BOEING LIFE
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of methods which aim
the protection of timber by
armoùr of one kind or another.
Metal has been largely
used for this, steel QI iron sheathing has_been employed but
found to corrode too quickly, zinc and Muntz metal
(an alloy of copper and
giving indifferent results ;
much better are casings of cast iron or copper.
The latter.
is highly poisonous to all forms of life but is expensive and,
uniortunately, much song—ht after by thieves.
Vitried
pipe castings have been found to give excellent protection
but they, in their turn, suer from the seriousdefect that
they are easily broken.
A great number of patent amours
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of one kind and another have been put on the market but,
though they give initial protection, all break down Sooner
or later andthe wood borers enter… Concrete casings are
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largely used at the present day, especially in the United
States, and they are often— very effective but there is always
the danger that the concrete will be attacked chemical‘ly
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by the sea water Or that it will break away near the base '
oî_the pile find so allowbo'rers to effect an entrance there -
and work their way upwards,‘
An old and very effective
method consists of covering-the surface of the wood with '
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broad-headed iron nails, known as “ scupper—naing.”
The rust from the nails Spreads. and forms a complete
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coating over the
and with satisfactory eeCt._
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All these methods
effective
the»Crustacean
borers than with the Shipworm, since the former can do
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little damage unless a good deal of the surfaceis exposed
whereas a very small .unprotected area will allow come
paratively large numbers of minute larval ShipWorms to
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begin boring, and these may each pen—strate into the wood
for a depth of a foot or more,.according to the particular
species.
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The best method of protecting timber against the ravages
of the Shipworm is to impregnate it:—with. some poisônous
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