368 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
To contrast the two different methods of transpiration, that of condensed gas 
escaping into air, and of gas under the usual pressure of the atmosphere only, or 
under a less pressure, passing into a vacuum, a third series of experiments was made 
upon olefiant gas. The same globular condenser being full of olefiant gas, of 
the tension of the atmosphere at the time, which was 30*034 inches, the gas was 
allowed to escape through the capillary M into the receiver of an air-pump kept 
vacuous by constant exhaustion. It was thus transpired into a vacuum but with con- 
stantly diminishing force, for the force with which the gas was sent out would 
diminish of course in proportion as the globular receiver was emptied. The baro- 
metric gauge tube of this receiver, being closed at top and vacuous, gave the neces- 
sary means of observing the progress of the escape of the gas as it was transpired 
into the vacuum. In the following table of observations, the first column of the 
height of the gauge barometer is its absolute height, and expresses the whole tension 
or elasticity of the gas. Thermometer 67°. 
Table XII. — Transpiration of Olefiant Gas. 
Height of gauge barometer. 
Olefiant gas. 
Air. 
Experiment I. 
Experiment II. 
Experiment I. 
Experiment II. 
inches. 
O 
O 
O 
0 
30 
0 
0 
0 
0 
25 
191 
191 
327 
327 
20 
276 
276 
480 
480 
18 
152 
152 
267 
267 
16 
187 
187 
316 
315 
14 
242 
242 
432 
430 
12 
318 
319 
558 
558 
10 
446 
446 
773 
771 
From 20 to 10 
1347 
1345 
2346 
2341 
The results are sensibly different in one part of the scale from those obtained by 
the other method of transpiration, as will be seen by comparing the following state- 
ment with the former results. 
Transpiration of Olefiant Gas (into a vacuum). 
Air =1. 
Oxygen =1. 
From 30 to 20 inches ... 
From 20 to 1 6 inches ... 
From 16 to 14 inches ... 
From 14 to 12 inches ... 
From 12 to 10 inches ... 
0-5791 
0-5476 
0-5615 
0-5717 
0-5777 
0-5212 
0-4928 
0-5054 
0-5145 
0-5199 
From 30 to 10 inches ... 
0-5743 
0-5169 
The time seems to increase as we descend in the scale, or with the resistance, 
with the exception of the first observation, which probably is made to deviate from 
the general progression by some accidental cause. It would probably be more cor- 
