison's epoch-making invention rendered them entirely
untenable. The eminent scientist, John Tyndall, while not sharing these
precise views, at least as late as January 17, 1879, delivered a lecture
before the Royal Institution on "The Electric Light," when, after
pointing out the development of the art up to Edison's work, and showing
the apparent hopelessness of the problem, he said: "Knowing something of
the intricacy of the practical problem, I should certainly prefer seeing
it in Edison's hands to having it in mine."
The reader may have deemed this sketch of the state of the art to be
a considerable digression; but it is certainly due to the subject to
present the facts in such a manner as to show that this great invention
was neither the result of improving some process or device that was
known or existing at the time, nor due to any unforeseen lucky chance,
nor the accidental result of other experiments. On the contrary, it was
the legitimate outcome of a series of exhaustive experiments founded
upon logical and original reasoning in a mind that had the courage and
hardihood to set at naught the confirmed opinions of the world,
voiced by those generally acknowledged to be the best exponents of the
art--experiments carried on amid a storm of jeers and derision, almost
as contemptuous as if the search were for the discovery of perpetual
motion. In this we see the man foreshadowed by the boy who, when he
obtained his books on chemistry or physics, did not accept any statement
of fact or experiment therein, but worked out every one of them himself
to ascertain whether or not they were true.
Although this brings the reader up to the year 1879, one must turn back
two years and accompany Edison in his first attack on the electric-light
problem. In 1877 he sold his telephone invention (the carbon
transmitter) to the Western Union Telegraph Company, which had
previously come into possession also of his quadruplex inventions,
as already related. He was still busily engaged on the telephone,
on acoustic electrical transmission, sextuplex telegraphs, duplex
telegraphs, miscellaneous carbon articles, and other inventions of a
minor nature. During the whole of the previous year and until late in
the summer of 1877, he had been working with characteristic energy and
enthusiasm on the telephone; and, in developing this invention to a
successful issue, had preferred the use of carbon and had employed it in
numerous forms, especially in the form of carbonized paper.
Eighteen hundred and seventy-seven in Edison's laboratory was a
veritable carbon year, for it was carbon in some shape or form for
interpolation in electric circuits of various kinds that occupied the
thoughts of the whole force from morning to night. It is not surprising,
therefore, that in September of that year, when Edison turned his
thoughts actively toward electric lighting by incandescence, his early
experiments should be in the line of carbon as an illuminant. His
originality of method was displayed at the very outset, for one of the
first experiments was the bringing to incandescence of a strip of carbon
in the open air to ascertain merely how much current was required.
This conductor was a strip of carbonized paper about an inch long,
one-sixteenth of an inch broad, and six or seven one-thousandths of an
inch thick, the ends of which were secured to clamps that formed the
poles of a battery. The carbon was lighted up to incandescence, and, of
course, oxidized and disintegrated immediately. Within a few days this
was followed by experiments with the same kind of carbon, but in vacuo
by means of a hand-worked air-pump. This time the carbon strip burned
at incandescence for about eight minutes. Various expedients to prevent
oxidization were tried, such, for instance, as coating the carbon with
powdered glass, which in melting would protect the carbon from the
atmosphere, but without successful results.
Edison was inclined to concur in the prevailing opinion as to the easy
destructibility of carbon, but, without actually settling the point in
his mind, he laid aside temporarily this line of experiment and entered
a new field. He had made previously some trials of platinum wire as
an incandescent burner for a lamp, but left it for a time in favor of
carbon. He now turned to the use of almost infusible metals--such as
boron, ruthenium, chromium, etc.--as separators or tiny bridges between
two carbon points, the current acting so as to bring these separators
to a high degree of incandescence, at which point they would emit a
brilliant light. He also placed some of these refractory metals directly
in the circuit, bringing them to incandescence, and used silicon in
powdered form in glass tubes placed in the electric circuit. His notes
include the use of powdered silicon mixed with lime or other very
infusible non-conductors or semi-conductors. Edison's conclusions on
these substances were that, while in some respects they were within the
bounds of possibility for the subdivision of the electric current, they
did not reach the ideal that he had in mind for commercial results.
