GRANITE. 231 



syenite has been applied to this compound : but 

 with great inconvenience ; as it has also been 

 used to denote a member of the latest unstratified 

 rocks incumbent on the secondary strata. To 

 prevent additional confusion in the geological 

 description of two families of rock, often suffi- 

 ciently difficult to distinguish with every atten- 

 tion, it seems absolutely necessary to appropriate 

 this term exclusively to the granitic compound 

 which is posterior to the secondary strata. In a 

 geological arrangement, like the present, it is, 

 at any rate, indispensible. 



Granite therefore, consists fundamentally of 

 quartz, felspar, mica, and hornblende, variously 

 combined. But other minerals occasionally 

 enter into the composition, so as to form inte- 

 grant parts of a common mixture. They are, 

 it is true, comparatively rare, but they cannot 

 conveniently be excluded from the definition, 



These minerals are, actinolite, chlorite, talc 

 compact felspar, and steatite. This list might 

 perhaps be extended ; but the descriptions of 

 rocks hitherto published, are so unsatisfactory, 

 and the collections which have been formed, 



