. Report upon the forestry investigations of the U. S. Department of agriculture. 1877-1898. Forests and forestry. TIMBER PHYSICS SOUTHERN PINE. 353 Influence of moisture on strength. Average of all \ahd tests. Bending strength . Ci ushmg Per cent of moist- Cu- ban. Long- leat. Lob- lolly. b, 430 7,660 7,370 [ 33 J 20 10, 050 8, 900 8, 650 1 15 11,950 10,900 10,100 I 10 15,300 14,000 12,400 [ 33 5,000 4,450 4,170 J 20 6,600 5,450 5,350 \ 15 7,850 6,850 6, 500 1 io 9, 200 9,200 8, 650 Short- leaf. 6, 900 8,170 9, 230 11,000 4,160 5,100 5,900 7,000 Relath e values. Bending streng
. Report upon the forestry investigations of the U. S. Department of agriculture. 1877-1898. Forests and forestry. TIMBER PHYSICS SOUTHERN PINE. 353 Influence of moisture on strength. Average of all \ahd tests. Bending strength . Ci ushmg Per cent of moist- Cu- ban. Long- leat. Lob- lolly. b, 430 7,660 7,370 [ 33 J 20 10, 050 8, 900 8, 650 1 15 11,950 10,900 10,100 I 10 15,300 14,000 12,400 [ 33 5,000 4,450 4,170 J 20 6,600 5,450 5,350 \ 15 7,850 6,850 6, 500 1 io 9, 200 9,200 8, 650 Short- leaf. 6, 900 8,170 9, 230 11,000 4,160 5,100 5,900 7,000 Relath e values. Bending strength. Ciushing endwise .., Mean of both bending and crushing strength Per cent of moist- 33 20 15 10 33 20 15 10 33 20 15 10 Cu- ban. 100 llo 142 181 100 132 157 184 100 125 149 182 Long- leaf. 100 116 142 182 100 122 154 206 100 119 148 194 206 100 122 187 Lob- Short- lolly . leaf. 100 100 117 118 138 134 168 160 100 100 128 122 156 142 168 100 138 164 Aver age. 100 117 139 173 100 126 152 191 100 122 146 182 a 33 per cent green, 20 per cent half dry, 15 per cent yard dry, 10 per cent room S 6 7 8 9 Fig. 93.—Variation of compression strength with moisture. It will be observed that the strength increases by about 50 per cent in ordinary good yard seasoning, and that it can be increased by about 30 per cent more by complete seasoning in kiln or house. Large timbers require several years before even the yard-season condition is attained, but 2-inch and lighter material is generally not used with more than 15 per cent moisture. WEIGHT AND MOISTURE. So far the weight of only the kiln-dry wood has been considered. In fresh as well as all yard and air-dried material there is contained a variable amount of water. The amount of water contained in fresh wood of these pines forms more than half the weight of the fresh sapwood, and about one-fifth to one-fourth of the heartwood; in yard-dry wood it falls to about 12 to 18 per cent, while in wood kept in well-ventilated and esp
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