ON THE DECAY AND PRESERVATION OF WOOD.

Southland Times, Issue 1563, 12 April 1872, Page 3

ON THE DECAY AND PRESERVATION OF WOOD.

By James Hanax. The sharpest intellects of the age have L applied themselves to this subject, and 1 various methods have been suggested and t tried to prevent wood from premature decay, bv the action of the three elements ~ rotating one after the ot'ier — solar heat, r air, and water — and particularly its being per r orated by a grub produced by a four--1 winged insect depositing its egf;^ in the | bark or on the wood, when in a moist and gummy state. They will adhere to " the surface till they gain strength to bore > inwardly, remaining for about fuur vears ) doing the work of destruction. When 1 I full grown, they are about two inches ,' long, and coming again vo the surface, they lie dormant during the meta- • morphosing state to a flying insect. I have collected five varieties issuing from j their holes. The wood, shortly after all J have taken flight, falls into dust. It is | during the mouths of January, February, and part of March that they make their f appearance. The aborigines carry a small hook behind the ear to draw them out of their holes when in a fatty - J grub state, and esteem them delicious • eating. I have counted over two hundred eggs laid by one of the largest, which I encased in a lamp glass, on. a bib of wood ' inside. They are night flies, and the owl I or " mopoke" feeds on them, as do the tuis and robins on the smaller ones. The 1 woodhen and red parrot ka-kas, it is r well known, tear a,way the wood to get \ at them in the grub state. I have had some totaras taken out of mounds of earth in the bush, all heart, thirty feet long, making fifteen inches square, perfectly sound. The sap was turned into mould, from which an abundance of parasites grew. I have also seen some black pines nearly as large, all heart, and sound, dug up on the plains from land that was being ploughed. No doubt these had fallen when of mature age, and when the whole plain was covered over with bush, about two thousand years ago. Thus we see Nature's preservative, from 12 to 18 inches of mould, excluding the solar heat from extracting by evaporation the gummy essential oils which bind together the wood in one solid form ; but if we cover the like wood over with a coating of gravel the same thickness (that is the gravel obtained here, impregnated with decomposed shells and lime, containing latent heat, assisted by solar heat), it will draw from the wood its adhesiveness, disengage its ligneous fibre, and open small fissures in the wood which form ■ receptacles for the rain, which, with the next sun, will be equal to hot water poured on, dissolving the gum, and causing it to be carried off" into the vacant air. And this will be more particularly the case should one or both ends be uncovered, and thus exposed to the action of the elements named (which is often the case with railway sleepers) ; and when cut from a tree of old age, with a decayed heart, when any of this canker is left on the cut timber, it will corrode and eat away the whole lump, all combined hastening its decay. The New Zealand woods are mostly evergreen, consequently the proper time to cut them down is the summer and autumn months, during which time the trees have less humidity or water in them, and are quicker dried and seasoned if cut early in the season, the gums being more concentrated and harder. (Ktirnes has the woodman when falling them in winter drank the saccharine water that runs from the heartwood, which is collected by the smallest fibrous roots through the centre of the largest ones, and spread out through the heartwood over the whole tree, forming its natural food, which sustains life. When a limb has been blown oft' or become detached by a falling tree, the rain descends the centre of the heart, and causes canker, but the tree will stand as long as any heartwood remains to conduct sustenance for its support. I have counted over two thousand rings or girdles in the diameter of a cut log, which, according to modern theory, would make some as old as the Christian era. I am therefore of opinion that two ringß are formed every year (one in the sap, the other in the heart) in our indigenous ever-green forest trees, one in the spring, the other in autumn. There being only three deciduous trees, the ribbon wood, the goai, and the shrub fuschia, the proper time to cut these is " the fall of the leaf." The white pine and the bokaka, or box wood, are bound together by a weak albuminous gum, which, if extracted, would turn sour and make acetic acid ; the red pine by a resinous gum, and the black pine by a stronger gum, all readily dissolving in warm water. They resemble lime tree, walnut, and ash as regards decay, and will not stand more than from 6 to 10 years partly in the ground and partly out, without some metallic impregnation or other preservatives, but suspended will endure variously to the extent of thirty years. 1 The totara resembles red gum and cedar for durability, and is bound together by a gum partaking of the nature of beeswax, | the blue gum, teak, and oak by a gum partaking in a measure of the nature of linseed oil, hence their various degrees of durability. Generally the more rapid 1 the growth the shorter is the tree ; the slower on sandy or clayey soil, the longer. Thus it is by having discernment to , find out the cause we can best apply the i remedy. It is not reasonable to suppose that a literary theoretical man, who sits at his desk all day long, can be well up , in these matters. To become so, he must i delve o'er hill and vale ; strain his muscles ■ with the axe, the saw (like a Gladstone), ' the pick, and the blast, and use the ) microscope. It is very rare to see theory , and practice combined. 'j If we cut an esculent root, or take off 5 part of the shell of an egg, a skin will • form on it to preserve the inside from 1 decay till its -proper time allotted by Nature. So it is with _\yood. Cut up

I into scantling, the gums harden on its surface, and form a skin by filling up the pores ; and each time that this is planed off, even at the end of twenty years, it will shrink considerably in size, till a sufficient quantity of gum comes agiin to the surface to form another skin. Thus we see how Nature performs her work, both to preserve and to decay. In the forest or bush, most of the fallen trees decay much faster than on the plain. This is owing to its excessive umbrageous humidity, excluding the air. This dampness, acting on the vegetable watery humors of the sapwood, turns sour and mouldy on all woods of weak gummy adhesiveness, soon decaying, while the strength of gum in the heartwood of totara and black pine is hardened by the cold, and in a measure petrified, to make it more durable. The precipitate decomposition of inferior woods, limbs, and branches is one of the provisions of Nature to supply the growing coniferous and other young trees with nourishment. I will have to allude to these points again when I state my remedies, describing first what art has done by the process at present in use. Hanansvale Mill, Forest Hill, March 25th, 1872.