INDIRECT INJURIES CAUSED BY INSECTS. 239 



both surfaces as closely as possible, barely half an inch 

 of solid wood is left ; and though its progress is slower 

 in oak, that wood is equally liable to be attacked by it. 

 If this insect were easily introduced to new stations, 

 it might soon prove as destructive to our jetties as the 

 Teredo navalis to those of Holland, and induce the ne- 

 cessity of substituting stone for wood universally, what- 

 ever the expense : but happily it seems endowed with 

 very limited powers of migration; for, though it has 

 spread along both the South and East Piers of Bridling- 

 ton harbour, it has not yet, as Mr. Lutwidge informs 

 me, reached the dolphin nor an insulated jetty within 

 the harbour. No other remedy against its attacks is 

 known than that of keeping the wood free from salt- 

 water for three or four days, in which case it dies ; but 

 this method it is obvious can be rarely applicable a . 



How dear are their books, their cabinets of the va- 

 rious productions of nature, and their collections of 

 prints and other works of art and science, to the learned, 

 the scientific, and the virtuosi ! Even these precious 

 treasures have their insect enemies. The larva ofAglossa 



* In order to ascertain how far pure sea water is essential to this 

 insect, and consequently what danger exists of its being introduced 

 into the woodwork of our docks and piers communicating with our 

 salt-water rivers, as at Hull, Liverpool, Bristol, Ipswich, &c., where 

 it might be far more injurious than even on the coast, I have, since 

 December 15th 1815, when Mr. Lutwidge was so kind as to furnish 

 me with a piece of oak full of the insects in a living state, poured a 

 not very strong solution of common salt over the wood, every other 

 day, so as to keep the insects constantly wet. On examining it this 

 day (Feb. 5th 1816) I found them alive; and, what seems to prove 

 them in as good health as in their natural habitat, numbers have esta- 

 blished themselvesin a piece of fir- wood which I nailed tothe oak, and 

 have in this short interval, and in winter too, bored many cells in it. 



