•^58 On the Proportion of, &V. 



which case they become one gas) I cannot see 

 why rarefaction should either decrease or in- 

 crease this supposed afhnity. I have little 

 doubt, however, as to the fact of oxygenous 

 gas observing a diminishing ratio in ascending ; 

 for, the atmospheres being independent on 

 each other, their densities at different heights 

 must be regulated by their specific gravities. — 

 Hence, if we take the azotic atmosphere as a 

 standard, the oxygenous and the carbonic acid 

 will observe a decreasing ratio to it in ascend- 

 ing, and the aqueous vapour an increasing one, 

 The specific gravity of oxygenous and azotic 

 ga^es being as 7 to 6 nearly, their diminution 

 in density will be the same at heights recipro- 

 cally as their specific gravities. Hence it would 

 be found, that at the height of Mount Blanc 

 (nearly three English miles) the ratio of oxy- 

 genous gas to azotic in a given volume of air, 

 would be nearly as 20 to 80 ; — consequently it 

 follows that at any ordinary heights the dif- 

 ference in the proportions will be scarcely if 

 at all perceptible.* 



* Air brought from the summit of Hejvelyn, in Cum- 

 berland (1100 >ards above the sea — Barometer being 

 26,60) in July 1804, gave no perceptible difference from 

 the air taken in Manchester. — IVI. Gny-Lussac deler- 

 niines the constitution of air brought from an elevation 

 of four miles to be ihe same as that at the eailh's surface* 



