Chapter XIII: The Nineteenth Century (3)

319. An entirely new contribution to the problem has resulted from certain discoveries as to the nature of heat, culminating in the recognition (about 1840-50) of heat as only one form of what physicists now call =energy=, which manifests itself also in the motion of bodies, in the separation of bodies which attract one another, as well as in various electrical, chemical, and other ways. With this discovery was closely connected the general theory known as the =conservation of energy=, according to which energy, though capable of many transformations, can neither be increased nor decreased in quantity. A body which, like the sun, is giving out heat and light is accordingly thereby losing energy, and is like a machine doing work; either then it is receiving energy from some other source to compensate this loss or its store of energy is diminishing. But a body which goes on indefinitely giving out heat and light without having its store of energy replenished is exactly analogous to a machine which goes on working indefinitely without any motive power to drive it; and both are alike impossible.

The results obtained by John Herschel and Pouillet in 1836 (§ 307) called attention to the enormous expenditure of the sun in the form of heat, and astronomers thus had to face the problem of explaining how the sun was able to go on radiating heat and light in this way. Neither in the few thousand years of the past covered by historic records, nor in the enormously great periods of which geologists and biologists take account, is there any evidence of any important permanent alteration in the amount of heat and light received annually by the earth from the sun. Any theory of the sun’s heat must therefore be able to account for the continual expenditure of heat at something like the present rate for an immense period of time. The obvious explanation of the sun as a furnace deriving its heat from combustion is found to be totally inadequate when put to the test of figures, as the sun could in this way be kept going at most for a few thousand years. The explanation now generally accepted was first given by the great German physicist _Hermann von Helmholtz_ (1821-1894) in a popular lecture in 1854. The sun possesses an immense store of energy in the form of the mutual gravitation of its parts; if from any cause it shrinks, a certain amount of gravitational energy is necessarily lost and takes some other form. In the shrinkage of the sun we have therefore a possible source of energy. The precise amount of energy liberated by a definite amount of shrinkage of the sun depends upon the internal distribution of density in the sun, which is uncertain, but making any reasonable assumption as to this we find that the amount of shrinking required to supply the sun’s expenditure of heat would only diminish the diameter by a few hundred feet annually, and would therefore be imperceptible with our present telescopic power for centuries, while no earlier records of the sun’s size are accurate enough to shew it. It is easy to calculate on the same principles the amount of energy liberated by a body like the sun in shrinking from an indefinitely diffused condition to its present state, and from its present state to one of assigned greater density; the result being that we can in this way account for an expenditure of sun-heat at the present rate for a period to be counted in millions of years in either past or future time, while if the rate of expenditure was less in the remote past or becomes less in the future the time is extended to a corresponding extent.

No other cause that has been suggested is competent to account for more than a small fraction of the actual heat-expenditure of the sun; the gravitational theory satisfies all the requirements of astronomy proper, and goes at any rate some way towards meeting the demands of biology and geology.

If then we accept it as provisionally established, we are led to the conclusion that the sun was in the past larger and less condensed than now, and by going sufficiently far back into the past we find it in a condition not unlike the primitive nebula which Laplace presupposed, with the exception that it need not have been hot.

320. A new light has been thrown on the possible development of the earth and moon by Professor G. H. Darwin’s study of the effects of tidal friction (cf. § 287 and §§ 292, 293). Since the tides increase the length of the day and month and gradually repel the moon from the earth, it follows that in the past the moon was nearer to the earth than now, and that tidal action was consequently much greater. Following out this clue. Professor Darwin found, by a series of elaborate calculations published in 1879-81, strong evidence of a past time when the moon was close to the earth, revolving round it in the same time in which the earth rotated on its axis, which was then a little over two hours. The two bodies, in fact, were moving as if they were connected; it is difficult to avoid the probable inference that at an earlier stage the two really were one, and that the moon is in reality a fragment of the earth driven off from it by the too-rapid spinning of the earth, or otherwise.

Professor Darwin has also examined the possibility of explaining in a similar way the formation of the satellites of the other planets and of the planets themselves from the sun, but the circumstances of the moon-earth system turn out to be exceptional, and tidal influence has been less effective in other cases, though it gives a satisfactory explanation of certain peculiarities of the planets and their satellites. More recently (1892) Dr. _See_ has applied a somewhat similar line of reasoning to explain by means of tidal action the development of double stars from an earlier nebulous condition.

Speaking generally, we may say that the outcome of the 19th century study of the problem of the early history of the solar system has been to discredit the details of Laplace’s hypothesis in a variety of ways, but to establish on a firmer basis the general view that the solar system has been formed by some process of condensation out of an earlier very diffused mass bearing a general resemblance to one of the nebulae which the telescope shews us, and that stars other than the sun are not unlikely to have been formed in a somewhat similar way; and, further, the theory of tidal friction supplements this general but vague theory, by giving a rational account of a process which seems to have been the predominant factor in the development of the system formed by our own earth and moon, and to have had at any rate an important influence in a number of other cases.

AUTHORITIES AND BOOKS FOR STUDENTS.

I. GENERAL.

I have made great use throughout of R. Wolf’s _Geschichte der Astronomie_, and of the six volumes of Delambre’s _Histoire de l’Astronomie_ (_Ancienne_, 2 vols.; _du Moyen Age_, 1 vol.; _Moderne_, 2 vols.; _du Dixhuitième Siècle_, 1 vol.). I shall subsequently refer to these books simply as _Wolf_ and _Delambre_ respectively. I have used less often the astronomical sections of Whewell’s _History of the Inductive Sciences_ (referred to as _Whewell_), and I am indebted—chiefly for dates and references—to the histories of mathematics written respectively by Marie, W. W. R. Ball, and Cajori, to Poggendorff’s _Handwörterbuch der Exacten Wissenschaften_, and to articles in various biographical dictionaries, encyclopaedias, and scientific journals. Of general treatises on astronomy Newcomb’s _Popular Astronomy_, Young’s _General Astronomy_, and Proctor’s _Old and New Astronomy_ have been the most useful for my purposes.

It is difficult to make a selection among the very large number of books on astronomy which are adapted to the general reader. For students who wish for an introductory account of astronomy the Astronomer Royal’s _Primer of Astronomy_ may be recommended; Young’s _Elements of Astronomy_ is a little more advanced, and Sir R. S. Ball’s _Story of the Heavens_, Newcomb’s _Popular Astronomy_, and Proctor’s _Old and New Astronomy_ enter into the subject in much greater detail. Young’s _General Astronomy_ may also be recommended to those who are not afraid of a little mathematics. There are also three modern English books dealing generally with the history of astronomy, in all of which the biographical element is much more prominent than in this book: viz. Sir R. S. Ball’s _Great Astronomers_, Lodge’s _Pioneers of Science_, and Morton’s _Heroes of Science: Astronomers_.

II. SPECIAL PERIODS.

_Chapters I. and II._—In addition to the general histories quoted above—especially _Wolf_—I have made most use of Tannery’s _Recherches sur l’Histoire de l’Astronomie Ancienne_ and of several biographical articles (chiefly by De Morgan) in Smith’s _Dictionary of Classical Biography and Mythology_. Ideler’s _Chronologische Untersuchungen_, Hankel’s _Geschichte der Mathematik im Alterthum und Mittelalter_, G. C. Lewis’s _Astronomy of the Ancients_, and Epping & Strassmaier’s _Astronomisches aus Babylon_ have also been used to some extent. Unfortunately my attention was only called to Susemihl’s _Geschichte der Griechischen Litteratur in der Alexandriner Zeit_ when most of my book was in proof, and I have consequently been able to make but little use of it.

I have in general made no attempt to consult the original Greek authorities, but I have made some use of translations of Aristarchus, of the _Almagest_, and of the astronomical writings of Plato and Aristotle.

_Chapter III._—The account of Eastern astronomy is based chiefly on Delambre, and on Hankel’s _Geschichte der Mathematik im Alterthum und Mittelalter_; to a less extent on Whewell. For the West I have made more use of Whewell, and have borrowed biographical material for the English writers from the _Dictionary of National Biography_. I have also consulted a good many of the original astronomical books referred to in the latter part of the chapter.

I know of no accessible book in English to which to refer students except _Whewell_.

