New Light on Edison’s Light

No tale in all the chronicles of American invention would seem to be better known than the story of Thomas Edison’s incandescent electric light. The electric light, after all, quickly became the epitome of the bright idea, and its creator was for more than fifty years the living symbol of America’s inventive genius. But in truth it is only in recent years that we have begun to piece together the complete story of history’s most famous invention.

That the full picture of Edison’s work on the electric light in the late 1870s should be obscure is a bit strange, for few inventions before the twentieth century are better documented. The records of the famous laboratory at Menlo Park, New Jersey, were voluminous and have been well preserved over the years. Dozens of laboratory notebooks, hundreds of drawings and sketches, a wealth of letters, patents, and other documents all give testimony to the work and lives of the light’s inventors. The importance of the effort to invent a practical electric light was widely evident to contemporary observers, so we have, in addition, an unusual number of journalists’ accounts of their trips out to Menlo Park. Finally, the fame that Edison achieved with not only this invention but also dozens of others made him an object of attention and adulation for more than half a century after. Journalists, biographers, popularizers, and other writers besieged Edison with regularity, and accounts of the invention of the electric light were among their most popular works. So how can there be more to be known about such an event?

It is perhaps because there has been too much information. The vast numbers of documents, now residing in a large vault at Edison’s last laboratory, in West Orange, New Jersey, have so intimidated scholars and other researchers that few have attempted a careful combing of them for evidence. The reports in newspapers were always better sources of color and human interest than of reliable technical information. And the half-century of interviews has resulted in a tale jumbled by romantic recollection and the faulty memories of old men.

From all of this have come two pictures of the electric light’s creator. The one that has the larger place in the public mind is of the rough-and-ready inventor whose pursuit of the electric light was a dogged hunt through nature’s storehouse, a tireless search through thousands of possible substances for the right filament to make a light bulb work. The second, and very different, image is that of the scientific-laboratory chief, a prototype of the modern research manager, who was guided by a vision of a complete electric light and power system and who left the technical details to a skilled, educated staff. As contradictory as these two pictures are, both of them—or some fuzzy composite of the two—have a firm place in not only the popular mythology but in the history books as well.

The new, clearer picture that we are now piecing together comes from a systematic search through the archives at West Orange. For the first time, scholars are recognizing the great potential of the Edison records for revealing the character of the great technological transformations that made over American society in the last decades of the nineteenth century and the first years of the twentieth. Invention, it turns out, is neither a haphazard tinkering nor is it a mechanical application of scientific knowledge. It is a very human activity, filled with the accomplishments and the failings of most endeavors.

The story of the invention of the electric light is a chronicle of people in the midst of the most exciting creative challenge of their lives, working at a frontier of technology. Edison and his colleagues were participants in an enterprise that was part puzzle-solving, part system-building, and part hoopla. When Thomas Edison began to think seriously about the problem of the electric light, he was only thirty-one years old, but already he was the most famous inventor in America. Beginning with an improved stock ticker in 1869, his contributions to telegraphy had made him indispensable to the financiers who controlled the most visible “high technology” of the day. In 1876 he had taken his profits and built in the New Jersey countryside an “invention factory,” promising a “minor invention every ten days and a big thing every six months or so.” The only thing more astonishing than the young Midwesterner’s bravado was his success. Challenged to find a way around Alexander Graham Bell’s telephone patents, Edison devised the carbon telephone transmitter and other components for telegraphy’s latest wrinkle. Experimenting with means for recording telegraph signals, he came up with his most surprising invention, the phonograph. With this last wonder, Edison became a celebrity.

The burdens of being a celebrity were little different in the 1870s from today. By the middle of 1878 Edison was described as “very tired and ill,” worn out by traveling around the country showing off the “machine that talked.” That summer he sought a break and took off to the West with a group of scientists who invited him to accompany them to Wyoming to view a solar eclipse. The vacation was, apparently, a great tonic, but conversations with the scientists turned Edison’s attention to a new challenge: creating a practical electric light to replace the gas and oil lamps used everywhere.

When he returned east, Edison headed to the workshop of William Wallace in Connecticut. There Wallace, the country’s premier brass founder, had on display an electric arc lighting system of his own devising. The newspaper reporter who tagged along described the scene: “Mr. Edison was enraptured … eight electric lights were kept ablaze at one time, each being equal to 4,000 candles, the sub-division of electric lights being a thing unknown to science. This filled up Mr. Edison’s cup of joy. He sprawled over the table with the simplicity of a child, and made all kinds of calculations.” The source of Edison’s pleasure was not simply what he saw in Connecticut; it was also what he didn’t see. A few weeks later he explained to a newspaper reporter: “I saw the thing had not gone so far but that I had a chance.… The intense light had not been subdivided so that it could be brought into private homes.” Edison was certain that he could “subdivide the light.”