Edison's systematized attacks on the problem were two in number, the
first of which we have just related, which began in September, 1877, and
continued until about January, 1878. Contemporaneously, he and his
force of men were very busily engaged day and night on other important
enterprises and inventions. Among the latter, the phonograph may be
specially mentioned, as it was invented in the late fall of 1877. From
that time until July, 1878, his time and attention day and night were
almost completely absorbed by the excitement caused by the invention and
exhibition of the machine. In July, feeling entitled to a brief vacation
after several years of continuous labor, Edison went with the expedition
to Wyoming to observe an eclipse of the sun, and incidentally to test
his tasimeter, a delicate instrument devised by him for measuring
heat transmitted through immense distances of space. His trip has been
already described. He was absent about two months. Coming home rested
and refreshed, Mr. Edison says: "After my return from the trip to
observe the eclipse of the sun, I went with Professor Barker, Professor
of Physics in the University of Pennsylvania, and Doctor Chandler,
Professor of Chemistry in Columbia College, to see Mr. Wallace, a large
manufacturer of brass in Ansonia, Connecticut. Wallace at this time was
experimenting on series arc lighting. Just at that time I wanted to take
up something new, and Professor Barker suggested that I go to work and
see if I could subdivide the electric light so it could be got in small
units like gas. This was not a new suggestion, because I had made a
number of experiments on electric lighting a year before this. They had
been laid aside for the phonograph. I determined to take up the search
again and continue it. On my return home I started my usual course of
collecting every kind of data about gas; bought all the transactions
of the gas-engineering societies, etc., all the back volumes of gas
journals, etc. Having obtained all the data, and investigated gas-jet
distribution in New York by actual observations, I made up my mind that
the problem of the subdivision of the electric current could be solved
and made commercial." About the end of August, 1878, he began his second
organized attack on the subdivision of the current, which was steadily
maintained until he achieved signal victory a year and two months later.
The date of this interesting visit to Ansonia is fixed by an inscription
made by Edison on a glass goblet which he used. The legend in diamond
scratches runs: "Thomas A. Edison, September 8, 1878, made under the
electric light." Other members of the party left similar memorials,
which under the circumstances have come to be greatly prized. A number
of experiments were witnessed in arc lighting, and Edison secured
a small Wallace-Farmer dynamo for his own work, as well as a set of
Wallace arc lamps for lighting the Menlo Park laboratory. Before leaving
Ansonia, Edison remarked, significantly: "Wallace, I believe I can beat
you making electric lights. I don't think you are working in the right
direction." Another date which shows how promptly the work was resumed
is October 14, 1878, when Edison filed an application for his first
lighting patent: "Improvement in Electric Lights." In after years,
discussing the work of Wallace, who was not only a great pioneer
electrical manufacturer, but one of the founders of the wire-drawing and
brass-working industry, Edison said: "Wallace was one of the earliest
pioneers in electrical matters in this country. He has done a great deal
of good work, for which others have received the credit; and the
work which he did in the early days of electric lighting others
have benefited by largely, and he has been crowded to one side and
forgotten." Associated in all this work with Wallace at Ansonia was
Prof. Moses G. Farmer, famous for the introduction of the fire-alarm
system; as the discoverer of the self-exciting principle of the modern
dynamo; as a pioneer experimenter in the electric-railway field; as a
telegraph engineer, and as a lecturer on mines and explosives to
naval classes at Newport. During 1858, Farmer, who, like Edison, was a
ceaseless investigator, had made a series of studies upon the production
of light by electricity, and had even invented an automatic regulator
by which a number of platinum lamps in multiple arc could be kept at
uniform voltage for any length of time. In July, 1859, he lit up one of
the rooms of his house at Salem, Massachusetts, every evening with such
lamps, using in them small pieces of platinum and iridium wire, which
were made to incandesce by means of current from primary batteries.
