16 



TIMBER PINES OF THE SOUTHERN UNITED STATES. 



In any one tree the wood is lighter and weaker as we pass from the base to the top. This is 

 i rut- of every tree and of all four species. The decrease in weight and strength is most pronounced 

 in the lirst I'O feet from the stump and grows smaller upward. (See fig. 1.) 



49.6 



43.4 



37.2 



31.0 



24.8 



10 



20 



30 

 Feet from Stump. 



40 



50 



60 



1. Diagram showing variation of weight with height of t 



This great difference in weight and strength between butt and top finds explanation in the 

 relative width of the summerwood. Since the specific weight of the dark summerwood band in 

 each ring is in thrifty growth from 0.90 to 1, while that of the springwood is only about 0.40, the 

 relative amount of summerwood furnishes altogether the most delicate and accurate measure of 

 the.se differences of weight as well as strength, and hence is the surest criterion for ocular inspection 

 of quality, especially since this relation is free from the disturbing influence of both resin and 

 moisture contents of the wood, so conspicuous in weight determinations. 



The following figures show the distribution of the summerwood in a single tree of Longleaf 

 Pine, as an example of this relation : 



