distinguish poor coal from good coal. In fact, proper care should be
exercised in all purchasing, for the person who understands the quality
of the thing to be purchased will be more likely to get full value for
the money paid than the one who does not. About coal, it should be
understood that good hard coal has a glossy black color and a bright
surface, whereas poor coal contains slaty pieces. The quality of coal
can also be determined from the ash that remains after it is burned.
Large chunks or great quantities of ash indicate a poor quality of coal,
and fine, powdery ash a good quality. Of course, even if the coal is of
the right kind, poor results are often brought about by the bad
management of a fire, whether in a furnace or a stove. Large
manufacturing companies, whose business depends considerably on the
proper kind of fuel, buy coal by the heat units--that is, according to
the quantity of heat it will give off--and at some future time this plan
may have to be followed in the private home, unless some other fuel is
provided in the meantime.

Mixed with poor coal are certain unburnable materials that melt and
stick together as it burns and form what are known as _clinkers_.
Clinkers are very troublesome because they often adhere to the stove
grate or the lining of the firebox. They generally form during the
burning of an extremely hot fire, but the usual temperature of a kitchen
fire does not produce clinkers unless the coal is of a very poor
quality. Mixing oyster shells with coal of this kind often helps to
prevent their formation.

53. COKE.--Another fuel that is sometimes used for cooking is coke.
Formerly, coke was a by-product in the manufacture of illuminating gas,
but now it is manufactured from coal for use as a fuel. Because of the
nature of its composition, coke produces a very hot fire and is