.TEMPERATURE OF THE OCEAN. 399 



the coldest particles being at the bottom, and 

 the warmest at or near the surface. There is, 

 however, a remarkable apparent exception to 

 this rule, at a particular degree of heat, to 

 which allusion will be immediately made. In 

 the ocean, then, in these regions, the more 

 deeply we can penetrate, the colder will the 

 temperature of the water we obtain become. 

 The fact of the coldness of the inferior beds 

 of water was singularly illustrated by Messrs. 

 Kotzebue and Dupetit Thouars. Water was 

 procured by them from the abyss of the ocean, 

 in the tropics, and found to be at the unusually 

 low temperature of 35, or only three degrees 

 above freezing point ! This, too, under the 

 full influence of a tropical sun ! This most 

 curious discovery led philosophers to conceive 

 the existence of inferior polar currents of water 

 proceeding from the poles to the equator, just 

 on the principle of the trade -winds. 



Kotzebue and Sir James Ross have esta- 

 blished the fact, that there is a depth in the 

 ocean at which the water has a constant tem- 

 perature of about 39 5'. This depth depends 

 on the latitude. At the equator the stratum 

 of invariable temperature was as low as 7,200 

 feet, from thence it gradually rises till it comes 

 to the surface in S. lat. 56 26', where the water 

 has the temperature of 39 5' at all depths ; 



