NATURAL WATERS V5 



The conversion of a liquid into a vapour is always attended 

 by an absorption of heat. Though the amount of heat required 

 to convert a gramme of the liquid into vapour varies with the 

 nature of the liquid, in no case is it so great as with water. 

 The following experiment furnishes a striking proof of this 

 heat absorption : 



A small, thin glass beaker is placed on a few drops of water 

 on a wooden block ; a little ether is placed in the beaker, and 

 by means of a tube and bellows a cuirent of air is blown into 

 the beaker so as to cause the ether to evaporate rapidly. In 

 being converted into vapour it absorbs heat from the beaker ; 

 this cools the water below, and in a short time the loss of heat 

 becomes so great that the water freezes, and the little beaker 

 is cemented to the block of wood by a thin film of ice. 



The high specific and latent heats of water lead to important 

 consequences in nature. The former explains the temperate 

 character of the climate of places near large masses of water. 

 Islands or places near the coasts of large areas of water have 

 much smaller ranges of temperature than places far inland. 



A wet soil is cold because of both these causes. The heat of 

 the sun shining on the soil can only warm it slightly, because 

 (1) of the high specific heat of the water present, and (2) a 

 large portion of the heat is absorbed by the evaporation of a 

 portion of the water. The magnitude of this second effect is 

 greatly increased if a wind be blowing, since the rate of 

 evaporation is thereby accelerated. 



