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   In order fully to demonstrate the advantages attending on the author's
mode of building flues for Hot-houses, on the proper construction of which
so much depends, a Plate is given, which shows at large the various kinds
of flues which he has found necessary to introduce in different situations.
Plate I. Fig. A. is a section of a flue under a pathway; a cavity or space
is left between the wall and the side of the flue, which is formed by three
bricks laid on edge; the flue is seven inches in width: another cavity is
formed on the other side of the flue, bounded by a wall built against the
ground. The top is covered with stone paving, and, at intermediate dis-
tances, apertures are cut through the paving, to receive the cast-iron fretted
gratings represented by Fig. B. which allow the heated air in the cavities
to escape into the house: a stone is placed in the wall, in which is cut
a groove to receive the gratings that are placed over the cavity next it.
The bottom of the flue is formed with plain tiles laid lengthways, which
rest on bricks placed at a proper distance cross the bottom of the flue:
the intermediate space between the bricks receives the damps emitted from
the ground, and prevents the draught of the flue from being checked,
which it otherwise would be, were it formed on the ground; also the
heated air from the bottom of the flue passes into the side cavities, and
from thence into the house.
   Fig. C is the section of a double flue above the ground, the bottom of
which is constructed in the same manner as the one already described.
The sides of the flue are formed with bricks laid on edge, and the flue being
seven inches wide, makes the whole a convenient width to be covered with
foot tiles; under the joints ought to be laid a piece of sheet-iron, hoop-iron,
or slate, to prevent the smoke penetrating through the joints of the tiles.
   Fig. D is an elevation of part of a double flue above ground, in which
are represented the spaces under the bottom, already mentioned.
    Fig. E represents the furnace, and the flue entering the house and
ascending to its proper height. The top of the furnace is formed with
an iron plate, and also the sides. The bottom is formed with bars in the
usual way, to let the ashes drop into an ash-pit underneath.
    Fig. F is the section of a front flue.