NEW ZEALAND TIMBER.

Nelson Evening Mail, Volume IX, Issue 256, 28 October 1874, Page 4

NEW ZEALAND TIMBER.

An interestiog paper on tbe durality of New Zealand timbers has been BoppHed to the General Government by Mr Kirk. From it we extract some of the remarks which bear npon the timbers most commonly used in Nelson : — Totara. This tree is found throughout the colony, usually attaining its greatest dimensions on rich alluvial lands, or on dry hill sides of low elevation. Large specimens are fonnd north of the Waitemata, but it does not occur in abundance until after passing the southern limit of tbe kauri. Although not equal in size to the largest specimens of tbe kauri, trees are occasionally found from eight to ten feet in diameter, 4 to 6 feet being tbe average size; height 40 tO ft 7o feet. For piles for marine wbfrves and bridges, &c, it is one of tbs most valuable timbers known. In addition to its great durability, it bas tbe power of resisting tbe attacks of teredo for a considerable period, especially if driven with the bark intact, ijf is said that trees felled during the growing season will resist the attacks of teredo for a longer period than those felled during tbe winter. Although I have been unable to obtain direct evWetree in support of thie, I entertain little doubt of its troth, but fear the advantages that may be derived from this property are overrated. I have seen totara piles attacked by teredo within a year of their being driven ; bnt usually from two to four years elapse before tbey are touched, and if the bark is preserved intact, a much longer period; in fact, I bave never seen the bark of any timber perforated by teredines. • Heart of totara will r resist tbe teredo still longer. In the Auckland Museum is a section of a Tasmanian blue gum pile, taken from the wharf after having been driven for six or seven yeara. The pile is closely perforated, but heart of totara cradle sections bolted to it bave not been toothed-.. When the sap-wood of totara lias been thoroughly perforated, it sometimes happens tbat the teredo dies. oot, being unable to attack the heart-wood uutil it has been subjected for a longer period to the action of sea water, when tbe mollusc resumes possession^ and the destruction of that p_rVof the pile exposed to its ravages is a mere matter of time. Tbe fine wharf at tbe Bluff Harbor, constructed scarcely ten years ago, already shows tbe substantial totara piles in many cases perforated to the heart. Still, no other native timber, except perhaps tbe pariri, has equal power to resist the teredo. Witb regard to simple durability, the oldest totara piies yet driven in oar wharves and piers are perfectly sound, whether below the mud level or above high water mark — in short, wbere not actually exposed to the attacks of teredo. Piles driven in the Anekland Wharf bave been drawn twenty years after being driven, when the portion below tbe mud level was fresh and sound, even tbe bark undecayed; and wherever nsed for beams, girders or stringers, tbe same durability is shown, even in the oldest works, wherever good heart limber has been used. Totara piles in inland bridges exbrbitxarlier signs of decay : tbe sapwood decomposes more speedily, and appears to affect the heart. In situations of this kind, it is of great importance to /remove the sap-wood befoie tbe pile iB driven; and tbe same remark applies when totara is nsed for house blocks. Tbe heart-wood will last longer if the sap is removed before tbe pile is nsed. Red Pine. - -A* tree from 40 to 80 feet high, trunk 3 to -5 feet in diameter. Found throughout tbe eclony, but increasing in frequency from the Auckland Isthmus southwards. Tbis timber haa been extensively nsed in the construction of public works, especially in the southern parts of tbe colony, and bas hitherto had ahigher reputation for durability than it deserves. Its chief drawback arises from its liability to decay under the influence of wet. Wherever moisture can penetrate, as at joints, suncracks, shakes, or even the concavities on the surface of hewn beams, decay speedily commences, although intervening spaceß may remain sound for & considerable period. Separation of the ligneous tissue frequently takes place during growth, leaving small cavities, which become filled witb a resinous deposit. Tbis becomes shaken wheu the tree is felled, affording fatal facilities for tbe access of moifture. j White Pine. / The timber is white and tough, aoi is well adapted for indoor work, bu i will not bear exposure. In Wellingto i i aod other places it is s»id to be su bj... t to the attacks of a minute coleopteroi j insect; ie is, however, possible th. lbia ia only the case when the timber i i felled in tbe summer time and used ul a green condi.ion. There can, howJ ever, be no doubt that the timber is net in any way adapted for exposure, although it is occasionally used for general boilding purposes where kauri and totara canuot be readily procured. Uaed for house timbers, wall-platts become hopelessly decayed in three or /oar years if in contact with the ground. As weather-boarding, painted on tbi: outside, it is more durable, although ftot to be recommended for tht. purpose. Although of lighter specifio gravity, it . strength' is about equal to rimu; it, might therefore, within certain limits, be ased (or inside beams, __c, but its apparant liability to the ravages of insects will always prevent architects .0 T:?-«7 - 1 :

from recommending it to any extent. I have never seen exposed specimens of the timber attacked by insects. Contrary to what might have been expected, it appears to possess considerable power to resist the attacks of teredo. Black Bisch of Auckland and Otago, and Eed Birch of Wellington and Neison. The true black birch is a noble tree, found from Kaitaia, in the North Island, to Otago, but often Jochl aud absent from extensive districts. It aßcends the mountains from the sea level to 3,000 feet. The tree is usually from 60 to 90 feet in height, with a trunk from three to eight feet in diameter. In many districts it is abundant, and forms a large portioD of the forest. So much confusion has arisen from the misapplication of the names "black hircb," "red birch," and "white birch," that without actual examination it is difficult to say what tree may be intended in any particular instance. In many parts of tbe colony, the smallleaved tarata (Pittosporum tenuifolium) is called black birch; in others, the name is applied to the tawbero (Weinmannia facemosa) In fact, the term "birch" may be regarded as a generic name applied by buahmen to any small-leaved tree, and qualified with the prefixes " black," " white," or "red," nt the caprice of the individual or as may be suggested by the color of the foliage, bark, or timber. In Nelson it has been sparingly employed, with the next Bpecies, for marine p.lee. Mr Akareten, of Nelson, informed me that he had taken up pilesAf this species, which had been driven seventeen years, and found thereon perfectly sound except where attacked by teredo. He also stated that, in addition to Ub superior durability, it had the power of resisting the attacks of tbe teredo for a longer period. lam informed by Mr Blackett that the Waiau-ua bridge was constructed eleven years years ago entirely of this timber {Fagus fusca), and thafc on a recent close examination no trace of decay could be detected. White Birch of Nelson and Otago, Black Birch of Wellington, Canterbury, and Nelson. This tree occurs from tbe centre of the North Island to Otago, and is often found in much greater abundance than the preceding species. For fresh-water piles it is said to 'last eight years in good condition. In marine situations it is usually attacked by the teredo as soon as the bark is detached, and is often much damaged in two or three years, but will stand for ten years without requiring removal. Mr Akersten, of Nelson, is of opinion that it would stand for raOre than twenty years, if protected with copper sheathing. Piies drawn thirteen years after being driven had tbe parts exposed to the attack of teredo perforated to the centre and badly decayed : the upper and lower portions of the pile in fair condition, but not equal tc Fagus fusca under similar circumstances. Mr Thornton, engineer for tbe province of Canterbury, informed me that the first sleepers used on the Lyttelton railway were of tbis species, and that they were so badly decayed within eighteen months as to require removal. He attributed this rapid decay to their indifferent and _|ppy quality. \