_Chapter IV._—For biographical material, for information as to the minor writings, and as to the history of the publication of the _De Revolutionibus_ I have used little but Prowe’s elaborate _Nicolaus Coppernicus_, and the documents printed in it. My account of the _De Revolutionibus_ is taken from the book itself. The portrait is taken from Dandeleau’s engraving of a picture in Lalande’s possession. I have not been able to discover any portrait which was clearly made during Coppernicus’s lifetime, but the close resemblance between several portraits dating from the 17th century and Dandeleau’s seems to shew that the latter is substantially authentic.

There is a readable account of Coppernicus, as well as of several other astronomers, in Bertrand’s _Fondateurs de l’Astronomie Moderne_; but I have not used the book as an authority.

_Chapter V._—For the life of Tycho I have relied chiefly on Dreyer’s _Tycho Brahe_, which has also been used as a guide to his scientific work; but I have made constant reference to the original writings: I have also made some use of Gassendi’s _Vita Tychonis Brahe_. The portrait is a reproduction of a picture in the possession of Dr. Crompton of Manchester, described by him in the _Memoirs of the Manchester Literary and Philosophical Society_, Vol. VI., Ser. III. For minor Continental writers I have used chiefly _Wolf_ and _Delambre_, and for English writers, _Whewell_, various articles by De Morgan quoted by him, and articles in the _Dictionary of National Biography_.

Students will find in Dreyer’s book all that they are likely to want to know about Tycho.

_Chapter VI._—For Galilei’s life I have used chiefly Karl von Gebler’s _Galilei und die Römische Curie_, partly in the original German form and partly in the later English edition (translated by Mrs. Sturge). For the disputed questions connected with the trial I have relied as far as possible on the original documents preserved in the Vatican, which have been published by von Gebler and independently by L’Épinois in _Les Pièces du Procès de Galilée_: in the latter book some of the most important documents are reproduced in facsimile. For personal characteristics I have used the charming _Private Life of Galileo, compiled chiefly from his correspondence and that of his daughter Marie Céleste_. I have also read with great interest the estimate of Galilei’s work contained in H. Martin’s _Galilée_, and have probably borrowed from it to some extent. What I have said about Galilei’s scientific work has been based almost entirely on study of his own books, either in the original or in translation: I have used freely the translations of the _Dialogue on the Two Chief Systems of the World_ and of the _Letter to the Grand Duchess Christine_ by Salusbury, that of the _Two New Sciences_ by Weston (as well as that by Salusbury), and that of the _Sidereal Messenger_ by Carlos. I have also made some use of various controversial tracts written by enemies of Galilei, which are to be found (together with his comments on them) in the magnificent national edition of his works now in course of publication; and of the critical account of Galilei’s contributions to dynamics contained in Mach’s _Geschichte der Mechanik_.

_Wolf_ and _Delambre_ have only been used to a very small extent in this chapter, chiefly for the minor writers who are referred to.

The portrait is a reproduction of one by Sustermans in the Uffizi Gallery.

There is an excellent popular account of Galilei’s life and work in the _Lives of Eminent Persons_ published by the Society for the Diffusion of Useful Knowledge; students who want fuller accounts of Galilei’s life should read Gebler’s book and the _Private Life_, which have been already quoted, and are strongly recommended to read at any rate parts of the _Dialogue on the Two Chief Systems of the World_, either in the original or in the picturesque old translation by Salusbury: there is also a modern German version of this book, as well as of the _Two New Sciences_, in Ostwald’s series of _Klassiker der exakten Wissenschaften_.

_Chapter VII._—For Kepler’s life I have used chiefly _Wolf_ and the life—or rather biographical material—given by Frisch in the last volume of his edition of Kepler’s works, also to a small extent Breitschwerdt’s _Johann Keppler_. For Kepler’s scientific discoveries I have used chiefly his own writings, but I am indebted to some extent to _Wolf_ and _Delambre_, especially for information with regard to his minor works. The portrait is a reproduction of one by Nordling given in Frisch’s edition.

The _Lives of Eminent Persons_, already referred to, also contains an excellent popular account of Kepler’s life and work.

_Chapter VIII._—I have used chiefly _Wolf_ and _Delambre_; for the English writers Gascoigne and Horrocks I have used _Whewell_ and articles in the _Dict. Nat. Biog._ What I have said about the work of Huygens is taken directly from the books of his which are quoted in the text; and for special points I have consulted the _Principia_ of Descartes, and a very few of Cassini’s extensive writings.

There is no obvious book to recommend to students.

_Chapter IX._—For the external events of Newton’s life I have relied chiefly on Brewster’s _Memoirs of Sir Isaac Newton_; and for the history of the growth of his ideas on the subject of gravitation I have made extensive use of W. W. R. Ball’s _Essay on Newton’s Principia_, and of the original documents contained in it. I have also made some use of the articles on Newton in the _Encyclopaedia Britannica_ and the _Dictionary of National Biography_; as well as of Rigaud’s _Correspondence of Scientific Men of the Seventeenth Century_, of Edleston’s _Correspondence of Sir Isaac Newton and Prof. Cotes_, and of Baily’s _Account of the Rev^{d.} John Flamsteed_. The portrait is a reproduction of one by Kneller.

Students are recommended to read Brewster’s book, quoted above, or the abridged _Life of Sir Isaac Newton_ by the same author. The Laws of Motion are discussed in most modern textbooks of dynamics; the best treatment that I am acquainted with of the various difficulties connected with them is in an article by W. H. Macaulay in the _Bulletin of the American Mathematical Society_, Ser. II., Vol. III., No. 10, July 1897.

_Chapter X._—For Flamsteed I have used chiefly Baily’s _Account of the Rev^{d.} John Flamsteed_; for Bradley little but the _Miscellaneous Works and Correspondence of the Rev. James Bradley_ (edited by Rigaud), from which the portrait has been taken. My account of Halley’s work is based to a considerable extent on his own writings; there is a good deal of biographical information about him in the books already quoted in connection with Newton and Flamsteed, and there is a useful article on him in the _Dictionary of National Biography_. I have made a good deal of use in this chapter of _Wolf_ and _Delambre_, especially in dealing with Continental astronomers; and for special parts of the subject I have used Grant’s _History of Physical Astronomy_, Todhunter’s _History of the Mathematical Theories of Attraction and the Figure of the Earth_, and Poynting’s _Density of the Earth_.

_Chapter XI._—Most of the biographical material has been taken from _Wolf_ from articles in various encyclopaedias and biographical dictionaries, chiefly French, and from Delambre’s _Eloge_ of Lagrange. The two portraits are taken respectively from Serret’s edition of the _Oeuvres de Lagrange_ and from the Academy’s edition of the _Oeuvres Complètes de Laplace_. Gautier’s _Essai Historique sur le Problème des Trois Corps_ and Grant’s _History of Physical Astronomy_ have been the books most used for my account of the scientific contributions of the various astronomers dealt with; I have also consulted various modern treatises on gravitational astronomy, especially Tisserand’s _Mécanique Céleste_, Brown’s _Lunar Theory_, and to a less extent Cheyne’s _Planetary Theory_ and Airy’s _Gravitation_. For special points I have used Todhunter’s _History_, already referred to. Of the original writings I have made a good deal of use of Laplace’s _Mécanique Céleste_ as well as of his _Système du Monde_; I have also consulted a certain number of his other writings and of those of Lagrange and Clairaut; but have made no systematic study of them.

Students who wish to know more about gravitational astronomy but have little knowledge of mathematics should try to read Airy’s _Gravitation_; Herschel’s _Outlines of Astronomy_ and Grant’s _History_ (quoted above) also deal with the subject without employing mathematics, and are tolerably intelligible.

_Chapter XII._—The account of Herschel’s career is taken chiefly from Mrs. John Herschel’s _Memoir of Caroline Herschel_, from Miss A. M. Clerke’s _The Herschels and Modern Astronomy_, from the _Popular History of Astronomy in the Nineteenth Century_ by the same author, and from Holden’s _Sir William Herschel, his Life and Works_. The last three books and the _Synopsis and Subject Index to the Writings of Sir William Herschel_ by Holden & Hastings have been my chief guides to Herschel’s long series of papers; but nearly every thing that I have said about his chief pieces of work is based on his own writings. I have made also some little use of Grant’s _History_ (already quoted), of _Wolf_, and of Miss Clerke’s _System of the Stars_.

