THERMAL EFFECTS OF FLUIDS IN MOTION. 
349 
to a sufficient degree of approximation, by the equation 
E=*0036534+- °° O441 P ~i~ . 
381 niog ^ 
Also, by using Regnault s experimental results on compressibility of air as if they 
had been made, not at 4 0, 75, but at 16° Cent., we have estimated P'V' — PV for the 
numerator of the last term of the preceding expression. We have thus obtained 
estimates for the value of from eight of our experiments (not corresponding exactly 
to the arrangement in seven series given above), which, with the various items of the 
correction in the case of each experiment, are shown in the following Table. 
No. of ex- 
periment. 
Pressure of 
air forced 
into the plug. 
Barometric 
pressure. 
Excess. 
Cooling 
effect. 
Correction 
by cooling 
effect. 
Correction by 
reciprocal 
coefficient of 
expansion. 
Correction 
by com- 
pressibility 
(sub- 
tracted). 
Value of J 
divided by 
Carnot’s 
function for 
16° Cent. 
P. 
p 7 . 
P-P'. 
8. 
JO 
1 1 
P'V'— PV 
J 
EH log P. 
E E' 
EH log P. 
Pis 
I. 
20-943 
14-777 
6-166 
6-105 
1-031 
0-174 
0-290 
289-4 
II. 
21-282 
14-326 
6-956 
0-109 
0-942 
0-168 
0-291 
289-3 
III. 
35-822 
14-504 
21-318 
0-375 
1-421 
0-519 
0-412 
289-97 
IV. 
33-310 
14-692 
18-618 
0-364 
1-523 
0-470 
0-372 
290-065 
V. 
55-441 
14-610 
40-831 
0-740 
1-892 
0-923 
0-480 
289-705 
VI. 
53-471 
14-571 
38-900 
0-676 
1-814 
0-883 
0-475 
289-59 
VII. 
79-464 
14-955 
64-509 
1-116 
2-272 
1-379 
0-592 
289*69 
VIII. 
79-967 
14-785 
65-182 
1-142 
2-300 
1-376 
0-586 
289-73 
Mean ... 
289-68 
In consequence of the approximate equality of - to its value must be, within 
a very minute fraction, less by 16 at 0° than at 16° ; and, from the mean result of the 
preceding Table, we therefore deduce 273*68 as the value of - at the freezing-point. 
The correction thus obtained on the approximate estimate 272*85 -\-t, for - 5 
at temperatures not much above the freezing-point, is an augmentation of ’83. 
For calculating the unknown terms in the expression for -, we have also used 
Mr. Rankine’s formula for the pressure of air, which is as follows : — ■ 
TjC + t | 
pv=n. ~ TV— { 1 
aC 
hC 
( 
»*!• 
where 
C ^ (C + 0 \§v; 
C=274*6, log 10 a=’3176168, logi 0 A=3*8181546, 
H: 
26224 
’ 1 — a + h ' 
and, v being the volume of a pound of air when at the temperature t and under the 
pressure p, g denotes the mass in pounds of a cubic foot at the standard atmospheric 
pressure of 29*9218 inches of mercury. The value of p according to this equation, 
