To some men the material world is always presenting itself in the form of a series of fascinating puzzles, to be solved as one might work out a game of chess. The astronomer is given certain figures, and from those he intends to derive certain laws; the scientist knows the properties of certain materials and from those he is to reach some new combination that will produce a new result. He is not an inventor as much as he is a detective; he picks up the clews to certain happenings and constructs a working theory to fit them. In mechanics this theory that he constructs usually takes the form of a machine. And this machine is not so much a new discovery as it is the practical working-out of certain carefully-selected laws of nature.

Perhaps there has never been a man whose thoughts were so continually asking the question why as Thomas Alva Edison. Certainly there has never been one who has found the answer to that question in so many lines of scientific study. He has not merely happened on his discoveries. He has not been as much interested in the result as in the reasons for it. He belongs to the experimenting age. Once on a time men took the facts of nature for granted. But if they had always done so there would have been no telegraph, no telephone, no electric light, no phonograph. Each of these were achieved by working on a definite problem, and in no haphazard way. The inventor has become a scientist and a mechanic, and no longer an amateur discoverer. Chance has much less to do with the winning of new knowledge than it once had.

A visitor to Edison’s laboratory tells how he found him holding a vial of some liquid to the light. After a long look at it he put the vial down on the table, and resting his head in his hands, stared intently at it, as if he expected the vial to make some answer. Then he picked it up, shook it, and held it again to the light. The visitor introduced himself. Edison nodded toward the bottle. “Take a look at those filings,” said he. “See how curiously they settle when I shake the bottle. In alcohol they behave one way, but in oil in this way. Isn’t that the most curious thing you ever saw—better than a play at one of your city theatres, eh?” Again he shook the vial. “What I want to know is what they mean by it; and I’m going to find out.” There is the man, he wants to know “what they mean by it,” he continually asks the question why, he is the great experimenter among great inventors.

Edison has shown the calibre of his mind in a score of different ways. He has been showing it ever since the days when he was a newsboy on the trains of the Canadian Grand Trunk Railroad and the Michigan Central. Then he fitted up a corner of the baggage-car of his train as a miniature laboratory, and filled it with the bottles and retorts that had been discarded at the railroad workshops. Among his treasures was a copy of Fresenius’s “Qualitative Analysis,” engaging reading for a boy only twelve years old. But he was not only a chemist. When he was not working on the train he would be hanging about machine shops, listening and watching and considering. One day the manager of the Detroit Free Press told him he might have some three hundred pounds of old type that had been used up. The newsboy found an old hand-press and began to print a paper himself, called the Grand Trunk Herald, and sold it to the employees and regular passengers on his line. Usually he would set the type before the train started, and print it in the spare moments of his trip. Sometimes one of the station-masters on the run, who was also a telegraph operator, would get a piece of important news, write it down, and hand the paper to Edison as the train stopped. Then the boy would go to his shop in the caboose, set up the item, print it, and sell it, beating the daily newspapers that might be awaiting the passengers at the end of the ride.

The new invention of the telegraph, and the great possibilities of its use, early caught his attention. About the time the Civil War began the newsboy adopted a new idea in his business. He had always found it difficult to know how many newspapers to carry on each trip. If he had too large a stock some would be left on his hands, if he carried too few he would be sold out early and lose a good profit. He made a friend of one of the compositors of the Detroit Free Press, and got him to show him the proofs of the paper. That gave him some idea of the news of the day, and he could judge how many papers he would probably need. One day the proof-slip told him that there had been a terrific battle at Pittsburg Landing, or Shiloh, and that sixty thousand men had been killed and wounded. He knew that this would sell the paper. All he needed was to let people get an inkling of what the news was.

Edison dashed to the telegraph-operator and asked if he would wire a message to each of the large stations on the railroad line requesting the station-masters to chalk up a notice on their train bulletin-board, giving the fact that there had been a great battle, and that papers telling about it would reach the station at such an hour. In return he offered the operator newspaper service for six months free. The bargain was made, and the boy hurried to the newspaper office.

