208 Teredo navalis and Limnoria terebrans 



mooring ground. This vessel lately required repairs, and was 

 for that purpose grounded, when it was found that although 

 the copper of the bottom of the vessel had been extended to 

 the sides of the keel, yet the under part, which was unprotect- 

 ed, was eaten out from end to end, to the depth of 6 or 8 in- 

 ches by this animal ; the portion of keel may now be seen 

 in possession of Mr. W. Moore, of Plymouth, who executed 

 the repairs ; this gentleman also informs me that several years 

 ago he lost a piece of oak plank in Catwater, which was dis- 

 covered three years afterwards, at a very low tide, sticking in 

 the mud, and which in the mean time had been nearly eaten 

 out by the gribble. 



Proceeding to the western part of the harbour, we again 

 meet with the Limnoria, and upon making inquiries of Mr. Ro- 

 berts, the builder, and the other officers of the dock yard, I find 

 that both species of animals, known to them as the auger 

 worm and gribble, have for the last 30 or 40 years been found 

 occupying the underwater woodwork all round the yard, where 

 unprotected by iron nails, or copper sheathing. The inner 

 piles of the jetties not being protected, exhibit marks of the 

 destructive effects of the Limnoria ; large beams of timber 18 

 inches square have been entirely eaten through. About twelve 

 months since the south jetty was observed to be sinking, which 

 was found to arise from the same cause, and the jetty was 

 taken down and a new sea wall erected. The old piles are now 

 lying in the yard, where the ravages of the Limnoria may 

 easily be examined. The animal occupies nearly all the sub- 

 stance of the piles under water, even to several inches below 

 the surface of the mud ; the repairs of the different jetties are 

 still going on, and every day presents some fresh instances of 

 the destructive efforts of this diminutive animal. 



This day (December 12), accompanied by Mr. Churchward, 

 I made an examination of the whole of the building slips, 

 jetties and piles, round the dock-yard, and found that the 

 south building slip, which was floored 23 years ago, under Mr. 

 C.'s superintendance, with four inch oak plank, is now entirely 

 honeycombed, between high and low water mark, by the Lim- 

 noria, the sensation on walking over it beirig like that of 

 treading on wet sponge ; the piles of the south, north, and 

 pitch-house jetties are also all occupied by it, and are now 

 about to undergo repair. Mr. Churchward informs me that 

 the woodwork of the outer wall of the mast-pond, where there 

 is the deepest water, is chiefly occupied by the Teredo; and he 

 states, that from the operation of both causes, even the piles 

 protected with iron or copper, require renewal about every 9 or 

 10 years, the animals having insinuated themselves under the 



