The Durability and Preservation of Woods 239 



in his woodlot. The following is a list of woods arranged 

 by H. von Schrenk in order of lasting power : — 



FACTORS INFLUENCING DURABILITY 



Durability is affected by very many conditions. The 

 greater the proportion of solid wood substance, the greater 

 the durability. Hence, the higher the specific gravity, 

 the longer a wood will last. This, however, applies only 

 to wood of the same species. Heavy red oak is more 

 durable than light red oak, but not nearly so durable as 

 light cedar. 



Broad-ringed hardwoods, that is, the trees that have 

 made more rapid diameter growth, are less durable than 

 narrow-ringed, or slow-grown hardwoods. Experiments 

 in Europe have shown a great difference. Coniferous, 

 or soft woods, pines, spruces, and so' on, are much more 

 durable when they have grown slowly and formed even, 

 narrow rings. Thus, we see that in growing timber for 

 durability, it is best to plant hardwoods in good soil, but 



