h pipe
would have given heat enough, but the heat would not have been so
steady. Both nut and stove coal is used in this heater, and in the
severest winter weather it burns not more than a common hodful in
twenty-four hours. It is so easily regulated that the temperature of the
cellar day or night, or in mild or severe weather, never varies more
than three degrees, namely from 57 deg. to 60 deg..

In a close underground cellar where the temperature in midwinter without
any artificial heat does not fall below 40 deg. or 45 deg. it is an easy matter,
with such a heater as this is, to maintain any desired temperature. If
the grates are renewed now and then, the heater should last in good
condition for twenty years. With the ordinary stove there is danger of
fire, of escaping gas and of sudden changes of temperature, and the evil
influence of a dry, parching heat--just what mushrooms most dislike--is
ever present. The first cost of a hot water apparatus may be more than
that of an old stove and sheet iron pipes, but where mushrooms are grown
extensively, as a matter of economy, efficiency, and convenience, the
advantages are altogether on the side of the hot water apparatus.
Furthermore, hot water pipes can be run where it would be unsafe to put
smoke pipes.

CHAPTER III.

GROWING MUSHROOMS IN MUSHROOM HOUSES.

[Illustration: FIG. 7. MUSHROOM HOUSE BUILT AGAINST A NORTH-FACING
WALL.]

A mushroom house is a building erected purposely for mushroom culture.
It may be wholly or partly above ground, and built of wood, brick, or
stone, and extend to any desired dimensions. But a few general
principles should be borne in mind. Mushrooms in houses are a winter and
not a summer crop, and they are impatient of sudden changes of
temperature and of a hot or arid atmosphere. Therefore, build the houses
where they will be warm and well-sheltered in winter, so as to get the
advantage of the natural warmth, and spare the artificial heat. They
should be entered from an adjoining building, or through a porch on the
south side, so as to guard against cold draughts or blasts in winter
when the door would be opened in going into or coming out of the house.
At the same time, do not lose sight of convenience in handling the
manure, either in bringing it into the house or taking it out, and with
this in view it may be necessary to have a door opening to the outside.
All outside doors should be double and securely packed around in win