UNION OF AIR AND VAPOUR. 187 



edges as well defined as if they were terrestrial 

 solids, and even an entire covering, that extends 

 over the whole visible heavens, and shadows the 

 earth to very deep gloom, while yet that these 

 formations ride buoyant on the air, and some of 

 them are indications of dry weather. 



Thus though the air is the passage of the 

 ascending water, which is to maintain the springs, 

 it is no more the cause of the ascent than the 

 channel of a river is the cause why the tide of that 

 river flows downwards, and the vapour, whether 

 it be invisible or in clouds, is obeying the laws of 

 its own nature, and in no wise under the controul 

 of or attracted by the air. Were there an attrac- 

 tion, and if the air and the water actually united 

 in their ultimate particles, and formed a new sub- 

 stance, as an acid and an alkali do in the forma- 

 tion of a salt, we should soon, from the vast extent 

 of surface at which they constantly meet each 

 other, (which may be said to be, considering how 

 many moist substances stand surrounded by the 

 air, and how often the face of the water is wrinkled 

 with waves, equal to that of the whole globe) if 

 they acted chemically upon each other, we should 

 very soon have neither air nor water ; but a com- 

 pound of the two : differing as much in its pro- 

 perties from either as the neutral salt does from 

 the acid and the alkali. Common salt, which 

 renders our food so savoury and so wholesome, is 

 a compound of chlorine and hydrogen and soda, 

 each of which is a poison, and when perfectly 

 pure a very deadly one, nor are we acquainted 

 with any real chemical combination, in which the 

 properties of all the ingredients are not suspended 

 and new ones produced, while the combination 



