78 CHARACTERS OF STRATA 



the same chapter. If any thing could prove the gra- 

 dual and mechanical nature of this process, it is the 

 state and existence of fossil shells in the calcareous 

 strata, the successions of generations of animals en- 

 tangled in mud, arising partly from their own sources, 

 partly from extraneous materials, and deposited ac- 

 cording to the strict rules of mechanical arrangement. 

 The Oyster banks of our own times are their copies 

 or types; and they wait only for that time and these 

 changes, by aid of which they are destined to form 

 the limestones of a future earth. 



The preparation of the strata is a tedious process: 

 that it has been the work of incalculable time, requires 

 no other proof than that now mentioned; though 

 endless proofs of the same nature are found in the 

 nature of the strata themselves, and in the changes 

 now going on upon the surface of the earth. 



The deposition of regular strata of loose materials 

 in distinct succession, may be seen every day, in the 

 sections of lakes arid marine sestuaries. A lake is 

 but the image and model of a sea ; an sestuary is a por- 

 tion of the ocean itself. By whatever hydrostatic or 

 mechanical laws, therefore, the process of stratification 

 lias been regulated in these, it must have been similarly 

 regulated in the ocean itself. It is a problem in which 

 magnitude does not form an element of calculation. 

 As far as relates to a single deposit, even the precise 

 mode in which the materials are distributed on the 

 bottom can be defined; since it consists in a com- 

 bination of the force of gravity and the resistance and 

 motion of water. The diminution of the former 

 power, arising from the different specific gravities of 

 the earths and of water, added to the minuteness of 

 the materials, which thus expose a large relative sur- 

 face to the mechanical impulse of the water, permits 



