• P RAIN. 121 



confequence of the attraction of clouds is their incorporation, 

 and the refult of their incorporation is the increafed volume of 

 their conftituent particles, an increafe proportioned to the at- 

 traction that produced it; the increafed volumes, thus pro- 

 duced, form thofe drops whofe collection we call rain. The 

 weight of thefe being fuperior to the refiftance of air, they 

 neceflarily defcend, and the caufe of their different fize is thus 

 clearly difcerned. 



The repulfion of clouds fimilarly electrified, and not greatly Developemcnt of 

 differing in magnitude, terminates in a bare increafe of dif- ** effe " s * 

 tance ; but, if their magnitudes be much difproportioned, it 

 may terminate in attraction, or at leaft in forcing the confti- 

 tuent particles into clofer contact, and thus by increafing their 

 magnitude effect the fame refult. 



When the attraction takes place between clouds differently 

 and highly electrified, and within what electricians call the 

 ftriking dijlance, the electric fluid is fet free, the coalefcence of 

 the nubiious particles is more rapid and complete, and hence 

 the large drops that follow flafhes of lightning, or even floods, 

 where the quantities both of vapour and electron are confider- 

 able, as between the tropics. 



Upon thefe principles moft of the phenomena relative to rain 

 appear to me eafily explicable ; of thefe the moft remarkable 

 are : 



1. That rains are more copious but lefs frequent in the Phenomonaof 



fouthern parts of our hemifphere not much elevated over the rain# 



fea, than in the more northern latitudes. They are more co- More copious but 



pious when their productive caufes occui?, evidently becaufe lefs fre< jue n tin 

 , i, " - » - , . . , . , , low latitudes, 



the quantity of lufpended vapour is much greater in the hotter 



than in the colder regions ; but they are lefs frequent, becaufe 

 the variations of wind in different directions which introduce 

 and intermix clouds indifferently electrified are lefs frequent ; 

 this might be proved by inftancing the rainy feafons between 

 the tropics, were it not that this illuftration would extend this 

 paper to too great a length. Even in moderately elevated 

 iituations between the tropics, if infulated and of fmall extent 

 as the ifland of St. Helena, it feldom rains. 



2. That, in the temperate latitudes, rains are alfo more Moft copious 

 copious, though commonly lefs frequent, in fummer than in thou 8. *" ft f ™* 

 winter, for the reafons already afjigned. Dry fummers are 

 then the confequence of uniform winds, from whatever quar- 

 ter 



