AMERICAN FOREST CONGRESS 281 



keeping them in the wood, and after the wood has been 

 rendered more or less decay or fire-proof, the protection 

 against wear must be considered. 



Successful preservation that is, preservation which 

 will pay will depend upon : 



1. The timber used. 



2. The preserving method used. 



3. How the preserving is done. 



4. The man who supervises the preserving. 



The selection of timber used should be governed by 

 the available supply. The kind of wood used is after 

 all probably the least important factor, because, when 

 preserved, the indivuality of the wood becomes more or 

 less insignificant. The longest-lived preserved timber, 

 speaking with reference to decay alone, will be the one 

 which will allow of the most perfect and even penetra- 

 tion of a preservative, and which at the same time will 

 hold such a preservative. But we not only want long 

 length of life, but also a timber which, with any given 

 treatment, will bring an increased length of life which 

 shall represent the greatest possible financial return on 

 the original investment, made up of the first cost of the 

 timber and the cost of the preservative process. It so 

 happens that the open-grained porous woods which, 

 when untreated, last but a comparatively short time, 

 give high penetration and comparatively long increase 

 in length of life ; while the denser woods, which ordi- 

 narily are called longlived, give a poor penetration and 

 a comparatively short increased length of life as a 

 result of preservation. Recent tests with timber like 

 beech and elm have shown an amazingly high absorp- 

 tion for zinc chloride, amounting to as much as .65 

 pounds of dry zinc chloride per cubic foot, using a 2^2 

 per cent solution of zinc chloride. 



It is, as has been stated, a fortunate fact that most 



