14 
Abstract of Proceedings. 
Ig09. 
poo oo) 
GENERAL MEETINGS. 
Friday, January 8th. Mr. P. E. Vizard, Vice-President, in 
the chair. 
Mr. C. O. Bartrum, B.Sc., Secretary of the Society, gave a 
lecture on ‘‘ Talking Machines, their History and Scientific 
Principles,” illustrated with lantern and with a gramophone 
and an auxetophone lent by the Gramophone Company. The 
lecturer gave an elementary account of the mode of propagation 
of sound waves in the air; of the composition of musical notes 
and of complex sounds ; and of the complex wave forms which, 
striking on the drum of the ear, are analysed by that organ into 
their components, giving the sensations of the different sources 
from which they have proceeded. To show that sound waves are 
objective realities and not merely mathematical abstractions, a © 
photograph of a rifle bullet travelling at 2,000 feet per second 
and its accompanying sound waves was shown on the screen. 
This was taken by Mr. C. V. Boys, F.R.S., by the light of an electric 
spark as the bullet left the muzzle of the rifle. 
The lecturer showed that the form of any sound wave could 
be expressed by means of a curve, and that any body constrained 
by mechanical means to vibrate according to such a curve would 
radiate the corresponding sound. He pointed out that the spiral 
groove on the records of the phonograph and the gramophone 
had the character of such a curve, and showed by lantern slides 
how the diaphragm of the instruments was forced to vibrate and 
so to radiate the wave forms recorded. To make the records a 
soft wax disc is used, and the spiral groove is cut in the wax with 
a sapphire cutter attached to the recording diaphragm, the speaker, 
singer, or player, being close to the collecting bell of the instrument. 
From the wax a copper negative is made by electro-deposition, 
and from the copper negative the commercial records are stamped 
in a material plastic when hot, but very hard and tough when 
cold. The chief difference between the phonograph and the 
gramophone lies in the fact that with the former the wave form 
