174 MANUAL OF GARDENING 
smoke and hot air, instead of being carried directly upwards, is 
carried through a slightly rising horizontal pipe that runs 
underneath the beds. For some distance from the furnace, 
this flue may be made of brick or unvitrified sewer pipe, but 
stove-pipe may be used for the greater part of the run. The 
chimney is ordinarily at the farther end of the run of beds. It 
should be high, in order to provide a good draft. If the run of 
beds is long, there should be arise in the underlying pipe of <t 
least one foot in twenty-five. The greater the rise in this pipe, 
the more perfect 
will be the draft. 
If the runs are 
not too long, the 
underlying pipe 
may return un- 
derneath the 
beds and enter a 
chimney directly 
S over the back 
209. Useful kinds of watering-pots. These are adapted end of the fur- 
to different uses, as are different forms of hoes or 
pruning tools. nace, and such a 
chimney, being 
warmed from the furnace, will ordinarily have an excellent 
draft. The underlying pipe should occupy a free space 
or pit beneath the beds, and whenever it lies near to the 
floor of the bed or is very hot, it should be covered with 
asbestos cloth. While such flue-heated hotbeds may Le 
eminently successful with a grower or builder of experience, it 
may nevertheless be said, as a general statement, that when- 
ever such trouble and expense are incurred, it is better to make 
a forcing-house. The subject of forcing-houses and_ green- 
houses is not discussed in this book. 
The most satisfactory material for use in hotbed and cold- 
frame sash is double-thick, second-quality glass; and panes 
petty THT 
it 
ify 
i 
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