WHARF CONSTRUCTION, SYDNEY HARBOUR. XXXVII. 
about 18 inches down from the tenon were more or less 
decayed through the lodgement of organic matter in the 
crevices. If this had been prevented by weathering the tops 
of the piles or covering them with metal caps, it is probable 
that even this small deterioration would not have taken 
place. Apart from destruction by marine borers, ironbark 
piles, if protected at the head might be awarded a probable 
‘life of from 60 to 70 years. I exhibit a section cut from one 
of these piles. The sample shows no deterioration whatever 
after its immersion for 48 years in salt water. 
Borers.—Having now described at some length the 
behaviour and durability of various piles examined in 
Sydney Harbour, a brief notice of the piles greatest 
enemies, the borers, may be of interest. In Sydney Harbour 
there are at least three kinds of borers which destroy 
unprotected timber piles. First in importance on account 
of the rapidity of its work, is the Teredo or ship worm. It 
attains to a considerable size, and when it fastens upon a 
class of timber to its taste, completely riddles it in a very 
short time. After the ship worm come the Limnoria and 
the Sphaeroma, the former is about the size of a grain of 
rice and bores the wood out into a minute honeycomb. It 
appears to have a decided predilection for soft wood, and 
is not a very serious menace to the timbers usually used 
for piles. The Sphaeroma is a larger creature, and in no 
way resembles either of the other borers. It does not 
appear to eat into the wood very deeply, but rather erodes 
the surface into small depressions which eventually run 
into one another. In time, with the assistance of the 
Limnoria, it would undoubtedly fret a pile right through, 
I think it is owing to the action of this creature on the 
surface that the Teredo holes become eventually visible, 
because the opening to a Teredo hole upon the surface is 
very small and not readily noticed. For further informa- 
