214 5TATJC OF VAPOUR SUBSISTING IN THE ATMOSPHERE 



Remarks. Note. — 1. Hence we fee that air faturated with moifturp 



Air faturated a t high heats is much more expanded than dry air of the fame 



with moifturc r j , 



expands more temperature, as De Luc and General Roy have alfo obferved. 

 than dry air. but in temperatures below 36°,5 dry air is more dilatable 

 which probably induced SaufTure to conclude it was fo at 

 higher temperatures. At 54,5 the difference is very percep- 

 tible for J 000 parts dry air at 32° are expanded at 54°,5 that 

 is by 22°,5 above the freezing point to 1044,67, whereas 

 1000 parts of air faturated with moifture, are extended to 

 1064,72 and in higher heats, the differences of expanfion are 

 incomparably greater. 

 Moift air more 2. Hence it is plain why moift air, fuch as that of the Weft 

 u oca mg Indies is much more fuffocating than dry air of the fame tem- 



perature. For 1000 cubic inches of air faturated with moif. 

 ture at 869 of Fahr. contain nearly 76 inches of moifture 

 which is ufelefs to refpiration. 

 Gen. Roy's 3. Thefe experiments agree with thofe of general Roy, in 



experiments. wn ich fleam was introduced at hazard, for the general found 

 that from 32° to 52° each degree gave at a mean 2,588, and 

 eonfequently thefe 20° would expand 1000 inches to 1051,76, 

 and by Schmidt's experiments much more accurately made, 

 we have 1050,33. 

 Irr-gularity of 4. Schmidt alfo obferved a peculiarity in the expanfion of 

 the expansions mo ift a jr, previoufly noticed by Roy, for Schmidt found that 

 9 the expanfibility of air, faturated with moifture, was fmaller 

 than the expanfibility of pure vapour, until the 167th degree 

 of Fahr. but in higher degrees they confiantly 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 increaled ftill more after the 192d 

 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 to 32° of Fahr. to be 2,27 for each degree, which is 

 fmaller than that of drier air. 



meant to exprefs the dilatations of air faturated at any particular 

 degree of heat it would acquire at other fuperior degrees, but only 

 the bulk that 1000 parts dry air at 32° would acquire by faturation 

 at each higher degree. 



Thefe, 



