PROFESSOR GRAHAM ON THE MOTION OF GASES. 
603 
pump. This capillary (H) allowed 1 cubic inch of air to pass into a vacuum in 
15-64 seconds. Two inches of the tube were found to hold 265 grains of mercury, 
which gives a diameter of 0-0222 inch, or -j^-th of an inch. The tube, however, may 
have been more contracted at the bendings. 
Air-pump jars of greater size were also employed, so as to protract the time of 
passage, and give larger numbers. Of these vessels, which I have termed aspirator 
jars, the capacity of the “ three-pint jar ” was 103-56 cubic inches, and that of the 
“ six-pint jar” 201 -/8 cubic inches; the vacuous channels of the air-pump and con- 
necting tubes being included in these measurements. 
The temperatures recorded are those of the interior of the aspirator jar, observed 
by a very small mercurial thermometer, containing no more than 50 or CO grains 
of mercury, and therefore highly sensitive. It will be remarked that the tempera- 
ture within the receiver always rises, and in general about half of a degree Fahren- 
heit during the continuance of an experiment: this is owing to the compression of 
the gas already in the receiver by that which enters. The change of temperature due 
to this cause becomes less considerable with large aspirator jars, which are preferable 
to small jars for this and other reasons. 
As it appears that the relation between the coefficients of transpiration is only to be 
looked for at high pressures, attention should be more directed to the rates of trans- 
piration in the upper than in the lower part of the scale. The inquiry will therefore 
be directed with the view of solving the question, What are the coefficients of trans- 
piration of the different gases into a vacuum, or under considerable pressures ? 
Table XVII. — Transpiration by Capillary H. into a three-pint jar. Barom. 30-324. 
Gauge barometer in inches. 
Air. 
Oxygen. 
Hydrogen. 
Hyd. 95 + 5 air. 
Carbonic acid. 
I. 
II. 
I. 
II. 
I. 
II. 
I. 
II. 
I. 
11 . 
6l°-5 
6l°-5 
6 1 °*5 
6l°-5 
6l°-5 
6l°*5 
6l°-5 
6 1 °*5 
6l°-5 
6l°-5 
28 
0 ' 
0 " 
O'’ 
0 ' 
0 ' 
0 ' 
0" 
0" 
0 ' 
0" 
24 
213 
213 
236 
237 
104 
104 
125 
124 
178 
177 
20 
227 
227 
254 
253 
111 
111 
132 
182 
188 
188 
12 
549 
549 
611 
611 
268 
269 
321 
321 
454 
455 
8 
389 
388 
435 
435 
192 
192 
227 
227 
321 
320 
6l c -75 
6l°-75 
6l°-75 
6l°-75 
61 c *7 5 
61° 75 
6i c -75 
6l°-75 
61-75 
6i°-75 
From 28 to 8 inches 
1378 
1377 
1536 
1536 
675 
67 6 
805 
804 
1141 
1140 
Mean Results. 
Gauge barometer. 
Air. 
Hydrogen. 
95 IIyd. + 5 air. 
Carbonic acid. 
From 28 to 24 inches < 
From 24 to 20 inches < 
From 20 to 12 inches • 
From 12 to 8 inches ■ 
Time in seconds 
Time of oxygen = l... 
Time in seconds 
Time of oxygen = 1 ... 
Time in seconds 
Time of oxygen=l... 
f Time in seconds 
Time of oxygen = 1 ... 
213 
0-9006 
227 
0-8954 
549 
0-8985 
388-5 
0-8931 
104 
0-4397 
111 
0-4378 
268-5 
0-4394 
192 
0-4413 
124-5 
0-5264 
132 
0-5206 
321 
0-5252 
227 
05218 
177-5 ! 
0-7505 
188 
0-7416 
454-5 
0-7438 
320-5 
0-7368 
From 28 to 8 inches < 
Time in seconds 
Time of oxygen= 1 ... 
1377-5 
0-8968 
675-5 
0-4397 
864-5 
0-5237 
1140-5 
0-7425 
4 i 2 
