66 THIRD REPORT ON FOREST OPERATIONS 



solve out. Some of the modes which have been adopted are in- 

 compatible with this, and are therefore so far unsatisfactory. 

 The object of Boucherie's process is to displace the fermentable 

 sap by a fluid less liable to change. His method has been 

 largely practised in France, and there favourably reported on ; 

 but subsequent experience shows that its success remains to be 

 proved. Another fact should be mentioned, that this fluid can 

 only be made to penetrate the softer woods, refusing to pass 

 through hard wood, such as fully-formed oak. Eeference was 

 made to this process in last year's summary (par. 10). A full 

 account of it is given in the Keport of the Permanent Way Com- 

 pany in London, who have adopted this method in the prepa- 

 ration of railway sleepers, using for this purpose a solution of sul- 

 phate of copper. Timber, if expected to endure, must be thoroughly 

 dried by exposure to sun and air ; this desiccation may be ex- 

 pedited by first immersing the timber in water and then drying 

 it in a current of air. The importance of ventilation cannot be 

 over-estimated ; in fact, there are instances where the dry-rot* 

 has assailed beams of wood, and been arrested by allowing a free 

 current of air to act upon it. Instead of immersing the logs in 

 water, the practice is sometimes adopted of burying them in a 

 dunghill. This is simply a modification of the steaming process, 

 by which the nitrogenous matter is dissolved out. 



The following modes of preserving timber may also be referred 

 to, viz., Sir William Burnett's process and that of Mr Bethell. 

 The former, which consists in charging the wood with a solution 

 of chloride of zinc, appears, on the whole, to be the best and 

 most practicable. It has been thoroughly tested in Her Ma- 

 jesty's dockyards, and found to withstand not only the effects of 

 moisture, but the inroads of insects and fungi. The fact that 

 insects and dry-rot are in this country the greatest enemies of 

 timber, is all in favour of the chloride of zinc. Mr Bethell uses 

 creosote, with the object of " coagulating the albumen, and pre- 

 venting putrefactive decomposition." His process has been, and 

 still is, being tested on the railway. It would be premature to 



* For details of experiments and summary of this important subject, see 

 Professor Balfour's Memoir, read at the Edinburgh Architectural Institute, 

 April 1857. 



