rocks were formed were undoubtedly held in 

 suspension in the air and in the water, and by 

 a gradual process were deposited in the bottom 

 of the ocean in layers, forming rocks of vari- 

 ous kinds, according to the nature of the sub- 

 stance deposited. Gradually the crust of the 

 earth was built up until it acquired a certain 

 thickness; when, either from shrinkage under 

 the crust a great void was formed until it could 

 not sustain its own weight, or the pressure 

 caused by confined gases and molten matter 

 produced an upheaval which broke the crust 

 of the earth outward, causing great wrinkles 

 that we call mountain ranges. Undoubtedly 

 both forces were active in producing these re- 

 sults. When the gases and- molten matter had 

 escaped through the rifts in the rocks caused 

 by the upheaval there must have been great 

 voids formed that were filled up by the shrink- 

 age of the earth, causing much irregularity in 

 its surface. 



In some places there were enormous eleva- 

 tions, and in others correspondingly deep de- 

 pressions. The water that before was evenly 

 distributed over the surface of the globe, after 

 the upheavals ran off into the lower levels, fill- 

 ing up the great valleys, forming the seas, and 

 leaving about one-third of the land surface 

 uncovered. It must not be supposed, however, 

 that the appearance of the land was caused by 

 one grand movement or upheaval, but that it 



