[ 479 ] 



portion of their eledron, and thus thefe are, at leaft in part, con- 

 verted into a cloud; but clouds being ftill better condudors of 

 eledricity, the cloud thus formed robs, in its turn, the portions of 

 air more ftrong'y eledrified of their eledron, and converts, at leaff 

 partially, their vapours into clouds; thus the dimenfions of the 

 original cloud is increafed until it covers a confiderable part of the 

 ho.izon. By this fudden nubification a confiderable quantity of 

 caloric is fet loofe, which rarefies the air, and thus occafions a 

 ftorm or erruption of air from all quarters, in a word, a hurricane. 



Section II. 

 Of Dew. 



In hot weather, particularly if the heat is long continued, as in 

 fummer and autumn, vapours are diflTolved and elevated to great 

 heights, but in the evening, particularly after fun-fet, when the 

 air is cooled, a portion of this vapour, proportioned to the refri- 

 geration, gradually defcends, until at laft the lower ftrata of air 

 become faturate and gradually depofit it on the contiguous 

 denfer fubftances. The moifture thus depofited forms what is 

 called dew. That there is likewife an afcending dew arifing from 

 the efiluvia of vegetables which emit air accompanied with moif- 

 turc, but depofit it on the inferior furfaces of more elevated 



3 O 2 fubftances, 



