PROCESS OF GASSIFICATION. 187 



DR. HAMILTON, of Dublin, concluded, "that 

 evaporation is nothing else than the gradual 

 solution of water in air, produced and promoted 

 by (what he calls) attraction, assisted by heat 

 and motion, in the same manner as other sub- 

 stances are affected." Dr. Halley supposed 

 small hollow spheres of water, to be filled with a 

 subtile elastic fluid, which made them naturally 

 lighter than air ; and that a chemical union took 

 place between both ; air dissolving water, as 

 water does salt. DESAGULIERS argues, that 

 water is capable of being converted, by heat, 

 into an elastic fluid, much lighter than air ; and 

 ARISTOTLE ascribes exhalation to the action of 

 fire. LE ROY, of Montpellier, also supposed 

 that, " air dissolved water, in the same manner 

 that water dissolved sugar ; as water, by being 

 heated, becomes able to dissolve a large quantity 

 of sugar, and of salt, and, by cooling, abandons 

 a part of what it had dissolved ; in like manner, 

 the air, as it became heated, or cooled, takes up 

 more or less water." In order to ascertain the 

 fact, he exposed, athis window, during the night, 

 a white glass phial, full of air, closely tied up, 

 at the temperature of 79. Fahr: the mercury 

 fell to 68. during the night, and, on examining 

 the contents of the bottle, in the morning, he 

 found that a part of the water contained in the 

 air had separated, and had been deposited in 

 the form of little drops, which adhered to the 



