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lime, be, after fome days, carefully introduced under the fame 

 receiver, all the moifture will, after a few days, be extraded by 

 them, let the receiver be ever fo tall, as I myfelf and others have 

 frequently experiencedj which could not happen if thefe fubflances 

 were not in contad with the vapours, which are perpetually 

 drawn down by the attradion of the lower portions of air as faft 

 as they are deficcated, and thus the contad perpetually kept up. 

 Moreover, cold is known to be produced in air by evaporation, 

 but cold is never produced by mixture, but it often is by folution. 

 Many other arguments might be adduced in proof of the folution 

 of vapours in air, but thefe appear to me fufficiently convincing. 

 See alfo Schmidt's excellent treatife on vapours in 4 Gren's Jour. 



Yet it muft be remarked, that though air favours the rife of 

 vapour by its affinity, yet it oppofes its formation by its preiTure, 

 and, confequently, does not contribute to its origin, but only re- 

 ceives it in its nafcent ftate, and difperfes it through its own 

 volume, and enables it to fupport a degree of cold, greater than 

 it could bear if fingle ; and as its prefTure is proportioned to its 

 denfity, denfe air oppofes evaporation more than rarefied air does, 

 as already feen. 



But denfe air requires a greater quantity of vapour to faturate 



it than rarefied air, and, therefore, in equal volumes it may con- 



VoL.VIII. N n - tain 



