71G JOURNAL OF FORESTRY 



Creosote Treatment of Jack-pine and Eastern Hemlock for Cross- 

 ties. Bulletin 67, Dominion Forestry Branch. Department of the In- 

 terior. Ottawa, Canada. 1919. Pp. 24. 



The main value of this investigation lies in the development of a new 

 process of impregnation. The principal native timbers used for tie 

 purposes in eastern Canada at the present time are, in order of impor- 

 tance : Jack-pine (Piniis banksiana) , eastern cedar {Thuja occiden- 

 tal is) .eastern hemlock (Tsnga ca)iadensis),t2Lma.r2Lck (Larix laricina), 

 and the several species of eastern spruce (Picea sp.). In addition, 

 smaller amounts of hardwoods are used, the most important being 

 birch, maple, and beech. 



The life of untreated jack-pine and hemlock ties in the main track is 

 estimated at 7 and 6 years respectively. While no difificulties were 

 found in impregnating jack-pine, and with a two-hour pressure period 

 and an absorption of 13.6 pounds of creosote per cubic foot in the 

 average, a fairly satisfactory, although somewhat erratic, penetration, 

 averaging ^ inch, was secured, hemlock proved refractory, and even 

 in a six-hour pressure period the penetration was quite unsatisfactory, 

 slightly over j4 inch, with 23.2 pounds absorption. 



Then, following up a suggestion coming from Austria (see Forestry 

 Quarterly, Vol. X, 749), the process of making small holes in the sur- 

 face of the timber to facilitate penetration and distribution of preserva- 

 tive was developed. Various methods of making the incisions were 

 invented ; finally, an incising machine with knifelike projections (like 

 the rounded tip of a table knife) was found the most satisfactory. 

 "The incisions used were relatively long and very narrow and were so 

 made that the disturbance to the fibers of the wood was very slight, 

 and so that the incisions closed up after treatment and were barely 

 noticeable. The arrangement or spacing of the incisions was found to 

 be of great importance. Suitable arrangement permits of uniform dis- 

 tribution of the preservative throughout the treated zone in a relatively 

 short period. 



"These incisions, as distinct from round or other holes or perfora- 

 tions, present to the direct action of the preservative a much larger 

 surface for penetration across than with the grain, thus somewhat 

 compensating for the fact that wood is much more easily penetrable 

 with than across the grain, and enabling a much more uniform distri- 

 bution of preservative to be obtained than can usually be secured in 

 ordinary practice. It was also found that by incising timber in this 

 way every unit in a charge showed satisfactory penetration. 



