66 TECHNICAL riloPEHTIKS OF WOOD. 



ash, alder, oaks and spruce, especially near the roots of the trees, 

 the texture becoming normal higher up the stem. Curls arc 

 common in beeehwood above the insertion of the brunches. 

 Curls arc valued bv the cabinet-muker, but useless for carpentry. 



V. Ticistcd J-'ihrc. 



Twisted fibre occurs when the grain of the tree winds spirally 

 round its axis. This may be either from the left to the right 

 hand of an observer stationed in front of the tree, or the 

 reverse. The former direction is opposed to the apparent 

 diurnal motion of the sun, and the latter is with it. As a rule 

 the direction of the twist is constant throughout the tree, but in 

 some trees alternate zones of wood twist in opposite directions. 



In the case of the pyramidal or Lombardy poplar, the torsion is 

 always from right to left, and the reverse in the horse-chestnut. 



In most European forest trees, the torsion is from right to left, 

 especially in the case of the spruce. Torsion is common in the 

 following species: — Scotch pine, horse-chestnut, oak, sweet 

 chestnut, spruce, elm, beech, white poplar; it is rarer with 

 birch, alder, silver-fir, ash and sycamore. Although torsion is 

 commonest in trees grown in the open, it is nevertheless not 

 infrequent in dense woods, especially with oaks. In the case 

 of Scotch pine the degree of torsion may be so excessive that 

 the direction of the fibres twists completely round the stem 

 within a length of 5 to 7 feet. Fossil conifers have been found 

 with twisted fibre. Torsion of fibres is sometimes so frequent 

 that the trees in whole woods may be so afiected. There is a 

 Scotch pine forest near Trier where 8-4 per cent, of the trees 

 have twisted fibre, and other similar cases occur in the Bavarian 

 Alps, and in Switzerland. 



Torsion, according to Alexander ]3raun, is partly caused by a 

 sloping direction of the cambium-cells and partly by their great 

 length, so that there is no room for them in a vertical direction. 

 In fact it is only a question of degree, for in most trees the fibres 

 will be found to wind spirally round the stem, if their direction 

 is followed far enough. 



Wood with twisted fibre is not suitiil)lr for jilanks, wliicli 

 usually warp when sawn from such trees, and does not make 

 good scantling or beams, as their strength is greatly reduced by 



