ABOUT VOLCANOS AND EARTHQUAKES. II 



the earth. Every mile tlnck is such a greatcoat, and at 

 20 miles depth, according to this rate, the ground must 

 be fully red-hot; and at no such very great depth beyond, 

 either the whole must be melted, or only the most in- 

 fusible and intractable kinds of material, such as our fire- 

 clays and flints, would present some degree of solidity. 



(16.) In short, what the icefloes and icebergs are to 

 the polar seas, so we shall come to regard our continents 

 and mountain-ranges in relation to the ocean of melted 

 matter beneath. I do not mean to say there is no solid 

 central mass ; there may be one, or there may not, and, 

 upon the whole, I think it likely enough that there is 

 kept solid, in spite of the heat, by the enormous pres- 

 sure ; but that has nothing to do with my present argu- 

 ment. All that I contend for is this, Grant me a sea 

 of liquid fire, on which we are all floating,- land and 

 sea; for the bottom of the sea, anyhow, will not come 

 nearly down to the lava level. The sea is probably 

 nowhere more than five or six miles deep, which is far 

 enough above that level to keep its bed from becoming 

 red-hot. 



(17.) Well, now, the land is perpetually wearing down, 

 and the materials being carried out to sea. The coat 

 of heavier matter is thinning off" towards the land, and 

 thickening over all the bed of the sea. What must 

 happen 1 If a ship float even on her keel, transfer 

 weight from the starboard to the larboard side, will she 

 continue to float even 1 No, certainly. She will heel 

 over to larboard. Many a good ship has gone to the 

 bottom in this way. If the continents be lightened, 



