FISSIBILITY. 41 



Frost sometimes nullifies the fissibility of wood hj reducing 

 the elasticity of the fibres. Frozen wood is brittle, and the 

 difficulty of splitting it is further increased by the fact that the 

 wedge will not bite and falls out of the cleft. Resin also 

 increases the difficulty of splitting wood, as is easily seen in the 

 case of the lower resinous parts of Scotch pine-trees. 



4. Locality and Mode of Groicth. 



The eff"ect of the locality and mode of growth on the 

 fissibility of wood is considerable. Close growth and moist 

 soil favour' height-growth, straightness, length of fibres and 

 freedom from branches and knots ; producing straight and clean- 

 grained wood, which is easy to split. 



All poles grown in a dense wood and fast- grown coppice- 

 shoots of almost any species split easily, showing the favourable 

 efi'ects on fissibility of quick-growing crowded Avoods. Other 

 factors being equal, that part of a tree which has grown most 

 rapidly will split most easily, and this is most generally the 

 case Avith the upper part of a stem. 



5. Condudmg licmarks. 



Fissibility is an important propert}' of wood, for a number of 

 wood-manufactures depend on it and upon the convertibility of 

 trees into wood-fuel, which is much more readily and cheaply 

 eflected with fissile wood, such as that of conifers, than with 

 tough sycamore or hornbeam. 



A forester may easily detect the comparative fissibility of the 

 wood of a tree from its outward appearance. Considerable 

 length of stem, a clean bole, a uniformly and gently-tapering 

 stem, fine clefts in the bark (especially in oak, Scotch pine 

 and other trees with rhytidome, or coarse, dead bark), long 

 and straight bark-cracks, are all indices of fissibility of the 

 wood in a tree. The locality is also a certain index to an 

 expert, and so is a slight amount of heart-shake, visible on the 

 section of a felled tree. During the felling of very fissile trees, 

 after the stump has been half severed, the tree may split with 

 its own weight ; this frequently happens to tall beech-poles 

 grown in a crowded wood. 



The following: list of trees is arranged in their order of 



