According to Rennie's experiments, the power of wood to resist crushing (a cube an inch square being used, and the power applied to the end of the grain) is as follows: -

Problem VIII. To Determine The Load Any Post Of Less Than Ten Times Its Diameter In Height Will Support Without Crushing

Rule. - Multiply the area of the post in inches by the weight that will crush a square-inch of the kind of wood. A fourth of the product is the greatest permanent load the post will bear with safety.

Only two other strains to which wood may be subjected need be noticed.

One is that exerted by the foot of a truss, rafter, or any thing of the kind, on the wood between it and the end of the tie-beam on which it stands; the tendency being to slide, or push off the wood. The quality which resists this is called the lateral adhesion. Experiments have proved that the soft woods, as spruce, pine, etc, will resist a force of from five to seven hundred pounds, and the hard woods, as oak and chestnut, from six to nine hundred pounds, to the square-inch. As no piece of good carpentry would be dependent on the simple adhesion of the wood alone for support, but, where the thrust is one of more than ordinary moment, bolts or straps should be employed, rules and further suggestions are uncalled for.

The other strain to which reference has been made is where the power tends to tear asunder the fibres of the wood in the direction of their length. (See corollary 6, page 48.) Experiments made on oak and chestnut show this resistance to be from nineteen hundred and fifty to twenty-six hundred pounds to the square-inch, and white pine and spruce from six hundred and fifty to twelve hundred pounds.