(Quad"rant) n. [L. quadrans, -antis, a fourth part, a fourth of a whole, fr. quattuor four: cf. F.
quadrant, cadran. See Four, and cf. Cadrans.]
1. The fourth part; the quarter. [Obs.] Sir T. Browne.
2. (Geom.) The quarter of a circle, or of the circumference of a circle, an arc of 90°, or one subtending
a right angle at the center.
3. (Anal. (Geom.) One of the four parts into which a plane is divided by the coördinate axes. The upper
right-hand part is the first quadrant; the upper left-hand part the second; the lower left-hand part the
third; and the lower right-hand part the fourth quadrant.
4. An instrument for measuring altitudes, variously constructed and mounted for different specific uses
in astronomy, surveying, gunnery, etc., consisting commonly of a graduated arc of 90°, with an index or
vernier, and either plain or telescopic sights, and usually having a plumb line or spirit level for fixing the
vertical or horizontal direction.
Gunner's quadrant, an instrument consisting of a graduated limb, with a plumb line or spirit level, and
an arm by which it is applied to a cannon or mortar in adjusting it to the elevation required for attaining
the desired range. Gunter's quadrant. See Gunter's quadrant, in the Vocabulary. Hadley's
quadrant, a hand instrument used chiefly at sea to measure the altitude of the sun or other celestial
body in ascertaining the vessel's position. It consists of a frame in the form of an octant having a graduated
scale upon its arc, and an index arm, or alidade pivoted at its apex. Mirrors, called the index glass and
the horizon glass, are fixed one upon the index arm and the other upon one side of the frame, respectively.
When the instrument is held upright, the index arm may be swung so that the index glass will reflect
an image of the sun upon the horizon glass, and when the reflected image of the sun coincides, to the
observer's eye, with the horizon as seen directly through an opening at the side of the horizon glass, the
index shows the sun's altitude upon the scale; more properly, but less commonly, called an octant.
Quadrant of altitude, an appendage of the artificial globe, consisting of a slip of brass of the length of
a quadrant of one of the great circles of the globe, and graduated. It may be fitted to the meridian, and
being movable round to all points of the horizon, serves as a scale in measuring altitudes, azimuths, etc.
Quadrantal triangle, a spherical triangle having one side equal to a quadrant or arc of 90°. Quadrantal
versor, a versor that expresses rotation through one right angle.
(Quad*ran"tal) a. [L. quadrantalis containing the fourth fourth part of a measure.] (Geom.)
Of or pertaining to a quadrant; also, included in the fourth part of a circle; as, quadrantal space.
(Quad*ran"tal), n. [L.]
1. (Rom. Antiq.) A cubical vessel containing a Roman cubic foot, each side being a Roman square
foot; used as a measure.
2. A cube. [R.]
(Quad"rat) n. [F. quadrat, cadrat. See Quadrate.]
1. (Print.) A block of type metal lower than the letters, used in spacing and in blank lines. [Abbrev.
2. An old instrument used for taking altitudes; called also geometrical square, and line of shadows.
(Quad"rate) a. [L. quadratus squared, p. p. of quadrare to make four-cornered, to make
square, to square, to fit, suit, from quadrus square, quattuor four. See Quadrant, and cf. Quadrat,
Quarry an arrow, Square.]