462 



PITS AND FRAMES. 



the top. These ventilators have been 

 already described. The front wall, as well 

 as the external side one, which terminates 

 the range, is provided with ventilators, 

 m m m, 2 feet square, furnished with an 

 ornamental iron grating externally, and 

 internally with an opening and shutting 

 one, upon the louvre principle already 

 described. The subterranean ventilation 

 is brought from the front of the terrace 

 wall in 9-inch fire-clay tubular pipes, as 

 shown at i i i i, one-half of which enter 

 under the door sills, and pass along under 

 the pavement passage to the farther end 

 of the house, where their orifices come in 

 contact with the hot-water pipes a short 

 distance from the boiler ; while the other 

 alternate pipes, after passing through the 

 front wall under the 20-inch hollow par- 

 tition-wall, proceed in a like direction. 

 It will readily be seen that the pipes, 

 being made to terminate at the hottest 

 part of the house, will produce a draft in 

 them which will require a constant sup- 

 ply of fresh air from without to keep up 

 the circulation, and that fresh supply of 

 colder and heavier air will cause a diffu- 

 sion at the warmer parts, equalising the 

 temperature, replenishing the internal 

 atmosphere, and keeping up a constant 

 motion in the air of the house — a matter 

 of great importance to all plants. 



The air, as it travels along the tubes 

 under the pavement footpaths, has means 

 of escape at equal distances, through 

 nozzles cast on the sides of the conduct- 

 ing pipes. From these it passes upwards 

 through ornamental cast-iron gratings 

 let into the pavement at r r, &c. These 

 gratings extend the whole breadth of the 

 passage, and are 6 inches broad. 



The other air-tubes, which are laid in 

 the hollow partition walls, have also 

 3-inch fire-clay tubes attached to them, 

 III, &c, and bent so that their orifice 

 forms a plane with the top of the parti- 

 tion walls, rising up on each side of 

 the glass divisions, securing altogether 

 as uniform a distribution of air as can 

 well be imagined. 



These pipes are opened or shut at 

 pleasure by sliding lids, that cover them 

 more or less, according to circumstances ; 

 and so arranged that the whole can be 

 moved simultaneously, as already noticed. 



Rain-water tanks are placed under each 

 bed, as shown by the dotted lines on fig. 



651. These are supplied from the roof, 

 the tanks being placed level at top with 

 the floor of the passages. 



For cucumber pits, vide section Pits op 



VARIOUS CONSTRUCTIONS, &C. 



The succession and nursing pine-houses 

 in the same establishment are in all 

 respects the same as the above. 



The melon-house at Chatsworth is thus 

 described by Sir Joseph Paxton, in 

 " Paxton's Maga- 

 zine of Gardening 

 and Botany," ac- 

 companied with 

 cuts showing the 

 ground-plan, fig. 

 653, and cross- 

 section, fig. 654, 

 as well as by an 

 elevation and sec- 

 tion of the tanks. 

 This house is up- 

 on the ridge-and- 

 furrow principle, 

 and is admirably 

 ventilated by 

 openings in the 

 front parapet 

 wall, and also 

 by corresponding 

 openings in the 

 top of the back 

 wall ; the front 

 ones being under 

 the pediments, and the top ones above the 

 valleys or gutters. In the ground-plan, 



the different pits over the tanks are 

 shown, a a, with two small cisterns at 

 each end for cold water, as also to give 

 access to the tanks b b. The footpath c c 

 is a wooden trellis footpath; a form of 

 footpath Sir Joseph appears to prefer to 

 what we would judge to be preferable — 

 namely, a neat cast-iron open one. The 



