FENCES, WALLS, AND SHELTERS. 



87 



ierate its circulation. This system obviates the necessity of cleaning the 

 flues, which is found difficult in practice; while hot water, which is advocated 

 in some places, is found too expensive for ordinary use. 



207. Coping to garden walls has been a "much-vexed" question, and pro- 

 bably many practical men retain their own system, without paying much 

 attention to theories ; for, in gardening, a common-sense 

 application of the means at hand, and taking everything 

 at the right time, is of more importance than the best- 

 formed theory imperfectly carried out. It seems very well 

 settled, however, that a stone coping, projecting an inch 

 or two over the wall on each side, is necessary for the 

 protection of the wall from the effects of rain, and to that 

 extent that the coping is useful in retarding the radiation 

 of heat. Mr. Walker recommends a coping, as improving 

 the appearance, and necessary for protection from the 

 weather ; and he adds, that a coping of slate flags, two 

 inches thick, bevilled off to three-fourths of an inch at 

 the edges on each side, which he saw in the gardens of 

 Mr. Walker, of Preskelly, Pembrokeshire, is one of the 



simplest and most efficient he had seen. "These projections," he says, 

 *' greatly enhance the conservative power of the walls." Ho proceeds to 

 condemn the practice of fitting wire or wood trellis on the face of the 

 wall, as interfering with this conservative power. "A space intervenes 

 betwixt the trees and the wall, where the heated air escapes at the small 

 angle of divergence, in consequence of the greater lightness of the air, 

 caused by rarefaction, while the constant flowing of the denser and colder 

 current to supply its place produces a current which destroys the forcing 

 power of the wall." He arrives at the conclusion that the only eligible 

 mode of training trees on an open wall is by nails and shreds. We think 

 the nails and eyes, the latter being close to the wall, might be made to meet 

 all his requirements, leaving the wall sound and clean. 



208. Admitting that the coping projecting two inches is necessary ior the 

 protection of the wall, and beneficial to the tree, the best horticulturists 

 come to the conclusion that temporary copings, extending eighteen inches 



beyond the wall, with protecting cur- 

 H ' r* -, tains depending from them, are very 



useful during the spring months ; and 

 Mr. Errington considers that by using 

 them in autumn a fortnight is added 

 to the summer, and time given for 

 the ripening of the young wood. He recommends a temporary coping, 

 seven or eight inches, in the summer and autumn, and twice that in April 

 and May. Mr. M'Intosh considers wet walls in summer as robbers of heat, 

 and that a wall with a good projecting coping, capable of being moved in tho 

 heat of the day, is invaluable after sunset. The portable coping at Dalkeith 



