Volcanic ashes, used in cement, especially if required under
water.

PRACTICABLE. Said of a breach in a rampart when its slope offers a fair
means of ascent to an assaulting column.

PRACTICAL ASTRONOMY. A branch of science which includes the
determination of the magnitude, distance, and phenomena of the heavenly
bodies; the ready reduction of observations for tangible use in
navigation and geography; and the expert manipulation of astronomical
instruments.

PRAECURSORIAE. Ancient vessels which led or preceded the fleets.

PRAEDATORIAE, OR PRAEDATICAE. Long, swift, light ancient pirates.

PRAHU. [Malay for boat.] The larger war-vessels among the Malays, range
from 55 to 156 feet in length, and carry 76 to 96 rowers, with about 40
to 60 fighting men. The guns range from 2 inches to 6 inches bore, are
of brass, and mounted on stock-pieces, four to ten being the average.
These boats are remarkable for their swiftness.

PRAIA [Sp. _playa_]. The beach or strand on Portuguese coasts.

PRAIRIE. The natural meadows or tracts of gently undulating, wonderfully
fertile land, occupying so vast an extent of the great river-basins of
North America.

PRAM, OR PRAAM. A lighter used in Holland, and the ports of the Baltic,
for loading and unloading merchant ships. Some were fitted by the French
with heavy guns, for defending the smaller ports.

PRANKLE. A Channel term for the _prawn_.

PRATIQUE. A Mediterranean term, implying the license to trade and
communicate with any place after having performed the required
quarantine, or upon the production of a clean bill of health.

PRAWN. A marine crustacean larger than a shrimp, much esteemed as an
article of food.

PRAYER-BOOK. A smaller hand-stone than that which sailors call "bible;"
it is used to scrub in narrow crevices where a large holy-stone cannot
be used. (_See_ HOLY-STONE.)

PRECEDENCE. The order and degree of rank among officers of the two
services. (_See_ RANK.)

PRECESSION OF THE EQUINOXES. A slow motion of the equinoctial points in
the heavens, whereby the longitudes of the fixed stars are increased at
the present rate of about 50-1/4" annually, the equinox having a
retrograde motion to this amount. This effect is produced by the
attraction of the sun, moon, and planets upon the spheroidal figure of
the earth; the luni-solar precession is the joint effect of the sun and
moon only.

PREDY, OR PRIDDY. A word formerly used in our ships for "get ready;" as,
"Pre