Mr. Dalton on the constitution of the atmosphere. 181 



of 40 miles that the gas of one cell would be adequate to fill 

 two cells, making the density in each the same as that in 

 No. 1000 before the communication. In all that interval of 

 40 miles the continuity of the atmosphere would be inter- 

 rupted, each cell having a partial void, and the partition 

 having a pressure on it from above, and none beneath. In 

 like manner it might be shown that the carbonic acid atmo- 

 sphere, were it alone, and subsequently made to communicate 

 with empty cells, would be two miles below the summit of 

 the atmosphere before one cell of gas could fill two cells.* 



After a complete equilibrium of intercourse had taken 

 place between every two adjacent cells, let us next conceive 

 all the horizontal partitions to be withdrawn from the two 

 tubes, and consider what results will ensue. 



It is evident the descent of the upper part of the hydrogen 

 column in each tube would be immediate, as there would be 

 vacuous places to fill up in it. The same would take place 

 with the carbonic acid column ; but the great body or weight 

 of the mixed atmospheres would remain unchanged, except 

 a slight condensation. The column of hydrogen in each tube 

 would support 1 5 inches of mercury, and would in all respects 

 resemble the upper half of the first column. A, of hydrogen 

 gas, that supported 30 inches, excepting a slight difference 

 occasioned by distance from the earth and temperature ; and 

 the same may be observed of the carbonic acid column in 

 each tube. But would this constitution of the mixture be 



• Query, might not the absolute height of an atmosphere of carbonic acid gas 

 (or any other) be found, by perfectly exhausting a tall receiver, then letting in a 

 small given portion of the gas, and finding by some chemical test that the gas 

 existed in the lower but not in the upper portion of the receiver ? 



