568 PROFESSOR WILLIAM THOMSON’S ACCOUNT OF 
51. The expression for the amount of work necessary to produce a unit of. 
heat is : 
M(1+E¢4) 
E bl 
and therefore REGNAULT’s experiments on steam are available to enable us to cal- 
culate its value for any temperature. By finding the values of p at 0°, 10°, 20°, 
&c., from Table I., and by substituting successively the values 0, 10, 20, &c., for 
t, the following results have been obtained. 
Table of the Values of pies 
Work requisite to Work requisite to 
produce a unit of Temperature of produce a unit of Temperature of 
Heat by the com- the Gas. Heat by the com- the Gas. 
pression of a Gas. pression of a Gas. 
Ft.-lbs. - Ft.-lbs. ss 
1357°1 0 1446°4 ; 120 
1368-7 10 1455°8 130 
13790 20 1466°3 140 
1388-0 30 14758 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 15778 230 




Mr JouLe’s experiments were all conducted at temperatures from 50° to 
about 60° Fahr., or from 10° to 16° cent.; and, consequently, although some irre- 
gular differences in the results, attributable to errors of observation inseparable 
from experiments of such a very difficult nature are presented, no regular depend- 
ance on the temperature is observable. From three separate series of experi- 
ments, Mr JouLe deduces the following numbers for the work, in foot-pounds, 
necessary to produce a thermic unit Fahrenheit by the compression of a gas. 
820, 814, 760. 
Multiplying these by 1:8, to get the corresponding number for a thermic unit 
centigrade, we find 
1476, 1465, and 1368. 
The largest of these numbers is most nearly conformable with Mr Jouun’s 
views of the relation between such experimental “ equivalents,” and others which 
he obtained in his electro-magnetic researches; but the smallest agrees almost 
perfectly with the indications of Carnor’s theory; from which, as exhibited in 
the preceding Table, we should expect, from the temperature in Mr JouLE’s expe- 
riments, to find a number between 1369 and 1379 as the result. 

