TIMBER TREES 



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SAp and wafer, a process that in the open occupies from six 

 months to a year or even longer in the case of hard woods, and 

 about half the time for Coniferous timber. Artificial means 

 (e.g. heating; in special sheds or by electricity) are now frequently 

 employed in order ta shorten this period. The greatest care is 

 necessary in seasoning to avoid undue stresses and strains, which 

 bring about warping and splitting- of the trunk, defects that 

 commonly develop if the process be unduly hastened. This is 

 mainly due to the fact that the tangential shrinkage is consider- 

 ably greater than the radial. 1 



Another common defect is the " knots," which are constituted 

 by the vascular tissues of lateral branches that have become 

 embedded in the wood of the trunk ; in forestry their develop- 

 ment is checked by dense planting. 



In the following list are enumerated some of the more im- 

 portant timbers and the trees from which they are derived : 



Douglas Fir or 

 Oregon Pine . 



Larch 

 Pitch Pine 

 Red Deal . 



White Deal 

 White Pine 

 White or Yellow 

 Pine 



A. Coniferous. 



Pseudotsuga douglasii (Rocky Mts.) (woodwork in build- 

 ings). 2 



Larix europcea (Europe) (sleepers, pit-props, etc.). 



Pinus palustris (United States) (constructional work). 



Pinus sylvestris (Britain and Scandinavia) (building 

 work) . 



Picea excelsa (Norway) (paper-pulp, floor-boards, etc.). 



Abies pectinata (S. Europe) (joinery). 



Pinus strobus (N. America) (joinery). 



B. Dicotyledonous. 



>h . . . Fraxinus excelsior (Europe) (wheelwright's work, tool- 

 handles, aeroplanes, etc.). 



Beech . . Fagus sylvatica (Europe) (furniture and tools). 



Black Walnut . Juglans nigra (N. America) (furniture). 



Blue Gum . Eucalyptus globulus (Australia) (constructional work, 



piers). 



Birch . . Betula spp. (N. Europe) (furniture, cabinet-work, bob- 

 bins, etc.). 



Cedar Wood . Cedrela spp. (America) (cigar-boxes). 



1 The tangential shrinkage is often nearly double, and for this reason 

 radial cracks, that open wider and wider as the trunk dries, are not un- 

 common. 



2 A few only of the more important uses are mentioned in each case. 



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