Timber trees ng 



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. Artiticial means 

 {e.g. heating in special sheds or by electricit}') are now frequently 

 eraployed in order to shorten this period. The greatest care is 

 necessary in seasoning to avoid undue stresses and strains, \\'hich 

 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. ^ 



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 : 



A. Coniferous. 

 Douglas Fir or 



Oregon Pine . Pseudotsiiga doiiglasii (Rocky Mts.) (woodwork in build- 

 ings ).= 

 Larch . . Larix europeea (Europe) (sleepers, pit-props, etc.). 



Pitch Pine . Pinus palustris (United States) (constructional work). 



Red Deal . . Pinus sylvestris (Britain and Scandinavia) (building 



work) . 

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

 "White Pine . Abies pectinaia (S. Europe) (joinery). 



White or Yellow 



Pine . . Pinus strobus (N. America) (joinery). 



B. Dicotyledonous. 



Ash . . . 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. 



9 



