II.] DECAY OF TIMBER. 47 



at the centre. For this reason it becomes a matter of 

 great importance, in selecting timber for use — especially 

 if it be intended for works of any magnitude — that logs 

 should not be taken of dimensions much in excess of 

 the specification given, but corresponding as nearly as 

 possible in size to it, as the removal of more than a few 

 of the outer layers of heart-wood is likely to involve a 

 serious loss of strength. 



It should be observed that a tree does not cease 

 growing when it arrives at maturity. As long as it is 

 alive, it continues to increase in bulk by the addition of 

 the annual layers developed by the cambium ; but when 

 maturity is once passed, each succeeding year produces 

 a certain amount of deterioration at the centre. This 

 deterioration or decay appears in various stages, and 

 generally exhibits, in the first instance, either a white 

 or yellowish-red colour at the butt or root end of the 

 stem. If white, the defect is probably very slight, and 

 does not usually extend more than a few feet up ; but if 

 yellowish-red in colour, it is not unfrequently of a 

 more serious character. Again, if* the affected parts 

 have assumed a decidedly red tinge, the tree is said to 

 be, in technical language, " foxy," and is scarcely fit for 

 constructive purposes, as the decay tvill be found to 

 pervade a great portion of the tree. The further 

 advanced stage of deterioration is that which may be 

 described as a drying up or wasting away of the wood 

 immediately surrounding the pith, or medulla. It forms 

 a hollow, first at the butt, and then spreads upwards, 

 gradually increasing in size as the tree gets older, while 

 the defect may eventually reach even into the branches. 

 Many of these forms of "rot" are directly due to 

 parasitic fungi, and others are accompanied and hastened 

 by the ravages of these organisms. 



