162 BULLETIN OF THE 



sounds in the visible part of the spectrum, excepting the extreme 

 half of the red. 



These experiments reveal the cause of the curious fact alluded to 

 in my paper read before the American Association last August — 

 that sounds were heard from selenium when the beam was filtered 

 through both hard rubber and alum at the same time. (See table 

 of results in Fig. 14.) 



(3.) A solution of ammonia-sulphate of copper was tried. 



Result : When placed in the path of the beam the spectrum 

 disappeared, with the exception of the blue and violet end. To 

 the eye the spectrum was thus reduced to a single broad band of 

 blue-violet light. To the ear, however, the spectrum revealed itself 

 as two bands of sound with a broad space of silence between. The 

 invisible rays transmitted constituted a narrow band just outside the 

 red. 



I think I have said enough to convince you of the value of this 

 new method of examination, but I do not wish you to understand 

 that we look upon our results as by any means complete. It is 

 often more interesting to observe the first totterings of a child than 

 to watch the firm tread of a full-grown man, and I feel that our 

 first footsteps in this new field of science may have more of interest 

 to you than the fuller results of mature research. This must be my 

 excuse for having dwelt so long upon the details of incomplete 

 experiments. 



I recognize the fact that the spectrophone must ever remain a 

 mere adjunct to the spectroscope, but I anticipate that it has a wide 

 and independent field of usefulness in the investigation of absorption 

 spectra in the ultra-red. 



Mr. Wm. B. Taylor inquired whether the sounds obtained from 

 the two absorpion bands of the ammonia-sulphate of copper were 

 octaves of each other. Mr. Bell replied that this matter had not 

 as yet been investigated. 



Prof. William B. Rogers, President of the National Academy 

 of Sciences, being present as an invited guest, paid a high tribute 

 to Mr. Bell upon the very great interest and high scientific value of 

 the discovery just announced. 



The next communication was by Mr. G. Brown Goode on the 



SWORD-FISH AND ITS ALLIES. 



