A Short History of Astronomy

by Arthur Berry

CONTENTS.

PAGE
Preface		v
[CHAPTER I.]
Primitive Astronomy, §§ 1-18		1-20
[§ 1].	Scope of astronomy	[1]
[§§ 2-5].	First notions: the motion of the sun: the motion and phases of the moon: daily motion of the stars	[1]
[§ 6].	Progress due to early civilised peoples: Egyptians, Chinese, Indians, and Chaldaeans	3
[§ 7].	The celestial sphere: its scientific value: apparent distance between the stars: the measurement of angles	4
[§§ 8-9].	The rotation of the celestial sphere: the North and South poles: the daily motion: the celestial equator: circumpolar stars	7
[§§ 10-11].	The annual motion of the sun: great circles: the ecliptic and its obliquity: the equinoxes and equinoctial points: the solstices and solstitial points	8
§§ 12-13.	The constellations: the zodiac, signs of the zodiac, and zodiacal constellations: the first point of Aries (♈), and the first point of Libra (♎)	12
[§ 14].	The five planets: direct and retrograde motions: stationary points	14
[§ 15].	The order of nearness of the planets: occultations: superior and inferior planets	15
[§ 16].	Measurement of time: the day and its division into hours: the lunar month: the year: the week	17
[§ 17].	Eclipses: the saros	19
[§ 18].	The rise of Astrology	20
[CHAPTER II.]
Greek Astronomy (from about 600 b.c. to about 400 a.d.), [§§ 19-54]		21-75
[§§ 19-20].	Astronomy up to the time of Aristotle. The Greek calendar: full and empty months: the octaeteris: Meton’s cycle	21
[§ 21].	The Roman calendar: introduction of the Julian Calendar	22
[§ 22].	The Gregorian Calendar	23
[§ 23].	Early Greek speculative astronomy: Thales and Pythagoras: the spherical form of the earth: the celestial spheres: the music of the spheres	24
[§ 24].	Philolaus and other Pythagoreans: early believers in the motion of the earth: Aristarchus and Seleucus	25
[§ 25].	Plato: uniform circular and spherical motions	26
[§ 26].	Eudoxus: representation of the celestial motions by combinations of spheres: description of the constellations. Callippus	27
[§§ 27-30].	Aristotle: his spheres: the phases of the moon: proofs that the earth is spherical: his arguments against the motion of the earth: relative distances of the celestial bodies: other speculations: estimate of his astronomical work	29
[§§ 31-2].	The early Alexandrine school: its rise: Aristarchus: his estimates of the distances of the sun and moon. Observations by Timocharis and Aristyllus	34
[§§ 33-4].	Development of spherics: the Phenomena of Euclid: the horizon, the zenith, poles of a great circle, verticals, declination circles, the meridian, celestial latitude and longitude, right ascension and declination. Sun-dials	36
[§ 35].	The division of the surface of the earth into zones	37
[§ 36].	Eratosthenes: his measurement of the earth: and of the obliquity of the ecliptic	39
[§ 37].	Hipparchus: his life and chief contributions to astronomy. Apollonius’s representation of the celestial motions by means of circles. General account of the theory of eccentrics and epicycles	40
[§§ 38-9].	Hipparchus’s representation of the motion of the sun, by means of an eccentric: apogee, perigee, line of apses, eccentricity: equation of the centre: the epicycle and the deferent	41
[§ 40].	Theory of the moon: lunation or synodic month and sidereal month: motion of the moon’s nodes and apses: draconitic month and anomalistic month	47
[§ 41].	Observations of planets: eclipse method of connecting the distances of the sun and moon: estimate of their distances	49
[§ 42].	His star catalogue. Discovery of the precession of the equinoxes: the tropical year and the sidereal year	51
[§ 43].	Eclipses of the sun and moon: conjunction and opposition: partial, total, and annular eclipses: parallax	56
[§ 44].	Delambre’s estimate of Hipparchus	61
[§ 45].	The slow progress of astronomy after the time of Hipparchus: Pliny’s proof that the earth is round: new measurements of the earth by Posidonius	61
[§ 46].	Ptolemy. The Almagest and the Optics: theory of refraction	62
[§ 47].	Account of the Almagest: Ptolemy’s postulates: arguments against the motion of the earth	63
[§ 48].	The theory of the moon: evection and prosneusis	65
[§ 49].	The astrolabe. Parallax, and distances of the sun and moon	67
[§ 50].	The star catalogue: precession	68
[§ 51].	Theory of the planets: the equant	69
[§ 52].	Estimate of Ptolemy	73
[§ 53].	The decay of ancient astronomy: Theon and Hypatia	73
[§ 54].	Summary and estimate of Greek astronomy	74
[CHAPTER III.]
