112 On the Theory of mixed Gases. 



tie, having a dew left slicking to the sides of it, was placed 

 in water at the temperature of 126 degrees: the mouth, 

 which remained about an inch above the surface, was co- 

 vered with my hand, care being taken to remove it fre- 

 quently for an instant to permit the vapour and expanding 

 air to escape. After keeping it in this situation about two 

 minutes, I secured the mouth in the manner described above, 

 and inverted it in a quantity of the same water, where it 

 was reduced to 59 degrees ; in consequence of which it took 

 up IC22 grains of water, leaving a space equivalent to 6172 

 grains. If the experiment be now inverted, 6172 parts of 

 air will occupy the space of 7794 such parts when its tem- 

 perature is raised from 59 to 126 degrees; which is nearly 

 double the expansion of dry air in like circumstances. For, 

 according to Mr. Schmidt's experiments, 1000 parts of dry 

 air of 59 degrees will become equal to 1 133*03 such parts, 

 by being heated to 126 degrees; therefore, by the rule of 

 proportion, if 1000 parts give an expansion of 1 1 33*03 such 

 parts, 6172 parts give only 820: but the difference of 7704 

 and 6172 is 1(322, which is nearly the double of 820. The 

 preceding experiment, and others which I have made of the 

 same kind, demonstrate that moist air expands more than 

 dry air under like circumstances, and the fact subverts the 

 notion of uncombined elastic vapour mixing with the atmo- 

 sphere. The accuracy of the fact may be disputed ; the 

 doubt, however, is removed by repeating the experiment : 

 but so long as my statement remains uncontradicted, the 

 consequences of it to the theory in question cannot be con- 

 troverted by argument : for if elastic vapour mix with the 

 air, it does more than merely enter the pores of this fluid ; 

 for, according to my experiment, it enlarges these pores at 

 low temperatures, which we know to be impossible, unless 

 the heat of the compound arises to 212 degrees. Those who 

 are convinced of the superior expansion of moist air, will 

 readily apply the principle to certain interesting phajnomena, 

 n\ particular to the origin of tornadoes in hot countries, and 

 the variation of the barometer in temperate climates. 



Mr. Barrow, an intelligent traveller in South Africa, ob- 

 serve?, that the atmo.-ph'jre in Caffraria is sametimes heated 



to 



