190 SCIENTIFIC RECREATIONS. 



thing more to say respecting the mysteries of the Telephone and its later 

 developments. At present we are only concerned with it as a sound 

 conveyer, and it answers its purpose admirably, although somewhat liable to 

 attract other sounds or vibrations from neighbouring wires. 



The PHONOGRAPH, a mechanical invention of Mr. Edison, does not 

 make use of electricity, although the vibratory motion of the diaphragm is 

 utilized. It, in a simple form, consists of a diaphragm so arranged as to 

 operate upon a small stylus placed just opposite and below the centre, and 

 a brass cylinder, six or eight inches long, by three or four in diameter, 

 mounted upon a horizontal axis, extending each way beyond its ends for a 

 distance about its own length. 



U A spiral groove is cut in the circumference of the cylinder, from one 

 end to the other, each spiral of the groove being separated from its neigh- 

 bour by about one-tenth of an inch. The shaft or axis is also cut by a screw 



Fig. 194. Mode of using the Telephone. 



thread corresponding to the spiral groove of the cylinder, and works in 

 screw bearings ; consequently when the cylinder is caused to revolve, by 

 means of a crank that is fitted to the axis for this purpose, it receives a 

 forward or backward movement of about one-tenth of an inch for every turn 

 of the same, the direction, of course, depending upon the way the crank 

 is turned. The diaphragm is firmly supported by an upright casting 

 capable of adjustment, and so arranged that it may be removed altogether 

 when necessary. When in use, however, it is clamped in a fixed position 

 above or in front of the cylinder, thus bringing the stylus always opposite 

 the groove as the cylinder is turned. A small, flat spring attached to the 

 casting extends underneath the diaphragm as far as its centre and carries 

 the stylus, and between the diaphragm and spring a small piece of india- 

 rubber is placed to modify the action, it having been found that better 

 results are obtained by this means than when the stylus is rigidly attached 

 to the diaphragm itselt. 