The Middle Ages (from about 600 a.d. to about 1500 a.d.), [§§ 55-69]		76-91
[§ 55].	The slow development of astronomy during this period	76
[§ 56].	The East. The formation of an astronomical school at the court of the Caliphs: revival of astrology: translations from the Greek by Honein ben Ishak, Ishak ben Honein, Tabit ben Korra, and others	76
[§§ 57-8].	The Bagdad observatory. Measurement of the earth. Corrections of the astronomical data of the Greeks: trepidation	78
[§ 59].	Albategnius: discovery of the motion of the sun’s apogee	79
[§ 60].	Abul Wafa: supposed discovery of the variation of the moon. Ibn Yunos: the Hakemite Tables	79
[§ 61].	Development of astronomy in the Mahometan dominions in Morocco and Spain: Arzachel: the Toletan Tables	80
[§ 62].	Nassir Eddin and his school: Ilkhanic Tables: more accurate value of precession	81
[§ 63].	Tartar astronomy: Ulugh Begh: his star catalogue	82
[§ 64].	Estimate of oriental astronomy of this period: Arabic numerals: survivals of Arabic names of stars and astronomical terms: nadir	82
[§ 65].	The West. General stagnation after the fall of the Roman Empire: Bede. Revival of learning at the court of Charlemagne: Alcuin	83
[§ 66].	Influence of Mahometan learning: Gerbert: translations from the Arabic: Plato of Tivoli, Athelard of Bath, Gherardo of Cremona. Alfonso X. and his school: the Alfonsine Tables and the Libros del Saber	84
[§ 67].	The schoolmen of the thirteenth century, Albertus Magnus, Cecco d’Ascoli, Roger Bacon. Sacrobosco’s Sphaera Mundi	85
[§ 68].	Purbach and Regiomontanus: influence of the original Greek authors: the Nürnberg school: Walther: employment of printing: conflict between the views of Aristotle and of Ptolemy: the celestial spheres of the Middle Ages: the firmament and the primum mobile	86
[§ 69].	Lionardo da Vinci: earthshine. Fracastor and Apian: observations of comets. Nonius.Fernel’s measurement of the earth	90
[CHAPTER IV.]
Coppernicus (from 1473 a.d. to 1543 a.d.), [§§ 70-92]		92-124
[§ 70].	The Revival of Learning	92
[§§ 71-4].	Life of Coppernicus: growth of his ideas: publication of the Commentariolus: Rheticus and the Prima Narratio: publication of the De Revolutionibus	93
[§ 75].	The central idea in the work of Coppernicus: relation to earlier writers	99
[§§ 76-9].	The De Revolutionibus. The first book: the postulates: the principle of relative motion, with applications to the apparent annual motion of the sun, and to the daily motion of the celestial sphere	100
[§ 80].	The two motions of the earth: answers to objections	105
[§ 81].	The motion of the planets	106
[§ 82].	The seasons	108
[§ 83].	End of first book. The second book: decrease in the obliquity of the ecliptic: the star catalogue	110
[§ 84].	The third book: precession	110
[§ 85].	The third book: the annual motion of the earth: aphelion and perihelion. The fourth book: theory of the moon: distances of the sun and moon: eclipses	111
[§§ 86-7].	The fifth and sixth books: theory of the planets: synodic and sidereal periods	112
[§ 88].	Explanation of the stationary points	118
[§§ 89-90].	Detailed theory of the planets: defects of the theory	121
[§ 91].	Coppernicus’s use of epicycles	122
[§ 92].	A difficulty in his system	123
[CHAPTER V.]
