94 USES OF COMMERCIAL, WOODS OF THE UNITED STATES. 



Breaking strength (modulus of rupture). 5,730 pounds per square inch, or 

 36 per cent that of longleaf pine (Sargent). 



Factor of stiffness (modulus of elasticity). 616,000 pounds per square inch, 

 or 29 per cent that of longleaf pine (Sargent). 



Character and qualities. Light, soft, not strong, brittle; annual rings nar- 

 row, due to slow growth ; summerwood narrow, not conspicuous ; resin passages 

 numerous, large, prominent ; medullary rays numerous, thin ; color light brown, 

 the thick sapwood nearly white, or slightly tinged with red. 



Growth. Height, 25 to 40 feet ; diameter, 8 to 12 inches, though much larger 

 in favorable situations. 



SUPPLY AND USES. 



Knobcone pine is not a valuable timber tree. It sometimes is cut 

 for fuel and has a few minor uses about ranches and mines, but it 

 is too small and too scarce to become important. It grows in dry 

 mountain regions in Oregon and California, and in exceptionally 

 favorable situations yields small saw timber or good-sized mine 

 props. Like the jack pine of the Lake States, it is short lived, even 

 when no accident overtakes it, but it usually falls a victim to fire. It 

 prepares for an early death by producing cones when from 5 to 8 

 feet high. Miners once called the tree hickory pine, not because the 

 wood was tough like hickory, but because it was white. A difference 

 of opinion exists as to its toughness, some claiming uses for it on ac- 

 count of that property, while others say the wood is brittle. The lat- 

 ter quality is indicated by the tests which have been made. The cones 

 are so persistent that not infrequently the tree is unable to crowd 

 them off, and they become embedded in the wood. The cones seldom 

 open to release the seed, and a tree may retain the accumulated crops 

 of nearly its whole life, which may amount to 3 or 4 pounds of seed. 

 Then a fire kills the tree, the cones open, and the wind scatters the 

 small black winged seeds upon the bared mineral soil. Seedlings 

 must have light, however, or they will not last long, and this charac- 

 teristic has given the tree the names " sun-loving pine " and " sunny 

 slope pine." Although the fuel value of the wood is very low, more 

 is used for fuel than for any other purpose. 



BRISTLECONE PINE (Pinus aristata). 

 PHYSICAL PROPERTIES. 



Weight of dry wood. 34.7 pounds per cubic foot (Sargent). 



Specific gravity. 0.56 (Sargent). 



Ash. 0.3 per cent of weight of dry wood (Sargent). 



Fuel value. 75 per cent that of white oak ( Sargent ) . 



Breaking strength (modulus of rupture). 9,100 pounds per square inch, or 

 57 per cent that of longleaf pine (Sargent). 



Factor of stiffness (modulus of elasticity). 1,032,000 pounds per square inch, 

 or 49 per cent that of longleaf pine (Sargent). 



Character and qualities. Wood moderately light, soft, not strong, very nar- 

 row ringed, compact; grain fine and usually twisted; summerwood thin, dark- 



