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Modes of constructing Forcing-Houses, 



Art. X. Considerations on the various Modes of constructing Forcing- 

 Houses, relatively to the Degree of Heat to be obtained in them 

 from the Sun's Rays. By Mr. George M'Leish. 



It is not my intention, while the mania for hot water is in 

 such an unsettled state, to enter largely on the manner of sup- 

 plying heat to the interior of hot-houses, either by flues or by 

 pipes conveying steam or hot water ; I shall confine myself at 

 present to the transmission of heat from the solar rays through 

 the medium of glass. 



To begin with the pine-stove : gentlemen gardeners (that is, 

 those who superintend their own gardens), and gardeners, and 

 amateurs, have, no doubt, seen a variety of pine-stoves with the 

 angle of their roofs varying from the flat roof of the pine-stoves 

 at Kensington to the comparatively steep one of the celebrated 

 Baldwin ; and very possibly have, one time or other, found very 

 good pines in most of them. They have, too, very probably, 

 generally taken it for granted, that those in which they have seen 

 the best pines must of course be the very best models which 

 they could copy in houses to be built for their own cultivation 

 of the pine, without once enquiring into the cause, or combin- 

 ation of causes, why the 

 pines in the houses which 

 they may have selected as 

 models have excelled in 

 either size or beauty. I 

 herewith send you the end 

 sections of two pine-stoves. 

 Fig. 72. is the pine-stove of 

 a gentleman with whom a 

 particular friend of mine lives in the capacity of gardener ; and 

 it exemplifies the flat roof of the Kensington fruiting-house. 

 Fig. 73. is one constructed after the man- 

 ner of Baldwin's fruit-house or stove. 

 I shall endeavour, as briefly as pos- 

 sible, to point out the advantages of the 

 latter over the former. In both figures, 

 a represents the sun's rays on Decem- 

 ber 21., in latitude 51°. In fig. 72., 

 the angle of incidence becomes 58°, which, by Bouguer's table 

 [see Fncyc. of Gard., §2457. new edit.], transmits more than 

 888 rays out of 1000, the remainder being reflected. This house 

 stands at an angle of 36° from south to east, consequently the 

 sun shines directly on the roof at ten o'clock, the sun's alti- 

 tude being then about 8° above the horizon, thus increasing the 

 angle of incidence to 65° ; which, according to the above-men- 

 tioned table, loses an additional 45 rays by refraction : for it is 



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