The Reception of the Coppernican Theory and the Progress of Observation (from about 1543 a.d. to about 1601 a.d.), [§§ 93-112]		125-144
[§§ 93-4].	The first reception of the De Revolutionibus: Reinhold: the Prussian Tables	125
[§ 95].	Coppernicanism in England: Field, Recorde, Digges	127
[§ 96].	Difficulties in the Coppernican system: the need for progress in dynamics and for fresh observations	127
[§§ 97-8].	The Cassel Observatory: the Landgrave William IV., Rothmann, and Bürgi: the star catalogue: Bürgi’s invention of the pendulum clock	128
[§ 99].	Tycho Brahe: his early life	130
[§ 100].	The new star of 1572: travels in Germany	131
[§§ 101-2].	His establishment in Hveen: Uraniborg and Stjerneborg: life and work in Hveen	132
[§ 103].	The comet of 1577, and others	135
[§ 104].	Books on the new star and on the comet of 1577	136
[§ 105].	Tycho’s system of the world: quarrel with Reymers Bär	136
[§ 106].	Last years at Hveen: breach with the King	138
[§ 107].	Publication of the Astronomiae Instauratae Mechanica and of the star catalogue: invitation from the Emperor	139
[§ 108].	Life at Benatek: co-operation of Kepler: death	140
[§ 109].	Fate of Tycho’s instruments and observations	141
[§ 110].	Estimate of Tycho’s work: the accuracy of his observations: improvements in the art of observing	141
[§ 111].	Improved values of astronomical constants. Theory of the moon: the variation and the annual equation	143
[§ 112].	The star catalogue: rejection of trepidation: unfinished work on the planets	144
[CHAPTER VI.]
Galilei (from 1564 a.d. to 1642 a.d.), [§§ 113-134]		145-178
[§ 113].	Early life	145
[§ 114].	The pendulum	146
[§ 115].	Diversion from medicine to mathematics: his first book	146
[§ 116].	Professorship at Pisa: experiments on falling bodies: protests against the principle of authority	147
[§ 117].	Professorship at Padua: adoption of Coppernican views	148
[§ 118].	The telescopic discoveries. Invention of the telescope by Lippersheim: its application to astronomy by Harriot, Simon Marius, and Galilei	149
[§ 119].	The Sidereus Nuncius: observations of the moon	150
[§ 120].	New stars: resolution of portions of the Milky Way	151
[§ 121].	The discovery of Jupiter’s satellites: their importance for the Coppernican controversy: controversies	151
[§ 122].	Appointment at the Tuscan court	153
[§ 123].	Observations of Saturn. Discovery of the phases of Venus	154
[§ 124].	Observations of sun-spots by Fabricius, Harriot, Scheiner, and Galilei: the Macchie Solari: proof that the spots were not planets: observations of the umbra and penumbra	154
[§ 125].	Quarrel with Scheiner and the Jesuits: theological controversies: Letter to the Grand Duchess Christine	157
[§ 126].	Visit to Rome. The first condemnation: prohibition of Coppernican books	159
[§ 127].	Method for finding longitude. Controversy on comets: Il Saggiatore	160
[§ 128].	Dialogue on the Two Chief Systems of the World. Its preparation and publication	162
[§ 129].	The speakers: argument for the Coppernican system based on the telescopic discoveries: discussion of stellar parallax: the differential method of parallax	163
[§ 130].	Dynamical arguments in favour of the motion of the earth: the First Law of Motion. The tides	165
[§ 131].	The trial and condemnation. The thinly veiled Coppernicanism of the Dialogue: the remarkable preface	168
[§ 132].	Summons to Rome: trial by the Inquisition: condemnation, abjuration, and punishment: prohibition of the Dialogue	169
[§ 133].	Last years: life at Arcetri: libration of the moon: the Two New Sciences: uniform acceleration, and the first law of motion. Blindness and death	172
[§ 134].	Estimate of Galilei’s work: his scientific method	176
[CHAPTER VII.]
