Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Sound / by John Tyndall. Source: Wellcome Collection.

    235/496 (page 207)
    THE PHONOGRAPH. 3. screw is cut of the same pitch as that upon the cylinclei —viz. eight threads to the inch. The spindle turns in two brass bearings, one of which has an inside screw corresponding to the screw upon the spindle. A very thin sheet-iron diaphragm d d' (fig. 110) receives the operator's voice. It is secured by means of a brass flange over a shallow cir- pIG> no. cular recess cut in the wooden frame F. In the middle of the recess is a round hole opening into the mouthpiece M. A short piece of hard steel wire, ground to a blunt point and carefully polished, is fixed per- pendicularly to the iron diaphragm at its centre o. On the other side of the cylinder is the diaphragm p p', which reproduces the sound of the voice. It is made of vegetable parchment, and is stretched like a drum over the end of a piece of brass tube 1 inch long and 2f inches in diameter, fixed in the wooden frame H. The steel point t is attached to the end of a steel spring, its position coinciding with the centre of the circular opening in H. The light pine rod K, connecting the parchment and the spring, abuts at the end next to the spring against a small pad of vulcanised india-rubber, and at the other end carries a disc of thin sheet iron half an inch in diameter. The pressure of the spring is sufficient to render the diaphragm very slightly convex. The square frame f, carrying the thin iron diaphragm which receives the voice, is attached by hinges to a piece of wood, which is connected rigidly with 0, o again being con- nected by hinges B with x. By means of these hinges, and the screw s, tne point o may be made to approach the