_Photo by U.S, Forest Service._] Table XI gives an analysis of the causes of first failure in 840 large timber beams of nine different species of conifers.

Of the total number tested 165 were air-seasoned, the remainder green.
The failure occurring first signifies the point of greatest weakness in the specimen under the particular conditions of loading employed (in this case, third-point static loading).
|-----------------------------------------------------------| | TABLE XI | |-----------------------------------------------------------| | MANNER OF FIRST FAILURE OF LARGE BEAMS | | (Forest Service Bul.

108, p.

56) | |-----------------------------------------------------------| | | Total | Per cent of total failing by | | COMMON NAME | number |---------+-------------+-------| | OF SPECIES | of | Tension | Compression | Shear | | | tests | | | | |------------------+--------+---------+-------------+-------| | Longleaf pine: | | | | | | green | 17 | 18 | 24 | 58 | | dry | 9 | 22 | 22 | 56 | | Douglas fir: | | | | | | green | 191 | 27 | 72 | 1 | | dry | 91 | 19 | 76 | 5 | | Shortleaf pine: | | | | | | green | 48 | 27 | 56 | 17 | | dry | 13 | 54 | | 46 | | Western larch: | | | | | | green | 62 | 23 | 71 | 6 | | dry | 52 | 54 | 19 | 27 | | Loblolly pine: | | | | | | green | 111 | 40 | 53 | 7 | | dry | 25 | 60 | 12 | 28 | | Tamarack: | | | | | | green | 30 | 37 | 53 | 10 | | dry | 9 | 45 | 22 | 33 | | Western hemlock: | | | | | | green | 39 | 21 | 74 | 5 | | dry | 44 | 11 | 66 | 23 | | Redwood: | | | | | | green | 28 | 43 | 50 | 7 | | dry | 12 | 83 | 17 | | | Norway pine: | | | | | | green | 49 | 18 | 76 | 6 | | dry | 10 | 30 | 60 | 10 | |-----------------------------------------------------------| | NOTE .-- These tests were made on timbers ranging in cross | | section from 4" x 10" to 8" x 16", and with a span of 15 | | feet.

| |-----------------------------------------------------------| TOUGHNESS: TORSION Toughness is a term applied to more than one property of wood.
Thus wood that is difficult to split is said to be tough.