214 THE PHYSICAL GEOGRAPHY OF THE SEA. 



paring the ingredients for the fruitful soil of a land that some 

 earthquake or upheaval, in ages far away in the future, may be 

 sent to cast up from the bottom of the sea for man's use. 



The study of these "sunless treasures," recovered with so much 

 ingenuity from the rich bottom of the sea, suggests new views 

 concerning the physical economy of the ocean. 



457. In the chapter on the Salts of the Sea, p. 150, I endeav- 

 ored to show how sea-shells and marine insects may, by reason 

 of the offices which they perform, be regarded as compensations 

 in that exquisite system of physical machinery by which the har- 

 monies of nature are preserved. 



But the treasures of the lead and revelations of the microscope 

 present the insects of the sea in a new and still more striking light. 

 We behold them now serving not only as compensations by w^hich 

 the motions of the water in its channels of circulation are regu- 

 lated and climates softened, but acting also as checks and bal- 

 ances by which the equipoise between the solid and the fluid 

 matter of the earth is preserved. 



Should it be established that these microscopic creatures live 

 at the surface, and are only buried at the bottom of the sea, we 

 may then view them as conservators of the ocean ; for, in the of- 

 fices which they perform, they assist to preserve its status by 

 maintaining the purity of its waters. 



It is admitted (^ 343) that the salts of the sea come from the 

 land, and that they consist of the soluble matter which the rains 

 wash out from the fields, and w^hich the rivers bring dow^n to the 

 sea. 



The waters of the Mississippi and the Amazon, together with 

 all the streams and rivers of the world, both great and small, hold 

 in solution large quantities of lime, soda, iron, and other matter. 

 They discharge annually into the sea an amount of this soluble 

 matter which, if precipitated and collected into one solid mass, 

 w^ould no doubt surprise and astonish the boldest speculator with 

 its magnitude. 



458. This soluble matter can not be evaporated. Once in the 

 ocean, there it must remain ; and as the rivers are continually 

 pouring in fresh supplies of it, the sea, it has been argued, must 

 continue to become more and more salt. 



Now the rivers convey to the sea this solid matter mixed with 



