and into which the roots immediately connected with these boughs penetrate and afterwards keep possession. By taking off such branches early, therefore, the extra supply of nourishment afforded by such local circumstance of soil is directed to the stem and useful lateral branches.

It has been already observed, that, by depriving a tree, to a certain extent, of its side branches, the growth of the stem in length is promoted, but the diameter, strength, or thickness of it is not increased in the same proportion. When the side branches are destroyed by natural causes, or by the neglect of judicious thinning, the like injurious effects ensue to the primary object here in view, that of obtaining the largest quantity of timber of the best quality on a given space of land.

When the lateral branches perish or cease to be produced, except towards the top of the tree, from the want of pure air and of the vital influence of the solar rays on the foliage, the existence of the tree may continue for years, but the produce or increase of timber of any value ceases, and it dies prematurely, affording at last a produce comparatively of no value, after having obstructed the profitable and healthy growth of the adjoining trees during its latter unprofitable stages of life. In the contest for the preservation of existence which takes place after a certain period of growth among the individual trees of a plantation which has been neglected, or left without the aid of judicious pruning or thinning, there will be found trees which, from the accidental circumstance of having originally a vigorous, healthy constitution, and from partially escaping the numerous injuries and obstructions of growth that accrue to trees by neglect of culture, have attained to a valuable timber size. The timber of the few such trees, however, as have thus gained the supremacy, is frequently much blemished by the stumps of the dead branches having become imbedded in the wood; and this serious injury to the quality of the timber and value of the tree, is the invariable consequence of neglecting to prune off these stumps as soon as they appear, or rather neglecting to cut away close to the stem such branches as indicate decay, and before they cease growing.

The time at which pruning should begin, depends entirely on the growth of the young trees. In some instances of favourable soil and quick growth of the plants, branches will be found in the course of four or five years to require foreshortening, and in case of the formation of forked leaders, to be pruned off close to the stem. When the lateral branches of different trees interfere with each other's growth, pruning, so as to foreshorten, should be freely applied in every case, in order to prevent the stagnation of air among the branches, or the undue preponderance of branches on one side of the tree. Perfect culture, in this respect, requires that the plantation should be examined every year, and by keeping the trees thus in perfect order there will never be any danger of making too great an opening, or depriving a tree too suddenly of a large proportion of branches. The operation will also be so much more quickly performed, as to render the expense of management less than if the pruning were delayed, or only performed at intervals of years, as is too frequently practised. By this management there will be little, if any, necessity for pruning close to the stem, until the tree attain to twenty feet in height, or even more than that, provided the stem be clear of lateral branches from five to eight feet from the root. When the lateral branches are regular and moderately large, the smaller length of clear stem may be adopted, and where the branches are larger towards the top, the greater space of close pruning. Five years from the first close pruning will not be too long before the second is performed; one, or at most, two tire of branches

F

may then be displaced in like manner. The increase of diameter of the stem, is the only certain test for deciding whether the larger or smaller number of branches may be pruned off to most advantage, or whether it may be prudent to take any away from the stem until it attain greater strength and thickness. By examining the trees of a plantation annually, the critical time for pruning every branch for the best interest of the trees is secured. Some trees may be pruned with great advantage successively for years, whilst others may only require it every three or five years, and others again not at all.

