THE STORY OP THE EARTH 33 



our planet. The first solid crust that formed on the 

 molten earth is probably nowhere accessible to-day. In 

 most parts of the earth it is buried under the stratified 

 rocks, or the layers of sand, mud, etc., that have been 

 subsequently worn off the face of the earth and deposited 

 in seas and lakes. Where we have igneous rock at the 

 surface granite, basalt, or other rock that is clearly a 

 cooled mass of molten matter we have most probably 

 (in most cases quite certainly) the outcome of later 

 eruptions from below the crust. This is, at all events, 

 the general feeling of geologists. Moreover, there is 

 firm ground for thinking that the primitive crust was 

 spread fairly evenly over the surface of the planet. 

 That it would have nothing like the evenness of a sheet 

 of ice goes without saying. It was formed in an age of 

 convulsions, and after a titanic struggle with the up- 

 heaving forces below it. But there were none of those 

 large ranges of mountains that later, as we shall see, 

 puckered and crumpled the crust into gigantic folds, and 

 by far the greater part of the existing continents has 

 been raised above the level of the water subsequently. 

 The aspect of the earth would probably be at first one of 

 an almost continuous ocean, without the abysses we 

 know in it to-day, broken by comparatively small ridges 

 or islands, round the fringes of which the boiling ocean 

 raged furiously. The withdrawal of the enormous 

 weight of the oceans from the atmosphere, as the water 

 settled on the crust, would have a marked effect on such 

 dry land as there was. It would be relieved of the 

 earlier pressure of about 5,000 Ib. to the square inch, 

 and would yield more easily to the pressure from below. 

 Volcanic action on a colossal scale would thus greatly 

 enlarge the size of the first island-continents. 



But the atmosphere, though relieved of its vast 

 quantities of steam, would still be much heavier, denser. 



