14 



TIMIIKK HNE8 OK THK SOI TIIKU.N INITEU STATES. 



It ia clear from tlie above diagnosis 1 hat Lougleaf Pine may be distinguished from Cuban Pine 

 by its finer grain and small amount of sapwood: also that both of these differ from the Shortlcal 

 and I/oblolly in their greater weight and tin- more resinous character of their wood, but tliat the 

 wood of the two last named species is rarely distinguishable beyond doubt. 



Technically the wood of the pines (lifters about as follows: The wood of the Longleaf and Cuban 

 pines are about equal in strength, Longleaf excelling by its finer grain and smaller amount of 

 sapwood. The same comparison maybe made with regard to Loblolly and Shortleaf Pine. Being 

 much more variable, however, in weight and grain, exceptions to the general rule here art- very 

 numerous. Of the last-named species it may be said that the wood derived from more southern 

 localities is generally heavier and stronger than northern grown a fact especially apparent in 

 the case of the Shortleaf Pine. 



The extensive investigations carried on by the Division of Forestry during the last three to 

 lour years mainly on these pines permit us to give the following resumed of their mechanical 

 properties derived from not less than 20,001) tests and as many measurements and weighings. 

 We quote this information from Circular 12 of the division : 



MECHANICAL PROPERTIES. 



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,.~00,000 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 here given 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 to wood containing 15 per cent moisture, which may be 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 I'ine. 

 [Air-dry material (about 15 per cent moisture).] 



RELATION OF STRENGTH TO WEIGHT. 



Tlie intimate relation of strength and specific weight lias been well established by the experi- 

 ments. The average results obtained in connection with the tests themselves were as follows: 



