58 THE EARTH. 



that process, would still remain there as a gas, and the effect 

 of this superabundance would be to saturate all the water 

 covering the earth with it ; this solution of carbonic acid, 

 being capable of dissolving lime, would (as it percolated and 

 rushed in currents through the rocks and inequalities of the 

 surface) become converted into a solution of percarbonate 

 of lime, taking up a large quantity of this earth from the 

 broken-up granite, &c., then this carbonate of lime would 

 be deposited at the bottom of the water in one of two ways 

 either from pressure, diminution of carbonic acid in the 

 air, and heat of the surface, it crystallised at the bottom in 

 the form of marble (that the water does thus become satu- 

 rated with carbonic acid and take up lime, is constantly 

 shown by the stalagmites which form on the floors of 

 caverns, where the water thus loaded with percarbonate of 

 lime, evaporating, deposits gradually the carbonate in all 

 sorts of fantastic shapes, as in fig. 9), or the myriads of 



PIG. 9. STALAGMITE. FIG. 10. TEEEBEATTJLA. 



crinoidians and brachiopodous molluscs (fig. 10) which 

 were about this time created, absorbed it into their 

 systems and at their death deposited their shells, which 

 are made of this earth, at the bottom of the sea; these 

 shells, accumulating through ages into strata, became 

 hardened and partly crystallised by heat, thus forming 

 the limestones, which were the first containing carbonate 

 of lime. That such a collection, from such caiises, is 



