Selenium

a non-metallic element discovered by the chemist Berzelius in 1818. In the series of elements, it falls between sulphur and tellurium. It is found free in small quantities in connection with sulphur, and in compounds with copper, lead, mercury, silver, etc. In one of its forms, selenium is a red powder which melts on the application of heat. On cooling, it solidifies into a dark glassy mass. Selenium possesses a peculiar property. Its resistance to the passage of an electric current diminishes as the intensity of the light to which it is exposed increases. The metal is of no great importance in the arts. In combination with hydrogen it forms a gas quite as disagreeable as the sulphuretted hydrogen of rotten eggs.