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4o. ScHMiDT alfo obferved a peculiarity in the expanfion of 

 moill air, previoufly noticed by Roy, for Schmidt found that the 

 expanfibihty of air, faturated with moifture, was fmaller than the 

 expanfibility of pure vapour, until the 167th degree of Fahr. 

 but in higher degrees they conftantly approached nearer to each 

 other. And the General obferved that the mean rate of expanfion, 

 which from 152*^ to 172" of Fahr. was 12 for each degree, did 

 from the 172^ to the 192° increafe to 17,88 for each degree, and 

 increafed ftill more after the 19 2d to the boiling point. The 

 fluggifhnefs of expanfion of air, faturated with moifture at about 

 32°, was alfo noticed by the General, and he hence concludes the 

 mean rate of expanfion from o to 32° of Fahr. to be 2,27 for 

 each degree, which is fmaller than that of drier air. 



These variations of the rates of expanfibility of moift air, fa- 

 turated at different temperatures, Schmidt very juftly attributes 

 to the variation of the degrees of affinity or adherence of air and 

 vapour to each other at different temperatures. At 32*^ Fahr. it 

 is very ftrong, and alfo below that degree ; and hence the ftrong 

 folvent power of ai."-, colder than the water it ads upon, remarked 

 by Richman ; but if both are equally cold very little moifture 

 v.'ill be taken up by the air, as already mentioned; and hence I 

 have faid that air diffolves vapour when this is in a nafcent ftate. 



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