Book 6 — INDEX.

A.

Aberration (see Chromatic Aberration, Spherical Aberration)

Absorption, general and selective, 403, 408; spectroscope arranged for showing, 409

Adjustment of the transit instrument, 238

Adjustments of the Equatorial (Chap. XXI.), 328

Achromaticity of Huyghen’s eyepiece, 110

Achromatic lenses, 84, 86

Achromatism, 126

Airy’s transit circle, 284

Alexandrian Museum, astronomical observations, 19

Alt-azimuth, 287, 289

Altitudes, instrument used by Ptolemy for measuring, 35

Aluminium, line spectrum of, 406; the sun, 417

Analyser for polarization of light, 443, 450

Anaximander, his theory of the form of the earth, 6; invention of the gnomon ascribed to him, 16, 17; meridian observations by, 25

Anchor escapement, 197

Angles of position, measurement of, 358-366, 372

Ångström, spectrum analysis, 402, 412; wave-lengths, 406

Annealing of lenses and specula, 121

Archimedes, clocks used by, 176

Arcturus, heat of, 385

Argelander, magnitudes of stars, 382

Aries, its position in the zodiac, 34

Aristillus, his observations in the Alexandrian Museum, 19

486Armillæ Æquatoriæ of Tycho Brahe, 26, 41, 45; his Armillæ Zodiacales, 28

Ascension, Right (see Right Ascension)

Arctic circle, Euclid’s observations of stars in the, 10

Astrolabe, invented by Hipparchus, 25; engraving of Tycho Brahe’s, 26, 41; his ecliptic astrolabe, 28

Astronomical clock, 240 (see Clock)

ASTRONOMICAL PHYSICS (Book VI.), 371

Astronomy of Precision, Instruments used in (Chap. XIX.), 284-290

Astrophotometer, Zöllner’s, 379

Autolycus, first map of the stars by, 8, 9

Automatic spectroscope, 397

Auzout, invention of micrometer ascribed to, 219, 221

Axis of collimation, 218, 220

B.

Barium, in the sun, 419

Barlow, correction of aberration in lenses, 88; “Barlow lenses,” 89, 229

Barometrical pressure, its effect on the pendulum, 193

Berthon’s dynameter, 116

Bessel’s transit instrument, 284

Binary stars, 351, 359, 360

Blair (Dr.), object-glasses, 88

Bloxam’s improved gravity escapement, 201

Bond (Prof.), spring governor, 320, 321; celestial photography, 463

Bouguer’s photometer, 379

Brahe, Tycho (see Tycho Brahe)

487Brewster (Sir David), his list of Tycho Brahe’s instruments, 38; spectrum analysis, 410

British Horological Institute, time signals, 280

Browning’s method of silvering glass specula, 137; of mounting specula, 144; automatic spectroscope, 397; solar spectroscope, 428

Bunsen (Ernest de), on ancient astronomical observations, 6

Bunsen (Prof.) spectroscope, 396; his burner, flame of, 407; his work in spectrum analysis, 402, 412, 423

C.

Calcium, line spectra of, 406, 418

Cambridge Observatory (U.S.), equatorial at, 339; star spectroscope, 430; transit circle, 247, 248, 251

Camera, enlarging, for celestial photography, 458

Canada balsam, its power of refracting light, 447

Candles used to measure time, 176

Canopus, observations of, by Posidonius, 8

Cassegrain’s reflecting telescope, 103, 149, 169; with Mr. Grubb’s mounting, 301

Casting lenses and specula, 121

Castor, photograph of, 478

Catalogues of stars (see Stars)

Celestial globe, 23

Celestial Photography (Chap. XXXI., XXXII.), 454

Chair, observing, for equatorial telescopes, 339

Chaldeans, their observations of the motions of the moon, 4; early use of the gnomon, 16

Chance and Feil, manufacture of glass discs, 119, 305

Chemistry of the Stars (Chap. XXVII.-XXX.), 386-453

Chinese, observations of conjunctions of planets, 4, 5; early use of the gnomon, 16, 17

Chromatic aberration of object-glasses and eyepieces, 87, 109, 123

Chronograph, The (Chap. XVII.), 253-270

“Chronographic method” of transit observation, 259

Chronograph at Greenwich Observatory, 260-264

Chronometer, The (Chap. XIII.), rise and progress of time-keeping, 206-210; 488compensating balance, 207; detached lever escapement, 208; chronometer escapement fusee, 209

Chronometers used for determining “local time,” 281

Chronophers, for distributing “Greenwich time,” 275, 276

Cincinnati Observatory, 338

Circle, the; its first application as an astronomical instrument, 6, 7, 8, 10; division into degrees, 8, 17, 21

Circles, great, defined by Euclid, 12

Circle Reading (Chap. XIV.), 211-217; Digges’ diagonal scale, 213; the vernier, 214

Circle, Transit (see Transit Circle)

Circle, meridian, at Cambridge (U.S.), 248; mural, 241, 242

Circumpolar stars, 239

Clarke (Alvan), improvement in telescope lenses, 305; great equatorial at Washington, 309, 319