Farmer was not one of the party that memorable day in September, but his
work was known through his intimate connection with Wallace, and there
is no doubt that reference was made to it. Such work had not led
very far, the "lamps" were hopelessly short-lived, and everything was
obviously experimental; but it was all helpful and suggestive to one
whose open mind refused no hint from any quarter.
At the commencement of his new attempts, Edison returned to his
experiments with carbon as an incandescent burner for a lamp, and made
a very large number of trials, all in vacuo. Not only were the ordinary
strip paper carbons tried again, but tissue-paper coated with tar and
lampblack was rolled into thin sticks, like knitting-needles, carbonized
and raised to incandescence in vacuo. Edison also tried hard carbon,
wood carbons, and almost every conceivable variety of paper carbon in
like manner. With the best vacuum that he could then get by means of the
ordinary air-pump, the carbons would last, at the most, only from ten to
fifteen minutes in a state of incandescence. Such results were evidently
not of commercial value.
Edison then turned his attention in other directions. In his earliest
consideration of the problem of subdividing the electric current, he had
decided that the only possible solution lay in the employment of a lamp
whose incandescing body should have a high resistance combined with a
small radiating surface, and be capable of being used in what is called
"multiple arc," so that each unit, or lamp, could be turned on or off
without interfering with any other unit or lamp. No other arrangement
could possibly be considered as commercially practicable.
The full significance of the three last preceding sentences will not be
obvious to laymen, as undoubtedly many of the readers of this book may
be; and now being on the threshold of the series of Edison's experiments
that led up to the basic invention, we interpolate a brief explanation,
in order that the reader may comprehend the logical reasoning and work
that in this case produced such far-reaching results.
If we consider a simple circuit in which a current is flowing, and
include in the circuit a carbon horseshoe-like conductor which it is
desired to bring to incandescence by the heat generated by the current
passing through it, it is first evident that the resistance offered to
the current by the wires themselves must be less than that offered by
the burner, because, otherwise current would be wasted as heat in the
conducting wires. At the very foundation of the electric-lighting art is
the essentially commercial consideration that one cannot spend very much
for conductors, and Edison determined that, in order to use wires of a
practicable size, the voltage of the current (i.e., its pressure or
the characteristic that overcomes resistance to its flow) should be one
hundred and ten volts, which since its adoption has been the standard.
To use a lower voltage or pressure, while making the solution of the
lighting problem a simple one as we shall see, would make it necessary
to increase the size of the conducting wires to a prohibitive extent.
To increase the voltage or pressure materially, while permitting
some saving in the cost of conductors, would enormously increase the
difficulties of making a sufficiently high resistance conductor to
secure light by incandescence. This apparently remote consideration
--weight of copper used--was really the commercial key to the problem,
just as the incandescent burner was the scientific key to that problem.
