XXXIV. H. D. WALSH. 
and has until recently, contained a considerable amount of 
sewage matter. It has been my experience that where the 
salt water is fouled to any great extent with sewage such 
as used to be the case at Woolloomooloo and at the head 
of Darling Harbour, before the low level sewerage scheme 
was brought into use, there is little or no danger to be 
apprehended from marine borers, as they do not seem to 
be able to live in water contaminated by sewage, although 
it is well known that the Teredo is more destructive in 
clean brackish water than in pure salt water. I recently 
drew some turpentine spring piles at the Circular Quay, 
driven twelve years ago; apart from a few Teredo holes 
in the sapwood, the timber was otherwise quite sound, and 
I used the piles again in the same position. The water in 
the vicinity used to be impregnated to a considerable 
extent with sewage matter. Apart from destruction by 
marine borers, turpentine piles are very durable and might 
be awarded a life of from 30 to 40 years. 
From these and similar experiences which as you see are 
based on the test of a good many years, it appears certain 
that turpentine piles, unsheathed, are able to resist to a 
reasonable extent the attacks of marine borers in the 
latitude of Sydney. A little further north and in the 
Tropics I have no such faith in their immunity. 
I have often remarked that of the total number of tur- 
pentine piles in a wharf, several, (say about 10%) will suffer 
badly from attack by marine borers, sometimes to the 
extent of complete destruction, while at the same time the 
others remain practically untouched. There are several 
possible explanations of this, amongst which I suggest the 
following :— 
(1) A pile driven when green may conceivably, by retain- 
ing its sap, resist marine borers more effectually 
than one driven when dry. 
