Page:Timber and Timber Trees, Native and Foreign.djvu/48

28 thirds the semi-diameter of the tree. This is of serious consequence to the converter who has to deal with it, as the defect completely separates the concentric layers

into segments of circles. The simplest form in which we find this shake (Figs. 8 a and b), is that of a straight line crossing the pith, and taking a direction in the same plane through the length of the stem. It will, however, be found in some specimens to have taken a twisting form, and on examining the top of the tree, the shake may be nearly at right angles to that at the butt-end (Fig. 9).

This is about the worst form, as it would involve a most serious loss in the conversion of the log if it were an object to reduce it into plank, and often necessitates its being employed in bulk.

The twist in the heart-shake just referred to is probably the result of an effort made by the tree to turn upon its base, which, I should think, might happen to trees produced in dense forests, where light and air are