268 



FOREST PRODUCTS 



3. Ability to resist spike pulling and lateral displacement of spikes. 

 This is of such importance that many railroads are contemplating the 

 use of screw spikes to replace the ordinary nail spike. Hard, dense 

 woods, as oak, maple, beech, etc., are much superior to soft-fibered woods 

 such as cedar, western pine, spruce, cypress, etc., for this purpose. 



4. The wood must be of sufficient strength to withstand the strains 

 due to center binding. Practically all woods used for ties meet this 

 requirement. On weaker species, center binding will cause checking and 

 splitting which may become serious and require renewal with new ties. 



5. Available in sufficient quantities and reasonably inexpensive. 

 Locust, mulberry, osage orange and other woods make excellent ties, but 



r«W'i 



Photograpli ty U. S, Forest Scnlce. 



Fig. 70.— "Peeler'' or bark spud used in removing the bark after the tree trunk has been 

 "faced" and before it is sawed or chopped into tie lengths. 



do not grow in sufficient quantities. Walnut, hickory and cherry make 

 good ties, but they are too valuable for this purpose. White oak has risen 

 so rapidly in price that, although still fairly abundant, railroads are 

 being forced to use inferior and cheaper woods after treatment with some 

 preservative. 



The above considerations apply largely to ties intended for use in the 

 untreated condition. If the ties are to be treated, the principal requisite 

 quaUties are: 



1. Strength. 3. Permeability. 



2. Hardness. 4. Availability and inexpensiveness. 



