NEW ZEALAND STATE FOREST SERVICE.

LEAFLET No. 26.

A. D. McGAVOCK, Director of Forestry.

I 2th August, 19 35.

THE PROPERTIES AND USES OF KADRI

(Agathis australis) .

By ALEX R. ENTRICAN, Engineer in Forest Products, N.Z. State Forest Service.

SUMMARY. NEW ZEALAND kauri ranks as one of the most generally useful softwoods* in the world and has figured prominently in the inter­ national wood trade for over a century. In yielding flawless timber of exceptionally large size the tree is unsurpassed by any other known species, and although the extensive virgin forests of the early European occupation have been severely depleted the remaining stands are being placed under a system of forest regulations whereby a sustained yield of this valuable softwood will be assured. Owing to its evenness of texture and ease of working, to its small shrinkage and . ability to stay put, to its medium density and excellent strength properties, and to its high durability, the timber is able to meet the most exacting use requirements. Its uses range from all classes of building and general construction to ship-building; car and wagon construction, tank and vat manufacture, military bridging, the production of dairy and agricultural machinery, and to engineering pattern work, &c.

* " Softwood " is the commercial term used to distinguish the woods of the needle or scale-leaved trees, such as the true pines (Pinus spp.), rimu, silver-pine, ·&c. (Daorydium spp.), from those of the broad-leaved trees, such as the oaks ( Querous spp.), the eucalypts (Eucalyptus spp.), and the Southern beeches ( N othofagus spp.), known in contra-distinction as " hardwoods." The two terms are of no significance as regards the actual softness or hardness of the woods, and may be applied to the trees as well as to the woods derived therefrom.

