HAKDNBBS. 13 



of displacement, -which only brings the fibres closer together and 

 increases the hardness of the -wood at that point. Porous woods 

 offer most room for this displacement of the fibres, and, other cir- 

 cumstances being the same, possess the greatest degree of resistance. 

 The hardness due to toughness of the fibres manifests its.elf most 

 in a direction transverse to that in ■which they run. 



(c). The quantity of moisture present. — Dry wood is harder 

 than green -wood, firstly, because moisture softens the tissues, and 

 next, because green wood, being swollen up with moisture, occu- 

 pies for the same amount of solid matter, more space than dry 

 wood. The superior hardness in the dry state is more conspicu- 

 ous, the heavier the wood is. Dry Hardwichia hinata and ebony 

 are as hard as horn. In the case of very light tough woods, such 

 as willows, poplar, semal, &c., since the degree of toughness is in 

 proportion to the amount of contained moisture, the influence of 

 moisture on hardness becomes inconsiderable. The heartwood, 

 owing to the smaller quantity of water it contains, is always harder 

 than the sapwood, even when their respective weights are not very 

 different ; and for the same reason the older parts of a tree, pro- 

 vided of course they are still sound, are heavier than those which 

 are younger. 



(d). The quantity of resin and oil present. — Oil makes the 

 fibres tougher and fills up the interstices. In resinous woods, 

 however, hardness is in inverse proportion to the quantity of es- 

 sential oil present, since the oil keeps the resin in a soft condition. 

 Wood in which the resin is quite dry, as in stumps of deodar and 

 pine trees felled sometime ago, is almost as hard as horn. 



(e). The tool with which penetration is attempted. — The resist- 

 ance will be different according as we use a gimlet, or a file, or 

 a plane, or a saw, or a chisel, or sand paper, &c. Thus old posts, 

 exposed during years to every weather influence, of Hardwickia 

 hinata, khair and other woods that do not decay fiom exposure, 

 will defy all efforts to drive nails and bore holes into them, but 

 will nevertheless be easily cut up with a saw. We as foresters 

 need consider only the resistance offered to the axe and saw. 



In respect to the axe the greatest resistance to be overcome is 

 across the fibres, the least parallel to the fibres, especially in the 

 direction of the medullary plates and along the concentric rings of 

 growth, when these are well-marked. The resistance to be over- 

 come parallel to the fibres is connected with aptitude for fission, 

 and will, therefore, not be considered here. From what has gone 

 before it will have been seen that the resistance offered to an axe 

 driven across the fibres, whether perpendicularly or obliquely, 



