366 THE WORLD OF LIFE CHAP. 



(H 2 O) 3 being ice, while liquid water is a mixture of these or 

 (H 2 0) 2 . 



Professor H. E. Armstrong put forward this view in 

 1908, and in the Address already quoted he says : 



" Although it is generally admitted that water is not a uniform 

 substance but a mixture of units of different degrees of molecular 

 complexity, the degree of complexity and the variety of forms is 

 probably under-estimated, and little or no attention has been paid 

 to the extent to which alterations produced by dissolving substances 

 in it may be the outcome and expression of changes in the water 

 itself." 



And again : 



" As water is altogether peculiar in its activity as a solvent, and is 

 a solvent which gives rise to conducting solutions, an explanation of 

 its efficiency must be sought in its own special and peculiar 

 properties." 



Here again we find that the most common and familiar 

 of the objects around us, and which we are accustomed to 

 look upon as the most simple, may yet really be full of 

 marvel and mystery. 



The strange chemical properties of water are probably 

 the cause of the singular but most important fact that 

 water reaches its greatest density at 4 C. ( = about 7 F.) 

 above the freezing-point. If this curious anomaly did not 

 exist the coldest water would always be at the bottom, and 

 would freeze there ; and thus many lakes and rivers during 

 a hard winter would become solid ice, which the succeeding 

 summer might not be able to melt. Sir Henry Roscoe 

 says : 



"If it were not for this apparently unimportant property our 

 climate would be perfectly Arctic, and Europe would in all 

 probability be as uninhabitable as Melville Island." 1 



The very remarkable and highly complex relations 

 between the quantity of water in our oceans, seas, and lakes, 

 and the earth's habitability have been fully discussed 

 in chapters xii. and xiii. of my volume on Man's Place 

 in the Universe. I will only mention here, that in those 

 chapters I have pointed out the probable origin of the great 



1 Elementary Chemistry, p. 38. 



