OF ARTS AND SCIENCES. 



461 



conciltion. The table is merely a summing up of the results already 

 given, and exhibits a comparison of the atomic ratios * of the several 

 varieties. 



In the next table we bring together some farther noteworthy re- 

 sults, of which the details have already been given, indicating that in 

 the case of three, at least, of the vermiculites we have evidence of 

 different degrees of hj-dration corresponding to different tempera- 

 tures : — 



IV. VI. II. II 



* The atomic ratio is the same ratio wliich in most works on Mineralogy is 

 still called the oxygen ratio. The numbers given in this paper are found by 

 dividing the per cent of each oxide by a divisor, which is the quotient of the 

 molecular weight of the oxide divided by the quantivalence of the radical. 

 See writer's Chemical Philosophy, page 450, or Paper on Atomic Ratios, Am. 

 Jour., vol. xlvii.. May, 1869. 



