278 TIMBER BRIDGES AND TRESTLES. CHAP. VII. 



Axis. The line connecting the centers of successive cross-sections of a stick. 



Straight. Having a straight line for an axis. 



Out of Wind. Having the longitudinal surfaces plane. 



Full Length. Long enough to "square" up to the length specified in the order. 



Corner. The line of intersection of the planes of two adjacent longitudinal surfaces. 



Girth. The perimeter of a cross-section. 



Side. Either of the two wider longitudinal surfaces of a stick. 



Edge. Either of the two narrower longitudinal surfaces of a stick. 



Face. The surface of a stick which is exposed to view in the finished structure. 



Sapwood. A cylinder of wood next to the bark and of lighter color than the wood within. 

 It may be of uneven thickness. 



Heartwood. The older and central part of a log, usually darker in color than sapwood. 

 It appears in strong contrast to the sapwood in some species, while in others it is but slightly 

 different in color. 



Springwood. The inner part of the annual ring formed in the earlier part of the season, 

 not necessarily in the spring, and often containing vessels or pores. 



Summerwood. The outer part of the annual ring formed later in the season, not necessarily 

 in the summer, being usually dense in structure and without conspicuous pores. 



Decay. Complete or partial disintegration of the cell walls, due to the growth of fungi. 



Sound. Free from decay. 



Solid. Without cavities; free from loose heart, wind shakes, bad checks, splits or breaks, 

 loose slivers, and worm or insect holes. 



Wane. A deficient corner due to curvature or to taper of the log. 



Square Cornered. Free from wane. 



Knot. The hard mass of wood formed in a trunk at a branch, with the grain distinct and 

 separate from the grain of the trunk. 



Cross-Grain. The gnarly mass of wood surrounding a knot, or grain injuriously out of 

 parallel with the axis. 



Wind Shake. A crack or fissure, or a series of them, caused during growth. 



STANDARD DEFECTS OF STRUCTURAL TIMBER.* 



The standard defects included in the following list are mostly such as may be termed natural 

 defects, as distinguished from defects of manufacture. The latter have usually been omitted, 

 because the defects of manufacture are of minor significance in the grading of structural timber: 



Sound Knot. A sound knot is one which is solid across its face and is as hard as the wood 

 surrounding it. It may be either red or black, and is so fixed by growth or position that it will 

 retain its place in the piece. 



Loose Knot. A loose knot is one not firmly held in place by growth or position. 



Pith Knot. A pith knot is a sound knot with a pith hole not more than f in. in diameter f 

 in the center. 



Encased Knot. An encased knot is one which is surrounded wholly or in part by bark or 

 pitch. Where the encasement is less than | in. in width on each side, nor exceeding one-half the 

 circumference of the knot, it shall be considered a sound knot. 



Rotten Knot. A rotten knot is one not as hard as the wood surrounding it. 



Pin Knot. A pin knot is a sound knot not over \ in. in diameter. 



Standard Knot. A standard knot is a sound knot not over \\ in. in diameter. 



Large Knot. A large knot is a sound knot, more than I } in. in diameter. 



Round Knot. A round knot is one which is oval or circular in form. 



Spike Knot. A spike knot is one sawn in a lengthwise direction. The mean or average 

 diameter shall be taken as the size of these knots. 



Pitch Pockets. Pitch pockets are openings between the grain of the wood, containing more 

 or less pitch or bark. These shall be classified as small, standard and large pitch pockets. 



Small Pitch Pocket. (a). A small pitch pocket is one not over | in. wide. 



Standard Pitch Pocket. (b). A standard pitch pocket is one not over f in. wide nor over 

 3 in. in length. 



Large Pitch Pocket. (c).^A large pitch pocket is one over f in. wide, or over 3 in. in length. 



Pitch Streak. A pitch streak is a well-defined accumulation of pitch at one point in the 

 piece. When not sufficient to develop a well-defined streak, or where the fiber between grains, 

 that is, the coarse grained fiber, usually termed "spring wood," is not saturated with pitch, it 

 shall not be considered a defect. 



* Adopted by Am. Ry. Eng. Assoc., Vol. 8, 1907. 



t Measurements which refer to the diameter of knots or holes shall be considered as the mean 

 or average diameter in all cases. 



