83 Outlines of Geology. 



formed of materials collected through a series of ages in the bo- 

 som of an aqueous abyss ; and one of the first problems we are 

 called upon to solve, is the cause of the change of level in this 

 ocean, and of the emersion of our present land. It is difficult to 

 conceive any considerable change in the actual quantity of water, 

 resulting either from its transmutation or decomposition ; yet such 

 causes must not be excluded as impossible. But the most obvious 

 solution of the difficulty is founded upon the supposition that cer- 

 tain powerful agents have elevated our present continents, and at 

 the same time depressed the bed of the ocean ; what was once, 

 therefore, the bottom of an antediluvian sea, now appears to be 

 our habitable land ; and perhaps the dry land of a very remote 

 period of the world, may be the bottom of the present sea. This 

 disruption and elevation of the strata is not by any means a mere 

 gratuitous assumption, for independent of the verticality of loose 

 gravel beds, and other highly inclined strata which must have 

 been once vertical, we have so many other instances of disloca- 

 tions and heavings up of the strata among the old as well as 

 among the newer rocks, as, in the opinion of some, to demonstrate 

 to the utmost certainty the agency of an irresistible elevating 

 force ; but here the inquirer will perhaps stop to ask what force 

 or what power in nature could have been adequate to such extra- 

 ordinary and gigantic effects ; a question which must be answered 

 by minute inquiry into the position of the strata, their associations, 

 texture, and derangements, and by a comparison of these with 

 powers and causes now active or subject to our control and inves- 

 tigation. 



Another geological consideration, independent in a manner of 

 the former, but of much interest, and of some difficulty, relates to 

 the causes which have been active in producing the present more 

 superficial appearances oi ih.Q earth ; in carving it out into valleys, 

 and fitting it as it were for the order of things which now 

 prevails. 



Valleys are more or less extensive furrows of the surface, rami- 

 fying generally to a considerable lateral extent, and independent 

 of secondary purposes, fulfilling that most essential one of drain- 



