1818.] Passage of Gases through Tubes. 9 



hydrogen in ... 3 ; -7, the olefiant gas in '-75 



the second in ... 3'*5 ,, 2''5 



the smaller in ... 3''45 2'-8 ; 



and in several other experiments there seemed to be nearly an 



equal effect, when the quantity of gas passed in the same time 



was the same. 



I imagined that the specific gravity of the gases might have 

 some constant influence, but this does not seem to be the case; 

 carbonic oxide and olefiant gas are nearly of the same density ; 

 and if the effect depended upon their weight, it should be 

 nearly the same for both of them ; but this is not so ; seven 

 cubical inches of carbonic oxide required 4'6 minutes to 

 pass through a tube which was traversed by the same quantity 

 of olefiant gas under the same pressure in S'3 minutes, each 

 gas having been placed over caustic lime for some time pre- 

 viously ; and oxygen required to pass through the same tube 

 5 '45 minutes of time. 



I placed three gauges in different parts of a tube, of such a 

 size that it passed olefiant and hydrogen gas in nearly equal 

 times ; the gauges were very obedient to the pressure of the 

 gas in the different parts of the tube, but I could not perceive 

 any difference between the effect of the different gases. 



Such are some of the circumstances which affect and pro- 

 duce this curious effect : that the velocity of gases in passing 

 through tubes should be in some proportion to the pressure 

 on them is nothing particular ; but the singularity is, that the 

 ratio for the same gas varies with the pressure, and that this 

 variation differs in different gases ; thus the one which passes 

 with the greatest facility at low pressure, passes with the least 

 at high pressure. 



It may be deduced from the experiments at high pressures 

 and on obstructions, that the fluidity of the gas has little or 

 nothing to do in this case, for where it alone can have an in- 

 fluence, the indications are the same at all pressures, and the 

 gas of least density passes in the shortest time ; thus com- 

 paring hydrogen with olefiant gas, and considering its time 1, 

 the time of the latter will be in the experiments already men- 

 tioned, as 2-38, 2-42, 2-4, 2'57, 2'46, 2'57 ratios, which do not 

 differ much from each other, though the times, pressure, ob- 

 structions, and quantities of gas used vary very considerably. 