• 2

THE TREE-ITS FOREST FORM AND HABITS. The kauri is the monarch of the New Zealand forests, dwarfing in stature and magnificence all other indigenous species. The mature tree yields an almost cylindrical bole with considerably less taper than most other species, with the result that, although not attaining the extreme heights of the North American redwoods (Sequoia spp.) and the Australian eucalypts, it ranks amongst the largest timber­ prodµcing species in the world. The taper usually varies between 1 in. :in 4 ft. and 1 in. to 10 ft. The maximum recorded measure­ ments are 150 ft. for ~otal height,, 106 ft. for length of commercial bole, and 24 ft. for diameter. Early botanists and others estimate the maximum dimensions at 200 ft. for total height, 125 ft. for length of commercial bole, and from 28 ft. to 31 ft. for diameter. The largest recorded bole measured 100 ft. in length and 22 ft. in diameter, containing about 30;000 cubic feet of wood, and .capable of yielding about 200,000 ft. board measurement of sawn timber, or sufficient wood to build from ten to fifteen modern six-roomed houses. Veteran trees up to 17 ft. in diameter still exist, but, except for odd specimens, the usual range of diameters in well-stocked stands of mature trees is from 3 ft. to 8 ft. Total heights likewise range between 60 ft. and 100 ft., with odd trees exceeding 130 ft., while the merchantable boles vary from 12 ft. to 60 ft. in length, with an occasional trunk exceed­ ing 80 ft. Generally speaking, the largest-diameter trees seldom yield a bole exceeding 60 ft., many less than 40 ft., while in general the very long-boled trees of from 80 ft. to 100 ft. usually range between 3 ft. and 5 ft. in diameter. The average mature tree pro­ duces a log about 35 ft. in length and 4f ft. in diameter outside bark at mid-length. ·where young-growth classes are represented in the forest the various averages for the stand are, of course, considerably lower. In its immature state the tree grows with a remarkably even­ tapering trunk carrying a short and narrow conical crown formed by a comparatively small number of short, slender branches protruding almost horizontally from the stem. As the result of a natural branch-shedding process by which the lower branches are cast off successively as the young tree increases in height, the trunk is free of the overgrown branch stubs so characteristic of most softwoods. After a prolonged adolescence of 100 years, or considerably more, the height-growth slows down and the branch-shedding process · ceases. A system of large main branches then develops from one common point on the trunk, tp.ese branches radiatiµ.g upwards and outwards until the tree takes on the shape of a feather duster. The widespread nature of the crown of veteran trees in open stands is in striking contrast to the narrow crowns in dense stands. Almost invariably all branches below the main branching system have been cleanly shed, and the subsequent growth of the trunk is such that · ultimately it appears almost free of taper. The main branches themselves take on enormous proportions, attaining a diameter of .3 ft. and more in veteran trees. Al~hough the leaves are of a glossy olive-green, the trees are sparsely-foliaged, and the ash-grey colour of the bark gives to the general appearance of the kauri forest a peculiar haziness. For a softwood the leaves are of peculiar shape and size, 3 those of the young tree being as much as 4 in. in length by ! in. in width, with acute apices, while in the mature trees the leaves are much shorter and almost egg-shaped, usually under 1i in. in length, although still from i in. to i in. in width. Both types of leaves carry distinctive parallel markings. Unlike the softwoods of the Northern Temperate Zone, kauri appears to grow almost the whole year round, the only rest period being any exceptionally dry season during the early summer months between December and February, and it is at the conclusion of this period that a second growth of leaves occurs, the normal formation taking place in the very early spring. It flowers from as early as June to as late as October, but August is the peak flowering month. The cones ripen about eighteen months later, becoming almost spherical jn shape at maturity and from 2 in. to 3 in. in diameter. The cones break up still attached to the tree, but leave no permanent axis as do the true firs, for instance. There is a good deal of popular misapprehension about cone and 'seed. In most years green cones of all sizes may litter the ground beneath the trees, and it is often stated that the cones disintegrate on the ground to shed the seed. No authenticated case is known where these fallen cones have produced ripe and viable seed; and it is certain that many of the failures to germinate kauri-seed artificially are due to collection of immature seed from such fallen cones. The true matured seed collected from ripe cones in a good seed-year germinates readily; but good seed-years are not frequent (probably the cycle is five-year to seven-year), and even in such a year the season for collecting seed from the very fugacious cones is extremely short, and the task of collecting from branch-tips on the massive head perched above, say, 60 ft. of bare cylindrical bole is no light one. The seed itself is of the usual shape of pinaceous seeds, although decidedly flat and thin, and the seed-wing (about 1 in. by "i in.) is not detachable from the seed, a factor very adverse to the preparation of a clean seed-sample according to ordinary commercial standards for seed. Even in veteran trees the bark is extremely thin, usually only from i in. to Ji in. in thickness. That of young trees is smooth and prominently marked with white bandings. Its structure is characterized by a multiplicity of resin-cells, which are the source of the "kauri-gum" of commerce. They secrete a resinous substance when the bark is c.ut or otherwise injured, thus functioning as a protection to the growing wood beneath. The freshly bled gum is referred to as " candle gum." With undue exposure of the cambium or sapwood, however, the protection is insufficient to prevent attack by the kauri platypus (Platyptts apicalis), the borings of which are fortunately strictly localized. The bark, which scales off the mature tree in large flakes as much as several square feet in area, keeps the bole free of the climbing plants so common to other New Zealand tree species. The flakes leave a characteristic ripple or wave mark on the trunk, and form· at the base of the trunk a heap of decaying matter which may attain a height of 5 ft. or more. Resin also tends to collect in the forks of the main branches, and such gum, forming in the kauri forests o::f geological times, was probably the source of the fossil gum now being recovered from old swamps which have replaced previous forests. · Resin also occurs in the ray cells, but is essentially different from the ordinary "kauri-gum" of commerce. The wobd tends to become infiltrated with such resin only when damaged, either internally by the formation of heart shakes or externally by wounds to the trunk. The tops and stumps likewise become charged with this resin when healthy trees are felled. The kauri is a shallow-:rooting species. The young tree develops a thick tap root several feet in length, but ultimately this tends to decay and the mature tree is dependent upon a system of main and secondary laterals. The main laterals, generally speaking, are com­ paratively short, irregular in shape, and of small size, proceeding obliquely downwards but seldom penetrating as deeply as the tap­ root, while the secondary laterals attain considerable length, are extraordinarily tubular-like in shape, from 1 in. to 3 in. in diameter, and even more shallow in their habits than the main laterals.

