TEREDO. 163 



of iron formed by the nails in the interstices between 

 them (unless they are very closely driven in so as to 

 completely cover the piles) is superficial and liable to 

 scale off*. I have known the Teredo bore through a 

 pile which was supposed to be protected by large broad- 

 headed nails in the usual way. At Christiania, in April 

 1863, I found that Teredo navalis was very destructive 

 to the woodwork in the harbour, and to boats lying at 

 anchor in the fiord. The chief engineer told me that 

 all the piles had been thoroughly creosoted (10 lbs. 

 to the square foot) before they were driven in, but not 

 to much purpose. Some were taken up while I was 

 there, and proved the correctness of his statement. 

 They had evidently been well saturated with creosote, 

 and yet were full of the ship worm. It seems that 

 these piles had been fixed only two years preAdously. 

 Another remedy that had been tried at Christiania con- 

 sisted in covering the outside face of the piles with 

 fascines of brushwood. This may partially succeed, by 

 excluding the light and warmth of the sun, and con- 

 sequently preventing the production or development of 

 the organisms on which the Teredo feeds. It certainly 

 does not love the cold shade. The maxim " obsta 

 principiis " is particularly applicable to the present case. 

 If we can succeed in preventing the young Teredo from 

 commencing its burrow, the wood is impregnable to its 

 attack. It is not difficult to bar its entrance when the 

 whole body is not the size of the smallest pin's head, 

 the foot almost microscopical, and the shell a mere film. 

 In this state it insinuates itself between the fibres of the 

 wood on the outside ; and having once gained a footing, 

 it works its way, slowly but surely, into the interior, 

 where it becomes snugly lodged and irremovable. It 

 is indeed a most troublesome guest ; and a line from 