Students are recommended to read any or all of the first four books named above; the _Memoir_ gives a charming picture of Herschel’s personal life and especially of his relations with his sister. There is also a good critical account of Herschel’s work on sidereal astronomy in Proctor’s _Old and New Astronomy_.

_Chapter XIII._—Except in the articles dealing with gravitational astronomy I have constantly used Miss Clerke’s _History_ (already quoted), a book which students are strongly recommended to read; and in dealing with the first half of the century I have been helped a good deal by Grant’s _History_. But for the most part the materials for the chapter have been drawn from a great number of sources—consisting very largely of the original writings of the astronomers referred to—which it would be difficult and hardly worth while to enumerate; for the lives of astronomers (especially of English ones), as well as for recent astronomical history generally, I have been much helped by the obituary notices and the reports on the progress of astronomy which appear annually in the _Monthly Notices_ of the Royal Astronomical Society.

I add the names of a few books which deal with special parts of modern astronomy in a non-technical way:—

_The Sun_, C. A. Young; _The Sun_, R. A. Proctor; _The Story of the Sun_, R. S. Ball; _The Sun’s Place in Nature_, J. N. Lockyer.

_The Moon_, E. Neison; _The Moon_, T. G. Elger.

_Saturn and its System_, R. A. Proctor.

_Mars_, Percival Lowell.

_The World of Comets_, A. Guillemin (a well-illustrated but uncritical book, now rather out of date); _Remarkable Comets_, W. T. Lynn (a very small book full of useful information); _The Great Meteoritic Shower of November_, W. F. Denning.

_The Tides and Kindred Phenomena in the Solar System_, G. H. Darwin.

_Remarkable Eclipses_, W. T. Lynn (of the same character as his book on Comets.)

_The System of the Stars_, A. M. Clerke.

_Spectrum Analysis_, H. Schellen; _Spectrum Analysis_, H. E. Roscoe.

INDEX OF NAMES.

_Roman figures refer to the chapters, Arabic to the articles. The numbers given in brackets after the name of an astronomer are the dates of birth and death. All dates are_ A.D. _unless otherwise stated. In cases in which an authors name occurs in several articles, the numbers of the articles in which the principal account of him or of his work is given are printed in clarendon type thus_: =286=. _The names of living astronomers are italicised._

Abul Wafa. _See_ Wafa

Adams (1819-1892), XIII. 286, 287, 289

Adelard. _See_ Athelard

Airy (1801-1892), X. 227 _n_; XIII. =281=, =282=

Albategnius (?-929), II. 53; III. =59=, 66, 68 _n_; IV. 84, 85

Albert (of Prussia), V. 94

Albertus Magnus (13th cent.), III. 67

Alcuin (735-804), III. 65

Alembert, d’. _See_ D’Alembert

Alexander, II. 31

Alfonso X. (1223-1284), III. =66=, 68; V. 94

Al Mamun, III. 57, 69

Al Mansur, III. 56

Al Rasid, III. 56

Alva, VII. 135

Anaxagoras (499 B.C.?-427 B.C.?), I. 17

Anaximander (610 B.C.-546 B.C.?), I. 11

Apian (1495-1552), III. =69=; V. 97; VII. 146

Apollonius (latter half of 3rd cent. B.C.), II. =38=, 39, 45, 51,
52 _n_; X. 205

Arago, XII. 254

Archimedes, II. 52 _n_; III. 62

Argelander (1799-1875), XIII. 280

Aristarchus (earlier part of 3rd cent. B.C.), II. =24=, =32=, 41,
42, 54; IV. 75

Aristophanes, II. 19

Aristotle (384 B.C.-322 B.C.), II. 24, =27-30=, 31, 47, 51, 52;
III. 56, 66, 67, 68; IV. 70, 77; V. 100; VI. 116, 121, 125, 134;
VIII. 163

Aristyllus (earlier part of 3rd cent. B.C.), II. =32=, 42

Arzachel (_fl._ 1080), III. =61=, 66

d’Ascoli, Cecco (13th cent.), III. 67

Athelard (beginning of 12th cent.), III. 66

Auzout (?-1691), VIII. =155=, 160; X. 198

Bacon, Francis (1561-1627), VI. 134; VIII. 163

Bacon, Roger (1214?-1294), III. =67=; VI. 118

Bailly, XI. 237

_Ball_, XIII. 278 _n_

Bär, Reymers (Ursus) (?-1600), V. 105

Barberini (Urban VIII.), VI. 125, 127, 131, 132

_Barnard_, XIII. 294, 295

Baronius, VI. 125

Barrow, Isaac, IX. 166

Bayer, XII. 266

Bede, III. 65

Begh, Ulugh. _See_ Ulugh Begh

Bellarmine, VI. 126

Bentley, IX. 191

Berenice, I. 12

Bernouilli, Daniel (1700-1782), XI. 230

Bernouilli, James (1654-1705), XI. 230

Bernouilli, John (1667-1748), XI. 229, 230

Bessel (1784-1846), X. 198 _n_, 218; XIII. 272, =277-278=, 279, 280

Bille, V. 99

Bliss (1700-1764), X. 219

Bond, William Cranch (1789-1859), XIII. 295

Borelli (1608-1679), IX. 170

Bouguer (1698-1758), X. 219, =221=

Boullian. _See_ Bullialdus

Bouvard, XI. 247 _n_; XIII. 289

Bradley (1693-1762), X. 198, =206-218=, 219, 222-226; XI. 233;
XII. 257, 258, 263, 264; XIII. 272, 273, 275, 277

Brahe, Tycho (1546-1601), III. 60, 62; V. 97, 98 _n_, =99-112=;
VI. 113, 117, 127; VII. 136-139, 141 _n_, 142, 145, 146, 148;
VIII. 152, 153, 162; IX. 190; X. 198, 203, 225; XII. 257; XIII. 275

Brudzewski, IV. 71

Bruno, VI. 132

Bullialdus (1605-1694), XII. 266

Bunsen, XIII. 299

Burckhardt (1773-1825), XI. 241

Bürg (1766-1834), XI. 241

Bürgi (1552-1632), V. =97=, =98=; VIII. 157

Burney, Miss, XII. 260

_Burnham_, XIII. 309

Caccini, VI, 125

Caesar, II. 21; III. 67

Callippus (4th cent. B.C.), II. =20=, =26=, 27

Capella, Martianus (5th or 6th cent. A.D.), IV. 75

Carlyle, XI. 232

Carrington (1826-1875), XIII. 298, 302

Cartesius. _See_ Descartes

Cassini, Count (1748-1845), X. 220

Cassini, Giovanni Domenico (1625-1712), VIII. =160=, =161=; IX. 187;
X. 216, =220=, 221, 223; XII. 253, 267; XIII. 297

Cassini, Jacques (1677-1756), X. =220=, =221=, 222

Cassini de Thury (1714-1784), X. 220

Castelli, VI. 125

Catherine II., X. 227; XI. 230, 232

Cavendish (1731-1810), X. 219

Cecco d’Ascoli (1257?-1327), III. 67

_Chandler_, XIII. 285

Charlemagne, III. 65

Charles II., X. 197, 223

_Charlois_, XIII. 294

Christian (of Denmark), V. 106

Christine (the Grand Duchess), VI. 125

Clairaut (1713-1765), XI. 229, 230, =231=, 232, =233-235=, 237, 239,
248; XIII. 290

Clement VII., IV. 73

_Clerke_, XIII. 289 _n_

Clifford, IX. 173 _n_

Colombe, Ludovico delle, VI. 119 _n_

Columbus, III. 68

La Condamine (1701-1774), X. 219, =221=

Conti, VI. 125

Cook, X. 227

Coppernicus (1473-1543), II. 24, 41 _n_, 54; III. 55, 62, 69;
=IV.= _passim_; V. 93-97, 100, 105, 110, 111; VI. 117, 126, 127,
129; VII. 139, 150; IX. 186, 194; XII. 257; XIII. 279

