Variable, usually hard, strong, difficult to work, durable. Representative Uses of Wood. Heavy construction, dimension timbers, railway ties, piles, fuel. Weight of Seasoned Wood in Pounds per Cubic Foot. 32 (U. S. Forestry Div.).[86] 36 (average of 20 specimens by Soulé).[87] 32. Modulus of Elasticity. 1,680,000 (average of 41 tests by U. S. Forestry Div.).[86] 1,862,000 (average of 21 specimens by Soulé).[87] 1,824,000. Modulus of Rupture. 7,900 (average of 41 tests by U. S. Forestry Div.).[86] 9,334 (average of 21 specimens by Soulé).[87] 12,500. Remarks. Used similarly to hard pine. Lumbermen divide into red and yellow woods, the former dark and coarse, the latter fine, lighter, and more desirable. These distinctions probably due to age. One of the world's greatest trees. [p156] FOOTNOTE [Footnote 86: See page 6.] [Footnote 87: Professor Frank Soulé, University of California. Trans. Am. Inst. M. E., p. 552, Vol. XXIX.] FIR. (_Abies_.) Several of the fir-trees of the western United States attain to very great size. The silver fir (_Abies grandis_) and the white fir (_Abies concolor_) supply much wood in the section in which they grow. The balsam fir (_Abies balsamea_) of the Eastern States is of some commercial importance. Fir wood resembles spruce in appearance and in structural qualities. It may be told from spruce as well as from pine and larch by the fact that fir has no resin-ducts. The balsam fir is distinguishable by clear liquid resin which appears in blisters in the bark. The coarse, weak wood is cleaner than the bark would indicate. Spruce and fir woods are often confused in the United States, while pine, spruce, and fir are similarly confounded in Europe. [Illustration: BALSAM FIR (_Abies balsamea_).] Fir trees have flat, scattered, evergreen leaves, and cones that stand erect (see footnote under spruce). [p157] BALSAM FIR, COMMON BALSAM FIR. _Abies balsamea Mill._ Nomenclature. (Sudworth.) Balsam (Vt., N. H., N. Y.). Fir Tree (Vt.). Balm of Gilead (Del.). Canada Balsam (N. C.). Balm of Gilead Fir (N. Y., Pa.). Blister Pine, Fir Pine (W. Va.). Single Spruce, Silver Pine (Hudson Bay). Locality. Minnesota to Virginia, northward intermittently into Canada. Features of Tree. Fifty to seventy feet in height, one to two feet in diameter. Sometimes low shrub. Blisters in smooth bark contain thick balsam. Erect cones. Color, Appearance, or Grain of Wood. Heartwood white to brownish, sapwood lighter. Coarse-grained, compact structure, satiny. Structural Qualities of Wood. Soft, light, not durable or strong, resinous, easily split. Representative Uses of Wood. Occasionally used as inferior lumber. Weight of Seasoned Wood in Pounds per Cubic Foot. 23. Modulus of Elasticity. 1,160,000. Modulus of Rupture. 7300. Remarks.