322 
MR. J. P. JOULE AND PROFESSOR THOMSON ON THE 
duced are laid down upon the Chart No. 1, in which the ordinates of the curves 
represent the temperatures according to the scale of thermometer C, each division 
corresponding to 0 - 04 77 of a degree Centigrade. The divisions of the horizontal 
lines represent intervals of time equal to a quarter of a minute. The horizontal black 
lines show the temperature of the bath in each experiment. 
The effect upon the pressure of the air produced by shutting the stopcock during 
various intervals of time, is given in the following Table : — 
Stopcock shut for 
5 s . 
15 s . 
30 s . 
l m . 
2 m . 
Initial pressure 
m 
S 
22-35 
22-35 
22-35 
22-35 
22-35 
Pressure after 
... 0 
5 
24-92 
24-92 
24-92 
24-92 
24-92 
Pressure after 
... 0 
15 
23-07 
28-46 
28-46 
28-46 
28-46 
Pressure after 
... 0 
30 
22-43 
23-38 
30-84 
30-84 
30-84 
Pressure after 
... 0 
45 
22-35 
22-5 
24-27 
32-03 
32-03 
Pressure after 
... 1 
0 
22-35 
22-43 
22-83 
32-79 
32-79 
Pressure after 
... 1 
15 
22-35 
22-45 
24-54 
33-08 
Pressure after 
... 1 
30 
22-35 
22-35 
22-83 
33-25 
Pressure after 
... 1 
45 
22-35 
22-43 
33-33 
Pressure after 
... 2 
0 
22‘35 
33-41 
Pressure after 
... 2 
15 
22-35 
24-54 
Pressure after 
... 2 
30 
22-54 
Pressure after 
... 2 
45 
22-40 
Pressure after 
... 3 
0 
22-35 
The last column gives also the effect occasioned by the permanent shutting or 
opening of the stopcock, 33-41 lbs. being nearly equal to the pressure when the stop- 
cock has been closed for a long time. 
In the next experiments, the opposite effect of opening the stopcock was tried, the 
results of which are laid down on Chart No. 2. 
The effect upon the pressure of the air produced by opening the stopcock during 
the various intervals of time employed in the experiments, is exhibited in the next 
Table 
Stopcock opened for 
3£- s . 
7-s 
15 s . 
30 s . 
l m . 
Initial pressure 
in 
s 
34-37 
34-37 
34-37 
34-37 
34-37 
Pressure after 
... 0 
H 
29-57 
29-57 
29-57 
29-57 
29-57 
Pressure after.. 
... 0 
7| 
27-43 
27*43 
27-43 
27-43 
Pressure after 
... 0 
15 
32-47 
30-41 
25-15 
25-15 
25-15 
Pressure after 
... 0 
30 
33-5 
32-47 
30-41 
23-23 
23-23 
Pressure after 
... 0 
45 
33-94 
33-5 
32-4 
29-4 
22-9 
Pressure after 
... 1 
0 
34-1 
34-1 
33-5 
32-13 
22-76 
Pressure after 
... 1 
15 
34-2 
34-3 
33-94 
33-24 
28-82 
Pressure after 
... 1 
30 
34-33 
34-37 
34-14 
33-90 
31-44 
Pressure after 
... 1 
45 
34-37 
34-37 
34-30 
34-14 
32-9 
Pressure after 
O 
0 
34-37 
34-33 
33-66 
Pressure after 
... 2 
15 
34-37 
34-06 
Pressure after 
... 2 
30 
34-20 
Pressure after 
... 2 
45 
34-37 
The remarkable fluctuations of temperature in the issuing stream accompanying 
such changes of pressure, and continuing to be very perceptible in the different cases 