He did not have enough money to buy as many papers as he wanted. He asked the superintendent to let him have one thousand copies of the Press on credit. The request was instantly refused. Thereupon he marched up the stairs to the office of the paper’s owner, and asked if he would give him fifteen hundred copies on trust. The owner looked at the boy for a moment, and then wrote out an order. “Take that down-stairs,” said he, “and you will get what you want.” As Edison said in telling the story afterward, “Then I felt happier than I have ever felt since.”

He took his fifteen hundred copies to his storehouse on the train. At the station where the first stop was made he usually sold two papers. That day as they ran in to the platform it looked as if a riot had occurred. All the town was clamoring for papers. He sold a couple of hundred at five cents each. Another crowd met him at the next stop, and he raised his price to ten cents a copy. The same thing happened at each place where they stopped. When he reached Port Huron he put what was left of his stock in a wagon, and drove through the main streets. He sold his papers at a quarter of a dollar and more apiece. He went by a church, and called out the news of the battle. In ten seconds the minister and all his congregation were clamoring about the wagon, bidding against each other for copies of the precious issue. He had made a small fortune for a boy, and felt that he owed it largely to his use of the telegraph. Quick-witted he was, beyond a doubt, of an inventive turn, but a shrewd business man on top of all.

He wanted to be a telegraph-operator. Electricity fascinated him, and he could watch the machines and listen to the music of their clicking by the hour. He set up a line of his own in his father’s basement at Port Huron, making his batteries of bottles, old stovepipe wire, nails and zinc that he could pick up for a trifle. He studied the subject in his shop in the corner of the baggage-car, during the scant moments when he was neither printer nor newsboy. Once a bottle of phosphorus upset and started a fire. The boy was thrashed and his bottles and wires thrown out. But he was too doggedly persistent to mind any mishap. He saved the small son of the station-master at Port Clements from being run down by a train, and in return the father offered to teach him telegraphy. So little by little he learned his chosen work.

He obtained a position as night operator at Port Huron. That kept him busy at night, but he refused to sleep during the daytime as other night operators did, and used that time to work on his own schemes. To catch some sleep he kept a loud alarm-clock at his office, and set it so that he would be waked when trains were due and he was needed. But sometimes trains were off schedule, and again and again he would oversleep. At last the train despatcher ordered Edison to signal him the letter “A” in the Morse alphabet every half hour. The boy willingly agreed. A few nights later he brought an invention of his own to the office, and connected it by wires with the clock and the telegraph. Then he watched it work. Exactly on the half hour a little lever fell, sending an excellent copy of the Morse “A” to the key of the telegraph. Another lever closed the circuit. He kept his eyes on this instrument of his making until he had seen it act faultlessly again at the next half hour. Then he went to sleep. Night after night the signal was sent without a mistake, and the despatcher began to regain some of the confidence he had lost in the young operator. Then one night the despatcher chanced to be at the next station to Edison’s, and it occurred to him to call the latter up and have a chat with him. He signaled for fifteen minutes, and received no answer. Then he jumped on a hand-car and rode to Edison’s station. Looking through the window he saw the youth sound asleep. His eyes took in the strange instrument upon the table. It was near the half hour, and as the man watched he saw one lever of the instrument throw open the key and the other send the signal over the wire. The operator was still sleeping soundly. The despatcher recognized the young man’s ingenuity, but he also realized that he had been fooled, and so he woke Edison none too gently, and told him that his services were no longer in demand on that road.

Ingenuity, mechanical short-cuts, new devices for doing old work, were what beset his mind. He was not interested in doing the simple routine service of a telegrapher, he wanted to see what improvements on it he could make. Often this keenness for new ideas led him into trouble with his employers; occasionally it was of real service. At one time an ice-jam had broken the cable-line between Port Huron, in Michigan, and Sarnia, over the Canadian line. The river there was a mile and a half wide. The officers were wondering how they could get their messages across when they saw Edison jump upon a locomotive standing in the train-yard. He seized the valve that controlled the whistle. He opened and closed it so that the locomotive’s whistles resembled the dots and dashes of the telegraph code. He called Sarnia again and again. “Do you hear this? Do you get this?” he sent by the whistle. Four and five times he sent the message, and finally the whistle of a locomotive across the river answered him. In that way communication was again established.

