CONQUEST OF TIME AND SPACE 



cently discovered by Mme. Curie." In point of fact, 

 selenium is neither radioactive nor of recent discov- 

 ery. Moreover it is not a rare element. It is wide- 

 ly distributed in nature, but occurs in small quantities. 

 It was discovered and named by the famous Swedish 

 chemist Berzelius, as long ago as 1817. The word 

 selenium is from selenus, the Greek name for the 

 moon, and was given because the element is usually 

 found associated with tellurium (from tellurus, 

 earth) ; a fanciful association of ideas characteristic 

 of the imaginative mind of the discoverer, who was 

 one of the fathers of modern chemistry. 



While Dr. d'Albe's optophone is novel and spectac- 

 ular in its precise accomplishment, it depends upon 

 a principle that has previously been utilized in the 

 construction of several interesting mechanisms. The 

 fact that selenium conducts electricity only in the 

 light was discovered by a Mr. May and confirmed 

 and reported by Willoughby Smith, telegraph oper- 

 ators at Valencia, as long ago as 1873. It was at 

 once surmised that interesting applications of the 

 anomalous fact might in time be made. Some illus- 

 trations of the possibilities were given by Mr. Wm. J. 

 Hammer before the American Institute of Electrical 

 Engineers in New York. Mr. Hammer fired a cannon 

 over the heads of the audience by throwing a beam of 

 light from a distance; and he operated a five horse 

 power dynamo, alternately starting and stopping it 

 at will, merely by waving his hand across a beam of 

 light directed toward a selenium cell introduced in the 

 electric circuit. 



Mr. Hammer suggested that the cannon of a fort 



21 3*3 



