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 ratters; or these rafters may be formed so as to have a par- 

 tition of one inch and half between the glasses, on top of which is 

 to be placed a slip of board lour 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 oft' the wet sufficiently from the upper termination 

 of these sashes; likewise along the outer edge of the top or 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 ^lass, 

 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 ccrtainlv is injurious to the plants; but of two evils you 

 must take the least; anil, 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 



