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some chemical process, this does not seem to be the 

 case : elastic fluids of different specific gravities have 

 a tendency to equable mixture by a species of attrac- 

 tion, and the different parts of the atmosphere are 

 constantly agitated and blended together by winds or 

 other causes. De Saussure found lime water preci- 

 pitated on Mount Blanc, the highest point of land in 

 Europe ; and carbonic acid gas has been always found 

 apparently in due proportion, in the air brought down 

 from- great heights in the atmosphere by aerostatic 

 adventurers. 



The experimental proofs of the composition of 

 carbonic acid gas are very simple. If 1 3 grains of 

 well burnt charcoal be inflamed by a burning-glass in 

 100 cubical inches of oxygene gas, the charcoal will 

 entirely disappear ; and provided the experiment be 

 correctly made, all the oxygene except a few cubical 

 inches, will be found converted into carbonic acid ; 

 and what is very remarkable, the volume of the gas is 

 not changed. On this last circumstance it is easy to 

 found a correct estimation of the quantity of pure 

 charcoal and oxygene in carbonic acid gas : the weight 

 of 100 cubical inches of oxygene gas is to that of 10O 

 cubical inches of oxygene gas, as 47 to 34 : so that 

 47 parts in weight of carbonic acid gas, must be 

 composed of 34 parts of oxygene and 13 of charcoal, 

 which correspond with the numbers given in the se- 

 cond Lecture. 



Carbonic acid is easily decomposed by heating 

 potassium in it ; the metal combines with the oxy- 

 gene, and the charcoal is deposited in the form .of a 

 black powder. 



