220 



FIXED STRUCTURES FOR GROWI^'G 



ments that have taken place in the glazing of plant-stviictures of every 

 description, is the introduction of sheet window-glass, which, while it is 

 nearly as thick and strong as plate-glass, is not much dearer than crown- 

 glass. The thickness of this glass varies from one eighth of an inch to 

 something more than one sixteenth, and either thickness may be used in 

 lengths of from two feet to five feet. In the grand conservatory at Chats- 

 worth, the panes are three feet nine inches in length, that being the length 

 of the side of the ridge, and they are six inches in width, so that there is 

 no occasion for a lap. Ridge and furrow houses, when this kind of glass is 

 used, may be made nearly air-tight. In the grand conservatory in the 

 Horticultural Society's garden, the same kind of glass is used, and the panes 

 are sixteen inches by twelve inches. This house is remarkably well glazed, 

 and the laps are all puttied. Indeed, if this were not the case, it would be 

 almost impossible to heat such a lofty structure with glass on all sides ; 

 but this glass being very even, as well as thick and strong, the laps are not 

 more than three sixteenths of an inch, and do not retain any water, which, 

 indeed, from the temperature within being seldom greater than that without, 

 is not often deposited on it. 



514. Water is commonly supplied to plants in hothouses by hand ; but 

 pipes, pierced with small holes, have been arranged under the roof, which, on 

 turning on water from a cistern above the level, will throw down a shower 

 at pleasure. For lofty houses, such as the palm stoves of Messrs. Lod- 

 diges, the inventors of this system, this mode of watering is very eligible, and 

 it might also frequently be adopted in conservatories attached to dwelling- 

 houses, the cistern being in the upper part of the house. As a luxury, the 

 noise of the artificial shower, and the drops of rain, in a warm summer's 

 evening when all is arid Avithout, will more than compensate for the expense. 

 As water should never be applied to plants at a lower temperature than the 

 mean of the atmosphere which they grow in, there should be a cistern in 

 every house, of sufficient capacity to supply all the water which can be 

 wanted at any one time, placed over the flues or hot-water pipes in such a 

 manner as soon to be heated by them. In plant-houses these cisterns may 

 be used to a certain extent for growing aquatics ; but in this case only a small 

 portion of water should be taken from the cisterns at a time, so that the 

 addition of cold water may not chill the plants. To prevent the rose of 

 the watering-pot from being choked by the leaves or other matters in such 

 water, watering-pots with the grating described by Mr. Beaton (425) should 

 be used. 



515. The different kinds of fixed structures for plants, are — the pit, the 

 greenhouse, the orangery, the conservatory, the botanic stove, the pine stove, 

 and the forcing-house; and we shall conclude this section by shortly noticing 

 the characteristic features of each of these, and their varieties. 



516. Pits are low buildings with glass roofs, but without glass in the sides 

 or ends. The angle of the roof is between 15° and 25° with the horixon, 

 and the surrounding walls are generally built of brick, and hollow, or in 

 some kinds of pits they are pigeon-holed, or with thin panels to admit the 

 heat of exterior casings. The provision for heating varies from the mere 

 power of retaining natural heat by coverings of glass or other materials, to 

 the obtaining of 70^ or 80^ or upwards of ai-tificial heat, which may be 

 supplied either by fermenting materials or fire-heat or by both com- 

 bined. The cold-pit is without any artificial source of heating, and in some 