Clement, inventor of the anchor escapement, 197

Clepsydras, 36

Clock, The (Chap. XIII.), 175-205; ancient escapement, 177; crown wheel, 178; clock train, 180; winding arrangements, 181; pendulum, 183; cycloidal pendulum, 185; compensating pendulums, 187; Graham’s, Harrison’s, and Greenwich pendulums, 188; clock at Royal Observatory, Greenwich, 194; escapements, 196; anchor escapement, 197; Graham’s dead-beat, 199; Mudge’s gravity escapement, 200; escapement of clock at Greenwich, 203; arrangements at Edinburgh Observatory, 269; astronomical, 240, 244, 245, 346; sidereal, 254, 256, 266; solar, 254; standard, at Greenwich, 194, 203, 204, 271, 274

Clock, driving, for large telescopes, 318

Clocks driven and controlled by electricity, 272

Clock stars, 267

Clock tower at Westminster, 277

Coggia’s comet, its light polarized, 450

Collimation and collimation-error in the transit instrument and equatorial, 238, 247, 328

Colour, amount produced by a lens, 81, 84, 86; spectrum analysis, 407, 408, 414, 416; 489of stars, 165, 351, 433; of waves of light, 420; refrangibility of, 387

Comet of 1677, discovered by Tycho Brahe, 47

Comet, measurement of the angle of position of its axis, 359

Comparison prism of the spectroscope, 423

Compensating balance, 207

Compensating pendulums, 187-193

Composite mounting of large telescopes, 310

Concave lenses (see Lenses)

Concave mirrors (see Mirrors)

Conjugate images, 64

Conjunctions of planets, first observations, 4

Constellations, first observations, 5, 9; Orion and its neighbourhood, 156

Convex lenses (see Lenses)

Convex mirrors (see Mirrors)

Cooke, adjustment of object-glasses, 141; improvement in telescope lenses, 305; equatorial refractor, 300; driving clock for large telescopes, 321; illuminating lamp for equatorial telescopes, 326

Copernicus, parallactic rules of, 41

Copernicus (lunar crater), 354

Cross wires for circle reading, 212, 216, 218; in transit eyepiece, 234, 257

Crown-glass prisms, 83, 84; lenses, 86, 88

Crystals of Iceland spar, double refraction by (see Iceland Spar)

Culmination of stars, first observations of, 5

Cycloidal pendulum, 185

D.

Dawes, solar eyepiece, 114, 115, 349; photometry, 378

Day, solar and sidereal, 253, 254, 256

Day eyepiece, 113

Days, first reckoning of, 19; measurement of, 176

Dead-beat escapement, 198

Deal time-ball, 275, 279

Declination, 24, 234, 241, 243, 251; measured by Tycho Brahe, 45

Declination axis of the equatorial, 299, 308, 327, 328

Defining power of the modern telescope, 160, 164; stars in Orion a test of, 165

Degrees, division of the circle into, 8, 17, 21

490De La Rue (Warren, F.R.S.), his reflecting telescope, 108; improvements in polishing specula, 134; celestial photography, 454, 459, 460, 464, 465, 475

Denderah, the zodiac of, 7

Dent (E. & Co.), clock at Royal Observatory, Greenwich, 194, 203, 204, 271, 274

Detached lever escapement, 208

Deviation of light, 79, 82

Deviation error in the transit instrument, 240, 248

Dials of ancient clocks, 257

Diagonal scale, Digges’, 213

Differential observations made with the equatorial, 367

Digges’ diagonal scale, 213

Diogenes Laertes, on the invention of the gnomon, 16

Dioptrics, Kepler’s treatise on, 386

Direct vision spectroscope, 431

Dispersion of light by prism, 79, 80, 82

Dividing power of telescopes, 165

Dollond, experiments with lenses, 85; correction of chromatic aberration, 89; on manufacture of flint-glass discs, 118; pancratic eyepiece, 113

Dome form of observatory, 338, 339

Double stars, 351, 359; measurement of, 360

Double-image micrometer, 225, 229

Double refraction by crystals of Iceland spar (see Iceland Spar)

Driving clock, for large telescopes, 318, 346

Drum form of observatory, 338

Dundee time signal, 278

E.

