Arrived in London, Edison set up his apparatus at the Telegraph Street headquarters, and sent his companion to Liverpool with the instruments for that end. The condition of the test was that he was to record at the rate of one thousand words a minute, five hundred words to be sent every half hour for six hours. Edison was given a wire and batteries to operate with, but a preliminary test soon showed that he was going to fail. Both wire and batteries were poor, and one of the men detailed by the authorities to watch the test remarked quietly, in a friendly way: "You are not going to have much show. They are going to give you an old Bridgewater Canal wire that is so poor we don't work it, and a lot of 'sand batteries' at Liverpool."[1]
The situation was rather depressing to the young American, but "I thanked him," says Edison, "and hoped to reciprocate somehow. I knew I was in a hole. I had been staying at a little hotel in Covent Garden called the Hummums, and got nothing but roast beef and flounders, and my imagination was getting into a coma. What I needed was pastry. That night I found a French pastry shop in High Holborn Street and filled up. My imagination got all right. Early in the morning I saw Gouraud, stated my case, and asked if he would stand for the purchase of a powerful battery to send to Liverpool. He said 'Yes.' I went immediately to Apps, on the Strand, and asked if he had a powerful battery. He said he hadn't; that all that he had was Tyndall's Royal Institution battery, which he supposed would not serve. I saw it—one hundred cells—and getting the price—one hundred guineas—hurried to Gouraud. He said 'Go ahead.' I telegraphed to the man in Liverpool. He came on, and got the battery to Liverpool, set up and ready just two hours before the test commenced. One of the principal things that made the system a success was that the line was put to earth at the sending end through a magnet, and the extra current from this passed to the line served to sharpen the recording waves. This new battery was strong enough to pass a powerful current through the magnet without materially diminishing the strength of the current." The test under these more favorable circumstances was a success. "The record was as perfect as copper plate, and not a single remark was made in the 'time lost' column." Edison was now asked if he thought he could get a better speed through submarine cables with this system, and replied that he would like a chance to try it. For this purpose twenty-two hundred miles of cable stored under water in tanks was placed at his disposal from 8 P.M. until 6 A.M. He says: "This just suited me, as I preferred night work. I got my apparatus down and set up, and then to get a preliminary idea of what the distortion of the signal would be I sent a single dot, which should have been recorded upon my automatic paper by a mark about one thirty-second of an inch long. Instead of that it was twenty-seven feet long. If I ever had any conceit, it vanished from my boots up! I worked on this cable more than two weeks, and the best I could do was two words per minute, which was only one-seventh of what the guaranteed speed of the cable should be when laid. What I did not know at the time was that a coiled cable, owing to induction, was infinitely worse than when laid out straight, and that my speed was as good as, if not better than, the regular system, but no one told me this."
After a short stay in England Edison returned to America. He states that the automatic was finally adopted in England and used for many years; indeed, it is still in use there. But they took whatever they needed from his system, and he "has never had a cent from them."
On arriving home he resumed arduous work on many of his inventions—chiefly those relating to duplex telegraphy. This subject had interested him at various times for four or five years previously, and he now returned to it with great vigor.
Many inventors had been working on multiple transmission, and at this period a system of sending two messages in opposite directions at the same time over one wire had been invented by Joseph Stearns, and had then lately come into use.
The subject of multiple transmission gave plenty of play for ingenuity and was one that had great fascination for Edison. He worked out many plans, and in April, 1873, two applications for patents. One of these covered an invention by which not only could two messages be sent in opposite directions over one wire at the same time, but, if desired, two separate messages could be sent simultaneously in the same direction over a single wire. The former method was called the "duplex," and the latter the "diplex."
Duplexing was accomplished by varying the strength of the current, and diplexing by also varying the direction of the current. In this invention there was the germ of the quadruplex, and now Edison redoubled his efforts toward completing the latter system, for, while duplexing doubled the capacity of a line, the quadruplex would increase it four times.
He was working also on other inventions, but the quadruplex claimed most of his attention. He says: "This problem was of the most difficult and complicated kind, and I bent all my energies toward its solution. It required a peculiar effort of the mind, such as the imagining of eight different things moving simultaneously on a mental plane without anything to demonstrate their efficiency."
It is, perhaps, hardly to be wondered at that, when notified he would have to pay twelve and one-half per cent, extra if his taxes in Newark were not at once paid, he actually forgot his own name when asked for it suddenly at the City Hall, and lost his place in the line!
He succeeded, however, in inventing a successful quadruplex system by a skilful combination of the duplex and diplex with other ingenious devices. The immense value of this invention may be realized when it is stated that it has been estimated to have saved from fifteen million to twenty million dollars in the cost of line construction in America. But Mr. Edison received only a small amount for it. We will let him tell the story in his own words: