358 THE CANADIAN NATURALIST. [Vol. viii. 



been changed into compounds with chlorine by long continued 

 exposure to hydrochloric fumes. 



The results from the examination of various micas are not 

 less important than those yielded by olivine, hornblende and 

 augite. But these are restricted to dark brown or black micas, 

 which are usually curtly called " magnesia-micas " or " biotites "; 

 but do not include the bright pure potash-micas or " muscovites," 

 as these usually occur in the primordial rocks only as rarities and 

 contain but 3-9 per cent, of iron, in whose company the heavy 

 metals are usually found. After I had once found (in 1870) 

 copper and cobalt in a dark brown mica out of the gneiss from 

 Petersthal in the Renchthal I pursued the subject farther and 

 was encouraged in my researches by Hardman's discovery in 

 Dublin of zinc, copper and lead in micas from the Irish granites 

 In order to obtain a commensurate result from my work I had 

 naurally to separate out and examine as large quantities as pos- 

 sible of fresh micas from the primary rocks of various ranges. 

 Only from a few localities could I obtain some 30 grammes, but 

 from others far less. The entire results are set forth in the 

 following table : — 