Earth, The, its position in Ptolemy’s system, 3; early theories of its form, 6; circumference measured by Posidonius, 8; Euclid’s theory of its position, 12; inclination of its axis, 14, 17; size measured by Eratosthenes, 19; position in Tycho Brahe’s system, 46

Eclipses, first observations of, 4; eclipses of Jupiter’s moons; eclipses, solar, photograph of, 474

Ecliptic, plane of the, 13, 14; discovery of its inclination, 17; inclination measured by Eratosthenes, 19

Ecliptic astrolabe of Tycho Brahe, 28

491Edinburgh Observatory, clock arrangements at, 269; standard clock, 272; time signals, 278

Egyptians, their record of eclipses, 4; zodiac of Denderah, 7

Eichens, his equatorial telescope at Paris, 314, 315; siderostat constructed by him, 344

Electricity, its application to the chronograph, 265; to driving and controlling clocks, 272

Electric lamp, 404; arranged for spectrum analysis, 405

Emery used in grinding lenses and specula, 127

English mounting of large telescopes, 310

Equation of time, 254

EQUATORIAL, THE (Book V.), 293-368 (see Telescopes)

Equatorial Observatory, The (Chap. XXII.), 337-342 (see Observatories)

Equatorial, The; its ordinary work, (Chap. XXIV.), 349-368

Equinoctial circle, observations of, by Euclid, 11

Equinoxes, first observations of, 15, 16, 17, 22; precession of the, 33

Eratosthenes, observations of, 17; his measurement of the earth, and inclination of the ecliptic, 19; meridian circle invented by, 20

Erecting eyepiece, 113

Errors, collimation and deviation, in the transit instrument, 238, 240, 247, 328

Errors; personal equation, 259; adjustments of the equatorial, 329

Ertel, vertical circle designed by, 290

Escapements of clocks, 196-205; ancient, 177; anchor, 197; Graham’s, 199; Mudge’s, 200; Greenwich clock, 203; detached lever, 208; chronometer escapement, 209

Ethereal vibrations, 373, 401, 410, 420, 449, 450

Euclid, his observations of the stars, 8, 9, 10; of great circles, horizon, meridian and tropics, 11, 12; theory of the earth’s position, 12; pole star, 14

Extra-meridional observations, first employment of, 23, 25

“Eye and ear” method in transit observations, 259

Eyeball, section of the, 66

Eyepieces, Huyghen’s, 110; Ramsden’s, Dollond’s, 112; 492erecting or “day eyepiece,” 112; Dawes’s solar eyepiece, 114; magnifying power of, 116

Eyepiece of Greenwich transit circle, 246; of transit instrument, 257

F.

Faye, M., celestial photography, 456

Feil and Chance, manufacture of flint glass discs, 119, 305

Fixed stars (see Stars)

Flame of salts in a Bunsen’s burner, 407

Flint-glass prisms, 83, 84; lenses, 86, 170

Flint-glass, improvements in the manufacture of discs of, 118, 119, 305

Focal length of telescopes, 82, 458; of lenses, 62, 63; of convex mirrors, 94

Foucault; his reflecting telescope, 108; improvement of specula, 117; mode of polishing specula, 134, 136; mounting of his telescope, 311; governor of driving clock for large telescopes, 323; siderostat, 343; spectrum analysis, 410; heliostat, 424

Fraunhofer; manufacture of flint-glass discs, 118; large telescopes, 303; lines in the solar spectrum, 392; spectrum analysis, 402, 410, 422, 425, 432, 438

Frederick II. of Denmark, his patronage of Tycho Brahe, 38

Fusee for chronometers, 209

G.

Galileo; his telescopes, 73, 78; their magnifying power, 77; the pendulum, 183, 184

Gascoigne, eyepieces and circle reading, 212; cross wires for “telescopic sight,” 219

Gateshead, Mr. Newall’s refractor, 302

Geissler’s tubes, 413

German mounting of large telescopes, 299

Gizeh, great pyramid of, an astronomical instrument, 6

Glasgow, electric time-gun, 278

Glass, injurious effects of the duty on, 305

Glass specula, methods of silvering, 137

Globe, celestial, 23; terrestrial, 23

Gnomon; its invention and early use, 16; improvements in, 18, 175

493Graham; dead-beat escapement, 192, 199; mercurial pendulum, 188

Gravity escapement, 200, 202

Greeks, their early use of the gnomon, 16

Greenwich, Royal Observatory; perspective view and plan of transit circle, 243, 245, 251; transit room, 251, 257; meridian of, 252; chronograph, 260-264; computing room, 267; standard sidereal clock, 267; mean solar time clock, 268; standard clock, 274; pendulum, 188; reflex zenith tube, 286; alt-azimuth, 290; equatorial, 310; thermopile, 384; photoheliograph, 469

“Greenwich Time” and the use made of it (Chap. XVIII.), 271-283

Gregorian telescope, 149

Gridiron pendulum, 188, 189, 192

Grinding of lenses and specula, 127

Grubb; production and polishing of metallic specula, 121, 134; adjustment of object-glasses, 141; Cassegrainian and Newtonian reflectors, 102, 108, 301, 303; great Melbourne equatorial telescope, 108, 314, 315, 317, 324, 327; mode of mounting its speculum, 145-149; automatic spectroscope, 397; solar spectroscope, 428

Guinand, manufacture of flint-glass discs, 118

Guns fired as time-signals, 278

H.

