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tain a greater quantity of moifture than rarer air, and in all cafes 

 air muft have, to admit vapour, liberty of expanfion ; for in veffels 

 full of air, and perfedly clofed and refifting dilatation, no m<ire va- 

 pour can rife but as much as faturates that air; and, confequently, 

 diflillation cannot take place, let ever fo much heat be applied, as 

 Fontana has iTiewn, 13 Roz. Journ. p. 22. 



Doctor Eason, in i Mem. Mancheft. p. 396, argues, that if 

 vapours were diffolved in air, the air that receives them would 

 have its weight increafed by the additional weight of the vapours ; 

 but it is known, that moift air is lighter than dry air. This is 

 certainly ,true, but then it is only fpecifically lighter than dry 

 air. And it is well known that many, even metallic, alloys, are 

 fpecifically lighter than either of their ingredients. Air receiving 

 vapours acquires a flill greater addition to its volume than it 

 does to its weight ; bcfidcs, vapour is lighter than air, not in- 

 deed 1800 times, for that is true only oi Jleam, (the vapour of 

 boiling water) not of common vapour, as De Luc himfelf now 

 allows. 



The Do£tor adds, that if the dodrine of folution were true, we 

 could not have rain unlefs the air were fuperfaturated with water, 

 which is true with refped to fome or other of ihe Jirata of the at- 

 mofphere, for rain proceeds from clouds, and clouds confift of 



vapours 



