Page:Popular Science Monthly Volume 14.djvu/541

Rh time realize the full value of the invention, as his attention was mainly directed to the capacity of the apparatus for transmitting musical tones through an electric circuit.

In the winter of 1874 Mr. Gray observed a singular circumstance in connection with the reproduction of electrically transmitted vibrations through the medium of animal tissue. On going into the bath-room he found his nephew playing with a small induction coil—"taking shocks," as he expressed it, for the amusement of the smaller children. He had connected one end of the secondary coil to the zinc lining of the bath-tub, which was dry at that time. Holding the other end of the coil in his left hand he touched the lining of the tub with the right. In making contact, his hand would glide along the side for a short distance. At these times Mr. Gray noticed a sound proceeding from under his hand at the point of contact, which seemed to have the same pitch and quality as that of the vibrating electrotome, which was within hearing. Mr. Gray immediately took the electrode in his own hand, and, repeating the operation, to his astonishment found that, by rubbing hard and rapidly, he could make a much louder sound than the electrotome was making. He then changed the pitch of the vibration, increasing its rapidity, and found that the pitch of the sound under his hand was also changed, it still agreeing with that of the transmitted vibration. He then moistened his hand and continued the rubbing, but no sound was produced so long as his hand remained wet; but, as soon as the parts in contact became dry, the sound reappeared. So striking was the effect that, by hard rubbing with the dry hand, the noise could be distinctly heard throughout the house.

This experiment produced a profound impression upon his mind, and determined him at once to take the matter up in earnest and see what might be in it. He procured a violin, and, taking off the strings, substituted in their place a thin metal plate provided with a wire connection, so that he could attach it to one pole of the induction coil or battery, thus placing it in the same position, with reference to the body, that the bath-tub was in the original experiment. By rubbing the plate in the same manner as before described, the sound of the electrotome was reproduced, accompanied by the peculiar quality or timbre belonging to the violin. He noticed, however, that the characteristics of the initial vibrations were faithfully preserved, and all that was needed was to sift out such foreign vibrations as were excited in the receiver, owing to its peculiar construction; in which case there would remain the exact character of the transmitted vibrations.

In March, 1874, Mr. Gray undertook to secure letters patent for some of his conceptions, and with that purpose in view had models made, illustrating the idea of a series of transmitters, each tuned to a different pitch, showing a method of receiving musical or other sounds telegraphically, through the medium of animal tissue. In June, 1874, he filed another case, substituting for the animal-tissue receiver an