328 
MR. J. P. JOULE AND PROFESSOR THOMSON ON THE 
Table VI. — Experiments in which the air, after passing through the cylinder 
of lime, was forced through a plug consisting of 740 grains of silk. 
1 . 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
Number of obser- 
vations from 
which the results 
in Columns 
4, 6, and 7, 
are obtained. 
Cubic inches 
passed through 
the nozle 
per minute. 
Water in 
100 grains 
of air, in 
grains. 
Pressure in lbs. 
on the square 
inch. 
Atmospheric 
pressure. 
Temperature of 
the bath. 
Temperature 
of the issuing 
air. 
Cooling 
eifect in 
Cent, de- 
grees. 
10 
Not observed. 
0-19 
79-852 
14-777 
17-050 
15-884 
1-166 
10 
Not observed. 
0-19 
80-133 
14-782 
17-066 
15-913 
1-153 
10 
Not observed. 
0-19 
7.9-870 
14-787 
17-079 
15-945 
1-134 
10 
5650 
0-19 
80-013 
14-793 
17-083 
15-967 
1-116 
10 
Not observed. 
0-15 
79-814 
14-960 
16-481 
15-338 
1-143 
10 
Not observed. 
0-15 
80-274 
14-957 
16-489 
15-374 
1-115 
10 
Not observed. 
0*15 
79-903 
14-953 
16-505 
15-392 
1-113 
10 
5378 
0-15 
77-867 
14-950 
16-521 
15-428 
1-093 
10 
Not observed. 
0-14 
78-214 
14-638 
12-851 
11-770 
1081 
10 
Not observed. 
0-14 
78-245 
14-638 
12-877 
11-800 
1-077 
10 
Not observed. 
0-14 
78-180 
14-638 
12-885 
11-824 
1-061 
10 
Not observed. 
0-14 
78-633 
14-638 
12-905 
11-839 
1-066 
Mean 
0-16 
79-250 
14-793 
15-483 
14-373 
1-110 
In the foregoing experiments the pressure of the air on its exit from the plug was 
always exactly equal to the atmospheric pressure. To ascertain the effect of an 
alteration in the pressure of the exit air, we now enclosed a long siphon barometer 
within the glass tube (fig. 10). The upper part of this tube was surmounted with a 
cap, furnished with a stopcock, by partially closing’ which the air at its exit could be 
brought to the required pressure. The influence of pressure in raising the mercury 
in the thermometer by compressing its bulb, was ascertained by plunging the instru- 
ment into a bottle of water within the glass tube, and noting the amount of the 
sudden rise or fall of the quicksilver on a sudden augmentation or reduction of 
pressure. It was found that the pressure equal to that of 17 inches of mercury, 
raised the indication by 0 o, 09 ; which quantity was therefore subtracted after the 
usual reduction of the thermometric scale. 
Table VII. — Experiments with the plug consisting of 740 grains of silk. Pressure of 
the exit air increased. Cylinder of lime used. 
1 . 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
Number of obser- 
vations from 
which the results 
in Columns 
4, 6, and 7, 
are obtained. 
Cubic inches 
passed through 
the nozle 
per minute. 
Water in 
100 grains 
of air, in 
grains. 
Pressure in lbs. 
on the square 
inch. 
Pressure of 
the exit air. 
Temperature of 
the bath. 
Temperature 
of the issuing 
air. 
Cooling 
effect in 
Cent, de- 
grees. 
10 
Not observed. 
0-14 
82-982 
23-093 
12-673 
11-612 
1-061 
10 
Not observed. 
0-14 
82-510 
22-878 
12-713 
11-676 
1-037 
10 
Not observed. 
0-14 
81-895 
22-798 
12-755 
11-725 
1-030 
10 
Not observed. 
0-14 
80-630 
22-488 
12-795 
11-792 
1-003 
Estimated at 
Mean 
5400 
0-14 
82-004 
22-814 
12-734 
11-701 
1-033 
