New Zealand Times. WEDNESDAY, OCTOBER 7, 1874.

New Zealand Times, Volume XXIX, Issue 4227, 7 October 1874, Page 2

New Zealand Times. WEDNESDAY, OCTOBER 7, 1874.

A valuable State paper on the subject of the durability of New Zealand timbers, the best season for falling timber in New Zealand, and on the New Zealand teredo, was presented to Parliament last session, but it does not seem to have attracted much attention, although so much was said about the forests of the Colony. It was drawn up by Mr. T. Kirk, and was the result of a resolution of the House passed as long since as October 22nd, 1872. By this we do not mean to say that there has been delay. On the contrary, a perusal of the paper will show that its compilation has been necessarily a work of time. As yet, it is but the commencement of one Mr. Kirk hopes to furnish, when experiments are concluded that have been initiated respecting the strength of the timber with which our forests abound. But, commencement as it is, it supplies some very valuable information. The Committee that recommended it should be drawn up was one that was appointed to report upon Colonial Industries ; and, in view of the large amount of money proposed to be expended on public works it was considered desirable that a reasonable sum of money should bo expended in settling what timber would be found most durable if employed for,' sleepers under the earth, piles under water, or for buildings subject only to atmospheric influences. Very likely suah information was possessed by a few experienced builders and contractors throughout the Colony ; but now it will be available for the general public. The purchaser or builder of a house may find out whether its wood-work is likely to decay in five years or twenty—information that it is to his advantage to obtain. Wo are not to suppose that the Government has not had a very clear idea what the durability of certain timbers probably would be, whilst constructing so many telegraph lines, railways, and bridges; but the information now to hand will be important, if it but serves to render assurance doubly sure. New Zealand is a Colony especially fortunate in the character of the timber it possesses. It is softer and much more readily worked up for numberless purposes than the gum-trees which abound throughout Australia and Tasmania. For mere building purposes this is not of great consequence, as a steam saw-mill will soon reduce a log of gum, cedar, or jarrah to so many feet of timber ; but there is no timber in Australia of the general value of the Auckland kauri.

There ia no instance in Western Australia, notwithstanding the just value of the jarrah forests, of a single tree cutting £SOO worth of timber, as a kauri tree is reported in the New Zealand Handbook to have done. This Colony does not produce the satinwood of the Northern Territory ; nor the, sandal-wood of the Spice Islands ; but it grows timber in abundance which serves the purpose of that exported all over the world from the shores of the Baltic. Foremost, of course, stands the kauri, although it is not considered by Mr. Kirk to be equal in value to the puriri. But the kauri is worked up very easily, and it is very durable. There are houses built of it in the Bay of Islands thirty years ago, and the boards show no signs of decay. The upper timber of the Auckland wharf was of it, and now, after eighteen years' wear, it is in good condition. Many of the timbers of the Wynyard Pier were found sound, after twenty-three years' service. It lasts three times as long, under heavy wear and tear, as Tasmanian blue-gum. Under ground it will, apparently, last as long as heart of oak. An extensive forest of it was buried, at some remote period, near Parakura ; and timber dug up from this, perfectly sound, has been used for sleepers on the Auckland and Waikato Railway. But it is not adapted for piles, as directly the bark has decayed it is attacked by the teredo. Next to the kauri for general use ranks the totara, and it is found throughout the Colony. In point of strength it is not equal to the kauri, but it is of almost equal durability, and has the advantage of resisting for a considerable period of time the attacks of the teredo. Below the surface, and above the water-mark, it has been found perfectly sound after twenty years' service. The red and white pines are not considered by Mr. Kirk to be very desirable for use on public works, but both are well adapted for the manufacture of furniture, and for being cut up into boards. The black pine, on the contrary, seems to be very valuable for all purposes, a 3 is also the miro, called in Otago the black pine. The tanekaha, cedar, and tea-tree appear to be about equally valuable, but the tree of trees is the puriri, which is not found south of a line drawn from the East Cape to the Stony River. It is a sort of New Zealand teak, greatly valued for its durability and strength, and the teredo will not touch it. Descriptions of twentythree other sorts of timber follow in the paper that of the puriri ; but the above will give a slight idea of the labor Mr. Kirk has put into the work that was committed to his care.

