POLF (1) (0. Eng. pd!, cf. Ger. Pfahl, Du. pact', from

See also:

• LAT

Lat.

See also:

• PALES

pales, stake)  , a tapering cylindrical post or stake of some considerable length, used as a support in scaffolding, for telegraph or telephone wires, hops, &c., and as a means for taking jumps (see POLE-VAULTING), and also as a single shaft for a vehicle drawn by two or more horses . As a measure of length a " pole," also called " rod " or " perch," is equal to 51 yds . (16 ft.), as a measure of area it is equal to 30; sq. yds . (2) (Lat. polus, adapted from Gr . 1roXos, pivot, axis), one or other of the extremities of the axis of the earth; the " celestial pole " is one or other of the points in the heavens to which the earth's axis points; in the northern hemisphere this point is near the star Ursae minoris, better known as the Pole-star or Polaris (see URSA MAJOR) . For the regions lying about the north and south poles of the earth see POLAR REGIONS . In mathematics the word pole has several meanings . In spherical trigonometry the " pole " of a circle on a sphere is the point where the diameter of the sphere perpendicular to the plane of the circle intersects the sphere . In crystallography (q.v.) the " pole " of a face is the intersection of a line perpendicular to the face with the sphere of projection . The term is also applied to a point from which lines radiate, as, for instance, the origin in a system of polar co-ordinates, or the common point of a pencil of rays . In the geometry of conic sections the " pole " of a line, termed the " polar " of the point, is the intersection of the tangents (either real or imaginary) at the points where the line meets the conic (see GEOMETRY: § Projective) . The " magnetic poles " of the earth are the points on the earth's surface where the dipping needle is vertical (see TERRESTRIAL MAGNETISM) ; and the " poles " of a magnet are the points of the magnet where the magnetic intensity is greatest .

In

electricity, the term is applied to the elements of a galvanic battery (q.v.), or to the terminals of a frictional electrical machine .