66 THE OCEAN 



heat and wobble heat. Such motions increase 

 with a rise of temperature and decrease with 

 a fall of temperature, but are distinct from 

 changes of temperature. Again, changes of 

 heat-content may condition changes of state of 

 aggregation, of molecular or intramolecular 

 complexity, etc., without necessarily affecting 

 the temperature. Temperature is not the same 

 thing as heat; it is not a quality of any 

 particular body, but may be defined as that 

 state or condition of matter on which depends 

 its relative readiness to give or to receive heat. 

 Water has a greater capacity for heat — a 

 higher specific heat — than any other liquid 

 or solid. The specific heat of water is thirty 

 times that of mercury, that is, the amount of 

 heat required to raise the temperature of 

 one pound of water through any interval of 

 temperature is thirty times as much as that 

 required to raise an equal mass of mercury 

 through the same interval of temperature. 

 The capacity of steam and ice for heat is 

 only one-half that of water in the liquid state. 

 For these reasons water is not warmed by 

 the sun's rays to nearly the same extent as the 

 land, nor does it cool so quickly when the 

 sun's rays are absent. Another marked 

 peculiarity of fresh water is that its maxi- 

 mum density point is at a temperature of 

 39-2° F. Above this temperature the volume 



