76 TOOLS rOE FELLING AND OONVBHSION. 



steel is too highly tempered, it will break ; if not sufficiently 

 tempered, the edge will be turned. Soft-wooded trees require a 

 higher temper than hard-wooded trees. 



1. The felling axe. 



Action of the axe. — The action of an axe is to sever, to crush, 



and to shear. The severing and shearing actions are in direct, 



the crushing action in inverse, proportion to the sharpness of 



the edge and the thinness of the blade combined. When an axe 



is driven at right angles to the fibres, there is no shearing action 



at all, only severing and crushing ; but when the blow is delivered 



Fig. 19. obliquely, all three actions take place and the axe 



produces its greatest effect. Another reason why 



the obliquely driven axe penetrates further is that 



the lower lip of the wound it makes (see a in Fig. 



19), bends easily downwards and thus widens the 



gape, so as to allow the blade to continue its onward 



"* motion ; whereas when the cut is perpendicular to 



the axis of the tree, the severed fibres have to be 



crushed away longitudinally to produce a wider 



opening for the entry of the thicker hind portion 



of the blade into the wound. 



Weight of the axe-head. — This of course depends to some 

 extent on the strength of the axe-man, but it is essentially, regulat- 

 ed by the degree of hardness of the wood to be cut and the size 

 of the tree to be felled. The softer the wood, the more easily are 

 the fibres crushed and displaced, and, as a rule, also separated from 

 one another, whereas in hard wood the axe can do very little crush- 

 ing and comparatively little splitting, and must hence act chiefly 

 by severing. Hence hard woods require a lighter and thinner- 

 bladed axe than soft woods. Very light thin-bladed axes must 

 be used with small poles and saplings in coppice fellings to save 

 the roots from violent shocks and consequent rupture, and also 

 whenever the stem is so thin and pliant as to yield before the blow 

 from a heavier axe. Thus the weight of the felling axe for any- 

 thing above small poles varies from 1^ to 3^ lbs., the latter limit 

 being attained in the conifer forests of the Himalayas. For a 

 stem having a greater diameter than 6 inches the weight of the 

 axe should not be less than 2 lbs. For the special case of thin 

 yielding stems and of small poles in coppice fellings the weight 

 should be about 1 lb. more or less. 



Shape of the head. — The shape of the axe-head is extremely 

 varied, especially in India, where no machinery is employed in the 



