DURABILITY. 95 



perishable when exposed to the air and moisture and in hot 

 sandy soils. Larchwood tapped for resin has also little 

 durability. 



Beech : Is durable only in dry places and under water ; when 

 used in the ground it soon rots ; is very subject to be worm- 

 eaten. 



Hornbeam : Useful only in dry places under cover. 



Sycamore and Maples : Not liable to be worm-eaten ; durable 

 only when kept dry. 



Alder : Durable under water, otherwise very liable to decay and 

 to be worm-eaten. 



Wild cherry : Very liable to be worm-eaten. 



Birch : Utilizable for furniture and carriage-panels only when 

 kept dry. 



Aspen : Usually durable only when kept dry ; but old, reddish 

 aspen-wood is said to be durable. 



Lime : Durable, when kept dry, unless it is worm-eaten. 



Weyinouth-pine : Not durable, and not much prized, even in 

 its native localities. (American white deal.) 



Poplars, hazel and willows : Only durable when kept dry. 



6. Means of Increasing the Dnrahility of Timber. 



Since durability is of such importance in determining the 

 value of timber, it is evident that the greatest attention should 

 be paid to any means of increasing it. Here, only such means 

 will be considered as the forester can apply, and the question 

 of injecting timber will be deferred till the third part of the 

 book. 



It has been already shown how greatly the durability of timber 

 depends on the locality and exposure to light, and this points 

 out the way to produce durable timber by following certain 

 sylvicultural rules. 



The greatest possible care should be taken to select the proper 

 species for the locality. Fertile soils and mild climates are 

 necessary for most broad- leaved woods, the amount of light which 

 reaches the crown of the tree being gradually increased, and 

 when they have attained the period of maximum increment, the 

 crowns should be isolated from those of the surrounding trees. 

 Eor conifers, especially larch, spruce and silver-fir, mountainous 