Kepler (from 1571 a.d. to 1630 a.d.), [§§ 135-151]		179-197
[§ 135].	Early life and theological studies	179
[§ 136].	Lectureship on mathematics at Gratz: astronomical studies and speculations: the Mysterium Cosmographicum	180
[§ 137].	Religious troubles in Styria: work with Tycho	181
[§ 138].	Appointment by the Emperor Rudolph as successor to Tycho: writings on the new star of 1604 and on Optics: theory of refraction and a new form of telescope	182
[§ 139].	Study of the motion of Mars: unsuccessful attempts to explain it	183
[§§ 140-1].	The ellipse: discovery of the first two of Kepler’s Laws for the case of Mars: the Commentaries on Mars	184
[§ 142].	Suggested extension of Kepler’s Laws to the other planets	186
[§ 143].	Abdication and death of Rudolph: appointment at Linz	188
[§ 144].	The Harmony of the World: discovery of Kepler’s Third Law: the “music of the spheres”	188
[§ 145].	Epitome of the Copernican Astronomy: its prohibition: fanciful correction of the distance of the sun: observation of the sun’s corona	191
[§ 146].	Treatise on Comets	193
[§ 147].	Religious troubles at Linz: removal to Ulm	194
[§ 148].	The Rudolphine Tables	194
[§ 149].	Work Under Wallenstein: death	195
[§ 150].	Minor discoveries: speculations on gravity	195
[§ 151].	Estimate of Kepler’s work and intellectual character	197
[CHAPTER VIII.]
From Galilei to Newton (from about 1638 a.d. to about 1687 a.d.), [§§ 152-163]		198-209
[§ 152].	The general character of astronomical progress during the period	198
[§ 153].	Scheiner’s observations of faculae on the sun. Hevel: his Selenographia and his writings on comets: his star catalogue. Riccioli’s New Almagest	198
[§ 154].	Planetary observations; Huygens’s discovery of a satellite of Saturn and of its ring	199
[§ 155].	Gascoigne’s and Auzout’s invention of the micrometer: Picard’s telescopic “sights”	202
[§ 156].	Horrocks: extension of Kepler’s theory to the moon: observation of a transit of Venus	202
[§§ 157-8].	Huygens’s rediscovery of the pendulum clock: his theory of circular motion	203
[§ 159].	Measurements of the earth by Snell, Norwood, and Picard	204
[§ 160].	The Paris Observatory: Domenico Cassini: his discoveries of four new satellites of Saturn: his other work	204
[§ 161].	Richer’s expedition to Cayenne: pendulum observations: observations of Mars in opposition: horizontal parallax: annual or stellar parallax	205
[§ 162].	Roemer and the velocity of light	208
[§ 163].	Descartes	208
[CHAPTER IX.]
