DEFECTS AND UNSOUNDNESS. 



67 



the saw having cut through the fibres. All sawn wood with 

 twisted fibre must be planed in opposite directions along its 

 opposite faces. Coopers reject such wood for their staves, and 

 probe standing trees to test the straightness of the fibres. It 

 may be used for short split pieces, and also in the round, or as 

 wany-beams.* 



The custom followed in many districts in Germany of prefer- 

 ring wood twisted from right to left to that twisted in the opposite 

 direction appears to be due to prejudice, for in other districts 

 no difference is made in this respect. 



[Many woods of hot countries naturally have bent fibres, and that 

 of Guaiacum wood (^Lignum vitce), from the West Indies, may be 

 quoted ; in this, the grain bends from right to left and back 

 again, and frequently cuts the vertical at an angle of 45°, assuming 

 different directions in successive narrow layers. Such wood cannot 

 be split radially and only with great difficulty tangentially, and is 

 therefore very useful for pulleys, bowls and other purposes where 

 toughness is required and weight is no objection. — Tr.] 



vi. Knottiness. 

 All branches which have become enclosed in the wood give rise 

 to knots (fig. 11). Whenever trees, and especially light-demanders, 

 have been grown in dense 

 woods, they free them- 

 selves early from their 

 lower branches, and large 

 knots do not occur in 

 their wood. Trees grown 

 in the open, and many 

 shade-bearers, even when 

 grown in dense woods, 

 are not free from knots ; 

 though their lower 

 branches may eventually 

 die, and become enclosed 

 in the wood, such knots 

 are always liable to be- 

 come loose after the stem has been sawn-up, and thus leave holes 

 in the planks, which considerably reduce their value. 

 * Wane is the natural roiiudcd edge of a log. 



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