ASTRONOMY 
 
ASTRONOMY 
 
 BY 
 
 GEORGE F. CHAMBERS, F.R.A.S. 
 
 Of the Inner Temple, Barrister-at-Law 
 
 AUTHOR OF " A HANDBOOK OF ASTRONOMY," " THE STORY 
 OF THE COMETS," AND OTHER WORKS 
 
 WITH 358 ILLUSTRATIONS, INCLUDING 8 COLOURED PLATES 
 
 Gold Medal of.th - R.iya- 
 A str^nont -V* ;/ Societv 
 
 NEW YORK 
 
 D. VAN NOSTRAND COMPANY 
 TWENTY-FIVE PARK PLACE 
 
PRINTED IN GREAT BRITAIN 
 
 
PREFACE. 
 
 THIS volume is not a formal treatise on Astronomy, nor is it 
 a mere educational text-book ; but the idea which underlies 
 it may be realised from the following considerations. An 
 extended experience as an astronomical writer, and likewise 
 lecturer on the science, coupled with much intercommunica- 
 tion with many of its votaries in divers walks of life and 
 places, including colonies and foreign countries, has led me 
 to notice the remarkable spread of late years all over the 
 world of a taste for Astronomy. Some recent eclipses of 
 the Sun, and especially some recent comets, have had a good 
 deal to do with this, especially Halley's Comet of 1910. I 
 have often been struck by the frequent requests for informa- 
 tion on astronomical topics from all sorts of people, the 
 majority of whom, I fancy, would have resented a suggestion 
 that they should sit down and seriously study text-books on 
 the subject. These are the people whom I want to get hold of 
 through this volume. 
 
 There is nothing profound or inconveniently deep in it, 
 but it just gives a popular outline of leading facts, which 
 may be easily grasped by any fairly educated person who is 
 only able, or disposed, to give a limited amount of time or 
 thought to the matter, but who may happen to possess a 
 small telescope of, say, two or three inches aperture, or even 
 a good opera-glass. My endeavour has been to deal descrip- 
 
 285716 
 
VI PREFACE, 
 
 tively with some of the more ordinary sights of the Heavens, 
 the examination of many of which can be carried out with 
 the class of instrument just mentioned. Mathematical and 
 theoretical matters and speculations have been kept entirely 
 in the background. 
 
 It will appear, I hope, from the foregoing statement that 
 my idea has been to direct the reader's attention to what 
 may be called every-day topics, and to give in a handy form 
 information on such phenomena as are constantly brought 
 under the notice of people in general without exactly being 
 sought for by them. I want the reader to be able to answer 
 such questions as, " What is the meaning of the term Sun- 
 spot?" "What is the name of that bright star, or is it a 
 planet, which I see in the west every evening ? " " Is there 
 any difference between an eclipse of the Sun and an eclipse 
 of the Moon?" "Was Sir George Cornwall Lewis right 
 when he stigmatised Astronomy as a science of 'pure 
 curiosity '? " 
 
 Such questions as these, and others much more shallow, 
 have often been addressed to me, and I want to provide 
 people who possess only a smattering of scientific knowledge 
 with the means of answering some of these questions which 
 frequently crop up when some noteworthy astronomical event 
 or discovery gets mentioned in the newspapers or is talked 
 about. It will be seen, I think, that whilst my aims are 
 modest, I have endeavoured to provide materials for sensible 
 and exact knowledge, truly scientific and correct, yet not 
 needing too severe a demand on the time or mental powers 
 of those who patronise the book. 
 
 The illustrations have been obtained from many sources, 
 and, whilst it may be said of some of them that they are not 
 new, or only reproduce old ideas in new form, yet I have 
 endeavoured as far as possible to be chary in the insertion 
 
PREFACE. vil 
 
 of such, being desirous of providing my readers with pictures 
 which are not in general circulation or accessible to the 
 reading public. This really means that I have ransacked the 
 publications of various scientific societies, European and 
 American, for illustrations. America has been a rich field 
 for this purpose. 
 
 I have to thank Mr. H. F. Bushell, of the Gresham School, 
 Holt, Norfolk, for kindly reading the proof-sheets, but my 
 special thanks are due to friends too numerous to mention all 
 by name, who have provided me with drawings and photo- 
 graphs, without which it would have been impossible to 
 produce this, the most copiously illustrated book on Astro- 
 nomy which, I should suppose, has ever been published. 
 There are, however, a few names which stand out more 
 conspicuously than others, and which must receive special 
 mention. In such a list I must include the following : Pro- 
 fessor E. E. Barnard, of the Yerkes Observatory, Williams- 
 town ; Professor W. H. Pickering, of the Harvard College 
 Observatory, an institution to which Astronomy owes more 
 than can be expressed ; the Councils of the Royal Astrono- 
 mical Society and of the British Astronomical Association ; 
 and several private friends, under which head there must be 
 included Mr. E. M. Antoniadi, Mr. E. H. Barlow, Mr. S. Bolton, 
 Rev. A. L. Cortie, S.J.,Mr. W. F. Denning, Mr. W. B. Gibbs, 
 Mr. F. W. Longbottom, Admiral Moore, Rev. T. E. R. Phillips, 
 Mr. W. E. Wilson, Mr. H. E. Wood, together with Messrs. 
 Cooke & Sons and Sir H. Grubb. 
 
AN attentive, or even a cursory, perusal of this book will 
 give the go-by to the idea that astronomy is a science of " pure 
 curiosity." On the contrary, it has a great deal to recommend 
 it even in this utilitarian age, for the navigation of the high 
 waters of the world, and the daily disposal of our time by all of 
 us by the agency of clocks and watches, depend upon the 
 practical application of astronomy to the concerns of daily life. 
 But over and above all this it is a science which points un- 
 mistakeably to the Universe having been created, and being 
 still maintained, by a Divine Hand which controls everybody 
 and everything around us. It was no poetical fancy which 
 inspired Young in his Night Thoughts to write the significant 
 words " An undevout astronomer is mad." 
 
 G. F. C. 
 Lethen Grange, 
 Sydenham. 
 
CONTENTS. 
 
 PREFACE . . . . . . pp. v-vii 
 
 CONTENTS . . .., . ... . . ix-xiv 
 
 LIST OF ILLUSTRATIONS . . . . xv-xxiii 
 
 THE GREEK ALPHABET . ... . . xxiv 
 
 CHAPTER I. 
 INTRODUCTION. 
 
 The scope of the Science of Astronomy. Its modern developement 
 The other sciences which come in contact with it. The resulting necessity 
 of keeping the treatment of the science within defined limits. The different 
 divisions of pure astronomy. Mathematical Astronomy. Lord Grim- 
 thorpe's book, " Astronomy without Mathematics." Theoretical As- 
 tronomy. Descriptive, or Visual Astronomy. Practical Astronomy. 
 Amateurs may dispense with knowledge of mathematics altogether and 
 of the theory of telescopes and optics in part. The modern application of 
 the spectroscope . . . . . < . . pp. 1-4 
 
 CHAPTER II. 
 THE SUN. 
 
 Important position occupied by the Sun. Its general appearance. Its 
 mottled surface. "Granulations" probably the best word to describe it. 
 Spots on the Sun. Their periodicity. General description of them. 
 Peculiarities of spots. Period of the Sun's rotation. The Photosphere. 
 Distribution of the spots in latitude. Discovery of the periodicity of 
 the spots. Aurora. Terrestrial magnetism. Sun-spots and terrestrial 
 weather. Possible influence of some of the planets on Sun-spots. 
 Wilson's theory respecting them. Vortex movements on the Sun. Facula. 
 Apparent movements of spots at different seasons of the year. Notable 
 large spots. Light- and-heat- giving powers of the Sun. The Krakatoa 
 sunsets. ......... pp. 5-25 
 
X CONTENTS. 
 
 CHAPTER III. 
 THE MOON. 
 
 Next after the Sun in popular interest. How soon visible after being 
 new. Its phases. Its movement through the heavens. General physical 
 aspects. Its mountains. The walled plains. The rills. Mountain 
 chains. Isolated peaks. Signs of volcanic action. Resemblance be- 
 tween lunar and terrestrial volcanoes. Names applied to the principal 
 mountains. The so-called seas on the Moon. General appearance of 
 a crater. Changes in their appearance owing to the Moon's axial rotation. 
 The motions of the Moon very complex. The Librations. -The Harvest 
 Moon. The Hunter's Moon. Brightness of the Moon compared with the 
 Sun. Supposed influence of the Moon on the weather. Other influences 
 ascribed to the Moon. The " New Moon in the Old Moon's Arms." 
 Influence of the Moon on clouds. Influence of Moonlight on human 
 beings, a fallacy. Some statistics ..... pp. 26-40 
 
 CHAPTER IV. 
 
 THE TIDES. 
 
 The tides matter of interest to the inhabitants of maritime countries. 
 Influence of the Sun and Moon in causing them. Details of this influence. 
 That of the Moon greatly preponderates. Spring Tides. Neap Tides. 
 Daily differences. Range of the tide. " Establishment of the Port." 
 "Priming" and "lagging" of the tides. Equinoctial tides. Tides at 
 the solstices. Tidal irregularities of various kinds. In and around 
 Great Britain. Amongst the South Sea Islands. Influence of the baro- 
 meter. Journey of the tidal wave round the Earth. The " Bore." 
 
 pp. 41-54 
 
 CHAPTER V. 
 THE PLANETS GENERALLY. 
 
 What the planets are. May be conveniently divided into two groups. 
 The Inferior Planets. The Superior Planets. The Minor Planets. 
 Certain planets have satellites. The purpose served by them. Certain 
 planets have phases. The planets in Conjunction. The planets in 
 Opposition. Transits across the Sun. Characteristics common to all 
 the planets. Statement of these by Hind. Kepler's Three Laws. Sir J. 
 HerscheVs statement. Conjunction of two planets. Instances of this. 
 Various discarded planetary systems. Suggested I ntr a- Mercurial and 
 Trans- Neptunian planets. . pp. 55-66 
 
CONTENTS. XI 
 
 CHAPTER VI. 
 
 THE MOST INTERESTING AND FAMILIAR 
 PLANETS. 
 
 A classification of the planets, Mercury. Difficult to observe. 
 Spots. Phases. Schiaparelli's observations. Axial rotation. Sta- 
 tistics. How to find Mercury or Venus. Venus. Movements resem- 
 ble those of Mercury. Physical features. Possible mountains. At- 
 mosphere. A lleged satellite. Phases. Galileo's anagram. Statistics. 
 Mars. The Earth's nearest neighbour. Celebrated for its colour. 
 Subject to a slight phase. This planet very accessible for observation. 
 Its apparent movements. Physical appearance. Much controversy as 
 to this. Polar snows. Spots. Markings very permanent. Its colour. 
 Satellites. Statistics. Jupiter. Easy of observations. The largest 
 planet. Belts. Spots. Jovian spots and Sun-spots. Satellites. 
 Large ones easily found and followed. Small ones very difficult. Pheno- 
 mena. Velocity of light. Statistics. Saturn. Its rings. General 
 description of them. How designated. Changes in the appearance of 
 the rings from time to time. Some details respecting them. The ball. 
 The satellites as tests for telescopes. Statistics. . . pp. 67-97 
 
 CHAPTER VII. 
 THE LESS KNOWN PLANETS. 
 
 The planets of this chapter of little interest to the amateur. History of 
 the discovery of Uranus. Difficulties as to its orbit. Suspicions of the 
 orbit being disturbed by another planet. The search for it. The re- 
 searches of Adams and Leverrier. The discovery of Neptune. Brief 
 description of the planet. 7/s one satellite. TheMinor Planets. First or- 
 ganised search for them. Early discoveries. Recent discoveries facilitated 
 by photography. The planets now very numerous. And few of them of 
 any interest. Their fantastic names. Some particulars of the first 
 four. Summary respecting their orbits . . . pp. 98-112 
 
 CHAPTER VIII. 
 ECLIPSES. 
 
 The principles of eclipses. Other kindred phenomena. Two anec- 
 dotes. The difference between eclipses of the Sun and of the Moon. Total 
 eclipses. Partial eclipses. Annual number of eclipses. The Saros. 
 Method of using the Saros. Eclipses of the Sun considered. The accom- 
 paniments of a large partial eclipse of the Sun. Of a total eclipse. The 
 terror of savages. Instances of this.. The darkness. The fall of tempera- 
 
Xll CONTENTS. 
 
 ture. The red flames. Baily's Beads. The Corona. Details relating 
 thereto. The Moon's shadow. Shadow-bands. Bushes of light. The 
 Corona, a solar appendage. Connection between its shape and spots on 
 the Sun. Coming eclipses. Eclipse expeditions. Eclipses of the 
 Moon. The Moon when totally eclipsed. Anecdote of Columbus. In- 
 cident in the South African War. Transits of Mercury and Venus. 
 Method of measuring the Sun's distance. Transits and eclipses of the 
 satellites of Jupiter. Occultation of planets and stars by the Moon. 
 Occupation of stars and planets by planets . . . pp. 113-143 
 
 CHAPTER IX. 
 COMETS, 
 
 Always objects of popular interest. Very numerous. Telescopic comets. 
 Great comets visible to the naked eye. Changes in the appearance of 
 a comet after its first discovery. Often easily mistaken for a nebula. 
 Usual changes exhibited by a telescopic comet. Become visible as they 
 approach the Sun. What is a comet's tail ? Where does it come from ? 
 Why do some comets have tails and not others ? These questions difficult 
 to answer. Sir J . Herschel's opinion. General account of tails. Some 
 tails probably cylindrical. Bredichen's Types of tails. The '"Light- 
 pressure" theory. Orbits of comets. Periodical comets. Celebrated 
 comets. Some statistics .... pp. 144171 
 
 CHAPTER X. 
 SHOOTING-STARS. 
 
 Various classes of luminous meteors. Shooting- stars. Fireballs. 
 Aerolites. Radiant points of shooting-stars. Account of the most im- 
 portant showers. Position in the heavens of some of the chief radiant 
 points. Historical allusions. Celebrated great showers. Fireballs. 
 Their general resemblance to one another. Remarkable fireballs described 
 by Webb and Brodie. Their sizes, distances, and movements. Compu- 
 tation of their paths. Connection between meteors and comets. Shooting- 
 stars, fireballs, and aerolites all of the same nature. Circumstances attend- 
 ing the fall of aerolites pp. 172-190 
 
 CHAPTER XI. 
 THE STARS. 
 
 The apparent movement of the stars on a starlight night. The stars 
 in magnitudes. Diurnal movement of the Earth. Its consequences. 
 The stars visible vary with the latitude. The expression " fixed 
 
CONTENTS. xiii 
 
 Stars that art visible to the naked eye. The identification of the stars, 
 Bayer's system of lettering stars. Flamsteed's numbers. Sir J. 
 HerscheVs striking remarks. Total number of naked- eye stars. Amount 
 of star-light. Twinkling. Double stars. Binary stars. Coloured 
 stars. Complementary colours. Triple and multiple stars. Variable 
 stars. Notable variable stars. Temporary stars. Tycho Brake's Star. 
 Recent temporary stars ...... pp. 191-225 
 
 CHAPTER XII. 
 GROUPS OF STARS AND NEBULAE. 
 
 Stars in groups classified. Irregular groups. Clusters of stars more 
 or less compressed. Nebulce. Classification of nebulce. Annular 
 nebula. Elliptic nebulce. Spiral nebulce. Planetary nebula. 
 Nebulous stars. Large nebulce of irregular form. Exemplification of 
 these classes named. Distribution of nebulce and clusters over the heavens. 
 The Milky Way. Brief description of its position. Its historic names. 
 
 pp. 226-243 
 
 CHAPTER XIII. 
 THE CONSTELLATIONS. 
 
 The subject one of great interest. The best way of learning their posi- 
 tions. The effects of the diurnal movement. Star-atlases and plani- 
 spheres. The constellations best learnt in the open air. List of stars of 
 the ist magnitude. Standard stars of the first 4 magnitudes. Alignment 
 of stars. Origin of the constellations. Modern additions. A hasty 
 survey of the Northern Hemisphere . . . . pp. 244-255 
 
 CHAPTER XIV, 
 TELESCOPES. 
 
 Telescopes are of two kinds. Reflectors, Refractors. Various kinds of 
 reflectors. Brief description of each. Principle of a refractor. Spherical 
 aberration. Chromatic aberration. The opera-glass. Stands for tele- 
 scopes. Importance of a good stand. Equatorial stands. Advantages of 
 an equatorial mounting. Accessories to a telescope. Driving-clock. 
 Sidereal-clock. The housing of a telescope. Advantages of an observa- 
 tory. Detailed description of how to bmld one . . . pp. 256-282 
 
XIV CONTENTS. 
 
 CHAPTER XV. 
 TIME AND ITS MEASUREMENT, 
 
 Years. Months. Weeks. Days. Hours. The Sidereal Year. The 
 Mean Solar Year. The Anomalistic Year. Hipparchus. The Calendar 
 and the reforms it has undergone. By Julius Casar. By Pope Gregory 
 XIII. His Calendar adopted by England. But not by Russia. ' ' Old 
 Style." "New Style." The Lunar Month. The week. Quotation 
 from Laplace. Savages count time by " Moons." Divisions of the Day. 
 The 24-hour Day. a.m. and p.m. Railway time. The " Prime 
 Meridian." Greenwich chosen for this. Standard time. Usage of 
 different nations. Where does the day begin ? The Transit Instrument 
 and how to use it for obtaining the time .... pp. 283-300 
 
 CHAPTER XVI. 
 THE SPECTROSCOPE ASTRONOMICALLY. 
 
 What is a spectrum ? The decomposition of sunlight. Brief history 
 of the application of prisms to sunlight. Labours of Grimaldi. Of Sir 
 7. Newton. Of Wollaston. Of Fraiinhofer. The lines in the spectrum 
 named by him. And after him. Some details as to these. Their inter- 
 pretation. The labours of Huggins and others. Application of the 
 spectroscope to celestial objects. Secchi's star types. Motions of the stars 
 as ascertained by the spectroscope ... . pp. 301-309 
 
 CHAPTER XVII. 
 
