Detrital Theory of Geology. 



301 



transitionary rocks, in some occupying a limited range in 

 their constituent parts, and in others by far the greater 

 bujk, % whilst at all times it is very limited in granite. 



The most important step in such an inquiry is to ascer- 

 tain, as near as may be, the chemical composition of 

 granite ;* and to this end a table (No. I Table) is supplied, 

 chiefly gathered from a FEW of the analyses of Bischof, and 

 added to those of Brande and Page. In this table many 

 minerals known to exist in granite, but which are only 

 occasionally found, such as orthite, apatite, &c., are 

 designedly omitted, as also is garnet (which occurs more 

 frequently in eruptive rocks than in granite, and which, 

 moreover, in its chemical composition in relation to lime is 

 very variable, lime being sometimes altogether absent), 

 because the quantity of lime derivable from such sources is 

 too inconsiderable to deserve attention. 



TABLE I. 



* In examining the analyses of granite, a careful distinction ought to 

 be made between the granitic and granatoid rocks. 



