350 REPORT OF THE FOREST, FISH AND GAME COMMISSIONER. 



not infrequently a pile is so completely honeycombed interiorly (without 

 exterior evidence of unsoundness) that a slight blow would suffice to break 

 it in pieces. It is common enough for the teredo to destroy, with its 

 tunnels, from 50 per cent, to 70 per cent, of the cross area of the piece of 

 timber attacked. Fortunately, the marine wood-borers are able to work 

 upon submerged timber only between the mud line and low-water mark. 



The action of the Limnoria terebrans, while hardly less destructive 

 than that of the teredo, is chiefly upon or near the surface, so that timber 

 whiph it has weakened may be readily detected. The work of the chelura 

 closely resembles that of the limnoria. 



The principal land insect which attacks manufactured lumber is the 

 white ant, or termite, a wood-borer whose work is very destructive. It is 

 confined to southern latitudes, and is especially harmful in South America. 

 There is a black ant which infests the northern forests, and which riddles 

 wood of the pine family so as often to remove, by excavation, one-half 

 of its cubic contents, but the writer is not aware that it preys upon manu- 

 factured lumber. 



Various Preservative Treatments 



For many centuries efforts have been made to discover a suitable 

 treatment which wood could be made to undergo which would, at the same 

 time, preserve it against decay and the attacks of boring animals. The 

 number of experiments made has been legion. One writer (Paulet) enu- 

 merates 174 different processes which had been tried. From the earliest 

 times wood has been charred; and there are piles in Venice and in England 

 more than one thousand years old which seem never to have been treated 

 by any other process save charring. Apparently, the ancients had a 

 method of doing this which is now a lost art, for the results of charring 

 now-a-days are not very satisfactory. 



Later came a period when wood was coated with preservative paints; 

 and finally attempts were made to inject preservatives into the wood. 

 The painting processes and other external applications have gradually fallen 

 into disuse, as it was found that by covering the outside of timber with an 

 impervious coating the evaporation of water was stopped. This allowed 

 any chance fungus spore, which may have been on the wood before coating, 

 opportunity for rapid growth, thus hastening the destruction of the wood. 



