GREENHOUSE. 
GREENHOUSE. 
colour is far inferior to that of fine shelf; or, in some cases, it may be 
yellow gravel. For laying out 
walks, and the mode of preparing 
the foundation of gravel walks, &c., 
see WALKs. 
GREEK VALERIAN.—See Po.e- 
MO‘NIUM. 
GREEN-FLY.—See A'‘puis. 
GreeENHOUSE.-—A_ structure for 
growing those plants in (more par- 
ticularly in the winter season,) 
which will not endure the open air 
of British winters. It may be of 
any form, but the most convenient 
is a square or a parallelogram, with 
upright glass in front, sufficiently 
high to admit of walking upright 
under it immediately within the 
glass; and with a sloping roof, at 
such an angle as readily to throw 
off the rain. This roof, for the 
better receiving the sun’s rays, 
should face the south, south-east, or 
south-west, and this is called the 
aspect. 
be lower than seven feet in height, 
and the height of the back should 
be about two-thirds of the width of 
the house. The space within is 
generally laid out so as to have a 
shelf in front, about two feet high 
from the ground, and two or three 
feet in width; and next there is a 
path two or three feet in width$ 
the remainder of the floor, from the 
edge of the path to the back wall, 
being occupied with a series of 
shelves, rising one above another 
like the steps of a staircase, on 
which the pots of plants are to be 
placed. These shelves may be nine 
inches or a foot in width, and the 
height of one above another may 
also be nine inches or one foot. The 
mode,in which artificial heat is com- 
municated to such a house is by 
smoke-flues, or hot-water pipes. 
The fire should be at one end, or 
behind the house, whichever may 
be most convenient ; and the prin- 
cipal flue or hot-water pipe should 
be along the front wall, under the 
The front should seldom | 
| under the path. The reason for this 
position of the flue or pipe is, that 
heat always ascends ; and, conse- 
quently, if the source of heat were 
placed under the back of the house, 
the heat would ascend directly to 
the roof at the upper angle of the 
house, and would scarcely heat the 
lower or front part at all. In order 
to admit of ventilation, the front 
sashes should open outwards, or slide 
along a groove ; and the roof-sashes 
should also open by sliding the one 
over the other. Other minor details 
need not be here entered into, as 
they are perfectly understood by all 
constructors of greenhouses,whether 
of wood or iron. With respect to 
these two materials, iron admits of 
the greatest variety of shape, such 
as a curvilinear ground plan and 
roof, and it also admits most light ; 
but the construction in wood is most 
generally understood, and is father 
the cheapest. Very excellent and 
| ornamental greenhouses in iron are 
| constructed by Messrs. Cottam and 
Hallen, and wooden houses may be 
made by any carpenter or joiner. 
\ 
WN 
Fg, 31.—A small Greenhouse. 
Fig. 31 shows a small green- 
house, heated by hot water, con- 
taining a propagating shelf (a) for 
' cuttings, as they must be near the 
7% 
