WATER 93 



the high latent heats of fusion and evapora- 

 tion of water upon the meteorological pro- 

 cesses. When, for example, a body of water 

 becomes cooled to its freezing point, the 

 further abstraction of heat cannot lower its 

 temperature below that point, which, to be 

 sure, is somewhat variable in the case of salt 

 water. And so long as water and ice exist 

 in contact, the system constitutes a ther- 

 mostat, a very accurate one if the water be 

 fresh, which changes only in respect to the 

 quantities of ice and water as heat is added or 

 removed. 1 Heating serves merely to melt 

 the ice, cooling to freeze the water. Accord- 

 ingly, as long as the earth shall remain habit- 

 able the cooling of its oceans and seas will 

 remain rigidly limited by their freezing point. 

 However inclement the atmosphere, the ocean 

 can always support life until the final extinc- 

 tion of water by cold. It is worthy of note 

 that the freezing point of water, though to- 

 man with his carefully regulated body tein- 

 perature apparently low, is in reality very 

 high indeed compared with that of any like 

 substances, — perhaps 100° centigrade above 

 the average. 



1 In fact, there is no better means of obtaining a constant 

 temperature in the chemical laboratory than by mixing pure 

 ice with pure water. 