A little later, when Edison was employed as operator in the railroad office at Indianapolis, he practiced receiving newspaper reports in his spare hours at night. He and a friend named Parmley would take the place of the regular man, who was glad to have them do it. “I would sit down,” said Edison, “for ten minutes, and ‘take’ as much as I could from the instrument, carrying the rest in my head. Then while I wrote out, Parmley would serve his turn at ‘taking,’ and so on. This worked well until they put a new man on at the Cincinnati end. He was one of the quickest despatchers in the business, and we soon found it was hopeless for us to try to keep up with him. Then it was that I worked out my first invention, and necessity was certainly the mother of it.

“I got two old Morse registers and arranged them in such a way that by running a strip of paper through them the dots and dashes were recorded on it by the first instrument as fast as they were delivered from the Cincinnati end, and were transmitted to us through the other instrument at any desired rate of speed. They would come in on one instrument at the rate of forty words a minute, and would be ground out of our instrument at the rate of twenty-five. Then weren’t we proud! Our copy used to be so clean and beautiful that we hung it up on exhibition; and our manager used to come and gaze at it silently with a puzzled expression. He could not understand it, neither could any of the other operators; for we used to hide my impromptu automatic recorder when our toil was over. But the crash came when there was a big night’s work—a presidential vote, I think it was—and copy kept pouring in at the top rate of speed until we fell an hour and a half or two hours behind. The newspapers sent in frantic complaints, an investigation was made, and our little scheme was discovered. We couldn’t use it any more.”

His fortunes rose and fell, for, although he was now becoming a very expert operator, taking messages with greater and greater speed, he would continue to stray into new fields of experiment. When he started to work in the Western Union office in Memphis, which was soon after the end of the Civil War, he found that all messages that were sent from New Orleans to New York had to be received at Memphis, sent on from there to Louisville, taken again, and so forwarded by half a dozen relays to New York. Many errors might creep in by such a system. To cure this he devised an automatic repeater, which could be attached to the line at Memphis, and would of its own accord send the message on. In this way the signals could go directly from New Orleans to New York. The device worked, and was highly praised in the local newspapers. But it happened that the manager of the office had a relative who was just completing a similar instrument, and Edison had forestalled him. Consequently he found himself discharged. He got a railroad pass as far as Decatur, and walked a hundred and fifty miles from there to Nashville. So by alternate riding and walking he finally reached Louisville. A little later he was offered a place in the Boston office.

He had plenty of nerve, and was not at all put out at the amusement of the other men when he walked into the Boston office, clad in an old and shapeless linen duster. “Here I am,” he announced to the superintendent. “And who are you?” he was asked. “Tom Edison. I was told to report here.”

The superintendent sent him to the operating-room. Shortly after a New York telegrapher, famed for his speed, called up. Every one else was busy, and Edison was told to take his message. He sat down, and for four and a half hours wrote the messages, numbering the pages and throwing them on the floor for the office boy to gather up. As time went on the messages came with such lightning speed that the whole force gathered about to see the new man work. They had never seen such quickness. At the end of the last message came the words, “Who the devil are you?” “Tom Edison,” the operator ticked back. “You are the first man in the country,” wired the man in New York, “that could ever take me at my fastest, and the only one who could ever sit at the other end of my wire for more than two hours and a half. I’m proud to know you.”

This story may be legendary, but it is known to be a fact that Edison was at this time the fastest operator in the employ of the Western Union, and that he could take the messages sent him with a careless ease which amounted almost to indifference. He had also cultivated an unusually clear handwriting, which was of great help in writing out the messages.

As soon as he was settled at the Boston office he opened a small workshop, where he might try to complete some of the many devices he had in mind. He took out his first patent in 1868, when he was twenty-one years old, and it was obtained for what he called an electrical vote recorder. This was intended for use in Congress and the State Legislatures, and to take the place of the slow process of calling the roll on any vote. It was worked somewhat on the plan of the hotel indicator. The voter, sitting at his desk, would press one button if he wanted to vote “aye,” and another if he wanted to vote “no.” His vote was then recorded on a dial by the Speaker’s desk, and as soon as each member had pressed one or the other button the total votes on each side could be known. The machine worked perfectly, and Edison took it to Washington in high hopes of having it adopted by Congress. The chairman to whom he was referred examined it carefully. Then he said, “Young man, it works all right and couldn’t be better. With an instrument like that it would be difficult to monkey with the vote if you wanted to. But it won’t do. In fact, it’s the last thing on earth that we want here. Filibustering and delay in the counting of the votes are often the only means we have of defeating bad legislation. So, though I admire your genius and the spirit which prompted you to invent so excellent a machine, we shan’t require it here. Take the thing away.”

