3.) As the load increases the projecting ends sometimes split horizontally.

(See Fig.

4.) The irregularities in the load are due to the fact that the fibres collapse a few at a time, beginning with those with the thinnest walls.

The projection of the ends increases the strength of the material directly beneath the compressing weight by introducing a beam action which helps support the load.

This influence is exerted for a short distance only.
[Illustration: FIG.