1818.] Passage of Gases through Tubes. 7 



Hydrogen in 57" 



defiant gas in 135"-5; 



but equal volumes of each passed through the same tube at 

 equal low pressures in the following times : 



Hydrogen 8' 15" 



defiant gas 8' 11". 



Again, equal volumes of carbonic oxide and carbonic acid 

 gases passed at equal high pressures through the same tube, 

 occupied, the Carbonic oxide 133" 



Carbonic acid 156"*5; 

 but at low pressures, Carbonic oxide 1 V 34" 



Carbonic acid 9' 56". 



I have lately had my attention again called to the subject, 

 but have not yet been able to satisfy myself of the cause of 

 this curious effect; nevertheless, as experiments do not always 

 owe their value to the hypothesis which accompanies them, 

 a few short observations on some made on this subject may be 

 acceptable. 



The effect is always produced by fine tubes at low pressures, 

 but does not appear to belong to the mere obstruction by the 

 tube to the passage of the gas, nor have I been able to pro- 

 duce it without a tube. A very fine needle-hole was made in 

 a piece of platinum foil, and so arranged on a mercurial gaso- 

 meter, that the pressure of a small column of mercury sent 

 seven cubical inches of the following gases through in the 

 times mentioned, namely 



Hydrogen 3''8 nearly, taking a mean, 

 Olefiant gas 9''2 ; 



and when the pressure was increased, the same proportions in 

 the times was observed. Other similar experiments gave 

 similar results. 



Slits, cut in platinum foil by the edge of a penknife, did not 

 give so great a superiority to hydrogen as that mentioned 

 above, and the proportion varied with different slits ; still the 

 hydrogen passed most rapidly, and a difference of pressure 

 caused no difference in the relative times. 



Three diaphragms were placed in different parts of the 

 same tube, each being perforated with a small hole, but the 

 effects produced in tubes were not observable here. Hydrogen 

 passed in 3*8 minutes, and olefiant gas in 9*1 minutes. 



