tag="{http://www.w3.org/1999/xhtml}a">Part V.

When you cut off a stout stick, as the branch of a tree, you do not try to force your knife straight across with one cut. You cut a small notch and then widen and deepen it by cutting first on one side and then on the other (Fig. 5). The wood yields easily to the wedge on the side towards the notch, so that the edge can easily cut deeper, and thus the notch is gradually cut through the stick. The same principle is seen in cutting down a tree with an axe. You have only to look at the structure of a piece of wood when magnified, as roughly indicated in Fig. 6, to see why it is easier to cut with the grain than across it.