72 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



are more abruptly separated from the spring wood. The heartwood shows a markedly darker 

 color with a reddish flesh-color tinge added. 



It is perhaps easiest to distinguish the wood of the longleaf and Cuban pines from that of 

 the shortleaf and loblolly. It is also possible to keep apart the longleaf from the Cuban; but 

 while, in general, the shortleaf and loblolly can be more or less easily distinguished by color or 

 grain, some forms of the latter (rosemary pine) so nearly resemble the former that no distinguishing 

 feature is apparent. 



The most ready means for distinguishing the four seems to be the specific gravity or weight 

 in connection with the grain. The proportion of sap and heartwood will also be an aid in 

 recognizing a log or log-run lumber in the pile. These distinctive features are tabulated as follows, 

 the figures representing average conditions of merchantable timber and mature trees: 



Diagnostic features of the wood. 



QUALITY AND ADAPTATION OF WOODS. 



The exhaustive research described in another part of this report has given a full answer to 

 this part of the inquiry. 



The longleaf pine is superior wherever strength and durability are required. In tensile 

 strength it approaches, and may surpass, cast iron. In cross-breaking strength it rivals the oaks, 

 requiring 10,000 pounds per square inch on the average to break it, while in stiffness it is superior 

 to the oak by from 50 to 100 per cent. It is best adapted for principal members of heavy con- 

 struction, for naval architecture, for bridges, trestles, viaducts, and house building. The finer- 

 grained, and especially the curly, timber is much sought for finishing wood. Its hardness fits it for 

 planks and flooring, but unless quarter-sawed it is apt to "peel out." Being very resinous, it is 

 sometimes difficult to handle in dry kilns, nor does it take paint readily; its hardness also makes 

 it difficult to work, wearing out tools and muscles. The curly grained lumber, which is found 

 quite frequently, makes an elegant finishing and furniture wood. It is an excellent fuel, and its 

 resinous products supply the world with pitch, resin, and turpentine. Contrary to common belief, 

 the tapping for turpentine was found, by a large number of tests lately made under direction of 

 this division, not to weaken but to strengthen the timber in cross-breaking and compression and 

 to increase its stiffness. (See full discussion in report on timber physics.) 



The Cuban pine, mostly known locally as slash pine, is generally cut and sold without distinc- 

 tion from the lougleaf, and its wood, if not superior in some respects, is probably not inf. ' 

 any to the latter, except as far as its coarser grain and larger amount of sapwood may iuflu ce 