“Of course I was very sorry,” said Edison, in speaking of this interview later, “for I had banked on that machine bringing me in money. But it was a lesson to me. There and then I made a vow that I would never invent anything which was not wanted, or which was not necessary to the community at large. And so far I believe I have kept that vow.”

It was very evident there was a keen-witted man at work in the Boston office. The operators there had been much annoyed by an army of cockroaches that used to march across the table where they put their lunches and make a raid on the sandwiches and pies. One day Edison appeared with some tin-foil and four or five yards of fine wire. He unrolled the tin-foil, and, cutting two narrow strips from the long sheet, he stretched them around the table, keeping them near together, but not touching, and fastening them with small tacks. Then he connected the ribbons of foil with two batteries.

The leaders of the cockroach army arrived. The advance guard got his fore-creepers over the first ribbon safely, but as soon as they touched the parallel ribbon over he fell. In a very short time the invading army had met its Waterloo, and the lunches were safe from any further attack.

At another time the tin dipper that hung by the tank of drinking-water temporarily disappeared. When it was returned Edison put up a sign, reading, “Please return this dipper.” He also connected the nail on which the dipper hung with a wire attached to an electric battery. After that the dipper stayed in its place under penalty of a wrenched arm for moving it without first disconnecting the battery.

Edison had now determined to become an inventor, and as soon as he was able gave up his position in the Boston telegraph office, where his routine work took too much of his time, and went to New York to look for other opportunities. It happened that one day soon after his arrival he was walking through Wall Street and was attracted to the office of the Law Gold Indicator. The indicators or stock-tickers of this company were a new device, and were distributed through most of the large brokerage houses of the city. On the morning when Edison casually looked in, the machines had stopped work, no one could find out what was the matter, and the brokers were much disturbed. Edison watched Mr. Law and his workmen searching for the trouble. Then he said that he thought he could fix the machines. Mr. Law told him to try. He removed a loose contact spring that had fallen between the wheels, and immediately the tickers began to work again. The other workmen looked foolish, and Mr. Law asked the newcomer to step into his private office. At the end of the interview the owner had offered Edison the position of manager at a salary of three hundred dollars a month, and Edison had accepted.

He determined to improve this stock-indicator, and set to work at once. Soon he had evolved a number of important additions. The president of the company sent for him and asked how much he would take for these improvements. The inventor said that he would leave that to the president. Forty thousand dollars was named and accepted. Edison opened a bank account, and gave more time to working in his own laboratory. He had got well started up the rungs of the ladder he planned to climb.

His work lay along the lines of the telegraph, and he was anxious to win the support of the Western Union for his new ideas. His chance came when there was a breakdown of the lines between New York and Albany. He went to the Western Union president, who had already heard of him, and said, “If I locate this trouble within two or three hours, will you take up my inventions and give them honest consideration?” The president answered, “I’ll consider your inventions if you get us out of this fix within two days.” Edison rushed forthwith to the main office. There he called up Pittsburg and asked for their best operator. When he had him he told him to call up the best man at Albany, and get him to telegraph down the line to New York as far as he could, and report back to him. Inside of an hour he received the message, “I can telegraph all right down to within two miles of Poughkeepsie, and there is trouble with the wire there.” Edison went back to the president and told him that if he would send a repair train to Poughkeepsie they would find a break two miles the other side of the city and could have it repaired that afternoon. They followed his directions, and communication was restored before night. After that the Western Union officials gave the most careful consideration to every new invention that Edison brought them.

