Review of Cleaveland’s Mineralogy. i 
three 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 apprehension of the 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: 
“ Butin 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 horn- 
blende, as a predominating ingredient, characterizes those 
MINERALS to which most geologists apply the name érap.” 
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 
class of rocks in which hornblende predominates, and perhaps 
a few others of minor importance usually associated with them. 
It is true, a rock composed of pure hornblende may be called 
trap, but itis 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 ¢rap or hornblende, 
should be trap or hornblende rocks, and greenstone should come 
i 4s a subdivision, and not form a distinct section. With these 
alterations, 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 
t the correction. 
