THE AQUOSITY OF WATER 393 



assuredly have the chemical compounds which are present 

 in protoplasm but men of science have not found it to 

 help them in investigating the mechanism of those pro- 

 perties to ascribe them to mystical intangible "principles" 

 differing from the agencies at work in other less excep- 

 tional substances. 



Thus, for instance, water, though a very common and 

 abundant chemical compound formed by the union of two 

 chemical elements, hydrogen and oxygen, which, at the 

 temperature and pressure of the earth's surface, are 

 gaseous, offers many strange properties to our considera- 

 tion not shared by other compounds of gaseous elements. 

 For instance, hydrogen, when it combines with gaseous 

 elements other than oxygen, does not form a compound 

 which is liquid at the temperature and pressure of the earth's 

 surface. Its combinations with nitrogen, with chlorine, 

 with fluorine, and even with the solid element carbon, are 

 under those conditions gaseous. What a special character, 

 therefore, has water ! Moreover, water, though a liquid, 

 yet behaves in a most peculiar way when either cooled 

 below ordinary temperatures or heated above them. It 

 becomes solid when cooled, but expands at the same time, 

 so that it is less dense when solid that when liquid a 

 most unusual proceeding ! And when heated it is con- 

 verted into vapour, but with a loss or " making latent " of 

 heat, which, like its behaviour when solidifying, indicates 

 that water is endowed with a very peculiar structure or 

 mechanism in the putting together of its molecules. We 

 might call these combined peculiarities of water 

 "aquosity," and as we certainly cannot say why water 

 should possess the lot of them, whilst other compounds of 

 cither hydrogen or of oxygen, or, in fact, of any other 

 elements, do not possess this combination, we might say 

 that their presence is due to " the aqueous principle/' or 

 " aquosity," which enters into water when it is formed, 