_Cornu_, XIII. 283

Cosmo de Medici, VI. 121

Cotes (1682-1716), IX. 192

Crosthwait, X. 198

Cusa, Nicholas of (1401-1464), IV. 75

D’Alembert (1717-1783), X. 215; XI. 229, 230, 231 _n_, =232-235=,
237-239, 248

Damoiseau (1768-1846), XIII. 286

Dante, III. 67; VI. 119 _n_

_Darwin_, XIII. 292, 320

Da Vinci. _See_ Vinci

Dawes (1799-1868), XIII. 295

Delambre, II. 44; X. 218; XI. 247 _n_; XIII. 272

Delaunay (1816-1872), XIII 286, 287

De Morgan, II. 52 _n_

Descartes (1596-1650), VIII. 163

Diderot, XI. 232

Digges, Leonard (?-1571?), VI. 118

Digges, Thomas (?-1595), V. 95

Donati (1826-1873), XIII. 304

Doppler (1803-1853), XIII. 302

_Dreyer_, XIII. 308

_Dunér_, XIII. 302

Ecphantus (5th or 6th cent. B.C.), II. 24

Eddin, Nassir (1201-1273), III. =62=, 68; IV. 73

Encke (1791-1865), X. 227; XIII. 284

Eratosthenes (276 B.C.-195 or 196 B.C.), II. =33=, 45, 54; X. 221

Euclid (_fl._ 300 B.C.), II. 33, 52 _n_; III. 62, 66; VI. 115; IX. 165

Eudoxus (409 B.C.?-356 B.C.?), II. =26=, 27, 38, 42, 51

Euler (1707-1783), X. 215, 226; XI. 229, =230=, 231 _n_, =233-236=,
237, 239, 242, 243; XIII. 290

Fabricius, John (1587-1615?), VI. 124

Ferdinand (the Emperor), VII. 137, 147

Fernel (1497-1558), III. 69

Ferrel, XIII. 287

Field (1525?-1587), V. 95

Fizeau (1819-1896), XIII. 283

Flamsteed (1646-1720), IX. 192; X. =197=, =198=, 199, 204, 207 _n_,
218, 225; XII. 257; XIII. 275, 281

Fracastor (1483-1553), III. =69=; IV. 89; VII. 146

Fraunhofer (1787-1826), XIII. =299=, 311

Frederick II. (of Denmark), V. 101, 102, 106

Frederick II. (the Emperor), III. 66

Frederick II. (of Prussia), XI. 230, 232, 237

Galen, II. 20; III. 56; VI. 116

Galilei, Galileo (1564-1642), II. 30 _n_, 47; IV. 73; V. 96, 98 _n_;
=VI.= _passim_; VII. 135, 136, 138, 145, 151; VIII. 152-154, 157,
163; IX. 165, 168, 170, 171, 173, 179, 180, 186, 190, 195; X. 216;
XII. 253, 257, 263, 268; XIII. 278, 295

Galilei, Vincenzo, VI. 113

_Galle_, XIII. 281, 289

Gascoigne (1612?-1644), VIII. =155=, 156; X. 198

Gauss (1777-1855), XIII. =275=, =276=, 294

Gautier (1793-1881), XIII. 298

Genghis Khan, III. 62

George III, XII. 254-256

Gerbert (?-1003), III. 66

Gherardo of Cremona (1114-1187), III. 66

Gibbon, II. 53 _n_

Giese, IV. 74

Gilbert (1540-1603), VII. 150

_Gill_, XIII. 280, 281

_Glaisher_, XIII. 289 _n_

Godin (1704-1760), X. 221

Goodricke (1764-1786), XII. 266

Grant, XIII, 289 _n_

Grassi, VI. 127

Gregory, James (1638-1675), IX. =168=, 169; X. 202

Gregory XIII., II. 22

Gyldén (1841-1896), XIII. 288

Hainzel, V. 99

_Hale_, XIII. 301

Halifax, John. _See_ Sacrobosco

Halifax (Marquis of), IX. 191

_Hall_, XIII. 283 _n_, 295

Halley (1656-1742), VIII. 156; IX. =176=, =177=, 192 _n_; X. 198,
=199-205=, 206, 216, 223, 224, 227; XI. 231, 233, 235, 243;
XII. 265; XIII. 287, 290

Hansen (1795-1874), XIII. 282, 284, =286=, 290

_Harkness_, XIII. 301

Harriot (1560-1621), VI. 118, 124

Harrison, X. 226

Harun al Rasid, III. 56

Helmholtz (1821-1894), XIII. 319

Hencke (1793-1866), XIII. 294

Henderson (1798-1844), XIII. 279

Heraclitus (5th cent. B.C.), 11, 24

Herschel, Alexander, XII. 251

Herschel, Caroline (1750-1848), XII. 251, 254-256, 260

Herschel, John (1792-1871), I. 12; X. 221; XI. 242; XII. 256;
XIII. 289 _n_, =306-308=, 309, 316, 317, 319

Herschel, William (1738-1822), IX. 168; X. 223, 227; XI. 250;
=XII.= _passim_; XIII. 272, 273, 294, 296, 306-311, 317, 318

Hesiod, 11, 19, 20

Hevel (1611-1687), VIII. =153=; X. 198; XII. 268

Hicetas (6th or 5th cent. B.C.), II. 24; IV. 75

_Hill_, XI. 233 _n_; XIII. =286=, 290

Hipparchus (2nd cent. B.C.), I. 13; II. 25, 27, 31, 32, =37-44=,
45, 47-52, 54; III 63, 68; IV. 73, 84; V. 111; VII. 145

Hippocrates, III. 56

Holwarda (1618-1651), XII. 266

Holywood. _See_ Sacrobosco

Honein ben Ishak (?-873), III. 56

Hooke (1635-1703), IX. =174=, 176; X. 207, 212

Horky, VI. 121

Horrocks (1617?-1641), VIII. =156=; IX. 183; X. 204

_Howlett_, XIII. 298

_Huggins_, XIII. 301, 304, 311-313

Hulagu Khan, III. 62

Humboldt, XIII. 298

Hutton (1737-1823), X. 219

Huygens (1629-1695), V. 98 _n_; VI. 123; VIII. =154=, =155=, =157=,
=158=; IX. 170-172, 191

Hypatia (?-415), II. 53

Ibn Yunos. _See_ Yunos

Ishak ben Honein (?-910 or 911), III. 56

James I., V. 102; VII. 147

James II., IX. 192

_Janssen_, XIII. 301, 307 _n_

Joachim. _See_ Rheticus

Kaas, V. 106

Kant, XI. 250; XII. 258, 260; XIII. 287

_Kapteyn_, XIII. 280

_Kelvin_, XIII. 292

Kepler (1571-1630), II. 23, 51 _n_, 54; IV. 91; V. 94, 100, 104,
108-110; VI. 113, 121, 130, 132; =VII.= _passim_; VIII. 152, 156,
160; IX. 168-170, 172, 175, 176, 190, 194, 195; X. 202, 205, 220;
XI. 228, 244; XIII. 294, 301, 309

Kirchhoff (1824-1887), XIII. =299=, =300=, 311

Kirkwood (1815-1895), XIII. 294, 297

Koppernigk, IV. 71

Korra, Tabit ben. _See_ Tabit

Lacaille (1713-1762), X. =222-224=, 225, 227; XI. 230, 233, 235;
XII. 257, 259

La Condamine (1701-1774), X. 219, =221=

Lagrange (1736-1813), IX. 193; XI. 229, 231 _n_, 233 _n_, 236, =237=,
238-240, =242-245=, 247, 248; XII. 251; XIII. 293, 294

Lalande (1732-1807), XI. =235=, 241, 247 _n_; XII. 265

Lambert (1728-1777), XI. 243; XII. 265

Lami, IX. 180 _n_

Landgrave of Hesse. _See_ William IV.

