WATER 93 



the high latent heals 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 heal cannol lower il> 

 temperature below that point, which, to be 

 sure, is somewdiat variable in the case of sail 

 water. And so long as water and ice exi>t 

 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 tem- 

 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. 



