592 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
It is obvious that the times approach the inverse ratio of the tensions, as will 
appear more clearly on comparing 1 the times observed with those calculated on that 
principle. 
Time observed. 
Time calculated. 
Transpiration of air of 1 atmosphere 
Transpiration of air of 0-75 atmosphere 
Transpiration of air of 0-5 atmosphere 
1 
1-3133 
1-9306 
1 
1-3333 
2 
With air of higher tension than 1 atmosphere, the same apparatus for compres- 
sion was also employed as in the effusion experiments (fig. 3). The capillary E 
communicated with the two-pint aspirator-jar (capacity / 2'54 cubic inches), which 
was fully exhausted on the plate of the air-pump. The air being then allowed to 
pass into the capillary, the instant of time was noted when the gauge barometer fell 
to 28 inches, and the other points described below. The external barometer stood 
at 29‘08 inches ; thermometer at 53°. 
Table VII. — Transpiration of Air of different Densities. 
Gauge barometer 
in inches. 
Air of 
1 atmosphere. 
Air of 
2 atmospheres. 
Air of 
175 atmosphere. 
Air of 
1-5 atmosphere. 
Air of 
1-25 atmosphere. 
Air of 
1 atmosphere. 
I. 
II. 
I. 
II. 
I. 
I. 
II. 
I. 
II. 
III. 
// 
// 
/✓ 
// 
// 
// 
H 
// 
// 
// 
28 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
6 
20 
253 
254 
66 
67 
85 
86 
114 
114 
162 
l6l 
255 
12 
310 
310 
70 
69 
91 
90 
123 
124 
182 
179 
311 
8 
220 
220 
37 
37 
49 
49 
69 
70 
110 
109 
221 
4 
349 
352 
39 
40 
53 
53 
78 
77 
132 
134 
346 
2 
328 
328 
20 
19 
29 
28 
41 
41 
78 
79 
229 
1460 
1464 
232 
232 
305 
306 
425 
426 
664 
662 
1462 
The times of transpiration in the preceding table require to be corrected, as they 
represent the passage of equal volumes of air measured after and not before the 
transpiration. Thus the same depression of the gauge barometer would be produced 
by half a volume of air of 2 atmospheres, as by a whole volume of air of 1 atmo- 
sphere; and it is necessary therefore to double the times observed of air of the 
former density, to obtain the time of passage of a whole volume. For the transpira- 
tion of equal volumes, in the gauge-range from 28 to 20 inches, which is most nearly 
equivalent to the action of a vacuum, we have — 
Equal volumes. 
Observed time of transpiration. 
Calculated time. 
Air of 1 atmosphere 
254 seconds 
.... 1 
1 
Air of 1*25 atmosphere 
201’9 seeonds 
.... 0-7949 
0-8000 
Air of T5 atmosphere 
171 seconds 
.... 0-6732 
0-6666 
Air of 1-75 atmosphere 
149-6 seconds 
.... 0-5890 
0-5714 
Air of 2 atmospheres 
133 seconds 
.... 0-5236 
0-5 
