A cubical block of wood measuring twelve inches on a side floats on
water because it is lighter than water; it weighs, if yellow pine,
thirty-eight pounds, whereas the same volume of water weighs about
sixty-two pounds. Any substance weighing more than sixty-two pounds to
the cubic foot would sink in water.
[Illustration: BUOYANT POWER OF WOOD]
If our block of wood be drilled, and _lead_ poured in the hole, the
total size of wood-and-lead block being kept constantly at one cubic
foot, the block will sink as soon as its whole weight exceeds sixty-two
pounds. Ignoring the wood removed by boring (as, compared with the lead
which replaces it, an insignificant amount), the weight of lead plugged
in may reach twenty-four pounds before the block will sink.
This figure, twenty-four pounds, the difference between sixty-two and
thirty-eight pounds, then represents the maximum buoyant power of a
cubic foot of wood in water. It is the difference between the weight of
the wood block and the weight of the water it displaces. If any weight
less than this is added to that of the wood, the block will float,
projecting above the water's surface more or less, according to the
amount of weight buoyed up. It will not rise entirely from the water,
because to do this it would need to be lighter, not only than water,
but than air.
[Illustration: ONE CUBIC FOOT OF WOOD LOADED IN WATER]