'
structures,
the
problem still remains unsolved.
HOW —=
urgent the need for a Solution
be judged by the extent ’
of the damage done in San Francisco as the result of a
great burst of activity by the Shipworm in that district ;
between 1914 and 1920, when wOoden piers and wharves'
to the estimated value of ten million dollars were destroyed.
Innumerable remedies and protective measures have
been tried with varying degrees of, but never complete;
==
success.
Different "woods vary with regard to the speed
Η
With which they are attacked.
Hard woods, such as teak :_
or oak, are attackédjust as quickly as softer woods, but
some woods resist attack for a. longer period owing to the :_
presence in them of essential cils of poisonous alkaloidè.
Greenheart and Eucalyptus are examples.
One of thé
methods of pr0tecting timber consists of leaving the bark …
intact,
this often contains such protective oils.
Thé
wood, however, requires very careful
the bark ‘
is injured and the wood borers make their
through ']
the daniaged places. =-In arly case there is always thé
_
danger that the animals will enter about the kn0t‘s in
:
.
='w00d. ‘
-»
*
.,
"
‘
‘“'_
'—
Ï‘IthiS impôsSible‘her6 t‘o domore than give a list
a”few' ’
, important
"of
timber'. :
measures fall naturally into two m”aîn divisions,
those which " protect—the surface of
w0od and" those
'
—
Which? impregnate
Piles have'been paintèd
with a great varietÿof substances in thehopébf keepig_
outlborers;
maybe mentioned tar, copper
paints, and
preparations. These are
.
e‘fèaç‘iQs; whileÏthè *caaînga'remainsiaœ which
:iclthè caséagof‘ pre:
continually being
J_
=
by
Chartihg orf“xbreamingïîî
‘
e
-
*
oft1mbei‘lSanotheroldmethodof prefeccm;
“
‘
«
1‘Ï:
”
'
'
\