DISTRIBUTION AND SUPPLIES. The kauri is found only in the Auckland Province to the. north of the 38th parallel of south latitude. Though only scattered in the North Cape district, it occurs very generally throughout the North Auckland Peninsula, on the W aitakerei Ranges outside Auckland City, on the Coromandel Peninsula as far south as Te Aroha Mountain, and on the hilly country lying· between the Firth of Thames and the Main Trunk Railway. A few relics remain between the Waikato River and Raglan Harbour and to the south-south-west of Tauranga, the southernmost trees being recorded in the vicinity of Kawhia Harbour on the west and from Mamaku Plateau, about twenty-five miles south-south-west of Tauranga, on the east. Although not growing actually on the coast, the kauri often exists within a mile of the sea, and its altitudinal limits are from almost - sea-level to a maximum of about 2,500 ft. elevation. It is essentially a lowland species, only occasionally found above an elevation of 1,600 ft. Recent researches by Professor Evans and Dr. J. R. Hosking into the character of the coal-deposits in Southland show that the kauri was once present in that region, lending weight to the theory that the N othofagus spe

Under a low forest of manuka and towai, however, the kauri re­ generates freely together with tanekaha, miro, rimu, totara, &c., constituting a transition forest between the. open-heath stage and the kauri forest proper. As judged by existent immature stands iri various localities, it appears a spur or ridge species, but mature clumps are no less common ori wetter sites in sheltered basins, &e. Although ring-counts from virgin-grown timber vary· for individual inches from four to forty rings per inch, the average for various stands ranges from about eight to twelve rings per inch, and, as judged by young stock growing under favourable conditions, there is little doubt that with proper silvicultural management the kauri forests could be managed on a rotation of from one hundred to one hundred and fifty years. Admittedly a much longer period up to two hundred years or more would be required for the production of logs yielding wide-heart timbers, but this rotation is quite compatible with established forest practice, both softwoods in Northern Europe and hardwoods in Central Europe being regularly managed on rotations of two hundred and fifty years and three hundred and fifty years respectively. Of many hundreds of thousands of acres origin­ ally carrying kauri at the time of the European occupation, only about 35,000 acres of dense virgin kauri-stands remain, although another 25,000 acres of cut-over lands carry excellent regeneration and advance growth. lVIany thousands of acr~s of mixed kauri­ podocarp forests, both virgin and. cut-over, likewise carry small ·quantities of kauri and some regeneration, and the total visible supply of virgin commercial timber is estimated at about 300,000,000 ft. board measurement.

TYPES AND STANDS. Pure stands of kauri are largely in the nature of extensive groves with an under-story of taraire and kohekohe in the pole-stage. A kauri-taraire type is the more common, the kauri-content being fairly well dispersed with a lower intervening story qf mixed hardwoods and softwoods. In such stands taraire, kohekohe, and rewarewa are usually co-dominant, although tawa tends to replace the former towards the southern range of the kauri, while some rata and towai are always present. Miro is quite easily the most important softwood element of the second story, followed closely by ta:µekaha, while silver­ pine, rimu, totara, and matai are very scattered. Although both softwood and hardwood associates may be numerically strong, their millable content is extremely small, usually well under 10 per cent. of the total stand. Towards its upper altitudi:nal limit the kauri tends to be replaced by rimu and in its lower limits by white-pine, so that the resultant overlapping of these types gives the appearance of mixed kauri-podocarp stands in which the rimu or white-pine content may range from 25 per cent. to 50 per cent. Individual acres or even small dense groves of kauri may yield as much as 100,000 ft. board measurement per acrfj, but major forest areas seldom average above 30,000 ft. board measurement per acr:e, and rriore often below 20,000 ft. board measure:µient per acre. In such forests the percentage of overmature timber may rise as high as 50 per cent., emphasizing the urgent need of exploiting such timber before it deteriorates and of managing the forest to improve the

• 6 growth of the healthy trees and to secure re-establishment with young kauri-growth. By no other means can the kauri be preserved to posterity. Merely to fence around a few remnant virgin forests and protect them from fire is quite insufficient. The overmature trees will continue to decay and die, the healthy ones will follow suit much quicker than under proper management, and ultimately the whole of the kauri-growth will be replaced by a climax succession of taraire, &c. Proper forest-management, on the other hand, will preserve the magnificence of the kauri forest for all time and, in accordance with a recent decision, will be extended as rapidly as possible to all State-owned virgin commercial stands and cut-over forests carrying regeneration and advance growth. In mixed kauri-podocarp areas the total stands only occasionally exceed 10,000 ft. board measurement per acre, and over only about one-third of these forests does the total stand vary between 5,000 :ft. and 10,000 ft. board measurement per acre, the remaining two-thirds being below 5,000 ft. board measurement per acre. The quantity of kauri on these areas may vary between 5 per cent. and 50 per cent., or from only a few hundred feet board measurement to about 5,000 ft. board measurement. ·

