560 HISTORY OF THERMOTICS. 



being small, are easily affected by this force, and 

 thus become lighter than the atmosphere. 



Muschenbroek still adhered to the theory of 

 globules, as the explanation of evaporation ; but he 

 was manifestly discontented with it; and reason- 

 ably apprehended that the pressure of the air would 

 destroy the frail texture of these bubbles. He 

 called to his aid a rotation of the globules ; (which 

 Descartes also had assumed;) and, not satisfied 

 with this, threw himself on electrical action as a 

 reserve. Electricity, indeed, was now in favour, as 

 hydrostatics had been before ; and was naturally 

 called in, in all cases of difficulty. Desaguliers, 

 also, uses this agent to account for the ascent of 

 vapour, introducing it into a kind of sexual system 

 of clouds ; according to him, the male fire (heat) 

 does a part, and the female fire (electricity) per- 

 forms the rest. These are speculations of small 

 merit and no value. 



In the mean time, Chemistry made great pro- 

 gress in the estimation of philosophers, and had its 

 turn in the explanation of the important facts of 

 evaporation. Bouillet who, in 1742, placed the 

 particles of water in the interstices of those of air, 

 may be considered as approaching to the chemical 

 theory. In 1743, the Academy of Sciences of Bour- 

 deaux proposed the ascent of vapours as the sub- 

 ject of a prize ; which was adjudged in a manner 

 very impartial as to the choice of a theory ; for it 

 was divided between Kratzenstein, who advocated 



