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ee 8 eee 
Miscellanies. 389 
Although the lectures are necessarily long, (since the whole story 
of the actual structure of the crust of the globe and of its basisis told, 
as far as we know it,) they are conveniently divided under numerous 
heads, printed in small capitals, and thus the eye easily catches and 
reviews the various topics. — 
The plates are of the size of the volumes, so that there is no incon- 
venience from folded paper; and many appropriate wood cuts in con- 
nexion with the subjects, chequer the pages, and thus speak, through 
the eye, effectively to the mind. 
Many things might be said as to the best arrangement for a course 
of lectures, or fora work on geology. 
1. We may begin as Dr. Mantell has done, at the actual surface, and 
proceed from what we know and are familiar with, down through for- 
mations less and less known, until we arrive at the deep profound of 
the earth, the bathos of our ignorance; this is in the reverse order, 
both of the chronology and deposition of the strata, On the whole, 
this arrangement presents many important advantages, but leaves: 
the igneous phenomena unexplained until a late period. 
2. We may begin with the granite, the deepest rock of which we 
have any knowledge, and then in the ascending order, we meet only 
with materials with which we have been made acquainted, and of 
which the derivative rocks are constructed. We proceed also from! 
animals and plants, the least known, or entirely unknown, through 
successive families, more and more assimilated to those of our own 
times, and end with those that are identical with the existing races. 
3. We may begin with the granite and ascend through the ignige- 
nous rocks to the surface-fires of the actual volcanos, and then, de- 
scending through them, to their deep foci, ascend again, through the 
Schistose-primary, and fossiliferous rocks to the actual surface; or we 
may descend in the reverse order. 
4, We may begin with the cones of active and extinct voleanos— 
descend through ihe igneous rocks to the granite, and then up as be- 
fore, through the primary, transition, secondary and tertiary, to the 
actual surface, ending with the diluvial and alluvial. 
Having ourselves tried all these methods in instruction, we have 
preferred the 1st and 4th; and of these two, the latter, as putting us 
in early possession of igneous agency, the most potent, and the most 
concealed of the causes connected with geological dynamics, and 
leading us naturally through the sequel of aqueous agencies with 
which we are better acquainted. Still, our preference for this course 
is so slight, that for the sake of leading on a class by the aid of so 
instructive and delightful a guide as these volumes afford, we should 
not hesitate to adopt that course which Dr. Mantell has chosen. 
