Ch. III.] COMPARED WITH THOSE OF CORNWALL. 35 



binary combination of quartz and shorl ; facts which point 

 out to us that all well-marked compounds of distinct minerals 

 ought to be distinguished by appropriate names, although 

 they may be only known to exist in small quantities. The 

 above specified binary compounds are as much entitled to dis- 

 tinct names as shorl-rock : if they be not required in the one 

 case, neither is it necessary in the other ; so that the terms 

 shorl-rock, hornblende-rock, and others, should be expunged 

 from the geological nomenclature, if this view be persisted in. 

 If the knowledge of the primary rocks be a study worth pur- 

 suing, a mineralogical classification must be ultimately adopted; 

 for, accurate details concerning their transitions into each 

 other, and their modes of association, cannot be given on the 

 present system. This topic will be reverted to ; but in passing 

 we cannot help seizing every opportunity to urge the necessity 

 of this reformation, being firmly convinced that no measure 

 will tend more to promote the progress of this department of 

 the science. 



