No. 2. A beautiful most luxuriant growing oak, in one of the sweetest sunny spots of the sweetest valley of our Highlands. This tree, of nearly two hundred solid feet of timber, and 80 years of age, was growing upon the bare shelf of a sound mica-schist rock. From underneath this shelf, several feet down in front, a most exuberant spring welled out, and the roots spread down over {201} the rock to the mouth of the crystal spring, no doubt tracing inward the course of the limpid waters into the rocky chambers of the Naiad. We had much conjecture how this tree came to be growing on the bare shelf, and finally concluded, that the nymph of the spring, while she sat there gazing on her beauties, under the varying dimpling reflection of the living waters, her rosy feet bathed by the glassy flood, had been surprised by some rude Celt, and to effect escape from his rough embrace, had been transformed by Diana into a tree. Yet whether of natural or supernatural origin, it was by the people of the glen held of miraculous virtue, and the sickly children were brought to be dipped in the spring after being borne several times round the charm-tree. When torn from its seat, the tree, though sound, and having a level fall (we saw it fall), broke across about twenty feet up, where the stem was about eight feet in circuit; this was owing to the very soft tender nature of the wood, which, although consisting of very large annual growths, was, when sawn out, the most porous insufficient Scots oak we have ever seen. As this fact may be ascribed to the supernatural,—the heart of the nymph beginning to soften towards the Celt at the time Diana interfered, accounting well for {202} the soft texture of the heart-wood of the tree, we shall not press it as a proof on either side of the controversy. Perhaps sober reasoners may think this all phantasy, and conclude, that the tree, from deficiency of substantial earthy food, and subsisting principally on slops (being mainly nourished by drinking of the delicious well), would, like an animal under similar circumstances, be of soft flabby consistency.
The above fact is opposed to common opinion—a Highlander always choosing his oaken staff from off a rock, as being most to depend upon; yet perhaps this preference is owing to some association with the hardness of the rock itself.
No. 3. We found a sycamore plane (Acer pseudo-platanus) in the same row with other sycamores, and about the same size, so exceeding hard that it could scarcely be cut down by mattock and hatchet, whereas the others adjacent were comparatively of moderate hardness, though differing considerably in hardness from each other; the soil in this case was very equable, being of Carse clay. The peculiar hardness of this tree could only be attributable to a harder variety. Indeed, the difference of quality in timber depends chiefly on the infinite varieties existing in what is called Species, though soil and {203} climate have no doubt considerable influence, both in forming the variety, and in modifying it while growing. Of varieties, those which have the thinnest bark, under equal exposure, have the hardest wood.
No. 4. We have cut a number of large old ash trees, and found, with one or two exceptions, of what is called thunder-struck trees (which we consider only an obdurate variety), that they were invariably of very free, weak consistency, more especially the latter formed growths, but even the earlier growths had become frush from age. This timber soon went to decay after being cut down:—one piece cut out into planks, and these being laid down in the order they occupied in the log, was in the course of some weeks rendered again entire by being agglutinated by Jew’s ears (a species of fungus.) The workmen were greatly startled at the fact, thinking the log bewitched. When immediately dissevered by wedges, the wood was so much decomposed, that its fibre was tenderer than the Jew’s ears, separating in a new course in most places, in preference to the saw draught occupied by the ears. We have found very old oaks have exactly the same friable character, so much so, as render their safe felling almost impossible; yet this oak timber had not lost much in weight {204} when compared after being dried with younger oak.
No. 5. We cut a row of ash trees, about 50 years of age, in dry Carse clay, by the side of a deep ditch, and consequently of slow growth; the timber was excellent, hard, strong, and weighty, rather most so where the size was smallest. At one end, where the row approached a brook, and the soil became richer and moister, several of the trees were of good size, but rather inferior in quality of timber, excepting one (the largest, though not the nearest to the brook), which was of very hard, strong, and reedy fibre, evidently a variety differing much from the others. It is always easy to discriminate pretty accurately the quality of the wood, by examination of the saw cross section of the trunk, that is, provided the same saw be employed, and be kept equally sharp; the best timber having the glossiest, smoothest section.
No. 6. We have examined Scots fir grown in many different situations; by far the best quality, of its age, of any we know, stands upon a very adhesive Carse clay, which, from the proprietor’s neglect, is all winter and in wet weather soaking with water, and the trees not of very luxuriant growth. These, till a few years ago, stood in close order, without the stem being {205} much exposed to parching or evaporation; this exposure of the stem rendering fir timber much harder and more resinous. Every body who has touched larch must be convinced that the slow grown on poor tills, especially with long naked stems in exposed situation, is very much stronger and harder than the quick grown, though often not so tough: but much depends on the variety in larch, those having the reddest matured wood being much harder than the paler coloured.
