DEFECTS AND UXSOUNDXESS. 



(19 



knots are frequently as hard as bone, and altogether resist the 

 action of planes and saws. Silver-fir knots are usually very 

 dark-coloured, and thus reduce the value of this timber. The 

 transverse strength of Jbeams is evidently reduced by the presence 

 in them of large knots. In order to avoid knottiness in timber 

 trees must be grown in dense woods, especially when young. 



Scandinavian timber containing many knots is often falsified 

 by boring away the surface of the knots on both sides, and filling 

 the place with a mixture of wood-chips and glue. 



(e) Damage by Game and other Injuries. — Damage done to 



Fig. 14. 



Fig. 15. 



RiNIiGALL. 



(After Fernandez. ) 



timber, especially in parks by deer, which peel the bark of trees, 

 or rub their antlers against poles, may frequently be detected 

 deep-down in spruce and other timber, although it has been 

 completely occluded and enclosed within the wood of the stem . 

 In fig. 14, a, a is the exposed wound, h, h the occluding wood 

 which eventually produces regularly formed annual zones at 7». 

 The surface of the wound is always dark brown, and the woody 

 rings above and below the wound are also usually dark coloured. 

 Such stems cannot generally be used, either in the round or as 

 scantling. 



[Similar damage is done to trees by the abrasion of their bark by 

 cattle, cartwheels or during fellings, when one tree falls against 



