166 FAMOUS LIVING AMEEICANS any practical use. Soon after this he went to New York, ar- riving in that city without enough money to buy a breakfast. He applied for a job as a telegraph operator. While waiting for work he one day paid a visit to the office of a company which managed indicators, or tickers, distributed among sev- eral hundred brokerage offices. On that particular morning the machinery had broken down and there was much excitement because no one was able to locate the trouble. Every moment was precious because gold was dear. Mr. Edison was stand- ing by during the conmiotion and remarked that he thought he could put things right if permitted to do so. He was told to go ahead, whereupon he removed a loose contact spring which had fallen between the wheels and immediately the instrument did its work. As a result Mr. Edison was made manager of the service at a salary of three hundred dollars a month. He almost fainted from joy when he received the appointment. Dissatisfied with the working of the old instrument he set to work to improve it. Thus came about the invention of Edi- son's Universal Stock Indicator for which he was paid the sum of forty thousand dollars. At first he scarcely knew what to do with so much money, but finally decided to open up a factory in Newark, New Jersey, where he employed a number of assistants and soon made many surprising inventions. Among these was the Duplex telegraph which he sold to the Western Union Telegraph Company, who also made a contract with him by which they obtained an option on all his future improvements along telegraphic Unes. By means of the Duplex telegraph it was possible to send two messages in opposite directions over the same wire at the same time, without causing any confusion. This great inven- tion, which doubled the capacity of a single wire, was followed by that of the Quadruplex telegraph, invented in 1874, which made possible the transmission of two messages each way at the same time, according to the principle of working over the line with two currents so diflfering from each other in strength or nature that each of these currents affects only the par- ticular instrument adapted to respond to it. In order to operate this invention, two sending and two receiving oper
