DE. JOTJLB ON THE THEEMAL EEEECTS OF COMPEESSTN& ELIJIDS. 
135 
the needle. To settle this point a long series of experiments was made, in which the 
deflections after 40" were alternately observed with deflections after three minutes. It 
was found that in the latter case the amount of deflection was one-tenth more than in 
the former ; and therefore, in my experiments with this fluid, the deflections, observed 
at intervals of 40", were increased one-tenth, as will be observed in the sequel. 
As it was not convenient to apply a manometer to the apparatus during the experi- 
ments, I afterwards ascertained the pressure I had employed, by means of the indications 
of a carefully graduated air-gauge, when the piston was pressed down with the same 
weights I had employed in the experiments. The pressures thus obtained were nearly 
the same as those estimated from the weights laid on the piston, a small allowance being- 
made for friction. The pressure given in the Table is that of the fluid after the weight 
had been laid on half a minute, minus the residuary pressure arising from friction of the 
piston after the weight was removed. 
Table I. — Experiments on the Heat evolved by the Compression of Water. 
Tempera- 
ture in 
degree 
Centigrade. 
t. 
Expansibility by 
heat per degree 
Centigrade. 
e. 
O 
1-2 
— -000042 
5 
-000016 
11-69 
-000112 
11-69 
-000112 
18 
-000185 
18-76 
-000193 
30 
-000300 
31-37 
-000303 
40-4 
-000396 
Pressure 
in pounds 
on the 
;square foot. 
! P- 
Capacity 
for heat of 
a cubic foot 
of liquid. 
K. 
53634 
53634 
53634 
53634 
53634 
53634 
536.34 
33117 
33117 
62-43 I 
62-45 
62-45 
62 
I 
-45 I 
62-41 I 
62-41 
62-29 
62-29 I 
62-14 
L 
L 
Deflections of the needle, 
each the mean of ten 
observations. 
- 5-2 
- 4-5 
2-6 
12 
15 
f-qj-kan 
Mean 
5-8/ 
Mean — 4-85 
Mean 14-2 
9-8 
17-2 U 
20-9 / ‘ 
14-3fl 
20-6 
19-0 J 
3-6q 
5-7 ^Mean 
22 -oi 
22- 9 ^Mean 
23- 8 J 
9-65 
19*05 
17-75 
4-17 
17-6 
22-90 
Value of 
deflections. 
596=1-03 
596 = 1-03 
596 = 1-03 
596=1-03 
890=1-46 
1454 = 2-58 
204 = 2-66 
554=1-24 
69:4 = 1*36 
Experimental 
thermal effect. 
-0-0083 
0-0044 
0-0244 
0-0166 
0-0312 
0-0315 
0-0544 
0-0394 
0-0450 
Theoretical 
effect, or 
(273+t)ep 
JK 
-0-0071 
0-0027 
0-0197 
0-0197 
0-0333 
0-0347 
0-0563 
0'035.3 
0-0476 
