Moisture in Coal.

All coals contain water which has to be evaporated in the firebox and converted into steam. This carries away useful heat. It has been proved that 1–25th part of the total heat given out by coal in burning may be carried away in the steam formed by the evaporation of the water contained in the coal and that formed by the combustion of the hydrogen.

The presence of water, volatile hydrocarbon and earthy matter mechanically mixed in with the fixed carbon, accounts for the ease with which a lump of coal disintegrates and breaks up into smaller pieces when heated.

(To be continued.).