THERMAL EFFECTS OF FLUIDS IN MOTION. 
345 
“Table of the Values of ^ ■ = [W]. 
“ Work requisite to 
produce a unit of heat 
by the compression 
of a gas 
[m](i+E0 — [w] 
E 
“ Temperature 
of the gas 
t. 
“ Work requisite to 
produce a unit of heat 
by the compression 
of a gas 
“ Temperature 
of the gas 
t. 
ft. lbs. 
ft. lbs. 
1357-1 
6 
1446-4 
120 
1368-7 
10 
1455-8 
130 
1379-0 
20 
1465-3 
140 
1388-0 
30 
1475-8 
150 
1395-7 
40 
1489-2 
160 
1401-8 
50 
1499-0 
170 
1406-7 
60 
1511-3 
180 
1412-0 
70 
1523-5 
190 
1417-6 
80 
1536-5 
200 
1424-0 
90 
1550-2 
210 
1430-6 
100 
1564-0 
220 
1438-2 
110 
1577-8 
230” 
We now know, from the experiments described above in the present paper, that the 
numbers in the first column, and we may conclude with almost equal certainty, that 
the numbers in the third also, ought to be each very nearly the mechanical equivalent 
of the thermal unit. This having been ascertained to be 1390 (for the thermal unit 
Centigrade) by the experiments on the friction of fluids and solids, communicated to 
the Royal Society in 1849 , and the work having been found above to fall short of the 
equivalent of heat produced, by about at the temperature of the air-experiments at 
present communicated, and by somewhat less at such a higher temperature as 30 °, 
we may infer that the agreement of the tabulated theoretical result with the fact is 
perfect at about 30 ° Cent. Or, neglecting the small discrepance by which the work 
truly required falls short of the equivalent of heat produced, we may conclude that 
the true value of — 1 1 for all temperatures is about 1390 ; and hence that if [W] 
denote the numbers shown for it in the preceding table, //, the true value of Carnot’s 
function, and [//,] the value tabulated for any temperature in the “ Account of 
Carnot’s Theory,” we must have, to a very close degree of approximation, 
^ — LH * [W] ’ 
But if j>] denote the formerly assumed specific gravity of saturated steam, p its pressure, 
and X its latent heat per pound of matter, and if g> be the mass (in pounds) of water in a 
cubic foot, the expression from which the tabulated values of [jo.] were calculated is 
H= 
i-H 
1 dp . 
A dt’ 
while the true expression for Carnot’s function in terms of properties of steam is 
1 — cr 1 dp 
^ A dt 
2 Y 
MDCCCLIV. 