There were known to inventors two ways to derive light from electricity. The first was the electric arc, a blindingly bright spark sustained between two pieces of carbon. This was the form of light made by William Wallace and a host of other inventors. By the 1870s the availability of practical (though very inefficient) generators made the use of arc lights possible in large public areas, in lighthouses, and on streets. By its nature the electric arc was many times brighter than an ordinary interior lamp—perhaps four thousand candlepower as compared with the ten or twenty of gaslight. The other form of electric light used a current to heat up a material so hot that it became “incandescent.” It was well known that an incandescent light, if sustained, could be made moderate enough for common indoor usage. But all substances that could be heated to incandescence were in the process either melted or burned up in the heat. This had been demonstrated by the futile efforts of inventors for several decades. Two distinct approaches emerged: one was to use a material with a moderately high melting point that did not oxidize, such as platinum. This substance, unfortunately, always got too hot and melted despite clever devices to prevent this. The other approach was to use a substance whose melting point was so high as to pose no problem. Carbon was the obvious candidate for this option, but despite the use of vacuum pumps or inert gases, no one had managed to sufficiently protect the carbon in a lamp from combustion.

This was the state of affairs that allowed the newspapers to remark that subdivision—the making of small electric lights —was “unknown to science.” Here was a challenge that the superconfident Edison felt was both worthy and ripe. Upon his return to Menlo Park he plunged into several days of intensive experimenting. With the help of his closest assistant, Charles Batchelor, a clever and nimble-fingered Englishman, Edison constructed several lamps using spirals of platinum wire as “burners.” These devices were distinguished by regulating mechanisms designed to cut off the current if the platinum approached its melting point. These regulators were combinations of electromagnets, switches, resistances, and levers, familiar features of Edison’s telegraph inventions. Certain that finding the right sort of regulator posed little problem, Edison brashly announced that in a matter of weeks he would have all problems in hand.

Nothing emerges more vividly out of the laboratory records, letters, and newspaper interviews from Menlo Park in the early fall of 1878 than Edison’s supreme confidence. The confidence was infectious, and Edison’s announcement was greeted on the stock exchanges by a precipitious fall in gas stocks and by a clamor from some to secure a piece of the new technology.

Little time was wasted in organizing the Edison Electric Light Company, among whose backers were J. P. Morgan and the Vanderbilt interests. The company assured Edison the funds he needed to perfect his invention, including resources to expand Menlo Park and hire experts. All of this was comforting to Edison, and for several weeks the workers at Menlo Park went about constructing models of the new lamp, testing generators to power the system, and preparing patent applications. Only one problem clouded the picture—the light didn’t work. Dozens of regulators were made, using several approaches, all designed to cut off current to the platinum wires or strips as they exceeded safe temperatures. The platinum was formed into a variety of shapes, with the intent of conserving the heat energy put into the lamp while allowing the maximum amount of light to be emitted. In every case the lamp flickered intolerably, the burner melted or broke, or the light was too faint. At this point Edison had made little effort to systematically inveJ. P. Morganstigate prior work on incandescent lights or to work out the various elements of the generation and distribution system that he would need. By late fall it was apparent that what he didn’t know about electric lighting was at least as important as what he did.

Unfortunately for the inventor’s giant ego, this was as clear to some of his financial backers as it was to Edison. In November, therefore, Edison was prevailed upon to hire a young Princeton-trained physicist, Francis Upton, recently returned from graduate training in Germany. In later years some claimed that Upton, with his advanced knowledge of mathematics and physics, was the key member of the Menlo Park team, and this claim has become part of the image of Edison’s laboratory as a modern scientific establishment. Upton was unquestionably valuable, for he was sharp, eager, and ambitious. But the electric light did not depend on the latest knowledge of physics. Upton’s hiring was more important for what it said about Edison and his new line of attack in late 1878 than for the advanced learning it brought to the project. Edison now resolved to find out all he could about every aspect of lighting systems. He and his workers studied old patents, analyzed the work of current rivals, subscribed to the gaslight journals, and set about to begin all over again, still confident but now driven by both the challenges before them and the promises behind them.

