Ofi the Production of Vapor. 71 



with v^ital air, and generates water. But, from the cir- 

 cumstances under which hydrogen gas is produced, it 

 can by no means be supposed to exist in so hirge quan- 

 tities, as to generate the abundant vapor that exists. 

 Large quantities of vapor daily ascend from the surface 

 of rivers, ponds, lakes, and seas. Doct. Halley found,^ 

 that in the summer season, there arises in vapor at a 

 medium, daily, from every square foot of the surface of 

 water half a pint, from every square mile 6914 tons, and 

 from the Mediterranean sea 5,280,000,000 tons. This 

 prodigious quantity of water is not changed into air. 

 Nature affords no re-agent to decompose it. The con- 

 version of water into air, and air into water, appears 

 therefore not to be the grand process of nature, by which 

 clouds are formed, and precipitated in rain. Though 

 by the elimination of hydrogen gas, and its combination 

 with pure air, a small quantity of vapor may be generat- 

 ed, we are to look somewhere else for the principal 

 cause of the production of vapor. 



To make water ascend in vapor, it seems necessary 

 that some alteration in its texture should take place, that 

 should render it so porous as to be specifically lighter 

 than air. The alteration in the texture of bodies, is ei- 

 ther under such circumstances, that theu' very constitu- 

 tion and nature is changed ; in which case the attraction 

 between the two bodies that unite, is strong, and they 

 undergo a chymical combination ; or the body, whose 

 texture is altered, retains all its former properties ; and 

 pretty readily quits the substance it is united with. The 

 attraction here is weak, and the process is termed by 

 ohymisX.^ solution. Solution is the disappearance of a' 

 solid in a liquid ; or it is the change of a solid to a liquid^ 

 or to gas, without any alteration in the nature of the body 

 dissolved. Water and lire are the great solvents or men-, 

 strua that nature furnishes. Corpuscular attraction, or* 

 what the chymists term affinity, is commonly said ta 

 take place between the integrant parts of bodies, when 

 in contact only ; but this is not strictly true. The con- 

 stituent particles of bodies attract each other, when at 

 a small distance ; though that distance may be so small 

 as to be insensible. The nearer the integrant parts of a 



