34 



rious necessity for general terms ; since, as numer- 

 ous inineralogical varieties occur, often under 

 every mode of gradation, yet under one general 

 relation to the surrounding rocks, the want of these 

 terms would render such descriptions unintelli- 

 gible. 



\ 



Further, as rocks are chiefly studied, so are 

 they chiefly to be named for the purposes of geo- 

 logy; and the plan of a nomenclature should 

 therefore, like that of a classification, be made 

 conducive to those ends. The general terms 

 should be founded on the geological relations, or 

 should at least, be invariably associated with them ; 

 as far as terms are wanted for varieties, it is indif- 

 ferent from what source they are drawn, provided 

 they do not interfere with the main object, nor 

 excite improper associations respecting the true 

 place of a rock in the order of nature. 



It is the perfection of the study, as of the de- 

 scription of natural objects, to combine, with ac- 

 curacy in the details, comprehensive general 

 views. To be anxious only about the former, 

 takes off the attention of the student from the lat- 

 ter ; and, in attending to the minutiae of an ar- 