 TABLE OF THE CONSTELLATIONS, WITH A 
 BRIEF DESCRIPTIVE ACCOUNT OF EACH pp. 310-322 
 
 APPENDIX I. 
 
 STATISTICS RESPECTING THE PLANETS AND 
 THEIR SATELLITES pp. 323-324 
 
 APPENDIX II. 
 
 CATALOGUE OF CELESTIAL OBJECTS EASY FOR 
 SMALL TELESCOPES pp. 325-328 
 
 INDEX . pp. 329-335 
 
LIST OF ILLUSTRATIONS. 
 
 COLOURED PLATES. 
 
 1C. 
 
 i THE PLANET SATURN (Boltori) . . PLATE I Frontispiece 
 
 PLATE PAGE 
 
 iooa MARS (Boltori) . . ., . . . XXIXA . 80 
 
 108 JUPITER (Bolton) . XXXII . 84 
 
 141, 1410 PROMINENCES OH THE SUN . . XXXVII . 114 
 
 162 TOTAL ECLIPSE OF THE MOON (Tempel) . XLVIII . 138 
 
 258 DAYLIGHT METEOR (/. Nasmyth) . . LXXXIII . 188 
 
 262 COLOURED STARS LXXXIV . 208 
 
 263 COLOURED STARS ..... LXXXV . 210 
 
 BLACK-AND-WHITE ILLUSTRATIONS. 
 
 2. East Indian Coral ....... 8 
 
 3. Spot on the Sun, Aug. 14, 1868 n 
 
 4. A Typical Sun-spot (S. P. Langley) ... II . 12 
 
 5. The Disc of the Sun, showing Spots, Oct. 22, 
 
 1905 (Barlow) .... Ill . i2a 
 
 6. The Disc of the Sun, showing Spots, July 31, 
 
 1906 (Barlow) ... ,, i2a 
 
 7. The Disc of the Sun, showing Spots, Feb. 7, 
 
 1907 (Barlow) ...... ,, i2a 
 
 8. The Disc of the Sun, showing Spots, May 6, 
 
 1907 (Barlow) ...... ,, iza 
 
 9. The Disc of the Sun, showing Spots, July 15, 
 
 1907 (Barlow) IV . 126 
 
 10. The Disc of the Sun, showing Spots, May 4, 
 
 1908 (Barlow) ,, . I2& 
 
 11. The Disc of the Sun, showing Spots, Aug. 3, 
 
 1908 (Barlow) . . . . . I2& 
 
 12. The Disc of the Sun, showing Spots, Sept. 2, 
 
 1908 (Barlow) ,, . 126 
 
 13. The Great Sun-spot of 1865 on Oct. 14 
 
 (Hewlett) ..... . V . 13 
 
 14. The Great Sun-spot of 1865 on Oct. 16 
 
 (Howlett} . 13 
 
XVI 
 
 LIST OP ILLUSTRATIONS. 
 
 FIG. PLATE PAGE 
 
 15. The Great Sun-spot of 1865 disappearing on 
 
 Nov. 3 (Howlett) . . . . " . . V . 13 
 
 16. Remarkable Sun-spot, Oct. 20, 1905 (Bar- 
 
 low) . . VI . 14 
 
 17. Granulations and Faculas, Nov. 16, 1905 
 
 (Barlow) ....... ,, . 14 
 
 18. Large Compact Sun-spot, June 22, 1889 
 
 (McK.) 14 
 
 19-26. Sun-spots in 1882 at various dates 
 
 (Cortie) VII . 15 
 
 2730. The Great Sun-spot of Feb. 1905 at 
 
 various dates ...... VIII . 18 
 
 31-35. Changes in Sun-spots as they approach 
 
 the Sun's Limb : exemplified in May 
 
 1906 (Barlow) . . . . . . IX . 19 
 
 36. Facula? on the Sun, June 28, 1884 (Cortie) . . X . 22 
 
 37. Faculoe on the Sun, Nov. 28, 1884 (Cortie) . . ,, . 22 
 
 38. The Red Sunsets in 1883 XI . 23 
 
 39. Map of the Moon ...... XII . 26 
 
 40. The Phases of the Moon XIII . 27 
 
 41. The Moon's Surface in Model (Nasmyth) . . XIV . 28 
 
 42. The Lunar Mountain Copernicus (W. H. 
 
 Pickering) XV . 29 
 
 43. The Mare Crisium on the Moon (Weinek) . . XVI . 30 
 4445. The Lunar Mountain " Archimedes," 
 
 1888 (Weinek) . . . . . XVII . 31 
 
 46-51. Mountains on the Moon (Stuyvaert) . . XVIII . 34 
 
 52-57. Mountains on the Moon (Stuyvaert) . . XIX . 35 
 
 58-63. Mountains on the Moon (Stuyvaert) . . XX . 36 
 
 64-67. Mountains on the Moon (Stuyvaert) . . XXI . 37 
 
 68. The Earth-lit New Moon. Feb. 17, 1907 . . XXII . 52 
 
 69. The "Bore" on the River Tsien-Tang- 
 
 Kiang, China XXIII . 53 
 
 70. The Inclination of the Axes of the Planets . . 59 
 
 71. Diagram illustrating Kepler's Second Law . . ., .60 
 
 72. Conjunction of Venus and Saturn, 1845 . . ... . 63 
 
 73. Conjunction of Mars and the Moon, 1909 . . . . 64 
 
 74. Mercury (Guiot) ........ 69 
 
 75. Mercury, Nov. 5, 1881 (Denning) . . . XXIV . 72 
 
 76. Mercury, Nov. 6, 1881 (Denning) . . ,, .72 
 
 77. Mercury, Nov. 8, 1881 (Denning) . . . .72 
 
 78. The Various Phases of Venus . . . XXV . 73 
 
 79. Venus near its Inferior Conjunction (Schro- 
 
 ter) , . . .73 
 
 80. Venus, Dec. 23, 1885 (Lihou) 73 
 
 81. Venus, March 22, 1 881 (Denning) . . . XXVI . 76 
 
 82. Venus, March 26, 1881 (Denning) . . . ,, . 76 
 
 83. Venus, March 28, 1881 (Denning) . . . -76 
 
 84. Venus, March 30, 1881 (Denning) ,, 76 
 
LIST OF ILLUSTRATIONS. 
 
 FIG. 
 
 85. Venus, March 31, 1881 (Denning) 
 
 86. Venus, April 5, 1881 (Denning) 
 
 87. Mars, May 14, 1903 (IV. F. Gale) 
 
 88. Mars, April 14, 1903 (P. B. Molesworth) 
 
 89. Mars, April 19, 1903 (T. E. R. Phillips) 
 go. Mars, April 21, 1903 (P. B. Molesworth) 
 
 91. Mars, May 21, 1903 (R. Killip) 
 
 92. Mars, April 8, 1903 (H. Carder) 
 
 93. Mars, May 12, 1903 (T. E. R. Phillips) 
 
 94. Mars, April 30, 1903 (P. B. Molesworth) 
 
 95. Mars, March 31, 1903 (E. M. Antoniadi) 
 
 96. Mars, March 31, 1903 (E. A. L. Attkins) 
 
 97. Mars, March 31, 1903 (W. J. Hall) 
 
 98. Mars, May 7, 1903 (T. E. R. Phillips) 
 
 99. Mars, Sept. 20, 1909 (Antoniadi) 
 
 100. Mars, Nov. 5, 1909 (Antoniadi) 
 
 101. Mars on Mercator's Projection (Antoniadi) 
 
 102. Jupiter, Sept. 20, 1879 . 
 
 103. Jupiter, Oct. 15, 1879 
 
 104. Jupiter, Oct. 14, 1882 
 
 105. Jupiter, Dec. 24, 1882 . 
 
 106. Jupiter, Nov. 7, 1884 
 
 107. Jupiter, Feb. 27, 1885 . 
 
 109. Jupiter's Red Spot, Nov. 19, 1880 (Denning) 
 
 no. Jupiter's Red Spot, Sept. 28, 1881 (Denning) 
 
 in. Jupiter's Red Spot, Dec. 7, 1881 (Denning) 
 
 112. Jupiter's Red Spot, Oct. 30, 1882 (Denning) 
 
 113. Jupiter's RedSpot, Oct. 15, 1883 (Denning) 
 
 114. Jupiter's Red Spot, Feb. 6, 1884 (Denning) 
 
 115. Jupiter's Red Spot, Feb. 25, 1885 (Denning) 
 
 116. Jupiter's Red Spot, May 9, 1885 (Denning) 
 117-128. Jupiter with its Satellites, Aug. 21, 
 
 1867 (Tempel) 
 
 129. Jupiter's Red Spot in the i7th Century 
 
 130. Saturn, Jan. 5, 1862 (Wray) . 
 
 131. Saturn, Feb. to March 1884 (Henry) 
 
 132. Saturn, Feb. 1887 (Terby) 
 
 133. Saturn, March 18, 1887 (Elger) 
 
 134. Saturn, July 30, 1899 (Antoniadi) 
 
 135. Saturn, Jan. 27, 1912 (Phillips) 
 
 136. Irregularities in the Crape Ring, March 21, 
 
 1887 (Elger) 
 
 137. Irregularities in the Crape Ring, March 27, 
 
 1887 (Elger) 
 
 138. Saturn, Feb. 7, 1890 
 
 139. How Minor Planets are recognised as such 
 
 140. The Orbits of Eros, Mars, and the Earth 
 
 142. Solar Eclipsesvisible in England, 1891-1922 
 
 143. Total Eclipse of the Sun, Aug. 7, 1869 
 
 b 
 
 PLATE 
 
 PAGE 
 
 . XXVI 
 
 . 76 
 
 ,, 
 
 . 76 
 
 XXVII 
 
 77 
 
 >orth) . 
 
 77 
 
 lips) . 
 
 77 
 
 'orth) . 
 
 77 
 
 ,, 
 
 77 
 
 
 
 77 
 
 ips) . XXVIII 
 
 . 78 
 
 iorth) . 
 
 . 78 
 
 liadi) . ,, 
 
 . 78 
 
 kins) . ,, 
 
 . 78 
 
 . 
 
 . 78 
 
 Os) . 
 
 . 78 
 
 . XXIX 
 
 79 
 
 
 79 
 
 oniadi) XXX 
 
 . 82 
 
 XXXI 
 
 83 
 
 
 
 83 
 
 . 
 
 . 83 
 
 
 
 83 
 
 . 
 
 83 
 
 
 
 83 
 
 enning) XXXIII 
 
 86 
 
 enning) , 
 
 86 
 
 enning) , 
 
 . 86 
 
 enning) , 
 
 . 86 
 
 enning) , 
 
 . 86 
 
 enning) , 
 
 86 
 
 enning) , 
 
 86 
 
 enning) , 
 
 86 
 
 Ug. 21, 
 
 
 XXXIV 
 
 . 87 
 
 tury . 
 
 . 87 
 
 XXXV 
 
 . 92 
 
 ) 
 
 92 
 
 
 92 
 
 XXXVI 
 
 93 
 
 
 
 93 
 
 . 
 
 93 
 
 rch 21, 
 
 93 
 
 rch 27, 
 
 
 . 
 
 93 
 
 . 
 
 95 
 
 as such 
 
 . 109 
 
 Earth . 
 
 . in 
 
 1-1922 XXXVIII 
 ]6g . XXXIX 
 
 . 116 
 . 117 
 
LIST OF ILLUSTRATIONS. 
 
 MO. PLATE FACE 
 
 144. The Solar Corona, July 29, 1878 (Murphy) . XL . 120 
 
 145. The Solar Corona, Aug. 29, 1886 (Harvard 
 
 Annals, xviii.) ...... XLI . 121 
 
 146. The Solar Corona, Dec. 22, 1889 (Perry) 121 
 
 147. The Solar Corona, 1898 (C. M. Smith) . . XLII . 124 
 
 148. The Solar Corona, May 28, 1900 . . . XLIII . 125 
 
 149. The Eclipse of the Sun, April 17, 1912, at 
 
 11.46 G.M.T. (Barlow) .... XLIV . 136 
 
 150. The Eclipse of the Sun, April 17, 1912, at 
 
 12.5 G.M.T. (Barlow) ... ,, 136 
 
 151. The Eclipse of the Sun, April 17, 1912, at 
 
 12. 1 1 G.M.T. (Barlow) ... ,, 136 
 
 152. Total Eclipse of the Moon, Jan. 28, 1888 . . XLV . 136*3 
 
 153. Total Eclipse of the Moon, Jan. 28, 1888 ,, 136(3 
 
 154. Total Eclipse of the Moon, Jan. 28, 1888 . . XLVI . 1366 
 
 155. Total Eclipse of the Moon, Jan. 28, 1888 . . ,, . 1366 
 
 156. Total Eclipse of the Moon, Jan. 28, 1888 . . XLVII . 137 
 157-160. Occultation of Jupiter by the Moon, 
 
 Aug. 12, 1892 (W. H. Pickering] . . ,, .137 
 161. Diagram of the Corona, Aug. 8, 1896 
 
 (E. J. Stone] .... . 137 
 
 163. Phases of the Transit of an Inferior Planet . . . 141 
 
 164. Brooks's Comet of 1898 (x.) on Nov. ii .... 145 
 
 165. Brooks's Comet of 1898 (x.) on Nov. 15 . . . . 145 
 
 166. Diagram to show Recognition of a 
 
 Comet . . . . . . . . . 147 
 
 167. Telescopic Comet without a Nucleus .... 149 
 
 168. Telescopic Comet with a Nucleus . . . . .1/19 
 
 169. Head of Brooks's Comet, 1884 (i.), Jan. 13 
 
 (Thollon] XLIX . 150 
 
 170. Head of Brooks's Comet, 1884 (i.), Jan. 19 
 
 (Thollon] ,, .150 
 
 171. Encke's Comet, Sept. 22, 1848 (Smyth) . . L . 151 
 
 172. Medal of Comet struck in 1680 . . >. * . 153 
 
 173. Naked-eye View of Halley's Comet in 1910 
 
 (Leon) LI . 154 
 
 174. Curious Aspect of Halley's Comet, June 8, 
 
 1910 (Leon) ...... LII . 155 
 
 175. The Great Comet of 1 81 1 .... LIII . 156 
 
 176. The Great Comet of 1843 on March 17 . . LIV . 157 
 
 177. Donati's Comet, Oct. 5, 1858 (Pape) . . LV . 158 
 
 178. The' Comet of 1860 (iii.), June 26 (Cap- 
 
 pelletti and Rosa] . . . . . LVI . 159 
 
 179. The Comet of 1860 (iii.), June 28 (Cap- 
 
 pelletti and Rosa] . 159 
 
 180. The Comet of 1860 (iii.), June 30 (Cap- 
 
 pelletti and Rosa] ,, . 159 
 
 181. The Comet of 1860 (iii.), July i (Cap- 
 
 pelletti and Rosa] . 159 
 
LIST OF ILLUSTRATIONS. 
 
 FIG. 
 
 182. The Comet of 1860 (iii.), July 6 (Cap- 
 pelletti and Rosa) 
 183. The Comet of 1860 (iii.), July 8 (Cap 
 pelletti and Rosa) 
 184. The Comet Families of the Planets . 
 185. Halley's Comet, May i, 1910 . 
 186. Halley's Comet, 1910, on May 5 (More- 
 house) ...... 
 187. Halley's Comet, 1910, on May 13 (More- 
 house) ...... 
 188. Halley's Comet, 1910, on May 25 (More- 
 house) ...... 
 
 PLATE 
 
 . LVI 
 
 ! LVII 
 . LVIII 
 
 xix 
 
 PAGE 
 
 159 
 
 159 
 159 
 . 162 
 
 I6 3 
 I6 3 
 163 
 
 189. Halley's Comet, 1910, on May 29 (More- 
 house) ...... 
 190. Halley's Comet, 1910, on May 30 (More- 
 
 .' " 
 
 . I6 3 
 16^5 
 
 191. Halley's Comet, 1910, on June 5 (More- 
 house) ...... 
 192. Path of Halley's Comet, April 1910 
 193. The Warner Prize Medal 
 194. The Great Comet of 1744 
 195. Coggia's Comet, 1874, on July 13 (F.Brodie) 
 196. The Great Comet of 1882 (Charlois) 
 197. The Great Comet of 1882 on Nov. 7 
 198. The Great Comet of 1882 on Nov. 13 
 199. The Head and Nucleus of the Great Comet 
 of 1882 on Nov. 13 . 
 200. The Head and Nucleus of the Great Comet 
 
 
 
 LIX 
 LX 
 . LXI 
 
 . LXII 
 
 . I6 3 
 I6 3 
 . 164 
 165 
 
 . 1 66 
 . i66a 
 . 1666 
 . 1666 
 
 . i66c 
 . i66r 
 
 201. The Nucleus of the Great Comet of 1882 
 on Feb. i, 1883 . . . . 
 202. The Nucleus of the Great Comet of 1882 
 on Feb. 23, 1883 .... 
 
 . LXIII 
 
 . i66d 
 . i66d 
 
 203. The Nucleus of the Great Comet of 1882 
 on Feb. 27, 1883 .... 
 204. The Nucleus of the Great Comet of 1882 
 on March 3, 1883 .... 
 205. Swift's Comet of 1892 (i.) on March 30 
 206. Swift's Comet of 1892 (i.) on April 5 
 207. Swift's Comet of 1892 (i.) on April 6 
 208. Swift's Comet of 1892 (i.) on April 7 
 
 . LXIV 
 ! LXV 
 
 . 167 
 
 . 167 
 . 168 
 . 168 
 . 168 
 
 . 168 
 
 209. Swift's Comet of 1892 (i.) on April 14 
 210. Swift's Comet of 1892 (i.) on April 21 
 211. Swift's Comet of 1892 (i.) on April 22 
 212. Swift's Comet of 1892 (i.) on April 23 
 213. Rordame's Comet of 1893 (ii.) on July 8 
 (Hussey) ...... 
 214. Rordame's Comet of 1893 (ii.) on July 13 
 
 . LXVI 
 . LXVII 
 
 . i68a 
 . i68a 
 . 1680 
 . i68 
 
 . 1686 
 , 1686 
 
XX 
 
 LIST OF ILLUSTRATIONS. 
 
