NOXIOUS AND VALUABLE ANIMALS. 355 



and piers of bridges are cut off, and canal locks are rendered inefficient 

 by them. Dr. Coldstream observes, that he is not aware that they 

 ever attack floating timber, but confine themselves to fixed timbers. 

 They are, however, abundant on the under sides of timber floating in 

 timber-docks, which, to be sure, is confined, though floating. 



They select their station below low-water mark, though some few 

 rise so high as to be left by the tide a portion of the time. Tf they 

 have access to the end of the timber, they enter the soft portion be- 

 tween the annual, hard rings of wood, and seldom pass out of the cir- 

 cle which they first enter. Their numbers are so great, that no one 

 penetrates more than an inch from the surface before the whole tim- 

 ber is occupied and crumbling behind him by every wave that chafes 

 it. Such as cannot enter the ends of the timber, attack the sides and 

 burrow just beneath the surface. The whole surface is soon furrowed 

 by them, so that the remains of circle after circle are washed away. 

 It has been found that where the Limnoria is abundant, timber, hov/- 

 ever large, will lose an inch in diameter annually. A timber in the 

 dock of Mr. Aspinwall, near Winnisimmet Ferry, which was once the 

 mast of a frigate, has been reduced to a mere spar of about a foot in 

 diameter. 



The animal is probably no less abundant here than about England 

 and Scotland, where its ravages have been so troublesome. I have 

 observed them at low tide, about all the wooden structures which I 

 have examined in the neighbourhood of Boston. It therefore becomes 

 a matter of consequence to know how to guard against them. 



No very economical or effectual method of protection has yet been 

 ascertained. Casings of copper have been used in some instances ; 

 but the animal has succeeded in getting behind it. Various washes 

 have been applied; and it is said that verdigris paint is effectual. The 

 most efficient method hitherto tried, has been to cover the whole sur- 

 face with broad-headed nails, set close together. 



These little creatures, which force themselves upon our notice by 

 the ravages they commit on private property, or works of great public 

 utility, are nevertheless not without their use. A very trifling portion of 

 their whole number interfere with the works or the possessions of man. 

 The great multitude is employed in devouring and disintegrating sub- 

 merged timbers, which would otherwise remain almost imperishable. 

 In this respect they correspond to the wood-boring larvse and beetles 

 of the land. "Let us consider, for instance, how possible it is that 

 large masses of wood, floated down by rivers, might accumulate on 



