398 THE CHEMISTRY OF CREATION. 



the latter at the depth of 300 fathoms amounted 

 in summer to from 26 to 30 ; the temperature 

 of this zone was 55, while that of the upper 

 zone ranged from 76 to 84 , during eight 

 months in the year. It is highly interesting 

 to find that the inhabitants of the deep are 

 thus carefully accommodated and distributed, 

 far out of sight of man, as is the case with 

 the vegetable and zoological dwellers on the 

 surface of the earth. 



The warmest part of the ocean is, in tem- 

 perate and tropical regions, at its surface, and 

 it is in its usual and mean condition somewhat 

 warmer than the bed of air immediately resting 

 upon it. This is the result of a very simple law 

 connected with what is termed convection (or 

 carrying) of heat in fluids. The warmer parti- 

 cles of water, expanded by heat, become lighter 

 than the surrounding particles of colder water ? 

 and consequently rise of the surface ; while the 

 cold particles sink, until they meet with a stra- 

 tum of water of similar temperature and density 

 to their own. It is thus that the fluid particles 

 convey or carry heat In the conduction of heat 

 there is no movement of the particles of a sub- 

 stance, but heat flies from particle to particle. 

 In the case of fluids, heat is actually carried by 

 the particles from one position to another, and 

 is thus very slowly diffused throughout a liquid ; 