 
 
 FIG. 
 
 
 PLATE 
 
 PAGE 
 
 215. 
 
 Brooks's Comet of 1893 (iv.), Oct. 21 
 
 LXVIII 
 
 . i68c 
 
 216. 
 
 Brooks's Comet of 1893 (iv.), Oct. 22 
 
 f| 
 
 . i68c 
 
 217. 
 
 Borelly's Comet of 1903 (iv.), (R. J. 
 
 
 
 
 Wallace] ...... 
 
 . LXIX 
 
 . i68d 
 
 aiS. 
 
 Giacobini's Comet of 1906 (i.) on Dec. 29, 
 
 
 
 
 1905 (E. E. Barnard) .... 
 
 . LXX 
 
 . i68e 
 
 219. 
 
 Giacobini's Comet of 1906 (i.) on Dec. 29, 
 
 
 
 
 1905 (. E. Barnard) . . 
 
 . LXXI 
 
 . i68/ 
 
 220. 
 
 Giacobini's Comet of 1906 (i.) on Jan. 5, 
 
 
 
 
 1906 (E. E. Barnard) .... 
 
 
 i68/ 
 
 221. 
 
 Daniel's Comet of 1907 (iv.) on Aug. 18 
 
 " 
 
 
 
 (Kennedy) ..... 
 
 LXXII 
 
 169 
 
 222. 
 
 Morehouse's Comet of 1908 (iii.) on Oct. 15 
 
 
 
 
 (E. E. Barnard) 
 
 LXXIII 
 
 170 
 
 223. 
 
 Morehouse's Comet of 1908 (iii.) on Oct. 15 
 
 
 
 
 (Yerkes Observatory) .... 
 
 LXXIV 
 
 . i7oa 
 
 22 4 . 
 
 Morehouse's Comet of 1908 (iii.) on Nov. 15 
 
 
 
 
 ( Yerkes Observatory) .... 
 
 n 
 
 . i7oa 
 
 225. 
 
 Morehouse's Comet of 1908 (iii.) on Nov. 13 
 
 . LXXV 
 
 . 170^ 
 
 226. 
 
 Halley's Comet, 1910, on May 25 (Gingrich) 
 
 LXXVI 
 
 . 170^ 
 
 227. 
 
 Halley's Comet, 1910, on May 27 (Gingrich) 
 
 M 
 
 . i7oc 
 
 228. 
 
 Halley's Comet, 1910, on May 28 (Gingrich) 
 
 t| 
 
 . i7oc 
 
 229. 
 
 Halley's Comet, 1910, on June 2 (Gingrich) 
 
 >f 
 
 ' . 1700 
 
 230. 
 
 The Daylight Comet of 1911 (W. B. Gibbs) 
 
 LXXVII 
 
 . 170^ 
 
 231. 
 
 Brooks's Comet of 1911 on Sept. 21 (Long- 
 
 
 
 
 bottom) ...... 
 
 LXXVIII 
 
 I7i 
 
 232. 
 
 Brooks's Comet of 1911 on Sept. 24 (Long- 
 
 
 
 
 bottom) ...... 
 
 
 . 171 
 
 233- 
 
 A Meteor in Flight (E. E. Barnard) 
 
 LXXIX 
 
 . 172 
 
 234- 
 
 Fishing for Meteors (Longbottom) 
 
 LXXX 
 
 173 
 
 235- 
 
 Flight of Telescopic Meteors (Brooks) "* 
 
 . 
 
 173 
 
 2 3 6. 
 
 Meteor Radiant Point in Gemini 
 
 
 . 177 
 
 237- 
 
 Meteor Radiant Point in Leo . 
 
 LXXXI 
 
 . 178 
 
 238. 
 
 Meteor seen on Nov. 14, 1868, at New- 
 
 
 
 
 haven, Conn., U.S., at 1.15 a.m. . 
 
 LXXXII 
 
 . 179 
 
 239- 
 
 Meteor seen on Nov. 14, 1868, at New- 
 
 
 
 
 haven, Conn., U.S., at 1.19 a.m. . 
 
 it 
 
 . 179 
 
 240. 
 
 Meteor seen on Nov. 14, 1868, at New- 
 
 
 
 
 haven, Conn., U.S., at 1.30 a.m. . 
 
 () 
 
 179 
 
 241. 
 
 Meteor seen on Nov. 14, 1868, at New- 
 
 
 
 
 haven, Conn., U.S., at 1.39 a.m. . 
 
 M 
 
 179 
 
 242. 
 
 Meteor seen on Nov. 14, 1868, at Palisades, 
 
 
 
 
 N.Y., at 1.14 a.m 
 
 
 179 
 
 243- 
 
 Meteor seen on Nov. 14, 1868, at Palisades, 
 
 
 
 
 N.Y., at 1.18 a.m 
 
 ?> 
 
 . 179 
 
 244, 
 
 Meteor seen on Nov. 14, 1868, at Palisades, 
 
 
 
 
 N.Y., at i. 21 a.m. .... 
 
 |f 
 
 . 179 
 
 245^ 
 
 Meteor seen on Nov. 14, 1868, at Palisades, 
 
 
 
 
 N.Y., at 1.28 a.m. . . 
 
 ,, 
 
 . 179 
 
LIST OF ILLUSTRATIONS. 
 
 FIG. PLATE 
 
 246. Meteor seen on Nov. 14, 1868, at Haver- 
 
 ford, Pa LXXXII 
 
 247. Meteor seen on Nov. 14, 1868, at Williams- 
 
 town, Mass., at 1.15 a.m. ... 
 
 248. Fireball of Aug. 1 8, 1783 (first view) 
 
 249. Fireball of Aug. 18, 1783 (second view) . 
 
 250. Fireball of June 7, 1878 (Denning) . ' . 
 
 251. Fireball of Oct. 19, 1868 (Schmidt) . 
 
 252. Fireball of Oct. 19, 1877 (first effect) 
 
 253. Fireball of Oct. 19, 1877 (second effect) . 
 
 254. Successive Changes in a Fireball (three 
 
 views) ........ 
 
 255. Meteor of Nov. 12, 1861 (Webb) .... 
 
 256. Fireball observed in the Isle of Wight, 
 
 Feb. 22, 1909 (C. G. Brodie) .... 
 
 257. Orbit of the Leonids and of the Comet of 
 
 1866 (i.) 
 
 259. Apparent Changes in Stars rising and 
 
 setting ........ 
 
 260. An Apparent Double Star ..... 
 
 261. Diagram for plotting Measurements of 
 
 Double Stars 
 
 264. Light-curve of the Variable Star T Cassi- 
 
 opeiae ......... 
 
 265. Light-curve of the Variable Star S Cassi- 
 
 opeia . ..... 
 
 266. Light-curve of the Variable Star R Auriga3 
 
 267. Light-curve of the Variable Star R Ursa 
 
 Majoris ........ 
 
 268. Light-curve of the Variable Star T Ursae 
 
 Majoris ........ 
 
 269. Light-curve of the Variable Star S Ursae 
 
 Majoris ........ 
 
 270. Light-curve of the Variable Star S Bootis . 
 
 271. Light-curve of the Variable Star R Came- 
 
 lopardi ........ 
 
 272. Ligh t-curve of the Variable Star RDraconis 
 
 273. Light-curve of the Variable Star T Cephei 
 
 274. Light-curve of the Variable Star S Cephei 
 
 275. Light-curve of the Variable Star R Cassi- 
 
 opeiae ........ 
 
 276. Light-changes in Nova Persei, 1901 
 
 277. Tycho Brahe's Mural Quadrant .... 
 
 278. The Pleiades (Tempel) .... LXXXVI 
 279- Nebulas in the Pleiades (/. Roberts) . . LXXXVII 
 
 280. The Cluster 13 M. Herculis (W. E. Wilson) LXXXVIII 
 
 281. The Cluster u> Centauri .... LXXXIX 
 
 282. The Cluster 47 Toucani XC 
 
 283. The Cluster 2 M Aquarii (Sir /. Herschel) . . XCI 
 
 XXI 
 
 PAGE 
 179 
 179 
 
 179 
 179 
 179 
 
 179 
 1 80 
 180 
 
 181 
 182 
 
 183 
 
 187 
 
 193 
 205 
 
 207 
 213 
 
 213 
 213 
 
 213 
 215 
 
 215 
 215 
 
 215 
 217 
 217 
 217 
 
 217 
 219 
 
 221 
 226 
 227 
 228 
 229 
 230 
 231 
 
XX11 
 
 LIST OF ILLUSTRATIONS. 
 
 FIG. 
 284. 
 
 285. 
 286. 
 
 287. 
 288. 
 289. 
 
 The Cluster 5 M Libras (Sir J. Herschel) . 
 The Cluster 2 M Aquarii (Earl of Rosse) . 
 The Clusters 33 and 34 Ijl VI Persei 
 (Rambaut) ...... 
 The Great Nebula in Andromeda (Shepslowe) 
 The Spiral Nebula 51 M Can. Yen. (Smyth) 
 The Spiral Nebula 51 M Can. Yen. (Sir J. 
 Herschel) 
 
 PLATE 
 
 . XCI 
 
 . XCII 
 . XCIII 
 . XCIV 
 
 PAGE 
 
 . 231 
 . 231 
 
 . 232 
 
 . 232 
 
 . 2326 
 
 2326 
 
 290. 
 
 The Spiral Nebula in Ursa Major (Shepstowe) 
 
 . xcv 
 
 233 
 
 291. 
 
 The Nebula 4620 h Cygni (Barnard) 
 
 . XCVI 
 
 234 
 
 292. 
 
 The Nebulae 81 and 82 M Ursae Majoris 
 
 
 
 
 (/. Roberts) 
 
 . XCVII 
 
 235 
 
 293- 
 
 Planetary Nebula 97 M Ursge Majoris 
 
 
 
 
 (Sir J. Herschel) ' 
 
 . 
 
 235 
 
 294. 
 
 Planetary Nebula 97 M Ursa? Majoris (Earl 
 
 
 
 
 of Rosse) ...... 
 
 
 235 
 
 295- 
 
 The Great Nebula in Orion (Harvard) 
 
 'xcvhi 
 
 . 236 
 
 296. 
 
 The Great Nebula in Orion (W. E. Wilson) 
 
 . XCIX 
 
 . 237 
 
 297. 
 
 The Trapezium of Orion 
 
 . 
 
 237 
 
 298. 
 
 The Nebula surroundings Argus (C.E. Peek] 
 
 c 
 
 . 238 
 
 299. 
 
 The Nebula surrounding 17 Argus 
 
 CI 
 
 . 230 
 
 300. 
 
 The Nebula 17 M Clypei Sobieskii . 
 
 
 239 
 
 301. 
 
 The Dumb-bell Nebula in Vulpecula (low 
 
 
 
 
 power) ...... 
 
 CII 
 
 . 240 
 
 302. 
 
 The Dumb-bell Nebula in Vulpecula (en- 
 
 
 
 
 larged) 
 
 
 
 . 240 
 
 303. 
 
 The Dumb-bell Nebula in Vulpecula (Smyth) 
 
 . cm 
 
 . 24oa 
 
 304- 
 
 The Dumb-bell Nebula in Vulpecula (Earl 
 
 
 
 
 of Rosse) ...... 
 
 . 
 
 . 2400 
 
 305' 
 
 Nebulous Region of p Ophiuchi (E. E. 
 
 
 
 
 Barnard) ...... 
 
 . CIV 
 
 . 2406 
 
 306. 
 
 Nebulous Region of y Cygni (E. E. Barnard) 
 
 . 
 
 . 2406 
 
 307. 
 
 The Nebula 14 Itl V Cygni (Lick Obser- 
 
 
 
 
 vatory) ...... 
 
 . - cv 
 
 . 240C 
 
 308. 
 
 The " Trifid Nebula " in Sagittarius 
 
 . CVI 
 
 . 240^ 
 
 309- 
 
 The "Trifid Nebula " in Sagittarius 
 
 . CVII 
 
 . 240^ 
 
 310. 
 
 Stars in Cygnus (Henry) 
 
 . CVIII 
 
 . 2407 
 
 3*1- 
 
 The Nubecula Major .... 
 
 CIX 
 
 240.? 
 
 312. 
 
 The Nubecula Minor . 
 
 ex 
 
 . 2 40 h 
 
 3I3- 
 
 The Double Cluster in Perseus 
 
 CXI 
 
 . 241 
 
 3I4- 
 
 Void space in Sagittarius 
 
 
 . 241 
 
 3I5- 
 
 Kullmer's " Star-finder " 
 
 
 247 
 
 3 l6. 
 
 " Pillar- and-Claw " Stand 
 
 
 . 261 
 
 317. 
 318. 
 
 3-inch Portable Equatorial Telescope 
 Old-fashioned EnglishEquatorial, circaUgo 
 
 '. CXTI 
 
 263 
 . 264 
 
 3*9- 
 
 lo-inch Equatorial Telescope (Cooke) 
 
 . CXIII 
 
 265 
 
 320. 
 
 Standard Photographic Equatorial (Grubb) 
 
 . CX IV 
 
 . 266 
 
 321. 
 
 Vienna 2 7- inch Refractor (Grubb) 
 
 . cxv 
 
 . 267 
 
 322. 
 
 Eye-end of the Vienna Refractor (Grubb) . 
 
 . CXVI 
 
 . 268 
 
LIST OP ILLUSTRATION 
 
 s. 
 
 xxni 
 
 FIO. 
 
 PLATE 
 
 PAGE 
 
 323. so-inch Refractor of the Pulkova Observa- 
 
 
 
 tory (Repsold) 
 
 . cxvn 
 
 . 269 
 
 324. Photographic Equatorial of the Radcliffe 
 
 
 
 Observatory, Oxford .... 
 
 CXVIII 
 
 . 270 
 
 325. Siderostat Equatorial of the Cambridge 
 
 
 
 University ..... 
 
 rt 
 
 . 270 
 
 326. 36-inch Refractor of the Lick Observatory 
 
 
 
 (Warner & Swasey) .... 
 
 . CXIX 
 
 . 271 
 
 327. 36-inch Refractor of the Lick Observatory 
 
 
 
 (another view) ..... 
 
 . cxx 
 
 . 274 
 
 328. Eye-end of the Lick Refractor 
 
 . CXXI 
 
 . 2740 
 
 329. Distant View of the Lick Observatory 
 
 
 
 (H. E. Mathews) .... 
 
 . CXXII 
 
 . 274& 
 
 330. The Dearborn Observatory, Chicago 
 
 CXXIII 
 
 275 
 
 331. Equatorials under Construction at the 
 
 
 
 Dublin Works, 1912 (Grubb) . 
 
 CXXIV 
 
 . 276 
 
 332. Wooden Frame work of an Observatory Roof 
 
 . cxxv 
 
 . 277 
 
 333. The " Lethen Grange " Observatory, 
 
 
 
 Sydenham ..... 
 
 
 277 
 
 334. Royal Observatory, Cape Town (Grubb) . 
 
 CXXVI 
 
 . 278 
 
 335. Papier-mache Dome on an Iron-framed 
 
 
 
 Observatory (Grubb} 
 
 
 278 
 
 336. Barcelona University Observatorv (Grubb) 
 
 " 
 
 . 278 
 
 337. Calton Hill Observatory, Edinburgh (Grubb) 
 
 
 
 . 278 
 
 338-40. Observatory fitted with Rising and 
 
 
 
 Falling Floor ; 3 positions (Grubb) 
 
 CXXVII 
 
 . 279 
 
 341. Sir W. Peek's Observatory, Rousden, 
 
 
 
 Devonshire ..... 
 
 CXXVIII 
 
 . 280 
 
 342. Mr. J. Tebbutt's Observatorv, Windsor, 
 
 
 
 N.S.W 
 
 
 . 280 
 
 343- The Imperial Observatory, Vienna , 
 
 CXXIX 
 
 . 281 
 
 344. Telescope at the Treptow Observatory, 
 
 
 
 Berlin 
 
 . cxxx 
 
 . 282 
 
 345. 4-ft. Reflectorof the Melbourne Observatory 
 
 
 
 . 282 
 
 346. 28-inch Refractor of the Greenwich Obser- 
 
 
 
 vatory ...... 
 
 CXXXI 
 
 . 283 
 
 347. Meridian Circle, U.S. Naval Observatory, 
 
 
 
 Washington ..... 
 
 J 
 
 . 283 
 
 348. Time all over the World 
 
 
 . 291 
 
 349. The Transit Instrument 
 
 
 295 
 
 350. Venus and a Star in a Transit Instrument 
 
 
 . 297 
 
 351. Diagram to represent the Equation of Time 
 
 
 . 299 
 
 352. Secchi's Types of Stellar Spectra 
 
 
 . 307 
 
 353. Central Portion of Orion (Longbottom) 
 
 CXXX1I 
 
 314 
 
 354. " The Sickle " in Leo .... 
 
 CXXXIII 
 
 315 
 
 355. The Constellation Orion 
 
 
 315 
 
 356. The " Southern Cross " . 
 
 CXXXIV 
 
 . 316 
 
 357- The Spiral Nebula, 57 M Canum Venati- 
 
 
 
 corum (Earl of ftosse) 
 
 cxxxv 
 
 . 3i7 
 
THE GREEK ALPHABET 
 
 ** The small letters of this alphabet are so frequently emp'oyed in 
 Astronomy that a tabular view of them, together with their pronunciation, 
 will be useful to many unacquainted with the Greek language. 
 
 a Alpha. 
 Beta. 
 y Gamma. 
 8 Delta, 
 e Epsilon. 
 C Zeta. 
 rj Eta. 
 6 Theta. 
 t Iota. 
 K Kappa. 
 X Lambda. 
 /A Mu. 
 
 v Nu. 
 Xi. 
 
 o O- micron, 
 TT Pi. 
 p Rho. 
 or Sigma. 
 r Tau. 
 v Upsllon. 
 <f) Phi. 
 X Chi. 
 ^ Psi. 
 co O-mega 
 
ASTRONOMY. 
 