_Langley_, XIII. 307

Lansberg (1561-1632), VIII. 156

Laplace (1749-1827), XI. 229, 231 _n_, =238-248=, =250=; XII. 251,
256; XIII. 272, 273, 282, 286-288, 290, 293, 297, 318-320

Lassell (1799-1880), XII. 267; XIII. =295=

Lavoisier, XI. 237

Legendre (1752-1833), XIII. =275=, 276

Leibniz, IX. 191, 193

Lemaire, XII. 255

Leverrier (1811-1877), XIII. 282, 284, =288=, =289=, 290, 293, 294

Lexell (1740-1784), XII. 253

Lindenau, XI. 247 _n_

Lionardo da Vinci. _See_ Vinci

Lippersheim (?-1619), VI. 118

Locke, IX. 191

_Lockyer_, XIII. 301, 302

_Loewy_, XIII. 283 _n_

Louis XIV., VIII. 160

Louis XVI., XI. 237

Louville (1671-1732), XI. 229

Lubbock (1803-1865), XIII. 286, 292

Luther, IV. 73; V. 93

Machin (?-1751), X. 214

Maclaurin (1698-1746), X. =196=; XI. 230, 231; XII. 251

Maestlin, VII. 135

Maraldi, X. 220

Marius (1570-1624), VI. =118=; VII. 145

Martianus Capella. _See_ Capella

Maskelyne (1732-1811), X. =219=; XII. 254, 265

Mason (1730-1787), X. 226; XI. 241

Matthias (the Emperor), VII. 143, 147

Maupertuis (1698-1759), X. 213, =221=; XI. 229, 231

Maxwell (1831-1879), XIII. 297

Mayer, Tobias (1723-1762), X. 217, =225=, =226=; XI. 233, 241;
XII. 265

Melanchthon, IV. 73, 74; V. 93

Messier (1730-1817), XII. 259, 260

Meton (460 B.C.?-?), II. 20

Michel Angelo, VI. 113

Michell, John (1724-1793), X. 219; XII. 263, 264

_Michelson_, XIII. 283

Molyneux (1689-1728), X. 207

Montanari (1632-1687), XII. 266

Müller. _See_ Regiomontanus

Napier, V. 97 _n_

Napoleon I., XI. 238; XII. 256

Napoleon, Lucien, XI. 238 _n_

Nassir Eddin. _See_ Eddin, Nassir

_Newcomb_, X. 227 _n_; XIII. =283=, =286=, 290

Newton (1643-1727). II. 54; IV. 75; VI. 130, 133, 134; VII. 144, 150;
VIII. 152; =IX.= _passim_; X. 196-200, 211, 213, 215-217, 219, 221;
XI. 228, 229, 231-235, 238, 249; XII. 257; XIII. 273, 299

Niccolini, VI. 132

Nicholas of Cusa (1401-1464), IV. 75

Nonius (1492-1577), III. 69

Norwood (1590?-1675), VIII. =159=; IX. 173

Numa, II. 21

Nunez. _See_ Nonius

_Nyrén_, XIII. 283 _n_

Olbers (1758-1840), XIII. 294

Orange, Prince of, V. 107

Osiander, IV. 74; V. 93

_Palisa_, XIII. 294

Palitzsch (1723-1788), XI. 231

Pemberton, IX. 192

Philolaus (5th cent. B.C.), II. =24=; IV. 75

Piazzi (1746-1826), XIII. 294

Picard (1620-1682), VIII. =155=, =157=, =159-161=, 162; IX. 174;
X. 196, 198, 221

_Pickering_, XIII. 314, 316

Plana (1781-1869), XIII. 286

Plato (428 B.C.?-347 B.C.?), II. =24=, =25=, 26, 51; IV. 70

Plato of Tivoli (_fl._ 1116), III. 66

Pliny (23 A.D.-79 A.D.), II. 45

Plutarch, II. 24; XIII. 301

Pogson (1829-1891), XIII. 316

_Poincaré_, XIII. 288

Poisson (1781-1840), XIII. 286, 293

Pontécoulant (1795-1874), XIII. 286

Porta, VI. 118

Posidonius (135 B.C.?-51 B.C.?), II 45, 47

Pouillet (1791-1868), XIII. 307, 319

Pound, X. 206, 216

Prévost (1751-1839), XII. 265

Pritchard (1808-1893), XIII. 278 _n_, =279=, 316

Ptolemy, Claudius (_fl._ 140 A.D.), II. 25, 27, 32, 37, =46-52=, 53,
54; III. 55, 57, 59-63, 68; IV. 70, 76, 80, 83-87, 89, 91; V. 94,
105; VI. 121, 129, 134; VII. 145; VIII. 161; IX. 194; X. 205;
XI. 236

Ptolemy Philadelphus, II. 31

Purbach (1423-1461), III. =68=; IV. 71

Pythagoras (6th cent. B.C.), I. 11, 14; II. =23=, 28, 47, 51, 54

Recorde (1510-1558), V. 95

Regiomontanus (1436-1476), III. =68=, 69; IV. 70, 71; V. 97, 110

Reimarus. _See_ Bär

Reinhold (1511-1553), V. =93-96=; VII. 139

Reymers. _See_ Bär

Rheticus (1514-1576), IV. =73=, =74=; V. =93=, =94=, 96

Ricardo, II. 47 _n_

Riccioli (1598-1671), VIII. 153

Richer (?-1696), VIII. =161=; IX. 180, 187; X. 199, 221

Rigaud. X. 206 _n_

Roemer (1644-1710), VIII. =162=; X. 198, 210, 216, 220, 225; XIII. 283

Rosse (1800-1867), XIII. 310, 317

Rothmann (_fl._ 1580), V. =97=, =98=, 106

Rudolph II. (the Emperor), V. 106-108; VII. 138, 142, 143

Sabine (1788-1883), XIII. 298

Sacrobosco (?-1256?), III. =67=, 68

St. Pierre, X. 197

Savary (1797-1841), XIII. 309

Scheiner (1575-1650), VI. =124=, 125; VII. =138=; VIII. =153=;
XII. 268

_Schiaparelli_, XIII. 297

Schomberg, IV. 73

Schoner, IV. 74

Schönfeld (1828-1891), XIII. 280

Schroeter (1745-1816), XII. 267, =271=

Schwabe (1789-1875), XIII. 298

Secchi (1818-1878), XIII. 311, 312

_See_, XIII. 320

Seleucus (2nd cent, B.C.), II. 24

Shakespeare, VI. 113

Sharp (1651-1742), X. 198

Slusius, IX. 169

Smith, XII. 251

Snell (1591-1626), VIII. 159; IX. 173

Sosigenes (_fl._ 45 B.C.), II. 21

South (1785-1867), XIII. 306

Struve, F. G. W. (1793-1864), XIII. 279, 309

_Struve, O._, XIII. 283 _n_

Svanberg (1771-1851), X. 221

Sylvester II. _See_ Gerbert

Tabit ben Korra (836-901), III. =56=, =58=, 68; IV. 84

Tamerlane, III. 63

_Tannery_, II. 36 _n_

Thales (640 B.C.?-546 B.C.?), II. =23=; III. 55

Theon (_fl._ 365 A.D.), II. 53

Theophrastus, II. 24

Theophylactus, IV. 72

Thomson, T., X. 208 _n_

_Thomson, William._ _See_ _Kelvin_

Thury, Cassini de. _See_ Cassini de Thury

Timocharis (beginning of 3rd cent. B.C.). II. =32=, 42; IV. 84

Tycho Brahe, _See_ Brahe

Ulugh Begh (1394-1449), III. =63=, 68; IV. 73

Urban VIII. (Barberini), VI. 125, 127, 131, 132

Ursus. _See_ Bär

Varignon, IX. 180 _n_

Vinci, Lionardo da (1452-1519), III. 69

_Vogel_, XIII. 313, 314

Voltaire, II. 21; XI, 229

Wafa, Abul (939 or 940-998), III. =60=, 68 _n_; IV. 85; V. 111

Wallenstein, VII. 149

Walther (1430-1504), III. 68; V. 97

Wargentin (1717-1783), X. 216

Watzelrode, IV. 71

Wefa. _See_ Wafa

Welser, VI. 124

Whewell (1794-1866), XIII. 292

William IV. (Landgrave of Hesse) (1532-1592), V. =97=, =98=, 100,
105, 106, 110

Wilson (1714-1786), XII. =268=; XIII. 298

_Wolf, Max_, XIII. 294

Wolf, Rudolf (1816-1893), XIII. 298

Wollaston (1766-1828), XIII. 299

Wren (1632-1723), IX. 174, 176

Wright, Thomas (1711-1786), XII. 258, 265

_Young_, XIII. 301

Yunos, Ibn (?-1008), III. =60=, 62, 68 _n_

von Zach, XI. 247 _n_

GENERAL INDEX.