Haliburton, on ancient astronomical observations, 6

Hall; experiments with lenses, 85; manufacture of flint-glass discs, 118

Harcourt, Vernon, experiments with phosphatic glass, 123

Harrison’s gridiron pendulum, 188

Heat of Stars, Determination of (Chap. XXVI.), 377-385

Heliometer, 224

Heliostat, 423, 458

Henry (Prof.), radiation of heat from sun-spots, 385

Herschel (Sir John), lenses corrected for aberration, 88; table of reflective powers, 169; star magnitudes, 381

Herschel, Sir William, his reflecting telescopes, 103, 108; his mode of polishing specula, 129; great telescope at Slough, 169, 294

Herschel-Browning direct-vision prism, 400

494Hipparchus, trigonometrical tables constructed by, 17; discoveries of, 25-35; his measurement of space, 213

Hittorf, spectrum analysis, 413

Holmes (N. J.), his proposal of the electric time-gun, 278

Hooke, improvement in clock escapements, 196; micrometer, 221, 222; zenith sector invented by, 285; siderostat suggested by, 343

Horizon, the first astronomical instrument, 4, 7, 8; defined by Euclid, 12

Horological Institute, time-signals, 280

Hours, first reckoning of, 19; measurement of, 176

Hour circle of the equatorial telescope, 328, 335

Huen, island of, granted to Tycho Brahe, 38

Huggins (Dr.), telespectroscope, 429, 432

Huyghens; telescopes used by, 81; eyepiece, 110, 116, 212; application of the pendulum to clocks, 183; his measurements of space, 219, 223, 343; polarized light, 442

Hydrogen in the sun, 435

I.

Iceland spar crystals; double refraction by, 226, 228; polarization of light, 442, 445, 447, 449, 450

Illuminating power of the telescope, 158, 166, 168, 169; stars in Orion, a test of, 164

Images, double, seen through Iceland spar, 227

Inclination of the earth’s axis, 14, 17

Inclination of the ecliptic, 17; measured by Eratosthenes, 19

Index error, adjustments of the equatorial, 330

Iron, line spectrum of, 406, 418

Irrationality of the spectrum, 87

J.

Janssen (Dr.), solar photography, 471; discoveries in solar physics, 472

Jupiter, in Ptolemy’s system, 3; in Tycho Brahe’s, 46; as a telescopic object, 351; photographs of, 465, 466

Jupiter’s moons, observation of their eclipses to determine “local time,” 282

495K.

Kepler’s treatise on dioptrics, 386

Kew Observatory, photographs of the sun and sun-spots, 460, 465, 470, 475

Kirchhoff; spectroscope, 396; spectrum analysis, 402, 403, 412, 422, 428

Kitchener (Dr.), improved eyepiece, 113; stars in Orion, 164

Knobel’s photometer, 378

Knott, star magnitudes, 381

L.

Lamp for equatorial telescope, 325

Lamp, electric (see Electric Lamp)

Lassell; his Newtonian telescope, 108, 311; production, polishing, and mounting metallic specula, 121, 132, 144

Latitude; observations of Posidonius, 8; parallels of, 23

Lattice-work for tubes of telescopes, 172

Lenses; action of, 55, 58, 85; concave and convex, 61, 71, 75; amount of colour produced by, 81; achromatic, 84; Hall and Dollond’s experiments, 85; correction for colour, 87; correction for aberration in eyepieces, 109, 116; production of, 117

Lens, crystalline, of the eye, 67

Lewis (Sir G. C.), his “Astronomy of the Ancients,” 9

Liebig, improvement in specula, 117

Light; refraction, 55-72; deviation and dispersion, 79, 80, 82, 83; decomposition and recomposition, 83; reflection, 90-99; action of a reflecting surface, 91; angles of incidence and reflection, 92; concave and convex mirrors, 94-98; velocity of, 159; loss due to reflection, 168; effective, in reflectors, 169; vibration of particles, 373, 401; polarization, 441-453

Light of Stars, Determination of (Chap. XXVI.), 377-385

Lindsay (Lord), siderostat at his observatory, 347

Local time, 281

Longitude, meridians of, 23; as determined by Hipparchus and Tycho Brahe, 44; determined by clock and transit instrument, 280; expressed in degrees and time, 280

496M.

Magnesium vapour; colour of, 416; in the sun, 435

Magnifying power of large telescopes, 154, 155; stars in Orion, a test of, 163

Magnitude of stars, 377

Malus, discovery of polarization by reflection, 442, 448

Malvasia (Marquis), his micrometer, 219, 221

Manlius, gnomon erected by him at Rome, 18

Maps of the stars (see Stars)

Mars, in Ptolemy’s system, 3; in Tycho Brahe’s, 46; as a telescopic object, 350

Martin’s method of silvering glass specula, 138

Mauritius, photoheliograph at, 469

Mean time, 254

Mean solar time clock at Greenwich, 268

Melbourne Observatory, great reflecting telescope, 312, 313, 337; composition and production of specula, 120, 121, 129; view of optical part, 143; mode of mounting speculum, 144-149; photographs of the moon, 459

Mercurial pendulum, 187, 188, 192

Mercury, in Ptolemy’s system, 3; in Tycho Brahe’s, 46; as a telescopic object, 350

