74 
VIII. Operation of the Teredo Navalis on Colonial Timber. 
By Sir W. T. Denison, F.R.8., de. [Read 18th 
November, 1850.] 
In attempting to form an estimate of the cost of constructing 
and maintaining a range of wharves, whether along the 
sea-coast exposed to the action of salt water as at Hobart 
Town, or upon the banks of a river where fresh water can 
only operate upon them as at Launceston, one great element 
in the account will always be the relative duration of the 
materials which the engineer may have at his disposal ; whe- 
ther such materials be exposed to merely the common causes 
of decay, namely, the action of the air or the water, with the 
ordinary wear and tear of the structure of which they form a 
part, or to some local and peculiar action,—such as, in the 
case of timber, the destructive agency of the Teredo navalis 
and other worms. 
One of the principal difficulties which is met with at the 
very threshold of an investigation into the duration of dif- 
ferent kinds of material is the absence of a sufficient body 
of facts upon which any opinion can be formed; and, in 
order to remove this difficulty, it is most desirable that a 
permanent record should be made of any well-established 
facts which can bear upon the subject. 
It is the peculiar province of Societies like this which I 
am now addressing to store up and record all useful infor- 
mation ; and it is a wish to contribute in some small measure 
towards the performance of this part of the functions of the 
Royal Society, which has induced me to lay before the 
