10 Passage of Gases through Tubes. [1818. 



Neither is the variation among the different gases between 

 the ratio of the velocity and pressure, connected with specific 

 gravity, at least I have not been able to observe such a con- 

 nexion. I have quoted an experiment, ot rather the general 

 result of several, on carbonic oxide and olefiant gases, and it is 

 adverse to the supposition ; and in others, made on sulphurous 

 acid gas and ammoniacal gas, still further departures from the 

 order of the densities were observed. 



If a tube sufficiently fine and long be connected with a por- 

 tion of gas under high pressure, so that the time occupied in 

 its passage through it be considerable, the effect will be pro- 

 duced, i. e. the times of different gases will vary from each 

 other, but not according to their specific gravities ; if the tube, 

 however, be cut off so that the gases pass quickly, then the 

 times will be as the specific gravity. Now, in the long tube, the 

 pressure and velocity will vary throughout its length, the pres- 

 sure being greatest at the internal or connected end, and least 

 at the other extremity, whilst the velocity is least at the end 

 towards the reservoir, and greatest at the other. But the 

 ratio by which the pressure and velocity decrease and increase, 

 appears different for and peculiar to each gas. At the end of 

 the long tube the olefiant gas issues more rapidly than hydro- 

 gen, though the pressure at the reservoir is the same; but 

 shorten the tube, and let that part in which high pressures only 

 exist confine the gases in their passage, and the hydrogen gas 

 will surpass the olefiant gas in velocity as far as 4 or 5 does 2. 

 It would seem, therefore, that in the long tube the pressure or 

 elasticity of the olefiant gas diminishes less rapidly than that 

 of the hydrogen, or that its velocity increases more rapidly. 



Perhaps these effects may be accounted for by the suppo- 

 sition of some power of expansion peculiar to each gas, which, 

 if existing, a tube would for many reasons be well calculated 

 to exhibit. The experiment requires numerous repetitions and 

 much time, and I have not yet had sufficient to satisfy myself 

 on the subject. I will therefore refrain from mixing up crude 

 notions with facts, and at some more convenient opportunity 

 endeavour to supply what is wanting in this paper. 



