RESEARCH IN FOREST PRODUCTS 277 



and wood specialists in co-ordinating their work and in carrying the 

 study into the woods. These combined or co-ordinated studies and 

 experiments not only influenced naval stores practice but they put into 

 the hands of the forester knowledge by which he may manage longleaf 

 pine forests with more profit and less damage to the growing timber. 



This interdependency of research in forest products and silviculture 

 may be further expressed by considering our expanding fund of knowl- 

 edge with respect to the mechanical properties of wood. On the sur- 

 face this data does not appear of great concern to foresters engaged in 

 forest administration or silvicultural research. They have long recog- 

 nized, to be sure, that various species of wood possess special prop- 

 erties which have earned special values in the lumber market. These 

 values have, in turn, reflected themselves in stumpage values by species, 

 that is, the special properties have been recognized broadly as common 

 to the species rather than to the character or quality of the wood. And, 

 until quite recently, variability within the species has been given either 

 minor consideration or no consideration at all. Oak has stood for 

 strength, hickory for toughness, mahogany for pleasing effect, cedar 

 for durability, ash for bending, and so on. 



We have now, however, entered upon the era of selection for quality 

 within the species, properly recognizing that the poorest of our com- 

 mon species may produce some material stronger than the weaker pieces 

 of clear sound oak and tougher than some pieces of clear hickory. From 

 several hundred thousand strength tests of 126 different species, re- 

 search has definitely determined that there is a direct relation between 

 the specific gravity or density of wood and its strength properties.^ 

 This relation holds approximately true regardless of species, the dens- 

 ity of wood substance being so nearly constant that for any species 

 density or specific gravity of the wood may be taken as a measure of 

 the amount of wood substance contained in it. 



With this fundamental information, it was possible to draft definite 

 and reliable rules, not merely for determining the mechanical prop- 

 erties of wood in general, but for comparing various species and select- 

 ing the species and material within the species best suited for specific 

 purposes. In place of trade names designed to indicate strength and 

 quality, such as "longleaf" and "shortleaf" yellow pine, for example, 

 which often had no reliable or technical basis or significance, it was 



1 "The Relation of the Shrinkage and Strength Properties of Wood to Its 

 Specific Gravity," by J. A. Newlin and T. R. C. Wilson, July, 1919. 



