Mr. Dalton on the constitution of the atmosphere. 177 



an atmosphere of hydrogen gas in it, so as that it would 

 support the mercury in the barometer at go inches. Let the 

 tube B have an atmosphere of carbonic acid gas also capable 

 of supporting 30 inches of mercury. Now supposing it pos- 

 sible for the atmosphere to be for a few moments of uniform 

 density throughout the column, and that density the same as 

 at the surface of the earth, the height of the hydrogen 

 atmosphere would be about 66 miles, and that of the carbonic 

 acid about 3.3 miles ; or the heights would be in the ratio of 

 so to 1 nearly. Afterwards, when the atmospheres were 

 expanded to their natural extent, equal elasticities of the two 

 gases would also be at altitudes as 20 to 1 ; that is, if at two 

 miles of elevation the carbonic acid atmosphere supported 

 15 inches of mercury, that of hydrogen would support the 

 same at 40 miles elevation. These are positions too obvious 

 to be insisted upon. Conceiving now the atmospheres to 

 have acquired their perfect equilibrium, or to be at rest in 

 the respective columns, let numerous air-tight horizontal 

 partitions be imagined across both tubes at equal intervals 

 •from the ground upwards. These intervals may be either 

 small, as a foot, or larger, as a mile, as may suit our 

 purpose. 



Let now a communication be opened between each two 

 horizontal portions of the tubes, either by a perforation or a 

 small tube, as represented in the annexed figure, ati, s, 3,4, 

 &c. Then it is well known that the two gases would inter- 

 mix, and finally obtain such equilibrium, that one half of the 

 gas at first in each division would pass into the opposite 

 division, and the other half remain where it was. Hence, the 

 whole weight of gases in each whole tube would be still the 



MDCCCXXVI. 2 A 



