96 THE HOT-HOUSE. [Jan-. 
ends into these plates at regular distances, to receive and support 
the slope-glasses of the roof, placed close together upon these cross- 
bars or raftersi or these rafters may be formed so as to have a par- 
tition of one inch and half between the glasses, on tpp of which is 
to be placed a slip of board four inches wide, to prevent the rain 
working down along the edges of the sash frames: these rafters 
must be narrowed on the under side, the better to admit the rays 
of light and heat. 
The lights are to be laid on in two ranges or tiers, sliding one 
over the other, of sufficient length together to reach quite from 
the top of the upright framing in front to the top of the back wall: 
if these lights be placed close together, the rafters must be grooved 
lengthwise, above, to carry oft" the wet which may fall between 
them, making the upper end of the top tier shut close up to the 
wall-plate, running under a proper coping of wood or lead fixed 
along above close to the wall and lapped down with due width to 
cover and shoot off" the wet sufficiently from the upper termination 
of these sashes; likewise along the outer edge of the tojv^of crown- 
plate in front may be a small conductor of lead or wood to receive 
the water from the slope-glasses and convey it to one or both ends, 
without running down upon the upright sashes; being careful that 
the top part behind is well framed and secured, water-tight, and 
finish the top of the back wall a little higher than the glasses with 
a neat coping the whole length. 
In every part the wood-work must be made with the most criti- 
cal exactness, and all the sashes so fitted as to slide close and free; 
neat stays of iron may be placed on the under side of the roof 
lights, sunk into the wood and made fast by wood screws, in order 
to strengthen them; and the rafters or cross-bars are to be stayed 
with wood, at proper distances, to keep each firm in its place. In 
wide stoves it will also be necessary to place a neat upright, either 
of wood or iron, inside, under each of these rafters, to prevent their 
bending under the weight of the glasses, which are generally made 
to rest on the back wall of the bark pit. 
In glazing the roof-lights the panes are to lap over each other 
about half an inch; the vacancies where they overlap are by some 
closed up with putty, others leave them open, which is the better 
way when not too wide; in order both for the air to enter mode- 
rately, and for the rancid vapours arising from the fermentation of 
the bark-bed, &c. within thereby to be suffered to pass off"; and 
also that such as condense against the glasses may discharge itself 
at those places without dropping upon the plants: the glass for this 
purpose should be of a small size, and not more than from six to 
eight inches square; such would lap closer than larger sized glass, 
and form a much stronger roof. The great apertures occasioned 
by the crookedness of large panes admit the cold air so copiously 
in severe weather that incessant fires must be kept up to counteract 
it, which certainly is injurious to the plants; but of two evils you 
must take the least; and, besides, an extraordinary quantity of fuel 
is consumed this way which might be saved, and the plants kept in 
better health by adopting the smaller sized glass. Generally when 