It has been disputed whether resinous or non re-productive trees are benefited by pruning; but the value of judicious close pruning to that tribe of trees cannot be doubted: at the same time it is but too true that, in numerous instances, it has been carried to a mischievous excess. Young firs and larch trees, when deprived of their lateral branches, to within four or five tire of shoots of the top, are frequently seriously injured by the winds acting on the tuft of branches, which become as a lever loosening the roots, and producing all the evils of a suddenly checked growth, besides those of excessive bleeding or loss of the resinous sap, and the want of the periodical supply of nourishment to the stem afforded by these branches. At sixteen years of growth, larches standing at four feet apart, will be benefited by moderate pruning; i. e., of two or three tire of the lowermost branches, particularly should these appear to be decreasing in their former vigour of growth; and afterwards in every third or fourth year, successively, the like treatment should be adopted to these lowermost branches evincing a decline of healthy growth. The same rule applies to the pine or Scotch fir and the spruce; but the former, having large and compound branches, should be pruned at an earlier age than the latter, or before the lateral shoots are more than two inches in diameter. When the branch to be taken off is several inches in diameter, the wound is so large, the excavation of resinous sap so great, and the heart-wood, or the vessels which constitute it, so indurated, as to render the perfect union of the new and the old wood less certain than in young branches, all which make the removal of large branches productive of more evil than service t the growth of the tree and quality of the timber. On the contrary, when the pruning of the pine is altogether neglected, and the dead or rotten stumps or snags of branches are left to be embedded in the wood, or to form cavities for the accumulation of water or other extraneous matters in the substance of the stem, all the purposes of profit and of pleasure are sacrificed to neglect or unskilful culture.

Judicious thinning may be said to be productive of the same valuable effects to a plantation of timber-trees in the aggregate, as those which judicious pruning produces on every individual tree composing it: by the admission of a proper circulation of air and the solar rays, and permitting the free expansion of the essential lateral branches of the trees, as well as by preventing an unnecessary waste or exhaustion of the soil by the roots of all supernumerary trees.

The great advantages of judicious thinning are not confined to the object of obtaining the largest quantity of timber of the best quality on a given space of land in the shortest space of time; but the produce of the trees thus thinned out ought to afford a return sufficient to pay the expenses of culture, interest of capital, and the value of the rent of the land. In many instances the profits arising from the thinnings of well managed woods have covered these charges before the period of twenty years from the time of planting. The time at which the process of thinning should be commenced, depends on the like causes as those which regulate pruning, and need not here be repeated.

In general the freest growing plantations require to have a certain number of trees taken out by the time they have attained to eight years of growth from planting. On forest-tree soils of a medium quality, the age of ten or twelve years may be attained by the young trees before thinning is necessary; but should fifteen years elapse before the trees demand thinning, it will be found that the plantation has been imperfectly formed.

No certain rule can be given to determine the number of trees to be thinned out periodically, which will apply to all plantations and to every kind of forest-tree in them. A well-grounded knowledge of the principles of vegetable physiology, and of the habits of trees, is absolutely essential, to execute with success this very important branch of arboriculture. We may, however, quote the following statement from practice as one example, taken from an average of acres on an extensive plantation in Sussex :

One acre of siliceous sandy soil, worth 7s. per acre, when under pasturage, being properly prepared and planted with larch, at three feet and a half apart, required thinning for the first time, when the trees had attained to ten years of growth.

Number of trees when planted 3555 on one acre, of which 100 had failed during the first ten years of growth; therefore when the thinning commenced the number was 3455.

The future returns of income from the plantation, now rest on six hundred and eighty trees nearly arrived at their perfection of growth. The distance of nine feet apart is considered a sufficient space for the larch,

spruce, and silver firs, to attain to their maximum of timber growth, on soils of an average quality adapted to their habits; and as the above trees may profitably occupy the soil for twenty or thirty years more, or without ceasing to produce timber annually for that period, the thinning now should depend on, or be regulated by, the circumstances of demand for the produce, more than for the benefit of the individual trees which remain.

In the above details of thinning, it will seem to demand an explanation, why certain trees of the lowest value at fifty years' growth should have been left apparently to encumber the ground, while trees of a value equal to these are cut down at ten years' of growth. The answer to this question brings us back again to the difficulties before alluded to, of giving any data, or rules applicable in all cases, founded on number, size, distance and time, for the execution of the different processes of culture, relative to assisting and controlling the functions of vegetable life, so as to produce a given result, or obtain a specified quantity of timber from certain trees under different circumstances of soil, site, local climate, and culture.

