EISING AND SINKING OF LAND, 23 



posed of different earthy constituents and enclosed different 

 petrifactions. 



The striking differences which so frequently occur be- 

 tween the petrifactions of two strata, lying one above 

 another, are to be explained in a simple and easy manner by 

 the supposition that the same part of the earth's surface has 

 been exposed to repeated depressions and elevations. Such 

 alternating elevations and depressions take place even now 

 extensively, and are ascribed to the heaving of the fiery 

 fluid nucleus against the rigid crust. Thus, for example, 

 the coast of Sweden and a portion of the west coast of 

 South America are constantly though slowly rising, while 

 the coast of HoUand and a portion of the east coast of 

 South America are gradually sinking. The rising as well as 

 the sinking takes place very slowly, and in the course of a 

 century sometimes only amounts to some few lines, some- 

 times to a few inches, or at most a few feet. But if this 

 action continues uninterruptedly throughout hundreds of 

 thousands of years it is capable of forming the highest 

 mountains. 



It is evident that elevations and depressions, such as 

 now can be measured in these places, have uninterruptedly 

 alternated one with another in different places during the 

 whole course of the organic history of the earth. This 

 may be inferred with certainty from the geographical distri- 

 bution of organisms. (Compare vol. i. p. 350.) But to form a 

 judgment of our palseontological records of creation it is ex- 

 tremely important to show that permanent strata can only 

 be deposited during a slow sinking of the ground under 

 water, but not during its continued rising. Wlien the 

 ground slowly sinks more and more below the level of the 



