DEFECTS IN TIMBER AND GENERAL NOTES 299 



It should be understood that when a timber is referred 

 to as durable, or fairly durable, this is only a comparative 

 term, and only applies to its use under conditions for which 

 it is adapted and generally used, because although some 

 classes of timber such as greenheart, jarrah, pitch pine, oak, 

 and many hardwoods may be used in most situations and 

 either for interior work or where exposed to the weather, 

 and will have a fairly long life in either, yet with many 

 other timbers it would be quite the contrary. For instance, 

 sycamore, poplar, and other softwoods which last for very 

 long periods if protected from the weather would not be at 

 all durable if placed in situations where they would be 

 alternately wet and dry, and no one would think of using 

 them in Great Britain for, say, a timber quay, irrespective 

 altogether of their want of strength. 



The durability or otherwise of timber in various situations 

 is very variable ; the poorest timber may, in a dry protected 

 situation, last for centuries; the best of timber in other situa- 

 tions will decay in a few years. Some of the softer woods 

 last longer as railway sleepers and this is about the most 

 severe test to which timber can be subjected, especially if 

 placed in a cinder ballasted track than some of the hard- 

 woods, which in ordinary situations could not compare with 

 them in point of longevity. Oak, as we have seen, will last 

 in fairly good condition in some places for 2,000 years, but 

 the best American oak, when used for railway sleepers, 

 only lasts eight or ten years, and in some situations will 

 decay in three years. In America, which is about the only 

 country in the world where large quantities of untreated 

 softwoods are used for railway sleepers, it has been found 

 that the comparatively soft red cedar, the arbor vitse, and 

 redwood resist decay best, as they are less affected by disease 

 than most timbers ; treated hemlock will not last so long 

 in some situations as untreated cedar ; some roads get a life 



