230 Iteirospeclwe Criticism. 



Suppose, then, a house built, the angle of the roof of which is not 45", 

 but from 15° to 20°, or, as gardeners generally term it, I ft. rise in 3 ft. flat; 

 and having a bark bed nearly parallel with the roof, and at the distance 

 under it of say 4 ft., and arranged so that, should light pass through the glass 

 at right angles, it might illuminate all the bed and no more. By this you 

 will see that I mean to have no upright glass in front, and no wall supporting 

 the ridge of the roof. I see just as much reason for there being a wall to 

 lean a hot-house roof against, as there would be for a wall to support the 

 ridge of every cottage roof, instead of tying the rafters in couples, and making 

 each support itself. The fireways and footways, not being benefited by 

 light, should certainly be the shades in the picture, and be roofed with a 

 stronger and less polished material, for the same reasons (for you are deter- 

 mined to give and get reasons for all that you advance or accept) that the 

 selvages of fine cloth are made of a coarser wool and homelier colour than 

 the web j and doubtless this is done for the sake of greater strength and 

 cheapness, and to enhance the brighter qualities of the web by a powerful 

 contrast. But to return to the pine house, and in few words to sum up all. 

 The pine bed will thus be in extent perch for perch with the glass roof, 

 and therefore will contain, by the former calculation, as many pine plants in 

 a house 12 ft. wide and 30 ft. long, as the good old-fashioned house will hold 

 in 100 ft. long, and the same 12 ft. in width ; a back wall to support the 

 ridge will be done away with, and the pine-bed, plant stage, vine or peach 

 trellis, &c., placed parallel with the glass ; all the fireways and footways will 

 be stowed into the shaded parts, and the northern boundary, whether it form 

 a vaulted aile or a plain opaque roof, never allowed to make a less angle with 

 the glass roof than 90°. 



I have one reason more to urge in favour of this system of hot-house 

 building, and that is one that is seldom if ever attended to ; I mean the 

 deposition of damp or dew, and consequently the drip of water on plants 

 and people from the inside of the glass of a hot-house in cold weather. In 

 a frosty night you can scrape from the inside of the glass this frozen dew, 

 which, when thawed, falls like heavy rain. I have often observed the water 

 running down the insides of the cast-iron rafters of a cool green-house in the 

 mornings; and comparing these with wooden rafters under similar circum- 

 stances, and although the glass in both cases were alike moist, the iron being 

 such an excellent conductor of heat and cold, the inner surface would be 

 found nearly as cold as the external air, and consequently dew or damp was 

 deposited in abundance on its cold surface ; whereas the wooden rafters 

 seemed to resist heat, cold, and dew. Now, applying this to hot-house build- 

 ing, every change of temperature, either in the open air or in the hot-house, 

 causes the deposition of more or less dew ; but t|ie plastered ceiling of the 

 pathway beneath a tiled or slated roof will be much less aifected by changes 

 in the temperature than the glass roof will, and consequently will not collect 

 a tithe of the damp to drip on people that it would. I was very much 

 amused once, to see a venerable horticulturist with a quantity of grapes grown 

 in a cool green-house, which, when brought into a warm vinery to be weighed, 

 quickly changed from a jet black to a silvery grey, by the deposition of dew 

 upon their cold surfaces, to the utter astonishment of the worthy representa- 

 tive of the old school, who had then completed half a century in the study 

 and practice of gardening, and could never account for this unexpected 

 metamorphosis. But this will be the less to be wondered at, when I tell 

 you that an early edition of Alaiue's Gardener, ax\di Don'' s Catalogue, comprised 

 his library of garden literature. Mawe's Gardener, if I recollect aright, was an 

 heir-loom in the family, but Doll's Catalogue he certainly purchased on his 

 own account, and it was the only act whereby he was ever known to patronise 

 the learned in a business that had brought him an independent fortune. — 

 Alexander Forsyth. Alton Towe7's, February 8. 1840. 



Sir John Robison's Plant Case. (p. 1 17.) — 1 should recommend the intro- 

 duction of an alteration which I am under the necessity of making, to avoid 



