58 



TKCHNICAL PKUl'EIlTIK^ <)F WOOD. 



[This method was formerly adopted larjj;ely in India foi- splitting 

 .slabs of y:ranite and other stones in quarries. — Th.] 



(d) Warping of Timber. — Owing to the unequal coutractiou or 

 swelling of diti'erent parts of wood duo to changes in the hygro- 

 scopicity of the media to which it is exposed, it is said to warp; 



the extent of warping depends on 

 the amount of shrinkage to which 

 any wood may he suljject. 



As a rule, hard, broad-leaved 

 wood warps more than coniferous 

 wood. Beech is most subject to 

 warping, and walnut and maho- 

 gany warp considerably. Among 

 conifers, larch and Weymouth 

 pine warp least. Heart and 

 semi-heartwood warp less than 

 sapwood. 



"Whenever one side of a beam 

 warps more than the other it 

 becomes curved ; planks are 

 more subject to this the farther 

 they are from the centre of the 

 tree. Scantling lying on damp 

 ground, and exposed above to 

 the air and sun, bends upwards 

 at the ends. Beams let into 

 masonry, and panels of doors, 

 flooring. Sec, will warp during 

 damp weather unless plenty of 

 room is left for their expansion. 

 All planks sawn out of twisted-fibred or wavy-fibred wood 

 are also very subject to warping. [According to Boppe,* 

 owing to the position of the largest annual zones, round logs 

 from young trees warp as shown in fig. 7 (a), and older ones 

 as in fig. 7 (h). — Tr.]. 



The measures taken in industries to prevent the warping of 



(After IJoppe.) 



Tcclmologic Foicstierc, p. 4G. 



