PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 783rd meeting was held at the Cosmos Club, February 3, 1917. 

 Vice President Burgess in the chair; 61 persons present. The min- 

 utes of the 782nd meeting were read in abstract and approved. 



A letter signed by several members of the society, calling attention 

 to the recently organized American Metric Association, was read. 



Mr. Arthur W. Clime, introduced by Mr. Alexander Graham Bell, 

 presented a communication on Photoelectric radiophonic experiments. 



Mr. Bell, in introducing Mr. Clime, spoke of the history of se- 

 lenium. He referred to the remarkable property possessed by crystal- 

 line selenium of having its electrical resistance affected by light; and 

 of the utilization of that property in the construction of the photophone. 

 He also referred to the discovery made by the late Prof. W. G. Adams, 

 of King's College, England, that light produced an electromotive force 

 in crystalline selenium. Mr. Bell had suggested to Mr. Clime that 

 this opened up a new field for scientific investigation and recommended 

 him to follow out the experiments of Prof. Adams by applying the 

 results to radiophonic researches. He had also pointed out to Mr. 

 Clime that the remarkable properties of carbon in radiophonic work 

 would well bear exploration. 



Mr. Clime then exhibited some of the radiophonic apparatus he 

 has constructed, and spoke of the results that had been obtained. 

 He showed a selenium cell which, when exposed to an intermittent 

 beam of light, caused a telephone connected with it to emit a musical 

 sound even when there was no battery in the circuit. The result he 

 claimed was due to an electromotive force produced in the crystal- 

 line selenium by the action of light. He also showed a cell in which 

 the selenium had been replaced by lampblack. So long as there was 

 a voltaic battery in the circuit the telephone responded well when the 

 lampblack surface was illuminated by an interrupted beam of light, 

 but he was unable to detect any audible effect when the batterj r was 

 removed. A cell in which a mixture of selenium and lampblack was 

 employed was then exhibited. In this case the sonorous responses of 

 the telephone were very loud even when no battery was used. The 

 musical tone was clearly perceived when the telephone was held at a 

 distance of several inches from the ear. On. account of the magnitude 

 of the sound produced by the selenium-carbon mixture, Mr. Clime 

 predicted the possibility of producing, by the action of sunlight, an 

 electromotive force of sufficient power to be of economic value. 



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