At just this point, as the year was ending and the work in the laboratory began to take on the rhythm of a long, hard slog, a technical discovery was made that would set Edison’s system apart from all others and provide a key to long-term success. In looking at some rival efforts, Edison and his associates noticed that the amount of electrical current required to operate the systems was quite large. Since Edison was determined to make a lamp that could be used with all the convenience of gaslight and, in particular, could be turned on and off without affecting other lamps, he realized that the lamps would have to be on a “parallel” circuit. In such a circuit, as opposed to a “series” circuit, electric current would be delivered independently to each lamp from the main wires of the circuit. This much was generally known, but the team at Menlo Park observed something else. If a circuit had many lamps on it (and Edison always felt that would be the only economical approach), the delivery of sufficient energy to light each lamp would require either a high voltage or a large current (energy equals voltage times current). Large currents, which everyone else’s system relied on, could be carried only by large conductors—resulting in an enormously expensive use of copper. A combination of smaller currents and large voltages would require that each lamp have a high resistance (voltage equals current times resistance). Edison thus decided that his lamp would have to have a high-resistance burner.

This compounded the technical challenge, however. Short pieces of platinum had low resistances, so long spirals of thin thin platinum wire were required. The spirals, on the other hand, always broke easily once they were heated to incandescence. For many months in 1879 Edison and his co-workers struggled to make spirals that would last, all to little avail. Only one thing seemed to improve matters. When the platinum burner was enclosed in a glass globe and the best vacuum pump available had exhausted the air, the life of the glowing burner was measurably longer—reaching a few hours. Edison’s response to this discovery was typical: he insisted on having the finest vacuum pump possible and hired a glassblower to make it and keep it operating.

As 1879 dragged on, progress on the lamp was frustratingly slow. Still, Edison’s confidence never flagged. He set his workers to designing and building the other pieces of equipment that would be necessary to make the light work. Much time and energy went into constructing a generator for a high-voltage system, and the result in the summer of 1879 was a radical new design that was the most efficient in the world. Smaller details were not forgotten as Menlo Park yielded meters, switches, fuses, insulators, and other paraphernalia.

All this took place in the public eye. Even though Edison’s early claims of the imminent demise of gas lighting were now discounted and a few voices of disenchantment could be heard, the general fascination with the happenings in the rural New Jersey laboratory was still lively. This was in part due to the continuing backing of Wall Street for Edison’s efforts, although mutterings of dismay were being heard even there. The main source of wonderment, however, was Edison himself and the still fresh image of the Wizard of Menlo Park. The press loved it, of course, and Edison was ever mindful of the advantages of a reputation for working miracles. Eager readers devoured reporters’ descriptions of laboratory life, as in this story from the New York Herald of January 17, 1879:

“The ordinary rules of industry seem to be reversed at Menlo Park.… At six o’clock in the evening the machinists and electricians assemble in the laboratory. Edison is already present, attired in a suit of blue flannel, with hair uncombed and straggling over his eyes … his hands and face somewhat begrimed and his whole air that of a man with a purpose and indifferent to everything save that purpose. By a quarter past six the quiet laboratory has become transformed into a hive of industry. The hum of machinery drowns all other sounds and each man is at his particular post.… Edison himself flits about, first to one bench, then to another, examining here, instructing there; at one place drawing out new fancied designs, at another earnestly watching the progress of some experiment. Sometimes he hastily leaves the busy throng of workmen and for an hour or more is seen by no one.… In these moments he is rarely disturbed. If any important question of construction arises on which his advice is necessary the workmen wait. Sometimes they wait for hours in idleness, but at the laboratory such idleness is considered far more profitable than any interference with the inventor while he is in the throes of invention …”

The main laboratory at Menlo Park was a two-story white clapboard building one hundred feet long and thirty feet wide. Most of the activity was on the second floor, a single room lined with bottle-laden shelves and filled with tables cluttered with electrical and chemical apparatus. The most conspicuous feature of the room was a large pipe organ on the back wall, a gift from an admirer who felt Edison and “the gang” needed some diversion in their long nights of work. The sound of organ music in the middle of the night coming from the hilltop building marked by the occasional strange glow from the windows heightened the mysterious atmosphere that seemed to surround Menlo Park. When, in May 1879, Edison publicly announced a worldwide search for new sources of platinum, a New York tabloid featured him on its cover, complete with wizard’s robe and hat. Never before or since was one man or one place so closely identified with the strange miracles of the modern age.

In mid-1879, however, it looked as though only a true miracle would salvage the reputation of Menlo Park. The platinum lamp simply could not be made to work. When investors insisted on inspecting the work that had already cost them tens of thousands of dollars, Edison’s staff made a number of low-resistance lamps that, at best, lasted a few hours. High-resistance devices were impossible to keep glowing for any time at all. The only thing that improved the behavior of the lamps was increasing the vacuum in their bulbs, so better vacuum pumps continued to be made. By fall Edison had reached the limits for improving the platinum lamp.