PRODUCTWN AND MANUFACTURE. During its peak period of production towards the end of last century kauri was milled at the rate of well over 100,000,000 ft. board measurement per annum, of which over 40,000,000 ft. board measure­ ment was exported to Australia and elsewhere, and large amounts shipped to other portions of the colony. With the consequent rapid exhaustion of the kauri forests the annual production has steadily fallen, until, during the post-war period, it has averaged only about 17,000~000 ft. board measurement, with a peak of 23,000,000 ft. board measurement. Exports likewise have fallen to an average of only 2,000,000 ft. board measurement for the same period. The normal demand for both domestic and export requirements is now estimated to be between 5,000,000 and 10,000,000 ft. board measure­ ment per annum, but, with the exhaustion of the privately-owned forests, will eventually be reduced to less than 5,000,000 ft. board measurement. Both on account of its large size and the rough topography of many of the sites upon which it occurs, the kauri is a difficult and costly species to log. From rocky hill-sites trees have been known to somersault. several times in falling a few hundred feet into the valley below, eventually finishing up balanced on their broad, spreading, inverted-pyramidal heads. It is the one species of the New Zealand forests which can be floated with reasonable ease, and in rough country river driving has often been resorted to and the logs'ftoated long distances to the Auckland City sawmills. The streams available being relatively small and tortuous, it was often necessary to· cross­ cut the logs to short lengths and to· accumulate large volumes of wat~r behind dams towards the heads of the streams. The logs having been rolled, railed, or skidded either by bullocks or machine­ skidders into the dry bed of the stream, the dains are tripped and sufficient water liberated to sweep them dowri either to tide-water or 7 to large, floating streams, where they are gathered in booms and floated or otherwise conveyed to local sawmills or perhaps as far as a hundred miles or more to the- kauri sawmills at Auckland City. Prolonged immersion in sea-water is inadvisable owing to possible attack by the marine ship worm (Teredo navalis). In rough-river driving serious damage and large wastages may result from the "brooming" or splintering of the ends of logs, while delayed driving due to water shortages may enable the kauri weevil (Mitrastethus bi-tubercillcttus) to heavily attack the sapwood of logs. In excep­ tionally rough country the total logging losses due to shattering in felling, to brooming, &c., in driving, and to sinkages, &c., in floating, have amounted to as much as 30 per cent. Where the topography permits, transport may be effected by bush railway or by motor haulage or by various combinations of these and floating·, some kauri­ logs still reaching Auckland by the North Auckland Main Trunk Railway. Whereas, for reasons previously adduced, there has usually been a fair proportion of short logs between 12 ft. and 16 ft. in length, nevertheless some of the more important producers have made a speciality of long-length timbers, and logs up to 50 ft. are occasionally dealt with. The average log measures about 4 ft. 6 in. in diameter. Kauri is also produced from buried logs recovered from old swamps, the largest bole on record having measured 80 ft. in length and 24 ft. in diameter. Broadly speaking, the wood from such logs is weaker and less durable than that from growing trees, and if the wood is to be used under exacting conditions the purchaser should specify that " swamp " kauri is not to be supplied. It is definitely unsuitable for tank, vat, and similar exacting uses. · The kauri mills, particularly those situated on the waterfront of Auckland City, are probably the best equipped in the Dominion, possessing frame saws, modern Pacific-type benches and band-mills, band resaws, gang saws, &c., to deal with the largest logs and to produce the exceptionally large timbers for which the kauri possesses a world-wide reputation. The clean character of the kauri-log is reflected in the extraordinarily high yield secured in conversion, ranging from almost 6 ft. board measurement of sawn timber per cubic foot of small log (based on outside bark-measurements) to over 8 ft. board measurement per cubic foot of large logs, representing a loss of only 50 per cent. to 30 per cent., as compared with 60 per cent. to 40 per cent. for other species. For the domestic trade a large proportion of 1 in. stock is produced in 4 in., 4i in., and 6 in. widths for flooring, in 6 in., 8 in., 9 in., and 10 in. widths for weatherboarding, and in 5 in., 6 in., 9 in., and 12 in. widths for skirting, architraves, &c. Door-stock in 1i in. and 2 in. thicknesses includes widths of 4 in., 4i in., 6 in., 8 in., 9 in., and 12 in., while for sash-manufacture bottom rails are secured out of 4 in. by 2 in. and 4~ in. by 2 in., sills out of 9 in. and 10 in. by 3 in., mullions out of 4 in. by 3 in., transoms out of 5 in. by 3 in., jambs out of 6 in. by 6i in. by li in., stiles out of 2i in. by 2 in., and sash-bars out of 1 in. and li in. stock. Fence-palings in 5 ft. and 6 ft. lengths are cut from 6 in. by~ in. stock, :;i,nd match-lining from 4 in. and 6 in. by §-in. stock, finishing i in. in thickness. A good assortment of clear, wide inch stock, 18 in. and upwards in width, is also produced, together with similar lf in. stock for wash­ tubs, sink-tops, &c. Shorts are sold to the furniture trade and offcuts made up intO' boxes and crates. Fairly large stocks· of well-· seasoned timber in· these domestic sizes are· carried by the principal 8 producers, together with smaller stocks of ft.itches for export, although obviously these latter cannot be as thoroughly seasoned as the smaller­ sized stock kept for the local trade. Domestic stock is sawn to conform to nominal green dimensions, but the export trade is characterized by varying requirements, for excess sawing to allow for shrinkage. In 1 in. and 2 in. stock an excess of f6 to i of an inch in thickness is usually supplied, and a nominal excess of i in. in width, but with these exceptions. flitches for export are usually ordered to conform to nominal green dimensions, the purchaser adding the necessary excess to allow for subsequent shrinkage. Thus a flit.eh expected to yield timber 20 in. by 6 in. is ordered as 20~ in. by 6! in. The great bulk of the timber exported is in random width 1 in. and 2 in. stock and in large fl.itches from 12 i:n. to 30 in. in width and up to 8 in. in thickness, both the English and Australian merchants recutting to local requirements. The export trade also demands much longer lengths than the domestic, and lengths up to 50 ft. are regularly shipped. · Inch kauri will attain a shipping-dry condition of 25 per cent. moisture­ content (based on the oven-dry weight of the wood) in three months of favourable drying weather, but may take as much as six or even nine months of poor drying weather. Air-drying may be complete likewise in six months, but more often twelve months are required. The wood may be kiln-dried immediately after sawing, green inch stock being dried down to a moisture-content of 12 per cent. in from six to eight days using an initial temperature and relative humidity of 150° F. and 87 per cent. respectively and a final temperature and relative humidity of 170° F. and 52 per cent. respectively. For export involving long overseas freighting, 1 in. and 2 in. stock should be redueed preferably to a moisture-content of 25 per cent., but flitches 3 in. and upwards may safely be shipped at 35 per cent. moisture-content, the usual practice being to give such stock a minimum seasoning of twelve months under open covered storage.

