86 THE WORLDS LUMBER ROOM. 



globe might be buried beneath the ocean ; for as the rivers 

 are perpetually engaged in wearing it down and carrying 

 it away, they would in time reduce the level of the land 

 everywhere to that of the sea, were it not for the compen- 

 sating earthquake force, which whether working suddenly 

 or gradually, acts on the whole in the opposite direction. 



Volcanoes also have their share in repairing the waste of 

 the earth's surface, and though the island of Krakatoa was 

 reduced by the great subsidence to less than a third of its 

 original area (twenty square miles) it has since been increased 

 more than three square miles by the addition of volcanic 

 matter. 



The amount ejected by Krakatoa was, however, small 

 compared with that thrown up or poured forth by many 

 other volcanoes. 



Most of the islands of the Pacific are of altogether 

 volcanic origin, hills and islands of volcanic matter have 

 frequently been raised to a height of several hundred feet in 

 the course of a few hours, and lava has been poured forth 

 in such voluminous streams as to form beds of vast extent 

 and many hundreds of feet in thickness. 



Whether the molten rock which we call lava has itself 

 been formed from something else and has previously existed 

 in a solid state, we have no means of knowing; but there are 

 evidently vast stores of it, for the space from beneath which 

 volcanic matter has been ejected by volcanoes in the 

 Cordillera alone measures 720 miles one way and 400 the 

 other, showing, as Mr. Darwin says, the existence of a sub- 

 terranean lake of lava nearly double the size of the Black 

 Sea. 



