222 



FIXED STRUCTURES FOR GROWING 



the one sliding over the other; the upper sash sliding on ledges formed in the 

 rafters, so as to render it independent of the lower sash. In general, short 

 sashes for pits last much longer, and occasion much less hreakage of the glass 

 than long ones, from their leverage being so much less. The roofs of all 

 pits ought to have coverings, and the best material, hi our opinion, is boards, 

 as, where glass is so flat as it generally is in pits and frames, it is apt to get 

 dirtied by straw mats, unless these are put over a covering of bass mats. Fig. 

 J57 is an excellent plan of a pit or small house, with a span-roof all of glass, 



a, Back path. 



6, Bark pit, 50 ft. long in the 



clear. 

 c, Exterior pit for dung 



casing, to revive the heat. 

 d d, Gratings to drains. 

 e, Stink-trap to drain. 

 Fig. 157. Ground plan of a pit to be heated in Mr. Corbett's manner. 



designed by Mr. Glendinning, for general purposes, and heated by Corbett's 

 hot- water apparatus. Mr. Corbett's system appeal's to be better adapted 

 for pits than for larger and longer houses, where its heating power would 

 probably not be sufficient, or be unequal from the slowness of the circulation 

 in consequence of the water-troughs being necessarily on a dead level. Mr. 

 Glendinning's pit, however, may be heated by any mode, not even excepting 

 a smoke flue. Fig. 158 is a section of this pit, showing : 



/,/, Glass roof. g, Bark pit. 



A, Back path. 



i, Pit for dung casing. *, Drain. 



Hinged cover of ledged boards, 



to protect the dung from the 



rain and wind. 

 m, Ground lino. 

 n, Suspended shelf for strawberry 



pots. 



o, Slate shelf for pots. 

 p, Stink-trap communicating with 



the cross-drain (q) ,which leads to 



the main or barrel-built drain (k). 

 r, Corbett's hot-water apparatus. 

 s, Hollow wall of bricks on edge. 



Fig. 158. Cross section of a pit to be heated on CorbetCs system, or by smolsc-Jliies. 



Pits or low houses have been formed with glass on all sides, and span roofs 

 (see Gard. Mag. vol. vii. p. 290) ; but from the great quantity of glass in 

 proportion to the surface of floor enclosed, they become too expensive for 

 general purposes, and, unless furnished with a warm covering, the extensive 

 surface of glass occasions an injurious degree of radiation. 



516. The greenhouse is a light, airy structure, with a glass roof at an angle 

 of 35 or 40 with the horizon, and upright glass in front and at the ends ; and 

 with the means of heating sufficient to keep out frost, and in humid weather 

 to dry up damp. The plants are grown in pots placed on a stage, or range 

 of shelves rising one above another from a path in front, to within six or 

 seven feet of the upper angle of the back wall. Between the front path and 

 the upright glass, there is a broad shelf on a level with the lowest shelf of 

 the stage, for small plants that require to be near the light. All the front 

 and roof sashes are made to move, because it is frequently necessary to 

 admit a free circulation of the external atmosphere ; and coverings are 

 seldom applied, because a very little fire-heat is found to exclude the frost. 