GRADING. Kauri is graded on a different basis from all other New Zealand timbers. The principal grades are as follows:- First class Rough and/or pin heart IPermitting only heartwood. Shaky heart Medium class ·~ Allowing sapwood. Second class J 'Fir$t class is sound, clean heartwood free from knots, shakes, resin, pin-holes, and all other defects; suitable for all finishing purposes, joinery, sash, door, tank and vat stock, &c. Rough and/or pin heart is sound heartwood free from shakes, but permitting firm knots, resin, pin-hole, and other defects; suitable not only for construction work requiring good strength, but also for rough flooring, weatherboarding, &c. Shaky heart is sound heartwood permitting shakes, resin, knots, and other defects; suitable for general construction work where timbers. of only medium strength are required, out durability.· is of importance. · '· · · 9

Medium· is sound, clean timber allowing any percentage of sap­ wood, but otherwise similar to first class in being free from knots, shakes, &c. While generally suitable for :finishing purposes, it does not possess the same durability as the clean heartwood, and cannot be used where exacting conditions are likely to occur, such, for in­ stance, as in tank and vat construction, &c. On the other hand, it can be used for weatherboarding, interior doors, &c. Second class is defined officially as sound timber permitting sap­ wood, knots, shakes, resin, and other defects, but in practice shakes are relatively infrequent and the wood is used for rough flooring, weatherboarding and linings, for concrete boxings, for crate and box work, and for temporary construction work where durability is unimportant. Second class may also include timber containing a few pin-holes made by the kauri weevil previously referred to. An additional grade known as "dressing heart" is defined as sound heartwood permitting small knots and gum-streaks, the basic requirements, however, being that the piece is watertight and that the defects do not detract from a paint finish. Such timber is used for weatherboarding and linings. · The yield of the different grades varies widely with the log, but a stand of fair average quality will approximate as follows:- Per Cent. First .class 35 Rough and pin heart 13 Shaky heart 12

