THE WORK OF THE RIVERS. 125 



This at first sight appears remarkable, for it will be 

 remembered that carbonate of lime, of which this analysis 

 shows so small a proportion, is the mineral carried down in 

 the largest quantities, at least, by the European rivers*; and 

 that the chlorides, though they seldom fail altogether in any 

 river or stream, are yet conveyed in comparatively minute 

 quantities, except by a few small rivers which are especially 

 rich in them. 



The sun, when he drinks, takes pure water, leaving salt, 

 lime, and all else, behind in the ocean ; what then becomes 

 of the enormous quantity of carbonate of lime which the 

 Rhine, Rhone, Loire, and Thames, to mention no others, 

 are continually pouring into it ? 



It is in the ocean still, but it has changed its form; 

 or rather has again acquired a form and has once more 

 become visible. 



The rivers gather materials from all parts of the earth, 

 and their work is not for nothing ; they cater on land for 

 the inhabitants of the sea, and what they pour in is all wanted 

 there, and the reason why there is so little dissolved lime in 

 sea-water is that it is required for so many purposes. 



Where, for instance, would the oyster get the material 

 for its shells, if the rivers did not supply its need ; for, 

 being rooted to its bed, all it wants must be brought within 

 its reach ? Moreover, the lime must be dissolved before it 

 can be used ; the oyster would not be able to make anything 

 of a lump of chalk or limestone ; for, like all other shell- 

 covered mollusks, it has to swallow the materials of which 

 its habitation is made. These are secreted by a sort of 



* Chap. IV. 



