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OBLIQUITY-ORTHOTOMIC.
Obliquity: the term, xiii, 234.
Observations (see Orbits, Planet’s Orbit, Solar Eclipse).
Octacron: enumeration of polyhedra, v, 38—44.
Octad : the term, I, 586, vn, 133, 152, xn, 590.
Octadic-quartic Surfaces: x, 51.
Octagon: theorem of eight points on a conic, vm, 92—4.
Octahedral Function : xr, 128—9.
Octahedron : axial system, v, 531—9 ; automorpliic function for, xi, 169, 179—83, 212—6.
Octaves : elliptic functions, r, 127, 586; imaginaries, i, 301.
Octavic Surface : vm, 401—3.
Octic Function : and Abelian function, xi, 483.
Octics: and twisted cubics, xn, 310.
Octic Surface : on a sibi-reciprocal, x, 252—5 ; (see also Surfaces).
Octo-dianome: the term, vn, 134.
Octo-hexahedron: the term, x, 328.
Odd Branch of Curve: x, 36.
Off-planes: the term, vi, 330, 577, 583—5.
Off-points : the term, vi, 330, 338, 577, 583—5.
Olbers, W.: orbits of asteroids, ix, 177.
Olivier, T.: conics inscribed in quadric surface, I, 557.
Omal: the word, vi, 194, 463, 467—9.
Omega Functions: the term, xi, 453; note on Smith’s memoir, xm, 558—9.
Omphali: the term, vm, 326.
Operandator: defined, in, 242.
Operations: and substitutions, xm, 530.
Operators: differential, vii, 8 ; and seminvariants, xm, 322—32; MacMahon’s multilinear, xm, 399.
Optics: MacCullagh’s theorem in polarized light, iv, 12—20; geometrical construction in, x, 28.
Orbits: Jacobi’s canonical formulae for disturbed motion, in, 76—7; reduction to fixed plane, iii,
91—6; variation in plane of planet’s, hi, 516—8; central forces problem, iv, 516—21; position
of, in planetary theory, vn, 541—5 ; of asteroid, and Newcomb, ix, 176—7; Hamiltonian equations
of central, x, 613; Sylvester’s work at, xm, 47; (see also Planetary Theory, Planet’s Orbit).
Order: of system of equations, I, 457—61, 589; of qualities, defined, n, 221; of curve, n, 569—83,
xi, 462 ; in abstract geometry, defined, vi, 463; of curve and surface, xi, 629.
Ordinary Point for Differential Equations: xn, 394.
Oriani, B.: elliptic motion, hi, 474, iv, 528.
Orr, W. McF.: tetrads of circles, xm, 425.
Orthocentre: the term, xm, 550.
Orthogonal Surfaces: vm, 269—91, 292, 569—70; Smith’s Prize dissertation, vm, 558—63.
Orthogonal Surfaces and Curvature, Memoir on: vm, 292—315; introductory, vm, 292—3 ; curvature
of surfaces, vm, 293—300; conormal correspondence of vicinal surfaces, vm, 301—8; condition that
the two surfaces may belong to orthogonal system, vm, 309—11; family of surfaces, vm, 312—5.
Orthomorphic Transformation (see Orthomorphosis).
Orthomorphosis: of circle into parabola, v, 618, xn, 328—36; of a circle into itself, xm, 20;
general theory, xm, 170—90; some problems, xm, 191—205; note on theory, xm, 418—24; (see
also Conformal Representation).
Orthotomic: the term, ix, 13.
Orthotomic Circles: and polyzomal curves, vi, 501; and Jacobians, vi, 568.
Orthotomic Curve: of a system of lines in a plane, xm, 346—7.
Orthotomic Surfaces: in Ency. Brit., xi, 637—8.
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