TIMBER. 



CHARACTERISTICS AND PROPERTIES OF WOOD. 



I— STRUCTURE AND APPEARANCE. 



The structure of wood affords the ouly reliable means of distinguish 

 ing the different kinds. Color, weight, smell, and other appearances, 

 which are often direct or indirect results of structure, may be helpful in 

 this distinction but can not be relied upon entirely. In addition, struc- 

 ture underlies nearly all the technical properties of this important 

 product and furnishes an explanation why one piece differs as to these 

 properties from another. 



Structure explains why oak is heavier, stronger, and tougher than 

 pine; why it is harder to saw and plane, and why it is so much more 

 difficult to season without injury. From its less porous structure alone, 

 it is evident that a piece of a young and thrifty oak is stronger than the 

 porous wood of an old or stuuted tree; or that Georgia or longleaf pine 

 excels white pine in weight and strength. Keeping especially in mind 

 the arrangement and direction of the fibers of wood, it is clear at once 

 why knots and "crossgrains" interfere with the strength of timber. 



It is due to structural peculiarities that "honeycombing" occurs in 

 rapid seasoning, that "checks" or cracks extend radially and follow 

 pith rays, that tangent or " bastard " boards shrink and warp more than 

 quartered lumber. These same peculiarities enable cherry and oak to 

 take a better finish than basswood or coarse grained pine. 



Moreover, structure, aided by color, determines the beauty of wood. 

 All the pleasing figures, whether in a hard-pine ceiling, a desk of quar- 

 tered oak, or in the beautiful panels of "curly" or "bird's-eye" maple 

 decorating the saloon of a ship or a palace car, are due to differences 

 in the structure of the wood. Knowing this, the appearance of any 

 particular section can be foretold, and almost unlimited choice and 

 combination are thereby suggested. 



Thus a knowledge of structure not only enables us to distinguish the 

 different woods, judge as to their qualities, and explain the causes of 

 their beauty, but it also becomes an invaluable aid to the thoughtful 

 worker, guiding him to a more careful selection and a more perfect use 

 of his material. 



CLASSES OF TREES. 



The timber of the United States is furnished by three well-defined 

 classes of trees: the needle-leaved, naked-seeded conifers (pine, cedar, 

 etc.), the dicotyledonous (with two seed leaves), broad-leaved trees (oak, 



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