98 BULLETIN OF THE 



Mr. A. B. Johnson then presented to the Society* a communica- 

 tion 



ON SOME PECULIAR RAVAGES OF TEREDO NAVALIS. 



This communication was discussed by Messrs. Antisell, Dall, 

 Gill, Harkness, and White. 



Mr. Antisell called attention to the fact that the existence of 

 the Teredo, as well as that of other destructive mollusks brought 

 to our harbors by shipping, along our entire coast is well known, 

 and that, in view of this fact, it is a matter of surprise that provi- 

 sion was not made for guarding against this danger. To this it was 

 answered by Mr. Johnson that the wharf was a temporary one, being 

 only needed for three months, and that, although the presence and de- 

 structive powers of the Teredo were recognized by the Board, it did 

 not appear that in any previous case the destructive action of 

 the Teredo was so «rapid as to render special precaution necessary 

 in this case. Upon a question from Mr. Harkness it was asserted 

 by Mr. Johnson that a pile, examined on September 15 by divers, 

 and found sound — chips cut by divers from the pile under water 

 were found unbored by the Teredo — broke down on September 19, 

 thus indicating a destruction of a pile in four days. 



The accuracy of the observation of September 15, that the chips 

 were unbored, was questioned by Mr. Dall, who asserted that the 

 Teredo in its youngest stage attacks the wood, and that the hole 

 made is at first very minute, and is gradually enlarged and deep- 

 ened as the mollusk grows. So that a pile which appears sound on 

 the surface may, in fact, already be seriously injured by Teredo bor- 

 ings. In San Francisco Bay the work of destruction of piles by the 

 Teredo, and their renewal goes on continually, aud it is estimated 

 that a complete renewal of all the piles in the bay occurs every 

 seven years. The mollii6k works and breeds the year round in 

 waters above a temperature of 60° F. It attacks the hard woods, 

 as lignum vitse, quite as readily as softer woods, but the destruction 

 in such case is less rapid. Such woods, however, as palmetto, con- 

 sisting of bundles of tough fibres interspersed with soft or spongy 

 material, are only slightly, if at all, injured. 



Mr. Gill called attention to the fact that the Dutch Commis- 

 sioners, appointed in consequence of the great ravages of the Teredo 

 on the coast of Holland in about 1859, found creosote the best pre- 



