Dividing by 238.25 lb. gives the heat per 1 lb.
of fuel used................................... = 11,745 units.
And temperature of furnace:
11,745 units/(18.125 lb. × 0.238) + 530°......... = 3,253°
Temperature of chimney 700° + 460°............... = 1,160°
Maximum duty (3,253° - 1,160°)/3,253°............ = 0.643°

Work of displacing atmosphere by smoke at 700°:
Cubic feet.
Volumes of gases at 70°........................ = 228.3
" " " " 700°........................ = 499.8
-----
Increase of volume.................... 271.5

Units.
Work done=
(194.46 lb. × 271.5 cub. ft. × 144 sq. in. × 15 lb.)
/722 units ..................................... = 147,720
Maximum amount of work to be expected =
3,248,425 × 0.643.............................. = 2,101,700
Deduct work of displacing atmosphere............. = 147,720
---------
Available work........................ 1,953,980

Actual work done:
Units.
1,620 lb. of water raised from 60° and turned
into steam at 53 lb..... ...................... = 1,855,900
Loss by radiation and convection................. 70,430
10-1/2 lb. ashes left, say at 500°............... 1,129