THE COASTS OF SAINTONGE. 355 



as sulphuretted hydrogen was to the Rats, and here 

 direct experiments became necessary. A great 

 number of substances which are highly poisonous to 

 Man and to the other vertebrata, exert only a very 

 feeble action on the invertebrata, and more especially 

 on insects. Sulphuretted hydrogen, which was so 

 successfully employed by M. Thenard, is one of 

 these, and hence it was necessary to replace it by 

 some other gas. 



Owing to the kindness of M. Robillard, principal 

 apothecary to the military hospital at La Rochelle, 

 the laboratory of that establishment was placed at 

 my disposal. Freshly collected Termites were intro- 

 duced into vessels which, by way of extra precaution, 

 had been placed in large basins filled with water, 

 and I then proceeded to try the effects of various 

 gases, until I discovered that chlorine completely 

 answered my expectations. When perfectly active 

 Termites are plunged into this gas in a nearly pure 

 condition they at once fall as if instantaneously 

 killed. When left for half an hour in air mixed 

 with only one tenth of chlorine, they are found to 

 be completely asphyxiated. Experiments that were 

 repeated in several different ways, and in which I 

 tried as far as possible to imitate the arrangement 

 of the layers of wood that had been attacked by the 

 Termites, gave equally decisive and equally satis- 

 factory results. Thus, to destroy the largest Termite 

 settlement, all that is necessary is to inject a sufficient 

 quantity of chlorine. 



We are far, however, from asserting that all the 

 difficulties of the problem can be met in this simple 



A A 2 



