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THOMAS A. EDISON 167 atora are required at each end of the wire. This device was worth millions of dollars to the Western Union, be- cause it made a mile of wire do the work of four miles. Eventually the same idea was developed into Sextuplex trans- mission. Not less brilliant was the invention of the automatic tele- graph, which required the preparation of the message in ad- vance, accomplished by the use of perforated paper tape with Morse telegraph characters, the tapes being subsequently run through a transmitter. This invention became possible only after the discovery of a solution which would give a chemically prepared pa])er, upon which the characters could be recorded at a great speed. Mr. Edison worked hard to perfect this paper and after six weeks of incessant labor, during which he ate at his desk and slept in his chair, he was finally able, after having made two thousand experiments, to produce a solution which would enable him to record over two thousand words a minute on a wire two hundred and fifty miles long. Event- ually he was able to obtain a speed of thirty-one hundred words a minute. It was while at Newark that he also invented the harmonic multiplex telegraph, a system of employing tuning forks act- uated by electro-magnets so that each reed serves as a key to send messages over the line, the tuning fork at the other end vibrating at the same frequency and thus selecting as much of the current as belongs to it. As many as sixteen messages may be sent at one time by means of this harmonic multiplex system. The autographic telegraph, also an Edison invention, writes at the other end of the line the same message which is sent off by means of a pencil writing on specially prepared paper. It was not only in telegraphy that Mr. Edison made such revolutionary inventions, but also in the perfection of the telephone. Many scientists were becoming interested in try- ing to solve the problem of how to employ electricity as a means of transmitting speech for great distances. The most famous of these inventors was Alexander Graham Bell, of Salem, Massachusetts. Strange to say, at almost exactly the