204 



THE GARDENER'S ASSISTANT. 



years, and at the end of that time be substantial, 

 yet we think cast-iron ribs at every 12 feet are 

 preferable, and such can now be made strong, 

 light, and elegant. To these purlins can be 



Fig. 264.— Section showing principle of Knight's Curvilinear House. 



secured, and then the intermediate bars for the 

 glass need not be so strong as would otherwise 

 be requisite. 



Frames. — These are usually made of deal 

 boards \\ inch thick. Their dimensions are 

 variable; but the larger they are the less ma- 

 terials are required in proportion to the internal 

 area. Thus, supposing the depth to be the 

 same in both cases — say 12 inches — a frame 3 

 feet by -4 feet would require for the sides and 

 ends 14 square feet of board, the space inside be- 

 ing only 12 square feet; whilst a frame 8 feet by 

 6 feet would require 28 feet for sides and ends, 

 and the area enclosed would be 48 square feet: 

 hence the larger, with only twice the quantity 

 of materials for what is called the box of the 

 frame, contains four times the space. It may 

 also be remarked that the small and large frame 

 both require the same amount of labour as re- 

 gards the joining of the sides and ends. These 

 are usually dovetailed; but Mr. Atkinson had 

 frames made with ends projecting beyond the 

 front board, and in the external angles thus 

 formed, as well as in the internal ones, triangular 

 pieces of wood were fitted, and to these the 

 sides and ends were nailed. In this way the 

 box of a frame can be put together without 

 dovetailing, and by almost any person. These 

 upright corner-pieces are also well adapted for 

 taking the bearing of the frame when placed on 

 posts or other supports. 



Pits (fig. 265).— The great utility of these 



structures is well known. In their simplest 

 form, without artificial heat, they are useful for 

 protecting many kinds of plants, which would 

 either be killed or much injured by exposure 

 to the open air in winter; and even in summer 

 this kind of pit affords the most convenient 

 means of sheltering delicate plants from heavy 

 rain and scorching sun. With heat at com- 

 mand, pits are available for purposes of pro- 

 pagation, nursing for larger structures, and 

 forcing vegetables, flowers, and fruit. Before 

 large structures are built, pits should receive 

 consideration, for without them a good stock of 

 plants cannot be brought forward. They are 

 constructed in many different ways. Fig. 265 

 represents two useful forms of pits, which may 

 be employed for almost any purpose. Modifi- 

 cations of these may be used as lean-to frames 

 against a wall or the front of a plant -house, 

 and heated according to requirements. For 

 general purposes two rows of 3-inch pipes on 

 each side are ample for the Span-roofed frame, 

 and two rows in front for the Lean-to. 



Propagating Pit (fig. 266). — This is usually 

 built so that the plants may be near the light; 

 the path, therefore, is best in the middle; and 

 there should be a good command of bottom- 

 heat under the bed of plunging materials. The 

 pit is 1 1 feet wide, and 8 feet high from the path 



Fig. 265.— Sections of Pits. 



to the upper angle of the roof; and the path is 

 3 feet wide. There are two beds 4 feet wide, 

 one on each side of the path, for plunging ma- 

 terials, ashes, tan, sand, or cocoa-nut fibre; 

 and each has one flow and one return pipe in 

 a chamber to afford bottom-heat, and two on 

 each side for top-heat; so that a high top and 