Before Edison's invention incandescent lamps had been suggested as
a possibility, but they were provided with carbon rods or strips of
relatively low resistance, and to bring these to incandescence required
a current of low pressure, because a current of high voltage would pass
through them so readily as not to generate heat; and to carry a current
of low pressure through wires without loss would require wires of
enormous size. [8] Having a current of relatively high pressure to
contend with, it was necessary to provide a carbon burner which, as
compared with what had previously been suggested, should have a very
great resistance. Carbon as a material, determined after patient search,
apparently offered the greatest hope, but even with this substance the
necessary high resistance could be obtained only by making the burner
of extremely small cross-section, thereby also reducing its radiating
surface. Therefore, the crucial point was the production of a hair-like
carbon filament, with a relatively great resistance and small radiating
surface, capable of withstanding mechanical shock, and susceptible of
being maintained at a temperature of over two thousand degrees for a
thousand hours or more before breaking. And this filamentary conductor
required to be supported in a vacuum chamber so perfectly formed and
constructed that during all those hours, and subjected as it is to
varying temperatures, not a particle of air should enter to disintegrate
the filament. And not only so, but the lamp after its design must not
be a mere laboratory possibility, but a practical commercial article
capable of being manufactured at low cost and in large quantities. A
statement of what had to be done in those days of actual as well as
scientific electrical darkness is quite sufficient to explain Tyndall's
attitude of mind in preferring that the problem should be in Edison's
hands rather than in his own. To say that the solution of the problem
lay merely in reducing the size of the carbon burner to a mere hair, is
to state a half-truth only; but who, we ask, would have had the temerity
even to suggest that such an attenuated body could be maintained at a
white heat, without disintegration, for a thousand hours? The solution
consisted not only in that, but in the enormous mass of patiently
worked-out details--the manufacture of the filaments, their uniform
carbonization, making the globes, producing a perfect vacuum, and
countless other factors, the omission of any one of which would probably
have resulted eventually in failure.
[Footnote 8: As a practical illustration of these facts it
was calculated by Professor Barker, of the University of
Pennsylvania (after Edison had invented the incandescent
lamp), that if it should cost $100,000 for copper conductors
to supply current to Edison lamps in a given area, it would
cost about $200,000,000 for copper conductors for lighting
the same area by lamps of the earlier experimenters--such,
for instance, as the lamp invented by Konn in 1875. This
enormous difference would be accounted for by the fact that
Edison's lamp was one having a high resistance and
relatively small radiating surface, while Konn's lamp was
one having a very low resistance and large radiating
surface.]
Continuing the digression one step farther in order to explain the term
"multiple arc," it may be stated that there are two principal systems
of distributing electric current, one termed "series," and the other
"multiple arc." The two are illustrated, diagrammatically, side by side,
the arrows indicating flow of current. The series system, it will be
seen, presents one continuous path for the current. The current for the
last lamp must pass through the first and all the intermediate lamps.
Hence, if any one light goes out, the continuity of the path is broken,
current cannot flow, and all the lamps are extinguished unless a loop
or by-path is provided. It is quite obvious that such a system would be
commercially impracticable where small units, similar to gas jets, were
employed. On the other hand, in the multiple-arc system, current may be
considered as flowing in two parallel conductors like the vertical sides
of a ladder, the ends of which never come together. Each lamp is placed
in a separate circuit across these two conductors, like a rung in the
ladder, thus making a separate and independent path for the current in
each case. Hence, if a lamp goes out, only that individual subdivision,
or ladder step, is affected; just that one particular path for the
current is interrupted, but none of the other lamps is interfered with.
They remain lighted, each one independent of the other. The reader will
quite readily understand, therefore, that a multiple-arc system is the
only one practically commercial where electric light is to be used in
small units like those of gas or oil.
Such was the nature of the problem that confronted Edison at the outset.
There was nothing in the whole world that in any way approximated a
solution, although the most brilliant minds in the electrical art had
been assiduously working on the subject for a quarter of a century
preceding. As already seen, he came early to the conclusion that the
only solution lay in the use of a lamp of high resistance and small
radiating surface, and, with characteristic fervor and energy, he
attacked the problem from this standpoint, having absolute faith in
a successful outcome. The mere fact that even with the successful
production of the electric lamp the assault on the complete problem
of commercial lighting would hardly be begun did not deter him in the
slightest. To one of Edison's enthusiastic self-confidence the long
vista of difficulties ahead--we say it in all sincerity--must have been
alluring.
After having devoted several months to experimental trials of carbon,
at the end of 1878, as already detailed, he turned his attention to the
platinum group of metals and began a series of experiments in which he
used chiefly platinum wire and iridium wire, and alloys of refractory
metals in the form of wire burners for incandescent lamps. These metals
have very high fusing-points, and were found to last longer than the
carbon strips previously used when heated up to incandescence by the
electric current, although under such conditions as were then possible
they were melted by excess of current after they had been lighted a
comparatively short time, either in the open air or in such a vacuum as
could be obtained by means of the ordinary air-pump.