Such limits are constantly encountered in the chronicles of human creativity. An individual, driven by vision, imagination, and ambition into new and uncharted territory, will often reach the boundaries of the possibilities held out by a once promising direction. What then determines the changes in direction that yield up the special prize—the creation that makes a difference in the world and that marks the creator forever as different from his fellows? In the case of Edison’s electric light, as in so many others, this is not an easily solved puzzle. In October 1879, faced with the unhappy results of more than a year of arduous and expensive labor, Edison changed direction. In a matter of weeks, the missing element of his invention was put in place; no one from that time forth was allowed to doubt the success of the electric light.

The missing element was carbon. But this time it was not the carbon lamp tried by dozens of inventors before, only to burn up or disintegrate—it was carbon in the incredibly high vacuum of Edison’s bulbs. Carbon was a familiar material, indispensable to the telephone inventions that still occupied Edison’s attention from time to time. In the middle of October, Batchelor and Upton jotted down in their notebooks measurements of carbon’s resistance and some ideas on how it might be shaped into spirals. The efforts to make spirals, however, turned out to be fruitless—they always broke in the attempt to put them in bulbs. Finally, on the twenty-second of the month, Batchelor recorded “some very interesting experiments” using just a few inches of carbonized cotton thread. Put into a lamp, the short length of thread measured a resistance of a hundred ohms—many times that of platinum. What was more, the carbon lamp glowed almost as brightly as a gas lamp without flickering out.

One of the legends to grow up around the electric light was the story of a lamp, lit on October 21 and lasting forty hours, that provided a moment of clear triumph for the group at Menlo Park. For many years, electric companies celebrated the date as Electric Light Day, and October 21, 1929, was chosen as the day to honor Edison at Light’s Golden Jubilee. But records from the laboratory give no evidence of this “breakthrough” lamp. The dramatic moment was perhaps a necessary creation of the memories of people who, understandably, recalled in later years their work as a romantic quest, capped by a single shining moment. We learn, however, that invention is rarely romantic but instead shares the messiness and uncertainty of most creative human endeavors.

After a few more days of testing it became clear that the carbon lamp was the answer. During the next few weeks Edison and his assistants made variations on the new lamp to learn all they could about it. They clearly marveled at the result, for the lamp that emerged was as wonderful for its simplicity as for its light. A simple evacuated glass globe, in it mounted nothing but a short, black piece of carbonized sewing thread, the new lamp was very different from the bulky, expensive, and complex platinum devices around which the experimenters had built their hopes. Francis Upton, in a letter home in mid-November, exclaimed: “Just at the present 1 am very much elated at the prospects of the Electric Light. During the past week Mr. Edison has succeeded in obtaining the first lamp that answers the purpose we have wished. It is cheap—much more so than we ever hoped to have.”

Little time was wasted in letting the anxious investors know that an important discovery had been made. Several of them took the Pennsylvania Railroad to the little Menlo Park stop to see for themselves that Edison was not bluffing. The inventor showed an unusual reluctance, however, to let the press in on the story—at least until he was ready. Finally he invited a reporter to get a full account of the invention, swearing him to secrecy. When the New York Herald for December 21 appeared carrying Marshall Fox’s full-page story on the lamp, Edison was reported to be livid at the breach of confidence. The displeasure was short-lived, however, for, in truth, preparations for a public demonstration were well advanced. The workers in the laboratory had been kept busy for weeks making lamps, having discovered that bristol board made more reliable filaments than thread, while others had begun to install lamps in nearby homes, including Edison’s and Upton’s. A grand public display was scheduled for New Year’s Eve, and hundreds of the curious, aroused by a steady stream of newspaper stories, flocked to the laboratory, heedless of a winter storm.

The crowds that thronged into Menlo Park were made up of curiosity seekers and newshounds after the latest sensation. But they represented something more; they stood for a new relationship between advanced technology and the common man. Edison’s electric light was as mystifying and awe-inspiring as any invention of the age. Few things could have been more marvelous than the piece of charred paper glowing bright enough in its glass container to light up a room and yet not burning up. The magic represented by scientific technology was a source of unalloyed hope, not distrust. This attitude toward the powers of science and technology is one of the nineteenth century’s most important legacies, and no single instance better represents it than the enthusiasm with which the crowds ushered in the new decade at Menlo Park.