34 TECHNICAL PROPERTIES OF WOOD. 



Birch, Aspoi, Spruce, SrotcJt Vine, SUvcr-nr, Larch and 

 Black Vnn: ^^^^ 



JSolid cubic foot of timber 35^ 



Stacked 100 cubic feet of split tireAvood billets . '2729 



Ditto, round billets *i7*29 



Ditto, rootwood . . . . . . . "ilSl 



[Thus a load of 40 cubic feet of hardwood weighs 16 cwt. 12 lbs., 

 and a load of 50 cubic feet of softwood weighs 15 cwt. 90 lbs., 

 the cubic meter being reckoned at 35"3 cubic feet and the kilogram 

 2-2 lbs.— Tr.] 



In the German timber-trade a solid cubic meter (Festmeter) 

 of wood is reckoned to weigh COO kilos = 12 centners. A 

 stacked cubic meter is termed Haummcter or Stcre. 



Section Y. — Haudness. 



The hardness of a body is its power of resisting the insertion 

 of another body into its mass. Woods which offer considerable 

 resistance to being worked by instruments are termed hard- 

 woods, and others which may be easily worked are termed 

 softwoods. 



Owing to the non-homogeneous character of wood, it is clear 

 that the resistance offered to working depends on whether the 

 instrument used is acting parallel to the direction of the fibres, 

 directly across them, or in a direction intermediate to these two. 

 Resistance parallel to the fibres is connected with the fissibility of 

 wood, which will be discussed further on. The resistance which 

 wood offers to instruments also varies with the kind and mode of 

 working of each instrument. If other factors arc considered 

 which influence the relative hardness of wood in diflerent cases, 

 it becomes evident that this property of wood is not nearly so 

 easily estimated as might at first sight be imagined. 



The factors on which the hardness of a wood depends are : — its 

 anatomical structure, the coherence of its fibres, the amount of 

 resin it contains, its degree of moisture, and the kind of instru- 

 ment used. 



1. Auatiunical Structure. 

 The more ligneous substance anv wood contains the greater 