A scarcely less important portion of the paper than that which describes New Zealand timbers, and their qualities, is that which shows why, although timber of a proper description has been used, it has not proved as durable as was expected. This may have arisen from six causes, viz., in consequence of trees having been felled during the growing season; the timber having been used immediately after being felled ; the trees having been felled before the heart-wood was sufficiently matured ; the use of defective timber, whether sappy, shaky, laggy, worm-eaten, or soft, from having grown in unsuitable situations ; defectivo workmanship, no care having been taken to exclude rain from imperfect joints, exposed hewn beams being left with a concave upper surface so as to retain rain, &c, &c. ; or the application of paint, tar, &c, to the surface, while the timber is in |an unseasoned condition. We can quite understand that, in consequence of the demand,- timber has been improperly felled and used ; but this is a reason why the State should undertake the management of forests. There have been scores of houses built in Wellington recently, of green, unseasoned timber, and for it to last as it would do under other circumstances a miracle must take place. Mr. Kirk reports that the "disadvantages attending winter work in the bush have led to the anomalous fact that by far the larger portion of timber used in New Zealand is felled during the spring and summer months ; and this has given rise to the erroneous idea that some of our best timbers— the kauri, totara, and others—season imperfectly, contracting in length and breadth long after they are used. Except, possibly, with white pine grown in swamps, there is not the slightest valid foundation for such a statement : the shrinking has arisen solely from the use of summer-cut timberworked up while in an unseasoned condition. Exactly similar results would attend the use of the best European and American timbers under similar circumstances." And he recommends that "the timber required for public works of any extent, should be selected in the forest by some competent person, so that unsuitable timber, whether defectivo from having grown in situations not naturally adapted for the particular kind required, or from not having arrived at maturity, might be rejected at the butset. Also, that all timber should be deprived of its sap either by simple exposure to currents of air while protected from rain, by desiccation, or by infiltration with some preservative solution." Of course, it was not Mr. Kirk's business to point out that this part of his report concerns private people as much, relatively, as it does the Government ; but few persons will read his reporc without coming to the conclusion that they had better build with seasoned than with unseasoned timber. Respecting the time at which it should be felled, he says that evidently there is a vast diminution in the activity of arboreal growth during the winter months; and that there can bo "no question that, even in the warmest parts of the Colony, the circulation of the sap in trees is in a much less active condition in the winter season than in the summer, and consequently that the durability of the timber felled in the winter is much less likely to suffer from the process of fermentation than that felled during the spring or summer months." No timber, says he, should be felled before April and later than July, except in the case of kauri, which in many situations may be felled from March to June. Much, however, might be safely left to the judgment of a skilled forester. Timber resists the action of the teredo better if felled in winter than in summer.

An interesting description of the New Zealand teredo is appended to the paper we have been alluding to. This little animal, which is a post to any description of pine wood when placed under salt water, differs slightly and but slightly, from its brothers and sisters in other parts of the world. What it is elsewhere has been shown in tho Scientific American for July, and hero it is described as having "a worm-like body, terminating on the exterior in two siphonal tubes, one of which takes in water containing food and air, the other serving for tho discharge of the minute particles of wood which, the animal is continually excavating. Tho animal lives in a tubo from a few inches to two feet in length, and sometimes half-an-inch in diameter at the inner extremity, excavated in timber exposed to the influence of salt water, and invariably lined with shelly matter.

The outer extremity of the tube is scarcely larger than the head of a pin, and the body of the animal is attached just within'its mouth in such a way that it can be slightly protruded at pleasure." It will eat through blue gum piles fifteen to twenty inches in; diameter, Quebec oak, and. red birch, when under water, completely honey-combing' them in a few months. But it cannot get through bark or, we believe, any pulpy substance. It does not work below 105 feet deep, but at that depth it did eat through the planking of the s.s. Taranaki, when wrecked in Tory Channel, so that when she was raised it was found,unsafe to walk the decks till they were covered with planks. As a rule, the insects are considerably careful not to bore into each other's tubes, and when they do so they soon die. After the wood is well bored, another little insect —a crustacean —takes rjossession in countless numbers, and soon reduces the timber to a mere mass of spongy tissue. Mr. Kirk thinks that a solution of silex with muriate of lime as a wash, might be of use as a preventative, but saturations of creosote and metallic solutions are no defence. The best remedy is, however, to use only heart timber, and have all exposed parts covered with copper sheathing. This remark does not apply to piles made of puriri, which, when used, never have been known to have been perforated by teredines.