Meridian, defined by Euclid, 12

Meridional observations, first employment of, 20

Meridian of Greenwich, 252

Meridian circle, the first, 20; at Cambridge (U.S.), 248

Meridians of longitude (see Longitude)

MERIDIONAL OBSERVATIONS, MODERN (Book IV.), 233-290

Merz (M.), manufacture of flint-glass discs, 119; cost of large object-glasses, 172; large telescopes, 303

Metallic specula, 120, 171

Meton, meridian observations by, 25

Meudon Observatory, solar photography at, 470

Micrometer, The (Chap. XV.), 218-232; wire micrometer, 221, 352; heliometer, 224; double image, 229; position, 353; measurements made by, 355, 359-366, 368

Microscopes, for reading transit circles, 247; for Newall’s telescope, 307

Middlesborough, time signal, 278

Milky Way, observations of Euclid, 11

497Miller, spectrum analysis, 410

Mirrors, concave and convex, 94-98

Mirrors for reflecting telescopes (see Specula)

MODERN MERIDIONAL OBSERVATIONS (Book IV.), 233-290

Molecular vibration, 373, 401, 410, 429, 449, 450

Months, first observations of, 5

Moon, The, in Ptolemy’s system, 3; motions observed by the Chaldeans, 4; parallax observed by Ptolemy, 35; used by Hipparchus to determine longitude, 44; as a telescopic object, 350; the lunar crater, Copernicus, 354; measurement of shadow thrown by a lunar hill, 355; photographs and stereographs, 459, 464, 465, 466; part of Beer and Mädler’s map, 476; of De La Rue’s photograph, 477

Mounting of Large Telescopes (Chap. XX.), 293-327

Mounting of specula for reflecting telescopes, 144, 149, 169

Mudge, grinding and polishing specula, 129; gravity escapement, 200

Mural circle, 241, 242

Mural quadrant, Tycho Brahe’s, 233, 235

Multiple stars, 351

N.

Nebulæ, 351

Nebula of Orion, 157, 158

Neptune, as a telescopic object, 351

Newall’s equatorial refractor, 302; with spectroscope, 427; flint-glass discs for, 119; production of discs for object-glass, 128; photographs of the moon, 459

Newcastle, time signals, 278

Newton (Sir Isaac), on refracting telescopes, 82; his reflecting telescope, 101, 102; use of pitch in polishing specula, 128; refrangibility of light, 387; polarized light, 442

Newtonian reflector, 149; view of optical part, 143; effective light, 169; Grubb’s form, 303; Browning’s form, 304; mounting of, 310

Nicols’ prism, 115; measurement of the light of stars, 380; polarization of light, 443, 447, 448, 449, 450

North pole, diagram illustrating how it is found, 249, 251

498O.

Object-glasses, production of, 118, 119; correction of colour, 88; correction for spherical aberration, 126; mode of polishing, 128; mode of centring, 140; illustrations of defective adjustment, 141; adjustment of, 163; its perfection in modern telescopes, 166, 305; cost of production, 172; divided, for duplication of image, 225

Object-glass prism, 426

Observatories [see Alexandrian Museum, Cambridge (U.S.), Cincinnati, Edinburgh, Greenwich, Huen (Tycho Brahe’s), Kew, Lord Lindsay’s, Mauritius, Melbourne, Meudon, Paris, Potsdam, Vienna, Washington]

Observing chair for equatorial telescopes, 339

Optical action of the eye, 67; long and short sight, 69, 71

Optical qualities of telescopes, permanence of, 170

Optic axis in crystals of Iceland spar, 228

“Optick tube,” telescope so first called, 55, 139-151

Orion, first observations of, 5; Orion and the neighbouring constellations, 156; nebula of, 157, 158; stars in, a test for power of telescopes, 164-166; facilities for observing, 164

P.

Parallactic rules, 51; used by Ptolemy, 35; by Tycho Brahe, 38, 41

Parallax of the moon, observed by Ptolemy, 35

Paris Observatory, reflecting equatorial telescope, 314, 315, 337; siderostat, 344; photoheliograph, 469

Pendulum, 183, 185, 187, 188

Personal equation, 259

Phosphatic glass for lenses, 123

Photography, Celestial (Chap. XXXI., XXXII.), 454-483

Photography, stellar, 172

Photoheliograph, for photographs of the sun, 460, 470; for transit of Venus (1874), 461

Photometry, 373, 377

PHYSICS, ASTRONOMICAL (Book VI.), 371

499Physical Inquiry, General Field of (Chap. XXV.), 371-376

Picard, transit circle, 284

Pisces, its position in the zodiac, 34

Pitch employed in polishing lenses and specula, 128, 132

Plane of the ecliptic, 13, 14

Planets, in Ptolemy’s system, 3; first observations of conjunction, 4, 5; motions observed by Autolycus, 9; in Tycho Brahe’s system, 46; Saturn seen with object-glasses of 3¾ and 26 inches, 160, 161; as telescopic objects, 350; photographs of, 465

