POLES (Gr. polos, a turning-point), in geography, are the two extremities of the axis round which the earth revolves; they arc therefore situated the one on the n. and the other on The s. side of the equator, and equidistant from all parts of it. or in lat. n. and Iet. 00° south'. They are called the north and south poles of the earth.—In astronomy, the poles, which, for distinction's sake, arc frequently denominated " celestial poles." are those points in the heavens to which the earth's axis is directed, and round which the heavens seem to revolve. The celestial poles are valuable points of reference to astrono mers and geographers, so that the determination of their position in the heavens is a matter of the utmost importance. Unfortunately no stars mark their exact situation (see POLE-STAR) though there is a minute telescopic star only a few seconds from the north pole, which may he employed instead of it in rough observations—and therefore it is_ necessary to adopt some means for discovering its precise position. This is effected in the following manner; A bright star (generally the pole-star) is selected, and its position in its upper and its lower culminations (q.v.) is accurately noted; the point midway
between these two positions of the star is the pole of the heavens. The observation of toe star's two positions must be corrected for refraction, and it is for this reason that the pole-star is selected, since the effect of refraction is much the same in both positions of he star. The term "poles" has, hoWever, a wider application, as denoting the extremi ties of a line passing through the center of a great circle perpendicular to its plane; thus, we have the poles of the horizon (viz., the zenith and nadir), the poles of the ecliptic, the poles of a meridian; and in thesame sense, the terestrial and celestial poles are spoken of as the poles of the equator and equinoctial respectively.—Pole, in geometry, is used in a very indefinite sense; and in physics, it denotes those points of a body at which he attractive or repulsive energy is concentrated. See POLARITY.