upper mast.

TROACHER, OR TROAKER. A dealer in smuggled goods.

TROCHOID, OR CYCLOID. A geometrical curve, resulting from a circle being
made to run along a right line, whence the French designate it
_roulette_. But if a circle be made to roll along the circumference of
another circle, it becomes an _epicycloid_ (which see).

TROITE. An archaism for the cuttle-fish.

TROLLING. Drawing the bait along the water to imitate the swimming of a
real fish; this is generally done by a long line attached to the stern
of a sailing-boat. The word of old signified sauntering or idling about.

TROMBONE. A species of blunderbuss for boat service, taking its name
from its unseemly trumpet mouth.

TRONA. An article of export from Tripoli and Egypt; the _natron_ of
commerce, and _over munnoo_ of the East Indies. Sesqui-carb. of soda
mixed with salt and sulphate of soda.

TROOP. A company of cavalry, commanded by a captain, generally from
forty to sixty strong. Also, an assembling beat of the drum.--_Trooping
the guard_, or _the colours_, are special military ceremonies connected
with guard-mounting.--_Troop the guard._ A ceremony daily practised in
large ships by the marines at morning muster.

TROOP-BOATS. Are built with great flatness of floor, with extreme
breadth, carried well forward and aft, and possessing the utmost
buoyancy, as well as capacity for stowage. They were carried as
paddle-box boats (inverted), and thus protected the paddles as well as
being ready for use.

TROOP-SHIPS. A class of vessel of excellent account, during war, in the
hands of government; far preferable to hired transports for the purpose
of conveying soldiers, especially cavalry and their horses. They were
usually, in the last French war, 50's and 64's; and with the lower-deck
guns taken out, were roomy and airy.

TROPHY. Anything captured from an enemy and shown or treasured as a
token of victory.

TROPICAL MOTION. _See_ MOTION.

TROPICAL REVOLUTION. If the periodic time of a circuit round the sun be
taken in reference to the equinoxes or tropics, it is called a tropical
revolution.

TROPIC-BIRD. _Phaethon aethereus_, a well-known sea-bird, distinguished
by two very long feathers in its tail; also termed _boatswain-bird_,
from the tail feathers resembling a marline-spike.

TROPICS. Two imaginary lines upon the globe, or lesser circles of the
sphere, parallel to the equator, and at 23-1/2 deg. distance on each side
of it; they touch the ec