Nevertheless, Edison continued along this line of experiment with
unremitting vigor, making improvement after improvement, until about
April, 1879, he devised a means whereby platinum wire of a given length,
which would melt in the open air when giving a light equal to four
candles, would emit a light of twenty-five candle-power without fusion.
This was accomplished by introducing the platinum wire into an all-glass
globe, completely sealed and highly exhausted of air, and passing a
current through the platinum wire while the vacuum was being made.
In this, which was a new and radical invention, we see the first step
toward the modern incandescent lamp. The knowledge thus obtained that
current passing through the platinum during exhaustion would drive out
occluded gases (i.e., gases mechanically held in or upon the metal), and
increase the infusibility of the platinum, led him to aim at securing
greater perfection in the vacuum, on the theory that the higher the
vacuum obtained, the higher would be the infusibility of the platinum
burner. And this fact also was of the greatest importance in making
successful the final use of carbon, because without the subjection of
the carbon to the heating effect of current during the formation of the
vacuum, the presence of occluded gases would have been a fatal obstacle.
Continuing these experiments with most fervent zeal, taking no account
of the passage of time, with an utter disregard for meals, and but
scanty hours of sleep snatched reluctantly at odd periods of the day
or night, Edison kept his laboratory going without cessation. A great
variety of lamps was made of the platinum-iridium type, mostly with
thermal devices to regulate the temperature of the burner and prevent
its being melted by an excess of current. The study of apparatus for
obtaining more perfect vacua was unceasingly carried on, for Edison
realized that in this there lay a potent factor of ultimate success.
About August he had obtained a pump that would produce a vacuum up to
about the one-hundred-thousandth part of an atmosphere, and some time
during the next month, or beginning of October, had obtained one that
would produce a vacuum up to the one-millionth part of an atmosphere.
It must be remembered that the conditions necessary for MAINTAINING this
high vacuum were only made possible by his invention of the one-piece
all-glass globe, in which all the joints were hermetically sealed during
its manufacture into a lamp, whereby a high vacuum could be retained
continuously for any length of time.
In obtaining this perfection of vacuum apparatus, Edison realized that
he was approaching much nearer to a solution of the problem. In his
experiments with the platinum-iridium lamps, he had been working all
the time toward the proposition of high resistance and small radiating
surface, until he had made a lamp having thirty feet of fine platinum
wire wound upon a small bobbin of infusible material; but the desired
economy, simplicity, and durability were not obtained in this manner,
although at all times the burner was maintained at a critically high
temperature. After attaining a high degree of perfection with these
lamps, he recognized their impracticable character, and his mind
reverted to the opinion he had formed in his early experiments two years
before--viz., that carbon had the requisite resistance to permit a very
simple conductor to accomplish the object if it could be used in the
form of a hair-like "filament," provided the filament itself could be
made sufficiently homogeneous. As we have already seen, he could not use
carbon successfully in his earlier experiments, for the strips of carbon
he then employed, although they were much larger than "filaments,"
would not stand, but were consumed in a few minutes under the imperfect
conditions then at his command.
