14 



TIMHKK riNKS OF THE SOUTilEKN LXITED STATES. 



It is t'li'iU' IVoin the iihovo dinfjiio.si.s that Loiigh-af I'iiie may be (listiiij^uished Iroin Cuban Pine 

 by its finer grain and small amount of sajiwood; also tliat both of these differ from tlu! Shortleaf 

 and Loblolly in their greater weight and the more resinous character of their wood, but tliat the 

 wood of the two last named s|)eeies is rarely distinguishable beyond doubt. 



Technically the wood of tlie pines differs about as follows: The wood of the Longleaf and Cuban 



I)ines are about eijual in sti-cngth, Longleaf excelling by its liner grain and smaller ai iiit of 



sapwood. The same eomparison maybe made with regard to Loblolly and Shortleaf Tine. lieing 

 much more variable, however, in weight and grain, e.\eeptions to the general iiilc hcie arc very 

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

 localities is generally heavier and stronger than northern grown — a fact esjM-cially ai)parcnt in 

 the case of the Shortleaf Pine. 



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

 four years mainly on these pines permit us to give the following rc'sunu' of their meclianical 

 l)roperties derived from not less thin :iO,OOCI tests and as many measurements and weighings. 

 Wc (juote this information from Circular 12 of the division: 



MECHANICAL PHOPKRTIES. 



In general the wood of all these pines is heavy for pine ('M to 40 pounds per cubic foot, when 

 dry), soft to moderately hard (hanl for pine), requiring about 1,()(H) jwunds per stpiare inch to indent 

 one-twentieth inch; still', the modulus of elasticity being from l,.")(i(),(>(»0 upward; strong, re<iuiiing 

 from 7,0(H» pounds per sipiare inch and upward to break in bending and over .5,(100 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 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 atreni/ III of Smillirni I'iiie. 

 (Air-rtrv material (about 15 per ceut muisture).] 



RELATION OF STRENGTH TO WEIGHT. 



The intimate relation of strength and specific weight has been well established by the experi- 

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



Transverse streoeth 



SpeclSc weight of test pieces. 



Cuban. Longleaf. LobloUy. 



100 

 100 



01 



94 



Shortleaf. 



77 

 77 



