370 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



From these tests the following table of averages is derived, together with fig. 97: 



At^erage of tests for maximum uniformity. 



Name. 



White pine (Pinus strobus) 



Longleaf pine < Pinus palustm) 



Tnhptree (poplar) (Linodendron tulipifera) 



White oak (Quercns alba) 



Loblolly pine (Pmus tseda) 



Cypress (Taxodium distichum) 



Per cent. 

 8 



7.8 



8 



Yard dry. 



125 -f- (green). 



125 4- (green). 



Average 

 strength of 

 all pieces. 



Lbs. per t>q.in. 

 4,900 

 10, 800 

 6,010 

 8,300 

 2,670 

 4,090 



Greatest difference in 

 strength between adjoin 

 ing pieces 



Lbs. per &q, in. 

 190 

 380 

 480 

 1,110 

 130 

 70 



Greatest dif 



ference m en 



tire scantling, 



l. e., 6-10 loot 



piece. 



Per cent. 



18 

 10 

 20 

 87 

 20 

 15 



It will be observed that green cypress excelled in its uniformity; that green loblolly proves not more uniform 

 than dry white and longleaf pine; that wood of the conifers far excel even the tuliptree (poplar) with its uniform 

 grain and texture; and that oak, as might be expected, is the least uniform. It will 'also bo noticed that even in 

 one and the same short scantling (6 to 10 feet) of select quarter-sawed longleaf pine differences of 10 per cent may 

 occur, and that in all others these differences were even greater. 



Incidentally in this and the following experiment a small number of the blocks were thoroughly oven-dried 

 (to about 2 per cent moisture), and it was found that the strength of both cypress and loblolly was increased by 

 about 150 per cent during drying, so that wood ab 2 per cent is about two and one-half times as strong as perfectly 

 green or soaked material; and also that drying from 8 to 10 per cent to the lowest attainable moisture condition 

 d to 2 per cent) still adds about 25 per cent to the strength of the wood. 



In the following diagram and table a part of the results are presented in detail : 



// t OOO { 

 /QOO& 

 9.00O 



6,000 

 7000 

 6,000 

 5,000 

 4,000 

 3O00 



B.OOO 

 BlOC/f#M£ffc/ 





« O © i> 



^ZZZmZZTp.'NZ 



<>— g-0.. ^ 



CYPP& 



■ o - & 



frrrk — e 



IOBLOUY Pim 



3 S 7 9 // /3 /S /7 /9 2/ 23 25 



Fig. 97. — Strength of contiguous blocks, showing maximum uniformity of select <piarter-sawed material in compression endwise. 



