Though the soil, in small spots, may be very much changed by art; and though, in suburban gardens of only two or three perches, the soil may be entirely artificial, and consequently be made, in a great measure, what the proprietor wishes it; yet it is always desirable, where it can be done, to choose a soil which is good by nature. If we were asked what was the single quality in a soil, the predominance of which would entitle it to be called good, we should say friability. With reference to a small dwelling-house, and also to a small garden, this quality is more especially desirable, since it will almost always be found easier to alter the texture of a dry soil so as to render it retentive of moisture, than to drain and alter the texture of a wet soil to thoroughly as to give it a character of dryness. A dry soil may either have sand or gravel as its prevailing quality: the gravel affords the best foundation for a house, and the sand, the best subsoil for a garden. A soil, however, may be naturally either sandy or gravelly, and yet not be dry, from being placed on a retentive subsoil, or from the subsoil being connected with the watery subsoil of higher grounds.
In the case of a retentive subsoil, the surface soil, though sandy in its original nature, from being long saturated with surface water, and from that water containing vegetable matter, will probably have become black and peaty in appearance; and unless the water can be thoroughly got rid of by draining, such soils are decidedly unfavourable both for building and gardening. As chalky soil is almost always dry, it is favourable for building on; but, unless it has a considerable depth of soil over it, the expense of forming suitable garden ground is greater than on most other soils. A chalky subsoil in a valley is generally covered by a depth of loam on the surface, which loam forms one of the very best soils for growing every description of vegetables in the highest degree of perfection. Chalky soils, though dry, are invariably colder than most others, from the whiteness of the chalk not absorbing readily the sun's rays, and from the slowness with which a dense body like chalk is penetrated with the rain of summer, which is one of nature's chief modes of warming subsoils.
A strong clayey soil is not to be desired; because it will cost a great deal to render it fit for garden purposes; and because it forms a dangerous foundation for small houses built on its surface, on account of its liability to shrink during the great heats of summer, and to expand when remoistened by rains, thus throwing the walls of the house out of their perpendicular. In various parts of Middlesex, to the north of London, brick pottages may be seen built on strong clays, with walls leaning to one side, or bulging out, or with deep cracks in them produced by this cause. However, where the foundation of the house is sunk to the depth of 3 ft. or 4 ft., or where the surface of the clay is covered with a thick coat of gravel, small stones, or sand, or where it is payed, or laid with flag-stones, to the breadth of 3 ft. or 4 ft. all round the house, this disadvantage of a clayey soil will not be experienced; because the soil immediately connected with the foundation is thus, in a great measure, protected from atmospherical changes. A strong clayey soil can be walked on with pleasure fewer days of the year than any other, on account of its retentiveness of moisture; and it is the most expensive to cultivate, from its being alternately too hard and too wet.
It is, therefore, the very worst kind of soil for houses having an acre or two of ground attached; and it must obviously be the very worst that can occur, either for kitchen-gardens or flower-gardens. There is a description of clayey soil which is almost always soft and moist, because it abounds in springs; and, though no soil whatever, in its natural state, can be worse for building on, or for gardening, than this moist clay; yet, if it admits of being thoroughly drained, it may be rendered fetter for either purpose than the tough strong clay above mentioned. The reason is, that this springy cla,y, from the very circumstance of its being springy, or, in other words, so porous as to admit of water rising up through it, is less retentive of moisture, and more freely and easily worked, when drained, than the other. In some cases, however, the springs which rise from the subsoil cannot be effectually cut off, so as to render the surface perfectly dry; by which is meant, perfectly free from all moisture, but that which falls on it in the form of rain or snow.
Loamy soils (which, for our present purpose, it will be sufficient to consider as intermediate, either between sand and clay, or between peat or soft black earth, and chalk) are not unfavourable for building on, and are highly favourable for every description of gardening. A sandy loam, with rock or sand, or even gravel, for a subsoil, may be considered as the most favourable of all for gardening purposes, and, indeed, as the best soil for a country residence.