1 78 Mr. Dalton on the constitution of the atmosphere. 



same as before, namely, 30 inches of mercury ; half of which 

 in each tube would be carbonic acid, and the other half 

 hydrogen. 



Very great differences would be found in the proportions 

 of the two gases in ascending, viewing them either in regard 

 to volume or to weight. In the lowest division, or No. 1 , we 

 should find equal volumes of carbonic acid and hydrogen. 

 At the height of two miles, we should find about one volume 

 of carbonic acid mixed with two of hydrogen ; at the height 

 of four miles, the carbonic acid would be to the hydrogen as 

 one to four, nearly ; and at the height of 40 miles, there would 

 probably be no carbonic acid at all in either tube, but the 

 hydrogen would there be of one half the density it was in 

 No. 1. Above this, or above the limits of the carbonic acid 

 atmosphere, wherever it might be, there would be nothing 

 but hydrogen gas in each tube up to the limits of the hydro- 

 gen atmosphere. 



The Hmits of the atmosphere having been mentioned, it 

 may be proper to observe, that on the hypothesis of the 

 density of any atmosphere diminishing in geometrical pro- 

 gression to intervals of ascent in arithmetical progression, 

 every atmosphere must be unlimited, or of infinite extent. 

 But if any atmosphere is constituted of particles on the New- 

 tonian hypothesis, it is obvious that such atmosphere must 

 have a limit ; this limit will exist where the repulsion of two 

 particles becomes equal to the weight of one of them. 



We have no data from which to determine the absolute 

 height above the surface of the earth to which any one 

 atmosphere can ascend ; but we can form a pretty accurate 

 comparison of the relative heights to which two atmospheres 



