672 REPORT—1896. 
sounds than the way in which it catches every inflection of the voice or 
the slightest emphasis, diminuendo, and crescendo of the sound. This 
must be due to variations of pressure. How may these variations be 
recorded ? 
The most evident method is to attempt to record mechanically the 
variations in an electro-magnet produced by pressures on a variable 
resistance apparatus in the same circuit. The first attempt of the 
Committee was to place Graham’s transmitter over the glass disk of the 
phonograph and to place in the same circuit an electro-magnetic marker 
such as is used for physiological purposes. This gave poor results, but 
still they were encouraging. On placing a Breguet’s chronograph in 
circuit the results were much better, and it was evident that there was a 
movement of the vibrator of the chronograph for each note or chord 
emitted by the phonograph. The Committee then heard of an ingenious 
apparatus devised by Heurtley of Breslau, by which he has succeeded in 
recording by electrical and mechanical arrangements the sounds of. the 
heart. His apparatus consists essentially of a large stethoscope on which 
a peculiar resonator is fixed. The resonator carries a small wooden 
tuning-fork, between the prongs of which is fixed a simple microphonie 
contact of two carbon buttons. This is one half of the apparatus. The 
other half consists of an electro-magnet, over the poles of which is fixed, 
face downwards, a shallow tambour, of the Marey pattern, having on its 
under surface a broad ferrotype plate. This tambour is then connected 
with an extremely delicate recording tambour. It is evident that the 
second half of this apparatus is exactly what is wanted for the phono- 
graph work, and, by the kindness of Professor Heurtley, the apparatus 
was made in Tiibingen without delay. When placed in the circuit along 
with the carbon transmitter the pen of the recording tambour moves at 
right angles to the line of revolution of the cylinder with each tone and 
chord played by the phonograph. When the ear perceives tones of con- 
siderable intensity the lever point is seen moving through a greater 
distance than when the tones are weaker; consequently we have a 
graphic record of the variations in intensity. If the recording cylinder 
is timed to travel at the same rate as the cylinder of the phonograph, 
then the curves on the former exactly correspond to the ensemble of the 
minute marks on the latter corresponding to a particular variation in 
intensity. When the recording cylinder is caused to travel as fast as the 
phonograph cylinder, the variation in the heights of the curves recorded 
on the revolving cylinder is not so apparent as when the recording 
cylinder travels more slowly. It is easy, however, to time the rate of 
revolution of both cylinders by a chronograph. Thus we have found that 
when the recording cylinder is travelling at such a rate that an extent of 
surface of one-fourth of an inch corresponds to one-fourth of a second, an 
easily read tracing is obtained. In such a distance we may have one little 
wave representing the pressure of a chord lasting for one-fourth of a 
second, or we may have from two to as many as fifteen little waves, often 
varying much in general character. Suppose we find as many as fifteen ; 
then each must have lasted not more than ,,th of a second. Even then 
the ear is able to follow the individual notes when the phonograph is 
listened to simultaneously. This may be readily done either by listening 
directly to the phonograph or by connecting a telephone with the secon- 
dary of an induction coil, while the current in which the variable resistance 