If all trees were produced from seed with the same degree of constitutional strength, and were the soils on which they might be planted of the like nature throughout, and under equal circumstances with regard to moisture and exposure, as well as to every other influential point, then statical rules of practice for the culture of trees might with equal certainty be given, and of as general an application to suit every variety of case, as those for the execution of any mechanical art: but the reverse of all this is the fact; and every variation in the soil, and in the exposure and growth of the trees, must be met with a corresponding variation in the process of culture, as regards the number of trees to be thinned out, the distances at which they should stand, and their size and age. The trees above mentioned, which at fifty years' growth were not of greater value for the purposes of timber, than several trees thinned out at ten, assisted the growth of the more valuable trees, which immediately or more remotely adjoined them, by the shelter they afforded against cutting winds, and by ameliorating the local climate, to that degree as to fully warrant their continuance. Those trees which were of equal value to these when cut down at ten years' of growth, stood so close to others of greater promising value as to injure the growth of both, and had they been suffered to remain, would have prevented some of the most valuable trees of the plantation from attaining to perfection. Thus, on the one hand, by removing the former description of plants, the most valuable trees are promoted in growth, and on the other preserved from injury, by suffering less valuable ones to remain.

Various tables have been calculated to assist in deciding on the number of trees to be thinned out of plantations at stated periods; one of these by Mr. Waistell*, appears to be brought to as near a correct average, as the nature of the subject will permit.

"The following table shews the number of trees to be cut out in thinning woods, and the number left standing at every period of four years, from twenty to sixty-four years, reckoning that the distance of trees from each other should be one-fifth of their height, and that the trees should have increased twelve inches in height, and one inch in circumference annually, and to have been at first planted four feet apart.'

* Transactions of the Society of Arts, vol, xxvi., and Withers's 'Memoir on planting and rearing Forest-trees,' p. 37.

When there is a deficiency of access to certain parts of the plantation, and additional rides or drives must be made, the lines should be marked out by barking the trees in the course of it, or, what is better, by a circular mark with whitewash or lime. The roots should be grubbed up, and the surface of the ground prepared and sown with the seeds mentioned in Chapter V. When there are steeps or hills, the drives should be formed with the most easy ascent for the convenience of timber carts. The ascent ought not to be greater than one foot in thirty. The most useful instru ment for determining the ascent or descent of forest drives, is constructed in the form of the common level, furnished with an index divided into ninety degrees. When the plummet line hangs at the forty-fifth degree, Fig. 10.

the legs of the instrument indicate a perfect level (fig. 10), and when it hangs at a lesser or greater number, it indicates the degree of ascent or descent accordingly. In plantations the thinning of which has been neglected, the trees next the sides of the drives are always the largest and most valuable, and afford a test at all times to judge how far judicious thinning has been practised or neglected. When this essential part of culture has been neglected, the greatest caution is necessary in performing the work. The trees being grown up slender, weak, and deficient of side branches, a too sudden exposure to the winds or currents of air, will be found injurious, if not fatal. The outside trees should be continued in their thicket state for several years after the first relief is given to the interior trees, and even then should only be deprived of decaying companions, or of branches unnecessary for the purposes of shelter, but which it may be advantageous for the trees to lose. Trees weakened by growing in a crowded state, become more obnoxious to disease, and to the attacks of insects, and to that of parasitic plants, such as mosses and lichens, which rarely or never appear on healthy and vigorous trees. The number of trees to be taken out on the first occasion of the thinning of a neglected plantation should be very limited, and confined to those which have become the most exhausted. The process should be carried on for six or seven years, until completed. The pruning of such trees should be confined to the removal of decaying or dead branches, until the gradual introduction of fresh air, and the solar rays by the thinning process has renewed lateral shoots and invigorated the branches*. Forest-trees are, like other organized bodies, confined to a

*It is a great error to suppose, that by leaving trees in an individually crowded state, the object of a close cover is secured; on the contrary, this object will only be gained for