HARDNESS. 37 



heavy short-fibred wood. For in order to get the better of the 

 bending and yielding of the fibres in the former case, the axe 

 must act with a greater weight, as its action in this case is not 

 only cutting, but also rending. 



In the case of heavy compact wood the fibres do not bend, 

 and the axe cuts more freely and may be therefore lighter than 

 in the former case, but must have a thinner, finer and harder 

 steel edge. 



In order to reduce the resistance offered by wood-fibres to the 

 axe at right angles to the blade, it is usual to cut obliquely ; 

 the more obliquely the cut is delivered the greater is the 

 api^roach to a splitting action, when resistance is least and the 

 work to be done is consequently reduced. 



Experience shows that to fell frozen wood comparatively 

 heavy axes are required, but the reason for this is not clear. 



(b) The resistance wood offers to the saw is very different from 

 that it ofi"ers to the axe. The direction in which the saw acts is 

 not nearly so important as in the case of the axe : it appears on 

 the contrary in the case of most woods, and especially that of 

 light softwoods, that the resistance to the saw is greater parallel 

 to the direction of the axis of the tree, than across the fibres ; 

 the saw never splits, but tears and cuts the fibres asunder, and 

 sometimes separates them from one another with a plane-like 

 action. 



In the case of broad-leaved trees the softer and longer the 

 fibres, and the looser the texture of the wood, the greater is the 

 difficulty of working the saw ; in such cases the teeth do not 

 divide the fibres, but tear them from neighbouring fibres, 

 the section becomes rough and uneven and a large quantity of 

 sawdust is produced, all this indicating difficulty in the work. 

 Sawing becomes easier in the case of dense short-fibred wood 

 with coherent fibres, and smooth cuts with little sawdust result. 

 It is therefore easier to saw heavy than light broad-leaved 

 wood. Conifers are sawn most easily of all woods, owing 

 to their fimple anatomical structure and fine medullary rays. 



Moisture diminishes the hardness of wood, so that it is 

 easier to saw green w^ood than dry wood, but at the same 

 time, moisture increases the pliability of the fibres ; in the case 

 of heavy woods, this increase of pliability is not important. 



