Part 19 (2/2)

We should add that the cornet tube is an ”open” pipe So is that of the flute The clarionet is a ”stopped” pipe

[29] It is obvious that in Fig 136, _2_, a pulse will pass from A to B and back in one-third the ti 136, _1_

[30] The science of hearing; froans and Tuning,” p 245

Chapter XVI

TALKING-MACHINES

The phonograph--The recorder--The reproducer--The gra of records--Cylinder records--Gramophone records

In the Patent Office Museuton is a curious little piece ofaxle, which has at one end a screw thread chased along it The screw end rotates in a socket with a thread of equal pitch cut in it To the other end is attached a handle On an upright near the cylinder is mounted a sort of drum The membrane of the druitated by the air-waves set up by hus into a sheet of tinfoil wrapped round the cylinder, pressing it into a helical groove turned on the cylinder froraph ever made Thomas Edison, the ”wizard of the West,” devised it in 1876; and from this rude parent have descended the beautiful machines which record and reproduce hu accuracy

[Illustration: FIG 146--The ”governor” of a phonograph]

We do not propose to trace here the develop-machine; nor will it be necessary to describe in detail its mechanism, which is probably well known to most readers, or could be mastered in a very short time on personal exa that the wax cylinder of the phonograph, or the ebonite disc of the graenerally rotated by clockwork concealed in the body of the overned, in order that the recordpoint at a uniforovernor co 146 The last pinion of the clockwork train is ular plates, A and C, to which are attached three short lengths of flat steel spring with a heavy ball attached to the centre of each A is fixed; C moves up the shaft as the balls fly out, and pulls with it the disc D, which rubs against the pad P (on the end of a spring) and sets up sufficient friction to slow the clockwork The liulated by screw S

THE PHONOGRAPH

Though the recording and reproducing apparatus of a phonograph gives very wonderful results, its construction is quite simple At the same time, ithas been devoted to finding out the most suitable materials and forms for the parts

[Illustration: FIG 147--Section of an Edison Bell phonograph recorder]

The _recorder_ (Fig 147) is a little circular box about one and a half inches in diameter[32] From the top a tube leads to the horn The bottoed at one side This plate supports a glass disc, D, about 1/150th of an inch thick, to which is attached the cutting stylus--a tiny sapphire rod with a cup-shaped end having very sharp edges Sound-waves enter the box through the horn tube; but instead of being allowed to fill the whole box, they are concentrated by the shi+fting nozzle N on to the centre of the glass disc through the hole in C C You will notice that N has a ball end, and C C a socket to fit N exactly, so that, though C C and N move up and down very rapidly, they still make perfect contact The disc is vibrated by the sound-i point down into the surface of the wax cylinder, turning below it in a clockwork direction The only dead weight pressing on S is that of N, C C, and the glass diaphragm

[Illustration: FIG 148--Perspective view of a phonograph recorder]

As the cylinder revolves, the recorder is shi+fted continuously along by a leading screw having one hundred or more threads to the inch cut on it, so that it traces a continuous helical groove froroove is really a series of very1/1000th of an inch in depth[33] Seen under a microscope, the surface of the record is a succession of hills and valleys, so 151, _a_) A loud sound causes the stylus to give a vigorous dig, while low sounds scarcelyis, that not only are the fundamental tones of musical notes impressed, but also the harmonics, which enable us to decide at once whether the record is one of a cornet, violin, or banjo perfor simultaneously near the recorder's horn, the stylus catches all the different shades of tone of every note of a chord There are, so to speak, minor hills and valleys cut in the slopes of the main hills and valleys

[Illustration: FIG 149--Section of the reproducer of an Edison Bell phonograph]

[Illustration: FIG 150--Perspective view of a phonograph reproducer]

The _reproducer_ (Fig 149) is somewhat more complicated than the recorder As before, we have a circular box colass disc forms a bottos, R R, by a screw collar, C To the centre is attached a little eye, froe of the box is a _floating weight_, having a circular opening ih this to the left end of a tiny lever, which rocks on a pivot projecting froht end of the lever is affixed a sapphire bar, or stylus, with a ball end of a dia point of the recorder The floating weight presses the stylus against the record, and also keeps the link between the rocking lever of the glass diaphragiven to the stylus is therefore transm, which vibrates and sends an air-iiven at the sam of the recorder, the sounds which they represent are accurately reproduced, even to the harmonics of a musical note

THE GRAMOPHONE

This effects the saraph, but in a sos vertically doards into the surface of the record, whereas the stylus of the gras fro 151_b_) It - stylus be moved sideways or vertically by the record, provided that m

[Illustration: FIG 151_a_]