AGATHIS AUSTRALIS. 145 
ten rings to the inch as a fair average for growing timber it would give three 
centuries as the age of a tree with a diameter of 5ft. at the base. This rate of 
increase is supported by the little we know of the rate of growth of young 
trees. In the Auckland Domain trees planted twenty-two years ago are now 
a5ft. high, with a circumference of 26in., which shows greater rapidity of growth, 
but the trees are growing under very favourable conditions. Another tree planted 
twenty years ago is 2oft. high, with a diameter of only 201n. 
The wood of the kauri remains sound long after it has passed its maximum 
rate of growth; but the newly-formed wood-cylinders are very thin, while the 
immense pressure exerted by the outer cylinders consolidates the inner portion 
of the trunk, so that the number of rings to an inch is greatly increased. I have 
counted over thirty rings to an inch in some gigantic trunks, so that, assuming 
each ring to represent only a year’s growth, the age of a tree 7ft. in diameter 
must be twelve hundred and sixty years; the gigantic specimen at Mercury 
Bay, which is 80ft. to the lowest branch, and 24ft. in diameter, must be con- 
siderably over four thousand years; and the fine specimen at the Maunganui 
Bluff, which is 66ft. in circumference, would not be less than three thousand six 
hundred years. 
The kauri is remarkable for the soundness of its timber: hollow and detec- 
tive trees are more rare than in any other, native tree, and when they occur it is 
often found that the defects have been caused by some injuries received during 
early stages of growth, or from their having grown in wet situations: star- or 
ring-lags or shakes or other defects of a similar character are rare. No other 
tree has the power of retaining its timber in a sound condition so long after the 
maximum rate of growth has been passed. 
The proportion of sapwood is very small in fully-matured trees, and, as a 
rule, it is sharply defined; the wood is most deeply coloured at the heart, and 
becomes gradually lighter towards the circumference, the outer zones consisting 
of white sapwood, varying in thickness from tin. to 5in. according to the age of 
the tree and the conditions under which it was grown. Freely-growing trees, 
30in. in diameter, may occasionally be found almost destitute of heartwood ; but, 
if growing on rocky ground, trees 2ft. and upwards in diameter may often be 
found with the heartwood fully matured, and almost destitute of sapwood. 
PROPERTIES AND USEs. 
Kauri timber varies from yellowish-white to brown in colour; it is straight 
in the grain, even, compact, firm, clean, and silky, while it is of great strength, 
toughness, and elasticity. It is of extreme durability, and adapted to a greater 
variety of uses than any other New Zealand timber. It exhibits a certain degree 
of variation in colour, density, hardness, and the amount of resin it contains. 
Mr. E. Bartley, architect, of Auckland, distinguishes four varieties as under :— 
t. Red kauri, which is close-grained, resinous, and durable, the best general 
building-timber, and suitable for beams, joists, and heavy framework, but hable 
to cast and twist, shrinking longitudinally as well as transversely. 
2. White kauri: This is yellowish-white, and straight in the grain; it is very 
tough, and will bear a greater strain than the red, but is less durable ; it neither 
warps nor shrinks longitudinally if fairly seasoned before being worked up. It is 
a splendid timber for mouldings and joiners’ work, and is largely used by boat- 
builders on account of its toughness and elasticity. 
3. Black kauri: This is of a deep-brown colour, very hard, dense, and 
heavy, being charged with resin, but is difficult to work. This, however, is 
compensated for by its extreme durability. 
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