At nearly the same time Miss Mabel Hubbard came to him to be taught his system of speech. He became engaged to her, and some years later they were married. His future wife’s father was a well-known Boston lawyer, Gardiner G. Hubbard. It is related that one evening as Bell sat at the piano in Mr. Hubbard’s home in Cambridge, he said, “Do you know that if I sing the note G close to the strings of the piano, the G-string will answer me?” “What of it?” asked Mr. Hubbard. “Why, it means that some day we ought to have a musical telegraph, that will send as many messages simultaneously over one wire as there are notes on the piano.” Bell knew the field of his work in a general way, but he had not yet decided which path to choose of several that looked as if they might lead across it. His far-distant goal was to construct a machine that would carry, not the dots and dashes of the telegraph, but the complex vibrations of the human voice. This would be much more difficult to attain than a musical telegraph, and for some time he wavered between the two ideas. His work with his deaf and dumb pupils was all in the line of making sound vibrations visible to the eye. He knew that with what was called the phonautograph he could get tracings of such sound vibrations upon blackened paper by means of a pencil or marker attached to a vibrating cord or membrane, and furthermore that he could obtain tracings of certain vowel sound vibrations upon smoked glass. He studied the effect of vibrations upon the bones of the ear, and this led him to experiment with vibrating a thin piece of iron before an electro-magnet. His study of the effect of vibrations on the human eardrum showed Bell what path he should follow. Sound waves striking the delicate ear-drum could send thrills through the heavier bones inside the ear. He thought that if he could construct two iron discs, which should be similar to the ear-drums, and connect them by an electrified wire, he might be able to make the disc at one end vibrate with sound waves, send those vibrations through the wire to the other disc, and have that give out the vibrations again in the form of sounds. That now became his working idea, and it was the principle on which the telephone was ultimately to be built. But Bell had been giving so much time and attention to this absorbing project that his teaching had suffered. His “School of Vocal Physiology” had had to be abandoned, and he found that his only pupils were Miss Hubbard and small George Sanders. Both Mr. Sanders and Mr. Hubbard, who had been helping him with the cost of his experiments, refused to do so any longer unless he would devote himself to working out his musical telegraph, in which both had a great deal of faith as a successful business proposition.