$i GARDEN MANAGEMENT. 



198. In reference to the really practical question of walls, the Caledonian 

 Horticultural Society instituted, some years ago, a very interesting series of 

 experiments on the comparative merits of a wall coloured black, an inclined 

 wall at an angle of 50°, and a vertical wall of the same freestone. The results 

 were very varied. At 6 p.m. in April, the average temperature of the sloping, 

 the black, and the freestone wall was the same,— the brick wall was one 

 degree lower. During May the temperature of the brick wall was considerably 

 higher. At one o'clock in the day the average temperature of the sloping 

 wall was seven degrees higher than the brick wall, — the whinstone wall was 

 three degrees, and the free stone five degrees, lower than the sloping wall; 

 and at six o'clock the sloping wall was two degrees higher than the freestone 

 and brick wall, and five degrees above the whinstone ; but in frosty weather 

 the sloping wall was three degrees colder, in the night, than any of the others. 

 It may therefore be assumed that, for all practical purposes, the brick and 

 whinstone walls are nearly equal, and only a shade in advance of the freestone 

 wall. 



199. The position of the walls being determined, as well as the material, 

 the foundations should be excavated. Their depth must depend upon the 

 subsoil, and the workmen should dig until they reach a soHd homogeneous 

 bed. The trench completed, it should be filled up, to within six inches of the 

 surface, with conci-ete, consisting of six or seven parts of coai-se gravel, stones, 

 or brick rubbish, to one part of freshly-slaked lime, reduced to a thin paste, 

 which may be thrown over a thin layer of the gravel ; but the better founda- 

 tion is formed by mixing the material thoroughly in a heap, and tm*ning it out 

 of the wheelbarrow into the trench, from a raised bank, raking each layer level 

 £s it is thrown in. 



•00. The thickness of the wall must depend on its height, and the foundation 

 sihould be thicker by three or four inches than the wall itself— this thickness 

 rising five or six inches above the surface-level. For a wall six or seven 

 feet high, a single brick, or 9-inch wall, will suffice ; for higher walls, it 

 will require a brick in length and another in breadth, or 14 inches ; beyond 

 12 feet and up to 18, two bricks in length, or 18 inches. Walls of \hese 

 proportions are capable of suppoi-ting a lean-to green-house of correspond- 

 ing height, if they are properly bonded, and hot lime or good cement is 

 used. There is this practical difiiculty in the more weak wall, that the bricks 

 shrink unequally in drying. This inequality might be remedied by using the 

 shorter ones as "stretchers," as bricks laid longitudinally on the wall are 

 called, using the regular-sized bricks for "headers." But the bonding or 

 tying, which is the object of laying headers and stretchers, would not be at- 

 tained. It is, therefore, to be provided for by using half-bricks, and throwing 

 out the short ones. The brick in length and breadth, and that in two lengths, 

 are more easily laid and bonded ; but the chief aim of the gardener, if he is 

 charged with the superintendence of the work, is to see that the workmen 

 use the proper bricks, and that they are bedded in a moderate quantity of 

 moitar made of fresh-slaked lime or cement. 



