comes equal to the
increase of the force of gravity.

TERMINATOR. The line separating the illuminated from the dark portion of
the moon's disc.

TERM-PIECES, OR TERMS. Pieces of carved work on each side of the
taffrail upon the side stern-timber, and extending down as low as the
foot-rail of the balcony.

TERN, OR SEA-SWALLOW. A species of sea-bird, allied to the gulls, but
of smaller and lighter make, and with longer and more pointed wings and
tail; genus _Sterna_.

TERNARY SYSTEM. Three stars in close proximity, and found to be in
physical connection, as, for instance, {z} Cancri.

TERRADA. An Indian boat, otherwise called _tonee_. A large 'longshore
boat of the Gulf of Persia.

TERRAPIN (contracted by sailors into _turpin_ and _tenopen_). A
fresh-water tortoise, plentiful in America, and much esteemed for food.

TERREPLEIN. In fortification, the horizontal surface of the rampart in
rear of the parapet.

TERRESTRIAL REFRACTION. The property of the atmosphere by which objects
appear to be higher than they really are, and in certain cases producing
the effect called _deceptio visus_, and _fata morgana_.

TERRITORY. The protection of neutral territory operates to the
restitution of enemy's property captured within its limits. Since the
introduction of fire-arms that distance has usually been recognized to
be almost three English miles.

TERTIATE, TO. To examine whether a piece of ordnance is truly bored and
has its due proportion of metal in every part, especially at the vent,
the trunnions, and the muzzle.

TESTING A CHAIN-CABLE. Trying its strength by the hydraulic machine,
which strains it beyond what it is likely to undergo when in use.

TESTONE. A silver Papal coin, value 1_s._ 3_d._ A testone is also a
current coin in Portugal, consisting of 100 reis.

TETE DE PONT. A work covering the farther end of a bridge from assault
from the country beyond.

TEW, TO. To beat hemp.

THAUGHTS (properly ATHWARTS). _See_ THWARTS.

THEODOLITE. The theodolite, as used in land-surveying, levelling, &c.,
is well known. But the great theodolite, with its vertical circle and
telescope adapted to the observation of the heavenly bodies, as used by
nautical astronomers, commonly called an alt-azimuth instrument, is
almost an observatory _per se_. By this alone, within three hours on
each side of noon, the longitude, latitude, and magnetic variation of a
position may be determined.

THERE! A word added in hailing any