successive piece from the
center outward is lighter than its neighbor.

Examining the pieces, this difference is not as readily explained by
the appearance of each piece as in the case of pine wood.
Nevertheless, one conspicuous point appears at once. The pores, so
very distinct in oak, are very minute in the wood near the center, and
thus the wood is far less porous.

Studying different trees, it is found that in the pines, wood with
narrow rings is just as heavy as and often heavier than the wood with
wider rings; but if the rings are unusually narrow in any part of the
disk, the wood has a lighter color; that is, there is less summer-wood
and therefore less weight.

In oak, ash, or elm trees of thrifty growth, the rings, fairly wide
(not less than one-twelfth inch), always form the heaviest wood, while
any piece with very narrow rings is light. On the other hand, the
weight of a piece of hard maple or birch is quite independent of the
width of its rings.

The bases of limbs (knots) are usually heavy, very heavy in conifers,
and also the wood which surrounds them, but generally the wood of the
limbs is lighter than that of the stem, and the wood of the roots is
the lightest.

In general, it may be said that none of the native woods in common use
in this country are when dry as heavy as water, _i.e._, sixty-two
pounds to the cubic foot. Few exceed fifty pounds, while most of them
fall below forty pounds, and much of the pine and other coniferous
wood weigh less than thirty pounds per cubic foot. The weight of the
wood is in itself an important quality. Weight assists in
distinguishing maple from poplar. Lightness coupled with great
strength and stiffness recommends wood for a thousand different uses.
To a large extent weight predicates the strength of the wood, at least
in the same species, so that a heavy piece of oak will exceed in
strength a light piece of the same species, and in pine it appears
probable that, weight for weight, the strength of the wood of various
pines is nearly equal.

WEIGHT OF KILN-DRIED WOOD OF DIFFERENT SPECIES
-----------------------------------------+----------------------------
| Approximate
|----------+-----------------
| | Weight of
| |---------+-------
Species