This taper
to the outlet will create a draught and so keep a better fire. Arch
this over with vitrified tile. The furnace end where the fire is
should be about six feet away from the bed. When the trenches are
completed, cover over with the dirt that was taken out of them. Two
such trenches under the frames will make a good hotbed. Anyone can
do this sort of work."
A hotbed can also be heated by running steam pipes through the
ground, but unless you happen to be where exhaust steam could be
used, this method is not economical except for big houses. The care
and expense of a separate steam plant would be too great to pay,
unless for growing winter vegetables for market or flower culture.
If you go into that on a scale large enough to pay, new problems at
once demand solution.
Vegetables under glass have kept pace with other crops. Within
fifteen miles of Boston are millions of square feet of glass devoted
to vegetables, chiefly lettuce. There are more than five million
feet in the United States used for other crops. Ordinarily, under
favorable conditions, glass devoted to this work will yield an
average of fifty cents per year per square foot.
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