THEORTofRAIN. 67 



this place being no colder, in general, than any other in the 

 neighbouring atmofphere at the fame height. 



ACCORDING to this principle, there mould be more rain upon 

 the land than upon the fea, which, being a plane, and homo- 

 geneous in its nature, has neither the fame power to produce 

 ftreams of air, nor to mix together thofe which it may produce. 

 We find this alfo confident with experience. There is lefs rain, in 

 general, upon the fea than upon the land, fo far as we may 

 judge from all that we know. In the conftant trade-winds, 

 there is very little rain ; but, in the variable winds adjoining 

 to the trade-winds, rain falls in abundance, which is ftrictly 

 agreeable to the theory. So certain alfo is this general princi- 

 ple, that the mofl experienced feamen and beft obfervators have 

 made the remark, that, in thofe great oceans, the appearance of 

 a cloud at a diflance was an indication of an ifland, which they 

 feldom failed to find from that indication. 



THE fecond principle in the caufe of rain is the different 

 degrees of humidity that may happen to be in the ftreams of 

 air which are mixed. Here we mall alfo find a great fource of 

 variation as to the quantity of rain to be produced in equal cir- 

 cumftances, /'. e. with a perfect fimilarity in die other requifite 

 conditions. It is not, however, fo eafy to exemplify the reality 

 of this principle from actual obfervation, as it is with regard to 

 the other, which had been fo evident as to have been received 

 into a general opinion. We mall, therefore, be obliged to look 

 out for fome appearances, by which the theory may be confirm- 

 ed, in proving the two following general propofitions : 



ift, THAT the place where the greateft quantity of rain mould 

 fall, cceter'u paribus, is in the land contiguous to a great fea in a 

 tropical fituation. 



zdfy, THAT the place where the leaft quantity of rain fhould 

 fall upon the earth," ceeteris paribus, is the moft inland part of 

 the continent of Europe and Afia, in a cool or temperate lati- 

 tude. 



I 2 IP 



