FOREST UTILIZATION 



59 



ton woods), however, moist wood is tougher and 

 therefore harder as well, 

 (d) Frost increases the hardness. 



SCHEDULE OF HARDNESS. 



III. Cleavability or fissibility. 



Cleavability is the resistance of fibre to axe, saw and wedge, 

 worked lengthwise in the direction of the fibre. Radial 

 cleavage is usually by 5° % to lOO % easier than tangential 

 cleavage (except in black gum). 

 Factors of cleavability are : 



(a) A straight, long, elastic fibre. 



(b) Heavy and high medullary rays. 



(c) Straightness of growth. 



(d) Branchiness. 



(e) Moisture (very green and very dry wood splits 



best). 



(f) Frost (reduces the cleavability). 



(g) Hardness and softness (extremely hard and ex- 



tremely soft wood splits badly. This rule holds 

 good only in hardwoods). 



SCH-EDDLE OF CLEAVABILITT. 



IV. Pliability. 



Under pliability we combine flexibility and elasticity. 



(a) Flexibility ; wood which is easily bent without 

 breaking is flexile (flexible). Softwoods are nat- 

 urally less flexile than hardwoods. 

 Flexibility depends on : 



1. Toughness and cohesive force of fibre. 



2. Moisture, which increases it very much. 



3. Heat, which ■ increases it. 



4. Age of tree, inasmuch as young shoots 



are tougher than old wood. 



5. Impregnation, natural as well as artificial, 