Total heart grades 60

Medium 25 Second class 15

Total sap grades 40

Grand total 100

PROPERTIES OF THE \VOOD. Physical Characteristics. The heartwood ot kauri is normally a light biscuit-brown in colour, but in trees infiltrated with resin it may vary from a dark reddish-brown to a rich yellow-brown. The reddish-brown wood is seldom, if ever, exported, being used for lower-grade purposes on the domestic markets, The wood of either a .light biscuit-brown or a rich yellow-brown colour is the most valuable. The sapwood is a light browish-white in colour. The transition from early to late­ wood is so gradual,. the difference between the two so small, and the flattened latewood cells with thickened walls so few that the growth­ rings are not sharply defined except on a very smoothly-cut cross­ section. For these reasons the normal wood· displays no sharply­ marked figure on either flat- or quarter-sawn surfaces, although on the flat-sawn surface the growth-ring figure is intensified by a difference in colour between the early and late wood, the former being definitely yellowish and the latter of a rich brownish hue. The principal distinguishing characteristic of the kauri :figure, however, is the 10 minutely flecked background made by innumerable small rays. They are __ most prominent, of course, on quarter-sawn surfaces, although quite noticeable on flat-sawn stock. There are two types of abnormal wood which are highly figured---:­ waved, cp_rly, or feathered kauri and mottled kauri. The former is the result of distorted grain arising from growing peculiarities in exposed trees, and the shot effect and natural silky lustre of the normal wood, combined with this figure, make it eagerly sought after for panelling and furniture work. The mottled wood possesses a most striking appearance, the figure consisting of dark patches of varying shapes and shades of brown set in the rich, yellow background of the normal wood. The shot-effect of the varying shades of brown and yellow within the cigar-shaped patches gives them the appearance of· candle-flames. The patches are formed by the inclusion of small pieces of bark, and generally vary from 1 in. in length by i in. in width to over 6 in. by 2 in. Occasionally small branchlets and even leaves are occluded, yielding much smaller and somewhat lighter­ coloured patches. Only a few trees, of course, contain much mottled timber, which quite often is confined to but one side of the trunk, and such trees are more common on rocky sites than elsewhere. When felled, the timber has, for a New Zealand softwood, a low moisture-content, averaging only about 80 per cent., based on the oven-dry ·weight of the wood, as compared with over 100 per cent. for rimu, totara, &c. It is largely on this account that kauri is the only New Zealand timber which floats with ease, its specific gravity of 0·48 (oven-dry weight on volume green basis) being the same as rimu and considerably higher than that of totara ( 0·41) ; whereas, in the green state, kauri averages only about 51 lb. per cubic foot as compared with over 60 lb. per cubic foot for rimu, totara, matai, miro, &c. The kauri examined for physical and mechanical pro­ perties had a range of specific gravity (oven-dry weight volume green) of from 0·39 to 0·59, but 82 per cent. of the specimens fell within the limits of 0·44 and 0·52. Specimens heavily infiltrated with resin would, of course, exceed these upper limits, but the percentage of such wood is usually small. Kauri is easily distinguished from other indigenous woods by the innumerable small rays whieh give the wood a characteristic dappled or flecked ground. Microscopically the wood is distinguished by double rows of pits in alternate arrangement on the radial walls of the tracheids, and by the large number of pits on the ray-tracheid crossfield, amounting to as many as nine or more. The rays are often heavily charged with resin. Although the timber is easily split for posts, palings, shingles, &c., it nails without splitting and with the greatest ease, and possesses excellent nail- and screw-holding properties. Likewise it saws easily, works readily under hand-tools, machines with ex­ ceptional ease, and turns satisfactorily. After being properly seasoned the wood stays put. It finishes to a surface of silky smoothness and takes both natural finishes and paints with ease. The basic pro­ perty of the wood conferring upon it this extraordinary combination of excellent working properties· is its remarkable evenness of texture. Although when freshly sawn or surfaced the wood possesses a characteristic faint odour, the seasoned timber is virtually non­ odoriferous and· non-tainting. .Ll

