their functions are not fully understood. Polar circles (Astron. & Geog.), two circles, each at a
distance from a pole of the earth equal to the obliquity of the ecliptic, or about 23° 28&prime, the northern
called the arctic circle, and the southern the antarctic circle. Polar clock, a tube, containing a
polarizing apparatus, turning on an axis parallel to that of the earth, and indicating the hour of the day
on an hour circle, by being turned toward the plane of maximum polarization of the light of the sky, which
is always 90° from the sun. Polar coördinates. See under 3d Coördinate. Polar dial, a dial
whose plane is parallel to a great circle passing through the poles of the earth. Math. Dict. Polar
distance, the angular distance of any point on a sphere from one of its poles, particularly of a heavenly
body from the north pole of the heavens. Polar equation of a line or surface, an equation which
expresses the relation between the polar coördinates of every point of the line or surface. Polar forces
(Physics), forces that are developed and act in pairs, with opposite tendencies or properties in the two
elements, as magnetism, electricity, etc. Polar hare (Zoöl.), a large hare of Arctic America which
turns pure white in winter. It is probably a variety of the common European hare (L. timidus). Polar
lights, the aurora borealis or australis. Polar, or Polaric, opposition or contrast (Logic), an
opposition or contrast made by the existence of two opposite conceptions which are the extremes in a
species, as white and black in colors; hence, as great an opposition or contrast as possible. Polar
projection. See under Projection. Polar spherical triangle (Spherics), a spherical triangle whose
three angular points are poles of the sides of a given triangle. See 4th Pole, 2. Polar whale (Zoöl.),
the right whale, or bowhead. See Whale.
(Po"lar) n. (Conic Sections) The right line drawn through the two points of contact of the two
tangents drawn from a given point to a given conic section. The given point is called the pole of the
line. If the given point lies within the curve so that the two tangents become imaginary, there is still a
real polar line which does not meet the curve, but which possesses other properties of the polar. Thus
the focus and directrix are pole and polar. There are also poles and polar curves to curves of higher
degree than the second, and poles and polar planes to surfaces of the second degree.
(Pol"ar*chy) n. See Polyarchy.
(Po*lar"ic) a. See Polar. [R.]
(Po"lar*i*ly) adv. In a polary manner; with polarity. [R.] Sir T. Browne.
(Po`lar*im"e*ter) n. [Polar + -meter.] (Opt.) An instrument for determining the amount of
polarization of light, or the proportion of polarized light, in a partially polarized ray.
(Po`lar*im"e*try) n. (Opt.) The art or process of measuring the polarization of light.
(||Po*la"ris) n. [NL. See Polar.] (Astron.) The polestar. See North star, under North.
(Po*lar"i*scope) n. [Polar + -scope.] (Opt.) An instrument consisting essentially of a polarizer
and an analyzer, used for polarizing light, and analyzing its properties.
(Po*lar`i*scop"ic) a. (Opt.) Of or pertaining to the polariscope; obtained by the use of a
polariscope; as, polariscopic observations.
(Po`lar*is"co*py) n. (Opt.) The art or rocess of making observations with the polariscope.
(Po`lar*is"tic) a. Pertaining to, or exhibiting, poles; having a polar arrangement or disposition; arising
from, or dependent upon, the possession of poles or polar characteristics; as, polaristic antagonism.
(Po*lar"i*ty) n. [Cf. F. polarité.]
1. (Physics) That quality or condition of a body in virtue of which it exhibits opposite, or contrasted,
properties or powers, in opposite, or contrasted, parts or directions; or a condition giving rise to a contrast