Читать книгу On Naval Timber and Arboriculture - Patrick Matthew - Страница 10

Table of Contents

Spanish or sweet Chestnut, sometimes named Chestnut Oak, sometimes included in the genus Fagus, seems at least a connecting link between Quercus and Fagus. This valuable timber tree, the largest growing, and, in many places, also the most common in the south of Europe, and which was once so {43} abundant in England that many of the largest of our ancient piles are wooded of it, has been for several ages much on the decrease in this country; owing, probably, to a slight refrigeration of climate, which, during this period, appears to have taken place, preventing the ripening of the seed, or, in more rigorous winters, following damp, cold summers, destroying all the young plants (at least the part above ground), whose succulent unripened shoots and more delicate general constitution, from immatured annual round of life, or imperfect concoction of juices, have not power to withstand the severe cold sometimes occurring near the surface of the earth. A very general destruction of the young plants of this kind of tree has occurred more than once within our memory from severe frost; but as the climate, a few years back, rather improved, and the spirit of planting became more general, a considerable number of plants of this tree have attained height and hardihood to withstand the cold, excepting in the points of the annual shoot, which we notice are again nipped (year 1830). This may give encouragement to more extended planting, as the tree is handsome, and, in most places, where water does not abound nor stagnate, acquires great size in comparatively short time. It is said to prefer a gravelly or stone {44} rubble subsoil, but we have seen it in rich clay, in row with large beeches, even exceed them in size. We should prefer for it any deep friable dry soil.

There is one circumstance connected with this timber in this country, at least in Scotland, which must prevent its general use in ship plank, and be of material injury to it for ship timbers; this is, that few trees of it of size are found without the timber being shaky or split, some to such a degree that the annual rings or concentric growths have separated from each other. This appears to be owing to our climate being colder than what is suitable to the nature of the plant; the sap in the stem possibly freezing in severe weather and splitting, or severing the growths of the timber, but more probably occasioned by the season being too short, and too moist and cold, to ripen or fill up with dense matter, sufficiently, the frame of the annual growths; thence, as each ring of sap-wood, prematurely hastened by the torpor of moisture and cold, turns to red or matured wood, and, in so doing, dries considerably within the other rings of moist sap-wood, the contractile force may be sufficient to separate this growth from the next external sap growth, the cohesion existing between the tissue or fabric of the growth being much stronger than the cohesion between one {45} growth and another. The uncommon dryness of the matured wood, and moistness of the sap-wood of this tree, and smallness of the number of sap-wood rings, commonly only from 2 to 6 in this country, incline us to believe that this is the cause of the insufficiency or defect; and that, in a milder, drier climate, the sap-wood rings will be found to be more numerous, and thus, independent of a better first ripening, affording a longer time for their cells to be more filled up with an unctuous matter (which prevents the shrinking) gradually deposited while they convey the sap, the sap-wood rings being the part of the timber through which the sap circulates. As proof of this unctuous deposit or filling up, we observe that dry sap-wood imbibes moisture much quicker, and in greater quantity, than dry mature. We think this premature maturity (if we may so term it) of timber in cold countries, a general law. Our larch, originally from the Apennine, has not more than one-third of the number of sap-rings of our Scots fir, indigenous in Mar and Rannoch mountains; and our narrow-leafed, or English elm, said to have been introduced from the Holy Land in time of the Crusades, has not more than one-half of the number of our indigenous broad-leafed, or Scots elm. From the sap-growths of Laburnum, {46} scarcely exceeding in number those of the Spanish chestnut, we should suppose that it has been moved northward, or that the proper climate has left it. We have observed that moist, or water-soaked ground, has influence, as well as climate, to deprive the alburnum vessels sooner of their living functions, inducing that torpor of tubes, or semi-vital condition, in which they only serve to support the more active parts, and constitute what is called Mature Timber.

It is a general opinion that Spanish chestnut soon takes rot in situations where the roots come in contact with water. This appears to result from moist soil inducing the too early maturing of the timber already alluded to, and occasioning shaky insufficient fabric, which soon corrupts. We have observed oaks which had fewer layers of sap-wood, from growing in damp situations, have the timber of inferior quality, and sometimes of a shaky, brownish description, when cut across, throwing out a dirty brownish liquid or stain.

From the use of the Spanish chestnut in the Spanish navy, both in planking and timbering, and from the roofing beams and ornamental work of Westminster Hall being also of this wood, we should suppose it was not so liable to this defect of rents in {47} the timber in milder climates. Chestnut timber is a good deal similar to oak, though not quite so reedy and elastic, but is destitute of the large laminæ or plates (flash), which, radiating from the pith to the outside, become so prominent to view in the oak when the longitudinal section is perpendicular to the outside, in the plane of the laminæ. It is, we should think, as capable of supporting weight, when stretching as a beam, as the oak, and is equally, if not more durable, many beams of it existing in very old buildings undecayed: it is said even to have been taken out fresh where it had stood 600 years as lintels. Earth stakes of it are also very durable. It possesses one advantage over oak, which must recommend it for ship-building, that is, having much less proportion of sap-wood; and, from the matured wood containing much less sap or moisture, we should suppose it not so liable to dry rot, or that more simple means, or shorter period, would suffice for seasoning it, so as to be proof against this evil. Spanish chestnut is as yet little known among British shipwrights; but were a quantity of it in the market free of the unsoundness we have alluded to, its merits would soon become known. The bark is used by tanners, but is said not to equal that of oak.