Pleiades, the first observations of, 5

Plücker, spectrum analysis, 413

Pogson, star magnitudes, 381, 382

Pointers of pre-telescopic instruments, 35, 49, 214, 216

Polar axis of the equatorial, 299, 302, 308, 311, 312, 324, 328, 329, 346

Polariscope, 441-453

Polarization of light, 441-453

Pole, North, 238; diagram illustrating how it is found, 249

Pole star, first observations of, 6; observations of Euclid, 10, 14; its position, 238

Polishing lenses and specula, 128, 171; Lord Rosse’s polishing machine, 131; Mr. Lassell’s, 132

Posidonius, measurement of the earth’s circumference, 8

Position circle, 353

Position micrometer, 353, 358

Post Office Telegraphs, for distribution of Greenwich time, 275

Potsdam, photoheliograph at, 469

Precession of the equinoxes, 33

Prime-vertical, 285

Prime-vertical instrument, 287

Primum mobile of Ptolemy, 3

Prisms, action of, 55; crown and flint-glass, 83, 84; water, 85; doubly refracting, for the micrometer, 226; direct vision, 400; in the spectroscope, 393-400; object-glass prism, 426

Ptolemy, the Heavens according to, 3; trigonometrical tables, 17; sun’s altitude, 21; his discoveries, 35; parallax of the moon, 35; his measurement of time, 36; parallactic rules, 38, 51

Purbach, observation of altitudes by, 36

Pyramids, the first constructed astronomical instruments, 5, 6

500Q.

Quadrants used by Tycho Brahe, 38; his quadrans maximus, 48

Quadrant, mural, 233, 235

Quartz crystals for polarizing light, 450, 452

R.

Radiation of stars, visual, 383; thermal, 385

Radiation, general and selective, 403, 408

Ramsden’s eyepiece, 112, 212

Reading microscopes, for Greenwich and Cambridge (U.S.) transit circles, 247; for Newall’s telescope, 307

Red stars (see Colour of Stars)

Reflection of light (see Light)

Reflecting telescopes (see Telescope)

Reflective powers, Sir John Herschel’s table of, 168

Reflector, diagonal, for solar observations, 114

Reflecting and refracting telescopes compared, 170

Reflex zenith-tube at Greenwich, 286

Refracting telescopes (see Telescopes)

Refracting and reflecting telescopes compared, 170

Refraction of light (see Light)

Refraction, double, by crystals of Iceland spar (see Iceland Spar)

Refrangibility of colours, 387; of light, 420

Regiomontanus, altitudes measured by, 36

Regulation of clocks by electricity, 272

Rising of stars (see Stars)

Right ascension, 24, 234, 241, 249, 257; measured by Hipparchus, 44; by Tycho Brahe, 45

Ring micrometer, 368

Robinson (Dr.), specula of Melbourne telescope, 129; apertures of object-glasses, 168

Rockets fired as time signals, 281

Römer, wires in a transit eyepiece, 220; transit circle and transit instrument, 284

Rosse (Lord), his reflecting telescope, 108, 294, 311, 312; composition of reflector, 120; production of metallic specula, 121, 131; nebula of Orion as seen by his reflector, 157, 158; illuminating power of his telescope, 159; 501effective light, 169; thermopile observations, 384

Royal Observatory, Greenwich (see Greenwich)

Rudolph II. (Emperor), his patronage of Tycho Brahe, 42

Rumford’s photometer, 377

Rutherfurd, his work in celestial photography, 455, 464, 466, 471, 477, 480

S.

Salts, flame of, in a Bunsen’s burner, 407

Sand clocks and sand glasses, 176

Saturn, in Ptolemy’s system, 3; in Tycho Brahe’s, 46; as seen with a 3¾ inch and 26 inch object-glass, 160, 161; as a telescopic object, 351; mode of measuring its rings, 357; photographs of, 465, 466

Savart’s analyser for polarization of light, 452

Scarphie, employed by Eratosthenes, 19

Scheiner’s telescope, 78

Seasons, The, 15, 16

Secchi (Father), direct-vision star spectroscope, 431; stellar spectra, 433

Setting of stars (see Stars)

Sextants used by Tycho Brahe, 38, 50

Sidereal clock, 254, 266 (see Clock)

Sidereal day, 256

Sidereal time, 240, 254, 324

Siderostat, The (Chap. XXIII.), 343-348, 461; at Lord Lindsay’s Observatory, 347

Signals for distributing “Greenwich time,” 278

Signals, time, 281, 283

Signs of the zodiac (see Zodiac)

Silver-on-glass reflector at the Paris Observatory, 316

Silvering glass specula, modes of, 137; silvered glass reflectors, 171

Simms, his introduction of the collimator in the spectroscope, 393, 425

Sirius, first observations of, 5; spectrum of, 432

Slough, Sir Wm. Herschel’s telescope at, 294

Smyth (Admiral), stars in Orion, 165; colours of stars, 351; star magnitudes, 381

