68 CLASSIFICATION OF ROCKS. 



however imperfect, is not only as valuable as a mi- 

 neral one for distinguishing these, but is decidedly 

 superior in the investigation of nature. The very 

 basis of geology is the knowledge of rocks; but that 

 knowledge is of little value for any other purposes. 

 If the mere mineralogist desires a mineralogical ar- 

 rangement of these, he is right; since, to him, rocks 

 are but collections of minerals. 



Leaving these to him, therefore, as the philosopher 

 in botany approves a classification of carnations with- 

 out following it, I must limit myself to those which 

 have been intended to facilitate the study of geology, 

 as declarations of the order of nature, whether truly so 

 or not. A tendency to arrangement, indeed, some love 

 of logic, good or bad, seems to be an inherent pro- 

 pensity in the human mind ; but if the sound rea- 

 soner adapts his logic to nature, the proceeding is 

 more commonly reversed; while, from the assimilating 

 powers of all systems, an artificial arrangement soon 

 becomes considered as a natural one. Thus, while its 

 inventor learns to see only through his own false me- 

 dium, his followers cease to enquire, because they be- 

 lieve. I hope to show that the classifications thus 

 esteemed natural, are, on the contrary, artificial. 

 They .cannot therefore be received as of the science of 

 geology ; it will be another enquiry, how far they are 

 useful in facilitating its study. 



Some early but imperfect observations gave rise to 

 the first separation of rocks into two classes ; but, 

 while the general principle has been preserved, we can 

 no longer reconcile this simple division to our en- 

 creased knowledge. All rocks were thus distinguished 

 into primary and secondary; characterized, respectively, 

 by high, and by low angles of elevation, or, as more 

 decidedly stated, by their vertical and their horizontal 



