S 6 THEO RT of RAIN. 



ous, with regard to the humidity and drynefs of that furface 

 which is expofed to heat as the caufe of evaporation. Hence a 

 fource of the moft variable motions in the fluid atmofphere, 

 always affected with the heat of each particular part of the fur- 

 face with which it comes in contact ; hence a tendency to fatu- 

 rate every part of the atmofphere with aqueous vapour, more 

 or lefs, fo far as other natural operations will admit ; and hence 

 a fource of the moft irregular commixture of the feveral parts 

 of this elaftic fluid, whether faturated or not with aqueous 

 vapour. 



ACCORDING to the theory, nothing is required for the pro- 

 duction of rain befides the mixture of portions of the atmo- 

 fphere, fufficiently faturated with humidity, and in different de- 

 grees of heat. But we have feen the caufes of faturating every 

 portion of the atmofphere with humidity, and of mixing the 

 parts that are in different degrees of heat. Confequently, over all 

 the furface of the globe, there fliould happen occasionally rain 

 and evaporation, more or lefs j and alfo, in every place, thofe 

 viciffitudes fhould be obferved to take place, with fome ten- 

 dency to regularity, which, however, may be fo difturbed as 

 to be hardly diftinguifliable upon many occaiions. Variable 

 winds, and variable rains, fliould be found in proportion as 

 each place is fituated in an irregular mixture of land and wa- 

 ter ; whereas regular winds fhould be found in proportion to 

 the uniformity of the furface ; and regular rains, in proportion 

 to the regular changes of thofe winds, by which the mixture 

 of the atmofphere neceffary to rain may be produced. But, as 

 it will be acknowledged, that this is the cafe in almofl all this 

 earth, where rain appears according to the conditions here fpe- 

 -cified, the theory is thus found to be in conformity with na- 

 ture, .and natural appearances are thus explained by the theory. 



2. Of 



