FORM OF GREENHOUSE. 



199 



of the garden. The form, as shown in the ground plan, a, to be a 

 lengthened parallelogram, having the corners cut off. The elevation, as 

 shown at will be hght and elegant, and the cross section at c will 

 show the internal arrangement, viz., the stage for the plants, surrounded 

 by a walk on all sides, and heated by hot water, or smoke flues, as at 

 a fl, the pipes or flues carried round the house under the pavement of the 

 footpath, and the heat to ascend through ventilators fixed in the floor, by 

 which means it can be retained in or allowed to ascend from the chamber 

 in which the pipes or flues are placed. The front and end lights of this 

 house to be taken away at pleasure, and two of the uppermost tier of the 

 roof sashes made moveable, so as to sHde down for the purpose of venti- 

 lation. 



The most common form and arrangement of the best greenhouses which 

 are built against walls, is that of the annexed figure, and these answer 



every purpose of cultivation. The arrangement of such a house is this : — 

 the roof is composed of two hghts, and is supported by cast-iron uprights, 

 a, placed under every ' second rafter, and the intermediate rafter is 

 supported by means of a semicircular iron bar, which, springing frojn 



