As the walls of a garden form one of the principal sources of expence, it is proper, before proceeding to build, to as certain correctly the average level of the borders, if the ground be unequal, so as to suit the depth of the foundation to it. If the inequalities be considerable, both walls and borders are made to sink and rise, so as to humour them. Declivities in a garden are not unpleasing ; and when they happen to slope to the south or east, they afford the earli est crop of different legumes, such as peas or beans. Some improvers have constructed a series of low flat arches as the basement of the wall, these arches having their tops on a level with the surface of the borders ; the piers left are from two to four feet broad, according as the foundation is firm or otherwise. The advantage consists not merely in saving much building, but in permitting the roots of the wall-trees, which are planted opposite to the arches, to ex tend themselves in every direction, and draw nourishment from the soil on both sides of the wall. In some places projecting stone buttresses are set at intervals in the walls, in order to strengthen them, and to break the force of the winds when sweeping along. But to this latter purpose they contribute little : temporary screens of reed, project ing at right angles from the wall, and removed after the blossoming season, when the chief danger is over, are thought better : and if any sort of strengthening columns or piers be necessary, they can be built so as to project only on the outside of the wall. In this country, walls are generally made of the thickness only of three bricks laid side by side, or somewhat more than a foot ; and to such walls, in exposed situations, buttresses may be very proper. When the walls are intended to be high, indeed, they arc commonly made sixteen inches thick for a few feet above the basement, and then gradually reduced to twelve or thirteen. The basement, whether of brick or stone, is al ways about six inches thicker than the lower part of the wall.
Walls have sometimes been built with curves ; and in perfectly calm weather, the trees in these curves must re ceive more heat than on a straight wall ; but it is found that in windy weather they suffer much more ; and that even when there is only a slight air of wind, a draught is pro duced around the trees, rendering their situation colder than if they were at a distance from the wall. Curved or semicircular walls are therefore no longer constructed. The inclining of walls to the horizon, in order to their re ceiving the sun's rays more directly, is excellent in theory, but not adapted to practice. Trellises may be so inclined, or close wooden palings: such indeed have been success fully employed in some gardens, as at Brechin Castle, the seat of Mr Maule of Panmure ; where curved walls may also be seen. A stone or brick wall, however, could not be sufficiently inclined without the support of a bank of earth, and this would inevitably keep the wall continually damp and cold. A coping is necessary to preserve the wall, not only by preventing the rain from sinking into it at top, but to throw it off from the sides, where its trickling down would do much damage. The best coping is form ed of long pieces of freestone, neatly hewn from four inches thick in the centre to two at the plinth ; the edges being made to project beyond the wall about two or three inches, and a groove being run underneath the plinth, to collect and throw off the drops.
What is commonly called the kitchen-garden has, in mo dern times, become almost the only walled enclosure. It is likewise the fruit-garden, the walls being chiefly intend ed for the protecting and training of fruit-trees. These, it is to be understood, are planted on both sides of the wall ; the exterior fruit-border being defended generally by a sunk fence and an evergreen hedge, with a wire fence for the exclusion of hares. If, after all, the enclosing walls afford too little room for training, a cross wall is built in the middle of the garden ; or where the establishment is large, and where fruit is much in demand, two cross walls are reared. These cross walls are not placed nearer to each other than a hundred feet ; if they be two hundred feet separate, it is perhaps better. They can scarcely be said to disfigure the garden ; on the contrary, they might be defended, as tending rather to enliven its effect, by pre. senting new scenes, as the successive central doors are opened. Tney seldom need to be high ; being generally destined for peaches, nectarines, or plums, nine or ten feet are sufficient.
Rot Walls.
AI. It may be proper in this place to say a few words of flued wails, as by much the best time for their construction is at the original enclosing of the garden. Hot walls are of two kinds ; such as are intended to have sloping glass frames attached to them, thus to a certain extent forcing the fruit ; and such as are not calculated for having this appendage, but merely to have screens over the blossoms in the spring. Both are generally built about ten or twelve feet high.
In the first kind of hot wall, a ground plate or low parapet, a foot high, and at the distance of perhaps five feet from the wall, is, in some places, formed for the glass frames to rest upon, these being heavy and strong ; the trees are trained on a trellis within a few inches of the wall ; and along the border in front of the trees, early crops of peas, kidney beans, or strawberries, are raised. In other places, the frames are very slight construction, and easily manage. able : they arc about two feet shorter than the height of the wall ; and this deficiency is supplied by a bordered pa rapet, on which rest the rafters for supporting the sashes : the space between the bottom of these and the wall, seldom exceeds three feet. One furnace is reckoned sufficient for 45 or 50 feet of such frame-work. When the new hood of the tree is sufficiently ripened, the whole is taken down and carried under cover. When there is a consider able extent of hot wall, adapted for the reception of glass frames, perhaps 250 or 300 feet, particular trees may be forced or omitted, and an opportunity is thus afforded of restoring trees, by allowing them a year's rest. For these hot walls, fire heat is required only for about four months, from the end of February to the end of May, and again for two or three weeks, when the new wood is ripening.