2 24 transactions of royal scottish arboricultural society. 



The Creosoting ok Spruce, Larch, Oak, and Scots Pine. 



Office of the Engineer in Chief, 



General Post Office (West), London, E.G., 



\yh January 1 904. 



My Dear Sir, — In further reference to your letter of the 

 ist instant, I beg to say that in speaking of Baltic whitewood, 

 when giving evidence before the Committee on British Forestry, 

 I referred to common spruce, or Norway spruce as it is often 

 called ; and I was speaking of round, not square timber. As 

 you will doubtless be aware, this timber is very largely imported 

 for pit-props, which are classified by the timber importers as 

 " whitewood mining timber," or " redwood mining timber," as the 

 case ma:y be, but no doubt it is sometimes mixed with silver fir. 



If Norway spruce could be creosoted, it would be particularly 

 suitable for telegraph poles, as it is usually very straight and 

 shapely, and we have, consequently, from time to time endeav- 

 oured to creosote it ; but even when the timber has been 

 seasoned many months, and put under the greatest obtainable 

 pressure, say 80 lbs. to the square inch, the creosote has not 

 penetrated more than half an inch below the surface of the 

 wood. Mr Havelock says : " Spruce takes the creosote worse 

 than any timber I know ; " and by this I understand that his 

 experience is the same as my own, viz., that the creosote can 

 only be injected to a very limited extent. Spruce, so creosoted, 

 would be more durable than untreated timber, but it would have 

 a very short life as compared with properly creosoted redwood. 



I believe that in the case of all timbers which do not readily 

 take creosote, the difficulty is due to the structure, and if you 

 have a microscope available, it will give me great pleasure to 

 endeavour to obtain for you sections of redwood, larch, and 

 spruce, mounted as microscopic slides, showing the difference in 

 the structures. 



Of course, creosoting is very much a question of degree. It 

 is my experience that to satisfactorily creosote timber, about 

 10 lbs. of oil per cubic foot should be injected: oak and red-fir 

 will very readily take this quantity, or a much larger quantity, 

 whereas larch and spruce, which only absorb creosote to a depth 

 of about half an inch, will take from 2\ to 6 lbs. of oil per cubic 

 foot, according to the age and growth of the timber — and this 

 quantity is insufficient to thoroughly preserve it. 



