8 Passage of Gases through Tubes. [1818. 



The gases were passed through discs of paper, and the num- 

 ber of discs was increased so as to increase the obstruction, the 

 pressure and quantity of gas remaining the same. With one disc 

 of drawing-paper 6'5 cubical inches of hydrogen passed in 7 ; 



6'5 ,, ,, of olefiant gas in 18' ; 



with two discs the hydrogen passed in 15H 

 ,, olefiant gas ,, 38'; 



with three discs the hydrogen ,, 22''5 

 ,, ,, olefiant gas ,, 57 f< 75. 



Lastly, for the effect of obstruction, I used a tube filled with 

 pounded glass. This was uncertain, because on moving the 

 tube it was impossible, almost, not to move some of the par- 

 ticles within, and then, of course, circumstances were changed ; 

 but by sending the gases through one after the other, results 

 were obtained, the mean of which gave for hydrogen 3 ;< 4 

 ,, ,, for olefiant gas 4 ;> 7. 



It would seem from these experiments that mere obstruction 

 is not the cause of the effect observed in tubes, for when the 

 tubes are removed, and obstructions which retard much more 

 placed for them, the effect is lost ; and as the same aperture 

 produces no difference of effect at high or low pressures, the 

 variations between different apertures should probably be re- 

 ferred to some other cause. 



I then endeavoured to ascertain some of the circumstances 

 attending on tubes. Both glass and metal tubes produce the 

 effect, and a metal tube, down which a wire had been thrust, 

 did not seem to have this influence on the passage of gases 

 through it altered. The effect is heightened as the gas is 

 made to pass more slowly through the tube ; and this, whether 

 the increased time be caused by diminished pressure, increased 

 length of tube, or diminished diameter. This may be well 

 illustrated by putting several very fine tubes together, for the 

 particular effect is thus increased whilst the time is shortened. 

 Two brass planes were ground together, and a few scratches 

 made down one of them so as to form very fine tubes 5 through 

 these olefiant gas passed in 26'*2, and hydrogen in 32 ;< 5. 



Three glass tubes were taken of different diameter, and cut 

 into such lengths that they passed nearly equal quantities of 

 hydrogen gas in equal times by the same pressure ; their lengths 

 were 42, 10*5, and 1*6 inches. The longer tube passed the 