Smyth (Prof. Piazzi), on the pyramids as astronomical instruments, 6; position of the vernal equinox, 34; 502clock arrangements at Edinburgh Observatory, 269

Sodium, discovery of its presence in the sun, 412

Solar photography, 459, 465

Solar spectroscope, 435; Browning’s and Grubb’s forms, 428

Solar spectrum, 390, 391, 392, 423, 433, 436, 438, 439; photographs of, 479, 480

Solar time, 253, 255

Solstices, first observations of the, 15, 16, 17, 22

Southing of stars, 234

SPACE MEASURERS (Book III.), 135-232; circle reading, 211; Digges’ diagonal scale, 213; the vernier, 214; micrometers, 218

Space-penetrating power of the telescope, 154; stars in Orion, a test of, 165

Spectroscope, construction of the, 393-400; automatic, 397; arranged for showing absorption, 409; attached to Newall’s refractor, 427; solar, Browning’s and Grubb’s forms, 428

Spectrum produced by prisms, irrationality of the, 86, 87

Spectrum, solar, 390, 391, 392

Spectrum analysis, principles of, 401-421

Specula, production of, 117, 120; casting, annealing, 121; curvature, 122; grinding, 127; polishing, 128; silvering, 137; mounting, 142, 169, 172; effective light, 169; repolishing, 171; cost as compared with object-glasses, 172

Spherical aberration, 87; diagram illustrating, 104, 105; its correction in eyepieces, 109, 111; of specula, 123, 124

Sprengel pump, 413

Spring governor of driving-clock for large telescopes, 319, 320

“Spurious disc” of fixed stars, 163

Standard clock at Edinburgh Observatory, 272

Standard sidereal clock of Greenwich Observatory, 267

Standard solar time clock of Greenwich Observatory, 267

Stars, Chemistry of the (Chap. XXVII.-XXX.), 386-453

Stars, Light and Heat of (Chap. XXVI.), 377; variable, 377-385

Stars, first observations of the, 4, 5, 6, 7; first maps of, 8; observations of Autolycus, Euclid, and Posidonius, 8, 10; 503first catalogues of, 19; latitude and longitude of, 24, 30; positions tabulated by Hipparchus, 30; Tycho Brahe’s catalogue and map of, 42, 44; stars in Gemini seen through a large telescope, 155; nebula of Orion, 157; Orion and its neighbourhood, 156; double, as defined by telescopes of different power, 162, 164, 167, 167; distance of stars from the earth, 159; facilities for observing Orion, its stars, a test for power of telescopes, 164; stellar photography, 172, 465, 466, 467, 478; their rising and setting as measurers of time, 176; double, measurement of, 359, 361, 362; spectrum of red star, 433

Star-clusters, double and multiple stars, 351

Star-spectra, from Father Secchi’s observations, 433; photographs of, 479

Star spectroscopes, at Cambridge (U.S.), 430; direct vision, 431

Star-time (see Sidereal Time)

Steinheil, improvement of specula, 117

Stellar day, 256

Stereographs of the moon, 465, 466

Sternberg, Tycho Brahe’s Observatory, 38

Stewart (Prof. Balfour), spectrum analysis, 402; solar photography, 471

Stokes (Prof.), experiments with phosphatic glass, 123; spectrum analysis, 402, 410

Stone, thermopile at Greenwich, 384

Strontium in the sun, 419

Struve, transit instrument, 285; double stars, 362; star magnitudes, 381

Sun, The; in Ptolemy’s system, 3; first determination of its yearly course, 8, 15; course in the zodiac, described by Autolycus, 9; altitude determined by the gnomon, 16, 18; and the Scarphie, 19, 20; telescopes for observing, 114; “mean sun,” 256; as a telescopic object, 349; presence of sodium in, 412, 415; vapour of other metals, 417; absorption spectrum, 418; telespectroscopic observations, 436; of the chromosphere, 437; sun-storms, 438, 439; photographs, 459, 469, 470

504Sun-dials, 18

Sun-spots observed by Galileo and Scheiner, 78; examined by the position micrometer, 358; spectra of, 415, 435

Sunderland time signals, 278

T.