As soon as he had money in bank Edison carried out a plan he had long had in mind. He gave up his workshop in New York and opened a factory and experimenting shop in Newark, New Jersey, where he would have plenty of room for himself and his assistants. He began by manufacturing his improved “stock-tickers,” and he met with very considerable success. But he felt that manufacturing was not his forte. He said of this venture later, “I was a poor manufacturer, because I could not let well enough alone. My first impulse upon taking any apparatus into my hand, from an egg-beater to an electric motor, is to seek a way of improving it. Therefore, as soon as I have finished a machine I am anxious to take it apart again in order to make an experiment. That is a costly mania for a manufacturer.”

In his Newark shop Edison now turned his attention to improvements on the telegraph. His first important invention was the duplex, by which two messages could be sent over the same wire in opposite directions at the same time without any confusion or obstruction to each other. This doubled the capacity of the single wire. Later he decided to carry this system farther, and perfected the quadruplex device. By this two messages could be sent simultaneously in each direction, and two sending and two receiving operators were employed at each end of a single wire. The principle involved was that of working with two electric currents that differ from each other in strength or nature, and which only affect receiving instruments specially adapted to take such currents, and no others. This invention changed a hundred thousand miles of wire into four hundred thousand, and saved the Western Union untold millions of dollars which would otherwise have had to be expended for new wires and repairs to the old ones.

Along somewhat similar lines Edison perfected an automatic telegraph, an harmonic multiplex telegraph, and an autographic telegraph. The harmonic multiplex used tuning-forks to separate the several different messages sent at the same time, and the autographic telegraph allowed of the transmission of an exact reproduction of a message written by the sender in one place and received in another. And in addition to all these leading inventions he was continually improving on the main system, and his improvements were rapidly bought and taken over by the Western Union Company.

In almost as many diverse ways Edison improved upon the telephone. He had left his factory in Newark in charge of a capable superintendent, and moved his own laboratories to Menlo Park, a quiet place about twenty-five miles from Newark. His striking discoveries soon earned for him the nickname of “The Wizard of Menlo Park.” Here he experimented with the new apparatus known as the telephone. He said of his own connection with it, “When I struck the telephone business the Bell people had no transmitter, but were talking into the magneto receiver. You never heard such a noise and buzzing as there was in that old machine! I went to work and monkeyed around, and finally struck the notion of the lampblack button. The Western Union Telegraph Company thought this was a first-rate scheme, and bought the thing out, but afterward they consolidated, and I quit the telephone business.” As a matter of fact Edison has done a great deal of other work besides inventing his carbon transmitter in the telephone field, and the Patent Office is well stocked with applications he has sent them for receivers and transmitters of different designs.

Edison has himself told of the main incidents in his perfection of the electric light. In the Electrical Review he said, “In 1878 I went down to see Professor Barker, at Philadelphia, and he showed me an arc lamp—the first I had seen. Then a little later I saw another—I think it was one of Brush’s make—and the whole outfit, engine, dynamo, and one or two lamps, was traveling around the country with a circus. At that time Wallace and Moses G. Farmer had succeeded in getting ten or fifteen lamps to burn together in a series, which was considered a very wonderful thing. It happened that at the time I was more or less at leisure, because I had just finished working on the carbon-button telephone, and this electric-light idea took possession of me. It was easy to see what the thing needed: it wanted to be subdivided. The light was too bright and too big. What we wished for was little lights, and a distribution of them to people’s houses in a manner similar to gas. Grovernor P. Lowry thought that perhaps I could succeed in solving the problem, and he raised a little money and formed the Edison Electric Light Company. The way we worked was that I got a certain sum of money a week and employed a certain number of men, and we went ahead to see what we could do.

“We soon saw that the subdivision never could be accomplished unless each light was independent of every other. Now it was plain enough that they could not burn in series. Hence they must burn in multiple arc. It was with this conviction that I started. I was fired with the idea of the incandescent lamp as opposed to the arc lamp, so I went to work and got some very fine platinum wire drawn. Experiment with this, however, resulted in failure, and then we tried mixing in with the platinum about ten per cent. of iridium, but we could not force that high enough without melting it. After that came a lot of experimenting—covering the wire with oxide of cerium and a number of other things.

