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of the surface with a parallel to the tangent plane and indefinitely near it. It is an ellipse when the curvature is synclastic, and an hyperbola when the curvature is anticlastic.

The entrance of the moon into the shadow of the earth in eclipses, the sun's entrance into a sign, etc.

ematics; -- so called because one of the integrals expresses the length of an arc of an ellipse.

by John Kepler. They are these: (1) The orbit of a planet with respect to the sun is an ellipse, the sun being in one of the foci. (2) The areas swept over by a vector drawn from the sun to a planet are proportioned to the times of describing them. (3) The squares of the times of revolution of two planets are in the ra…

od of time, at the end of which, in the Julian calendar, the new and full moons and the eclipses recur on the same days of the week and month and year as in the previous period. It consists of 532 common years, being the least common multiple of the numbers of years in the cycle of the sun and the cycle of the moon.…

ate, n. Oblate ellipsoid or spheroid (Geom.), a solid generated by the revolution of an ellipse about its minor axis; an oblatum. See Ellipsoid of revolution, under Ellipsoid.

An oblate spheroid; a figure described by the revolution of an ellipse about its minor axis. Cf. Oblongum.

A prolate spheroid; a figure described by the revolution of an ellipse about its greater axis. Cf. Oblatum, and see Ellipsoid of revolution, under Ellipsoid.

ration of obscuring; the state of being obscured; as, the obscuration of the moon in an eclipse. Sir J. Herschel.

attention to; to notice with care; to see; to perceive; to discover; as, to observe an eclipse; to observe the color or fashion of a dress; to observe the movements of an army.

To eclipse; to hide from sight.

ight by the intervention of some other of the heavenly bodies; -- applied especially to eclipses of stars and planets by the moon, and to the eclipses of satellites of planets by their primaries.

Banishment; exclusion; as, social ostracism. Public envy is as an ostracism, that eclipseth men when they grow too great. Bacon. Sentenced to a perpetual ostracism from the . . . confidence, and honors, and emoluments of his country. A. Hamilton.

A body or figure in the shape of an egg, or popularly, of an ellipse. Cassinian oval (Geom.), the locus of a point the product of whose distances from two fixed points is constant; -- so called from Cassini, who first investigated the curve. Thus, in the diagram, if P moves so that P A.P B is constant, the point P desc…

Specifically (Conic Sections), in the ellipse and hyperbola, a third proportional to any diameter and its conjugate, or in the parabola, to any abscissa and the corresponding ordinate.

or affecting, a part only; not general or universal; not total or entire; as, a partial eclipse of the moon. "Partial dissolutions of the earth." T. Burnet.

In part; not totally; as, partially true; the sun partially eclipsed. Sir T. Browne.

The shadow cast, in an eclipse, where the light is partly, but not wholly, cut off by the intervening body; the space of partial illumination between the umbra, or perfect shadow, on all sides, and the full light. Sir I. Newton.

The circumference of a circle, ellipse, or other figure.

inary, or out of the usual course of nature, from which omens are drawn; a portent; as, eclipses and meteors were anciently deemed prodigies. So many terrors, voices, prodigies, May warn thee, as a sure foregoing sign. Milton.