INDUSTRIAL PROGRESS DURING THE YEAR 1875. cclxxxvii 



volved in the preservation of timber, contribute materially 

 toward the rational explanation of conflicting and often con- 

 tradictory results obtained in practice. This author's inves- 

 tigations lately placed before the French Academy were 

 devoted specially to the examination of the destructive ac- 

 tion which takes place in wooden railway sleepers injected 

 with sulphate of copper. It is generally held that the pro- 

 tective action of metallic salts is due to their combination 

 with the ligneous tissue, and especially with the nitrogenous 

 matter, which is rendered insoluble and poisonous to living 

 beings. This operation the author claims to be insufficient. 

 He affirms, from his studies of the action of metallic salts, 

 and especially of sulphate of copper, upon the nitrogenous 

 matter of wood, that the albumino-cupric precipitate is not 

 absolutely insoluble in water, and that it is especially solu- 

 ble in water containing carbonic acid. The nitrogenized 

 matter in wood is partly soluble and partly insoluble. The 

 soluble albuminous portion is fixed by the metallic salt, 

 which combines also with the insoluble nitrogenous matter. 

 The water, especially if charged with carbonic acid, destroys 

 and removes this metallic compound ; in proof of which the 

 author gives a number of examples, which show that the 

 copper gradually passes out of the combination and disap- 

 pears altogether, giving place to the carbonate of lime. The 

 process is explained to be as follows : The carbonate of lime 

 contained in the ballast is slowly dissolved under the influ- 

 ence of the rain-water, and penetrates gradually into the 

 wood, substituting the copper. So long as the copper re- 

 mains in its original combination, its preservative action 

 continues. The carbonate of lime is not a septic agent, but 

 it eliminates the preservative body from its compounds, and 

 restores the matter to be preserved, if not to its natural 

 state, at least to one which facilitates the access and the ac- 

 tion of destructive agents. This theory is confirmatory and 

 explanatory of the fact, long established by observation, that 

 railway sleepers, etc., are destroyed most rapidly in calcare- 

 ous soils ; and the affirmation of the imperfect insolubility 

 of the albumino-metallic precipitate, is additionally confirm- 

 ed by the fact that the injection of timbers with metallic 

 compounds has been found to afford but little protection to 

 the same where they are immersed in fresh or salt w r ater. 