“Then I got a great idea. I took a cylinder of zirconia and wound about a hundred feet of the fine platinum wire on it coated with magnesia from the syrupy acetate. What I was after was getting a high-resistance lamp, and I made one that way that worked up to forty ohms. But the oxide developed the phenomena now familiar to electricians, and the lamp short-circuited itself. After that we went fishing around and trying all sorts of shapes and things to make a filament that would stand. We tried silicon and boron, and a lot of things that I have forgotten now. The funny part of it was that I never thought in those days that a carbon filament would answer, because a fine hair of carbon was so sensitive to oxidation. Finally, I thought I would try it because we had got very high vacua and good conditions for it.

“Well, we sent out and bought some cotton thread, carbonized it, and made the first filament. We had already managed to get pretty high vacua, and we thought, maybe, the filament would be stable. We built the lamp and turned on the current. It lit up, and in the first few breathless minutes we measured its resistance quickly and found it was 275 ohms—all we wanted. Then we sat down and looked at that lamp. We wanted to see how long it would burn. The problem was solved—if the filament would last. The day was—let me see—October 21, 1879. We sat and looked, and the lamp continued to burn, and the longer it burned the more fascinated we were. None of us could go to bed, and there was no sleep for any of us for forty hours. We sat and just watched it with anxiety growing into elation. It lasted about forty-five hours, and then I said, If it will burn that number of hours now, I know I can make it burn a hundred.’ We saw that carbon was what we wanted, and the next question was what kind of carbon. I began to try various things, and finally I carbonized a strip of bamboo from a Japanese fan, and saw that I was on the right track. But we had a rare hunt finding the real thing. I sent a schoolmaster to Sumatra and another fellow up the Amazon, while William H. Moore, one of my associates, went to Japan and got what we wanted there. We made a contract with an old Jap to supply us with the proper fibre, and that man went to work and cultivated and cross-fertilized bamboo until he got exactly the quality we required.”

This is the inventor’s own statement, but it gives a very meagre notion of the many months’ experimenting in his workshop while he hunted for a suitable filament for his electric light.

As he said, after he had first seen the Brush light, and studied it, he decided that the main problem was one of distribution, and thereupon considered whether he should use the incandescent or the voltaic arc in the system he was planning. At last he decided in favor of the incandescent light.

Then began the long months of testing platinum wire. He wanted to find some way of preventing this hardest of all metals from melting when the full force of the electric current was turned into it. He worked out several devices to keep the platinum from fusing, an automatic lever to regulate the electric current when the platinum was near the melting-point, and a diaphragm with the same object; but all of them had to be discarded. Although he was still searching for the right clue he seems to have had no doubt of his final success. He said at this time, “There is no difficulty about dividing up the current and using small quantities at different points. The trouble is in finding a candle that will give a pleasant light, not too intense, which can be turned off and on as easily as gas. Such a candle cannot be made from carbon points, which waste away, and must be regulated constantly while they do last. Some composition must be discovered which will be luminous when charged with electricity and that will not wear away. Platinum wire gives a good light when a certain quantity of electricity is passed through it. If the current is made too strong, however, the wire will melt. I want to get something better.”

It was generally known that Edison was working along this line. An English paper, commenting on the matter, said, “The weak point of the lamp is this, that in order to be luminous, platinum must be heated almost to the point of melting. With a slight increase in the current, the lamp melts in the twinkling of an eye, and in practice the regulator is found to short-circuit the current too late to prevent the damage. It is this difficulty which must be overcome. Can it be done?”

After long study Edison concluded that pure platinum was not suited to successful electric lighting. Then he incorporated with it another material of a non-conducting nature, with the result that when the electric current was turned on one material became incandescent and the other luminous. This gave a clear, but not a permanent, light. He tried many different combinations, and experimented month after month, but none of his trials produced the result he wanted, and at last he concluded that he was on the wrong track, and that neither platinum nor any other metal would give the right light.

There is something very dramatic about his real discovery. He was sitting in his laboratory one evening, when his right hand happened to touch a small pile of lampblack and tar that his assistants had been using in working on a telephone transmitter. He picked up a little of it, and began to roll it between his finger and thumb. He was thinking of other things, and he rolled the mixture absent-mindedly for some time, until he had formed a thin thread that looked something like a piece of wire. Glancing at it, he fell to wondering how it would serve as a filament for his light. It was carbon, and might be able to stand a stronger current than platinum. He rolled some more of the mixture, and decided to try it.

