Page:Popular Science Monthly Volume 17.djvu/20

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the principal valuable positive conclusions have been derived from linguistic researches. In the dispute as to the relative merits of the zoölogical and philological methods in ethnology, I accordingly side with the advocates of the latter; and, in regard to the special subject of this paper, I say with Quatrefages, in the words of Virgil, "Ne crede colori."

By E. A. ENGLER, A. M.

ALTHOUGH the telephone seems to have sprung up among us very suddenly, there have been steps in its development which show that the difficulties encountered in devising a means for the transmission of articulate speech have not been overcome altogether by a single stroke of individual genius, but singly by the patient and, for the most part, unrewarded labor of many. Each stage of its development was the outgrowth of suggestions obtained from previous experiments. Of the instruments which served their purpose in the discovery of the properties of the carbon button, a brief description will be given in this paper.

Sound is known to be produced by vibrations, generally of air; differences between sounds are due to differences in vibration. There are but three essential characteristics to be noted, all dependent upon the vibrations of the air: 1. The pitch, by virtue of which a sound is called high or low, and which depends upon the number or rapidity of the vibrations; 2. The intensity or loudness, which is determined by the amplitude of the vibration; 3. The quality by which we distinguish the corresponding tones of different instruments, and which depends on the form of the vibration. In order to obtain an exact reproduction of any sound, its pitch, intensity, and quality must be exactly reproduced; and, to render this possible, the rapidity, amplitude, and form of the vibration must be exactly reproduced.

For producing sound at a distant place two methods suggest themselves: 1. Actually to transmit the sound vibrations through the air; this is the method employed in the speaking tube. 2. To reproduce the sound vibrations at the distant station; this is the method employed in the telephone. The previous development of the telegraph naturally suggested electricity as the agent to carry the vibrations from one place to another. It thus became necessary to convert sound waves into electric waves and vice versa, and experiments look-

  1. This paper, at first intended for a special occasion, has been published at the suggestion of several friends. In its preparation, use has been made of information to be found in George B. Prescott's work on the telephone, and in the journals of science. Most of the illustrations are from Prescott's work.