gni, 431;
brilliancy of, 454;
decline of, 455;
distance of, 456;
parallax of, 455

November meteors, 376, 377, 379

Nutation, and Bradley, 501

O

Oberon, 309, 559

Object-glasses, 11, 12, 14, 16, 19

Observatories, 9-28

Observatory, Cape of Good Hope, 27;
Dunsink, 12, 184;
Greenwich, 26, 314;
Lick, 16;
Paris, 22;
Uraniborg, 10;
Vienna, 14;
Washington, 226;
Yerkes, 16

Occultation, 102, 215

Oceanus Procellarum, 83

Opera-glass, 27, 28

Opposition of Mars, 209

Orbital moment of momentum, 552

Orbits of planets, 114, 115, 117;
dimensions, 139-143;
elliptical form, 138-140;
minor planets, 232, 234, 239;
not exactly circles, 135;
of satellites of Uranus, 310;
Sun the common focus, 139

Orgueil meteorite, the, 399

Orion, 4, 418

Orion, belt of, 418, 467;
brilliancy of, 418;
nebula in, 269, 461, 466-469

Orionis, a, 418, 482

Orionis, th, a multiple star, 318, 467

Ovifak meteorite, the, 407

P

Palisa and the minor planets, 234

Pallas, 233, 238

Parabolic path of comets, 338-340

Parallactic ellipse, 444

Parallax, 181, 182, 214, 443;
of stars, 507

Paris telescope, 22, 23

Pegasus, great square of, 413, 414

Peg-top, the, and the rotation of the Earth, 494

Pendulum for determining the force of the Earth's attraction, 205

Penumbra of Sun-spot, 51

Perihelion, 163

Periodic times of planets, 139-143, 558

Periodicity of Sun-spots, 41

Perseids, 400

Perseus, 415, 416, 429;
sword-handle, 462

Perturbation, planetary, 317-324, 346

Perturbations, theory of, 296

Petavius, 93

Peters, Professor, and charts of minor planets, 234;
and the derangement of Sirius, 427

Phases of the Moon, 71, 76

Phobos, 226, 551, 558

Photography, and practical astronomy, 25;
and the distance of 61 Cygni, 449;
Dr. Roberts and the nebula in Andromeda, 469;
Mr. Common and the nebula in Orion, 469;
Sir W. Huggins and the spectra of nebulae, 473

Photosphere, the, 37, 54

Physical nature of the stars, 477

Piazzi, discoverer of the first known minor planet, 203

Pickering, Professor, 218, 220, 255, 265;
and Betelgeuze, 482;
and planetary nebulae, 474;
and Saturn's satellites, 296;
and spectroscopic binaries, 486, 487

Pico, 89

Planetary motion, Kepler's laws of, 138, 141, 142, 147, 148

Planetary nebulae, 470

Planetary perturbation, 317-324

Planets, ancient ideas respecting, 2, 6;