r Frederick Bramwell ingeniously arranged his data in the form
of a balance sheet, and showed 253,979 units unaccounted for; but
if from this we deduct the work lost in displacing the air, the
unaccounted-for heat falls to less than 4 per cent. of the total
heat of combustion. These results show how extremely accurate the
observations must have been, and that the loss mainly arises from
convection and radiation from the boiler.]

The data necessary for our purpose are:

Steam pressure 80 lb. temperature 324 deg. = 784 deg. absolute.
Mean temperature of smoke 389 deg. = 849 deg. "
Water evaporated per 1 lb of coal, from and at 212 deg. 11.83 lb.
Temperature of the air 60 deg. = 520 deg. absolute.
" of feed water 209 deg. = 669 deg. "
Heating surface 220 square feet.
Grate surface 3.29 feet.
Coal burnt per hour 41 lb.

The fuel used was a smokeless Welsh coal, from the Llangennech
colleries. It was analyzed by Mr. Snelus, of the Dowlais Ironworks,
and in Table II. are exhibited the details of its composition, and the
weight and volume of air required for its combustion. The total heat
of combustion in 1 lb of water evaporated:

= 15.06 x (0.8497 + 4.265 x (0.426 - 0.035/8))
= 15.24 lb. of water from and at 212 deg.
= 14,727 units of heat.

TABLE II.--PROPERTIES OF LLANGENNECH COAL.

---------------------+----------+------------+---------------------+
| | | |
| | | Products of |
| | Oxygen | Combustion at 32 deg. F.|
| Analyses | required +--------+------------+
| of 1 lb. | for | | |
| of Coal. | Combustion.| Cubic | Volume |
| | Pounds. | feet. | per cent. |
---------------------+----------+------------+--------+------------+
Carbon........... | 0.8497 | 2.266 | 25.3 | 11.1 |
Hydrogen......... | 0.0426 | 0.309 | 7.6 | 3.4 |
Oxygen........... | 0.0350 | --- | --- | --- |
Sulphur..........