| Douglas fir | 427 | 50.1 | | Cucumber tree | 408 | 47.8 | | Shortleaf pine | 400 | 46.9 | | Red pine | 358 | 42.0 | | Sugar pine | 353 | 41.1 | | White elm | 351 | 41.2 | | Western yellow pine | 348 | 40.8 | | Lodgepole pine | 348 | 40.8 | | Red spruce | 345 | 40.5 | | White pine | 314 | 36.8 | | Engelman spruce | 290 | 34.0 | | Arborvitae | 288 | 33.8 | | Largetooth aspen | 269 | 31.5 | | White spruce | 262 | 30.7 | | Butternut | 258 | 30.3 | | Buckeye (yellow) | 210 | 24.6 | | Basswood | 209 | 24.5 | | Black willow | 193 | 22.6 | |-------------------------------------------------------| re>

The complexity of the computations depends upon the way in which the stress is applied and the manner in which the stick bends.  Ordinarily where the length of the test specimen is not greater than four diameters and the ends are squarely faced (see Fig. 7), the force acts uniformly over each square inch of area and the crushing strength is equal to the maximum load (P) divided
{ P }
by the area of the cross-section (A). { C = —–­ }
{ A }

[Illustration:  FIG. 7.—­Endwise compression of a short column.]

It has been demonstrated[4] that the ultimate strength in compression parallel to the grain is very nearly the same as the extreme fibre stress at the elastic limit in bending. (See Table V.) In other words, the transverse strength of beams at elastic limit is practically equal to the compressive strength of the same material in short columns.  It is accordingly possible to calculate the approximate breaking strength of beams from the compressive strength of short columns except when the wood is brittle.  Since tests on endwise compression are simpler, easier to make, and less expensive than transverse bending tests, the importance of this relation is obvious, though it does not do away with the necessity of making beam tests.

[Footnote 4:  See Circular No. 18, U.S.  Division of Forestry:  Progress in timber physics, pp. 13-18; also Bulletin 70, U.S.  Forest Service:  Effect of moisture on the strength and stiffness of wood, pp. 42, 89-90.]

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