Now, however, that he had found means for obtaining and maintaining high
vacua, Edison immediately went back to carbon, which from the first
he had conceived of as the ideal substance for a burner. His next step
proved conclusively the correctness of his old deductions. On October
21, 1879, after many patient trials, he carbonized a piece of cotton
sewing-thread bent into a loop or horseshoe form, and had it sealed
into a glass globe from which he exhausted the air until a vacuum up to
one-millionth of an atmosphere was produced. This lamp, when put on
the circuit, lighted up brightly to incandescence and maintained its
integrity for over forty hours, and lo! the practical incandescent lamp
was born. The impossible, so called, had been attained; subdivision
of the electric-light current was made practicable; the goal had
been reached; and one of the greatest inventions of the century
was completed. Up to this time Edison had spent over $40,000 in his
electric-light experiments, but the results far more than justified the
expenditure, for with this lamp he made the discovery that the FILAMENT
of carbon, under the conditions of high vacuum, was commercially
stable and would stand high temperatures without the disintegration and
oxidation that took place in all previous attempts that he knew of
for making an incandescent burner out of carbon. Besides, this lamp
possessed the characteristics of high resistance and small radiating
surface, permitting economy in the outlay for conductors, and requiring
only a small current for each unit of light--conditions that were
absolutely necessary of fulfilment in order to accomplish commercially
the subdivision of the electric-light current.
This slender, fragile, tenuous thread of brittle carbon, glowing
steadily and continuously with a soft light agreeable to the eyes,
was the tiny key that opened the door to a world revolutionized in
its interior illumination. It was a triumphant vindication of Edison's
reasoning powers, his clear perceptions, his insight into possibilities,
and his inventive faculty, all of which had already been productive of
so many startling, practical, and epoch-making inventions. And now he
had stepped over the threshold of a new art which has since become so
world-wide in its application as to be an integral part of modern human
experience. [9]
[Footnote 9: The following extract from Walker on Patents
(4th edition) will probably be of interest to the reader:
"Sec. 31a. A meritorious exception, to the rule of the last
section, is involved in the adjudicated validity of the
Edison incandescent-light patent. The carbon filament, which
constitutes the only new part of the combination of the
second claim of that patent, differs from the earlier carbon
burners of Sawyer and Man, only in having a diameter of one-
sixty-fourth of an inch or less, whereas the burners of
Sawyer and Man had a diameter of one-thirty-second of an
inch or more. But that reduction of one-half in diameter
increased the resistance of the burner FOURFOLD, and reduced
its radiating surface TWOFOLD, and thus increased eightfold,
its ratio of resistance to radiating surface. That eightfold
increase of proportion enabled the resistance of the
conductor of electricity from the generator to the burner to
be increased eightfold, without any increase of percentage
of loss of energy in that conductor, or decrease of
percentage of development of heat in the burner; and thus
enabled the area of the cross-section of that conductor to
be reduced eightfold, and thus to be made with one-eighth of
the amount of copper or other metal, which would be required
if the reduction of diameter of the burner from one-thirty-
second to one-sixty-fourth of an inch had not been made. And
that great reduction in the size and cost of conductors,
involved also a great difference in the composition of the
electric energy employed in the system; that difference
consisting in generating the necessary amount of electrical
energy with comparatively high electromotive force, and
comparatively low current, instead of contrariwise. For this
reason, the use of carbon filaments, one-sixty-fourth of an
inch in diameter or less, instead of carbon burners one-
thirty-second of an inch in diameter or more, not only
worked an enormous economy in conductors, but also
necessitated a great change in generators, and did both
according to a philosophy, which Edison was the first to
know, and which is stated in this paragraph in its simplest
form and aspect, and which lies at the foundation of the
incandescent electric lighting of the world."]
No sooner had the truth of this new principle been established than
the work to establish it firmly and commercially was carried on
more assiduously than ever. The next immediate step was a further
investigation of the possibilities of improving the quality of the
carbon filament. Edison had previously made a vast number of experiments
with carbonized paper for various electrical purposes, with such good
results that he once more turned to it and now made fine filament-like
loops of this material which were put into other lamps. These proved
even more successful (commercially considered) than the carbonized
thread--so much so that after a number of such lamps had been made and
put through severe tests, the manufacture of lamps from these paper
carbons was begun and carried on continuously. This necessitated first
the devising and making of a large number of special tools for cutting
the carbon filaments and for making and putting together the various
parts of the lamps. Meantime, great excitement had been caused in this
country and in Europe by the announcement of Edison's success. In the
Old World, scientists generally still declared the impossibility of
subdividing the electric-light current, and in the public press Mr.
