[ The Edison Carbon Telephone and Hughes' Microphone.]
To the Editor of the Scientific American:
Mr. Edison finds a resemblance between his carbon telephone and my microphone.
I can find none whatever; the microphone in its numerous forms that I have already made, and varied by many others since, is simply the embodiment of a discovery I have made, in which I consider the microphone as the first step to new and perhaps more wonderful applications.
I have proved that all bodies, solid, liquid, and gaseous, are in a state of molecular agitation when under the influence of sonorous vibrations; no matter if it is a piece of board, walls of a house, street, fields or woods, sea or air, all are in this constant state of vibration, which simply becomes more evident as the sonorous vibrations are more powerful. This I have proved by the discovery that when two or more electrical conducting bodies are placed in contact under very slight constant pressure, resting on any body whatever, they will of themselves transform a constant electrical current into an undulatory current, representing in its exact form the vibrations of the matter on which it reposes; it requires no complicated arrangement and no special material, and to most experimenters the three simple iron nails that I have described form the best and most sensitive microphone. But these contact points would soon oxidize, so naturally I prefer some conducting material which will not oxidize.
Mr. Edison's carbon telephone represents the principle of the varying pressure of a diaphragm or its equivalent on a button of carbon varying the amount of electricity in accordance with this change of pressure; it represents no field of discovery, and its uses are restricted to telephony.
The three nails I have spoken of will not only do all, and that far better than Edison's carbon telephone in telephony, but has the power of taking up sounds inaudible to human ears, and rendering them audible, in fact a true microphone; besides it has the merit of demonstrating the molecular action which is constantly occurring in all matter under the influence of sonorous vibrations.
Here we have certainly no resemblance in form, materials, or principles to Mr. Edison's telephone. The carbon telephone represents a special material in a special way to a special purpose.
The microphone demonstrates and represents the whole field of nature; the whole world of matter is suitable to act upon, and the whole of the electrical conducting materials are suitable to its demonstrations.
The one represents a patentable improvement; the other a discovery too great and of too wide bearing for any one to be justified in holding it by patent, and claiming as his own that which belongs to the world's domain.