THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



JUNE 1878. 



LVII. Some Electrical Experiments with Crystalline Selenium. 

 By Robekt Sabine*. 



THE following experiments were undertaken with the view 

 of removing, if possible, some of the difficulties which I 

 had found in the way of constructing constant resistances of 

 crystalline selenium. 



For convenience, I propose to retain the order in which the 

 experiments suggested themselves and were made, and shall 

 therefore divide the following account of them into (1) the 

 experiments with crystalline selenium in darkness, and (2) its 

 behaviour in light. 



The experiments were made with several specimens of sele- 

 nium, some of which were provided, when in the amorphous 

 state, with platinum wires. The process of annealing was 

 done in an iron pot contained in an oil-bath, the temperature 

 of which could be kept steady at any required degree. The 

 selenium was made in the form of plates about 0*1 centim. 

 thick, 0*5 to 1 centim. broad, and 2 to 3 centims. long, wires 

 (when employed) being inserted transversely at equal distances 

 apart. In some specimens, the wires were laid upon a small 

 piece of mica or platinum-foil, and the melted selenium dropped 

 upon them : in others the platinum wires were heated to in- 

 candescence in a smokeless flame, and, while still hot, were 

 imbedded in the amorphous selenium. The two methods ap- 

 peared to be capable of giving equally firm contact, which 

 was probably due chiefly to the contraction of the selenium 

 round the platinum wire. 



* Communicated by the Author. 



Phil. Mag. S. 5. Vol. 5. No. 33. June 1878. 2 D 



