ckoned according to the order of signs. It is the sum
or difference of the right ascension and ascensional difference.

OBLIQUE BEARINGS. Consist in determining the position of a ship, by
observing with a compass the bearings of two or more objects on the
shore whose places are given on a chart, and drawing lines from those
places, so as to make angles with their meridians equal to the observed
bearings; the intersection of the line gives on the chart the position
of the ship. This is sometimes called the method of cross-bearings.

OBLIQUE SAILING. Is the reduction of the position of the ship from the
various courses made good, oblique to the meridian or parallel of
latitude. If a vessel sails north or south, it is simply a distance on
the meridian. If east or west, on the parallel, and refers to parallel
sailing. If oblique, it is solved by middle latitude, or Mercator
sailing.

OBLIQUE STEP. A movement in marching, in which the men, while advancing,
gradually take ground to the right or left.

OBLIQUITY OF THE ECLIPTIC. The angle between the planes of the ecliptic
and the equator, or the inclination of the earth's equator to the plane
of her annual path, upon which the seasons depend: this amounts at
present to about 23 deg. 27'.

OBLONG SQUARE. A name improperly given to a parallelogram. (_See_
THREE-SQUARE.)

OBSERVATION. In nautical astronomy, denotes the taking the sun, moon, or
stars' altitude with a quadrant or sextant, in order thereby to find the
latitude or time; also, the lunar distances.

OBSERVE, TO. To take a bearing or a celestial observation.

OBSIDIONAL CROWN. The highest ancient Roman military honour; the
decoration of the chief who raised a siege.

OBSTACLES. Chains, booms, abattis, snags, palisades, or anything placed
to impede an enemy's progress. Unforeseen hindrances.

OBTURATOR. A cover or valve in steam machinery.

OBTUSE ANGLE. One measuring above 90 deg., and therefore beyond a right
angle; called by shipwrights _standing bevellings_.

OBTUSE-ANGLED TRIANGLE. That which has one obtuse angle.

OCCIDENT. The west.

OCCULTATION. One heavenly body eclipsing another; but in nautical
astronomy it is particularly used to denote the eclipses of stars and
planets by the moon.

OCCUPY, TO. To take military possession.

OCEAN. This term, in its largest sense, is the whole body of salt water
which encompasses the globe, except the collection of inland seas,
lakes, and rivers: in a wor