DEFECTS AND UNSOUNDNESS. 65 



cup-shake does not proceed far up the stem and is most frequent 

 in old trees ; it frequently extends only for a few feet in height, 

 hut may proceed to the top of the stem. The defect is com- 

 monest in the case of old silver-fir, larch, oaks, heech and many 

 softwoods, but scarcely any species is exempt from it. 



Cup-shaken wood cannot usually be sawn, but may be split 

 into staves. The use that can be made of such wood evidently 

 varies with the extent of the defect in question. 



(d) Abnormal Direction of Fibres. 



i. General Account. 



An abnormal direction of the fibres in a stem renders wood 

 unfit for use in construction of buildings, &c., but may give it a 

 certain value for cabinet-making. Under this heading are in- 

 cluded, occlusion of wounds, burrs, wavy wood (curls), twisted 

 fibres and knottiness. 



ii. Occlusion of fVoiiJids. 

 The wood covering old wounds caused by loss of bark, or the 

 pruning of large branches, readily detaches itself from the 

 subjacent wood, and is formed of fibres irregular in direction. 

 It cannot therefore generally be utilized except for fuel. 



iii. Burrs. 

 Burrs are due to the extensive production of dormant buds, 

 round which the fibres wind abnormally ; they are also due to 

 injuries and pruning. Burrs are commonest in poplars, elms, 

 walnut, ash (the finest ash-burrs come from Hungary), alders, 

 birch (birch-burrs are termed Swedish lily-wood in the timber- 

 market), maple (silver-maple or birdseye-maple, fine specimens 

 of which come from America), also in oaks and limes. Burrs 

 are usually found low down on a stem, and are commonest with 

 trees grown in the open, not in closed woods. They are usually 

 sawn into thin veneers and used for the fronts of piano-fortes 

 and other ornamental cabinet-making work. They are produced 

 artificially by lopping ash-trees. 



iv. Curls or Wavy Wood. 

 Curls (or wavy wood) are formed when the fibres bend from 

 side to side, but do not cross one another ; they occur in beech, 



VOL. V. F 



