b FOSSIL MAMMALIA. 



Now, the action of the waters, whether in rains, thaws, or 

 running streams, which extend the land by the eventual depo- 

 sition of debris, presupposes the existence of mountains, vallies, 

 plains, and other inequalities, and consequently could not have 

 produced them. The action of the sea is still more limited, 

 and its phenomena have no affinity with the immense masses 

 of whose revolutions we have been speaking ; and volcanoes, 

 though they have formed both mountains and islands, formed 

 them of nothing but lava, i. e. of substances modified by vol- 

 canic action, which is never the case with the substances to 

 which we have above alluded, nor do volcanoes ever disturb the 

 strata which traverse their apertures. In a word, none of the 

 agents acting on the earth's surface with which we are now 

 acquainted, are capable of producing those tremendous revo- 

 lutions which have left their traces so indelibly marked on the 

 external covering of the globe. Neither will the circular motion 

 of the pole of the earth, nor the gradual inclination of its axis 

 on the plane of the ecliptic, better serve to explain such phe- 

 nomena. The slowness and limited direction of these motions 

 bear no proportion to the extent and overwhelming rapidity of 

 such catastrophes. It follows, then, that they must have been 

 occasioned by causes whose operation has long ceased, which 

 were external to this planet, and most probably totally out of 

 the course of things in existing nature. Many conjectures 

 have been made by naturalists respecting the character of these 

 causes, some eminent for absurdity, and all resting on hypo- 

 thesis; into any of which it would be as wide of our design to 

 enter as to propound any new solution of our own. It is 

 enough to repeat that nothing in the agency of nature, as it 

 has operated for ages in relation to this earth, could have pro- 

 duced the grand revolutions which this earth has evidently 

 undergone ; nor is it any absurdity to suppose that the agency 

 which did produce them was preternatural. 



To return to our more immediate subject ; it is comparatively 

 but a short time since the studv of marine fossils has been 



