SECTION III., 1901. [48 ] Trans. R. S. C. 
VII—A_ Century of Progress in Acoustics:—Presidential Address 
to Section. 
By PRESIDENT J. Loupon, LL.D. 
(Read May 23, 1901.) 
In selecting. the Progress of Acoustics, on its experimental side, 
as the subject for this year’s Presidential Address, I am fully alive to 
the fact that this branch of science has. been comparatively neglected 
by physicists for many years, and that consequently I cannot hope to 
arouse the interest which the choice of a more popular subject migüt 
command. It is, however, just because of this neglect of an important 
field of science that I conceive it to be my duty to direct some atten- 
tion thereto. This duty I can best perform, it seems to me, by taking 
a survey of the work accomplished in this particular field during the 
century that has just closed. Such a survey will make it evident not 
only that the science of acoustics has made immense progress during 
that time, but also that many of the experimental methods in use in 
other branches of physical science were invented and first employed 
in the course of acoustical research. This latter fact, though not gen- 
erally recognized, furnishes an illustration of the interdependence 
which exists between the various branches of physical science, and 
suggests the probability that the work of acoustical research in the 
future may be advanced by experimental methods specially designed 
for investigation in other fields. A revival will, of course, come in 
time for acoustics, as it has recently come for electricity, and it ought 
to come all the sooner because of the co-operation which physicists 
may naturally look for from those who are cultivating the new fields 
of experimental psychology. 
In order to avoid the tedium of a bare enumeration of discoveries 
arranged chronologically, I propose to refer, in the first instance, to 
the invention of the various experimental methods which have been 
employed in acoustical research. A separate reference to these methods 
will enable us to appreciate their potency in the advancement of this 
science. : 
The earliest of these methods is due to Chladni whose work “Die 
Akustik” appeared in the form of.a French translation in 1809 under 
the title “Traité d’Acoustique de Chladni”. In this work were col- 
lected all the researches on the vibrations of bodies which Chladni had 
conducted with the aid of the new method (méthode de sable.) This 
method consists in distinguishing, on the surfaces of vibrating bodies, 
