Philip Quilibet.
SCIENTIFIC MISCELLANY.
THE TELEPHONE.
Great interest in telegraphic subjects has lately been aroused in the American public by exhibitions of the telephone, an instrument for transmitting sound vibrations by electricity. Two general forms of this instrument are known, in one of which a series of tuning forks communicates with a precisely similar series at the other end of the wire, and the signals made to one are repeated by the other. A more interesting form, and the one that has lately attracted so much attention, is that which receives and transmits ordinary vocal sounds. The operator talks to a membrane, and at the other end of the wire is a resonator of some kind which talks to the auditor there. The fundamental idea of the machine is not new. It was at first proposed to use it for transmitting electric signals without a wire, and in that view a trial was made with it during the siege of Paris. The armistice interrupted the operations, but M. Bourbouze, the experimenter, and other inventors have continued to study the subject, Mr. A. G. Bell, professor of vocal physiology in Boston, being among them. M. Bourbouze used a vibrating needle the movements of which were effected by sound waves, and another Frenchman, M. Reuss, introduced the sounding box with its membrane. This is a box with a membrane stretched over the top and a short tube of large diameter in the side. The operator talks to this tube, and the box strengthens the sound, which finally affects the membrane, causing it to vibrate. Resting upon this membrane is a thin copper disc attached to a wire leading from the electrical battery. Above and very near it hangs a metallic point, which forms the end of a wire leading to the place to which the message is to be sent. The membrane rises slightly with every vibration, and touching the point, a current is established and communication effected with the distant point; but this communication ceases as soon as the vibration stops, and the membrane assumes a state of rest. As every simple note is produced by a definite number of air vibrations, and every compound sound is made up of the sum of several simple notes, the apparatus transmits a definite number of vibrations for each sound which it receives; and if those vibrations can be communicated to the air at any point, however distant, the original sounds will be reproduced. In short, the instrument may be explained as one invented to transmit air vibrations by electricity.
The receiver consists of an iron rod about the size of a knitting needle, wound with insulated copper wire, and supported on a wood box having very thin sides. The rod vibrates with every passage of the current, and the thin box increases the amount of these vibrations and makes them audible. It is found best to introduce several rods into the insulated coil, as with only one the sound produced is rather snuffling. In either case, however, the vibrations of the rod are exactly the same as those of the membrane, and even the character of the sound is automatically reproduced.
The description here given is that of Reuss's instrument, which was illustrated last year in the French paper "La Nature." The exact construction of Mr. Bell's telephone has not been made public, but it seems to be quite similar. He is said to make his vibrating membrane of metal. The greatest distance to which sounds have been sent is one hundred and forty-three miles, from Boston to North Conway, N.H. The instrument is not yet perfect, the sounds being frequently indistinct. With a private wire and two persons accustomed to each other's voices it would probably be a greater success. It is therefore likely to be quickly introduced into business uses. At present some rather wild anticipations are indulged in by the daily press, but the instrument probably has a really remarkable future before it.
DAMAGES BY AN INSECT.