APTITUDE FOR BEING WORKED. Ill 



ally the greatest heat, and are favourite woods for heating 

 houses. Such are the woods of beech and hornbeam, olive- 

 wood, also that of evergreen oak. Finally, woods rich in 

 resin, such as torch wood and older pinewood of all species, 

 burn with long flames, but do not consume their carbon 

 completely, and give out much smoke and soot. Such wood 

 is excellent for steam-engines. 



Silver-fir twigs and needles are so rich in turpentine that 

 they will burn when freshly cut. Larchwood is a bad 

 combustible. Julius CaBsar calls it "Ufinum i<ini impcuctrabile." 



7. Aptitude of Wood* for liein<i Worked. 

 a. II ij 



The reaction of wood to cutting implements, such as the 

 chisel, axe and plane, depend on the direction in which the 

 force is used, and cutting is most difficult perpendicular to 

 its fibres, while cutting becomes easier the nearer the direction 

 of the force is to their direction, because their splitting assists 

 cutting. Hence with the axe it is easiest to cut obliquely. 

 In the case of softwood the fibres bend before the axe, and 

 heavy axes are required, which have more momentum and 

 penetration than light axes. For hardwoods lighter axes are 

 usual, as the fibres do not bend before the axe. 



The knife hardly deserves mention as a forest tool, but, 

 when used with the hand, its action unites that of the axe 

 and saw more than that of any other tool ; it affords, there- 

 fore, a suitable test for classifying the degrees of hardness of 

 woods approximately. 



Nordlinger, from average results obtained with different 

 tools, gives the following classification of woods according to 

 their hardness : 



Hard as bone: Barberry, box, privet, lilac. 



Very hard : Common dogwood (Conius unifi/iiiiea, L), yellow 

 dogwood (C. Mas, L.), whitehorn, blackthorn. 



Hard: Eobinia, field -maple, sycamore, hornbeam, wild 

 cherry, service-tree, buckthorn, elder, yew, pedunculate oak, 

 mahogany. 



Fairly hard; Ash, holly, mulberry, mountain - pine, 



