36G 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



liesnlts of tests m bending, at rupture. 

 [Pounds per square inch.] 



No. 



o 

 6 



7 



8 



9 



10 



13 

 14 

 15 

 16 

 17 

 18 

 19 

 20 

 21 

 22 

 23 

 24 

 25 



27 

 28 

 29 

 30 

 31 

 32 



Spt ( its. 



deduced to 15 per cent moisture. 



Longleaf pine. 

 Cuban pino . .. 

 Shortleaf pino. 

 Loblolly pine.. 



Reduced to 12 per cent moisture. 



"White pine • 



Kedpine 



Spruce pine 



Bald cypress 



White cedar 



Douglas spruce a ... 



White oak 



Overeup oak 



Post oak 



Cow oak 



Podoak 



Texan oak 



Yellow oak 



Water oak 



Willow oak 



Spanish oak 



Sba^bark hickory. - 

 Mockernut hickory 



Water hickory 



Bitternut hickory.. 

 Nutmeg hickory - . - 



Pecan hickory 



Pignut hickory... - 



White elm 



Cedar elm 



White ash 



Green ash 



Sweet gum 



Number 



ot tests. 



1,160 

 390 

 330 

 650 



120 



95 



170 



C55 



87 



■ftlo 



216 



49 



256 



57 



117 



40 



31 



153 



257 



187 



75 



14 



25 



72 



37 



30 



18 



44 



87 



10 



118 



Highest 

 single test. 



17, 800 



17, 000 

 15, 300 

 14, 800 



11, too 



12, 900 



16, 300 



14, 800 



9,100 



13, 000 

 20, 300 

 19, 600 

 16, 400 

 23, 000 

 16, 500 

 19, 500 



15, 000 



16, 000 

 16, 000 

 17, 300 

 23, 300 

 20, 700 

 18, 000 

 19, 500 

 16, 600 

 18, 300 

 25, 000 



14, 000 

 19,200 



15, 000 



16, 000 

 14, 400 



Lowest 

 sniffle test. 



3, 300 

 2,900 

 5,000 

 3,900 



4,600 

 3, 100 

 3, 100 

 2,300 

 3,500 

 3,800 

 5,700 

 4,900 

 5,100 

 3,300 

 5,700 

 8,200 

 5,100 

 5,800 

 3, 200 

 5, 000 

 5,700 

 5, 300 

 5,300 

 7,000 

 6,700 

 5,600 

 11,100 

 7,300 

 6,600 

 5,000 

 5,100 

 5,100 



Average 

 highest 10 

 per cent of 



tests. 



14, 200 

 14, 600 

 12, 400 

 13, 100 



10, 100 

 12, 300 



13, 600 

 11, 700 



8,400 



12, 000 

 18, 500 

 14, 900 

 15, 300 

 12, 500 



15, 400 



16, 900 



14, 600 

 15, 700 

 13, 800 

 15, 600 

 20, 300 

 19, 700 

 17, 300 

 19, 300 



15, 600 

 18, 100 

 24, 300 



13, 600 

 17, 300 

 14, 200 



16, 000 

 12, 700 



Average 

 lowest 10 

 per cent of 



tests. 



8,800 

 8,800 

 7,000 

 8,100 



5,000 

 4,900 

 5,800 

 5,000 

 4,000 

 4,100 

 7,600 

 6,300 

 7,400 

 6,500 

 9,100 

 10, 000 

 5,700 

 7,200 

 5,400 

 6,900 

 9,400 

 7,900 

 5,400 

 8,700 

 8,100 

 10,300 

 11, 500 

 7,300 

 8,500 

 6, 300 

 5,100 

 0,000 



Average of 

 all tests. 



30, 900 



11, 900 



9, 200 



10, 100 



7,900 

 9, 100 



10, 000 

 7,900 

 6,300 

 7,900 



13, 100 



11, 300 



12, 300 

 11, 500 

 11, 400 

 13, 100 

 10, 800 

 12, 400 

 10, 400 

 12, 000 

 36,000 

 15, 200 

 12, 500 

 35, 000 

 12, 500 

 15, 300 

 18, 700 

 10, 300 

 13, 500 



10, 800 



11, 600 

 9,500 



Proportion 



of tests 



within 10 



per cent of 



average. 



Per cent. 

 41 

 46 



40 

 44 



43 

 28 

 43 

 25 

 32 

 22 

 39 

 47 

 47 

 32 

 46 

 64 

 28 

 40 

 33 

 40 

 40 

 45 

 21 

 28 

 40 

 38 

 43 

 44 

 50 

 37 

 20 

 39 



Pioportion 



of tests 



within 25 



per cent of 



average. 



l J er cent. 



84 

 83 

 79 

 84 



81 

 60 

 81 

 69 

 78 

 58 

 75 

 81 

 92 

 68 

 84 

 86 

 65 

 76 

 70 

 72 

 84 

 78 

 64 

 60 

 88 

 95 

 77 

 72 

 86 



t*rf 



60 

 79 



a Actual tests on "dry" material not reduced for moistuie. 



RELATIONE OF HEIGHT AND STRENGTH. 



That within the same species the strength of -wood varied with the dry weight (specific gravity), i. e., that 

 the heavier stick is the stronger, has been known for some time. That this law of variation held good not only for 

 a given species, but irrespective of species for the four principal pines of our Southern States was indicated in 

 Circular 12 of this Division. This fact becomes the more important in practical application, as the wood of these 

 species of pines so far can not be distinguished at all by its anatomical structure and only with difficulty and 

 uncertainty by other appearances, while in the lumber market substitution is not infrequent. It will therefore be 

 best with these pines, where strength alone is desired, to inspect the material by weight (specific), other things 

 being equal, disregarding species determination. 



While this result of the exhaustive series of tests reasonably well demonstrated for these pines may be 

 considered of great practical value, we can now extend the application of the law of relation between weight and 

 strength a step farther, and state as an indication of our tests that probably in woods of uniform structure strength 

 increases with specific weight, independently of species and genus distinction, i. e., other things being equal, the 

 heavier wood is the stronger. We are at present inclined to state this important result with caution, only as a 

 probability or indication, until either the test material and tests can be more closely scanned, or more carefully 

 planned and minutely executed series of detail tests can be carried on to confirm the truth of what the wholesale 



tests seem to have developed. 



In the following two diagrams the average strength of the different species in compression endwise and 

 bending, as found in the preceding tables, has been plotted with reference to the dry weight as given in preceding 



table. 



Considering that these tests and weight determinations (especially the latter) were not carried on with that 

 finesse which would be required for a scientific demonstration of a natural law, that other influences, as crossgram, 

 unknown defects, and moisture conditions may cloud the results, and that in the averaging of results undue consid- 

 eration may have been given to weaker or stronger, heavier or lighter, material, the relaxation is exhibited even by 

 this wholesale method with a lemarkable degree of uniformity bordering on demonstration. 



An exception is apparent in the oaks in that they do not exhibit this relation of weight and strength with 

 reference to other species, and also with less definitoness among the various species of oak in themselves. The 

 structure of oak wood being exceedingly complicated and essentially different from that of the wood of all other 

 species under consideration, it may reasonably be expected that it will not range itself with these. 



