CHAPTER X 



THE EARTH AS THE ABODE 

 OF LIFE 



IN the last chapter we spoke of the formation of the 

 atmosphere of the earth and of the growth of the 

 oceans. We must now consider the formation of 

 these more closely, and we must distinguish between the 

 great vaporous clouds which rolled about the earth in its 

 molten state and the settled atmosphere which formed 

 about it when it grew cooler. 



After the earth had begun to solidify it was at first 

 covered with a collection of porous fragments of rock 

 covering the earth like a shell and containing the ele- 

 ments of water. Such materials in general appearance 

 would be not unlike the pumice stone which is expelled 

 from volcanoes to-day. Those who have never had the 

 fortune to see volcanic eruptions for themselves usually 

 imagine that the volcano throws out nothing but fire and 

 smoke. As a matter of fact it throws out vast quantities 

 of vapour, of which, according to Sir Archibald Geikie, 

 999 parts in 1000 are steam. At the great eruption of 

 Mount Pelee the cloud of steam continually arising from 

 the volcano for months in succession was several cubic 



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