His experiments had already resulted in the production of an almost absolute vacuum, only one-millionth part of an atmosphere being left in the tube. Such a vacuum had never been obtained before. With his assistant, Charles Bachelor, he put a thread of the lampblack and tar in a bulb, exhausted the air, and turned on the current. There was an intense glow of light; but it did not last, the carbon soon burned out. Therefore he started to study the reason why the carbon had failed to withstand the electric current. His conclusion was that it was impossible to get the air out of the lampblack. Besides that the thread became so brittle that the slightest shock to the lamp broke it. But he felt certain now that a carbon filament, made of something other than tar and lampblack, was what he wanted.

He next sent a boy to buy a reel of cotton, and told his assistants he was going to see what a carbonized thread would do. They looked doubtful, but began the experiment. A short piece of the thread was bent in the form of a hairpin, laid in a nickel mould and securely clamped, and then put in a muffle furnace, where it was kept for five hours. Then it was taken out and allowed to cool. The mould was opened and the carbonized thread removed. It instantly broke. Another thread was put through the same process. As soon as it was taken from the mould it broke. Then a battle began that lasted for two days and two nights, the object of which was to get a carbonized thread that would not break. Edison wanted that thread because it contained no air, and might stand a greater current than the lampblack. Finally they took from the mould an unbroken thread, but as they tried to fasten it to the conducting wire it broke into pieces. Only on the night of the third day of their work, in all which time they had taken no rest, did they get a thread safely into the lamp, exhaust the air, and turn on the current. A clear, soft light resulted, and they knew that they had solved the problem of the incandescent light.

Edison and Bachelor watched that light for hours. They had turned on a small current at the start, to test the strength of the filament, but as it stood it, they turned on a greater and greater current until the thread was bearing a heat that would have instantly melted the platinum wire. The cotton thread glowed for forty-five hours, and then suddenly went out. The two watchers ended their long vigil, exhausted, but very happy. They knew that they had found the light that was to be the main illumination for the world.

But Edison realized that he had not yet found the ideal filament. The cotton thread had only lasted forty-five hours, and he wanted one that would burn for a hundred hours or longer. He wanted a more homogeneous material than thread, and he began to try carbonizing everything he could lay his hands on, straw, paper, cardboard, splinters of wood. He found that the cardboard stood the current better than the cotton thread, but even that did not burn long enough. Then he happened upon a bamboo fan, tore off the rim, and tried that. It made a filament that gave better results than any of the others.

Now he began his exhaustive study of bamboo. He learned that there were more than twelve hundred known varieties of bamboo. He wanted to find the most homogeneous variety. He sent out a number of men to hunt this bamboo, and it is said that the search cost nearly $100,000. Six thousand specimens of bamboo were carbonized, and he found three kinds of bamboo and one of cane that gave almost the result he wanted. All of these grew in a region near the Amazon, and were hard to get on account of malarial conditions. But at last he discovered the bamboo species that suited him, and he was ready to give his new light to the world.

The world was waiting for it. Scientists and the press reported his invention everywhere. He hung a row of lamps from the trees at Menlo Park, and the thousands who came to see them wondered when they found they could burn day and night for longer than a week. The lamps were small and finely made, they could be lighted or extinguished by simply pressing a button, and the cost of making them was slight. The last doubters surrendered, and admitted that Edison had given the world a new light, and one which was not simply a scientific marvel, but was eminently practical and useful.

But Edison is never satisfied with what he has done in any line; he must try to increase the service each invention gives. Therefore he now conceived the idea of having a central station from which every one might obtain electric light as they had formerly obtained gas. There were gigantic difficulties in the way of such an undertaking. Hardly any one outside of Edison’s own laboratory knew anything about electric lighting, and there were only a few of them who could be trusted to put a carbon filament in an exhausted globe.

