‘This fact of the reproduction of sounds by a helix is universal. Every induction coil and every electro-magnet are capable of reproducing sound when the currents of the sender are of sufficient intensity.’ Signor Canestrelli writes as follows: ‘With the combination of a carbon telephone and one without diaphragm or magnet--that is, with only a simple coil--I was able to hear whistling through the coil, placed close to the ear. This coil was of very fine copper wire, and the currents were produced through an induction coil by two Bunsen elements. The contacts of the telephone were in carbon, and it was inserted in the primary circuit. ‘I fastened the coil to the middle of a tightly stretched membrane which served as the base of a short metal cylinder. When a magnet was placed near this part of the coil, the sounds were intensified, and when I fixed the magnet in this position, I could hear what was said. ‘I afterwards substituted for the magnet a second coil, fastened to a wooden bar, and on causing the induced currents to pass into both coils at once I was able to hear articulate speech, although not without difficulty. ‘Under these latter conditions I found it possible to construct a telephone without a magnet, but it required a strong current, and it was necessary to speak into the sender in a special manner, so as to produce strong and concentrated sounds.’ Another very interesting experiment by M. A. Bréguet shows that all the constituent parts of the telephone--the handle, the copper rims, and the case, as well as the diaphragm and the electro-magnet--can transmit sounds. M. Bréguet ascertained this fact by the use of string telephones, which he attached to different parts of the telephone on which the experiment was made. In this way he was not only able to establish a correspondence between the person who worked the electric telephone and the one who was listening through the string telephone, but he also made several string telephones act, which were attached to different parts of the electric telephone.