Note 1 — MUSICAL TELEPHONES.
Reading edition
Mr. Gray, in an article inserted in the Telegrapher of October 7, 1876, enters into full details of this mode of transmitting sounds by the tissues of the human body, and he gives the following as the conditions in which it must be placed to obtain a favourable result: 1. The electricity must be of a high tension, in order to have an effect perceptible to the ear.
2. The substance employed to touch the metallic plate must be soft, flexible, and a good conductor, up to the point of contact: it must then interpose a slight resistance, neither too great nor too small.
3. The disk and the hand, or any other tissue, must not only be in contact, but the contact must result from rubbing or gliding over the surface.
4. The parts in contact must be dry, so as to maintain the required degree of resistance.