When grown, the main stem, either used whole, sawn in two, or quartered, will form one wing of the knee, and the bent branch the other; see figs. c, d. The dotted lines shew the saw section. Particular attention must be paid to prevent oaks from separating into more than four leaders, and also to train up these leaders a considerable height, without allowing them to divide again, retaining always numerous feeders; thus, when the tree acquires size, {28} many valuable crooks g, h, i, will be formed above the knees. It is necessary, however, to guard against training the branches to too great a height, as, when so, they run much risk of being twisted and torn by high winds.
Knees may also be obtained by cropping the top from plants that have side branches similar to f, and training these branches for leaders as above directed. In this case, the section, where the top is cut off, must not be too large, and the branches, either two or four, well knotted to the trunk, or the situation sheltered, otherwise the trunk at the section may be split down by the strain of the wind on the new leaders. Also, in healthy growing trees of considerable size, which have spreading tops, and which are not to be cut down for a considerable time, the forester, if he have a good eye, may, by lopping off a few branches here and there throughout the top, throw the greater part of the boughs into condition to become knees, or valuable crooks, when of size. This is of most material consequence to the ultimate value of half-grown oak trees, in open situations, and ought to be particularly studied by the superintendent, as, when allowed to run into very numerous stemmy branches, without direction or curtailment, the top, instead of being ultimately of {29} considerable value as timber, is of none. Directions in writing will scarcely suffice to teach a forester this part of his business; he must consider attentively the knee figures and bends we have furnished, fix them in his memory, and use every eligible means to obtain them. Knees, of all descriptions of oak timber are in the greatest request. We have known them purchased at 7s. per computed solid foot, which, from the plan of measuring, is as much as 10s. per real solid foot. The prevailing inattention to judicious training will continue to occasion the supply of knees to be short of the demand, and thence the price high, provided some change does not take place in the structure of vessels, or iron knees be adopted, which are now sometimes used, or vessels, with the exception of the deck and rigging, be formed of iron altogether, which we have seen do very well in inland navigation.
As crooked round oak timber of the natural length is extremely unmanageable, and its distant transport very expensive, it is desirable that it be squared and cut in lengths suited to its ultimate use, where grown. This requires a thorough knowledge of the necessary curves, to which the figs. p. [19], will afford considerable assistance. However, the superintendent of any extensive fall of naval timber either should be {30} a shipwright who has had practice in lining off timbers, or should have passed several months in a dock-yard during the timbering of vessels, observing every piece that is put to use.
As most part of the timbers of a vessel have their sides squared, the cutter cannot err much in hewing away the sides in the plane of, and at right angles to, the curves, at least as deep as the sap-wood reaches, thus leaving only a little sap-wood on the angles; the sap-wood, in all cases (except in those small craft used in carrying lime, which preserves from rot), being worse than useless; by its decay not only weakening the vessel from the want of entireness of the timbers, but also acting as a ferment to further corruption.
In our directions for obtaining curved and angular bent timbers, we may be thought to have been a little too minute with the dimensions and figures: under the hand of the shipwright, or person of skill, a tree of almost any possible bend cuts out to valuable purpose: what is wanted is crooked timber, free of large knots;—first and second foot-hooks and knees are, however, most in demand.
NOTES TO PART I.
- [4]. Beech, suited for plank, is sometimes of more value when straight and of considerable length for the purposes of keel-pieces; for this the log requires to be from 30 to 70 feet in length, and at least of sufficient thickness at the small end to square a foot.
- [5]. These directions are generally applicable—as well for what may be required for being bent for compass-timbers, and for what may be used for land purposes, as for plank.
- [6]. There are several valuable varieties of apple-trees of acute branch angle, which do not throw up the hark of the breeks; this either occasions the branches to split down when loaded with fruit, or, if they escape this for a few years, the confined bark becomes putrid, and produces canker, which generally ruins the tree. We have remedied this by a little attention in assisting the rising of the bark with the knife. Nature must not be charged with the malformation of these varieties; at least, had she formed them, as soon as she saw her error she would have blotted out her work.
- [7]. Commencing by times, the greater part of training and pruning for plank, excepting in the case of dead branches, fractures, and last pruning, may be performed by a small knife.
- [8]. We are not in possession of sufficient facts to judge of the effect to hasten or deter decay occasioned by the timber having been softened in hot liquids of 212° or upwards, and not raised so high as to generate pyrolignous acid; but we think it must impair the elasticity.
- [9]. As excellent plank can be obtained by importation, the grower of naval timber ought to regard the production of crooks as a more patriotic occupation than the production of plank. It will generally pay better.