614 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
tubes, for air, oxygen, nitrogen, hydrogen and carburetted hydrogen ; whilst the 
passage of carbonic acid is subject to a retardation in the upper part of the scale of 
the copper capillary, by which its rate increases so much as from 0 /5 to 07661, in 
the last series of experiments. The rate of carbonic acid indeed exhibits a want of 
steadiness with this capillary, which is not observed in the other gases enumerated. 
Thus we find it in the upper part of the scale 07639 by Table XXV. ; 075/3 by 
Table XXVIII. ; and 07661 by the last table. I may add, that in a preliminary 
experiment which was made with this gas, and also in an experiment made subse- 
quently to those recorded, and after the tube had been some weeks out of use, so high 
a coefficient was given for carbonic acid as 078. It is impossible to say whether this 
irregularity is properly referable to the material of the tube, or is peculiar to this 
individual capillary, as it is the only instrument of the same metal which was used. 
The copper tube has no advantage over the glass capillary for experiments on 
transpiration, while it is liable to the objection that it cannot be used at all with cer- 
tain gases which have a chemical action on copper, and would tarnish the surface of 
the tube. The experiments made with it, however, have their value in demonstrating 
that the rates of transpiration of different gases are essential properties of these gases, 
and not regulated by the material of the transpiring tube. Indeed there is no more 
reason to suppose that the coefficient of transpiration of a gas would vary with the 
substance of the tube, than that the specific gravity of the same gas would be found 
different according as it was observed in a glass or copper vessel. 
6. Transpiration of different Gases by a Glass Capillary Tube E. 
This was another long capillary glass tube, resembling H, but somewhat shorter. 
The extreme length of capillary E was 20 feet ; it allowed 1 cubic inch of air to 
pass into a vacuum in 12*03 seconds. One inch of this tube at either end was 
found to contain 1 grain and 0*94 grain of mercury ; the smallest of which admea- 
surements gives 0*0187 inch as the diameter of the tube ; that is, about g-Jryth of an 
inch. 
The following table contains a series of experiments on various gases, which were 
made on one occasion, and in the order in which they are given. 
Table XXXI. — Transpiration by Capillary E into a six-pint jar. 
Barom. 30*340— 30 288. 
Gauge barometer 
in inches. 
Air. 
Oxygen. 
Carburetted 
hydrogen. 
Hydrogen. 
Carbonic oxide. 
Nitrogen. 
Nitrous oxide. 
Carbonic acid. 
Air. 
i. 
Ii. 
i. 
ii. 
i. 
ii. 
i. 
II. 
i. 
II. 
i. 
ii. 
1. 
II. 
i. 
II. 
i. 
ii. 
72° 
72° 
72° 
72°-25 
72°-75 
72°-75 
72°-75 
72°-75 
72°-7 5 
72°-75 
72°-75 
72°-75 
72°-75 
72°-75 
72°-75 
72°-75 
72°-75 
72°-75 
28-5 
0" 
0" 
0 " 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
0" 
26-5 
153 
153 
172 
170 
93 
93 
75 
74 
150 
149 
150 
149 
129 
129 
130 
130 
154 
154 
24-5 
156 
156 
173 
175 
97 
97 
75 
76 
150 
151 
151 
153 
133 
133 
132 
132 
158 
158 
23-5 
84 
84 
92 
92 
52 
50 
41 
40 
80 
80 
81 
80 
70 
70 
70 
70 
84 
84 
From 28-5 to 23'5 in. 
393 
393 
437 
437 
242 
240 
191 
190 
380 
380 
382 
382 
332 
332 
332 
332 
396 
396 
