Page:Timber and Timber Trees, Native and Foreign.djvu/40

20 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 layer; 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 will 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.

Trees are of course most valuable, as yielding the largest possible amount of good timber, just prior to the commencement of this change, which is indicated almost immediately it takes place by the topmost branches and branchlets becoming stunted and thick; being, in fact, what the surveyor or woodman would call "