CAUSES OF DECAY AND DESTEUCTION OP TIMBER 267 
the surface and makes a hole from to f inch diameter 
and about 2 inches deep. 
An excellent sborfc and interesting paper dealing with 
these timber borers, by Mr. Charles H. Snow, M.A.Soc.C.E., 
is published in the Proceedings of the American Society of 
Civil Engineers, Vol. XL., 1898. 
So far as the author knows, there is no wood which is 
not liable to attack by the sea worm with the possible 
exception of billian from North Borneo, and that has not 
been much used, but appears immune, and some of the 
palms or similar timbers which the teredo will not generally 
attack, as the animal prefers a compact wood for its abode. 
In the paper previously referred to Mr. Walsh mentions 
turpentine as the only Australian timber which the teredo 
dislikes, and he found this timber quite sound after an 
immersion of thirty to forty years, although occasionally the 
sapwooi showed signs of attack by limnoria and sphgeroma. 
Engineers for a long while pinned their faith on green- 
heart, as it was considered that the sea worm would only 
attack the sapwood of that timber, and greenheart certainly 
resists the attack of the worm for a longer period than any 
other timber in general use, but, as has been pointed out 
elsewhere, it is now known that even greenheart only lasts 
for a limited time in places where the teredo or limnoria 
is active. 
These borers will not attack certain timbers if others 
more to their liking exist in the neighbourhood, hence the 
reason of the statements so frequently made to the effect 
that many timbers are proof against the marine worm. 
Piles standing by themselves appear to be more open to 
attack than when placed close to others. 
White Ants. Boring insects of other kinds attack timber 
all over the world. The most destructive is the termite 
