IRQ]                               NAUTICAL  DICTIONARY.

IRONS. A ship is said to be in irons, when, through mis¬
management, she will neither cast one way nor another.

ISLAND, or ISLE. A portion of land entirely surrounded
by water.

ISTHMUS. A narrow neck of land uniting a peninsula with
the adjoining land, or connecting two continents.
 

JACK, or UNION JACK. A small union flag formed by the
intersection of the red and white crosses. In merchant ships it
is bordered with white.    See Flag.

JACK-CROSS-TREES. Iron cross-trees at the head of any
long topgallant mast.    See Cross-trees.

JACK-SCREW. A purchase consisting of wheels and pinions
which work inside of a wooden frame, and act upon an iron bar
called the Spear;  used in stowing cotton, flax, and other goods.

JACK-STAFF. A staff set up on the outer end of a vessel's
bowsprit, to hoist the union jack upon.

JACK-STAYS. Ropes stretched taut along a yard, or iron
rods or strips of wood fixed to the yard, for bending the head of
a square sail to, There are sometimes jack-stays used for fore-
and-aft sails^to traverse; upon, instead of hoops sliding up and
down the mast: these formerly received the name of Traverse-
horses,                     jV-f ^ '''^'' "   ^^-^^ '^ ^' ('                  '''•■'■

JAM, or JAMB. A term applied to the act of anything being
confined, and also to the act of confining it, so that it is im¬
movable, or cannot be moved without difficulty. It is especially
applied to ropes.                       '    '

JAWS (Fr, Manches). Pieces of wood fixed upon the inner
ends of booms or gaffs, forming a semicircle so as to enclose the
after-part of the mast. The points of the jaws are sometimes
called Horns,

The Jaw-rope is a rope attached to the jaws to prevent a gaff
from coming off the mast.

JEARS, or JEERS. Strong tackles for hoisting lower yards.
The ropes employed to hoist upper yards and gaffs are called
Halyards.

JEPAN. The French name for a kind of raft used particularly
at Ceylon, and which is seen also on the coasts of the Gulf of
Manar.    (Diet, de Marine a voiles,)

JERQUING a vessel, A search performed by an officer of the
212