CARNOT’S THEORY OF THE MOTIVE POWER OF HEAT. 973 
per hour. The economy may be estimated from these data, as in the other cases, 
on the assumption which, with reference to these, is the most probable we can 
make, that the evaporation produced by a pound of best coal is 7 Ibs. of steam. 
58. The following Tables afford a synoptic view of the performances and 
theoretical duties in the various cases discussed above. 
In Table A the numbers in the second column are found by dividing the 
numbers in the first by 83 in cases (1.), (2.), and (5.), and by 7 in cases (4.), (6.), 
and (7.), the estimated numbers of pounds of steam actually produced in the dif- 
ferent boilers by the burning of 1 Ib. of coal. 
The numbers in the third column are found from those in the second, by 
dividing by 618, in Table A, and 614 in Table B, which are respectively the 
quantities of heat required to convert a pound of water taken from the hot well 
at 30°, into saturated steam, in the boiler, at 140° or at 121°. 
With reference to the cases (3.), (4.), (6.), (7.), the hypothesis of Table B is 
probably in general nearer the truth than that of Table A. In (4.), (6.), and (7.), 
especially upon hypothesis B, there is much uncertainty as to the amount of eva- 
poration that will be actually produced by 1 1b. of fuel. The assumption on which 
the numbers in the second column in Table B are calculated, is, that each pound 
of coal will send the same number of units of heat into the boiler whether hypo- 
thesis A or hypothesis B be followed. Hence, except in the case of the French 
contract, in which the evaporation, not the fuel, is specified, the numbers in the 
third column are the same as those in the third column of Table A. 
TaBLe A. Various Engines in which the temperature of the Boiler is 140°, and 
that of the Condenser 30°. 
Theoretical Duty for each Unit of Heat transmitted, 440 foot-pounds. 
Work produced] Work produced] Work produced|Per cent- 
for each pound |for each pound | for each unit | age of 
of coal con- | of water eva- | of heat trans- |theoreti- 
(1.) Fowey Consols Experiment, reported in 1845, 
(2.) Taylor’ s Engine at the United Mines, work- S| 
ing in 1840, : 
(3.) French Engines, according to contrat 
(4.) English Engines, according to contract, 
(5.) Average actual performance of Cornish Engines, 
(6.) Common Engines, consuming 12 lbs. of best 
coal per hour per horse-power, 
(7.) Improved Engines with Expansion Cylinders, 
consuming an equivalent to 4 Ibs. of best 
coal per horse-power per hour, | 
VOL. XVI. PART V. 
sumed. 
Foot-Pounds. 
1,330,734 
1,042,553 
* * K *¥ 

565,700 
585,106 
165,000 
495,000 

porated. 
Foot-Pounds. 
156,556 
122,658 
98,427 
80,814 
68,836 
23,571 
70,710 

mitted. 
Foot-Pounds. 
253 
198-4 
159 
130°8 
111°3 
381 
114-4 
~I 
coal 
cal duty. 
57°5 
| 4541 
36:1 
29:7 
25:3 
8-6 
26 


