NOTES ON THE PROPERTIES OP WOOD. 



It occurs that a new bark grows over such wound, and in such 

 instances the evil is not detected until the stem is cut into timber. 

 Similar defects are also caused by lightning. 



As a very elaborate work upon the various kinds of oak, I may 

 mention Kotschy's Eichen Europa's, " Durability and Preservation of 

 Wood." 



Well seasoned timber will last for an indefinite period if kept in dry 

 air or under water ; but when alternately exposed to atmosphere, water, 

 and light, it begins to decompose. The ordinary causes by which this is 

 effected are chiefly the fermentation of the azotic substances contained in 

 the cellular tissue. This is developed under the influence of the oxygen 

 in the atmosphere, and by the moisture contained in the wood. We have 

 therefore the problem to find means to prevent this fermentation, either 

 by obviating all such circumstances as air and water, or to extract from 

 the wood its vegeto -albumen, or to act upon the latter in a manner that 

 it will resist fermentation, and the attacks of insects. No process has 

 yet been invented which answers all these conditions, and with all its 

 trials we must have the assistance of chemistry and entomology. 



I refer to our museums as the place where, among other rude-made 

 articles, will be found here and there a remnant of wood which bears the 

 age of decenniums, and other specimens of petrified wood which must 

 have been in existence in its natural state centuries ago. 



That wood in sandy soil will last for centuries may be seen in the 

 specimens which were dug up whilst making the new docks at Birken- 

 head, from depths varying from 8 to 32 feet below the surface, and they 

 are reckoned to have been there for centuries. 



Among the many inventions to preserve wood, those of England have 

 proved the most successful. Already in 1737 a patent was granted to 

 Mr. Emerson, for preparing timber with hot oil, and soon after the 

 method of Oxford and Kyan came into use. 



In 1837 a patent was taken out by Margary, to impregnate wood with 

 sulphate of copper ; and since 1838, Sir William Burnett's process, 

 chloride of zinc, has been in use. 



Mr. Payne obtained a patent in 1841 for preparing wood with two 

 solutions, such as carbonate of soda and sulphate of iron. Some very 

 good results are obtained with this system, but it must be done with the 

 greatest care. 



Still better is the invention patented by Mr. J. Bethell, which con- 

 sists in the injection of oil of tar after the air has been extracted. This 

 process is effective to a great extent, and for a full description I 

 refer to Mr. Bumell's paper, read before the Society of Arts in London, 

 1860. (See Vol. 8 of " Transactions," p. 554.) 



The disadvantage of the creosoting system is the offensive smell 

 and the increased danger by fire ; but it is recommendable for railways 

 and hydraulic works. 



In France, the price of creosote is too high to admit its general use ; 



