348 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OP AGRICULTURE. 



The following diagnosis may prove lielpful in the distinction of the wood: 



Diagnostic features of the tvood. 



Name of species. 



Specific gravity of kiln-/Possiblo range 



dried wood. jMostfrequentrange 



Weight, pounds per cubic foot, kiln-dried 



wood. (Average) 



Character of gram seen in cross section .... 



Color, general appearance 



Sap wood, proportion 



Uesin 



Long-leaf pine (Pinus 

 palustris Miller). 



.50 to. 90 

 . 55 to . 65 



36 

 Eine and even ; annual 

 rings quite uni- 

 formly narrow; on 

 large logs averag- 

 ing generally 20 to 

 25 rings to tlie inch. 



Even tlark reddish 

 yellow to reddish 

 brown. 



Little; rarely over 2 to 

 3 inches ot radius. 



Very abundant; parts 

 often turning into 

 "light wood;" 

 pitchy throughout. 



Cuban pine (Pinus 

 heterophylla (Ell) Sud). 



. 50 to , 90 

 . 55 to . 70 



37 

 Variable and coarse, 

 rings mostly wide, 

 averaging on large 

 logs 10 to 20 rings to 

 the inch. 



Dark straw color with 

 tinge of flesh color. 



Broad , 3 to 6 inches . . 



Abundant, sometimes 

 yielding more pitch 

 than long leaf; 

 "bleeds" freely, 

 yielding little 

 scrape. 



Short-leaf pine (Pinus 

 echinata Millei). 



. 40 to . 80 

 . 45 to . 51 



30 



Very variable; me- 

 dium, coarse; rings 

 wide near heart, fol- 

 lowed by zone of 

 narrow rings; not 

 less than 4 (mostly 

 about 10 to 15) rings 

 to the inch, but 

 often very fine 

 grained. 



Whitish to reddish or 

 yellowish brown. 



Commonly over 4 

 inches of radius. 



Model ately abundant, 

 least pitchy; only 

 near stumps, knots, 

 and limbs. 



Loblolly pine (Pinus 

 tceda Linn.). 



.40 to. 80 

 .45 to .55 



31 

 Variable, mostly very 

 coarse; 3 to 12 rings 

 to the inch, gener- 

 ally wider than in 

 the short leaf. 



Yellowish to orange 

 brown. 



Very variable, 3 to 6 

 inches of the radius. 



Abundant; more than 

 short leaf, less than 

 long leaf and Cuban, 

 but does not " bleed ' ' 

 if tapped. 



The sapling timber of all four species is coarse grained, that of loblolly exceeding the rest in this respect. 

 The grain varies most in the butt, least in the top, is very fine in the outer portions of all old trees. Loblolly in the 

 center of the log frequently shows rings over one-half inch wide, and timber averaging eight rings to the inch is 

 not rare, while short leaf will average 10 to 15 rings to the inch. The greater or less proportion of the sharply 

 defined dark-colored hands of summer wood of the ring furnish the most reliable and ready means of determining 

 quality. 



At present distinction is hut rarely made in the species and in their use. All four species are used much alike, 

 although differentiation is very desirable on account of the difference in quality. Formerly these pines, except for 

 local use, were mostly cut or hewn into timbers, hut especially since the use of dry kilns has become general and 

 the simple oil finish has displaced the unsightly painting and "graining" of wood Southern pine is cut into every 

 form and grade of lumber. Nevertheless, a largo proportion of the total cut is still being sawed to order in si/es 

 above 6 by 6 inches, and lengths above 20 feet for timbers, for which the long leaf and Cuban furnish ideal material. 

 The resinous condition of these two pines make them also desirable for railway ties of lasting quality. 



MECHANICAL FUOPERTIES. 



In general the wood of all these pines is heavy for pine (31 to 40 pounds per cubic foot, when dry); soft to 

 moderately hard (hard for pine), requiring about 1,000 pounds per square inch to indent one-twentieth inch; stiff, 

 the modulus of elasticity being from 1,500,000 upward; strong, requiring from 7,000 pounds per square inch and 

 upward to break iu bending, and over 5,000 pounds in compression when yard-dry. 



The values given in this circular are averages based on a large number of tests, from which only defective 

 pieces are excluded. 



In all cases where the contrary is not stated the weight of the wood refers to kiln-dried material and the 

 strength of wood containing 15 per cent moisture, which may be conceived as just on the holder of air-dried 

 condition. The first table gives fairly well the range of strength of commercial timber. 



Average strength of Southern pine. 

 Air dry material (about 15 per cent moisture). 





Compression strength. 



Bending stiength. 



Tensile 

 strength. 







With grain. 



Across 

 grain. 

 3 per cent 

 indenta- 

 tion. 



At rupture 



modulus „ ,~4~ 

 2bh* 



At elastic 

 limit 



modulus 

 3 W,Z 

 "2 bh> 



Elasticity 



(stiffness) 



modulus 



3 Wl* 



4 A bk* 



Relative 

 elastic 

 resili- 

 ence. 





Name. 



Average 

 of all valid 



tests. 



A\ erago 

 for the weakest 



one-tenth 

 of all the tests. 



Average 

 ot all valid 



tests. 



Average 

 tor the weakest 



one- tenth 

 of all the tebts. 



Shearing 

 stiength. 





Absolute 



Rela- 

 tive. 



100 

 87 

 83 



75 



Absolute. 



Rela- 

 tive. 



100 

 87 

 82 

 74 



Absolute. 



Rela- 

 tive. 



Absolute. 



Rela- 

 tive. 





Cuban pine — 

 Longleafpine.. 

 Loblolly pme . . 

 Shortleaf pme . 



Lbs. per 

 sq. inch 

 7,850 

 6.85C 

 6,500 

 5,900 



Lbs. per 

 sq. inch. 

 6,500 

 5, 650 

 5,350 

 4,800 



Lbs. per 



sq. inch. 



1,050 



1,060 



990 



940 



Lbs. per 



sq. inch. 



11, 950 



10, 900 



10, 100 



9,230 



100 

 91 



84 



77 



Lbs. per 

 sq. inch. 

 8 750 

 8,800 

 8 100 

 7, 000 



100 



101 



92 



80 



Lbs. per 

 sq. inch. 

 9,450 

 8,500 

 8,150 

 7,200 



Lbs. per 

 sq. inch. 

 2, 305, 000 

 1, 890, 000 

 1, 950, 000 

 1, 600, 000 



In. -lbs. 

 per cu. m. 

 2 5 

 2.3 

 2 25 

 2. 05 



Lbs. per 

 sq. inch 

 14, 300 

 15, 200 

 14, 400 

 13,400 



Lbs. per 

 sq. inch. 

 680 

 706 

 690 

 688 



