LAYING OUT THE KITCHEN GARDEN. 417 



make excellent walls, retaining much heat and lasting a long time, they 

 ought to be covered with a wooden trellis on which to train the trees. It 

 has been recommended by Hitt and others to build the walls on piers, for 

 the sake of allowing the roots of the trees to extend themselves on both sides 

 of the wall. As however the branches of the trees are constrained so ought 

 to be the roots, in order that the one may be proportionate to the other. 

 Besides, as there are generally trees on both sides of every garden wall, it 

 does not appear that, under ordinary circumstances at least, anything would 

 be gained by this mode of building walls, excepting the saving of a small 

 proportion of materials. Where walls are not built of brick, stone or earth, 

 they may be formed of boards, which when properly seasoned and after- 

 wards saturated with boiling tar, will endure many years, and produce as 

 much heat in the summer season as brick or stone. They are indeed colder 

 in winter and spring, but that circumstance is often an advantage by retard- 

 ing the blossoming of the trees, and lessening the risk of their being injured 

 by spring frosts. If a cavity were formed by the boarding, and filled with 

 pounded clinkers, or charcoal, or coke, much heat would be absorbed from 

 the sun heat, and thus form a source for giving out heat at night. 

 Where the walls are formed of brick they may always be built hollow, 

 (472) to save material; and as very little additional expense will be 

 required to form the hollows into flues (475) or channels for hot- water 

 pipes, such an arrangement should not be neglected in the colder parts 

 of the island. The walks in the interior of the garden are laid out in a 

 direction parallel to the walls, and espalier rails are commonly formed parallel 

 to the walks. Exterior to the walls, a narrow portion of ground is inclosed 

 which is technically called the slip^ the object of which is to admit of getting 

 the full benefit of the wall on the outside as well as within. 



88G. In trenching and levelling the surface of the kitchen-garden, care 

 must be taken to form a complete system of underground drainage ; not only 

 by having drains formed of tiles to carry off subterraneous water, but by 

 having the surface of the subsoil parallel to the exposed surface, both being 

 inclined towards the situation of the drains ; so that the water in sinking 

 down from the surface may not rest in hollows (526). The best situation 

 for these drains will generally be under the walks. The depth of the soil 

 of a garden should seldom be less than two feet, this depth being penetrated 

 by the roots of even the smallest kinds of culinary vegetables when growing 

 vigorously. The depth of the soil, however, ought to bear some relation to 

 its quality, and to the climate. A loamy or clayey soil in a humid climate 

 need not be trenched to the same depth as if it were in a warm and dry 

 climate ; because the use of the soil to plants being to retain moisture, a 

 small body not liable to lose by evaporation, may be as effective as a larger 

 one so constituted as to lose a great deal. The borders for fruit-trees form 

 an important part of the kitchen- garden, and should always be prepared with 

 a due regard to the soil, the climate, and the kinds of trees to be planted. 

 The bottom should generally be prepared so as to prevent the roots from 

 penetrating into the subsoil : though as this naturally limits the supply of 

 water to the roots in dry seasons, and consequently gives occasion for 

 artificial waterings, a better mode than making the borders very shallow, is 

 never to dig them, and to spread the manure always on the surface. By 

 this means the roots will not be forced downwards, as they necessarily must 

 be when the surface is loosened and exposed to the drying influence of the 



