CROSS TIES 293 



Species Length of Life in Years. 



Cypress 9~*4 



Elm, white 3-5 



Fir, Douglas 6-9 



Gum, red 3-4 



Gum, black 2-4 



Hemlock, eastern 2-3 



Hemlock, western 4- 7 



Hickory 2-5 



Larch, western 6-8 



Locust, black 12-20 



Maple, hard 2-4 



Oaks, white -. . . 7-1 1 



Oaks, red 3- 6 



Pine, loblolly 2-4 



Pine, lodgepole 2-5 



Pine, longleaf 6- 9 



Pine, shortleaf 3-5 



Pine, western yellow 4- 7 



Pine, white 3- 6 



Redwood 8-14 



Tamarack 6-9 



THE PRESERVATIVE TREATMENT OF TIES 1 



It is estimated that in 1915 over 37,000,000 ties or nearly 30 per cent 

 of all those used that year were treated by some artificial means to pro- 

 long their life. About 80 per cent of all wooden materials subjected to 

 preservative treatment are cross ties. 



The principal preservatives are coal tar creosote and zinc chloride, 

 the former being used in humid or non-arid climates and the latter in 

 the semi-arid regions of the West. (Zinc chloride leaches out of the wood 

 in regions of medium to heavy rainfall.) Sometimes a combination of 

 both is used (Card process). 



Cross ties are almost wholly preserved by the so-called pressure treat- 

 ment, that is, the ties are loaded on trucks and run directly into long 

 cylinders or retorts where steaming or vacuum may be applied and then 

 the creosote oil is forced into the wood fibers under pressure until an 



1 For further information regarding timber preservation, see "The Preservation of Struc- 

 tural Timber," by H. F. Weiss, Annual Proceedings of the American Wood Preservers' 

 Association, and various publications of U. S. Forest Sen-ice on the subject. 



