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 basis is 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 for a 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, througli 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 volcanos — 

 descend through the 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. 



