THE TEREDO AND ITS DEPREDATIONS. 551 



Harlingen, Stavoren, and Nieuwendam, and afterward in the ports of 

 Nieuwe-Diep and Stavoren. The woods employed were oak, red fir, 

 ordinary fir, and Pinus sylvestris, generally in pieces one metre long 

 by two or even three decimetres square. These blocks were prepared 

 in different ways, and care was taken to place by their side blocks of 

 the same kinds of wood without any preparation as counter-proofs. 



The trials made by the commission may be placed under three prin- 

 cipal groups : 



1. Coatings applied to the surface of wood, or modifications of the 

 surface itself. 



2. Impregnation of wood with different substances, which modify 

 the interior as well as the surface of the wood. 



3. Employment of exotic woods, other than ordinary woods of con- 

 struction. 



Coatings applied to the Surface op Wood. The methods be- 

 longing to this group, which have been examined by the commission, are 

 the following : 



1. Method invented by M. Claasen, and kept secret by the inventor. 



2. Metallic paint, invented by M. Claasen and likewise kept secret. 



3. Method of M. Brinkerink, consisting of a mixture of Russian 

 talc, coal-tar, resin, sulphur, and finely-powdered glass, applied hot on 

 wood previously roughened by a toothed instrument ; this application 

 was two millemetres thick. 



4. Method of M. Rijswijk, analogous to the preceding. 



5. Paraffine varnish, obtained by the dry distillation of peat, from 

 the factory of MM. Haages & Co., at Amsterdam. 



6. Coal-tar, applied cold on the wood in several successive layers, 

 or applied hot on wood whose surface had been previously carbonized. 

 Some pieces were treated as follows : Holes were first bored in them 

 and filled with tar, then plugs were fitted closely to the holes and driven 

 in with sufficient force to make the tar penetrate the wood ; other 

 pieces still were painted over with a mixture of tar with sulphuric acid, 

 or sal ammoniac, or turpentine, or linseed-oil. 



7. Painting with colors mixed with turpentine and linseed-oil 

 among others with chrome-green or with verdigris. 



8. Singeing or superficial carbonization of the wood. 



The pieces of wood thus prepared were placed in the water at the 

 end of May, 1859, and the first examination, made toward the end of 

 September of the same year, showed that neither of these methods af- 

 forded any protection from destruction by the teredo. There was one 

 partial exception, and that was the pieces of wood treated according to 

 No. 6 ; these showed only traces of the teredo here and there. But, 

 at a later examination, in the autumn of 1860, when the wood had been 

 exposed a year and a half, these were also fcund to be equally severely 

 attacked by the teredo. 



The results of these experiments strongly convinced the commission 



