196 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



first size, 500 bolts of peeled rods of other sizes, and 100 bolts 

 of unpeeled rods of the "small" size. With these 600 bolts, 

 5000 baskets are made for use on the farm. The average 

 weight of a bolt of peeled rods (in August) is 56 lbs., and of a 

 bolt of " small " rods 28 lbs., the total yield being at the rate 

 of 2 tons 7 cwts. per acre. 



The accounts for 1905 showed a net revenue of ^15, 7s. 8d. 

 per acre. 



29. Teredo navalis and other Sea-Worms.^ 



By LlEUT.-COLONEL Bailey. 



Wood immersed in fresh or in brackish water, or even in 

 polluted sea-water, is not exposed to attack by these pests ; 

 indeed, by prolonged immersion in such water the tissues 

 become harder and more durable, as is proved by the present 

 condition of the piles in Venice, and of timber which has long 

 lain buried in peat. Knowledge of the practical indestructibility 

 of timber thus used led to the erection at Venice, Amsterdam, 

 and hundreds of other places, of vast and enormously heavy 

 buildings, resting entirely on piles driven deep down into the 

 water-laden soil ; and results have in all cases justified the 

 confidence with which timber has been employed under such 

 conditions. 



But wood immersed in pure and fresh sea-water is far from 

 enjoying a like immunity ; ships, boats, piles, dock-gates, 

 sheathings of quays, and other structures which remain in 

 prolonged contact with such water, being exposed to attack by 

 certain animals which, boring into them, riddle them by their 

 galleries, ultimately, and often very rapidly, rendering them 

 completely useless. The only such animals which are of 

 practical importance in this connection are Teredo navalis, a 

 very destructive mollusc, the most serious attacks by which 

 occur in sea-water of high salinity, which is also warm and 

 pure ; and two crustaceans, Lhnnoria terebrans and Chelura 

 terebrans, which are almost as formidable as the Teredo, and 

 which attack all species of timber, though they prefer soft 

 species. 



During recent years, the port of Marseilles has suffered 



^ Summary ol Invasion dii Taret dans le port de Marseille, par Monsieur E. 

 Henry. 