 CHAPTER I. 
 INTRODUCTION. 
 
 The scope of the Science of Astronomy. Its modern dev elopement. 
 The other sciences which come in contact with it. The resulting 
 necessity of keeping the treatment of the science within defined 
 limits. The different divisions of pure astronomy. Mathematical 
 Astronomy. Lord Grimthorpe's book, "Astronomy without Mathe- 
 matics." Theoretical Astronomy. Descriptive, or Visual Astronomy. 
 Practical Astronomy. Amateurs may dispense with know- 
 ledge of mathematics altogether and of the theory of telescopes 
 and optics in part. The modern application of the spectroscope. 
 
 THE word "astronomy," coming as it does from two Greek 
 words which, in combination, represent the idea of " the Laws 
 of the Stars," fails altogether to indicate especially the modern 
 scope of the science with which it professes to deal. The fact 
 is that the discoveries of modern times, which supplement the 
 astronomy known to the people who lived a century or two ago, 
 have extended it into so many other fields of knowledge that 
 it is not altogether easy always to say where astronomy, pure 
 and simple, ends and something else begins. The chemist, 
 the photographer, the optician, and to some extent the geo- 
 logist, are all concerned, or consider themselves concerned, in 
 the sphere which formerly was limited to pure astronomy, 
 being the Sun, Moon, Planets, Comets, and Stars, and the 
 phenomena strictly connected with and arising out of the study 
 of these various celestial objects. 
 I 
 
2 ,. l r ' ; -INTRODUCTION. 
 
 It will be my endeavour in the following pages to keep as 
 closely as I reasonably can to astronomy in its older and more 
 limited sense, because were I to attempt to draw into the 
 astronomer's net everything which, by modern custom or prac- 
 tice, comes over the border-line, this book might be open to the 
 objection that it comprised too much of everything and not 
 enough of anything. 
 
 The Science of Astronomy, taken as a whole, itself embodies 
 several distinct lines of thought and treatment. One of these 
 may be termed Mathematical Astronomy, and perhaps it may 
 be said that it is this subdivision which is most generally 
 assumed by people who have not looked into details to be the 
 cardinal feature of the science, and therefore the one which 
 comes first into the mind of the general reader as the dominant 
 character of the science. This explains the fact that often 
 when I have recommended the study of astronomy to persons 
 who have never thought much about the matter, I have been 
 met with remarks couched more or less as follows : " Yes, I 
 dare say it is an interesting subject, but it is too mathematical 
 for me, and I know nothing of mathematics." All this is, in 
 a sense, fallacious. Whilst it is perfectly true that a professed 
 student who wishes to get up the subject to the fullest extent 
 must be of a mathematical turn of mind, and be prepared to 
 go through to the highest mathematics, it is a very great 
 mistake to suppose that unless this is done it is no good taking 
 up the subject at all. The view which I am now presenting is 
 not novel, for a great many years ago the late Lord Grim- 
 thorpe, when he was plain Mr. Beckett-Denison, Q.C., 
 published a very useful little book with the pointed title of 
 "Astronomy without Mathematics/' Perhaps in some general 
 sense the reader will find that I have trodden in the footsteps 
 of my departed friend, but nobody could possibly assimilate 
 Lord Grimthorpe's style and language, which was completely 
 sui generis in every sense of those useful words. 
 
 Mathematical Astronomy may otherwise be spoken of as 
 
DIFFERENT BRANCHES OF ASTRONOMY. 3 
 
 Theoretical Astronomy, because it covers the theories of the 
 movements of such of the heavenly bodies as move, and the 
 laws which govern their movements, and so enables the advanced 
 students and professors to predict with precision and detail the 
 motions of the planets and other moving bodies whose positions 
 in the sky from day to day and month to month and year to 
 year are set out in our almanacs. 
 
 In a measure independent of this, we have what may be 
 called Descriptive, or Visual Astronomy. This represents, with 
 respect to the heavens, the work done by the newspaper re- 
 porter and the illustrated newspaper with regard to things 
 mundane. In other words, the student of astronomy who 
 concentrates his attention on the descriptive side spends his 
 time in using his eyes to see what he can see, and to draw 
 with his pencil or record with his camera what he has seen, 
 and perhaps to commit to writing his observations for the use 
 either of himself or of somebody else. It is obvious that this 
 is the popular, everyday side of the subject, and that people 
 with fairly good eyes and a certain amount of common sense 
 and intelligence can study the celestial bodies with pleasure 
 and profit, even although they know little or nothing of mathe- 
 matical astronomy, and have no great acquaintance with the 
 third leading subdivision of the science which is called 
 Practical Astronomy. 
 
 Practical Astronomy deals with instruments, processes, and 
 methods with the principles, the construction, and the use 
 of telescopes, the construction and use of star-maps, the 
 instrumental measurement of angles and distances, and the 
 tabulation of observations and the drawing of conclusions from 
 them. 
 
 As in the former case a student may do a good deal of useful 
 work with his eyes without troubling himself much or at all 
 with mathematics, so also he can do useful work, and derive 
 pleasure from it, in connection with descriptive astronomy, 
 using th telescope to help him. And this, though he knows 
 
4 INTRODUCTION. 
 
 little or nothing about the theory and construction of tele- 
 scopes, or how they are put together, or the names of the 
 different sorts of lenses which he uses each time that he 
 handles his telescope. In mentioning the range of astronomy 
 it must not be forgotten how important to us all (at times) is 
 that branch or subdivision of the subject which goes by the 
 name of Nautical Astronomy the application of the science to 
 the navigation of ships ; but that, of course, is entirely beyond 
 the scope of this work. 
 
 I hope that the foregoing ideas will be realised by those 
 people who read this book, and that accordingly they will 
 also realise the fact that they can obtain a great deal of 
 pleasure and profit from a study of such departments of as- 
 tronomy as may be readily reached without great exertions 
 of the mind, and without any large expenditure in the way of 
 apparatus. 
 
 There is only one more subject which must in brief form find 
 a place in this volume, and that is Spectroscopy. It is only 
 within 50 years or so that the spectroscope has been brought 
 into general use as an accessory to the study of astronomy ; 
 and it has come, almost with a rush, to occupy a prominent 
 place in the minds and work of those who, going beyond the 
 modest aims of this volume, desire to dive into hidden things 
 which do not in the first instance appeal to the eyes of the 
 casual student of nature who takes up astronomy. 
 
 In order not to burden the pages of the book with uninviting 
 masses of figures, statistics involving numerical quantities will 
 to a certain extent be excluded from the text and relegated 
 to an Appendix, where they will be more accessible for consulta- 
 tion and comparison. 
 
CHAPTER II. 
 THE SUN. 
 
 Important position occupied by the Sun. Its general appearance. Its 
 mottled surface- ' ' Granulations ' ' probably the best word to describe 
 it. Spots on the Sun. Their periodicity. General description of 
 them. Peculiarities of spots. Period of the Sun's rotation. The, 
 Photosphere. Distribution of the spots in latitude. Discovery of 
 the periodicity of the spots. Aurora. Terrestrial Magnetism. 
 Sun-spots and terrestrial weather. Possible influence of some of 
 the Planets on Sun-spots. Wilson's theory respecting them. Vortex 
 movements on the Sun. Faculce. Apparent movements of spots 
 at different seasons of the year. Notable large spots. Light- and 
 heat-giving powers of the Sun. The Krakatoa sunsets. 
 
 WE are so accustomed to see the Sun and feel its heat-giving 
 effects that we are apt to lose sight of the important position 
 which it occupies in the Universe or perhaps I ought rather 
 to say in our Solar System, because the Universe, in the proper 
 sense of the term, extends far beyond our Solar System, which 
 is probably only one of many systems, and perhaps even not 
 the most important. The late R. A. Proctor entitled one of 
 his many books, " The Sun : Ruler, Fire, Light, and Life of the 
 Planetary System." The phrase was a comprehensive one, but 
 did not go beyond the legitimate expression of the facts. 
 
 Everybody, I suppose, knows at any rate, in a general 
 way that the Sun is the centre of our Solar System, not only 
 in the sense in which the nave is the centre of a carriage-wheel, 
 but as the immediate and the prime source (humanly speaking) 
 of all light and life on the Earth ; moreover, it is also the 
 central force which keeps everything going. To pursue this 
 
 5 
 
6 THE SUN. 
 
 thought further would lead me into a disquisition on the Law 
 of Gravitation and the laws generally of Celestial Motions, 
 which, it will be understood from the previous chapter, would 
 be foreign to the aims of this volume. 
 
 If we look at the Sun soon after sunrise or towards sunset, 
 or through a fog, or through a smoked or dark-coloured glass, 
 what do we see ? Apparently a luminous disc, which for our 
 present purpose may be regarded as a true circle, though, when 
 it is viewed near sunrise or sunset, the circular outline is 
 slightly distorted. To the naked eye this disc appears as a 
 flat patch of yellowish light, possessed of great inherent bright- 
 ness and powerful heat-distributing properties. 
 
 But this is a very poor description of what the Sun really is. 
 The astronomer, by means of his instruments and calculations, 
 determines it to be very large and not flat, but globular or 
 spherical a ball, in fact. To the naked eye the Sun seems to 
 have the same smooth surface and yellowish tint all over ; in 
 a telescope, however, matters are far otherwise. The surface 
 appears speckled or stippled, and near the limbs or edge of the 
 circle streaked, whilst every now and again and here and there 
 blackish spots are sometimes visible, the centre of the Sun 
 being always brighter than the edges. This latter fact is a 
 very obvious result of its globular form, but the mottling and 
 streaks and spots depend on certain physical causes which are 
 not in every respect capable of full explanation. 
 
 A great many words and phrases have been brought into 
 use with the object of conveying an intelligible idea of the 
 appearance of the surface of the Sun. "Willow-leaves," "rice- 
 grains," "shingle beach," "mottling," "stippling," "granula- 
 tions," and " photospheric network " are amongst the terms 
 which have been employed, first by one and then by another 
 observer. The last-named term is decidedly objectionable, 
 because it conveys too much the idea of an artificial formation. 
 On the whole, because of its vagueness, I am inclined to prefer 
 the word "granulations" as being most expressive of the 
 
THE SUN'S SURFACE. 7 
 
 ordinary appearance of the Sun in telescopes of sufficient .size 
 to show anything. 
 
 A great controversy raged over several of these phrases half 
 a century or less ago. The term "willow-leaf" was put for- 
 ward by Mr. James Nasrnyth,the inventor of the steam-hammer, 
 who in his later years became a great observer, being also very 
 skilful with his pencil. His idea was that the whole surface of 
 the Sun exhibited the appearance which would be presented by 
 a large mass of willow-leaves if flattened out and lying pro- 
 miscuously one on the top of another at all possible angles. 
 Though the term "willow-leaf" did not meet with general 
 acceptance, it set astronomers thinking how they could best 
 describe the general appearance of the Sun's surface, which all 
 agreed was not smooth and uniform, as a planed slab of wood 
 covered with a coating of oil-paint appears smooth and uniform. 
 Langley's well-known picture of what he called a "Typical 
 Sun-spot" brings out the "willow-leaf" idea, though I do not 
 think he used the words. [Plate II.] 
 
 Sir W. Huggins, one of our greatest and most experienced 
 English observers, took up the subject very carefully at the 
 time, and summarised his conclusions by giving the preference 
 to the word "granule," because no positive form is implied by 
 its use. He thought "rice-grain" was a suitable expression to 
 represent what was seen in small telescopes, but that there was 
 thereby implied a definiteness of shape which to some extent 
 disappeared when large telescopes and high powers were 
 resorted to. He thought, however, that it might safely be said 
 that these objects, whatever their nature, did affect an elongated, 
 oval, or lenticular form. 
 
 These opinions have not been seriously disturbed by later 
 discoveries, and, on the whole, it may be said that the general 
 surface of the Sun presents a granulated appearance to which 
 some apply the word " network," though, as I have said before, 
 I think the word is too precise. Another word in use is " pore " ; 
 and this has something to recommend it, because when the 
 
8 
 
 THE SUN. 
 
 spots (presently to be described) break out, they often start 
 from a pore as a place of origin. 
 
 Other similes have been suggested for the granulations on 
 the surface of the Sun. An American astronomer has likened 
 them to the snow-white ends of coral. He says that the picture 
 
 Fig. 2. Madrepora Specifera. 
 
 An East Indian Variety of Coral. 
 
 here given (Fig. 2) of a specimen of East Indian coral in the 
 Natural History Museum at Williams College, Massachusetts, 
 " held at arm's length, and viewed with eyes partially closed, 
 gives a tolerable idea, though on an enlarged scale, of the 
 appearance of the solar mottling as seen in the largest 
 telescopes." 
 
GROWTH OF SUN-SPOTS. 9 
 
 The spots on the Sun are a very notable feature, and now 
 and again become a very striking feature visually, and the 
 whole history of their observation is one of intense interest. 
 Before the invention of the telescope little or nothing was 
 thought or known of them, because it was only at long intervals 
 that a spot sufficiently large to be seen with the naked eye 
 became visible. And . even when telescopes did come into 
 use, and spots were much more often noticed, it was a long 
 time more than 200 years before observation of them came 
 to be made systematically, and some 250 years before it was 
 realised that their visibility from time to time depended upon 
 a recognisable law of periodicity. 
 
 Before dealing with this law let us consider for a while some- 
 thing about a spot on the Sun qua spot. We will suppose that 
 on a certain day an observer turns his telescope, armed with 
 a suitable dark glass, on to the Sun, and that he notices nothing 
 but the uniform granulated surface of which I have already 
 spoken, and that on the following day he detects a little 
 blackish point. If he watches this point during several days 
 he will notice that it increases in size, and very likely develops 
 into two blackish points. In such case the two will separate 
 from one another more and more, become larger in size and 
 probably more irregular in shape, whilst, when they have 
 become considerably separated, other outbursts will take place 
 in between the two original spots, so that a very broken but 
 somewhat regular irregular group or chain of spots will have 
 sprung up. The forward spot of the original pair will become 
 as it were the leader of the group, the word " forward " being 
 used to indicate the spot which is at the end of the group 
 reckoning in the direction in which it will have been noticed 
 that the group is moving over the Sun's disc, which will be 
 from E. to W. 
 
 It is necessary to give an explanation here. Whether a spot 
 is endowed with an absolute motion of its own is an inde- 
 pendent question which may, or perhaps may not, have to be 
 
10 THE SUN. 
 
 answered in the affirmative in any given case ; but, inasmuch 
 as the Sun is endued with a motion of rotation on its axis, 
 every spot, whatever its inherent permanency may be, will 
 be visually noticed to be constantly in motion across the 
 Sun's disc. 
 
 As the Sun rotates on its axis from E. to VV. in about 
 25^ days, no spot can remain continuously on view for more 
 than about half of this period actually about 13 days for a 
 reason to be presently given. 
 
 If, as often happens, a spot has a lifetime of several weeks, 
 it will, after disappearing on one edge of the Sun, reappear a 
 fortnight later on the other edge, and so on and so on, it may 
 be for two or three months or more. 
 
 Let us now go back to the chain or group of spots with 
 the consideration of which we started. This will be seen to 
 undergo incessant changes the constituent spots increasing 
 in size and number or decreasing as the case may be. Sooner 
 or later they will all disappear, being smothered or blotted out 
 by the onward rush of the waves of luminous matter which 
 constitute the ordinary surface of the Sun as seen by us, and 
 to which the name of Photosphere (or shell of light) has been 
 given. 
 
 Spots on the Sun do not always appear in groups or with a 
 gregarious tendency, for sometimes we may see a single spot 
 which apparently has no neighbours or belongings. Near 
 such a spot sometimes small neighbours may spring up, or, 
 on the other hand, it may retain its individuality for some time, 
 increasing in size or diminishing, but retaining during its whole 
 existence a compact and somewhat symmetrical form which 
 more or less approximates to a circle, like a hole bored in a 
 piece of wood by a gimlet, which, when removed, shows the 
 edges to be rough and frayed. 
 
 So much for the personal appearance of an average Sun-spot, 
 but a good deal remains to be said on the subject. When a 
 spot is beginning to disappear it does not always do so by 
 
CHANGES IN SUN-SPOTS. IT 
 
 a uniform contraction all round its circumference. Not un- 
 frequently the final closing up will be preceded by a bridge 
 of luminous matter darting over- the dark area, and forming 
 for the time it endures a bridge over the dark area, making 
 indeed the whole appearance to be that of two small spots side 
 by side instead of one large spot. 
 
 The mass of material which is available for an account of 
 
 3' 
 
 Fig. 3. Spot on the Sun, Aug. 14, 1868. 
 
 the Sun, even if only limited to the standpoint of visual obser- 
 vation, is so great that it is very difficult to know how much 
 to include and what to exclude in writing an account of the 
 Sun. Something more, however, needs to be said as to the 
 physical appearance of the Sun's surface and of individual spots. 
 We talk about spots on the Sun, and colloquially call them 
 dark spots ; but that adjective is really only a relative term, 
 and must not be pushed too far. The ordinary dark central 
 
12 THE SUN. 
 
 part of a spot is commonly called the Umbra (Lat. " shadow "). 
 This is surrounded usually by a fringe of a lighter shade to 
 which the name of Penumbra is applied (Lat. pene, almost ; 
 umbra, a shadow). 
 