DurabiUty. In contact with the ground the heartwood of kauri has a life of only about ten years, although fence-posts, &c., of "gummy" kauri well infiltrated with resin may prove serviceable for much longer periods. On the other hand, it is extraordinarily durable under some of the most exacting of alternate wet and dry conditions. Its uses in this connection have included fencing, railway-sleepers, wharves, bridges, culverts, shingles, weatherboarding, sashes, framing and lining for freezing-works, &c. When properly protected by paint the "medium" grade, which permits sapwood, is quite durable for weatherboarding, &c., but is not suitable for use either in contact with the ground or when exposed to similar exacting conditions. There are numerous instances of kauri timbers having been salvaged for joinery and other purposes after giving over half a centnry of service in bridges, freezing-works, &c., enabling it to rank amongst the most durable softwoods of the world.

Physical and Mechanical Properties. Kauri ranks amongst the very strongest softwoods of the world. As its physical and mechanical properties have been determined by standard tests it is possible to compare them with the results of similar tests upon North American Douglas fir, which also possesses a world-wide reputation for strength, and with Southern Finnish pine, which is well known and widely used on the British markets.

Green. 1----,-A-i_r--dr_Y_·__ _ Propertiei>.

II Douglas I I Douglas II . Kauri. Fir So:ut~ernF11;J-msh I Kauri. Fir S~ut1!-ernFu:~msh • Pme. · j Pme . I 1

Rate of growth (rings per inch) .. J 26 14 20 Summerwood (percentage) 32 36 25 Moisture-content (percentage, based 72 36 30 12 12 12 on oven-dry wejght) Specific gravity (oven-dry, based on 0·48 0·45 0·50 0·52 0·48 0·49 volume at test) Weight per cubic foot at test (lb.) 51 38 41 36 34 35 Shrjnkage: Green to oven-dry- Radial (percentage) .. 5·0 4·6 Tangential (percentage) 6·3 7·8 8·3 Volumetric (percentage) 11·9 11·8 Static bending..:._ Fibre stress at E.L. (lb./sq. in.) .. 4,410 4,800 3 ,830 8,240 8 ,100 7,600 Modulus of rupture (lb./sq. in.) .. 7' 790 7 ,600 6 '700 113 ,070 11, 700 ,600 Modulus of elasticity (M lb./sq. in.) 1,570 1,550 1,240 1,890 11 ,920 1,640 Work t.o E.L. (in. lb./cu. in.) 0·71 0·85 . . 2·09 1-96 Work to M.L. (in. lb./cu. in.) 9·0 6·8 • • i 14·5 8·6 Compression parallel to grain­ Crushing-strength at E.L. (lb./sq. 2,770 3,.HO 2,850 4,060 6,450 5,630 in.) Maximum crushing-strength (lb./sq. 3,370 3,890 3,350 5,600 7,420 6,850 in.) Compression perpendicular to grain­ Crushing-strength at E.L. (lb./sq. 490 510 360 1,080 910 730 in.) Hardness (load to imbed a 0·444 in. ball to one-half its diameter)­ Side (lb.) 480 480 410 780 670 590 End (lb.) 530 510 440 880 760 680 Shear parallel to grain (lb./sq. in.) .. 940 930 1,220 1,140 Cleavage (lb.Jin.) 140 160 290 250 180 430 Tension perpendicular to grain (lb./sq. 130 240 180 300 300 250 in.) ______12

Tests of "swamp" kauri in an air-dry condition of 12 per cent. moisture-content indicate that in modulus of rupture in bending it is only 72 per cent. as strong as timber from growing trees, in modulus or elasticity in bending only 59 per cent., and in maximum crushing­ strength parallel to the grain 91 per cent.

UTILIZATION. The reputation of kauri for having possessed a wider range of uses than any other known softwood is due unquestionably to its remarkable combination of high durability, even texture, superlative strength, easy working and finishing properties, and ability to stay put after seasoning. Its uses during recent years have tended to decrease, but solely on account of the lower price of other woods, the tendency being to restrict it to the more-exacting uses where its extraordinary properties can command a higher price.