Edison was denounced as a dreamer. Other names of a less complimentary
nature were applied to him, even though his lamp were actually in
use, and the principle of commercial incandescent lighting had been
established.
Between October 21, 1879, and December 21, 1879, some hundreds of these
paper-carbon lamps had been made and put into actual use, not only in
the laboratory, but in the streets and several residences at Menlo Park,
New Jersey, causing great excitement and bringing many visitors from
far and near. On the latter date a full-page article appeared in the
New York Herald which so intensified the excited feeling that Mr. Edison
deemed it advisable to make a public exhibition. On New Year's Eve,
1879, special trains were run to Menlo Park by the Pennsylvania
Railroad, and over three thousand persons took advantage of the
opportunity to go out there and witness this demonstration for
themselves. In this great crowd were many public officials and men of
prominence in all walks of life, who were enthusiastic in their praises.
In the mean time, the mind that conceived and made practical this
invention could not rest content with anything less than perfection,
so far as it could be realized. Edison was not satisfied with paper
carbons. They were not fully up to the ideal that he had in mind. What
he sought was a perfectly uniform and homogeneous carbon, one like the
"One-Hoss Shay," that had no weak spots to break down at inopportune
times. He began to carbonize everything in nature that he could lay
hands on. In his laboratory note-books are innumerable jottings of the
things that were carbonized and tried, such as tissue-paper, soft paper,
all kinds of cardboards, drawing-paper of all grades, paper saturated
with tar, all kinds of threads, fish-line, threads rubbed with tarred
lampblack, fine threads plaited together in strands, cotton soaked in
boiling tar, lamp-wick, twine, tar and lampblack mixed with a proportion
of lime, vulcanized fibre, celluloid, boxwood, cocoanut hair and shell,
spruce, hickory, baywood, cedar and maple shavings, rosewood, punk,
cork, bagging, flax, and a host of other things. He also extended his
searches far into the realms of nature in the line of grasses, plants,
canes, and similar products, and in these experiments at that time
and later he carbonized, made into lamps, and tested no fewer than six
thousand different species of vegetable growths.
The reasons for such prodigious research are not apparent on the face of
the subject, nor is this the occasion to enter into an explanation, as
that alone would be sufficient to fill a fair-sized book. Suffice it
to say that Edison's omnivorous reading, keen observation, power of
assimilating facts and natural phenomena, and skill in applying the
knowledge thus attained to whatever was in hand, now came into full play
in determining that the results he desired could only be obtained in
certain directions.
At this time he was investigating everything with a microscope, and one
day in the early part of 1880 he noticed upon a table in the laboratory
an ordinary palm-leaf fan. He picked it up and, looking it over,
observed that it had a binding rim made of bamboo, cut from the outer
edge of the cane; a very long strip. He examined this, and then gave it
to one of his assistants, telling him to cut it up and get out of it
all the filaments he could, carbonize them, put them into lamps, and try
them. The results of this trial were exceedingly successful, far better
than with anything else thus far used; indeed, so much so, that after
further experiments and microscopic examinations Edison was convinced
that he was now on the right track for making a thoroughly stable,
commercial lamp; and shortly afterward he sent a man to Japan to procure
further supplies of bamboo. The fascinating story of the bamboo hunt
will be told later; but even this bamboo lamp was only one item of
a complete system to be devised--a system that has since completely
revolutionized the art of interior illumination.
Reference has been made in this chapter to the preliminary study that
Edison brought to bear on the development of the gas art and industry.
