AMERICAN FOREST TREES 9 



That explains in part why some species are adapted to quarter- 

 sawing and others are not. If no broad rays exist in the wood, as with 

 white pine, red cedar, and cottonwood, quarter-sawing cannot add much 

 to the wood's appearance. 



Grain The grain of wood is not a definite quality. The word 

 does not mean the same thing to all who use it. It sometimes refers 

 to rings of yearly growth, and in that sense a narrow-ringed wood is fine 

 grained, and one with wide rings is coarse grained. A curly, wavy, 

 smoky, or birdseye wood does not owe its quality to annual rings, yet 

 with some persons, all of these figures are called grain. The term some- 

 times refers to medullary rays, again to hardness, or to roughness. 

 Some mahogany is called "woolly grained" because the surface polishes 

 with difficulty. The pattern maker designates white pine as "even 

 grained", because it cuts easily in all directions. The handle maker 

 classes hickory as "smooth grained", because it polishes well and the sole 

 idea of the maker is smoothness to the touch. There are other grains 

 almost as numerous as the trades which use wood. In numerous 

 instances "figure" is a better term than "grain." Feather mahogany, 

 birdseye birch, burl ash, are figures rather than grains. There is no 

 authority to settle and decide what the real meaning of grain is in wood 

 technology. It has a number of meanings, and one man has as much 

 authority as another to interpret it in accordance with his own ideas, 

 and the usage in his trade. It is a loose term which covers several 

 things in general and nothing in particular. 



Weight The weight of wood is calculated from different stand- 

 points. It has a green weight, an air-dry weight, a kiln-dry weight, and 

 an oven-dry weight. All are different, but the differences are due to the 

 relative amounts of water weighed. Sawlogs generally go by green 

 weight; yard lumber by air-dry or partly air-dry weight; while the 

 wood used in ultimate manufacture, such as furniture, is supposed to 

 be kiln-dry. 



The absolute weight of wood, with all air spaces, moisture, and 

 other foreign material removed, is about 100 pounds per cubic foot, 

 which is 1.6 times heavier than water; but that is not a natural form 

 of wood. It is known only in the laboratory. 



The actual wood substance of one species weighs about the same 

 as another. Dispense with all air spaces, all water, and all other foreign 

 substance, and pine and ebony weigh alike. It is apparent that the 

 different weights of woods, as between cedar and oak for example, are 

 due chiefly to porosity. The smaller the aggregate space occupied by 

 pores and other cavities, the heavier the wood. That accounts for the 

 differences in weights of absolutely dry woods of different kinds, except 



