FOREST UTILIZATION 57 



Quarter sawing increases the gloss. 



IV. Odor. Odor is important for the use of wood in the package 

 industry. The strong odor of wood is usually lost in the 

 course of seasoning. The following species retain, however, 

 a characteristic odor : Cherry, birch, sassafras, red cedar. 

 D. Inner qualities, or qualities discernible by mechanical tests. 

 I. Specific gravity. 



(a) Pure wood fibre forms in fresh wood, with broad 



leafed species of temperate climates, about 35 % 

 of the entire weight, while conifers show an aver- 

 age of about 25 %. 



(b) Air dried wood still retains from 10 % to 15 % of 



water. If the dry kiln reduces the percentage of 

 water below that figure, the hygroscopicity of the 

 wood will speedily cause it to return. 



(c) Factors influencing specific gravity of air-dried wood 



within the same species are : 



1. The width of the rings, in ring porous 



hardwoods and in conifers forming 

 heartwood. 



2. The incrustations of rosin, tannin and 



pigments in the heart. 



3. The age of the tree. 



4. The decay of the fibre. 



5. The section of the tree, since roots are 



very light, butt logs heavy, bole fairly 

 light and branches fairly heavy. 

 In the case of the diffuse porous hard- 

 woods and of conifers destitute of heart, 

 no rule can be given relative to specific 

 gravity 'of inner and outer layers, of 

 wide and narrow rings. 



(d) Air dried lumber has, on an average, the following 



weights : 



Weight of 



Species Specific gravity. 1,000 ft. b.m. 



Turkey oak, hickory, service-bush, over 0.75 over 4,000 Ibs. 

 Ash, white and red oak. locust, 



beech, hornbeam, hard maple, 



pear tree , 0.70-0.75 about 3,750 Ibs. 



Elm, soft maple, apple tree, syca- 



more, birch 0.60-0.70 about 3,400 Ibs. 



Horse chestnut, chestnut, tulip 



tree, alder, larch, longleaf pine 0.55-0.60 about 3,000 Ibs. 

 Yellow pine, douglas fir, spruce, 



fir, willow, cottonwood 0.45-0.55 about 2.600 Ibs. 



White and sugar pine under 0.45 about 2,200 Ibs. 



(e) Rules. 



i. Specific gravity times 5,200 equals the 

 weight of 1,000 feet b. m. of sawn lum- 

 ber. Reason 1,000 superficial feet of 

 water one inch deep weigh 5,200 Ibs. 



