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Heroes of the Telegraph [90]

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as the machine is required, to take down or to render back a phonographic message.

The recording tympanum, which is about the size of a crown-piece, is fitted with a mouthpiece, and when it is desired to record a sentence the spindle is started, and you speak into the mouthpiece. The tympanum vibrates under your voice, and the stylus, partaking of its motion, digs into the yielding surface of the wax which moves beneath, and leaves a tiny furrow to mark its passage. This is the sonorous record which, on being passed under the stylus of the reproducing tympanum, will cause it to give out a faithful copy of the original speech. A flexible india- rubber tube, branching into two ear-pieces, conveys the sound emitted by the reproducing diaphragm to the ears. This trumpet is used for privacy and loudness; but it may be replaced by a conical funnel inserted by its small end over the diaphragm, which thereby utters its message aloud. It is on this plan that Edison has now constructed a phonograph which delivers its reproduction to a roomful of people. Keys and pedals are provided with which to stop the apparatus either in recording or receiving, and in the latter case to hark back and repeat a word or sentence if required. This is a convenient arrangement in using the phonograph for correspondence or dictation. Each instrument, as we have seen, can be employed for receiving as well as recording; and as all are made to one pattern, a phonogram coming from any one, in any art of the world, can be reproduced in any other instrument. A little box with double walls has been introduced for transmitting the phonograms by post. A knife or cutter is attached to the instrument for the purpose of paring off an old message, and preparing a fresh surface of the wax for the reception of a new one. This can be done in advance while the new record is being made, so that no time is lost in the operation. A small voltaic battery, placed under the machine, serves to work the electric motor, and has to be replenished from time to time. A process has also been devised for making copies of the phonograms in metal by electro- deposition, so as to produce permanent records. But even the wax phonogram may be used over and over again, hundreds of times, without diminishing the fidelity of the reproduction.

The entire phonograph is shown in our figure. [The figure is omitted from this e-text] It consists of a box, B, containing the silent electro-motor which drives the machine, and supporting the works for printing and reproducing the sounds. Apart from the motive power, which might, as in the graphophone, be supplied by foot, the apparatus is purely mechanical, the parts acting with smoothness and precision. These are, chiefly, the barrel or cylinder, C, on which the hollow wax is placed; the spindle, S, which revolves the cylinder and wax; and the two tympana, T, T', which receive the sounds and impress them on the soft surface of the wax. A governor, G, regulates the movement of the spindle; and there are other ingenious devices for starting and stopping the apparatus. The tympanum T is that which is used for recording the sounds, and M is a mouthpiece, which is fixed to it for speaking purposes. The other tympanum, T', reproduces the sounds; and E E is a branched ear-piece, conveying them to the two ears of the listener. The separate wax tube, P, is a phonogram with the spiral trace of the sounds already printed on its surface, and ready for posting.

The box below the table contains the voltaic battery which actuates the electro-motor. A machine which aims at recording and reproducing actual speech or music is, of course, capable of infinite refinement, and Edison is still at work improving the instrument, but even now it is substantially perfected.

Phonographs have arrived in London, and through the kindness of Mr. Edison and his English representative, Colonel G. E. Gouraud, we have had an opportunity of testing one. A number of phonograms, taken in Edison's laboratory, were sent over with the instruments, and several
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