105 



These variations are what make possible both 

 the evaporation of water and its precipitation 

 as rain and as dew in the meteorological cycle. 

 And therefore the high latent heat of vapori- 

 zation of water is in still another manner a 

 most favorable circumstance in its effect upon 

 the organisms. 



To sum up, this property appears to possess 

 a threefold importance. First, it operates 

 powerfully to equalize and to moderate the 

 temperature of the earth; secondly, it makes 

 possible very effective regulation of the tem- 

 perature of the living organism; and thirdly, 

 it favors the meteorological cycle. All of 

 these effects are true maxima, for no other 

 substance can in this respect compare with 

 water. 1 



1 This conclusion may be contrasted with that of Whewell 

 (Bridgewater Treatise, p. 142). He includes the expansion of 

 water by heat, the expansion of water by cold below 40°, the 

 expansion of wate. in freezing, the latent heats of melting and 



