18 



TIMBKR PINES OF THE SOUTHERN UNITED STATES. 



That these statements refer only to tho clear portions of each log, and arc variably affected 

 at rach whorl of knots (every 10 to 30 inches) according to their size, and also by the variable 

 amounts of resin !ii|> to 20 per cent of the dry weight), must be self-evident. 



Sapwood is not necessarily weaker than heart wood, only usually the sapwood of the large- 

 si/ed trees we are now using is represented by the narrow-ringed outer part, which was formed 

 during the old-age period of growth, when naturally lighter and weaker wood is made; but the 

 wood formed during the more thrifty diameter growth of the first eighty to one hundred years 

 sapwood 'at the time, changed into heartwood later was even as sapwood the heaviest and 

 strongest. 



RANGE OF VALUES FOR WEIGHT AND STRENGTH. 



Although the range of values for the individual tree of any given species varies from butt to 

 top, and from center to periphery by 15 to 25 per cent, and occasionally more, the deviation from 

 average values from one individual to another is not usually as great as has been believed; thus, 

 of 56 trees of Lougleaf Pine, 42 trees varied in their average strength by less than 10 per cent 

 from the average of all 56. 



The following table of weight (which is a direct and fair indication of strength), representing 

 all the wood of the stem and excluding knots and other defects, gives a more perfect idea of the 

 range of these values : 



Range of specific weight tritli age (kiln-dried wood). 

 [To avoi<l fractions the valued are multiplied by 100.] 



Though occasionally some very exceptional trees occur, especially in Loblolly and Shortleaf, the 

 range on the whole is generally within remarkably narrow limits, as appears from the following 

 table: 



Range of specific weight in trees of the same age approximately ; averages for whole trees. 

 [Specific gravity multiplied by 100 to avoid fractions.] 



From this table it would appear that single individuals of one species would approximate 

 single individuals of another species so closely that the weight distinction seems to fail, but in 

 large numbers, for instance carloads of material, the averages above given will prevail. 



INFLUENCE OF LOCALITY. 



In both the Cuban and Longieaf Pine the locality where grown appears to have but little 

 influence on weight or strength, and there is no reason to believe that the Lougleaf Pine from one 

 State is better than that from any other, since such variations as are claimed can be found on any 

 40-acre lot of timber in any State. But with Loblolly, and still more with Shortleaf, this seems not 

 to be the case. Being widely distributed over many localities different in soil and climate, the 

 growth of the Shortleaf Pine seems materially influenced by loc.atiVi. The wood from the Southern 

 Ooast and Gulf region andeveu Arkansas is generally heavier than the wood from localities farther 

 north. Very light and fine-grained wood is seldom met near the southern limit of the range, while 

 it is almost the rule in Missouri, where forms resembling the Norway Pine are by no means rare. 

 The Loblolly, occupying both wet and dry soils, varies accordingly. 



