94 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



point of water, and keeping up that heat for forty-eight hours, 

 when the fire is withdrawn, and the oil is run off while hot, in 

 order to dry up any that may adhere to the surface of the wood. 

 The wood is then removed when cool enough to handle. 



The plant with which the writer has to do is employed chiefly 

 for creosoting fencing material (stobs and palings), every descrip- 

 tion of wood being used for this purpose. Fast grown, immature 

 wood, such as exists to a great extent in this country, lends itself 

 readily to this treatment, and becomes practically of as much 

 value as good larch. In practice, every description of wood, with 

 the exception of larch, is creosoted, all that is required being 

 a medium to hold the preservative substance. As might be 

 expected, the different species do not absorb oil to the same 

 extent, beech taking in much more than any other species, while 

 practically the whole of the other broad-leaved species absorb less 

 than the conifers. But a great deal depends on the rate of 

 growth, as open-grained wood may absorb twice as much as 

 wood that is slow grown. The degree of seasoning has also an 

 effect on the absorbent power of most species; but it is not 

 essential that the wood should be thoroughly seasoned before 

 being submitted to this process. 



The creosote used is obtained from tar distillers, and costs 2|d. 

 per gallon at the works. It has a specific gravity of not less 

 than 1008 ; and its boiling point being considerably higher than 

 that of water, advantage is taken of this fact in the system 

 described. The sawn stobs and palings being stacked conveniently 

 near the boiler, are seasoned as far as circumstances permit, and 

 treated in succession. The stobs are packed as closely as possible 

 into the boiler in tiers, beginning at one end of the boiler, and are 

 then covered with creosote as above stated, a barrel mounted on 

 wheels being iised for the conveyance of the oil from the chemical 

 works. The fire is then started and kept going until the tempera- 

 ture rises to a little above 212° R, when the moisture in the timber 

 is driven off in the form of vapour, the creosote taking its place in 

 the tissues of the wood. Besides this mechanical action, a chemical 

 change undoubtedly takes place whereby the contents of the cells 

 and intercellular spaces are coagulated and fixed, and are thereby 

 rendered less liable to attack from fungi and insects, or, in other 

 words, to decay, some of the constituents of the creosote acting as 

 an antiseptic. The effect of the process is also to prevent, at least 

 for a time, moisture from again entering the tissue. Paling rails 