 These two portions of an ordinary spot are generally very 
 distinctly defined, and the umbra does "not usually pass into 
 the penumbra by a gradual change of intensity. It occasion- 
 ally happens that, within the limits of the Umbra, there may 
 be noticed a small patch of deeper blackness to which Dawes 
 applied the term Nucleus. But Dawes's description of an 
 ordinary nucleus as "intensely black" is again a misnomer, 
 for it is only relatively dark, showing in reality, according to 
 Langley, a violet purple hue. One spot may either have its 
 own penumbra, or several spots may be included in one 
 penumbra. Moreover, the outer edges of a penumbra will 
 usually appear darker than the interior portions. This, no 
 doubt, is a mere effect of contrast. The outer edge of a 
 penumbra is generally of a very irregular outline, but not 
 always so, for sometimes the outline bears a certain general 
 resemblance to the spot which it surrounds. Whilst the 
 spots themselves are often very irregular in shape, yet, on 
 the other hand, they are sometimes very compact and 
 symmetrical a remark still more true of nuclei where a 
 nucleus exists. 
 
 The duration of the existence of a spot is a matter of 
 extreme uncertainty. Sometimes a spot may be seen to 
 appear and disappear in the course of a few hours ; or it 
 may remain visible, disappearing and reappearing several 
 times by virtue of the Sun's axial rotation, as already pointed 
 out. It cannot be said that every spot remains absolutely 
 fixed in its position during the period of its visibility. Some 
 spots certainly have a motion of translation of their own which 
 makes it impossible to, rely upon their disappearance and 
 reappearance as a means of deducing the exact period of the 
 Sun's rotation. 
 
FIG. 4 
 
 PLATE II. 
 
FIGS. 5-8 
 
 PLATE in. 
 
 Oct. 22, 1905. 
 
 July 31, 1906. 
 
 Feb. 7, 1907. May 6, 1907. 
 
 Disc of the Sun, showing Spots (E. W. Barlow}. 
 
FIGS. 9-12 
 
 PLATE IV. 
 
 July 15, 1907. 
 
 May 4, 1908. 
 
 Aug. 3, 1908. Sept. 2, 1908. 
 
 Disc of the Sun, showing Spots (E. W. Barlow}. 
 
FIGS. 13-15 
 
 PLATE V. 
 
 The Great Sun-spot of 1865 (Howlett). 
 
APPARENT MOVEMENTS OF SUN-SPOTS. 13 
 
 However, as the result of multitudes of observations by 
 various observers, we shall probably be not far wrong in 
 putting this at 25 days 8 hours. It must be noted, however, 
 that these figures are not a measure of the time which a spot 
 takes to disappear and reappear and disappear again. This 
 occupies 27 days 7 hours, being longer than the true rotation 
 once, on its axis, of the Sun itself, because between the com- 
 mencement of an observation dating from the disappearance 
 of a spot at the eastern limb and its arrival at the same point 
 again, the Earth has moved forwards, and the Sun has, so to 
 speak, to turn a little farther than one revolution in order 
 to be again abreast of the Earth. 
 
 We have not yet exhausted the special features of the Solar 
 Orb as made manifest even to the casual observer. In the 
 first place, the intensity of the solar light is greater in the 
 centre than at the exterior limits of the disc. This is a natural 
 consequence of the obvious fact that, in looking at the edges, 
 we are looking through a thicker layer of the outer coating 
 of the Sun than when we look straight at it in the middle 
 of the disc. It remains now to answer, or to try and 
 answer, the questions, "What is the Sun?" and "How is it 
 put together?" These questions are difficult, and are very 
 much mixed up. 
 
 To say that the Sun is not a solid body as the Earth is, and 
 with a luminous atmosphere surrounding it, is a statement 
 altogether inadequate, and beside the mark. The general 
 opinion now is that there is probably nothing solid in the 
 Sun, but that it is an enormous mass of gaseous matter of 
 various kinds, surrounding which are two or more shells or 
 strata of matter of different chemical constitution, including 
 hydrogen gas, and divers metallic vapours. To the innermost 
 of these layers the name of Photosphere has been given, and 
 this is the visible source of the ordinary solar light which 
 reaches the Earth. Next outwards comes the Chromo- 
 sphere, a thin casing of luminous matter, chiefly hydrogen 
 
14 THE SUN. 
 
 gas, and the seat of the Red Flames seen in total eclipses of 
 the Sun ; whilst, still reckoning outwards, there is a third shell 
 to which the name of " Corona " has been given. We shall have 
 to consider further some of these matters in the chapter (post) 
 which treats of eclipses of the Sun. 
 
 The spots do not appear promiscuously all over the Sun. 
 They are never seen at either of the poles or anywhere near 
 them. They seldom reach a greater latitude, N. or S., of 
 the Solar Equator than about 30 to 37 ; but, even within 
 these equatorial regions, they are not promiscuously distri- 
 butedthat is to say, they are rare at or near the Solar Equator, 
 and perhaps may be said to be most usually seen in latitudes 
 between 10 and 20 N. or S., being as a rule more numerous 
 and of greater general size in the northern hemisphere, 
 especially between the latitudes of 11 to 15. I shall have to 
 recur to this question of the distribution of the spots in latitude 
 after I have spoken of their periodicity. 
 
 This is a very interesting and important detail. For more 
 than two hundred years after the invention of the telescope 
 and of its employment in the observation of Sun-spots, they 
 were regarded as haphazard manifestations of some kind of 
 outbursts on the Sun's surface, the causes of which were quite 
 unknown, and least of all were imagined to be subject to 
 any laws. 
 
 in 1826 a German amateur named Schwabe, who lived 
 at Dessau, commenced a systematic observation of the Sun 
 day after day. He appears to have been able to see it, on 
 an average, about 300 days in every year, and he carried 
 on such observations for about 30 years, when he reached 
 a remarkable stage in his career. He seems to have 
 begun by suspecting that, if he observed the Sun through a 
 sufficiently long number of years, he would find that the spots 
 were subject to a law or laws of some sort. Twelve years 
 enabled him to satisfy himself that there was a periodicity 
 about them : he then spent another 6 years in trying to 
 
FIGS. 16-18 
 
 PLATE VI. 
 
 Sun-spots. 
 
 (i) Oct. 20, 1905. (2) Nov. 16, 1905, showing granulations and faculce (Barlow). 
 (3) June 22, 1889 (McK.). 
 
FIGS. 19-26 
 
 PLATE VII. 
 
 .-r 
 
 ! 
 
 ^-*.A''' 
 
 
 ~_ 
 
 'm 
 
 
 Sun-spots in 1882 at Various Dates (Corlie). 
 
PERIODICITY OF SUN-SPOTS. 15 
 
 impress astronomers with the truth of his opinion, and in 
 the course of another period of 12 years or more he was 
 able to convince mankind that the periodicity of the Sun-spots 
 was absolutely assured ; and, to cut a long and very inter- 
 esting story short, it will suffice for me now to say that, as 
 regards their numbers, the spots are subject to a period of 
 slightly over n years. Or, to put it in another way, 1911 
 having been a year of practically no spots at all, 1912 has 
 seen a few ; they will now go on increasing every year until 
 about 1916, when they will be very abundant, reaching their 
 period of maximum ; they will then diminish until 1922 or 1923, 
 when very few, and during many months none at all, will be 
 visible. 
 
 This question of periodicity and its amount of in years 
 is now established to a dead certainty. It must be stated, 
 however, that a minimum does not occur midway between 
 two maxima, but that 6J years elapse between a maximum and 
 the next minimum, leaving 4^ years as the interval between 
 a minimum and the next maximum. These precise figures 
 for the intervals are not, however, quite assured. 
 
 We are not yet able to put a very explicit interpretation 
 upon this 1 1 -year period, though there are some incidental 
 coincidences connected with it which are striking and" unmis- 
 takable. These include the diurnal variation of the magnetic 
 needle and manifestations of the Aurora Borealis. It is beyond 
 the scope of this volume to discuss in detail terrestrial magnet- 
 ism and the Aurora. It must suffice, therefore, for me to 
 state that the magnetic needle is subject to a minute change 
 of an oscillatory character in the nature of an effort on the 
 part of the needle to turn towards the Sun. These diurnal 
 vibrations are not uniform, but vary in extent during a period 
 of years now recognised as being about 1 1 years. Mani- 
 festations of the Aurora also vary from year to year during 
 1 1 years ; and now comes the singular coincidence that 
 maxima of terrestrial magnetic displays and of auroral 
 
16 THE SUN. 
 
 manifestations are synchronous with maxima of Sun-spots, and 
 minima with minima. 
 
 The coincidences which have just been pointed out will be far 
 more easily realised by an inspection of the annexed diagram 
 than by the fullest verbal description. The rise and fall of 
 the curves in the diagram indicate in each case both the 
 extent of the changes and the dates thereof ; and the most 
 cursory inspection of the three divisions of the diagram will 
 show at once the coincidences of maxima and of minima and of 
 dates. 
 
 With these facts before us it is not permissible to doubt that 
 there is some intimate connection between certain events 
 which happen on the Sun and certain events which happen on 
 the Earth. What the nature of the connection may be cannot 
 quite definitely be stated, but that electricity is concerned in 
 the matter in some way or other seems perfectly certain. 
 There is, indeed, more evidence on record than I have yet 
 stated. For instance, on September i, 1859, tvvo English 
 observers in different places were examining a fine group of 
 Sun-spots, and suddenly, at 11.18 a.m., two patches of bright 
 light burst forth in front of the spots. They were at first 
 thought to be due to a fracture in the screen attached to the 
 object-glass of the telescope ; but such was not the case. The 
 patches of light were distinctly on, or connected with, the Sun 
 itself. They remained visible for about five minutes, during 
 which time they moved a short distance. 
 
 A remarkable fact has now to be added. Simultaneously 
 there happened a great disturbance of the magnetic instru- 
 ments at the Kew Observatory, followed 16 hours afterwards 
 by a violent magnetic storm, during which the telegraphs were 
 interrupted and Auroras appeared. This incident does not 
 stand alone, for on several more recent occasions large 
 Sun-spots and marked disturbance of instruments recording 
 terrestrial magnetism have been noticed as contemporaneous 
 events. Probably the truth is enshrined in the following 
 
SUN-SPOTS AND WEATHER ON THE EARTH I'J 
 
 words of Mr. H. C. Lewis, an assistant at the Greenwich 
 Observatory : 
 
 " The theory is not improbable that Sun-spots are the result 
 of solar electrical or magnetic storms, and that Auroras are 
 the result of a disturbed electrical condition of the Earth 
 caused by induction from the Sun. The common cause for 
 both phenomena is probably cosmical." 
 
 Maunder has summed up the situation, as regards the ques- 
 tion of solar magnetism, thus : 
 
 " It is evident that, besides sending to us light and heat, 
 the Sun sends us some kind of influence which comes only 
 from certain portions of its surface. We find that there is a 
 tendency for magnetic disturbances to take place when a Sun- 
 spot is on a definite portion of the Sun's disc." 
 
 The question is often mooted as to whether any connection 
 can be traced between the prevalence or absence of spots and 
 the character of the weather on the Earth. The evidence as 
 to this is exceedingly contradictory, and great names are to be 
 found ranged on both sides of the controversy, and it is really 
 impossible to present any trustworthy definite conclusions. 
 
 The matter has been approached from two somewhat inde- 
 pendent standpoints, namely, terrestrial temperatures as dis- 
 tinguished from terrestrial rainfall. Perhaps it is in respect of 
 temperatures that the evidence is more contradictory than in 
 the matter of rainfall. For instance, Wolf, a well-known Swiss 
 observer, considered that he had found decisive evidence " that 
 years rich in solar spots are in general drier and more fruitful 
 than those of an opposite character, while the latter are wetter 
 and stormier than the former." Another Swiss observer, 
 Gautier, discussing 62 sets of observations, extending over 
 1 1 years and taken at various places in Europe and America, 
 arrived at exactly the opposite conclusion. Professor C. P. 
 Smyth considered that a great wave of heat passes over the 
 
 2 
 
l8 THE SUN. 
 
 Earth every 11 years and a fraction, and nearly coincident 
 with the beginning of the increase of each Sun-spot cycle. 
 A German observer, Steen, collecting materials obtained during 
 30 years ending with 1903, considered that there was evidence 
 that the maxima and minima of thunderstorms occur at about 
 the periods when Sun-spots are at their maxima and minima 
 respectively. 
 
 Perhaps it may be added with safety, though I shrink from 
 dogmatising on the matter, that a year of high temperature is 
 coincident with an absence of Sun-spots. This idea, which 
 was put forth by E. J. Stone about 1870, as the result of 30 
 years' observations at the Cape, and by Abbe as the result of 
 60 years' observations at Munich, certainly found a confirma- 
 tion in the long prevalence of intense heat in 1911, which was 
 a year of unusual deficiency in Sun-spots. 
 
 The question has been seriously mooted as to whether spots 
 on the Sun are subject to any further cycle than the ii'i year 
 cycle, and whether planetary influences come into the question. 
 It seems that an affirmative answer must be given on both 
 these points. Wolf considered that the activity of the Sun, as 
 indicated by spots, has two further periods of 55^ years and 
 166 years respectively ; the former period being made up of 
 5 normal cycles and the latter of 15 normal cycles. This is a 
 matter which needs and deserves further investigation. 
 
 The following table of dates of recent Sun-spot maxima and 
 minima will be useful for reference : 
 
 Maxima. Minima. 
 
 1860-1 
 
 1867-2 
 1870-6 
 
 1878-9 
 1884-0 
 
 1890*2 
 1894-0 
 
 1901-9 
 1906-4 
 
 1911 
 
FIGS. 27-30 
 
 PLATE VIII. 
 
 Jan. 31 
 
 Feb. i 
 
 
 COM PAR/JTI v 
 
 3jo 32.0" 
 
 
 GREAT SPOT 
 
 AT S U N '5 Lt Ki 8 
 
 Jan. 5 
 
 # - 
 
 Feb.; 
 
 The Great Sun-spot of February 1905. 
 
 181 
 
FIGS. 31-35 
 
 PLATE IX. 
 
 Changes in Spots as they approach the Sun's Limb. 
 
 (E. W. Barlow.} 
 
 1906. (i) May 13 ; (2) May 14 ; (3) May 15; (4) May 16 ; (5) Mav 18. 
 
WHAT ARE TttE SPOTS. 1<) 
 
 As regards planetary influences, there is a considerable 
 amount of testimony to show that the prevalence of Sun-spots 
 depends in some way on the position of certain of the Planets 
 with respect to the Sun. Wolf thought he found traces of an 
 influence exerted by Venus in the course of its annual revolu- 
 tion round the Sun, and Balfour Stewart thought that Mercury 
 and Jupiter might also be brought in as exercising some effect. 
 The influence of Venus, assuming it to be real, implies that 
 the planet causes spots to break out in longitudes of the Sun 
 which are opposite to the planet, though, supposing a spot to 
 have been started by Venus, its maximum developement does 
 not take place till, by the Sun's rotation on its axis, the place 
 of origin has been carried farthest away from Venus. 
 
 In spite of the distinguished names which are attached to 
 some of these surmises as regards planetary influence, I do not 
 feel inclined to rely very much upon them because of the 
 obvious liability to mistakes being made in the inferences, 
 owing to the general complexity of the whole subject and the 
 difficulty of proving connections of cause and effect. 
 
 A large amount of attention has been bestowed on the Sun 
 of late years by astronomers generally throughout the world, 
 with the especial object of determining, if possible, what are 
 the causes of Sun-spots, and what are the physical circum- 
 stances which may be supposed to govern them. Much pro- 
 gress has been made, but, nevertheless, more information than 
 we at present possess is needed. The oldest and most 
 attractive theory of the spots is that associated with the name 
 of a certain Professor Wilson, of Glasgow, as modified by 
 Sir W. Herschel. This assumed that the Sun is surrounded 
 by two atmospheres, arranged somewhat as the skins of an 
 onion, the outer one being luminous (thence termed the Photo- 
 sphere, as already mentioned) and the inner one non-luminous, 
 and that the spots are rents or apertures in these two skins 
 through which we see revealed the solid body of the Sun itself. 
 
 Bearing in mind that it is now the received opinion that the 
 
20 THE SUN. 
 
 Sun is not a solid body, it must, nevertheless, be confessed that 
 the Wilson theory has something very attractive about it, in 
 view of what one sees when a Sun-spot is scrutinised with a 
 telescope. Suppose we find a spot somewhat symmetrical in 
 shape, and in the middle of the Sun's disc, and watch its 
 gradual change of place towards the edge by reason of the 
 Sun's axial rotation. It will be seen that such a spot, whilst it 
 of course undergoes foreshortening, in accordance with the 
 natural law of foreshortening when a globe is turning on its 
 axis, undergoes foreshortening on the side nearest the limb 
 which the spot is approaching ; so much so that the penumbra 
 on that side will have ceased to be visible whilst a certain 
 amount of penumbra exactly opposite still remains in view. A 
 person carefully studying the career of a particular spot can 
 hardly fail to be impressed with the feeling that his eye is 
 resting on a cavity with sunken walls, so to speak, all round 
 it, not necessarily perpendicular, but rather in the form of a 
 funnel. 
 
 This theory of the* nature of a Sun-spot finds confirmation in 
 the fact that now and again a large spot, when it is passing out 
 of view and turning the corner of the disc, so to speak, gener- 
 ally appears as a notch in the outline of the disc a fact which 
 distinctly favours the idea that the spots are depressions, and 
 condemns the idea (held by some) that the spots are elevations 
 above the general surface of the Sun. Spots as notches have 
 not infrequently been recorded by observers ; a notable case 
 occurs in a photograph taken at Dehra-Dun, in India, in 1884. 
 
 The newest idea l respecting the condition of the Sun is that 
 put forth in America by Professor Hale (a highly skilled 
 observer) that he has detected signs of Vortices, or cyclonic 
 action of a magnetic nature, in connection with the visible 
 surface of the Sun. Hale has investigated the subject in 
 
 1 I am not at all sure that this idea ought to be considered "new," because 
 I have in my possession a drawing by Hewlett dated May n, 1863, which is 
 actually labelled what it shows, " Interesting Vorticose Group." 
 
FACUL^E. 21 
 
 a very exhaustive fashion, and his conclusions have met with 
 much acceptance ; but it is only fair to add that signs of 
 cyclonic action on the Sun, and of a disposition for the granu- 
 lations to take up sometimes a spiral form, were obtained 
 and noted many years before Hale went to work by observers 
 as early as Huggins and Secchi in the 'sixties and 'seventies 
 of the last century. This branch of solar study is a highly 
 delicate and intricate one, requiring skilled observers and 
 large and special instruments, and therefore is a subject 
 somewhat beyond the scope of this volume. 
 
