FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



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



Diagnostic features of the wood. 



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

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

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

 denned dark-colored bands of summer wood of the ring furnish the most reliable and ready means of determining 

 finality. 



At present distinction is but rarely made in the species and in their use. AH 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, but especially since the use of dry kilns has become general and 

 tho simple oil linish has displaced the unsightly painting and "graining" of wood Southern pine is rut into every 

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

 above li by (i 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 J'KOPKRTIES. 



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 in bending, and over 5,000 pounds in compression when yard-dry. 



The values given iu 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 maybe conceived as just on the border 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). 