Universal Gravitation (from 1643 a.d. to 1727 a.d.), [§§ 164-195]		210-246
[§ 164].	Division of Newton’s life into three periods	210
[§ 165].	Early life, 1643 to 1665	210
[§ 166].	Great productive period, 1665-87	211
[§ 167].	Chief divisions of his work: astronomy, optics, pure mathematics	211
[§ 168].	Optical discoveries: the reflecting telescopes of Gregory and Newton: the spectrum	211
[§ 169].	Newton’s description of his discoveries in 1665-6	212
[§ 170].	The beginning of his work on gravitation: the falling apple: previous contributions to the subject by Kepler, Borelli, and Huygens	213
[§ 171].	The problem of circular motion: acceleration	214
[§ 172].	The law of the inverse square obtained from Kepler’s Third Law for the planetary orbits, treated as circles	215
[§ 173].	Extension of the earth’s gravity as far as the moon: imperfection of the theory	217
[§ 174].	Hooke’s and Wren’s speculations on the planetary motions and on gravity. Newton’s second calculation of the motion of the moon: agreement with observation	221
§ 175-6.	Solution of the problem of elliptic motion: Halley’s visit to Newton	221
[§ 177].	Presentation to the Royal Society of the tract De Motu: publication of the Principia	222
[§ 178].	The Principia: its divisions	223
[§§ 179-80].	The Laws of Motion: the First Law: acceleration in its general form: mass and force: the Third Law	223
[§ 181].	Law of universal gravitation enunciated	227
[§ 182].	The attraction of a sphere	228
[§ 183].	The general problem of accounting for the motions of the solar system by means of gravitation and the Laws of Motion: perturbations	229
[§ 184].	Newton’s lunar theory	230
[§ 185].	Measurement of the mass of a planet by means of its attraction of its satellites	231
[§ 186].	Motion of the sun: centre of gravity of the solar system: relativity of motion	231
[§ 187].	The non-spherical form of the earth, and of Jupiter	233
[§ 188].	Explanation of precession	234
[§ 189].	The tides: the mass of the moon deduced from tidal observations	235
[§ 190].	The motions of comets: parabolic orbits	237
[§ 191].	Reception of the Principia 239
[§ 192].	Third period of Newton’s life, 1687-1727: Parliamentary career: improvement of the lunar theory: appointments at the Mint and removal to London: publication of the Optics and of the second and third editions of the Principia, edited by Cotes and Pemberton: death	240
[§ 193].	Estimates of Newton’s work by Leibniz, by Lagrange, and by himself	241
[§ 194].	Comparison of his astronomical work with that of his predecessors: “explanation” and “description”: conception of the material universe as made up of bodies attracting one another according to certain laws	242
[§ 195].	Newton’s scientific method: “Hypotheses non fingo”	245
[CHAPTER X.]
Observational Astronomy in the Eighteenth Century, [§§ 196-227]		247-286
[§ 196].	Gravitational astronomy: its development due almost entirely to Continental astronomers: use of analysis: English observational astronomy	247
[§§ 197-8].	Flamsteed: foundation of the Greenwich Observatory: his star catalogue	249
[§ 199].	Halley: catalogue of Southern stars	253
[§ 200].	Halley’s comet	253
[§ 201].	Secular acceleration of the moon’s mean motion	254
[§ 202].	Transits of Venus	254
[§ 203].	Proper motions of the fixed stars	255
[§§ 204-5].	Lunar and planetary tables: career at Greenwich: minor work	255
[§ 206].	Bradley: career	257
[§§ 207-11].	Discovery and explanation of aberration: the constant of aberration	258
[§ 212].	Failure to detect parallax	265
[§§ 213-5].	Discovery of nutation: Machin	265
[§§ 216-7].	Tables of Jupiter’s satellites by Bradley and by Wargentin: determination of longitudes, and other work	269
[§ 218].	His observations: reduction	271
[§ 219].	The density of the earth: Maskelyne: the Cavendish experiment	273
[§ 220].	The Cassini-Maraldi school in France	275
[§ 221].	Measurements of the earth: the Lapland and Peruvian arcs: Maupertuis	275
[§§ 222-4].	Lacaille: his career: expedition to the Cape: star catalogues, and other work	279
[§§ 225-6].	Tobias Mayer: his observations: lunar tables: the longitude prize	282
[§ 227].	The transits of Venus in 1761 and 1769: distance of the sun	284
[CHAPTER XI.]