Memel fir, which is the largest growthed red pine we are acquainted with, is very strong and durable, probably next to the pitch pine of North America; yet the very large growthed Memel is generally weakest, though we frequently find a log of small growthed, mild and inferior in strength. In old buildings we have often witnessed the beautiful small growthed red wood pine wormed, when the larger growthed was sound, but we are sensible that spontaneous decomposition and consumption by insects are very different; much resin deters insects, whereas, in moist situations, as in treenails of vessels, it conduces to spontaneous decay; yet is it preservative when the timber is exposed to the weather by excluding the rain. {206}
The coniferæ differ much in the internal arrangement of their woody structure from the hard wood species, having tissue of much larger cells, and being generally destitute of the large lineal tubes, which in hard wood constitute the more porous inner part of the annual layer. When these tubes occur in the pines, they also differ in position, being in the outer part of the layer. Owing to the resin of the pines becoming fixed in the cells of the outer part of the annual layers, inspissated, we think, by the summer’s heat and drought (others say congealed by the cold), these cells are filled up, and this part of the growth rendered much denser than the inner part of the layer, being from solidity semi-transparent. We would attribute the abundance of resin in the Georgian pitch pine to the heat and long summer of that country, probably in concert with damp richness of soil, not only occasioning this deposit under these circumstances, but perhaps inducing a disposition in this species to the formation of this product[44]. The absence of the large tubes, {207} and the presence of oleaginous resin, render pine timber, when old and small growthed, not so brittle, nor so liable to decay, as that of deciduous trees; but it becomes very deficient in lateral adhesion. From the same cause we find the external layers of matured pine timber comparatively superior to the quality of the inner layers: in hard wood the exterior layers are generally much inferior to the inner. Boards of sap-wood of fast grown Scots fir, particularly of the outside layers are much better suited—stronger and more lasting, for boxes used as carriage packages, or for machinery or cart lining much exposed to blows and friction; than boards of the best matured red wood of Memel, Swedish, or Norway pine. This is principally owing to the fast grown alburnum possessing much greater lateral adhesion than the matured wood of old pines. To have these sap-wood boards in greatest perfection, the tree must {208} not lie in the bark after felling, and the boards must be well dried soon after being cut out. To expose the tree, peeled, either standing or felled, to the sun and dry air for some time, will considerably increase the strength of this alburnum. The wood, while in the state of sap-wood, of many kinds of timber is as strong and much tougher than the same wood after being matured, and would be equally valuable were any process discovered of rendering it equally durable; its insufficiency often arises from partial decay having occurred while in the log. The same sap-wood of oak, which, allowed to lie on the grass after being peeled in spring, will be so much decomposed in autumn that it may be kicked off with one’s heel; if cut out and dried immediately on being felled, it will be tougher than the matured, and, kept dry as cart-spokes, and defended by paint from the worm, will last and retain its toughness for an age. The tilling up, which to a certain extent occurs in maturing, is most probably deposited to fill up tubes, and may thus not greatly strengthen the mass; a hollow cylinder being stronger than a solid cylinder when extending horizontally over a considerable stretch, like a joist or beam; the mass may also become a little more fragile by maturing: besides a filling up is the result of some chemical change the {209} wood probably becoming slightly carbonized or approaching to that change which takes place when vegetables become peat.
It is rather difficult to speak of the strength of timber, as different kinds of timber, and different parts and qualities of the same kind of timber, have different kinds of strength. Some kinds are stronger as beams or joists, other kinds as boarding; while, again, some kinds are better for enduring a regular pressure, others for supporting a sudden jerk or blow, either as beams or boards. Some kinds are also comparatively stronger, moist; others when dry—and some kinds retain their qualities of strength or toughness longer than others when moist, and others longer when dry, although no rot appear.
No. 7. Purposely for experiment[45], we selected three ash trees, all growing in Carse clay, but differing the most in fastness of growth of any we could discover. We cut these down on the same day; two of them proved about 36 years planted, and the third 15; this, the youngest was of fast growth, and had layers of more than double the size of one of the {210} former, and about six times that of the other. We cut a number of pieces of exactly equal length and thickness (17 inches long, and nearly an inch on the side), from each of these, choosing them of clean straight fibre, at equal distance from the ground, and from the outside of the tree, and having their growths nearly parallel to one side, of course free of heart. We proved one of each immediately on being cut out while full of sap, with their growths on edge in horizontal position, supported at each end with a weight suspended from the middle. The smallest growthed, and the largest, weighed at the time of trial nearly equal; the medium growthed one-thirtieth more. The smallest growthed supported the weight about six minutes; the medium and the largest about half that time; the smallest growthed yielded the least before breaking, and the largest yielded the most. When completely dried, the weight of the medium growthed still continued greatest, surpassing the largest one-fourteenth, and the smallest about one-thirtieth. The smallest and medium supported nearly equal weight, during equal time, and outbore the largest about one-seventh[46]; when placed {211} with the growths on edge, they were stronger than when placed with the growths flat.