PRODUCTION OF SOUXD BY RADIAXT EXERGY. 331 



terior of the receiver (G) was filled with red worsted. Upon explor- 

 ing the spectrum as before, entirely different results were obtained. 

 The maximum effect was produced in the green at that part where 

 the red worsted appeared to be black. On either side of this point 

 the sound gradually died away, becoming inaudible on the one side in 

 the middle of the indigo, and on the other at a short distance outside 

 the edge of the red. 



3. Upon substituting green silk for red worsted, the limits of audi- 

 tion appeared to be the middle of the blue and a point a short distance 

 out in the ultra-red maximum in the red. 



4. Some hard-rubber shavings were now placed in the receiver 

 (G). The limits of audibility appeared to be, on the one hand, the 

 junction of the green and blue, and, on the other, the outside edge of 

 the red maximum in the yellow. Mr. Tainter thought he could 

 hear a little way into the ultra-red, and to his ear the maximum was 

 about the junction of the red and orange. 



5. A test-tube containing the vapor of sulphuric ether was then 

 substituted for the receiver (G). Commencing at the violet end, the 

 test-tube was gradually moved down the spectrum and out into the 

 ultra-red without audible effect, but, when a certain point far out in 

 the ultra-red was reached, a distinct musical tone suddenly made its 

 appearance, which disappeared as suddenly on moving the test-tube a 

 very little farther on. 



6. Upon exploring the spectrum with a test-tube containing the 

 vapor of iodine, the limits of audibility appeared to be the middle of 

 the red and the junction of the blue and indigo maximum in the 

 green. 



7. A test-tube containing peroxide of nitrogen was substituted for 

 that containing iodine. Distinct sounds were obtained in all parts of 

 the visible spectrum, but no sounds were observed in the ultra-red. 



The maximum effect seemed to me to be in the blue. The sounds 

 were well marked in all parts of the violet, and I even fancied that 

 the audible effect extended a little way into the ultra-violet, but of 

 this I can not be certain. Upon examining the absorj^tion spectrum 

 of peroxide of nitrogen it was at once observed that the maximum 

 sound was produced in that part of the spectrum where the greatest 

 number of absorption lines made their appearance. 



8. The spectrum was now explored by a selenium cell, and the 

 audible effects were observed by means of a telephone in the same 

 galvanic circuit with the cell. The maximum effect was produced in 

 the red. The audible effect extended a little way into the ultra-red on 

 the one hand and up as high as the middle of the violet on the other. 



Although the experiments so far made can only be considered as- 

 preliminary to others of a more refined nature, I think we are war- 

 ranted in concluding that the nature of the rays that produce sonorous 

 effects in different substances depends upon the nature of the substances 



