. Bulletin. Forests and forestry -- United States. Tested in compression endwise (fig. 29), the fibers act as so many hollow columns firmly grown together, and when the load becomes too great the piece fails in the manner illustrated in fig. 31. This failure is a very complex phenomenon; in wood like pine the fibers of the plain in which failure occurs become separated into small bodies; they tear apart aud cease to behave as one solid body but act as a large number of very small independent pieces. Like the strands of a rope these small bodies offer but little resistance to compression; they
. Bulletin. Forests and forestry -- United States. Tested in compression endwise (fig. 29), the fibers act as so many hollow columns firmly grown together, and when the load becomes too great the piece fails in the manner illustrated in fig. 31. This failure is a very complex phenomenon; in wood like pine the fibers of the plain in which failure occurs become separated into small bodies; they tear apart aud cease to behave as one solid body but act as a large number of very small independent pieces. Like the strands of a rope these small bodies offer but little resistance to compression; they bend over, and the piece "; It is evident that a vertical position and a regular arrangement of the fibers increase the resistance and that therefore the medullary rays and oblique position of fibers in crossgrained and knotty timber tend to reduce the strength in com- pression. From the following table of strength in tension and compression it will be seen that these two are not always proportional, the stiffer conifers excelling in the latter, the tougher hard woods in the former: Fig. 29.—Compression Fig. 30.—Longitudinal shearing. Ratio of strength in tension and compression, showing the difference between rigid conifers and lough hard woods. Hickory Elm Larch Lougleaf pine i: Ratio: Tensile strength. compressive strength. A stick 1 square inch in cross section. Weight required to— Pull apart. Pounds. 32, 000 29, 000 19,400 17,300 Crush endwise. Pounds. 8,500 7,500 8,600 7,400 Strength in compression of common American tvoods in well-seasoned select pieces. [Approximate weight per square inch of cross section requisite to crush a piece of wood endwise.] Pounds. (1) Black locust, yellow and cherry birch, hard maple, best hickory, longleaf and Cuban pines, and tamarack 9, 000+ (2) Common hickory, oak, birch, soft maple, walnut, good elm, best ash, shortleaf and loblolly pines, western hemlock, and Douglas fir 7, 000+ (3) Ash,
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