During the past year I have had many opportunities, in connection with a research on the phonograph, of observing the efficacy of Mr Graham's method of electrically producing sound, and as it is not generally known, a short explanation may be useful.

Two or more cells are connected to a mass of granular carbon whose resistance can be varied by vibration, and the circuit is then completed through the coils of an electro-magnet. In front of the electro-magnet is a diaphragm sensitive to the variations of current flowing through the electro-magnet. This diaphragm is so placed relatively to the circuit of variable resistance, that any vibration imparted to it is transmitted through a column of air to the circuit of the variable resistance or its diaphragm. The granular carbon, similar to that in telephonic transmitters, is contained in a box or chamber closed at one end by a diaphragm of carbon, with which the granular carbon is in electrical contact. The carbon resistance box is so placed that its diaphragm is acted on by the vibrations set up by the diaphragm of the electro-magnet. To effect this, a flexible tube passes from the front of the diaphragm of the transmitter to the front of the diaphragm of the electro-magnet. Thus, when the various parts of the apparatus are connected, as seen in the figure, and when the circuit is completed by closing a key, the vibrations set up in the telephone diaphragm are caused to act upon the circuit of variable resistance, which, in turn, again acts upon the telephone or receiver diaphragm. A continuous musical sound is then emitted.