320 



ON THE IGNEOUS METAMORPHOSIS 



[Ch. XIV. 



A TABLE 



OF THE COMPOSITION OF MINERALS CONTAINED IN THE 

 PRIMARY ROCKS. 



It may also be objected that some beds of primary rocks 

 do not contain alkali, whilst others, with which they alternate, 

 abound in felspar : that is, the same condition of these rocks 

 which intimates that an emanation of caloric from a central 

 igneous mass could not have produced the supposed meta- 



