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144
The results show Karri to sink in water, Jarrah to float, and that
Jarrah absorbs more water and swells more freely than Karri. The
author calls attention to the extraordinary expansion of the creosoted
blocks. No doubt these blocks lost a great deal of creosote during
the weeks they remained in a warm room, and perhaps the pressure
they had been subjected to in the cylinder during the creosting
process in some way accounts for their greater expansion.
Considerable feeling appears to exist in Australia as to the
relative capabilities of the two woods, Karri and Jarrah, and a Commission
on the subject was appointed in 1887, which arrived at the
following conclusions:—
CONCLUSIONS ARRIVED AT BY THE COMMISSION.
1. It is very certain that the usefulness and durability of both
timbers depends very much upon the locality where grown, and the
season of the year in which it is felled. The Commission consider
that from November to May or June, or when the sap is down, is
the best time to undertake this work; this applies equally to Jarrah
or Karri.
2. From the lengthened tests and life in works to which Jarrah
has been subjected, it appears to be a timber suitable for piles in
marine structures. Karri piles, as compared with Jarrah, can
scarcely be regarded as having passed the experimental stage ; and
the Commission would suggest that a series of experiments be commenced
and continued year by year with both timbers under exactly
similar conditions, careful inspection being made from time to time,
and true records kept.
3. From the evidence appended, it appears that the advantages
of Karri over Jarrah are:—That piles can be obtained of greater
lengths, straighter, they drive better and resist a heavier strain. For
the superstructure of bridges, jetties, &c., or where severe strains or
crushing weight has to be considered, Karri, in consequence of its
greater strength (see appended Tables), should be preferred and used
before Jarrah.
4. It does not appear from the evidence before the Commission
that there is much to choose between the two timbers as far as their
anti-resisting properties are concerned.
5. From the evidence before the Commission, and the appended
Tables of Tests, we are of opinion that Karri is most suitable for
works of construction, railways, and public works generally ; but as
regards the timber resisting the action of salt water and sea worms
in marine works it has yet to be proved.
6. It appears, from structures that have been examined, and
from the evidence taken, that, as a general rule, round piles should
be used in preference to square, and they should be charred and
tarred before being driven.
(Signed) Clayton T. Mason, M.Inst.C.E., Chairman.
William Rogers, M.Inst.C.E.
Fred Stafford, M.Inst.C.E.
H. Ernest Parry, Assoc.M.Inst.C.E.
James Gardiner, Assoc.M.Inst.C.E.
Joseph Harris, J.P., Inspector of Forests,