_Roman figures refer to the chapters, Arabic to the articles. When several articles are given under one heading the numbers of the most important are printed in clarendon type, thus_: =207=. _The names of books are printed in italics._

Aberration, X. 206, =207-211=, 212, 213, 216, 218; XII. 263;
XIII. 277, 283, 284

Académie Française, XI. 232, 238

Academy of Berlin, XI. 230, 237

Academy of St. Petersburg, XI. 230, 233

Academy of Sciences (of Paris), X. 221, 223; XI. 229-233, 235-237

Academy of Turin, XI. 237, 238

Acceleration, VI. =133=; IX. =171=, 172, 173, 179, 180, 185, 195;
X. 223

_Ad Vitellionem Paralipomena_ (of Kepler), VII. 138

_Alae sive Scalae_ (of Digges), V. 95

Aldebaran, III. 64; XIII. 316 _n_

Alexandrine school, II. 21, 31-33, 36-38, 45, 53

_Alfonsine Tables_, III. =66=, 68; V. 94, 96, 99

Algol, XII. 266; XIII. 314, 315

_Almagest_ (of Ptolemy), II. =46-52=; III. 55, 56, 58, 60, 62, 66, 68;
IV. 75, 76, 83

_Almagest_ (of Abul Wafa), III. 60

_Almagest, New_ (of Kepler), VII. 148

_Almagest, New_ (of Riccioli), VIII. 153

_Almanac, Nautical_, X. 218; XIII. 286, 288, 290

Almanacks, I. 18 _n_; II. 20, 38; III. 64, 68; V. 94, 95, 100;
VII. 136; X. 218, 224; XIII. 286, 288, 290

Altair, III. 64; XIII. 316 _n_

Analysis, analytical methods, X. =196=; XI. 234

Angles, measurement of, I. 7

Annual equation, V. =111=; VII. 145

Annual motion of the earth. _See_ Earth, revolution of

Annual motion of the sun. _See_ Sun, motion of

Annual parallax. _See_ Parallax, stellar

Annular eclipse, II. =43=; VII. 145

Anomalistic month, II. 40

Ἀντιχθών, II. 24

Apex of solar motion, XII. 265

Aphelion, IV. 85

Apogee, II. =39=, 40, 48; III. 58, 59; IV. 85; V. 111; IX. 184 XI. 233

Apparent distance, I. 7

Apple, Newton’s, IX. 170

Apse, apse-line, II. =39=, 40, 48; IV. 85; IX. 183; XI. 235, 236, 242,
246

Arabic numerals, III. 64; V. 96

Arabs, Arab astronomy, II. 46, 53; III. =56-61=, =64=, 66, 68; V. 110;
VIII. 159; XII. 266

Arctic regions, II. 35

Arcturus, XII. 258

Aries, first point of (♈), I. =13=; II. 33, 42; IV. 83 _n_; V. 98,
III; X. 198

Asteroids. _See_ Minor planets

Astrolabe, II. 49; III. 66

Astrology, I. 16, =18=; III. 56; V. 99, 100; VII. 136, 149, 151

_Astronomiae Fundamenta_ (of Lacaille), X. 224

_Astronomiae Instauratae Mechanica_ (of Tycho), V. 107

_Astronomiae Instauratae Progvmnasmata_ (of Tycho), V. 104

Astronomical Society, German, XIII. 280

Astronomical Society, Royal, XII. 256, 263

_Astronomicum Caesareum_ (of Apian), V. 97

_Astronomisches Jahrbuch_, XII. 253

Astronomy, divisions of, XIII. 272

Astronomy, descriptive, XIII. =272=, 273, 294

Astronomy, gravitational, X. =196=; XIII. 272, 273, 286

Astronomy, observational, XIII. 272, 273

Astronomy, origin of, I. =2=

Astronomy, scope of, I. 1

Attraction. _See_ Gravitation

Autumnal equinox, I. II. _See also_ Equinox

Axioms. _See_ Laws of Motion

Axis (of an ellipse), XI. 236, 244, 245

Babylonians. _See_ Chaldaeans

Bagdad, III. 56, 57, 60, 68

Belts of Jupiter, XII. 267

Betelgeux, III. 64

Biela’s comet, XIII. 305

Binary stars. _See_ Stars, double and multiple

Bode’s _Astronomisches Jahrbuch_, XII. 253

Bodily tides, XIII. 292, 293

Brightness of stars. _See_ Stars, brightness of

Brooks’s comet, XIII. 305

Brucia, XIII. 294

Bureau des Longitudes, XI. 238

Cairo, III. 60

Calculus of Variations, XI. 237 _n_

Calendar, Greek, II. =19=, =20=, 21

Calendar, Gregorian, II. =22=; IX. 165 _n_; X. 217

Calendar, Julian, II. =21=, 22; III. 68; IV. 73; IX. 165 _n_;
X. 197 _n_, 217

Calendar, Mahometan, III. 56

Calendar, Roman, II. 21

Caliphs, III. 56, 57, 69

Canals of Mars, XIII. 297

Cartesianism, VIII. 163; IX. 191, 195; XI. 229

Castor, XII. 263, 264, 266

Catalogues of stars. _See_ Star-catalogues

Cavendish experiment, X. 219

Celestial latitude. _See_ Latitude, celestial

Celestial longitude. _See_ Longitude, celestial

Celestial sphere, I. =7=, =8=, 9-11, 13, 14; II. 24, 26, 33, 38-40,
45, 47, 51; III. 64, 67; IV. 78, 80, 83, 88; V. 98, 105; VI. 129;
VIII. 157; X. 198, 207, 208, 214; XII. 257; XIII. 272

Celestial sphere, daily motion of. _See_ Daily motion

Celestial spheres, II. 23, 26, 27, 38, 51, 54; III. 62, =68=; V. 100,
103

Centre of gravity, IX. 186

Centrifugal force, VIII. 158 _n_

Ceres, XIII. 276, 294

Chaldaeans (Babylonians), Chaldaean astronomy, I. 6, 11, 12, =16-18=;
II. 30, 34, 40, 51, 54; III. 56

Chart, photographic, XIII. 280

Chemistry of the sun, XIII. =299-301=, 303

Chinese astronomy, I. 6, 11

Chords, II. 47 _n_

Chromosphere, X. 205; XIII. =301=, 303

Chronometer, X. 226

Circular motion, II. 25, 26, 38, 51; IV. 76; VII. 139; VIII. =158=;
IX. =171-173=. _See also_ Eccentric, Epicycle

Circumpolar stars, I. =9=; II. 35

Clock. _See_ Pendulum clock _and_ Chronometer

Clustering power, XII. 261. _See also_ Condensation of nebulae

_Coelum Australe Stelliferum_ (of Lacaille), X. 223

Collimation error, X. 225 _n_

Comets, I. 1; II. 30; III. 68, =69=; V. 100, 103-105; VI. 127, 129;
VII. 144, =146=; VIII. 153; IX. =190=, 192; X. =200=, 205, 217,
224; XI. 228, =231=, 243, 248, 250; XII. 253, 256, 259;
XIII. 272, =291=, =304=, =305=, 307

Comet, Biela’s, XIII. 305

Comet, Brooks’s, XIII. 305

Comet, Encke’s, XIII. 291

Comet, Halley’s, VII. 146; X. =200=, 205; XI. =231=, 232; XIII. 291,
307

Comet, Lexell’s, XI. 248; XIII. 305

Comet, Olbers’s, XIII. 291

Comet, Pons-Brooks, XIII. 291

Comet, Tebbutt’s, XIII. 305

Comet, Tuttle’s, XIII. 291

_Cometographia_ (of Hevel), VIII. 153

_Commentaries on the Motions of Mars_ (of Kepler), VII. 135 _n_,
139, 141, 150 _n_

