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The Telephone 143 after a little reflection he forced the thought into the background, partly because his experiments to this end proved such disconcerting failures. It was ultimately submerged by another idea—the trans- mission of a number of messages at the same time in the Morse telegraphic code over a single wire. He called it the “ Harmonic Telegraph,” and he depended for his success upon the law of sympathetic vibrations. An intermittent current of a given musi- cal pitch was produced by each transmitter, to which the receiver responded when its spring was tuned to that particular note. But the crux of this problem was that the sympathetic springs—that of the trans- mitter and the receiver respectively—had to be dead in tune to prevent any conflict in the tele- graphic signals. In the quest of this issue the cellar laboratory in the Sanders’ home became a maze of tuning-forks, electro-magnets, and electric batteries. But although the harmonic telegraph claimed the first and foremost attention of the young investigator, the idea of talking over the telegraph wire still lingered at the back of his brain. He kept it under restraint, thinking that perhaps, while working out the har- monic telegraph, some phenomena might be revealed which would lead to the realisation of the talking- wire problem. But the harmonic telegraph proved an exasperat- ing field for experiment. The greatest difficulty was to keep the springs in tune. He would sit in a room with a receiver pressed to his ear so as to be able to compare the note or pitch of its spring with that of the transmitter which was vibrating in the cellar