PRODUCTION OF SOUND BY RADIANT ENERGY. 329 



Fig. 11. 



ceiver (F) by the action of the same current, would be found capable 

 of extinguishing the effect produced in the receiver (G) by the action 

 of the undulatory beam of light, in which case it should be possible to 

 establish an acoustic balance be- 

 tween the effects produced by 

 light and electricity by introduc- 

 ing sufficient resistance into the 

 electric circuit. 



Upon the Nature of the 

 Rats that produce Soxorous 

 Effects ix Different Sub- 

 stances. In my paper read be- 

 fore the American Association 

 last August, and in the present 

 paper, I have used the word 

 " liglit " in its usual rather than 

 its scientific sense, and I have not 

 hitherto attempted to discrimi- 

 nate the effects produced by the 

 different constituents of ordinary 

 light the thermal, luminous, and 

 actinic rays. I find, however, that 

 the adoption of the word "pho- 

 tophone " by Mr. Tainter and my- 

 self has led to the assumption 

 that we believed the audible ef- 

 fects discovered by us to be due 

 entirely to the action of luminous 

 rays. The meaning we have uni- 

 formly attached to the words 

 " photophone " and " light " will 

 be obvious from the following: 

 passage, quoted from my Boston 

 paper : 



Althoiifrh effects are produced, as 

 above shown, by forms of radiant en- 

 ergy, which are invisible, we have 

 named the apparatus for the produc- 

 tion and reproduction of sound in this 

 way the " photophone," 'because an 

 ordinary beam of light contains the 

 rays ichich are operati}:e. 



To avoid in future anv misun- 

 derstandings upon this point, we 

 have decided to adopt the term 

 " radiophone,'''' proposed by M. 



^^ 



