Classifications of Rocks. 37 



the false medium which he has constructed, it is not wonderful 

 if those who follow him cease to inquire, and receive as proved, 

 that which is mere matter of hypothesis. I hope to show that 

 the classification of rocks which have been esteemed natural, 

 are, on the contrary, artificial. They must not, therefore, be 

 allowed to enter as constituents into the science of geology ; 

 and the only inquiry will be, how far they are useful in facili- 

 tating its study. 



An imperfect and ill-founded observation of Lehman gave 

 rise to the first notion of separating rocks into two classes. 

 That observation, as far as his researches and information 

 extended, appeared to have for its basis a real order of things ; 

 but, while the general principle has been preserved, the in- 

 crease of observations has accumulated so many exceptionable 

 facts, as to render it impossible any longer to reconcile to it 

 the state of our knowledge or the order of nature. It was con- 

 ceived that rocks could be easily distinguished into primary 

 and secondary ; the first being chiefly characterized by high, 

 and the last by low angles of elevation ; or, as more decidedly 

 stated, rocks were distinguished by their vertical and by their 

 horizontal positions. Hence the primitive and secondary 

 classes were established. 



Other geologists, improving on this system, have pointed 

 out the place where these two classes meet, or have attempted 

 to assign their common boundary ; and thus the arrangement 

 into two classes has been made more useful, if not more 

 natural. But as this distinction has been found to be attended 

 with some difficulty, a still more minute division has been 

 attempted, and rocks have been arranged in three classes ; a 

 division to which the name Transition has been applied as an 

 adjective term, having been introduced between the primitive 

 and secondary. This arrangement, promulgated by Werner, 

 has been adopted by many persons, and has been esteemed 

 strictly natural. This classification also has been connected 

 with a system of cosmogony, even more decidedly than that 

 which we must attribute to Lehman ; but it is not worth an 

 inquiry which of the two was the origin of the other, whether 

 the cosmogony or the classification preceded. It will pre- 

 sently appear that it is not only as defective as the more simple 



