Review of Cleavdand' s Mineralogy. 51 



classes of primitive, transition, and secondary rocks, into 

 one class ; and where the same rock occurs in all the three 

 classes, or in two of them, he mentions-it in giving the history 

 of the particular rock. This method simplifies the subject 

 very much to the apprehensions of a learner. A rigid Werne- 

 rian would probably revolt at it, but the distinctions of Mr. 

 Werner may still be pointed out, and, we should think, ought 

 to be, at least by all teachers. 



In Mr. Cleaveland's account of the trap rocks, we should 

 almost imagine that some typographical error had crept into 

 the following paragraph : 



" But in modern geological inquiries, the word trap is usually 

 employed to designate a simple mineral, composed of horn- 

 blende nearly or quite pure, and also those aggregates in which 

 hornblende predominates. Hence, the presence of hornblende, 

 as a predominating ingredient, characterizes those minerals to 

 which most geologists apply the name trap.^^ 



Now, it is not accordant with our apprehensions that trap is 

 ever at the present time employed to designate a simple mine- 

 ral, nor has Professor Cleaveland himself used it in his tabular 

 view, or in his description of simple minerals. In our view, it 

 is the classical word of modern geology, to designate that descrip- 

 tion of rocks in which hornblende predominates, and perhaps a 

 few others of minor importance usally associated with them. 

 It is true, a rock composed of pure hornblende may be called 

 trap, but it is not true, vice versa, that this rock, considered in 

 its character of a simple mineral, is called trap. If our views are 

 correct, the section which is headed trap or hornblende, should 

 be trap or hornblende rocks, and greenstone should come in as a 

 subdivision, and not form a distinct section. With these alter- 

 ations, and with the substitution of rock in the Jirst, and rocks 

 in the second instance, in the paragraph above quoted, instead of 

 mineral and minerals, we apprehend the view of this family of 

 rocks would be much more clear, and a degree of confusion, 

 which learners now experience from the paragraph, would be 

 prevented. If we are wrong, we are sure Professor Cleaveland 

 will pardon us; if right, his candour will readily admit the 

 correction. 



