160 BULLETIN OF THE 



(3.) Upon substituting green silk for red worsted, the limits of 

 audition 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 max- 

 imum 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 violent 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 further on. 



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

 the vapor of iodine, the limits of audibility appeared to be the mid- 

 dle 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 cannot be certain. Upon examining th« absorption spectrum 

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

 sound was produced in that part of the spectrum where the great- 

 est number of absorption lines made their appearance. 



(8.) The spectrum was now explored by a selenium cell, and tbe 

 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 about its junction with the orange. 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 

 warranted in concluding that the nature of the rays that produce son- 

 orous effects in different substances depends upon the nature of the 