Gravitational Astronomy in the Eighteenth Century, [§§ 228-250]		287-322
[§ 228].	Newton’s problem: the problem of three bodies: methods of approximation: lunar theory and planetary theory	287
[§ 229].	The progress of Newtonian principles in France: popularisation by Voltaire. The five great mathematical astronomers: the pre-eminence of France	290
[§ 230].	Euler: his career: St. Petersburg and Berlin: extent of his writings	291
[§ 231].	Clairaut: figure of the earth: return of Halley’s comet	293
[§ 232].	D’Alembert: his dynamics: precession and nutation: his versatility: rivalry with Clairaut	295
[§§ 233-4].	The lunar theories and lunar tables of Euler, Clairaut, and D’Alembert: advance on Newton’s lunar theory	297
[§ 235].	Planetary theory: Clairaut’s determination of the masses of the moon and of Venus: Lalande	299
[§ 236].	Euler’s planetary theory: method of the variation of elements or parameters	301
[§ 237].	Lagrange: his career: Berlin and Paris: the Mécanique Analytique	304
[§ 238].	Laplace: his career: the Mécanique Céleste and the Système du Monde: political appointments and distinctions	306
[§ 239].	Advance made by Lagrange and Laplace on the work of their immediate predecessors	308
[§ 240].	Explanation of the moon’s secular acceleration by Laplace	308
[§ 241].	Laplace’s lunar theory: tables of Bürg and Burckhardt	309
[§ 242].	Periodic and secular inequalities	310
[§ 243].	Explanation of the mutual perturbation of Jupiter and Saturn: long inequalities	312
[§§ 244-5].	Theorems on the stability of the solar system: the eccentricity fund and the inclination fund	313
[§ 246].	The magnitudes of some of the secular inequalities	318
[§ 247].	Periodical inequalities: solar and planetary tables Mécanique Céleste	318
[§ 248].	Minor problems of gravitational astronomy: the satellites: Saturn’s ring: precession and nutation: figure of the earth: tides: comets: masses of planets and satellites	318
[§ 249].	The solution of Newton’s problem by the astronomers of the eighteenth century	319
[§ 250].	The nebular hypothesis: its speculative character	320
[CHAPTER XII.]
Herschel (from 1738 a.d. to 1822 a.d.), [§§ 251-271]		323-353
[§§ 251-2].	William Herschel’s early career: Bath: his first telescope	323
[§§ 253-4].	The discovery of the planet Uranus, and its consequences: Herschel’s removal to Slough	325
[§ 255].	Telescope-making: marriage: the forty-foot telescope: discoveries of satellites of Saturn and of Uranus	327
[§ 256].	Life and work at Slough: last years: Caroline Herschel	328
[§ 257].	Herschel’s astronomical programme: the study of the fixed stars	330
[§ 258].	The distribution of the stars in space: star-gauging: the “grindstone” theory of the universe: defects of the fundamental assumption: its partial withdrawal. Employment of brightness as a test of nearness: measurement of brightness: “space-penetrating” power of a telescope	332
[§ 259].	Nebulae and star clusters: Herschel’s great catalogues	336
[§ 260].	Relation of nebulae to star clusters: the “island universe” theory of nebulae: the “shining fluid” theory: distribution of nebulae	337
[§ 261].	Condensation of nebulae into clusters and stars	339
[§ 262].	The irresolvability of the Milky Way	340
[§ 263].	Double stars: their proposed employment for finding parallax: catalogues: probable connection between members of a pair	341
[§ 264].	Discoveries of the revolution of double stars: binary stars: their uselessness for parallax	343
[§ 265].	The motion of the sun in space: the various positions suggested for the apex	344
[§ 266].	Variable stars: Mira and Algol: catalogues of comparative brightness: method of sequences: variability of α Herculis	346
[§ 267].	Herschel’s work on the solar system: new satellites: observations of Saturn, Jupiter, Venus, and Mars	348
[§ 268].	Observations of the sun: Wilson: theory of the structure of the sun	350
[§ 269].	Suggested variability of the sun	351
[§ 270].	Other researches	352
[§ 271].	Comparison of Herschel with his contemporaries: Schroeter	352
[CHAPTER XIII.]