 Before passing away from the Sun from a sight-seeing 
 standpoint, I must not omit a few words about solar faculce^ 
 These are streaks of light frequently to be noticed in the 
 equatorial regions of the Sun, and near either limb, and 
 often running somewhat in a N. and S. direction. They are 
 generally of no particular form, though perhaps a policeman's 
 truncheon is not a very far-fetched simile to convey an idea of 
 their shape. Without exactly pretending tosay what they are in 
 constitution, it seems at least certain that 'they are elevations 
 or ridges in the Photosphere, possibly even detached masses 
 of luminous matter floating in or on the Photosphere. It would 
 seem that they have some sort of association with spots, in 
 so far that they are often to be found just outside the penumbra 
 of a disappearing spot, or even occupying the place where a 
 spot has actually disappeared. [Figs. 36-37, Plate X.] 
 
 The fact that the position of the'Earth with reference to the 
 Sun at different seasons of the year varies, and that the Sun's 
 axis is inclined to the plane of the Ecliptic, has this result, 
 namely, that a spot on the Sun, if attentively followed during 
 the fortnight it occupies in crossing the Sun's disc, will be 
 found to pursue a path which differs with the season of the 
 year. In June and December a spot will seem to follow a 
 straight path diagonally upwards in the former case, and 
 diagonally downwards in the latter case ; whilst in March 
 1 Latin factila, a torch. 
 
22 THE SUN. 
 
 and September the apparent path will be curved with the 
 convexity in the former case towards the North Pole and 
 with the convexity in the latter case towards the South 
 Pole. 
 
 Astronomical writers of popular books generally try to excite 
 their readers by giving a wonderful array of figures supposed 
 to represent the dimensions of remarkable Sun-spots. I am 
 not convinced of the usefulness of such statistics, and I shall 
 give but a very few. It may be taken for granted that no 
 Sun-spots are fairly visible to the naked eye unless they have 
 a breadth of at least 50,000 miles, but many spots of greater 
 size than this are on record. For instance, on March 15, 1858, 
 a spot was visible having an angular breadth of 4', or about 
 108,000 miles. 
 
 This chapter may be brought to a close with a few statistics. 
 The distance of the Sun from the Earth, or, to put it more 
 consistently, of the Earth from the Sun, may be taken as 
 averaging 92,000,000 miles, which varies slightly in the months 
 of January and July, when, owing to the ellipticity of the 
 Earth's orbit the Earth is nearest the Sun and farthest from 
 the Sun respectively. Why we in England (and in the Northern 
 Hemisphere generally) experience colder weather in January 
 than we do in July, though we are nearer the Sun in January 
 than we are in July, perhaps needs a word of explanation. 
 
 The explanation is exceedingly simple. The meridian 
 altitude of the Sun in January is low, and its rays reach us 
 through a certain thickness of atmosphere, and much of the 
 heat is therefore lost ; but in July the meridian altitude of 
 the Sun is very considerably higher, and its rays descend 
 upon England and the Northern Hemisphere more nearly 
 perpendicularly, and therefore more directly, and through a 
 thinner depth of atmosphere to absorb them. The diameter 
 of the Sun is about 32' of arc (say just over |), or about 
 860,000 miles. The Sun's mass, or attractive power, is 332,000 
 times that of the Earth, and about 750 times that of all the 
 
FIGS. 36-37 
 
 PLATE X. 
 
 
 June 28, 1884. 
 
 Nov. 28 1884. 
 
 Faculae on the Sun (Cortie). 
 
FIG. 38 
 
 PLATE XI. 
 
 [23 
 
HEAT-GIVING POWER OF THE SUN. 23 
 
 planets put together. The density of the Sun is about i^ times 
 that of water. 
 
 These figures are an indication of the comparative lightness 
 of the Sun as a matter of weight. Many experiments have 
 been made to arrive at an idea both of the heat-giving and 
 of the light-giving power of the Sun. The conclusions as 
 to this are very apocryphal, and do not deserve much weight. 
 For instance, it has been stated that our annual share of the 
 heat would melt a layer of ice all over the Earth 100 ft. in 
 thickness, or heat an ocean of fresh water 60 ft. deep from 
 freezing-point to boiling-point ; whilst the direct light of the 
 Sun has been supposed to be equal to that of 5563 wax candles 
 of moderate size at a distance of one foot from the observer. 
 Such figures as these seem rather to savour of " Alice in 
 Wonderland." 
 
 Though attempts have been made to calculate and state by 
 figures the heat-giving power of the Sun, it must be obvious 
 that all such calculations can only be, if not quite imaginary, 
 yet very wild and indeterminate. It is, however, worth while 
 to record a few practical consequences of the power of the Sun's 
 rays being what they are. For instance, in constructing the 
 Breakwater at Plymouth, the men working in diving-bells at 
 a distance of 30 ft. below the surface had their clothes burnt 
 by coming under the focus of the convex lenses fixed at the 
 top of the bell to let in the light. 
 
 Some years ago the bedroom curtains in the house of a friend 
 of mine at Bromley, in Kent, were set on fire by the concentrated 
 Sun's rays ; and I once read in a book of military history 
 relating to Sir R. Abercrombie's expedition to Egypt in 1801 
 that the Turks captured from the French a brass gun which 
 had been fitted up so that every day at 12 noon the gun was 
 fired by the sun igniting a charge of powder by means of a 
 burning-glass (i.e. a double-convex lens), which focussed the 
 Sun's rays on the touch-hole, and so ignited some powder: 
 
 It would not be possible, nor indeed desirable, in my limited 
 
24 THE SUN. 
 
 space to describe in any detail the various pictures of Sun-spots 
 given in this chapter, but the one dated August n, 1868, will 
 really serve to describe a good many Sun-spot pictures. The 
 wisp-like structure of the penumbra will be readily realised, 
 whilst on the southern side of the vast depression (for the 
 penumbra is a depression thousands of miles deep) there will 
 be noticed, closely packed, a vast crowd of rice-shaped grains 
 which appear to be flowing up to and over the edge of the 
 centre. The picture also shows a long straggling line and 
 small spots trailing after the principal spot, which, as has 
 already been mentioned, is often a feature of a prolonged 
 and extended group of spots. It may help to convey an idea 
 of the magnitude of these spot apertures in the Sun's outer 
 atmosphere if I say that the one under consideration is 
 sufficiently spacious for the Earth to be dropped into it with- 
 out touching the penumbra on either side. 
 
 Figs. 19-26 represent various Sun-spots at various dates as 
 observed at the Stonyhurst College Observatory, and have 
 been kindly placed at my disposal for reproduction in this 
 volume by the Rev. A. L. Cortie, S.J. The 4 pictures dated 
 April 1882 show the day-by-day changes in a spot in the course 
 of a week or less. The spot dated Nov. 17, 1882, was 
 accompanied by a great magnetic storm and a magnificent 
 display of Aurora. The spots dated Sept. 29 and Oct. 2 
 and Sept. 13 and Sept. 15, 1883, are examples of spots with 
 double penumbrae. Fig. 37, dated June 28, 1884, gives the 
 whole disc of the Sun with certain spots and a remarkable 
 manifestation of faculas. The picture dated Nov. 28, 1884, 
 shows a very fine group of faculas on the E. limb of the Sun. 
 The whole-page plate [VIII.] dated February 1905 gives the life- 
 history of what became a great spot from its developement from 
 a few small spots. 
 
 Fig. 38 is a representation, taken from a photograph, of the 
 red sunsets for " Red Light ") which created so much sensation 
 in the autumn and winter of 1883, and which were regarded as 
 
KRAKATOA SUN EFFECTS. 25 
 
 one of the most remarkable solar-terrestrial effects of modern 
 times. The strange feature of the Red Light was the peculiar 
 halo which it caused around the Sun by day, and its long 
 duration after sunset. At that time, and during the early 
 evening, the colour was usually orange-red, or even rose, and 
 it stretched far up towards the zenith with a bright spot at the 
 highest point. There was also a bright spot and coloured arch 
 in the E., opposite the point of sunset, as if due to a reflection 
 of the western display. The phenomenon chang'ed rapidly, 
 arch succeeding arch with changing colours as the sun sank 
 lower and lower. It will be remembered that the phenomenon 
 was by common consent ascribed to volcanic (Just sent forth 
 from an active volcano on the island of Krakatoa, near Java 
 and it was supposed that the dust was belched forth in such 
 enormous quantities that it was carried round and round the 
 World by the Earth's axial rotation. 
 
CHAPTER III. 
 THE MOON. 
 
 Next after the Sun in popular interest. How soon visible after being 
 new. Its phases. Its movement through the heavens. General 
 physical aspects. Its- mountains. The walled plains. The rills. 
 Mountain chains. Isolated peaks. Signs of volcanic action. 
 Resemblance between lunar and terrestrial volcanoes. Names 
 applied to the principal mountains. The so-called seas on the 
 Moon. General appearance of a crater. Changes in their appear- 
 ance owing to the Moon's axial rotation. The motions of the Moon 
 very complex. The Librations. The Harvest Moon. The Hunter's 
 Moon. Brightness of the Moon compared with the Sun. Supposed 
 influence of the Moon on the weaiher. Other influences ascribed 
 to the Moon. The " New Moon in the Old Moon's Arms." In- 
 fluence of the Moon on clouds. Influence of Moonlight on human 
 beings, a fallacy. Some statistics. 
 
 NEXT after the Sun the Moon ranks as the celestial object best 
 known to the inhabitants of the Earth, though we do not, 
 under ordinary circumstances, see it every day. This is 
 owing to the fact that, during the third quarter of the Moon's 
 monthly circuit of the heavens, it only shines when most of 
 us are in bed. Still, it is there for those who choose to rise 
 early, or take rest very late, in order to see it. Indeed, except 
 for a certain number of hours, usually considered for good 
 eyes to be about 30 before or after it is "new," the Moon 
 is visible, weather permitting, throughout the whole of its 
 monthly journey round the Earth as projected on the sky. 
 
 The phases of the Moon that is to say, the ever-changing 
 outline of its illuminated portion are so well known that it 
 
 26 
 
FIG. 39 
 
 PLATE XII. 
 
 The Moon, 
 
FIG. 40 
 
 PLATE XIII. 
 
 The Phases of the Moon. 
 
 f27 
 
THE PHASES OF THE MOON. 27 
 
 seems almost too commonplace to describe them in detail ; but 
 something must be said on the subject. 
 
 Let us start with what is called a " New" Moon, which means 
 that, after the Moon has completed one revolution round the 
 Earth ending with its being lost in the Sun's rays, then, after pass- 
 ing a particular point when Earth, Moon, and Sun are all in a 
 straight line, it emerges from the Sun's rays in the western sky in 
 the evening. Each night thenceforward it gets farther and farther 
 away from the Sun, and day by day becomes more easily visible, 
 until on or about the 7th day it reaches a position we designate 
 as its " First Quarter " (lucus a non lucendo), which means that 
 half of the whole circle of its disc is illuminated, and it is then 
 on the meridian at about 6 p.m. On or about the I4th day, 
 it is " Full Moon," when the whole disc is illuminated and 
 we see a complete circular area of light. The Moon is then 
 on the meridian at midnight. It still proceeds in its easterly 
 course, and the next important stage brings it, at about the 
 2 ist day, to its Third, or, as it is more commonly called, its 
 " Last Quarter.' 3 It is then on the meridian at about 6 a.m., 
 and may be noticed in the W., shining brightly or dimly 
 (dependent on whether the season of the year is winter or sum- 
 mer) at or near the time when it is the ordinary breakfast-hour 
 of the ordinary Englishman. Still moving in the same easterly 
 direction, it will again come into u conjunction" with the Sun 
 on or about the 28th day from which we started ; that is to 
 say, it will again be " New " at or near the time of midday. 
 During, however, speaking roughly, the 26th, 27th, and 28th 
 days it will be shining in broad daylight, and therefore more 
 or less invisible, except that a good eye with a good telescope 
 should be able to see it up to within about 30 hours of actual 
 conjunction, being the 30 hours' interval already mentioned 
 in a previous paragraph. [Fig. 40, Plate XI II.] 
 
 The terms " New," " First Quarter," " Full," " Last Quarter," 
 which have been made use of above are rather in the nature 
 of fancy phrases, though everybody uses them, and they are 
 
28 THE MOON. 
 
 fairly well understood ; but, when employed in connection with 
 the weather, are altogether illusory and meaningless. 
 
 The special attractions of the Moon from the spectacular 
 point of view are its mountains and the other physical features 
 of its surface, including those to which the names of " seas " 
 and " walled plains " have been given. There are also certain 
 clefts or rifts, to which the name of "rills" has been attached, 
 and perhaps we should not be far wrong in regarding these as 
 cracks in the lunar surface. The mountains, however, are the 
 special features of our satellite to deserve, as indeed they 
 receive, the particular attention of the ordinary sightseer. It 
 may be said that, as on the Earth, so on the Moon, the mountains 
 are of two types : chains of mountains and isolated mountains. 
 The character of the former is sufficiently obvious from the 
 name, but the isolated mountains are of a twofold character 
 single peaks, and crater mountains, of which we have, on the 
 Earth, few examples except certain volcanoes. Here we come 
 upon a marked difference between the mountains of the Earth 
 and the mountains of the Moon. Craters on the Earth are 
 the exception, and very few in number ; craters on the Moon 
 are the rule, and in overwhelming numbers. Indeed, this 
 is hardly putting the matter strong enough, because nearly the 
 whole surface of the Moon is made up of crater formations. 
 This fact is especially interesting, because it makes it perfectly 
 clear that, at some past time, the whole surface, as we now see 
 it, took its ultimate shape as the result of volcanic action. 
 If anybody has any doubt about this the doubt must assuredly 
 be removed by comparing, say, a photograph of the Peak of 
 Teneriffe with that of any number of lunar peaks selected 
 promiscuously. 
 
 All the principal lunar mountains have received names, 
 chiefly those of men eminent in science, both ancient and 
 modern. This system of nomenclature dates from the I7th 
 century having been instituted by an Italian astronomer named 
 Riccioli. 
 
FIG. 41 
 
 PLATE XIV. 
 
 *o^<* 
 
 28] 
 
 The Moon's Surface Modelled. 
 
 By James Nasmyth, 1861. 
 
PLATE XV. 
 
 The Lunar Mountain Copernicus (W. H. Pickering, photo). 
 
 [20 
 
DESCRIPTION OF THE MOON'S SURFACE. 29 
 
 In more recent times the greater number of the important 
 mountains have been measured to ascertain their height 
 above the general level of the Moon, above which some of 
 them rise to an elevation of 20,000 ft. The work of 
 measuring these heights was carried out on a large scale 
 more than half a century ago by two German astronomers 
 named Beer and Madler, the value of whose labours has 
 been universally recognised. The work is one of some 
 difficulty owing to the lack of water on the Moon, but it is 
 accomplished by taking observations under special circum- 
 stances of the angular dimensions of the shadows of the 
 mountains whose height it is desired to ascertain. 
 
 The portions of the Moon's surface to which the name of 
 "seas" has been applied were so called originally from their 
 supposed nature ; but it is now quite certain that there is no 
 water on the Moon, and that these areas are in the nature 
 of vast plains like the Steppes of Asia or the deserts of Africa. 
 
 The seas have received very fanciful names, but, as they are 
 commonly referred to by the Latin form of their names, the 
 result is not so irritating as when the English translation is 
 employed. The following are some of the names : Mare 
 Humorum, Mare Imbrium, Mare Nectaris, Mare Serenitatis, 
 Mare Tranquillitatis, and so on. These names, if one does 
 not think to translate them, may pass muster ; but how vapid 
 they sound in their English forms : the Sea of Liquids, the 
 Sea of Showers, the Sea of the Drink of the Gods, the Sea of 
 Serenity, the Sea of Tranquillity unworthy of exact science ! 
 
 A lunar crater usually consists of a sort of basin with a 
 conical elevation rising from the centre, and a raised rim 
 encompassing it. The cases of a crater mountain not having 
 a circular contour are rare ; sometimes, however, a crater 
 may be thought to be elliptical, but this is probably in most 
 eases a perspective effect due to the foreshortening of the 
 crater, which will be one seen near the Moon's limb. 
 
 A verbal description of the appearance and structure of one 
 
3O THE MOON. 
 
 crater would more or less serve to describe every crater, and 
 in real truth no verbal description is worth much ; the craters 
 must be seen either in photographs, or in drawings, or through 
 a telescope for the features, which all of them have more or 
 less in common, to be properly realised. 
 
 In examining the craters by means of a telescope it is im- 
 portant to bear in mind that it is only at the same period in 
 each lunation that is to say, at the same age of the Moon in 
 days that a crater always looks the same. The constant 
 movement of the Moon round the Earth, and consequently 
 the constant changes in the amount of sunshine falling on the 
 Moon, makes the mountains present an incessantly varying 
 appearance. In the case of mountains situated near, but just 
 outside, the terminator (as the line dividing the illuminated from 
 the un illuminated portion is called) the changes in question 
 may often strike an observer, even from hour to hour. The 
 tips, of course, of the mountains may be in sunshine, whilst the 
 adjacent valleys are in shade ; and the size and appearance 
 of the tips are things always changing. At one moment two 
 tips, perhaps, may be visible as bright points, whilst after a 
 short interval a third will become visible ; or, on the other 
 hand, the two tips first seen may become invisible, whilst a 
 new intermediate tip may come into view. 
 
 At or near the epoch of Full Moon it is not much worth 
 while looking at the Moon, so far as a desire to examine its 
 formation in detail is concerned, because, the Sun then shining 
 straight on the full face of the Moon, there will be no shadows. 
 On this account the Moon can best be studied at or near the 
 Quarters, or when the Crescent Moon is sufficiently clear of 
 the Sun. At such times the shadows cast by the mountains 
 will fall to their maximum length on to the adjacent valleys 
 and plains. Be it remembered, of course, that they will point 
 in one direction when the Moon is waxing and in the contrary 
 direction when it is waning. . 
 