Talcott, zenith telescope designed by, 285

Taurus, its position in the zodiac, 34

Telegraph wires, their application in determining “local time,” 281

Telepolariscope, The (Chap. XXX.), 441-453

Telespectroscope, 426

TELESCOPE, THE (Book II.), 55-172

TELESCOPE, THE EQUATORIAL (Book V.), 293-368

Telescope:—Various Methods of Mounting Large Telescopes (Chap. XX.), 293-327; refracting, 73-89; Galilean, 73; magnifying power of the telescope, 76, 79; Scheiner’s telescope, 78; focal length of early telescopes, 79; achromatic, 86; reflecting, 100-108; Gregory’s telescope, 101; Newton’s, 102; Cassegrain’s, 103; Sir W. Herschel’s 103, 108; Lord Rosse’s, De La Rue’s, Lassell’s, Foucault’s, Grubb’s, 108; eyepieces, 109-116; Huyghen’s eyepiece, 110; Ramsden’s eyepiece, 112; magnifying power of eyepieces, 116; lenses and specula, 117-138; flint glass for lenses, 119; the “optick tube,” 139-151; the modern telescope, 152-172; magnifying and space penetrating power, 154, 155; illuminating power, 158; defining power, 160; reflecting and refracting compared, 170; permanence of optical qualities, 170; “telescopic sight,” 219; Sir Wm. Herschel’s at Slough, 294; Lord Rosse’s reflector, 294, 311, 312; refractor on alt-azimuth tripod, 296; simple equatorial mounting, 298; the German mounting, 299; Washington great equatorial, 309; English mounting, 310; forked mounting, 310; Greenwich equatorial, 310; Melbourne reflector, 312, 313; Paris reflector, 314; driving clock, 318; Newall’s refractor with spectroscope, 427; 505De La Rue’s, 459; Rutherfurd’s, 466; Newall’s, 459; Melbourne, 459

Telescope, zenith (see Zenith Telescope)

Temperature, its effect on the pendulum, 187, 193

Terrestrial globe, 23

Thales, his employment of the gnomon, 17

Theodolite, 288

Theodolite, astronomical, 287

Thermometry, 374, 384

Thermopile, 374

Time; first reckoning of, 19; early measurements, 36, 44, 175; modern measurement of, 253; sidereal, solar, and mean, 254, 256

TIME AND SPACE MEASURERS (Book III.), 175-232

Time, Greenwich (see Greenwich Time)

Time, local, 281

Time balls for distributing Greenwich time, 275

Time signals, 278, 281, 283

Timocharis, his observations in the Alexandrian museum, 19

Tourmaline, in polarization of light, 443

Transit Circle, The (Chap. XVI.), 233-252; system of wires in eyepiece, 220; at Greenwich and Cambridge (U.S.), 247, 248, 251; mode of using, 253, 284

Transit Clock, The (Chap. XVII.), 253-270

Transit instrument, 171, 234, 236, 237; mode of using, 253; Römer’s, 284; Struve’s, 285

Transit of Venus, photographic observations, 475

Trigonometrical tables, first construction of, 17

Tropics, defined by Euclid, 12

Trouvelot, ring of Saturn observed with the Washington refractor, 161

Tube of the telescope, 139-151

Tycho Brahe; astrolabe, 26; ecliptic astrolabe, 28; discoveries of, 37-52; biography of, 37; list of his instruments, 38; portrait, 39; catalogue of stars, 42; observatory (engraving), 43, 287; his solar system, 46; discovery of comet of 1677, 47; instruments for measuring distances and altitudes of stars, 51; clocks, 179, 184, 196; diagonal scale for measuring space, 213; mural quadrant, 233; transit circle, 284

506U.

United States Naval Observatory, 341

Uranus, as a telescopic object, 351

Uraniberg, Tycho Brahe’s Observatory, 38

V.

Variable stars, 377

Velocity of gases in sun-storms, 440

Venice, ancient clock dials, 257

Venus, in Ptolemy’s system, 3; in Tycho Brahe’s, 46; employed by Tycho Brahe in determining longitude, 44; as a telescopic object, 350; transit of, instrument used in the expedition of 1874, 236; photographic observations, 475

Vibrations, ethereal, 373, 401, 410, 449, 450

Vienna, refracting telescope, 141

Villarceau, Yvon, driving clocks, 324

Vega, heat of, 385

Vernal equinox, its position in the constellations, 34

Vernier, the, 214

Vertical circle, Ertel’s, 290

W.

Walther, altitudes measured by, 36

Washington Observatory; great refracting telescope, 302, 309; flint glass discs, 119; ring of Saturn seen through it, 161

Watches, detached lever escapement for, 207

Water clocks, 176

Wave-lengths of light of solar gases, 440

Westminster clock-tower, 277

Wheatstone (Sir C.); “chronographic method” of transit observation, 259; apparatus for controlling clocks, 271

Winlock (Prof.), photographs of the sun, 461

Wires, cross, for circle reading, 212, 216; system of wires in a transit eyepiece, 220, 234, 257; in eyepiece of Greenwich transit circle, 246; wires of the transit instrument, 234

Wire micrometer, 221, 352

507Wolfius, correction of chromatic aberration in lenses, 89

Wollaston (Dr.), lines in the solar spectrum, 391; spectrum analysis, 402, 422

Wyck (Henry de), clock made in 1364 by, 178

Y.

Ys of the transit instrument, 238, 284

Years, first observation of, 5; determination of their length, 22

508Z.

Zenith, zenith sector, zenith telescope, reflex zenith tube, at Greenwich, 285

Zenith distances, measurement of, 51

Zodiac, first defined, 8, 9; observations of Euclid, 11, 12; of Denderah, 7

Zöllner’s astrophotometer, 379

Zero of right ascension, 249

Zinc in the sun, 419

THE END.

LONDON: R. CLAY, SONS, AND TAYLOR, BREAD STREET HILL, E.C.