THE CRUST OF THE EARTH. 



it the matter still remaining in fusion. By the continued effect 

 of radiation the temperature of the surface would continually 

 decrease, and consequently the thickness of the solidified shell 

 would be continually augmented. At length the superficial 

 temperature would fall to such a point that the sublimated 

 matter would be precipitated on the surface, and when the super- 

 ficial temperature, falling still lower, would descend below the 

 boiling point of water, a general condensation of the vapour sus- 

 tained in the atmosphere would ensue, and the entire surface of 

 the globe would be covered with an ocean of uniform depth. 



If no disturbing force acted, this would have continued to be 

 the condition of the globe ; but the fused matter enclosed by the 

 solid crust being subject to effects more or less irregular, and 

 exercising unequal pressures, it was in some places protruded 

 upwards, and in others depressed. In this manner certain parts 

 of the solid crust were pushed above the level of the water, while 

 others may have suffered corresponding depressions. Instead, 

 therefore, of a universal ocean, the surface became diversified by 

 land and water. 



The action of the water upon the subjacent solid crust of the 

 earth by erosion and disintegration and exposure to atmospheric 

 action, produced various changes in its condition ; and' the parts 

 thus washed off being subsequently deposited at the bottom of the 

 waters, produced the incipient stratification which has been above 

 described. 



"When the temperature of the globe was reduced to such a point 

 as to be compatible with the existence of organised bodies, the 

 first forms of life were called by the Creator into existence, and 

 were such as were adapted to the then physical condition of the 

 globe, being, as might be expected, exclusively marine tribes. 

 When subsequently land emerged from the ocean, and by the 

 condensation and precipitation of vapour rivers and lakes were 

 formed, terrestrial, fiuviatile, and lacustrine tribes were called 

 into existence. 



50. As each successive stratum was thus formed, the remains 

 of the animals and vegetables of the epoch were deposited in 

 them, and have accordingly been preserved to our times. Fiu- 

 viatile and land animals, in greater or less numbers, were swept 

 into the embouchures of rivers, and there deposited like the 

 others. Lacustrine tribes were, in like manner, deposited in the 

 bottoms of vast lakes or inland seas. 



51. But, besides these, there are indications of other changes 

 either gradual or sudden, which would explain the deposition of 

 terrestrial organic remains in the strata. There are evidences 

 that the swellings upwards and subsidence downwards of the 



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