PROFESSOR GRAHAM ON THE MOTION OF GASES. 
361 
with the thermometer at 66°, and barometer from 30' 144 to 30' 112 inches. Means 
were taken to preserve the temperature constant during this and similar experiments, 
by immersing the condenser, and also the capillary, in vessels of water of which the 
temperature was watched by an assistant and preserved uniform. 
The average times of falling from a pressure of 20 to 10 inches are for oxygen and 
air, 593 and 533 seconds respectively; numbers which are in the proportion of 1 to 
0’8988. The average times from 10 to 6 inches are 467 and 419'5 seconds; that is, 
as 1 to 0'8983 : from 6 to 2 inches, 1030 inches and 924 seconds; that is, as 1 to 
0-8971. The average whole time of escape, or during the fall from 20 to 2 inches, 
is 2088 seconds for oxygen and 1876-5 seconds for air, numbers which are in the 
proportion of 1 to 0-8987. 
The transpiration time of air is therefore highly uniform under different pressures, 
and approaches closely to its theoretical density or time 0-9010. 
(3.) The parallel experiments on compressed carbonic acid gas escaping into air 
are contained in the following Table : — 
Table VII. — Transpiration of Carbonic Acid. 
Pressure by gauge barometer. 
Experiment I. 
Experiment 11. 
inches. 
// 
// 
20 
0 
0 
15 
178 
178 
10 
260 
260 
8 
148 
148 
6 
195 
195 
4 
278 
279 
2 
475 
474 
From 20 to 3 inches 
1534 
1534 
Comparing these times with the times of oxygen, we obtain the following results: — 
Transpiration times of Carbonic Acid. 
From 20 to 10 inches pressure 0-7384 
From 10 to 6 inches pressure 0-7345 
From 6 to 2 inches pressure 0-7311 
From 20 to 2 inches (average) 0-7346 
The times for carbonic acid have not the nearly perfect uniformity of those of air, 
for different pressures, but still their relation is close, particularly in the lower part 
of the scale where times are long and can be best observed. The time from 4 to 2 
inches is 474-5 seconds with carbonic acid and 650 seconds with oxygen, which give 
as the transpiration time of carbonic acid 0-7300. 
It will be observed how nearly the times for this gas approach 0-7272, the reci- 
procal of its density. 
In a second series of experiments made upon carbonic acid, at the same time as 
