THE BAY OF BISCAY. 231 



could only destroy the vitality of these organic par- 

 ticles before they come in contact with the eggs, we 

 could at once put a stop to the further development 

 of these destructive Molluscs. 



I convinced myself by repeated experiments that 

 a twenty-millionth part of a mercurial salt, if thrown 

 into the water in which myriads of these organic 

 corpuscles were moving, would be sufficient to render 

 all of them motionless in the course of two hours. A 

 two-millionth part of the same salt produces the 

 same effect in forty minutes, and entirely deprives 

 the water of the fertilising power with which it had 

 previously been so highly charged. Without pre- 

 senting equal intensity of action, salts of copper and 

 of lead possess a similar property. To preserve the 

 submerged wood of our marine docks and wharfs, it 

 is therefore only necessary from time to time to throw 

 a few handfuls of these different substances into the 

 surrounding water. Fecundation would thus be en- 

 tirely arrested, and the eggs would perish before they 

 were developed, and consequently the species would 

 be completely exterminated in our harbours and docks 

 in the course of two or three seasons. By prevent- 

 ing the loss which is annually occasioned by the 

 Teredos the original cost of this process would very 

 speedily be more than covered.* 



* The first expense would be merely to enclose the water within 

 a circular wall, and this would obviously not be a very costly 

 process. It will, of course, be impossible for me in the present place 

 to enter into any practical details, but if everything should happen 

 on a large scale in the same manner as in my experiments, one 

 pound of corrosive sublimate, or two pounds of acetate of lead, would 



