322 



SCIENCE OF GARDENING. 



Pakt II. 



1638. Though the making of putty be hardly within the gardener's province, yet it is 

 fitting he should know that there are several sorts, of which the following are the prin- 

 cipal : 



Soft putty, being a well- wrought paste of flour of whitening and raw linseed-oil ; 



Hard putty, composed of whitening and boiled linseed-oil ; 



Harder putty, in which a portion of turpentine, or what is called, drying, is introduced ; and the 



Hardest putty, composed of oil, red or white lead, and sand. The first is the most durable of all, be- 

 cause it forms an oleaginous coat on the surface, but it requires a longer time for drying. The hard sorts 

 are apt to crack, if not soon well painted ; and the hardest of all, though it appears to be impenetrable, 

 and of the greatest durability, yet renders it difficult to replace a pane when broken. It seems, therefore, 

 quite unfit for hot-houses. Much depends on well working the putty some days before it is to be used ; 

 and in general, that putty which has been ground and wrought in a putty-mill is to be preferred. 



1639. The best sort of paint for hot-houses is that which, for the last twenty years, 

 has been known by the name of anti-corrosion, which is composed chiefly of the 

 powdered scoriae of the lead-mines of Col. Beaumont, near Hexham. There are other 

 sorts, which are called anti- corrosive and impenetrable paints ; but they have not been long 

 enough in use to enable us to recommend them. It may be a sufficient recommendation 

 of the anti-corrosion to state, that it is used in government works, and especially on all 

 cast-iron erections, by Rennie, Telford, and others. As to the color of paint, or washes 

 of any sort, for the walls or interior of hot-houses, it is almost unnecessary to observe, 

 that as light is the grand object, white is to be preferred. 



Subsect. 5. Walls and Sheds of Hot-houses. 



1640. Walls of some sort are necessary for almost every description of hot-house, for 

 even those which are formed of glass on all sides are generally placed on a basis f 

 masonry. But as by far the greater number are erected for culinary purposes, they are 

 placed in the kitchen-garden, with the upper part of their roof leaning against a wall, 

 which forms their northern side or boundary, and is commonly called the back wall, and 

 the lower part resting on a low range of supports of iron or masonry, commonly called 

 the front wall. Behind the back wall a shed is commonly formed, and within this is 

 placed the furnace, the fuel to be used therein, and other materials or implements con- 

 nected with the culture or management of the hot-house. 



1641. The parapet, or front wall, of hot-houses comes first in order. Where upright 

 sashes are used, there are generally brick walls, either carried up solid from the found- 

 ation, or built on piers, according as it may be desirable to have the roots of the plants 

 within pass through to the soil without, or not. In the case of fixed roofs, that part of 

 the wall which is above ground is formed with horizontal openings, to which opaque or 

 glazed shutters are fixed, opening outwards for the purpose of admitting air. A recent 

 improvement on parapets consists in forming them of cast-iron props or pillars {Jig. 267.), 

 which are placed on a basis of two or three bricks (c, c), three or four feet under the sur- 

 face : to these props, top and bottom rails are fitted, which are rebated to receive a shut- 

 ter. ( fig. 268.) The wall-plate (a, b,fgs. 267, & 268.), which receives the ends (d) of 

 the rafters or sash-bars, forms also a gutter for carrying off the water of the roof, exter- 

 nally (a), and the condensed water internally (Jigs. 267, & 268. b). 



267 



268 



269 



1642. Where the roof is moveable on the polyopic plan, no such t shutters are re- 

 quired, and therefore the ends of the rafters may go at once three <* ^ J^*^ 

 soil, according to the nature of the foundations, and rest on brick-work ; * e ^rfac e o f 

 the ground, and the lower edge of the lowest sash being united by a moveable plate, 

 forming at once a gutter and a rest for the lower rail of the sash. 