 From the point of view of the general reader who only 
 
FIG. -43 
 
 PLATE XVI. 
 
 The Mare Crisium on the Moon. 
 
 From a Dr.uvine bv Professor L. Weinek from a nesrativp tn 
 
FIGS. 44-45 
 
 PLATE XVII. 
 
 [31 
 
LI-BRATIONS OF THE MOON. 31 
 
 aspires to be a sightseer there is not very much more to say 
 with respect to the Moon. To the mathematical astronomer 
 the Moon has given a great deal of trouble from time to time 
 because its motions are exceedingly complex, and it can hardly 
 be said, even now, that the subject has been thoroughly 
 mastered. 
 
 Speaking roughly, we may say that the same hemisphere of 
 the Moon is always turned towards the Earth ; but this is not 
 absolutely true, for, owing to certain physical causes connected 
 with the position of the Moon's axis with respect to the plane 
 of its orbit, and the inclination of that plane to the Ecliptic, 
 the poles of the Moon's axis lean alternately to and from the 
 Earth. Likewise, the Moon's angular velocity in its orbit is 
 subject to a slight variation, in consequence of which a little 
 more of its eastern or western edge is seen at one time than 
 at another. 
 
 Moreover, on account of the diurnal rotation of the Earth, 
 we view the Moon under somewhat different circumstances 
 at its rising and at its setting according to the latitude of the 
 place on the Earth at which we make our observation. 
 
 These three foregoing sets of circumstances give rise to 
 three irregularities called Librations, respectively known as 
 libration in latitude, libration in longitude, and diurnal libra- 
 tion. The general effect of these librations is that, comparing 
 one epoch with another, we see a narrow strip at one time 
 which we do not see at another time. In other words, though 
 we never see more than a complete hemisphere at one time, 
 yet in the course of time we see a whole hemisphere, and a 
 little bit beyond, all the way round. We have, in fact, a sort 
 of surreptitious look round the corner. 
 
 It is commonly stated that the Moon possesses no atmo- 
 sphere, and this is in substance true ; but very refined obser- 
 vations of planets and stars when occulted by the Moon suggest 
 the existence of an atmosphere so infinitesimally small that 
 W. H. Pickering has put it at only ^Vfrth that of the Earth. 
 
32 THE MOON, 
 
 He says: "Although this value seems small, it is by no means 
 insignificant, and would correspond to a pressure of hundreds 
 of tons per square mile of the lunar surface." 
 
 Two expressions connected with the Moon may find a place 
 here. The " Harvest Moon " and the " Hunter's Moon " are 
 both of them well-known phrases more familiar, however, to 
 dwellers in the country than to dwellers in towns. The 
 Harvest Moon is that Full Moon which occurs nearest to 
 the autumnal equinox. As the Moon then rises nearly at the 
 same hour on several successive evenings, and at a point of 
 the horizon almost opposite to the Sun, the duration of its 
 visibility at night is about the maximum possible. The pro- 
 tracted moonlight is often very acceptable to the farmer at 
 that critical period in his agricultural occupations. 
 
 An old iSth-century writer on astronomy named Ferguson 
 thus puts the matter: 
 
 " The farmers gratefully ascribe the early rising of the Full 
 Moon at that time of the year to the goodness of God, not 
 doubting that He had ordered it so on purpose to give them an 
 immediate supply of moonlight after sunset for their greater 
 conveniency in reaping the fruits of the Earth." 
 
 The near coincidence in several successive risings of the 
 Moon takes place in every lunation whenever our satellite 
 is in the signs Pisces and Aries ; but the phenomenon is only 
 prominently noticeable when the Moon is "full" in those 
 signs, and this only occurs at or near the autumnal equinox 
 with the Sun in Virgo or Libra. The Harvest Moon is most 
 useful when it is Full Moon about September 23. The Moon 
 may then rise for two or three nights in succession no more 
 than 10 minutes later each night. Under different circum- 
 stances that is, when the Moon is in Libra, and at or near 
 the descending node of its orbit it may rise as much as i 
 hours later one night than on the preceding night. 
 
 The Full Moon next following the Harvest Moon is called 
 
LUNAR EFFECTS. 33 
 
 the " Hunter's Moon," and will usually fall in October. There 
 does not attach to it the same glamour that attaches to the 
 Harvest Moon, and it is spoken of much less frequently. It 
 is to be presumed that it implies that the operations of hunting 
 will commence at much about the time that this particular 
 Moon displays itself in the heavens. 
 
 There remains to be mentioned an interesting fact in con- 
 nection with the light afforded by the Moon, namely, that we 
 in the Northern Hemisphere get more of it in the winter 
 (when it is most wanted) than we do in the summer (when 
 we can most readily dispense with it). These differences in 
 the availability of the moonlight are due to the fact that it is 
 in the winter that the Moon is found in the most northern 
 part of its orbit, because the Sun at the same time is exactly 
 opposite to it in the most southern part of its (apparent) orbit. 
 The nights of short Moon in winter are also the nights before 
 and after the New Moon when there is the least possible 
 amount of moonlight to lose. 
 
 In summer, for us in the Earth's Northern Hemisphere, the 
 reverse of all this is the case : the Moon's elevation above 
 the horizon is the minimum possible, and the northern hemi- 
 sphere of the Earth therefore receives the minimum amount of 
 moonlight. 
 
 The following quotation from a well-known book by a very 
 well-known man brings under notice the Moon in quite a novel 
 connection : 
 
 " The evening was pleasant, and we dined in the open air. 
 All the valley was very dark. The mountains showed a velvet 
 black. Presently the moon rose. I repress the inclination to 
 try to describe the beauty of the scene, as the valley was swiftly 
 flooded with that mysterious light. All the suitable words 
 have probably been employed many times by numerous writers 
 and skipped by countless readers. Indeed, I am inclined to 
 think that these elaborate descriptions convey little to those 
 who have not seen, and are unnecessary to those who have. 
 Nature will not be admired by proxy. In times of war, how- 
 
 3 
 
34 THE MOON. 
 
 ever, especially of frontier war, the importance of the moon is 
 brought home to everybody. ' What time does it rise to-night?' 
 is the question that recurs ; for other things attacks, ' sniping,' 
 rushes besides the tides, are influenced by its movements." 1 
 
 What is the amount of the light sent to us by the Moon? 
 We buy and sell electric lamps calculated to display so much 
 candle-power. Can we make any analogous calculation with 
 respect to the light of the Moon compared with that of the 
 Sun? Such calculations have been made, but, as was to be 
 expected, there is great discrepancy. More than a century 
 ago Bouger calculated that the Moon's light was only TnnroTnrth 
 that of the Sun ; several more modern estimations make it 
 much less, and the only safe conclusion that one can submit 
 is, that if the whole sky was covered with full moons we should 
 still hardly get the amount of daylight which we owe to the 
 Sun. 
 
 The question of the Moon influencing the weather on the 
 Earth has already been alluded to, but something more must 
 be said. People often remark in common conversation, " Ah ! 
 the Moon changes to-morrow, and we shall have a change of 
 weather." Supposing that on the aforesaid to-morrow the 
 Moon will be reaching its First Quarter, or Eastern Quadrature 
 (to use the proper scientific term), the exclamation quoted is 
 intended to mean that directly the Moon reaches a point in 
 its orbit 90 away from the Sun, whatever has been the weather 
 during the few days before the Moon reaches that point, that 
 weather will be replaced by some other weather. It may as 
 well be stated plainly and broadly that this is absolute non- 
 sense. I will here quote the testimony of two experts on this 
 subject. The late Astronomer Royal, Sir W. H. Christie, in 1896 
 said : 
 
 " It seems doubtful whether the Moon has, or has not, any 
 influence on the weather ; but it is clear that, in any case, it can 
 
 ' W. S. CHURCHILL, M.P., The Malakand Field Foice, 18^7, p. 174. 
 
FIGS. 46-51 
 
 PLATE XVIII. 
 
 341 
 
FIGS. 52-57 
 
 PLATE XIX. 
 
 [35 
 
WEATHER NOT AFFECTED BY]THE MOON. 35 
 
 have but very little influence, as such an influence has never 
 been detected with certainty. The Moon's place is always 
 changing, and there is no warrant for the popular idea that 
 the instants of change are 'new,' 'full,' and 'first' and 'last 
 quarters.'" 
 
 If this pronouncement is not sufficiently emphatic, perhaps 
 another somewhat similar one, taken from a letter from the 
 Meteorological Office in London, may convince a Moon- 
 believer : 
 
 " No one in his senses can believe in the Moon's influence 
 on the weather. The fact that storms move over the surface 
 of the Earth is sufficient to show that, if the change of weather 
 suits the Moon in Ireland, it must fail to suit it in England." 
 
 It is very remarkable how deeply ingrained in the minds of 
 people is the idea that the Moon influences the weather, and 
 that what are very inappropriately called " changes of the 
 Moon" bring about, or are associated with changes in 
 the weather. Most grotesque of all is the idea that it makes 
 a difference in the consequential result whether a so-called 
 "change of the Moon" occurs at one particular hour rather 
 than at another. In real truth the word " change " in this 
 connection is a curious misnomer, which has no astronomical 
 basis ; and neither literally nor even figuratively has the 
 slightest foundation in fact. Perhaps the situation may be 
 brought home to some by asking, Who would suggest that an 
 express train travelling from London to Manchester without 
 stopping at Rugby, and returning via Oxford without stopping 
 at Birmingham, underwent a " change " when it passed through 
 Rugby and Birmingham ? 
 
 Notwithstanding what I have said above, there are a few 
 genuine weather signs which, it may be admitted, are associated 
 with the Moon, but have no physical connection with it. For 
 instance, if the Moon looks pale and the horns blunt, or lack 
 
36 THE MOON. 
 
 sharpness, rain is indicated ; but if the Moon is clear and sharp 
 and silvery bright, so to speak, it is a sign of fine weather which 
 is likely to continue. An old adage which has come down to 
 us in Latin from I know not what date runs thus : "A pale 
 moon indicates rain ; a red moon wind ; a clear moon fair 
 weather." 
 
 It often happens that when the Moon is two or three days 
 old the dim outline ofthe portion not directly illuminated by the 
 Sun can be seen, shining with a pale grey light. This appear- 
 ance is popularly called " the New Moon in the Old Moon's 
 arms," though it would be better to put it the other way about 
 and call it " the Old Moon in the New Moon's arms." The 
 appearance may be taken as a sign of rain, being the equivalent 
 of the clearness of distant hills, which clearness is an almost 
 invariable forerunner of rain. It is sometimes suggested that 
 the question of the effective meaning of this sign depends upon 
 the position of an imaginary line joining the horns relatively to 
 a horizontal or an inclined position ; but nothing depends on 
 this, because the position as regards level of the line joining the 
 horns is simply a matter which depends upon the season of 
 the year as regards the place of the Moon in the heavens with 
 respect to the Sun. [Plate XXII.] 
 
 When the Moon is near its full, either before or after, it fre- 
 quently happens that, as the Moon rises in the sky on a cloudy 
 night, the clouds break up and disperse as the night wears on. 
 I regard this as a well-authenticated fact, which I observed 
 myself many years ago before I knew that Sir J. Herschel had 
 also put it in print, and I may add that I have often noticed it 
 myself since, though Mr. W. Ellis, late of the Greenwich 
 Observatory, once sought to controvert it. It seems to confirm 
 the idea that the Moon imparts a certain but very faint amount 
 of warmth to the Earth, as the direct observations of the late 
 Earl of Rosse distinctly indicate. 
 
 Subject to the foregoing exceptions, it may be said that the 
 following composition of some unknown "poet " (save the mark !) 
 
FIGS. 58-63 
 
 PLATE XX 
 
 36] 
 
FIGS. 64-67 
 
 PLATE XXI. 
 
 Atlas and Hercules. 
 
 The Apennines. 
 
 Alphonsus. Aristarchus. 
 
 Mountains on the Moon (Stuyvearf). [ P . 37 
 
POPULAR DELUSIONS. 37 
 
 correctly represents the facts as regards the Moon and the 
 weather : 
 
 "The Moon and the weather 
 May change together, 
 But change of the Moon 
 Does not change the weather ; 
 If we'd no Moon at all 
 And that may seem strange 
 We still should have weather 
 That's subject to change." 
 
 Besides the question of terrestrial weather, the Moon is credited 
 with other influences, some genuine ; some perhaps genuine, but 
 more likely mythical. The most genuine lunar influence is its 
 effect on the tides of the ocean a subject of sufficient im- 
 portance to demand a separate chapter hereafter. The 
 influence which I have described as perhaps genuine is one 
 which is wholly independent of the so-called changes of the 
 Moon. It is that perhaps it is more often rainy during 
 the increase of the Moon from New to towards Full 
 than from Full to towards New. Moreover, that when 
 the Moon is in perigee, or nearest the Earth, the chances of 
 rain are greater than when it is in apogee, or farthest from 
 the Earth. 
 
 Contrary to the prejudices of most people, perhaps one might 
 say of the great mass of mankind, the epoch of New Moon is 
 the period when changes of weather may be least looked for. 
 The alleged lunar influences which must be regarded as 
 mythical are too many to be recited here. Perhaps the most 
 prominent is that which is enshrined in the word lunatic, which 
 philologically may be taken to imply that the Moon has some- 
 thing to do with people going out of their minds ; but, without 
 going so far as this, one often comes across passages in books 
 the writers of which insinuate that the rays of the Moon exercise 
 a mischievous influence on human beings exposed to them. 
 This is especially an idea current in the East, though! it finds a 
 
38 THE MOON. 
 
 counterpart in ideas met with nearer home. A writer named 
 Carne has remarked : 
 
 " The effect of the Moonlight on the eyes in Eastern Coun- 
 tries is singularly injurious. The natives tell you always to 
 cover your eyes when you sleep in the open air ; indeed, the 
 sight of a person who should sleep with his face exposed to the 
 Moon at night would soon be utterly impaired and destroyed." 
 
 Another writer, named Anderson, speaking of Batavia, is still 
 more thrilling in his language : 
 
 " One must here take great care not to sleep in the beams of 
 the Moon uncovered ; I have seen many persons whose necks 
 have become crooked, so that they look more to the side than 
 forwards." 
 
 A writer of very ancient date, Plutarch, remarked that the 
 light of the Moon causes animal substances to putrefy ; and it 
 is said that Sicilian fishermen cover during the night fish which 
 they expose on the sea- shore to dry, and for the same reason. 
 Even before the time of Plutarch, Virgil, when describing the 
 descent of yEneas into Hades, speaks of the incertam Lunam 
 sub luce malignd, " the Moon's doubtful and malignant light." * 
 The old forest laws of France forbade the felling of trees except 
 during the waning of the Moon, and a Scotch writer, many years 
 ago, stated that peat dug during the increase of the Moon 
 continues moist and never burns clear. 
 
 The writers of a very well-known book 2 make the following 
 statement in it : 
 
 " Lunar influence seems to occasion phenomena of a very 
 curious nature. It is confidently affirmed that it is not unusual 
 for men on board a ship, while lying in the moonlight, with 
 
 1 sEneid, book vi. line 270. I borrow from Milner's Astronomy the 
 translation of "malignant " for malignd ; but Valpy renders it " faint and 
 glimmering," which wholly changes the simile. 
 
 " Voyages and Travels round the World, by the Rev f D. TYERMAN, and 
 G, BENNETT, 
 
STATISTICS. 39 
 
 their faces exposed to the beams, to have their muscles spas- 
 modically distorted and their mouths drawn awry affections 
 from which some have never recovered. Others have been so 
 injured in their sight as to lose it for several months. Fish, 
 when taken from the sea-water, and hung up in the light of the 
 Moon during a night, have acquired such deleterious qualities 
 that, when eaten the next day, the infected food has produced 
 violent sickness and excruciating pains. We have conversed 
 with people who have been themselves disordered after having 
 partaken of such fish. It is hazardous to touch on this subject ; 
 we repeat what we have heard from those who ought to be 
 believed, and who would not affirm that of which they them- 
 selves were not persuaded." 
 
 There is a circumstantial element of good faith in the fore- 
 going quotations, which makes it impossible to disbelieve the 
 facts stated. But where the writers have gone astray, and 
 others have gone astray with them, is in their erroneous explana- 
 tion of real facts. The explanation seems to be this. Animal 
 substances may seem to putrefy, and peat to become moist, and 
 human beings to become subject to bodily ailments when 
 exposed to the light of the Moon, not because of that light, but 
 because owing to the absence of clouds (the sky therefore being 
 clear to permit a full display of moonshine), the radiation of heat 
 from the Earth's surface is facilitated, so that objects, whether 
 animate or inanimate, become colder than the surrounding air ; 
 the deposition of dew is therefore facilitated, and it is the 
 moisture thus engendered which hastens the developement of 
 muscular pains and bodily ailments in animated beings, and 
 decomposition and putridity in inanimate objects. 
 
 The Moon travels round the Earth in 27 days, 7 hours, 
 43 minutes at a mean distance of 237,300 miles. Owing to the 
 fact that its orbit is not a circle but an ellipse, the eccentricity 
 of which is 0*05, it may sometimes be as near to the Earth as 
 221,600 miles, or may recede to as far as 253,000 miles. In 
 consequence of this eccentricity its apparent diameter may vary 
 between 29' 21" and 33' 31". Its diameter at mean distance is 
 
40 THE MOON 
 
 31' 5" ar;d its true diameter is about 2,160 miles. It will be 
 sufficiently near the truth, for popular purposes, to say that its 
 diameter as we see it is about ^, and is therefore about the 
 same, apparently of course, as that of the Sun. Owing to the 
 influence of the Earth's atmosphere the apparent diameter will 
 differ somewhat according as we view the Moon when high 
 up in the sky or low down near the horizon. 
 
CHAPTER IV. 
 THE TIDES. 
 
