LIMNORIA LIGNORUM. 355 
The means taken to protect the woodwork are of 
several descriptions, viz., copper sheathing; iron nails 
closely studded; (the ferruginous oxide that the action 
of sea-water produces, impregnates the wood, and forms 
a protective iron crust all over the surface ;) creosote 
and coal-tar are likewise used, and it is the opinion of 
My. Moore that all timber that can be smeared over once 
a year, is effectually freed from the ravages of the 
Limnoria. 
The action of these animals is more or less rapid, 
according to circumstances. Pinewood they appear to 
destroy about the rate of one-quarter to half an inch 
in a year: of course this must be less rapid during 
the first year or so, and more rapid after several years, 
for the numerical increase of animal life must be 
greater in proportion to time. We find that that portion 
of the pine framework that supports the hull of the 
Robust frigate, that was commenced being built on the 
31st of October, 1859, and is submerged at every tide, 
has been eaten in many places from two to three inches, 
while an inspection of the pine scaffolding round the 
half-built fort just within the Plymouth breakwater and 
harbour, erected between three and four years, shows us 
that the extent of the depredation amounts to from 
three-fourths of an inch to an inch and a half, according 
to the nature of the wood and its freedom from any pro- 
tecting influence. The little animals invariably choose 
the softer places, shunning the knots and hard lines of 
wood that longitudinally connect one knot with another. 
They likewise avoid every part of the wood that had 
been impregnated with iron, sometimes for several inches 
round the place where a nail or bolt had been driven. 
Oak they attack not so readily as pine, but still the 
former gradually falls before their persevering action, the 
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