_Commentariolus_ (of Coppernicus), IV. =37=; V. 100

_Compleat System of Optics_ (of Smith), XII. 251

Complete induction, IX. 195

Condensation of nebulae, XI. 250; XII. 261; XIII. 318

Conic, conic section, VII. =140= _n_; XIII. 309

Conjunction, II. =43=, 48 _n_; III. 60; V. 110, III; X. 227

Conservation of energy, XIII. 319

Constant of aberration, X. =209=, 210; XIII. 283 _n_

Constellations, I. =12=, 13; II. 20, =26=, 34, =42=; X. =223=

Construction of the heavens, XII. 257. _See also_ Sidereal system,
structure of

Corona, VII. 145; X. 205; XIII. =301=, 303

Counter-earth, II. 24

Crape-ring, XII. 267; XIII. 295

Craters (on the moon), VIII. 153; XIII. 296

Curvature of the earth. _See_ Earth, shape of

Daily Motion (of the celestial sphere), I. 5, =8=, =9=, 10; II. 23,
24, 26, 33, 38, 39, 46, 47; III. 67, 68; IV. =78=, =80=, 83;
V. 98, 105; VI. 129; VIII. 157

D’Alembert’s principle, XI. 232, 237 _n_

Damascus, III. 57

_Darlegung_ (of Hansen), XIII. 286

Day, I. 4, II. 16; II. 47; XIII. 287, 293, 320

Day-and-night, I. 16 _n_

Day-hour, I. 16

Declination, II. =33=, 35, 39; X. 213, 218; XIII. 276

Declination circle, II. 33

_De Coelo_ (of Aristotle), II. 27

Deductive method, inverse, IX. 195

Deferent, II. =39=, 48, 51; III. 68; IV. 86, 87

Degree, I. 7

Deimos, XIII. 295

_De Magnete_ (of Gilbert), VII. 150

_De Motu_ (of Newton), IX. 177, 191

_De Mundi aetherei_ (of Tycho), V. 104

_De Nova Stella_ (of Tycho), V. 100

_De Revolutionibus_ (of Coppernicus), II. 41 _n_; IV. =74-92=;
V. 93, 94; VI. 126

_De Saturni Luna_ (of Huygens), VIII. 154

Descriptive astronomy, XIII. =272=, 273, 294

Deviation error, X. 225 _n_

_Dialogue on the Two Chief Systems_ (of Galilei), VI. 124 _n_,
=128-132=, 133

Differential method of parallax, VI. =129=; XII. 263; XIII. 278

Diffraction-grating, XIII. 299

Dione, VIII. 160

_Dioptrice_ (of Kepler), VII. 138

Direct motion, I. 14

Disturbing force. _See_ Perturbations

Diurnal method of parallax, XIII. =281=, 284

Doctrine of the sphere. _See_ Spherics

Doppler’s principle, XIII. =302=, 313, 314

Double hour, I. 16

Double-star method of parallax. _See_ Differential method of parallax

Double stars. _See_ Stars, double and multiple

Draconitic month, II. =40=, 43

_Durchmusterung_, XIII. 280

Dynamics, VI. 133, 134; IX. 179, 180; XI. 230, 232, 237

_Dynamique, Traité de_ (of D’Alembert), XI. 232

Earth, I. 1, 15, 17; II. 28, 29, 32, 39, 41, 43, 47, 49, 51; III. 66,
69; IV. 80, 86; VI. 117, 121, 133; VII. 136 _n_, 144, 145, 150;
VIII. 153, 154; IX. 173, 174, 179-182, 184, 186, 195; XI. 228, 245;
XIII. 285, 287, 292, 293, 297, 320. _See also_ the following
headings

Earth, density, mass of, IX. 180, 185, 189; X. =219=; XI. 235;
XIII. 282, 294

Earth, motion of, II. 24, 32, 47; IV. =73=, 76, =77=; V. 96. 97,
=105=; VI. 121, 125-127, =129-132=; VIII. 161, 162; IX. 186, 194;
XII. 257. _See also_ Earth, revolution of _and_ rotation of

Earth, revolution of, annual motion of, II. 23, =24=, 28 _n_, =30=,
47; IV. =75=, =77=, =79-82=, =85-88=, 89, 90, =92=; V. 111;
VI. 119, 126, =129=, 131, 133; VII. 139, 142, 146; VIII. 161;
IX. 172, 183; X. 207-210, 212, 227; XI. 235, 236, 240; XII. 263;
XIII. 278, 282, 283

Earth, rigidity of, XIII. 285, 292

Earth, rotation of, daily motion of, II. 23, =24=, 28 _n_; IV. =75=,
=78=, 79 _n_, =80=, 84; V. =105=; VI. 124, 126, =129=, =130=;
IX. 174, 194; X. 206, 207, 213; XIII. 281, 285, =287=, 320

Earth, shape of, II. =23=, =29=, =35=, =45=, =47=, 54; IV. 76; VIII.
=161=; IX. =187=, 188; X. 196, 213, 215, 220, =221=, 222, 223; XI.
229, =231=, 237, 248

Earth, size of, II. =36=, 41, 45, 47, 49; III. 57, 69; IV. 85;
VII. 145; VIII. =159=, 161; IX. 173, 174; X. =221=, 222, 223

Earth, zones of, II. =35=, 47

Earthshine, III. 69

Easter, rule for fixing, II. 20

Eccentric, II. 37, =39=, =40=, 41, =48=, =51=; III. 59; IV. =85=, =89=,
=91=; VII. 139, 150

Eccentricity, II. =39=; IV. 85; VII. =140= _n_; XI. 228, 236, 240,
244-246, 250; XIII. 294, 318

Eccentricity fund, XI. 245

Eclipses, I. 11, 15, =17=; II. 29, 32, 40-42, =43=, 47-49, 54;
III. 57, 68; IV. 76, 85; V. 110; VI. 127; VII. 145, 148: VIII. 162;
X. 201, 205, 210, 216, 227; XI. 240; XIII. 287, 301

Eclipses, annular, II. =43=; VII. 145

Eclipses, partial, II. 43

Eclipses, total, II. =43=; VII. 145; X. 205; XIII. =301=

Ecliptic, I. =11=, 13, 14; II. 26, 33, 35, 36, 38, 40, 42, 51; III.
58, 59, 68; IV. 80, 82-84, 87, 89; V. 111; VIII. 154; X. 203, 209,
213, 214, 227; XI. 235, 236, 244, 246, 250

Ecliptic, obliquity of, I. =11=; II. 35, 36, 42; III. 59, 68; IV. 83,
84; XI. 235, 236

École Normale, XI. 237, 238

École Polytechnique, XI. 237

Egyptians, Egyptian astronomy, I. 6, 11, 12, 16; II. 23, 26, 30, 45;
IV. 75

_Elements_ (of Euclid), III. 62, 66; IX. 165

Elements (of an orbit), XI. =236=, 240, 242, 244, 246; XIII. 275, 276

Elements, variation of. _See_ Variation of elements

Ellipse, II. 51 _n_; III. 66; VII. =140=, 141; IX. 175, 176, 190, 194;
X. 200, 209, 214; XI. 228, 236, 242, 244; XIII. 276, 278, 309

Ellipticity, X. 221

Empty month, II. =19=, 20

Empyrean, III. 68

Enceladus, XII. 255

Encke’s comet, XIII. 291

Encyclopaedia, the French, XI. 232

Energy, XIII. 319

Ephemerides. _See_ Almanacks

_Ephemerides_ (of Regiomontanus), III. 68

Epicycle, II. 37, =39=, 41, 45, =48=, =51=, 54; III. 68; IV. =85-87=,
=89-91=; VII. 139, 150; VIII. 163; IX. 170, 194

_Epitome_ (of Kepler), VI. 132; VII. 144, =145=

_Epitome_ (of Purbach), III. 68

Equant, II. =51=; III. 62; IV. 85, 89, 91; VII. 139, 150

Equation of the centre, II. =39=, 48; III. 60; V. 111

Equator, I. =9=, 10, 11; II. 33, 35, 39, 42; IV. 82, 84; V. 98;
VI. 129, 133; IX. 187; X. 207, 220, 221; XIII. 285

