14 



TIMUEE PINES OF THE SOUTHERN UNITED STATES. 



It is clear from the above diaguo.sis that Longleaf Pine maybe distinguished from Cuban Pine 

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

 and Loblolly in tlielr greater wciglit and the more resinous character of their wood, but that the 

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



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

 pines are about equal in strength, Longleaf excelling by its hner 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 are very 

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

 localities is generally heavier aud 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 

 four years mainly on these i)ines permit us to give the following resume of their mechanical 

 properties (h^rived from not less thin 20,000 tests aud as many measurements and weighings. 

 We quote this information from Circular 12 of the division: 



MEflHANICAL PROPERTIES. 



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

 dry), soft ti> moderately hard (hard for pine), requiring al)out 1,000 pounds per square inch to indent 

 one-twentieth inch; stiff', the modulus of elasticity being from l,."iOO,000 upward; strong, re(iniring 

 from 7,000 pounds per s(|uare inch and npwai'd to break in bending and over 5,000 pounds in 

 comi)ression 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 kihi-diied 

 material ami tiie strength to wood confaining 1.5 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 etrenrilh of Southern Pitie. 

 [Air-dry niateri:il (about 15 jier cent moi,sture).] 



KELATION OF STRENOTH TO MTIIGHT. 



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

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



Transverse stronglh 



Specific weight of teat pieces. 



Cuban, i Longleaf. I Loblolly. I ShorUeuf. 



100 

 100 



91 

 94 



77 

 77 



