The reason that Scots fir is of better quality, and more resinous, on good loam and moist till, than on poor siliceous ground, may probably be, that the loam contains more oleaginous matter, and other {304} vegetable products which bear a near relation to resinous, and which, transmitted upwards from the roots, may occasion richer assimilated juices. Men fed upon whale or seal blubber, if the digestion is good, have much fatty deposit upon the body, and the perspired fluid is oil. It is a fact well known to every intelligent farmer, that infield or croft land, that is land, which, having been earliest cultivated, was, of course, the best soil at first, and which has also been long highly manured at the cost of the outfield, and therefore containing much oleaginous and other matter, products of organization, produces grasses and other vegetables much more nutritive to cattle than the outfield, even though these vegetables be of the same species, and by reason of more careful culture of those of the outfield, also of the same size of plant. We have also considered that light, poor sandy soil, which throws up a considerable flush of vegetation in the spring, partly because it has then sufficient moisture, but which almost entirely gives over producing throughout the latter part of the summer, partly because the winter’s moisture is exhausted, may throw out the frame or skeleton of a considerable growth, or annual layer of wood, in the early part of the season, but may not afford sufficient matter for the filling up or {305} maturing the layer into good dense timber later in the season, when the assimilated fluid or sap is believed to descend.
Our author states, that the timber of pruned trees must be inferior to that of trees with many side-branches, because the consequent contracting and twisting of the vessels as they pass the junction of the branches and stem, obstruct the descent of the sap, thence the timber is better matured, and in firs has more of resinous deposit. We admit that the resinous deposition is more abundant in knots and in some of the parts adjacent; but the timber is not better throughout. Worm-eating may be observed to commence generally in the neighbourhood of knots. Although one part of the wood, in consequence of the obstruction of the knot, be more dense and resinous, another part, immediately above or below the knot, where the growths are extended to fill up the vacant space, where the worming commences, is less dense, and of inferior durability, and corruption begun, extends. The knotted timber, of course, is very inferior in strength and value to the clean. We would refer the longer continued flow of sap from maple and birches, which have many side-branches, in part, to the lower or side-branches commencing to vegetate sooner in the {306} spring than the top of the tree; this successive commencement of vegetation prolonging the bleeding.
Again, in larch, we find that by far the hardest and most durable wood is grown upon poor, hard, thin tills (that is, thin of vegetable mould upon the diluvium), even where the root-rot commences about thirty years of age. Now, we ask, is this the natural soil of larches? We have not, however, found larch from rich loam, of better quality than from poor sand, as we have observed in Scots fir. We also consider larch, grown on a proper larch soil—on sound soil and subsoil, or sound rock, common in acclivous situation—superior in quality to larch of equal quickness of growth, raised on rich loam or sand, though not equal to larch of slow growth from the above mentioned poor tills.
We would ask how our author is enabled to assume, as an axiom, that trees produce the best timber in their natural locality? We would also desire some rational information to shew in what manner pruning up can in any way conduce generally, to the increase of the timber, or to the enlargement of one-stemmed vegetables. A tree naturally rises in one stem. It throws out its branches in the disposition most favourable to draw the fullest benefit from the light and air. It of its own {307} accord (that is when man does not meddle), gradually raises its pyramidal centre, with proportional lateral spread, as high as is befitting, for the fullest expansion of the individual, under the circumstances of its location. Man may mar this beautiful natural balance easier than decypher the proximate cause he may throw the new deposit of wood in greater proportion upon the upper part of the stem, rendering his beam more suitable from equality of thickness, and particularly in pines, of cleaner, smaller growthed, more durable timber, thence more valuable. But the tree will neither produce the same quantity of measurable timber in a considerable number of years, nor will it ultimately reach to nearly the same size, nor continue life nearly so long, as when left to itself. Man’s interference is useful in removing competitors, in giving it lateral room for extension, in training it skilfully to one leader and subordinate equality of feeders, should transplanting, early pruning up, or other cause, destroy the natural regular pyramidal disposition—not in pruning it up, thus reducing it to narrower compass, and destroying its balance to the locality.
The use of the infinite seedling varieties in the families of plants, even in those in a state of nature, differing in luxuriance of growth and local adaptation, {308} seems to be to give one individual (the strongest best circumstance-suited) superiority over others of its kind around, that it may, by overtopping and smothering them, procure room for full extension, and thus affording, at the same time, a continual selection of the strongest, best circumstance-suited, for reproduction. Man’s interference, by preventing this natural process of selection among plants, independent of the wider range of circumstances to which he introduces them, has increased the difference in varieties, particularly in the more domesticated kinds; and even in man himself, the greater uniformity, and more general vigour among savage tribes, is referrible to nearly similar selecting law—the weaker individual sinking under the ill treatment of the stronger, or under the common hardship.
As our author’s premises thus appear neither self-evident, nor supported by facts, it might seem unfair, at least it would be superfluous, to proceed to the consideration of his conclusions and corollaries.
VII. CRUICKSHANK’S PRACTICAL PLANTER.
After the preceding parts of this volume had gone to press, we received a copy of Cruickshank’s Practical Planter. We endeavour to give a short view of the contents.
The author commences with some general remarks on the expediency and profit of laying uncultivated ground under timber, stating, rather too strongly, the very superior income derivable from forest than from heathy moors, and its advantages to the soil. No doubt, a great portion of the higher and more rocky part of Scotland is susceptible of little other improvement than planting; and, under timber, would produce more than ten times the income that it does in pasture; and the patriotic motive of embellishing his country, and enriching his countrymen, may excuse his having drawn the advantages of planting in rather high colours. Mr Cruickshank’s statement (as he says, designedly kept rather below the truth), that an acre of moor, of average quality, covered with Scotch fir, sixty years {310} planted, would contain 600 trees, value 10s. each, differs considerably from what has come within our experience. The timber of an acre of Scotch fir, sixty years planted in such waste ground as occurs in the valley of the Tay, will not average much more than one hundred pounds per acre on the spot, and laid down on the quay at Newcastle (the place to which the greater part of the Scotch fir on the east of Scotland is carried), would not produce L. 300 per acre.
In order the more to encourage planting, Mr Cruickshank runs into a speculative statement of the fertilizing influence of planting upon the soil, in rather a novel manner, leaving out the particular facts, which, he says, had come under his own observation, and adducing one as proof, furnished to him by another person unnamed. We have often had occasion to see ground, which had produced a crop of firs, brought under tillage without any marked fertility beyond the adjacent fields which had been under proper rotation of cropping, certainly inferior to what had lain for the same length of time in natural grass pasture. There is a particular instance in a slight rising ground (diluvial soil) in the Carse of Gowrie, where the fields, since the rooting out of the fir-wood, have not paid seed and labour in corn, though {311} under regular manuring and rotation. There are even varieties of pine, such as the loblolly, which are known to have an influence upon the soil where they grow poisonous to succeeding crops. Mr Cruickshank himself adverts several times to ground which had produced a crop of timber, being boss (hollow) from the roots remaining in the soil, and owing to this hollowness being unsuited for replanting till the roots were removed or consumed. We do not very well comprehend this hollowness, and ascribe the unsuitableness for replanting immediately, rather to exhaustion, or to the formation of something inimical to vegetation, than to any hollowness or manner of arrangement of the soil.