LIFE IN THE PRIMITIVE OCEAN 2^ 



would burst. Then the molten masses below would 

 pour up and over the crust. This would go on for 

 long ages, until the crust was thick enough to confine 

 the fiery giant below it. That is why we find the 

 earliest rocks, which represent half the life of the 

 earth, mainly volcanic. When the crust had set firm, 

 the great process of wearing down the rocks would 

 start, and the sand and fragments would begin to 

 form our "sedimentary" rocks at the bottom of 

 the sea. 



After these great upheavals the crust of the earth 

 would no longer be fairly even. There would be hills 

 and ridges, with corresponding valleys and depres- 

 sions. The waters would settle in the depressions, 

 and the division of "dry" land and water would 

 commence. As the crust becam.e thicker and more 

 irregular, great masses of it might be undermined by 

 water, far below, and sink or "subside," making 

 mighty hollows in the surface of the earth. Probably 

 our ocean-beds were formed in this way. It drained 

 the shallow seas off the rest of the crust, and made 

 more "dry" land. The land, in other words, has 

 been gaining on the water all through the history of 

 the earth. There was very little dry land at first, 

 and there were no mountains. There is more dry 

 land than ever to-day. 



This may seem to you to be not a very important 

 matter to dwell up n, when I have, for reasons of 

 space, to omit thousands of interesting features. On 



