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.