He went about this new development in the most methodical way. He got an insurance map of New York City, and studied the business section from Wall to Canal Streets and from Broadway over to the East River. He knew where every elevator shaft and boiler and fire-wall was, and also how much gas each resident used and what he paid for it. This last he learned by hiring men to walk through the district at two o’clock in the afternoon and note how many gas lights were burning, then to make the rounds again at three, and again at four, and so on into the hours of the next morning.

With the field carefully examined he formed the New York Edison Illuminating Company, and had his assistants take charge of factories for making lamps, dynamos, sockets, and the other parts necessary for his lights. It was very difficult to get the land he wanted for his central station, but he finally bought two old buildings on Pearl Street for $150,000. He had little room space and he wanted to get a big output of electricity. So he decided to get a high-speed engine. They were practically unknown then, and when he went to an engine builder and said that he wanted a 150 horse-power engine that would run 700 revolutions per minute he was told it was impossible. But he found a man to build one for him, and set it up in the shop at Menlo Park. The shop was built on a shale hill, and when the engine was started the whole hill shook with the high speed revolutions. After some experimenting and changing they got the power that Edison wanted, and he ordered six more engines like the first.

In the meantime workmen had been busy digging ditches and laying mains through the district that Edison intended to light. The engines were set up in the central station and tried out. Then the troubles began. The engines would not run evenly, one would stop and another go dashing on at a tremendous speed. Edison tried a dozen different plans before he brought anything like order out of that engine chaos. Finally he had some engines built to run at 350 revolutions and give 175 horse-power, and these proved what was required. September 4, 1882, he turned the current on to the mains for the needed light service, and it stayed on with only one short stoppage for eight years.

In this way Edison invented the electric light and evolved the central station that should provide the current wherever it was needed. At the same time he had worked out countless adjuncts to it, the use of the fine copper thread to serve as a fuse wire and prevent short-circuiting, the meter, consisting of a small glass cell, containing a solution in which two plates of zinc are placed, and which shows how much current is supplied, the weighing voltameter, and other instruments for estimating the current, and improvements on the motors and engines. There was no field remotely connected with electric lighting that he did not enter. Yet as soon as the invention was actually before the world business competitors sprang up on every hand. There was more litigation over this than over any other of Edison’s inventions. “I fought for the lamp for fourteen years,” he said, “and when I finally won my rights there were but three years of the allotted seventeen left for my patent to live. Now it has become the property of anybody and everybody.”

Edison had always wanted a model laboratory, one that should be fitted with the most perfect instruments obtainable, and supplied with all the materials he could possibly require in any of his extraordinary experiments. In 1886 he bought a house in Llewellyn Park, New Jersey, and near the house ten acres of land, on which he built the laboratory of his dreams. Here he had a large force of skilled workmen constantly engaged in developing his ideas, and the expenses were paid by the many commercial companies in which he was interested, and which profited by the improvements he was continually making in their machinery.

Many volumes might be written to tell of the “Wizard’s” achievements. There has been no inventor who has covered such a field, and each step he takes opens new and fascinating vistas to his ever-inquiring eyes. Electricity is always his main study, and electricity he expects in time will revolutionize modern life by making heat, power, and light practically as cheap as air. But other subjects have concerned him almost as much. He ranges from new processes for making guns to the supplying of ready-made houses built of cement. Everything interests him, every object tempts him to try his hand at improving on it.

The phonograph is his achievement, and the practical development of the kinetoscope. He has built electric locomotives and run them, he has made many discoveries in regard to platinum. His better known patents include developments of the electric lamp, the telephone, storage-batteries, ore-milling machinery, typewriters, electric pens, vocal engines, addressing machines, cast-iron furniture, wire-drawing, methods of preserving fruit, moving-picture machines, compressed-air machines, and the manufacture of plate glass. He took out a patent covering wireless telegraphy in 1891, but other matters were then absorbing his attention, and he was quite willing to yield that field to the brilliant Italian, Marconi. He feels no jealousy for other inventors. He knows how vast the field is, and how many paths constantly beckon him.

It is doubtless true that the great inventors are born and not made, but many of them seem, nevertheless, to have drifted into the work that gave them fame, or to have hit by chance on their compelling idea. It was not so with Edison. He was beyond any doubt born an inventor. With him to see was to ask the question why, and to ask that question was to start his thoughts on the train that was to bring him to the answer.