412 THE CHEMISTRY OF CREATION. 



different in respect to their temperature, but 

 also in the quantity of salt which they contain ; 

 from which it appears, that while the quantity 

 of water carried away from the tropical sea, by 

 evaporation, is greater than that which rain and 

 the rivers give back to that sea, the reverse 

 takes place in the polar seas, where evaporation 

 is very small, and the condensation of vapour 

 very great. The circulation must on that ac- 

 count be such, that a part of the vapour which 

 rises in tropical zones will be condensed in 

 polar regions, and in the form of polar currents 

 flow back again to warmer climates. Although 

 my analyses are only made in water from the 

 ocean between Europe and America, yet little 

 doubt can be entertained that that part of the 

 ocean which separates America from Asia is 

 constituted in a similar manner; and that cur- 

 rents flowing from the poles are the rule, and 

 currents flowing towards the poles are the 

 exception." 



The chief cause of these variations in the 

 total quantities of saline matter present in the 

 water of different seas, are 1st, the influence 

 of evaporation, which concentrates the fluid by 

 removing a portion of its watery particles ; and 

 2nd, the influx of fresh- water from the land, or 

 from the atmosphere. In consequence of its 

 saline contents, sea-water is more dense and 

 heavy than fresh-water. This is occasionally 



