CURRENTS OF THE SEA. 161 



under current from tlie Mediterranean as they were in favor of tlie 

 existence of Leverrier's planet before it was seen througii the tele- 

 scope at Berlin. 



438. Now suppose, as Su' Charles Lyell maintains, that none 

 of these vast quantities of salt which this surface current takes 

 into the Mediterranean find their way out again. It would not 

 be difficult to show, even to the satisfaction of that eminent geol- 

 ogist, that this indraught conveys salt away from the Atlantic 

 faster than all the fresh-wsitQx rivers empty fresh supplies of salt 

 into the ocean. Now, besides this drain, vast quantities of salts 

 are extracted from sea water for madrepores, coral reefs, shell 

 banks, and marl beds ; and by such reasoning as this, which is 

 perfectly sound and good, we establish the existence of this under 

 current-, or else we are forced to the very unphilosophical conclu- 

 sion that the sea must be losing its salts, and becoming less and 

 less briny. 



439. The Cueeents of the Indian Ocean. — ^By carefully 

 examining the physical features of this sea (Plates VIII. and IX.), 

 and studying its conditions, we are led to look for warm currents 

 that have their genesis in this ocean, and that carry from it vol- 

 umes of overheated water, probably exceeding in quantity many 

 times that which is discharged by the Gulf Stream from its fount- 

 ains (Plate VI.). 



440. The Atlantic Ocean is open at the north, but tropical 

 countries bound the Indian Ocean in that direction. The waters 

 of this ocean are hotter than those of the Caribbean Sea, and the 

 evaporating force there (§210) is much greater. That it is greater 

 we might, without observation, infer from the fact of a higher 

 temperature and a greater amount of precipitation on the neigh- 

 boring shores (§ 202). These two facts, taken together, tend, it 

 would seem, to show that large currents of warm water have their 

 genesis in the Indian Ocean. One of them is the weU-known 

 Mozambique current, called at the Cape of Good Hope the La- 

 gullas current. 



441. Another of these currents makes its escape through the 

 Straits of Malacca, and, being joined by other warm streams from 

 the Java and China Seas, flows out into the Pacific, like another 



L 



