rds from a sheer line; the term is nearly
synonymous with _flight_.--_To fly up in the wind_, is when a ship's
head comes suddenly to windward, by carelessness of the helmsman.

FLY-WHEEL. The regulator of a machine.

FOAM [Anglo-Saxon, _feam_]. The white froth produced by the collision of
the waves, or by the bow of a ship when acted on by the wind; and also
by their striking against rocks, vessels, or other bodies.

FOCAL LENGTH. The distance between the object-glass and the eye-piece of
a telescope.

FOCUS. A point where converging rays or lines meet.

FOEMAN. An enemy in war; now used only by poets. One of Falstaff's
recruits, hight Shadow, presented no mark to the enemy: "The foeman may
with as great aim level at the edge of a pen-knife."

F[OE]NUS NAUTICUM. Nautical usury, bottomry.

FOG. A mist at sea, consisting of the grosser vapours floating in the
air near the surface of the sea. The fog of the great bank of
Newfoundland is caused by the near proximity of warm and cold waters.
The air over the Gulf Stream, being warmer than that over the banks of
Newfoundland, is capable of keeping much more moisture in invisible
suspension; and when this air comes in contact with that above the cold
water, it parts with some of its moisture, or rather holds it in visible
suspension. There are also dry fogs, which are dust held in suspension,
as the so-called African dust, which often partially obscures the sun,
and reddens the sails of ships as they pass through the north-east
trades.

FOG-BANK. A dense haze, presenting the appearance of a thick cloud
resting upon the horizon; it is known in high latitudes as the precursor
of wind from the quarter in which it appears. From its frequent
resemblance to land it has obtained the name of _Cape Fly-away_.

FOG-BOW. A beautiful natural phenomenon incidental to high latitudes. It
appears opposite to the sun, and is usually broad and white, but
sometimes assumes the prismatic colours. Indicative of clearing off of
mists. (_See_ FOG-EATER.)

FOG-DOGS. Those transient prismatic breaks which occur in thick mists,
and considered good symptoms of the weather clearing.

FOG-EATER. A synonym of _fog-dog_ and _fog-bow_. It may be explained as
the clearing of the upper stratum, permitting the sun's rays to exhibit
at the horizon prismatic colours; hence "sun-gall."

FOGEY. An old-fashioned or singular person; an invalid soldier or
sailor. Often means a stupid but irascible fello