The Nineteenth Century, [§§ 272-320]		354-409
[§ 272].	The three chief divisions of astronomy, observational, gravitational, and descriptive	354
[§ 273].	The great growth of descriptive astronomy in the nineteenth century	355
[§ 274].	Observational Astronomy. Instrumental advances: the introduction of photography	357
[§ 275].	The method of least squares: Legendre and Gauss	357
[§ 276].	Other work by Gauss: the Theoria Motus: rediscovery of the minor planet Ceres	358
[§ 277].	Bessel: his improvement in methods of reduction: his table of refraction: the Fundamenta Nova and Tabulae Regiomontanae	359
[§ 278].	The parallax of 61 Cygni: its distance	360
[§ 279].	Henderson’s parallax of α Centauri and Struve’s of Vega: later parallax determinations	362
[§ 280].	Star catalogues: the photographic chart	362
[§§ 281-4].	The distance of the sun: transits of Venus: observations of Mars and of the minor planets in opposition: diurnal method: gravitational methods, lunar and planetary: methods based on the velocity of light: summary of results	363
[§ 285].	Variation in latitude: rigidity of the earth	367
[§ 286].	Gravitational Astronomy. Lunar theory: Damoiseau, Poisson, Pontécoulant, Lubbock, Hansen, Delaunay, Professor Newcomb, Adams, Dr. Hill	367
[§ 287].	Secular acceleration of the moon’s mean motion: Adams’s correction of Laplace: Delaunay’s explanation by means of tidal friction	369
[§ 288].	Planetary theory: Leverrier, Gyldén, M. Poincaré	370
[§ 289].	The discovery of Neptune by Leverrier and Dr. Galle: Adams’s work	371
[§ 290].	Lunar and planetary tables: outstanding discrepancies between theory and observation	372
[§ 291].	Cometary orbits: return of Halley’s comet in 1835: Encke’s and other periodic comets	372
[§ 292].	Theory of tides: analysis of tidal observations by Lubbock, Whewell, Lord Kelvin, and Professor Darwin: bodily tides in the earth and its rigidity	373
[§ 293].	The stability of the solar system	374
[§ 294].	Descriptive Astronomy. Discovery of the minor planets or asteroids: their number, distribution, and size	376
[§ 295].	Discoveries of satellites of Neptune, Saturn, Uranus, Mars, and Jupiter, and of the crape ring of Saturn	380
[§ 296].	The surface of the moon: rills: the lunar atmosphere	382
[§ 297].	The surfaces of Mars, Jupiter, and Saturn: the canals on Mars: Maxwell’s theory of Saturn’s rings: the rotation of Mercury and of Venus	383
[§ 298].	The surface of the sun: Schwabe’s discovery of the periodicity of sun-spots: connection between sun-spots and terrestrial magnetism: Carrington’s observations of the motion and distribution of spots: Wilson’s theory of spots	385
[§§ 299-300].	Spectrum analysis: Newton, Wollaston, Fraunhofer, Kirchhoff: the chemistry of the sun	386
[§ 301].	Eclipses of the sun: the corona, chromosphere, and prominences: spectroscopic methods of observation	389
[§ 302].	Spectroscopic method of determining motion to or from the observer: Doppler’s principle: application to the sun	391
[§ 303].	The constitution of the sun	392
[§§ 304-5].	Observations of comets: nucleus: theory of the formation of their tails: their spectra: relation between comets and meteors	393
[§§ 306-8].	Sidereal astronomy: career of John Herschel: his catalogues of nebulae and of double stars: the expedition to the Cape: measurement of the sun’s heat by Herschel and by Pouillet	396
[§ 309].	Double stars: observations by Struve and others: orbits of binary stars	398
[§ 310].	Lord Rosse’s telescopes: his observations of nebulae: revival of the “island universe” theory	400
[§ 311].	Application of the spectroscope to nebulae: distinction between nebulae and clusters	401
[§ 312].	Spectroscopic classification of stars by Secchi: chemistry of stars: stars with bright-line spectra	401
[§§ 313-4].	Motion of stars in the line of sight. Discovery of binary stars by the spectroscope: eclipse theory of variable stars	402
[§ 315].	Observations of variable stars	403
[§ 316].	Stellar photometry: Pogson’s light ratio: the Oxford, Harvard, and Potsdam photometries	403
[§ 317].	Structure of the sidereal system: relations of stars and nebulae	405
[§§ 318-20].	Laplace’s nebular hypothesis in the light of later discoveries: the sun’s heat: Helmholtz’s shrinkage theory. Influence of tidal friction on the development of the solar system: Professor Darwin’s theory of the birth of the moon. Summary	406
[List of Authorities and of Books for Students]		411
[Index of Names]		417
[General Index]		425

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