670 REPORT—1896. 
paper moving at such a speed that the vibrations occurring in 0°5 second 
are spread over a distance of about 12 feet. The curves are thus greatly 
amplified, and the following facts may be demonstrated graphically :— 
(1) That many instruments have a curve-form so characteristic as to 
enable one by inspecting the curve to recognise the instrument. (2) That 
the curve-forms of sounds produced by instruments giving a pure tone 
are comparatively simple, while the curve-forms of instruments giving a 
mixed tone (with numerous partials) are more complicated. (3) That 
the curve forms of sounds produced by a band of music, or such a noise 
clang as that of a boiler-maker’s shop, are very complicated. (4) That if 
the tone of an instrument predominates in the sound of a band, the 
characteristic curve-form may be seen, modified to some extent by the 
other instruments. (5) That the curve-forms indicating a gradation from 
a tone of one pitch to a tone of another pitch may be observed. (6) That 
when numerous sounds, varying in pitch, follow each other in rapid suc- 
cession (as when a piece of music is quickly played), from ten to fifteen 
vibrations appear to be sufficient to enable the ear to appreciate the 
relative pitch of any one of the tones, or, in other words, pitch may be 
appreciated by vibrations lasting only a fraction of a second. This time 
cannot yet be definitely stated, as it has been found to vary from ./j>th to 
!,th of a second.! 
_ 2. The Committee has carefully studied the mechanism of the recording 
point in the English form of the phonograph, and they have constructed a 
model which makes the matter easily understood. The original tinfoil 
phonograph was so constructed that when the diaphragm was pressed 
inwards by the condensation of the air wave, the marker made a corre- 
sponding depression on the tinfoil, and when the diminution of pressure 
came on, corresponding to the rarefaction of the air wave, the marker 
passed away from the tinfoil. There were thus a series of marks the 
depth of each of which corresponded to the degree of pressure on the 
diaphragm. A hasty inspection of the more complicated apparatus 
in the English model might lead one to suppose that the action in it was 
of the same nature, but a careful scrutiny will show that this is not the 
case. By a large model made for the Committee it can be seen that, 
when pressure is made on the diaphragm, the effect is to cause the cutting 
edge of the recording gouge to be directed downwards. As the cutting 
edge of the gouge is directed against the wax cylinder, and is opposed to the 
rotation of the latter, it is evident that this change of the angle of the 
gouge to a downward direction will cause the gouge to cut a deeper 
groove into the wax cyliader. The depth of the groove, as determined by 
the angular movement, is therefore a measure of the pressure on the glass 
disk. It must be borne in mind that when no pressure is exerted on the 
glass disk the marker cuts a groove. When there is greater pressure, by 
the cutting edge being placed at a larger angle with the tangent of the 
curved surface of the cylinder, a deeper groove will be cut. On the other 
hand, when the cutting edge is placed at a smaller angle with the tangent 
of the curved surface of the cylinder a shallower groove will be ploughed 
on the surface of the wax cylinder. It follows that, if the sound acting 
on the wax cylinder of the phonograph be very intense, during the 
increase of pressure, the groove will be deep, and during the diminution 
1 A detailed account of the investigation will appear in the Trans. of the Roya 
Soc. of Hdin., 1896. ; 
