r 49S ] 



to ferenrty with the increafe of its weight. Becaufe under the 

 diminiflied weight of the atmofphere, the eruption of vapours 

 both from land and water is much more copious, a difpofition 

 highly favourable to nubification, and the clouds already formed 

 defcend lower, are more concentrated, and hence more difpofed 

 to readl upon and attrad each other and thus produce rain. The 

 increafed weight of the atmofphere muft produce oppofite effeds 

 and induce a difpofition adverfe to the prorludlion of rain. 



5®. That more rain falls on the furface of the earth than 

 on fmall elevations above it, as fron 30 to fome 100 feet: fee 

 Phil. Tranf. 1769, p. 361 ; andof 1771, 297; andof 1777, p. 256. 

 This.efFe(5l feems to me to proceed from the greater ftillnefs and 

 tranquillity of the air near the flifface of the earth than at greater 

 elevations. To prove this, it is only neceffaty to colleft the 

 rain that falls in moderate weather on both fituations, with that 

 which falls on both, in more ftormy weather. If this explana- 

 tion be juft the difference between the quantities coUeded in 

 both fituations will be found greater in the latter than in the 

 former cafe. This experiment I fhall make, and communicate 

 the refult to the Academy. 



C. That the quantities of rain coIle(fled at the top of high 

 mountains, and on plains about half a mile diftant from thofe 

 mountains are nearly equal, but in fummer there falls fomewhat 



Vol. VIII. 3 Ei more 



