THE OR T of R4IN. 79 



IT is found, that, in the tropical or equinoctial region, the 

 variation of the barometer is fmall, compared with that in the 

 temperate zone, notwithftanding there may be greater falls of 

 rain in the firfl than in the laft. But, if the power for evapo- 

 rating water, and of condenfing vapour, increafes in a higher 

 ratio than the equable progrefs of heat and cold, it muft ap- 

 pear, that, to produce the fame quantity of aqueous condenfa- 

 tion in a hot region, in which the atmofphere is faturated with 

 vapour, a fmaller quantity of the atmofphere, of different tem- 

 peratures, to be mixed for that purpofe, will be required ; and, 

 converfely, a greater quantity of the atmofpheric ftreams muft 

 concur for producing the fame quantity of rain in the temperate 

 regions, not equally faturated with vapour ; confequently, greater 

 temporary accumulations and local abftraclions of the atmo- 

 fphere, in the one region than in the other. Hence, a greater 

 rife and fall of the barometer, accompanying the changes of the 

 weather, in relation to rain and drought in the temperate than 

 in the tropical region. 



THUS, certain natural appearances, which are perfectly in- 

 confiftent with the levity of the atmofphere being the imme- 

 diate caufe of rain, find an eafy explanation in the prefent 

 theory, which requires the mixture of feveral portions of the 

 atmofphere in different temperatures of heat. We may now 

 proceed to confider the natural appearances which generally at- 

 tend rain in this ifland, with a view to recommend the theory, in 

 mowing that fuch mixtures actually take place. 



i. IF the mixing together of different ftreams of the atmo- 

 fphere be the caufe of rain, calmnefs, or fteady breezes, mould 

 be the attendants of fair weather ; but this, in general, is the 

 cafe. The converfe of this is alfo true ; for partial mowers ne- 

 ver happen without wind, although general rains, or fuch as 

 are produced in the higher regions of the atmofphere, may be 

 attended with a calm, or fall without difturbance, in the place 

 of our obfervation. Now, the truth of the propofition is mani- 



fefted 



