THEORT of RAIN. 55 



would be found, in each hemifphere, a region of much tem- 

 perance, in relation to heat, but of much humidity in the at- 

 mofphere, perhaps of continual rain and condenfation. 



THE fuppofition now formed muft appear extremely unfit for 

 making this globe a habitable world, in every part ; but, ha- 

 ving thus feen the effect of night and day, in temperating the 

 extremities of heat and cold in every place, we are now pre- 

 pared to contemplate the effects of fuppofing this globe to re- 

 volve around the fun, with a certain inclination of its axis. By 

 this beautiful contrivance, that comparatively uninhabitable 

 globe is now divided into two hemifpheres, each of which is 

 thus provided with a fummer and a winter feafon. But our 

 prefent view is limited to the evaporation and condenfation of 

 humidity ; and, in this contrivance of the feafons, there muft 

 appear an ample provifion for thofe alternate operations in every 

 part y for, as the place of the vertical fun is moved alternately 

 from the one tropic to the other, heat and cold, the original 

 caufes of evaporation and condenfation muft be carried over all 

 the globe, producing either annual feafons of rain, or diurnal 

 feafons of condenfation and evaporation, or both thofe,. feafons, 

 more or lefs, that is, in fome degree. 



THE original caufe of motion in the atmofphere is the influ- 

 ence of the fun heating the furface of the earth, expofed to that 

 luminary. We have now fuppofed that furface to be of one 

 uniform fhape, and fimilar fubftance; from whence it has fol- 

 lowed, that the annual progrefs of the fun, perhaps alfo the di- 

 urnal progrefs, would produce a regular condenfation of rain 

 in certain regions, and the evaporation of humidity in others ; 

 and this would have a regular progrefs in certain determined 

 feafons, which would not vary. But nothing can be more di- 

 ftant from this fuppofition than is the natural conftitution of 

 the earth ; for the globe is compofed of fea and land, in no re- 

 gular fhape or mixture, while the furface of the land is alfo ir- 

 regular, with refpect to its elevations and depreffions, and vari- 



ous, 



