As the causes which promote or retard the formation, or which tend to dissipate the earth’s covering of vegetable mould—a covering, on the richness or thickness of which the fertility of ground, as well for most kinds of naval timber as for other products, is so much dependent, though of the greatest importance—have never, that we are aware of, been generally brought into view, we shall devote some space to their consideration. In the first place, to give a fair specimen of our author, we shall transcribe several pages where he {312} has treated this subject with some ingenuity, and on which he appears to have bestowed considerable care. “Those who have never had an opportunity of seeing old woodlands brought into cultivation, will scarce credit what has now been advanced, that the soil should be enriched by the production of wood, when the experience of ages has proved that it is always exhausted by other crops.”—“Trees draw their nourishment from a much greater depth than any of the grasses, roots, or different kinds of grain raised by the agriculturist. Most of the latter derive the whole of their subsistence from the part of the soil that lies within a few inches of the surface; but the former, from the superior strength and magnitude of their roots, are enabled to penetrate much farther, and extract food from the very rock which forms the substratum of a great portion, both of our cultivated and uncultivated grounds. This, though it does not account for lands being positively enriched by wood, makes it, at the same time, far less surprizing that trees should grow to a large size, and yet not exhaust the upper part of the soil in so great a degree as most of the crops cultivated by the farmer. “There is another circumstance which gives ground in wood a great advantage over that in {313} tillage, which is, that the leaves of the trees are suffered to decay and rot where they fall, and, by this means, an annual addition is made to the depth of the vegetable mould. Now, the leaves of a tree may be considered as bearing the same proportion to the trunk and branches, in respect to the nourishment which they require, as the straw of corn bears to the grain. But the manure which cultivated land receives, is, in general, little more than the straw which grows on it after it has served for food or litter to cattle. Ground in wood, then, actually receives, in the annual fall of the leaves, as much enrichment as the farmer bestows on his land under tillage.