716 Report of the Consulting Engineers on the Trials of 
and the products of combustion may be taken, without much 
error, as that of air at constant pressure, namely '238, so that 
per 1 lb. of coal, the contents of the furnace required 24 "456 
X '238 = 5*819 units of heat to raise them one degree in 
temperature. According to Table VII. page 727, each pound 
of coal is capable by its combustion of yielding 14,940 units of 
heat when the watery vapour, amounting to '2997 parts, which 
forms one of the products of combustion is condensed, and by 
that means renders the latent heat of that vapour sensible ; but 
when the water formed escapes as vapour, its latent heat is not 
available, and must be deducted from the heat due to the 
energetic chemical action in the furnace. In addition there 
are the '83 per cent, of moisture in the coal, and the 2*87 per 
cent, of hydrogen and oxygen in the proportion to form water 
amounting to '037 parts in all, which are converted into steam 
at atmospheric pressure. Altogether '3368 parts of steam are 
thus formed, and these render latent and absorb 325 units of 
heat, so that, making these corrections, the available heat 
of the fuel is reduced to 14,615 units per 1 lb, of coal. 
Associated with the burning fuel were 23*45 lbs. of air, and 
supposing its average temperature to have been 70°, or 530° 
absolute, the heat contained in the air and coal, reckoning from 
absolute zero, would be 24-45 lbs. x 530° x "238 = 3084 units, 
which added to 14,615 units due to combustion, makes the total 
heat of the products from absolute zero to be 17,699 units per 
1 lb. of coal. We have seen that it required 5*819 units to 
raise the contents of the furnace one degree in temperature, 
hence 14615 units would be competent to raise the temperature 
of 1 Ib," ^^'^^ ^ = 2511°, and as the absolute temperature of the 
air and coal was 530°, the absolute temperature of the furnace 
was probably not far from 3041°. The temperature of the 
escaping products of combustion was found to average 385°, or 
845® absolute, so that the proportion of heat which it would be 
possible to utilize would be ^^^3q^o^^^ = *722, The con- 
sumption of coal was at the rate of 44 • 03 lbs, per hour, so that the 
available heat would be 44 -03 lbs. X 17,699 u. X '722 = 562,645 
units. 
This quantity of heat was appropriated in three ways : — 
First, in evaporating 11 "21 lbs, of water from and at 212° per 
1 lb. of coal, and therefore per hour 
44*03 lbs. X 11*21 lbs. X 966*6 u. = 477,110 units; 
secondly, in supplying the loss due to radiation and convection, 
