322 Tainter and Bell— Production of Sound by Light. 
Non-Electrie Photophonic Receivers. 
It is a well known fact that the molecular disturbance, pro- 
duced in a mass of iron by the erp influence of an in- 
termittent electrical current, can be observed as sound by plac- 
ing the ear in close contact with thods iron, and it occurred to us 
that the molecular disturbance pattie in crystalline selenium 
by the action of an intermittent beam ight should be audi- 
ble in a similar manner pehout the aid of a telephone or bat- 
tery. Many experiments were made to verify this theory, but 
at first without definite resu 
he anomalous behavior of, the hard rubber screen alluded 
to above suggested the thought listening to it a 
This experiment was tried w sient success. I 
held the sheet in close contact es my ear while a beam of 
intermittent light was focussed upon it by means of a lens. 
distinct musical note was immediately heard. We found the 
effect intensified by arranging the sheet of hard rubber as a 
diaphragm, and listening through a hearing tube, as shown in 
fig. 10. 
10. 
We then tried crystalline selenium in the this of a thin 
disc and obtained a similar but less intense 
The other substances, which I enumerated 7 ie commence- 
ment of my address, were now successively tried in the form 
of thin sasca and sounds were obtained from all but carbon 
and thin g 
In our acca iments, one interesting and suggestive feature 
was the different intensities of the sounds Shed from differ- 
ent substances under similar conditions. e found hard rub- 
ber to produce a louder sound than any other aR ea we 
tried, excepting antimony and zinc; and paper and mica to 
produce the weakest sounds 
On the whole, we feel we arranted i in announcing as our con- 
clusions that sounds can be produced by by the action “of a variable 
light from substances of all kinds when in the form of thin dia- 
* We have since obtained perfectly distinct tones from carbon and thin glass 