Equator, motion of. _See_ Precession

Equinoctial points, I. =11=, 13; II. 42. _See also_ Aries, first
point of

Equinoxes, I. =11=; II. 39, 42

Equinoxes, precession of. _See_ Precession

_Essai philosophique_ (of Laplace), XI. 238

Ether, XIII. 293, 299

Evection, II. =48=, 52; III. 60; IV. 85; V. 111; VII. 145

Evening star, I. 14. _See also_ Venus

_Exposition du Système du Monde_ (of Laplace), XI. =238=, 242 _n_,
=250=

Faculae, VIII. =153=; XIII. 300, 301, 303

Figure of the earth. _See_ Earth, shape of

Firmament, III. 68

First point of Aries, Libra. _See_ Aries, Libra, first point of

Fixed stars, I. 14. _See_ Stars

Fluxions, IX. 169, 191; X. 196

_Fluxions_ (of Maclaurin), XII. 251

Focus, VII. =140=, 141; IX. 175; XI. 236

Force, VI. 130; IX. =180=, 181

Fraunhofer lines, XIII. =299=, =300=, 303, 304

Front-view construction. _See_ Herschelian telescopes

Full month, II. =19=, 20

Full moon. _See_ Moon, phases of

_Fundamenta_ (of Hansen), XIII. 286

_Fundamenta Astronomiae_ (of Bessel), X. 218; XIII. =277=

Funds of eccentricity, inclination, XI. 245

Galactic circle, XII. 258, 260

Galaxy. _See_ Milky Way

Gauges, gauging. _See_ Star-gauging

Georgium Sidus. _See_ Uranus

Gravitation, gravity, II. 38 _n_; VII. 150; VIII. 158, 161;
=IX.= _passim_; X. 196, 201, 213, 215, 219, 220, 223, 226;
=XI.= _passim_; XII. 264; XIII. 282, 284, 286-293, 309, 319

Gravitational astronomy, X. =196=; XIII. 272, 273, 286

Gravity, variation of, VIII. =161=; IX. 180; X. 199, 217, 221, 223;
XI. =231=

Great Bear, I. 12; XII. 266

Great circle, I. =11=; II. 33, 42; IV. 82, 84

Gregorian Calendar. _See_ Calendar, Gregorian

Grindstone theory, XII. =258=; XIII. 317

_Hakemite Tables_, III. =60=, 62

Halley’s comet, VII. 146; X. =200=, 205; XI. =231=, 232; XIII. 291, 307

_Harmonics_ (of Smith), XII. 251

_Harmony of the World_ (of Kepler), VII. 144

Helium, XIII. 301

Herschelian telescope, XII. 255, 256

_Historia Coelestis_ (of Flamsteed), X. 198

Holy Office. _See_ Inquisition

Horizon, I. 3, 9; II. 29, =33=, 35, 39, 46; VIII. 161; XIII. 285

Horoscopes, V. 99

Hour, I. 16

Hydrostatic balance, VI. 115 _n_

Hyperbola, IX. 190; XI. 236 _n_

Hyperion, XIII. 295

_Ilkhanic Tables_, III. 62

_Il Saggiatore_ (of Galilei), VI. 127

Inclination, III. 58; IV. 89; XI. =228=, =244=, 245, 246, 250;
XIII. 294, 318

Inclination fund, XI. 245

_Index of Prohibited Books_, VI. 126, 132; VII. 145

Indians, Indian astronomy, I. 6; III. 56, 64

Induction, complete, IX. 195

Inequalities, long, XI. 243

Inequalities, periodic, XI. =242=, 243, 245, 247

Inequalities, secular, XI. =242=, 243-247; XIII. 282. _See also_
Perturbations

Inequality, parallactic, XIII. 282

Inferior planets, I. =15=; IV. 87, 88. _See also_ Mercury, Venus

Inquisition (Holy Office), VI. 126, 132, 133

Institute of France, XI. 241

Inverse deductive method, IX. 195

Inverse square, law of, IX. =172-176=, =181=, 195; XI. 233. _See also_
Gravitation

Ionian school, II. 23

Iris, XIII. 281

Irradiation, VI. 129

Island universe theory, XII. =260=; XIII. 317

Japetus, VIII. 160; XII. 267; XIII. 297

Julian Calendar. _See_ Calendar, Julian

Juno, XIII. 294

Jupiter, I. 14-16; 11. 25, 51; IV. 81, 87, 88; V. 98, 99; VI. 121,
127; VII. 136 n, 142, 144, 145, 150; VIII. 154, 156, 162; IX. 172,
181, 183, 185-187; X. 204, 216; XI. 228, 231, 235, 236, 243-245,
248; XII. =267=; XIII. 281, 288, 294, =297=, 305. _See also_ the
following headings

Jupiter, belts of, XII. 267

Jupiter, mass of, IX. 183, 185

Jupiter, rotation of, VIII. =160=; IX. 187; XIII. =297=

Jupiter, satellites of, II. 43; VI. =121=, =127=, 129, 133; VII.
=145=, 150; VIII. 160, 162; IX. 170, 184, 185; X. 210, =216=;
XI. 228, =248=; XII. 267; XIII. 283, =295=, 297

Jupiter’s satellites, mass of, XI. 248

Kepler’s Laws, VII. =141=, =144=, 145, 151; VIII. 152; IX. 169, 172,
175, 176, 186, 194, 195; X. 220; XI. 244; XIII. 294, 309

Latitude (celestial), II. =33=, 42, 43; III. 63; IV. 89

Latitude (terrestrial), III. 68, 69; IV. 73; X. =221=; XIII. 285

Latitude, variation of, XIII. 285

Law of gravitation. _See_ Gravitation

Laws of motion, VI. =130=, =133=; VIII. 152, 163; IX. 171, =179-181=,
183, 186, 194, 195; XI. 232

Leap-year, I. 17; II. =21=, 22

Least squares, XIII. =275=, 276

_Letter to the Grand Duchess_ (of Galilei), VI. 125

Level error, X. 225 _n_

Lexell’s comet, XI. 248; XIII. 305

Libra, first point of (♎), I. =13=; II. 42

Librations of the moon, VI. =133=; X. 226; XI. =237=, 239

_Libros del Saber_, III. 66

Light-equation, XIII. 283

Light, motion of, velocity of, VIII. =162=; X. 208-211, 216, 220;
XIII. 278, 279, =283=, 302. _See also_ Aberration

Logarithms, V. 96, 97 _n_

Long inequalities, XI. 243

Longitude (celestial), II. =33=, 39, 42, 43; III. 63; IV. 87; VII. 139

Longitude (terrestrial), III. 68; VI. =127=, 133; VII. 150; X. 197,
216, =226=

Longitudes, Bureau des, XI. 238

Lunar distances, III. 68 _n_

Lunar eclipses. _See_ Eclipses

Lunar equation, XIII. 282

Lunar theory, II. =48=, 51; V. 111; VII. 145; VIII. 156; IX. =184=,
192; X. =226=; XI. =228=, 230, 231, =233=, =234=, =240=, =241=,
242, 248; XIII. 282, =286=, =287=, 288, 290. _See also_ Moon,
motion of

Lunation, II. =40=. _See also_ Month, synodic

_Macchie Solari_ (of Galilei), VI. =124=, 125

Magellanic clouds, XIII. 307

Magnetism, VII. 150; XIII. 276, =298=

_Magnitudes and Distances of the Sun and Moon_ (of Aristarchus), II. 32

Magnitudes of stars, II. 42; XII. 266; XII. 280, 316. _See also_
Stars, brightness of

Mars, I. 14-16; II. 25, 26, 30, 51; III. 68; IV. 81, 87; V. 108; VI.
129; VII. 136 _n_, 139-142, 144, 145; VIII. 154, 161; IX. 181, 183,
185; X. 223, 227; XI. 235, 245; XII. 267; XIII. 281, 282, 284, 294,
295, =297=. _See also_ the following headings

Mars, canals of, XIII. 297

Mars, mass of, XI. 248

Mars, opposition of, VIII. =161=; XIII. =281=, 284, 297

Mars, rotation of, VIII. 160; XIII. 295, 297

Mars, satellites of, XIII. 295

Mass, IX. =180=, 181, 185

Mass of the earth, sun, Venus.... _See_ Earth, Sun, Venus ... mass of

_Mécanique Analytique_ (of Lagrange), XI. 237

_Mécanique Celeste_ (of Laplace), XI. =238=, 241, 247, 249, 250;
XIII. 292

Medicean Planets. _See_ Jupiter, satellites of

Meraga, III. 62