166 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



ON THE INFLUENCE OF LIGHT UPON THE CONDUCTIVITY OP 



CKYSTALLINE SELENIUM. 



Dr. Werner Siemens writes that he has investisrated the 

 conductivity of selenium as affected by light. He states 

 that although the selenium has an extraordinarily irregular 

 absorptive power, and although consequently the increase in 

 its conductivity by the action of light is very variable, yet 

 by soldering two pieces of flat spiral wire at a distance of 

 one millimeter from each other between two pieces of mica, 

 he was able to construct an extremely delicate measure of 

 light. Dark heat rays have no direct influence in this ar- 

 rangement upon the conductivity; warming the selenium 

 diminishes the conductivity. Diffuse daylight doubles the 

 conducting power, but direct sunlight increases this power 

 tenfold ; and he states that he hopes to be able, by means 

 of this mineral, to construct a reliable photometer. Monatsb. 

 h. Akad. der Wissens.^ Berlin, 1875, 280. 



CONDUCTION OF ELECTKICITY BY COMPOUNDS OF SULPHUR. 



According to the observations of Herwig, the resistance 

 which iron and steel offer to the passage of the galvanic cur- 

 rent varies with the direction, intensity, and duration of the 

 current itself. Similar phenomena have now been made 

 known from the observations of Braun in reference to a 

 large number of both natural and artificial compounds of 

 sulphur; the effects in question amount to thirty per cent, 

 of their entire value, so that of tlie existence of these differ- 

 ences there can be no question. A connection between the 

 crystallographic peculiarities of the minerals and the direction 

 of maximum or minimum galvanic resistance is not clearly 

 made out, although indicated in some cases. 19 C, VIII., 95. 



ON THE GLOW DUE TO GALVANIC CURRENTS. 



The experiments made by Mtiller in Freiburg a few years 

 ago gave the first correct information with respect to the 

 law which reojulates the Gflowino; of wires throuirh which a 

 current of galvanism is passing. Miiller's experiments and 

 methods have been the subject of a communication to the 

 Bohemian Academy of Sciences by Professor Yon Waltenho- 

 fen, who states that Miiller's results seem to accord less ac- 



