In drying a log or pole with the bark on, most of the water must be evaporated through the ends, but in the case of peeled timbers and sawn boards the loss is greatest from the surface because the area exposed is so much greater.
The more rapid drying of the ends causes local shrinkage, and were the material sufficiently plastic the ends would become bluntly tapering.

The rigidity of the wood substance prevents this and the fibres are split apart.

Later, as the remainder of the stick dries many of the checks will come together, though some of the largest will remain and even increase in size as the drying proceeds.

(See Fig.

27.) [Illustration: FIG.