1847.] On Teredo Navalis, fyc. 487 



On Teredo Navalis and a natural defence against its ravages, by Mr. 

 Lehman n -.from the Transactions of the Scandinavian Naturalists 

 of Copenhagen, 1840 ; translated and communicated by Dr. T. 

 Cantor. 



Teredo Navalis, an important agent in the economy of nature, is 

 universally known by the damage it inflicts upon the wood work of 

 posts and ships. While accomplishing the intention of nature iii 

 destroying decayed wood in the sea, it at the same time attacks ships, 

 bulwarks and the piles of quays. Like all animals intended by nature to 

 clear her stage, the Teredo is endowed with immense power of repro- 

 duction, and therefore by its numbers becomes more destructive than 

 the largest animals which come in collision with the industry of man. 

 Every museum exhibits specimens of wood perforated by this shell-fish, 

 which lines its abode with lime, in composition similar to that of its 

 shells. But my inquiries as to the length of time required by the 

 animal to perforate the wood, have hitherto been fruitless. Some samples 

 of the works of Teredines are here submitted, because I am enabled to 

 attest the age of the artificers. Five years after the posts of bulwarks of 

 Kyholm were erected they appeared in the state now exhibited. From 

 these it will be seen that the Teredines, during the said period, have 

 attained to their full size, of more than 12 inches in length, and half an 

 inch in diameter. It may therefore be inferred, that they thrive, and 

 combine quick growth with great multiplication. 



The more important the works are, which are attacked by the Teredo, 

 and the quicker the destruction is perpetrated, the greater the solicitude 

 which has been exerted to defend the wood, and many applications 

 have been tried, but none have stood proof in the sea. The only 

 remedy hitherto successful, has been to cover the wood with plates of 

 metal, of copper, brass or zinc. But they are too expensive to be 

 used universally, nor are they easily protected. 



I believe to have found a defence offered by nature herself, which I 

 therefore recommend to the attention of naturalists. The pilot and 

 light vessel, placed in the North-Sea, in the mouth of the Eider, 

 requires not to be coppered, and, as she has to sail but few miles, is 

 therefore provided with a sheathing of plain boards. The Teredo 

 attacks the latter indeed, but cannot penetrate to the sides of the vessel. 



