746 PROFESSOR FLEEMING JENKIN AND J. A. EWING ON THE 
As compared with Konte’s flames, the method now described has the great 
advantage of continuity. This advantage it also possesses over the direct 
analysis by means of resonators ; and, moreover, it leaves nothing to the sub- 
jective appreciation of the observer. 
The phonograph used in our experiments differed in some respects from 
any of which we have seen published accounts. A plan and side elevation 
of the instrument is shown in Plate XX XIV., the scale of which is one- 
third of the full size; ¢ is the spirally-grooved cylinder on which the tin- 
foil which was to receive the impression was placed. It was supported 
by the axle a. On another axle 0, was a heavy fly-wheel z. The two 
axles were connected by two pulleys pp, and a cord, marked by dotted 
lines in the figure. These pulleys were of such diameters that 6 made 
four revolutions for each revolution of a. Each axle had cut on it a screw 
working in a fixed nut used as one of the bearings. The screw on @ was 
of the same pitch as the spiral groove on the cylinder c, and that on } 
was of one-fourth that pitch; so that as the fly-wheel revolved the pulleys 
which communicated motion from one axle to the other advanced together lon- 
gitudinally, and remained always in the same plane with one another. By this 
arrangement the power of the fly-wheel to give uniformity of motion was much 
increased without giving too great a speed of revolution to the cylinder. The 
mouthpiece m, which is shown in section, and its mode of support, also deserve 
notice. The mouthpiece consisted of an inner and an outer brass tube; the 
outer tube was fixed to the stand, and the inner tube was clamped in its place 
by a screw passing through the top of the other. On the end of the inner tube 
the speaking disc was fastened—consisting of a ring e, of oil-silk and a central 
cone J, of stiff paper. At the apex of the cone was the pointer which indented — 
the tinfoil. It was of hard steel, shaped like a slightly rounded chisel, and 
sharp in the horizontal plane. It was further supported and directed by a short 
piece of watch-spring gy, which was rigidly secured to a projecting bracket h. 
This form of speaking disc was adopted after experiments with a great 
number of different shapes and materials. By other appliances much louder 
sounds could be obtained from the phonograph, but these were defective in 
distinctness, while this arrangement combined a moderate degree of loudness 
with remarkable clearness and purity of utterance. The loudness of the articu- 
lation was increased by placing a wooden mouthpiece, such as is used in Prof. 
GRAHAM BELL’s telephone, at the other end of the tube m, but this was found to 
damage the purity of the sounds, no doubt by making the tube act more as a 
resonator, which unduly favoured certain tones. As a sort of gauge of the merit 
which our phonograph possessed as a means of recording and reproducing 
sound, we may mention that no difficulty was felt by hearers in making out 
sentences as repeated by it, which had been originally spoken in their absence. 


