Ver·ti·cal a.
 1. Of or pertaining to the vertex; situated at the vertex, or highest point; directly overhead, or in the zenith; perpendicularly above one.
    Charity . . . is the vertical top of all religion.   --Jer. Taylor.
 2. Perpendicular to the plane of the horizon; upright; plumb; as, a vertical line.
 Vertical angle Astron. & Geod., an angle measured on a vertical circle, called an angle of elevation, or altitude, when reckoned from the horizon upward, and of depression when downward below the horizon.
 Vertical anthers Bot., such anthers as stand erect at the top of the filaments.
 Vertical circle Astron., an azimuth circle.  See under Azimuth.
 Vertical drill, an upright drill.  See under Upright.
 Vertical fire Mil., the fire, as of mortars, at high angles of elevation.
 Vertical leaves Bot., leaves which present their edges to the earth and the sky, and their faces to the horizon, as in the Australian species of Eucalyptus.
 Vertical limb, a graduated arc attached to an instrument, as a theodolite, for measuring vertical angles.
 Vertical line. (a) Dialing A line perpendicular to the horizon. (b) Conic Sections A right line drawn on the vertical plane, and passing through the vertex of the cone. (c) Surv. The direction of a plumb line; a line normal to the surface of still water. (d) Geom., Drawing, etc. A line parallel to the sides of a page or sheet, in distinction from a horizontal line parallel to the top or bottom.
 Vertical plane. (a) Conic Sections A plane passing through the vertex of a cone, and through its axis. (b) Projections Any plane which passes through a vertical line. (c) Persp. The plane passing through the point of sight, and perpendicular to the ground plane, and also to the picture.
 Vertical sash, a sash sliding up and down.   Cf. French sash, under 3d Sash.
 Vertical steam engine, a steam engine having the crank shaft vertically above or below a vertical cylinder.


 Az·i·muth n.  Astron. & Geodesy (a) The quadrant of an azimuth circle. (b) An arc of the horizon intercepted between the meridian of the place and a vertical circle passing through the center of any object; as, the azimuth of a star; the azimuth or bearing of a line surveying.
 Note: ☞ In trigonometrical surveying, it is customary to reckon the azimuth of a line from the south point of the horizon around by the west from 0° to 360°.
 Azimuth circle, or Vertical circle, one of the great circles of the sphere intersecting each other in the zenith and nadir, and cutting the horizon at right angles. --Hutton.
 Azimuth compass, a compass resembling the mariner's compass, but having the card divided into degrees instead of rhumbs, and having vertical sights; used for taking the magnetic azimuth of a heavenly body, in order to find, by comparison with the true azimuth, the variation of the needle.
 Azimuth dial, a dial whose stile or gnomon is at right angles to the plane of the horizon. --Hutton.
 Magnetic azimuth, an arc of the horizon, intercepted between the vertical circle passing through any object and the magnetic meridian. This is found by observing the object with an azimuth compass.

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 Cir·cle n.
 1. A plane figure, bounded by a single curve line called its circumference, every part of which is equally distant from a point within it, called the center.
 2. The line that bounds such a figure; a circumference; a ring.
 3. Astron. An instrument of observation, the graduated limb of which consists of an entire circle.
 Note: ☞ When it is fixed to a wall in an observatory, it is called a mural circle; when mounted with a telescope on an axis and in Y's, in the plane of the meridian, a meridian  circle or transit circle; when involving the principle of reflection, like the sextant, a reflecting circle; and when that of repeating an angle several times continuously along the graduated limb, a repeating circle.
 4. A round body; a sphere; an orb.
    It is he that sitteth upon the circle of the earth.   --Is. xi. 22.
 5. Compass; circuit; inclosure.
    In the circle of this forest.   --Shak.
 6. A company assembled, or conceived to assemble, about a central point of interest, or bound by a common tie; a class or division of society; a coterie; a set.
    As his name gradually became known, the circle of his acquaintance widened.   --Macaulay.
 7. A circular group of persons; a ring.
 8. A series ending where it begins, and repeating itself.
    Thus in a circle runs the peasant's pain.   --Dryden.
 9. Logic A form of argument in which two or more unproved statements are used to prove each other; inconclusive reasoning.
    That heavy bodies descend by gravity; and, again, that gravity is a quality whereby a heavy body descends, is an impertinent circle and teaches nothing.   --Glanvill.
 10. Indirect form of words; circumlocution. [R.]
 Has he given the lie,
 In circle, or oblique, or semicircle.   --J. Fletcher.
 11. A territorial division or district.
 Note: ☞ The Circles of the Holy Roman Empire, ten in number, were those principalities or provinces which had seats in the German Diet.
 Azimuth circle. See under Azimuth.
 Circle of altitude Astron., a circle parallel to the horizon, having its pole in the zenith; an almucantar.
 Circle of curvature. See Osculating circle of a curve (Below).
 Circle of declination. See under Declination.
 Circle of latitude. (a) Astron. A great circle perpendicular to the plane of the ecliptic, passing through its poles. (b) Spherical Projection A small circle of the sphere whose plane is perpendicular to the axis.
 Circles of longitude, lesser circles parallel to the ecliptic, diminishing as they recede from it.
 Circle of perpetual apparition, at any given place, the boundary of that space around the elevated pole, within which the stars never set. Its distance from the pole is equal to the latitude of the place.
 Circle of perpetual occultation, at any given place, the boundary of the space around the depressed pole, within which the stars never rise.
 Circle of the sphere, a circle upon the surface of the sphere, called a great circle when its plane passes through the center of the sphere; in all other cases, a small circle.
 Diurnal circle. See under Diurnal.
 Dress circle, a gallery in a theater, generally the one containing the prominent and more expensive seats.
 Druidical circles Eng. Antiq., a popular name for certain ancient inclosures formed by rude stones circularly arranged, as at Stonehenge, near Salisbury.
 Family circle, a gallery in a theater, usually one containing inexpensive seats.
 Horary circles Dialing, the lines on dials which show the hours.
 Osculating circle of a curve Geom., the circle which touches the curve at some point in the curve, and close to the point more nearly coincides with the curve than any other circle. This circle is used as a measure of the curvature of the curve at the point, and hence is called circle of curvature.
 Pitch circle. See under Pitch.
 Vertical circle, an azimuth circle.
 Voltaic circuit or Voltaic circle. See under Circuit.
 To square the circle. See under Square.
 Syn: -- Ring; circlet; compass; circuit; inclosure.


 vertical circle
      n : a great circle on the celestial sphere passing through the
          zenith and perpendicular to the horizon