BORING LIFE
151
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therefore, they resemble all the wood borers with the
exception of the remarkably, specialized Shipworm which
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is unique amongst borers in its inability to make a new
burrow if removed from the one it originally constructed,
and its capacity to extract
from; the substance into which it borès. ‘'
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Besides being attacked- by animals, rocks, surprisingly
enough, are also bored into by sea weedsl
Here again
it is only limestone or other calcareous rocks Which are
attacked, and the plants appear to prefer the harder
which, by their action, are soon reduced to a
friable mass coloured blueor greenish owing tothe weed
everywhere present in its substance. Their preference
for calcaredüs rocks is due to the fact that, like the Date—
mussel, they bore by'chemical means, transforming the
hard carbonate of lime which composes the rock into the
soft,, powdeiy, White bicarbonate. Besides rocks they
attack the
of molluscs, doing great damage to the
oyster
in the Bay “of; Sebastopol in the Black Sea "
_
where they are especially common. _Theÿ.attack in the
same regions the shells of barnaCles, the calcareoustubes
of -_worms and the external limy skeletons of other marine
of which are_coloured by their presence. _ Their
prevalence in the Black Sea, where they are common in all
depths down to about 75 feet, is a serious economic problem .
on account of_the damage they do both to stone work and
animal life…
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PROTECTION OF TIMBERŸ
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The problem of the protectionof timber from the attacks
of marine borers has vexed mankind since the
the
earliest wooden ships and harbour Works.
To—day, though
the advent of steel
_
ships and concrete
works
has led to & greatreduction in the use of timber inmadne
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