136 The Teredo, or Shipworm. [ February, 
Certain kinds of wood are less subject to their attacks than 
others. The tree palmetto of the Southern States, it is said, is 
never bored by the shipworm, and some of the Australian woods 
have similar immunity. Dr. Mueller says of the Eucalyptus mar- 
ginata (Smith): “ The Jarrah or mahogany tree of S. W. Austra- 
lia, is famed for its indestructible wood, which is attacked neither 
by Chelura nor Teredo nor Termites, and therefore so much 
sought for jetties and other structures exposed to sea water, also 
for underground work, and largely exported for railway sleepers. 
Vessels built of this timber have been enabled to do without cop- 
per sheathing. It is very strong, of a close grain and slightly 
oily and resinous nature; it works well, takes a fine finish, 
and is by shipbuilders here considered superior to either oak, 
teak or indeed any other wood.” * * * The Æ. rostrata 
(Schlecht), the red gum of Victoria, is another very valuable spe- 
cies for the “ extraordinary endurance of thewood underground, 
and for this reason highly valued for fence-posts, piles and rail- 
way sleepers ; for the latter it will last a dozen years, and if well 
selected much longer. It is also extensively used by shipbuilders. 
* * * Next to the jarrah from S. W. Australia, this is the 
best wood for resisting the attacks of seaworms and white ants. 
This species reaches a hundred feet in height.” 
In some of the seaports in different parts of the world there 
are small crustaceans that assist the shipworms in cutting away 
what wood the Teredo may leave. These little fellows resemble 
the wood-louse (pill bug), and cut either way of the grain of the 
ood. 
In the inlets around Puget sound the destructive action of both 
classes of animals may be seen, especially about the time of the 
summer solstice, when the extraordinary fall of the tide exposes 
the piles (of the wharves) for their entire length. A space meas- 
ured up and down on the piles for a length of four or five feet, 
including the portion exposed between ordinary tide marks, may 
be seen which is so completely riddled that it would seem as if 
the slightest loading of the deck of the wharf would result in a 
tumble down of the whole. 
The wood-eating crustaceans referred to belong to the groups 
Limnoria and Chelura. 
As an offset to the damage caused by these, from point of size 
insignificant animals, it should be borne in mind, to their credit, 
that by destroying old wrecks, &c., in channel ways and at the 
entrance to harbors, they contribute to the safety of navigation. 
It is stated also that the operations of the Teredo suggested to 
Mr. Brunel his method of tunneling the Thames. 