This study was so exhaustive that one can only compare it to the careful
investigation made in advance by any competent war staff of the elements
of strength and weakness, on both sides, in a possible campaign. A
popular idea of Edison that dies hard, pictures a breezy, slap-dash,
energetic inventor arriving at new results by luck and intuition, making
boastful assertions and then winning out by mere chance. The native
simplicity of the man, the absence of pose and ceremony, do much to
strengthen this notion; but the real truth is that while gifted with
unusual imagination, Edison's march to the goal of a new invention is
positively humdrum and monotonous in its steady progress. No one ever
saw Edison in a hurry; no one ever saw him lazy; and that which he did
with slow, careful scrutiny six months ago, he will be doing with just
as much calm deliberation of research six months hence--and six years
hence if necessary. If, for instance, he were asked to find the most
perfect pebble on the Atlantic shore of New Jersey, instead of hunting
here, there, and everywhere for the desired object, we would no doubt
find him patiently screening the entire beach, sifting out the most
perfect stones and eventually, by gradual exclusion, reaching the
long-sought-for pebble; and the mere fact that in this search years
might be taken, would not lessen his enthusiasm to the slightest extent.
In the "prospectus book" among the series of famous note-books, all the
references and data apply to gas. The book is numbered 184, falls into
the period now dealt with, and runs along casually with items spread
out over two or three years. All these notes refer specifically to
"Electricity vs. Gas as General Illuminants," and cover an astounding
range of inquiry and comment. One of the very first notes tells the
whole story: "Object, Edison to effect exact imitation of all done by
gas, so as to replace lighting by gas by lighting by electricity. To
improve the illumination to such an extent as to meet all requirements
of natural, artificial, and commercial conditions." A large programme,
but fully executed! The notes, it will be understood, are all in
Edison's handwriting. They go on to observe that "a general system of
distribution is the only possible means of economical illumination," and
they dismiss isolated-plant lighting as in mills and factories as of so
little importance to the public--"we shall leave the consideration of
this out of this book." The shrewd prophecy is made that gas will be
manufactured less for lighting, as the result of electrical competition,
and more and more for heating, etc., thus enlarging its market and
increasing its income. Comment is made on kerosene and its cost, and all
kinds of general statistics are jotted down as desirable. Data are to be
obtained on lamp and dynamo efficiency, and "Another review of the whole
thing as worked out upon pure science principles by Rowland, Young,
Trowbridge; also Rowland on the possibilities and probabilities of
cheaper production by better manufacture--higher incandescence without
decrease of life of lamps." Notes are also made on meters and motors.
"It doesn't matter if electricity is used for light or for power";
while small motors, it is observed, can be used night or day, and small
steam-engines are inconvenient. Again the shrewd comment: "Generally
poorest district for light, best for power, thus evening up whole
city--the effect of this on investment."
It is pointed out that "Previous inventions failed--necessities
for commercial success and accomplishment by Edison. Edison's great
effort--not to make a large light or a blinding light, but a small light
having the mildness of gas." Curves are then called for of iron
and copper investment--also energy line--curves of candle-power and
electromotive force; curves on motors; graphic representation of
the consumption of gas January to December; tables and formulae;
representations graphically of what one dollar will buy in different
kinds of light; "table, weight of copper required different distance,
100-ohm lamp, 16 candles"; table with curves showing increased
economy by larger engine, higher power, etc. There is not much that is
dilettante about all this. Note is made of an article in April, 1879,
putting the total amount of gas investment in the whole world at that
time at $1,500,000,000; which is now (1910) about the amount of the
electric-lighting investment in the United States. Incidentally a note
remarks: "So unpleasant is the effect of the products of gas that in the
new Madison Square Theatre every gas jet is ventilated by special tubes
to carry away the products of combustion." In short, there is no aspect
of the new problem to which Edison failed to apply his acutest powers;
and the speed with which the new system was worked out and introduced
was simply due to his initial mastery of all the factors in the older
art. Luther Stieringer, an expert gas engineer and inventor, whose
services were early enlisted, once said that Edison knew more about gas
than any other man he had ever met. The remark is an evidence of the
kind of preparation Edison gave himself for his new task.