198 
Proceedings of Royal Society of Edinburgh. [sess. 
cylinder (the circumference of the cylinder), or in a period of half a 
second. One foot of paper would therefore represent ~^th second, 
and 1 inch would represent of a second. 
The amplification vertically is nearly 1000 times, hut in the direc- 
tion of length it is only about thirty-five times magnified. To obtain 
the tracings so as to increase the amplification in length to corre- 
spond to the amplification in height, that is to say, to 1000 times, 
it would be necessary either to drive the phonograph thirty-six times 
slower, or a speed of one revolution in about five hours, or to roll 
out the paper thirty-six times faster, or about 864 feet in eight 
minutes instead of about 24 feet. Manifestly, either of these devices 
would be very inconvenient, and it is unnecessary to attempt to 
carry them out, as for purposes of analysis it does not matter. 
In the description of the curves of phonographic records taken 
by Hermann, nothing is said in explanation of the fact that the 
tracings are not amplifications to scale of the true marks on 
the phonograph cylinder. I show you here (1) a tracing of the 
vibrations of a bugle taken by my apparatus, giving an amplifi- 
cation about 1000 times vertically and thirty-five times in a linear 
direction, and (2) a tracing of a few of these curves enlarged 
longitudinally so as to have the vertical and longitudinal amplifica- 
tions equal — about 1000 times. It will be observed how the im- 
pressions are long shallow depressions, very shallow at first, 
gradually becoming deeper towards the centre, and again becoming 
shallow towards the other end. In this aspect they exactly 
resemble the grooves seen in photographs taken of portions of the 
surface of the wax cylinder. 
One of the chief difficulties in earlier experiments with this 
instrument was to secure that the point of the first lever always 
was in contact with the horizontal portion of the short arm of the 
second lever, and that, on the other hand, the pressure was not too 
great. If the mechanism be considered, it will be apparent that, 
supposing the groove on the wax cylinder to deepen, as would be 
the case if the sound recorded became more intense, the whole of 
the aluminium lever would fall and its point would press too heavily 
on the arm of the second lever. On the other hand, suppose the 
groove to become shallow, as happens when the sound is less intense, 
the aluminium lever would rise, and, as it is rigid, its point 
