Annual parallax, the greatest value of the heliocentric parallax, or the greatest annual apparent change of place of a body as seen from the earth and sun; as, the annual parallax of a fixed star.Binocular parallax, the apparent difference in position of an object as seen separately by one eye, and then by the other, the head remaining unmoved.Diurnal, or Geocentric, parallax, the parallax of a body with reference to the earth's center. This is the kind of parallax that is generally understood when the term is used without qualification.Heliocentric parallax, the parallax of a body with reference to the sun, or the angle subtended at the body by lines drawn from it to the earth and sun; as, the heliocentric parallax of a planet.Horizontal parallax, the geocentric parallx of a heavenly body when in the horizon, or the angle subtended at the body by the earth's radius.Optical parallax, the apparent displacement in position undergone by an object when viewed by either eye singly. Brande & C. Parallax of the cross wires their apparent displacement when the eye changes its position, caused by their not being exactly in the focus of the object glass.Stellar parallax, the annual parallax of a fixed star.

(Par"al*lel) a. [F. parallèle, L. parallelus, fr. Gr. para` beside + of one another, fr. other, akin to L. alius. See Allien.]

1. (Geom.) Extended in the same direction, and in all parts equally distant; as, parallel lines; parallel planes.

Revolutions . . . parallel to the equinoctial.

Curved lines or curved planes are said to be parallel when they are in all parts equally distant.

2. Having the same direction or tendency; running side by side; being in accordance (with); tending to the same result; — used with to and with.

When honor runs parallel with the laws of God and our country, it can not be too much cherished.

3. Continuing a resemblance through many particulars; applicable in all essential parts; like; similar; as, a parallel case; a parallel passage. Addison.

Parallel bar. (a) (Steam Eng.) A rod in a parallel motion which is parallel with the working beam. (b) One of a pair of bars raised about five feet above the floor or ground, and parallel to each other, — used for gymnastic exercises.Parallel circles of a sphere, those circles of the sphere whose planes are parallel to each other.Parallel columns, or Parallels(Printing), two or more passages of reading matter printed side by side, for the purpose of emphasizing the similarity or discrepancy between them.Parallel forces(Mech.), forces which act in directions parallel to each other.Parallel motion. (a) (Mach.) A jointed system of links, rods, or bars, by which the motion of a reciprocating piece, as a piston rod, may be guided, either approximately or exactly in a straight line. Rankine. (b) (Mus.) The ascending or descending of two or more parts at fixed intervals, as thirds or sixths.Parallel rod(Locomotive Eng.), a metal rod that connects the crank pins of two or more driving wheels; — called also couping rod, in distinction from the connecting rod. See Illust. of Locomotive, in App.Parallel ruler, an instrument for drawing parallel lines, so constructed as to have the successive positions of the ruling edge parallel to each other; also, one consisting of two movable parts, the opposite edges of which are always parallel. - - Parallel sailing(Naut.), sailing on a parallel of latitude.Parallel sphere (Astron. & Geog.), that position of the sphere in which the circles of daily motion are parallel to the

1. The apparent displacement, or difference of position, of an object, as seen from two different stations, or points of view.

2. (Astron.) The apparent difference in position of a body (as the sun, or a star) as seen from some point on the earth's surface, and as seen from some other conventional point, as the earth's center or the sun.

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