A, G. Bell— Production of Sound by Radiant Energy. 468 
Art. LVIII.—Upon the Production of Sound by Radiant 
Energy ; by ALEXANDER GRAHAM BELL. 
[Read before the National Academy of Sciences, April 21, 1881.] 
IN a paper read before the American Association for the 
Advancement of Science, last August, I described certain ex- 
periments made by Mr. Sumner Tainter and myself which had 
resulted in the construction of a “ Photophone,” or apparatus 
for the production of sound by light ;* and it will be my ob- 
ject to-day to describe the progress we have made in the inves- 
tigation of photophonic phenomena since the date of this com- 
munication, 
n my Boston paper the discovery was announced that thin 
disks of very many different substances emitted sounds when 
exposed to the action of a rapidly-interrupted beam of sunlight. 
he great variety of material used in these experiments led me 
to believe that sonorousness under such circumstances would 
be found to be a general property of all matter. 
' At that time we had failed to obtain audible effects from 
masses of the various substances which became sonorous in the 
upon the material composing the tube. _ 
At this stage our experiments were interrupted, as circum- 
Stances called me to Europe. : 
While in Paris a new form of the experiment occurred to 
my mind, which would not only enable us to investigate the 
sounds produced by masses, but would also permit us to test 
the more general proposition that sonorousness, under the influ- 
ence of intermittent light, is a property common to all matter. 
* Proceedings of American Association for the Advancement of Science, Aug. 
27th, 1880; see, also, this Journal, vol. xx, p. ; Journal of the American 
Electrical Society, vol, iii, p. 3; Journal of the Society of Telegraph Engineers 
3 of 
and Electricians, vol. ix, p. 404; Annales de Chimie et de Physique, vol. xxi. 
