DR T. THOMSON on Asbestus, Chlorite, and Talc. 359 



Silica, 58.804 



Magnesia, . .; uwx\. .v. . 28.236 

 Protoxide of iron, . . 9.479 

 Lime, oriT . .!* bh 5.926 



102.445 

 This is equivalent to 



34^ atoms silica, 



13 atoms magnesia, 

 _, .-, ,.. 



2^ atoms protoxide of iron, 



2 atoms lime. 



If we allow a small surplus of magnesia, indicated by the ex- 

 cess in the analysis, it is evident that the atoms of silica are just 

 double those of the bases, so that the mineral must consist of 

 bisilicates. It would appear at first sight, therefore, to differ 

 essentially from amphibole, which consists of C S 3 + 3 M S 2 . But 

 the analogy between the constituents and those of amphibole is 

 striking. And, if we were allowed to consider about 1 atom of 

 the protoxide of iron to be accidental, and the rest to replace 

 the lime, we would have 



which constitute the constituents of amphibole. I am disposed, 

 therefore, to consider the common asbestus, of which the mine- 

 ral analyzed was a specimen, as constituting a variety of amphi- 

 bole ; and in this respect agreeing with amianthus. 



