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           EMBELLISHMENT OF GROUNDS.
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age to the villa residence must answer the promise
made in the early portion of this work.     The best
form for conservatories, in view of economy and the
best practical working, is undoubtedly the parallel-
ogram, although sometimes, for the sake of external
appearance, they are made circular or polygonal in
plan.  We take for granted that it is well known
that the roof:, as well as the sides of a conservatory
where plants are to be successfully grown, must be
made of glass.   A southern   aspect is     the    best,
yet east and west exposures do tolerably well, where
the admission of light is facilitated by plenty of glass.
These remarks apply particularly to conservatories
attached to the house, as those in some of the pre-
ceding designs.
  All conservatories ought to be provided with means
for warming them thoroughly, at pleasure, and al-
though the warm-air furnace with common square flue
is one of the most simple and inexpensive modes in
use, it is inferior to the steam and hot water systems
for this purpose: the latter dispenses a moist and
genial temperature, and is therefore much more condu-
cive to the healthy growth of plants.   The pipes con-
ducting the steam or hot water should be concealed
from view: perhaps the best plan of doing this is to
place them in a longitudinal air-chamber under the
walk, with perforated top to permit the distribution
of heated air; the diffusion of which is greatly accel-
erated by an opening from the outer air to the hot air
passage, the  admitted air becoming      immediately
heated and passing into the conservatory.
  Fig. 184 is a design for a large conservatory.   The
center building is intended for an implement-room on