House and Building Construction. Until the opening years of the present century kauri was the principal building timber of the Dominion, being used not only in the Auckland Province to the almost total exclusion of other woods, but also being shipped in large quantities to most other districts in both the North and South Islands. The relative cheapness of the rimu and other woods resulting from their more general distribution has resulted in their wide substitution for the more valuable kauri. For wooden houses and other buildings there are few, if any, parts of the construction for which kauri is not the best wood avail­ able, whether it be for ground plates, beams, floor-joists, framing, rafters, weatherboarding, roof-sarking, exterior joinery, sashes and doors, flooring, panelling, match-lining, mouldings, built-in furniture, fitments, and decorative fittings. Some of the best class of houses, more especially in Auckland, of course, are still constructed through­ out of kauri, but, generally speaking, the tendency is to restrict its use to weatherboarding, to exterior joinery, including sashes and doors, and to sink-boards, wooden tubs, &c. Even in other centres kauri continues to be used for sashes and doors and for sink-boards. The most exacting conditions under which timber is· used in building work are in freezing works, and the fact that kauri has given good service for such purposes for over fifty years and has been salvaged for joinery and other purposes at the conclusion of this period is evidence of its wonderful durability. Ni:unerous houses in service between fifty and one hundred years bear further testimony to the durability of the wood.

. General Construction. For bridges and wharves, for mining and tunnelling timbers, and for constructional work of all kinds kauri is a valuable wood on account of its durability and great strength. Although specimens of:such structures still in use after many years' service testify to its value for these. purposes, the wood is seldom used for new structures qn account of the cheapness of concrete and steel construction .. 13

Ship and Boa.t Building. Kauri is one of the pre-eminent ship. and boat building softwoods of the world, first obtaining prominence in the export trade as a timber for ship's spars. In the·· days of sailing-ships it was ranked by both the Navy and the mercantile marine as the mast, spar, and decking timber par excellence, and its reputation in this respect became world-wide. It continues to be used both locally and in Australia for ship and boat construction, for spars, masts, sheathing, planking, decking, interior :finishing, and oars, and even in Great Britain small quantities are occasionally employed for the same purposes.

Furniture and Fitments. During. the vogue for light-coloured furniture kauri was widely employed, its strength and easy working and carving properties adapting it for this work, while the mottled and curly-grained wood provided veneer and panel stocks to give a pleasing contrast to the light colour of the normal wood. Even with the present fashion in period furniture its easy staining properties enable it to be used for large table-tops, &c., for which purpose the exceptionally large sizes of flawless wood render it suitable. For stuff-over furniture and for hidden framework where strength is of importance the timber is likewise favoured, shorts often being purchased for this class of use. 14

The wood was used in a similar fashion for church pews and pulpits, for seats and panelling in public buildings, and for counters and fittings in banks, shops, &c., counters, in particular, still absorb­ ing small quantities of the large flawless sizes.

Tanks and Vats, &c. For tanks and vats for the accommodation of water, beverages, chemicals, &c., kauri is amongst the most highly valuable woods in the world, being widely used for these purposes both in Great Britain and Australia as well as in New Zealand, its non-tainting properties and ability to stay put and resist acids being of basic importance. Some of the most famous beers in the Empire are brewed in kauri vats. ·Miscellaneous Uses. The miscellaneous uses for kauri are legionary. It is employed for all types of woodenware, more especially for kitchen articles, such, for instance, as cabinets, bread-boards, cutlery-boxes, trays, ironing­ boards, clothes-horses, and ladders, but also for miscellaneous turnery products such as wooden vases and bowls, serviette-rings, door, drawer, and broom handles, and for bases for electrical fittings, picture-frames, mouldings, &c. On account of its non-tainting pro­ perties, kauri was once used for butter-boxes and tallow-casks, but has since been replaced by the cheaper white-pine. It is still used occasionally for the heads of beer-barrels. Small quantities of slabs and off cuts, however, are worked up into boxes and crates, &c., its excellent nailing, strength, and working properties making the wood particularly suitable for all classes of containers. Other minor uses for kauri include butchers' chopping-blocks, pastryma~ers' tables and trays, cart and wagon floors and sides, filler-pieces for motor and bus bodywork, caskets, and coffins, &c.

Fa~rm Uses. Quite aside. from the multitudinous uses for sawn kauri on the farm, odd trees are readily converted by splitting into fencing-posts, strainers, droppers, rails, palings, shingles, laths, bridge timber, and firewood, &c., the wood splitting best by backing off.

G. H. LONEY, Government Pririter7 Wellington.-1935. [l,000 /7 /35-5649