,314 Qn the T^jy of Jjflved ^ase^, 



of 7794,aifVa6JL72is ; 622, wbiolji; is nearly the 

 double of .^2^. The preceding. experimeat, 

 and others which I have made of the same 

 kind, demonstrate ih^i moist air expands more 

 than dry , air under lik-e circumstances, and the 

 fact subverts the ngtion of unconabiped elastic 

 vapour mixing with Ae atmosphere. The 

 accuracy of the fact may be disputed; the 

 doubt however is reoaoved by, repeating the 

 experiment: but so long as my statement re- 

 mains uncontradicted, the consequences of it 

 Xo the theory in question cannot he controverted 

 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 expe- 

 riment, it enlarges these pores at low tempera- 

 tures which we know to be impossible^ unless 

 the heat^.ofthe compound arises to 21i? degrees. 

 Those who are convinced of the superior ex- 

 pa^sioi) of moist air, will readily apply the 

 principle to certain interesting phenomena, in 

 particular to the origiu of Tornadoes in hot 

 countries, and the variation of the barometer 

 in temperate clirpates. 



Mr. Barrow, an , intelligent traveller in 

 South Africa observes, that the atrnosphere in 

 Caffraria is sometime^, heated to ;1 02 or ipjt 

 degrees: this is suf corded by local thunder- 

 stprms, attended wi)thi heavy fa4l3 x}£ r^ia fji:«i 



