109 
RIGHT USE OF PRESERVATIVES. 
prevent this absorption of water from the air. Painting and varnishing are 
preservative processes; but we apply them only to the exposed surfaces, the 
concealed surfaces being unprotected and very often without ventilation. If 
concealed as well as exposed surfaces were thoroughly brushed with preservative, 
and fiesh, clean air admitted to them, decay would be either wholly prevented or 
indefinitely retarded. 
Anyone who has watched the demolition of old wooden buildings will know 
that the parts where decay has made most progress are floors that have been placed 
too near the ground and badly ventilated, outside walls where defects in the 
v eatherboarding have admitted driving rain, and inside linings that have consisted 
mainly of sapwood. Rafters, if of inferior wood, have also sometimes perished. 
The conclusion one comes to is that dampness and stagnant air have been 
responsible for most of the mischief. The assumption that the use of preservatives 
would remedy all this is fallacious and misleading. The function of preservatives is 
not to make good the defects in building construction, but to anticipate and 
supplement the skill and good judgment of builder and joiner. There is really 
no such thing as dry rot ’, that which is so called being due to fungi that derive 
their moisture partly from the wood and partly from stagnant air. Merulius 
lachrymans, or weeping Merulius, is mentioned as the most malignant member of 
the evil group. 
Fence posts and electric wire poles present another aspect of the wood decay 
problem. They are subject to the disadvantage of being inserted in the ground 
for part of their length, but against this is the compensating advantage of standing 
erect. In most kinds of soil the extreme bottom of a post or pole is beyond the 
reach of bacteria or fungi. The extreme top catches moisture and is liable to slow 
decay, but may be easily protected by a dressing of paint or bitumen. The 
seriously vulnerable part is the neck from a foot or more below the surface of the 
ground to six inches above. In Europe and America necessity has long compelled 
the use of softwoods and inferior hardwoods for these purposes and also for 
railway sleepers. Defect in natural durability has there been met to an increasing 
extent by treatment with preservatives, tar oils entering most largely into the 
remedies. Even such perishable timbers as poplar and willow are made available 
for fence posts by being saturated with creosote. 
In New Zealand the situation has so far been widely different. For a long 
time we had our totara and puriri; and when these began to fail we were able to 
turn to Australia for supplies of highly durable hardwood. All over this Dominion 
electric wires are now being carried by these wonderful poles from Australia. 
The experience of fifty to sixty years has proved, moreover, that we can abundantly 
produce Eucalyptus poles of medium natural durability in our own country. 
Preservative treatment of softwoods will become increasingly important as the 
years pass; but the most urgent need just now in New Zealand is a reasonably cheap 
and effective method for obtaining maximum durability from the eucalypts. Over 
a wide range in Australia and Tasmania there are in progress experiments that 
may be expected ere long to give us a workable formula for solving this problem. 
Meantime it seems safe and desirable to offer a few suggestions. Eucalypts 
intended for poles should never be felled until sufficiently mature; but, on the 
