520 Prof. A. G. Bell on the Production of 



tended the inquiry to a number of other gaseous bodies, ob- 

 taining- in every case similar results to those noted in the 

 memoirs referred to. 



The vapours of the following substances were found to be 

 highly sonorous in the intermittent beam — water vapour, 

 coal-gas, sulphuric ether, alcohol, ammonia, amylene, ethyl 

 bromide, diethylamine, mercury, iodine, and peroxide of 

 nitrogen. The loudest sounds were obtained from iodine and 

 peroxide of nitrogen. 



I have now shown that sounds are produced by the direct 

 action of intermittent sunlight from substances in every physi- 

 cal condition (solid, liquid, and gaseous); and the probability 

 is therefore very greatly increased that sonorousness under 

 such circumstances will be found to be a universal property 

 of matter. 



Upon Substitutes for Selenium in Electrical Receivers. 



At the time of my communication to the American Asso- 

 ciation, the loudest effects obtained w T ere produced by the use 

 of selenium, arranged in a cell of suitable construction, and 

 placed in a galvanic circuit with a telephone. Upon allowing 

 an intermittent beam of sunlight to fall upon the selenium, a 

 musical tone of great intensity was produced from the tele- 

 phone connected with it. 



But the selenium was very inconstant in its action. It 

 was rarely, if ever, found to be the case that two pieces of 

 selenium (even of the same stick) yielded the same results 

 under identical circumstances of annealing &c. While in 

 Europe last autumn, Dr. Chichester Bell, of University Col- 

 lege, London, suggested to me that this inconstancy of result 

 might be due to chemical impurities in the selenium used. 

 Dr. Bell has since visited my laboratory in Washington, and 

 has made a chemical examination of the various samples of 

 selenium I had collected from different parts of the world. 

 As I understand it to be his intention to publish the results 

 of this analysis very soon, I shall make no further mention of 

 his investigation than to state that he has found sulphur, iron, 

 lead, and arsenic in the so-called "selenium," with traces of 

 organic matter, that a quantitative examination has revealed 

 the fact that sulphur constitutes nearly one per cent, of the 

 whole mass, and that when these impurities are eliminated, 

 the selenium appears to be more constant in its action and 

 more sensitive to light. 



Prof. W. G. Adams * has shown that tellurium, like sele- 



* Proc. Roy. Soc. vol. xxiv. p. 163. 



