28 The Forest Pkoducts Laboratory 



in box design and proper selection of box species which has so far been 

 taken. 



Typical of various studies is the one made on hickory. A large 

 number of tests on spokes and other vehicle parts showed definitely 

 that "red" hickory was not inferior to "white" hickory in its mechani- 

 cal properties, and that grading rules discriminating against it on 

 account of color were basically unsound. Tests on larger vehicle parts 

 such as axles, bolst-^i's, and poles brought out the relative merits of 

 hickory and various substitute woods which the ever-increasing short- 

 age of hickory has forced into use. 



The relative strength of various species of wood when used as 

 telephone or other electric poles has been determined through actual 

 strength tests of a number of poles, simulating as nearly as possible 

 actual conditions in service. Several series of tests have also been 

 made upon cross arms of various sizes and species, to determine the 

 strength and proper design. 



For many years, timber cut from southern pine trees which had 

 been "bled" or turpentined was considered inferior on that account 

 and suffered discrimination. Strength tests made upon "bled" and 

 "unbled" wood showed that the turpentining had not injured the wood, 

 and enabled this material to assume its proper commercial value. 



In the Frcseroative Treatment of Woods 



The preservation of structural timbers against decay has long 

 been recognized as very desirable, particularly from the economic 

 standpoint, and the treatment of this class of material is growing. 

 There has, however, been considerable confusion concerning the effect 

 of the treatment upon the strength of the material. This has naturally 

 tended to retard the progress of the art. The laboratory has conducted 

 a series of tests upon various species of wood, treated and untreated, 

 and has shown just how much each kind of treatment has affected the 

 strength. This led to improvement in processes which were injurious 

 and to greater confidence in the strength of treated timber, besides 

 furnishing data to be used in the design of structures of treated timber. 



Wooden pihng and otlier wooden structures placed in salt water, 

 especially in southern waters, suffer severely from the attacks of ma- 

 rine borers of various kinds, and the annual loss from this one cause 



