398 THE CANADIAN NATURALIST. [Vol. ix. 



color, which, under the action of the blow-pipe gave out a peculiar 

 odor, like that attributed by Klaproth to tellurium. As tellurium 

 was a substance of extreme rarity, Berzelius attempted its pro- 

 duction from this deposit ; but he was unable, after many experi- 

 ments, to obtain further indications of its presence. He found 

 plentiful signs of sulphur mixed with mercury, copper, zinc, iron, 

 arsenic and lead, but no trace of tellurium. It was not in the 

 nature of Berzelius to be disheartened by the result. In science 

 every failure advances the boundary of knowledge as well as every 

 success, and Berzelius felt that, if the characteristic odor, that 

 had been observed did not proceed from tellurium, it might 

 possibly indicate the presence of some substance then unknown to 

 the chemist. Urged on by his hope he returned with renewed 

 ardor to his work. He collected a great quantity of the material, 

 and submitted the whole mass to various chemical processes. He 

 succeeded in separating successively the sulphur, the mercury, the 

 copper, the tin, and the other known substances whose presence had 

 been indicated by his tests : — and after all these had been elimin- 

 ated, there still remained a residue which proved upon examina- 

 tion to be what he had been in search of — a new elementary sub- 

 stance. The chemical properties of this new element were found to 

 resemble those of tellurium in so remarkable a decree that Ber- 

 zelius gave to the substance the name of "Selenium," from the 

 Greek word selene, the moon — ('' tellurium," as is well known 

 being derived from tellus, the earth.) Although tellurium and 

 selenium are alike in many respects, they differ in their electrical 

 properties ; tellurium being a good conductor of electricity, and 

 selenium, as Berzelius showed, a non-conductor. Knox discovered 

 in 1837, that selenium became a conductor when fused; and 

 Hittorff, in 1852, showed that it conducted, at ordinary tem- 

 peratures, when in one of its allotropic forms. When selenium 

 is rapidly cooled from a fused condition, it is a non-conductor. 

 In this, its vitreous form, it is of a dark brown color, almost black 

 by reflected light, having an exceedingly brilliant surface. In 

 thin films it is transparent, and appears of a beautiful ruby red 

 by transmitted light. When selenium is cooled from a fused 

 condition with extreme slowness, it presents an eutirel}' different 

 appearance, being a dull lead color, and having throughout a gran- 

 ulated or crystalline structure, and looking like a metal. In this 

 form it is perfectly opaque to light, even in very thin films. This 

 variety of selenium has long been known as "granular" or 