 The tides matter of interest to the inhabitants of maritime countries. 
 Influence of the Sun and Moon in causing them, Details of this 
 influence. That of the Moon greatly preponderates. Spring Tides. 
 Neap Tides. Daily differences. Range of the tide. " Establishment 
 of the Port." "Priming" and "lagging" of the tides. Equinoctial 
 tides. Tides at the solstices. Tidal irregularities of various kinds. 
 In and around Great Britain. Amongst the South Sea Islands. 
 Influence of the barometer. Journey of the tidal wave round the 
 Earth. The "Bore." 
 
 THE subject of the Tides of the Ocean is a mixed astronomi- 
 cal and geographical one, and it comes so much home to the 
 inhabitants of an island kingdom such as Great Britain and 
 Ireland that it must not be omitted from a volume which 
 appeals to those interested in studying things which they can 
 see. And it follows naturally chapters devoted to the Sun 
 and the Moon, because those two luminaries are jointly con- 
 cerned in causing the tides. 
 
 Diagrams illustrating the theory of the tides appear in every 
 book on astronomy and need not appear here because, as it 
 happens, it is possible to explain the matter without diagrams, 
 which is a thing not always possible in dealing with some 
 scientific problems. 
 
 Let us take, first of all, the case of the Moon. The Moon is 
 the Earth's satellite, and as such is primarily responsible for the 
 tides, though, as we shall see presently, the Sun is also con- 
 cerned in a lesser degree. 
 
 4* 
 
42 THE TIDES. 
 
 The Moon, being the Earth's satellite, is in a sense held in 
 its place by the attraction of the Earth ; but there is a certain 
 amount of mutuality in the matter that is to say, though the 
 Earth attracts the Moon, the Moon has a slight attractive 
 power on the Earth, but it does not suffice to do much more 
 than attract the water on the Earth, because the water is 
 mobile. This is only half the truth, for the Moon does draw 
 the Earth to a slight extent ; but in doing so the water on 
 exactly the opposite side is left behind, in a sense heaped up. 
 Thus it comes about that, whilst it is high-water when the 
 Moon is on, or near the meridian of the place of observation, 
 there is also a condition of high-water on the opposite side of 
 the Earth 180 removed in longitude from the meridian just 
 spoken of. In other words, the coincident tides are separated 
 from each other by 180, or by half the circumference of our 
 globe. Since the diurnal rotation of the Earth on its axis 
 thus causes the tidal waves to pass successively right round 
 the Earth once in about every 24 hours it follows that as there 
 are two tidal waves constantly in motion, there are everywhere 
 two high tides daily, with an interval of about 12 hours 
 between them. 
 
 Now let us consider the influence of the Sun as brought into 
 the matter. Though the mass of the Sun is so very much 
 greater than the mass of the Earth, there are two reasons why 
 the power of the Sun to raise or develope tides on the Earth 
 is much less than its preponderating mass would lead us to 
 suppose. Firstly, the greater distance of the Sun from the 
 Earth, compared with the distance of the Moon from the Earth, 
 diminishes the power of the Sun compared with what it would 
 be were the distances on an equality ; and, secondly, the 
 developement of the tides is due solely to the inequality of the 
 attractions in operation on different sides of the Earth, so that 
 the greater the inequality the greater the resulting tide and 
 vice versa. The mean distance of the Earth from the Sun is 
 about 11,720 diameters of the Earth, and consequently the 
 
THE THEORY OF THE TIDES. 43 
 
 difference between the distance of the Sun from one side of 
 the Earth compared with the other will be only Trhtfth of the 
 whole distance. But in the case of the Moon, whose mean 
 distance is only 30 diameters of the Earth, the difference 
 between the distance from one side compared with the distance 
 on the other side will be -sVth of the whole distance. 
 
 Inasmuch, therefore, as the height of the tidal wave depends 
 on the inequality of the attraction and the inequality being in 
 the case of the Moon represented by A, whilst in the case 
 of the Sun it is only TTTSTD the preponderance of the influence 
 of one of these two bodies over the other is obvious. Worked 
 out mathematically it was calculated by Newton to be about 
 2 to i. 
 
 Thus far we have been supposing the Sun and Moon to 
 be pulling together, but they only do that when they are in the 
 same straight line, which is when the Moon is what we call 
 New or Full. But when the Moon is in quadrature, or |th 
 or fths of the way round in its orbit, reckoned from the stage 
 known as New or Full, then Sun and Moon do not pull to- 
 gether, and the resulting tide is only that due to the surplus 
 influence of the Moon over that of the Sun ; in other words, 
 the resulting tide is a much smaller one than when they pull 
 together. This explains the contrast which all residents on 
 the sea-coast can realise between the high and low-water 
 marks which they observe at the epochs of New and Full 
 Moon compared with the rise and fall of the tides at the 
 Quarters. The former tides go by the name of "spring 
 tides," and give rise to the highest possible and lowest possible 
 high-water and low-water marks respectively. The latter are 
 known as " neap tides," and result in only a moderately high- 
 water mark and a moderately low-water mark. The physical 
 cause of these last-named circumstances will now be easily 
 understood, for, whilst Spring Tides depend upon Sun, Moon, 
 and Earth being all the same straight line, in the Neap Tides 
 the Moon's attraction acts along a line perpendicular to that of 
 
44 THE TIDES. 
 
 the Sun ; in other words, the two bodies partly neutralise one 
 another's action. 
 
 All the foregoing remarks have been based on the assump- 
 tion (which is baseless), namely, that the Earth is a sphere 
 covered all over by a layer of water of uniform depth ; but it 
 is convenient to give the explanation on this assumption in 
 order to make the matter more easily intelligible, and for this 
 same reason the following propositions are framed on the 
 same supposition, to be modified by subsequent explanations. 
 
 1. On the day of New Moon, Sun and Moon cross the 
 meridian at the same time, namely, at noon ; then, after an 
 interval, high-water occurs. Then the water begins to fall for 
 6 hours 12 minutes till it reaches its lowest position ; it then 
 rises for 6 hours 12 minutes to a second maximum ; then falls 
 for another interval of 6 hours 12 minutes, and rises again 
 during a fourth interval of 6 hours 12 minutes. It has, there- 
 fore, two maxima and two minima in a period of 24 hours 
 48 minutes, which is called a " tidal day." The foregoing 
 intervals are not quite correctly expressed, even in theory, for 
 the water usually takes a longer time in falling than it does 
 in rising, as may be noticed by any one sitting on the sea- 
 shore. 
 
 2. On the day of Full Moon the Moon crosses the meridian 
 12 hours after, the Sun, namely, at midnight, and the tidal 
 phenomena are the same as stated in the previous paragraph. 
 
 3. As time is reckoned by the apparent motion of the Sun, 
 the solar tide always happens at the same hour l at the same 
 place ; but the lunar tide, which is the greater, and therefore 
 gives a character to the whole, happens 48 minutes later 
 every day. It therefore separates eastwards from the solar 
 tide at that rate, and becomes later and later till, at the First 
 and Third Quarters of the Moon, it happens at the same time 
 
 1 I ignore here the question of the difference between apparent solar time 
 and mean solar time and the customary adjustment of these times by what is 
 called in the almanacks the " equation of time." 
 
DETAILS AS TO THE TIDES. 45 
 
 as the low-water of the solar tide : then the elevation of the 
 high- water and the depression of the low will be the difference 
 of the solar and lunar tides, and the condition of things will be 
 represented by the term Neap Tide. 
 
 4. The difference in height between high and low-water is 
 called the " range of the tide," .and obviously may be measured 
 in two ways : either horizontally along the shore or vertically on 
 a post of suitable height, and suitably placed for the purpose. 
 The former principle of measurement would be the one adopted 
 by an unscientific seaside visitor, but the latter will often be 
 noticed as measurable by numbered marks on the columns 
 supporting a pier, or painted on the upright wall of a jetty or 
 breakwater. 
 
 5. The Spring Tides are the highest, especially those which 
 happen 36 hours after the New or Full Moon. 
 
 6. The Neap Tides are the lowest, especially those which 
 happen 36 hours after the Moon is at one of its quarters, or in 
 quadrature, to speak scientifically. 
 
 7. The interval of time between noon and the time of high 
 water at any particular place is the same on the days both of 
 New and Full Moon. The precise moment of high-water at 
 any place when the Moon is New or Full is called by French 
 writers IJetablissement du port, and that expression has now 
 been brought into use in English as the " Establishment of the 
 Port," an awkward phrase which in itself conveys no meaning 
 till explained. 
 
 The fact that an interval of time elapses at any given place 
 between the meridian passage of the Moon and the time of 
 high-water is due to another fact, namely, that the waters of the 
 oceari are retarded by friction whilst they are in motion over 
 the solid surface of the Earth ; and so it comes about that both 
 the lunar and the solar tidal waves are not found immediately 
 under their respective luminaries, but follow them at a certain 
 distance. Moreover, the tidal wave is affected in another way 
 by the action of both these luminaires, and at certain periods 
 
46 THE TIDES. 
 
 of the lunar month the progress is either accelerated or 
 retarded. During the First and Third Quarters the solar tide is 
 W. of the lunar one ; and consequently the actual high-water 
 due to the combination of the two waves will be to the W. of 
 the place at which it would have been if the Moon were acting- 
 alone ; accordingly the time of high-water will be accelerated. 
 On the other hand, in the Second and Fourth Quarters the Sun 
 produces a retardation in the time of high-water. These effects 
 are called the " priming " and " lagging ; ' of the tides, and the 
 effect is to derange the average retardation, which from a mean 
 value of 48 minutes may be augmented to 60 minutes or 
 be reduced to 36 minutes. It follows from this that a sea- 
 bather who is watching for a chance of getting sand and not 
 stones for his foothold, and on a certain day does just escape 
 the stones, will not of necessity on the next day find himself 
 exactly in the same pleasant position at a moment which is 
 exactly 48 minutes different from the time shown by his watch 
 on the previous day. 
 
 The highest Spring Tides occur when the Moon passes the 
 meridian of the place of observation about i| hours after 
 the Sun, for then the maximum effects of the two luminaries 
 coincide. 
 
 The height of the tides is affected by another consideration 
 the positions of the Moon and the Sun with respect to the 
 Equator ; the nearer these two bodies are to the Equator the 
 greater the height of the tide. Twice a year, at what we call 
 the Equinoxes that is to say, about March 21 and September 22, 
 speaking roughly the Sun is actually in the Equator. If at 
 these dates the Moon should be in or near the Equator the 
 tides will be the highest possible. Such tides are spoken of 
 as the Equinoctial Spring Tides. On the other hand the 
 smallest tides will occur at about the Solstices (June 21 and 
 December 22) if the Moon attains its least or its greatest 
 meridian height at the same time as the Sun. 
 
 Finally, the distances of the Earth from the Moon and the 
 
DETAILS OF THE TIDES. 47 
 
 Sun also affect the height of the tides. Other things being- 
 equal, the height of a tide is greater or less according as the 
 Moon and the Sun are near to or far from the Earth. 
 Accordingly the tides at or near December 22 are higher 
 than those at or near June 21, the Earth being nearest to the 
 Sun (perigee being in January) and farthest from the Sun in 
 June (apogee being in July). 
 
 Thus far in our consideration of the tidal wave we have 
 been keeping up the fiction, already referred to, of the Earth 
 being a ball of solid matter with a smooth surface and covered 
 all over with a layer of water of even depth everywhere. It 
 needs not to be pointed out that this is pure fiction, some 
 parts of the Earth being land and other parts being water, the 
 two being distributed most irregularly, and the bottom of the 
 Ocean everywhere being of varying depth, just as the elevation 
 of the land is everywhere of varying height. 
 
 These facts have a most distracting influence on the times 
 and circumstances of the movements of the Earth's water ; 
 and though the rotation of the Earth on its axis and the 
 movements of the Moon and of the Sun all co-operate in 
 imparting a motion of translation, so to speak, to the Oceans 
 of water which exist on the Earth, local circumstances entirely 
 destroy the theoretical conditions. In other words, the actual 
 phenomena of the tides are exceedingly complicated, and 
 incapable of being defined by cast-iron rules because of the 
 irregular outline of the land, the uneven surface of the bed 
 of the ocean, and the action of winds and of currents of air 
 and currents of water, and so on. 
 
 The effect of all these disturbing influences cannot be better 
 brought home to the mind than by a consideration of the 
 following details. If the surface of the Earth were entirely 
 covered by the hypothetical layer of water mentioned on a 
 previous page, the height of a tide raised by the Sun's attrac- 
 tion would be i ft. ii in., and of a lunar tide 4ft., but the 
 difference in the level of the waters in the ocean due to the 
 
48 THE TIDES. 
 
 disturbing causes just spoken of <are, in the vast number of 
 cases, entirely different, and in excess of these figures. In 
 deep estuaries or creeks ending in narrow channels, which 
 gradually converge inwards as a common wine-funnel does, 
 the range is very much greater than along an open shore. 
 For instance, in the Bristol Channel, off Chepstow, the range 
 of rise and fall is as much as 38 ft., and in some similar 
 situations in foreign countries the range is even greater. 
 
 I once had an opportunity of standing on the shore of the 
 Bristol Channel on the Gloucester side of Chepstow, and the 
 rapidity with which landmarks such as piles and rocks, near 
 and around which I had walked a few minutes previously, were 
 submerged, and deeply submerged, was very striking to me, 
 whose experience of the rise and fall of the tides was limited 
 to open shores on the South and East of England. 
 
 Along open shores the rise and fall, measured in feet, are 
 comparatively limited, especially where promontories or head- 
 lands jut out into the sea. Thus, at the Needles in the Isle of 
 Wight, the range is only 9 ft., whilst at Weymouth it is even 
 less, being only 7 ft. On flat shores which bound large open 
 expanses of water such as the Atlantic and Pacific Oceans, and 
 confined seas like the Mediterranean, the elevation of the 
 tidal wave is to be measured rather by inches than by feet. 
 Thus at Toulon it is I ft. ; at St. Helena 3 ft. 
 
 The barometric pressure of the atmosphere is also a factor 
 to be taken into account in considering the probable range of 
 the tide at a given place and at a given time. When the 
 barometer is low an unusually high tide may be expected, and 
 vice versd ; and it has been estimated that a depression of 
 i in. in the column of mercury in the barometer has at the 
 London Docks the effect of raising the level of the tidal water 
 by the amount of 7 in., which at Liverpool would, be 10 in. 
 Thus it would come about that, supposing an unusual high 
 tide in the Thames (as has happened) brought the water up 
 to the level of the masonry of the Thames Embankment, a 
 
ABNORMAL TIDES. 49 
 
 sudden fall of the barometer might unexpectedly bring the 
 water over on to the highway, though no such risk had been 
 previously contemplated. The influence of the wind also 
 cannot be left out of account, for it is often very potential 
 either in aggravating the destructive, effects of a very high tide 
 or of checking them. 
 
 It is in the Pacific Ocean and among the South Sea Islands 
 that the most extraordinary anomalies in connection with the 
 tides are to be observed. Many travellers and navigators who 
 have performed voyages in those parts of the world have 
 recorded their strange experiences. I have come across many 
 such records, and transcribe the following as the most recent 
 which I have seen : 
 
 " This is, so far as I know, the only part of the world [Tahiti] 
 where the tide is high but once a day, and regularly at the 
 same hour between i and 2 o'clock in the afternoon. The 
 rise and fall does not exceed i ft. There must, I suppose, be 
 a corresponding movement of the sea after midnight. It may 
 be so slight that the regular evening breeze retards and 
 renders it imperceptible. I have often questioned nautical 
 men on the subject, but I have not been able to elicit any 
 satisfactory explanations : nor do Nautical Almanacs, nor the 
 sailing instructions issued by the Hydrographic Department, do 
 more than chronicle the extraordinary fact." l 
 
 The following description of the course of the general tidal 
 wave of the Earth is so clear and concise that it can neither 
 be improved upon nor be abridged. I therefore quote it in 
 full :.- 
 
 " The Antarctic is the cradle of tides. It is here that the Sun 
 and Moon have presided over their birth, and it is here, also, 
 that they are, so to speak, to attend on the guidance of their 
 own congenital tendencies. The luminaries continue to travel 
 round the Earth (apparently) from east to west. The tides 
 no longer follow them. The Atlantic, for example, opens to 
 
 1 E. REEVES, Broivn Men and Women ; or, the South Sea Islands, p. 381, 
 London, 1898. 
 
5O THE TIDES. 
 
 them a long, deep canal, running from north to south, and, 
 after the great tidal elevation has entered the mouth of this 
 Atlantic canal it moves continually northward ; for the second 
 12 hours of its life it travels north from the Cape of Good 
 Hope and Cape Horn, and at the end of the first 24 hours of 
 its existence has brought high-water to Cape Blanco on the 
 west of Africa and Newfoundland on the American continent. 
 Turning now round to the eastward, and at right angles to 
 its original direction, this great tidal wave brings high-water, 
 during the morning of the second day, to the western coasts of 
 Ireland and England. Passing round the northern cape of 
 Scotland, it reaches Aberdeen at noon, bringing high-water 
 also to the opposite coasts of Norway and Denmark. It has 
 now been travelling precisely in the opposite direction to that 
 of its genesis, and in the opposite direction, also, to the relative 
 motion of the Sun and Moon. But its erratic course is not yet 
 complete. It is now travelling from the northern mouth of 
 the German Ocean southwards. At midnight of the second day 
 it is at the mouth of the Thames, and wafts the merchandise 
 of the world to the quays of the port of London. In the course 
 of this rapid journey the reader will have noticed how the lines 
 [on the map] in some parts are crowded together closely on 
 each other, while in others they are wide asunder. This 
 indicates that the tide-wave is travelling with varying velocity. 
 Across the Southern Ocean it seems to travel nearly 1000 miles 
 an hour, and through the Atlantic scarcely less ; but near some 
 of the shores, as on the coast of India, as on the east of Cape 
 Horn, as round the shores of Great Britain, it travels very 
 slowly ; so that it takes more time to go from Aberdeen to 
 London than over the arc of 120 which reaches from 60" of 
 southern latitude to 60 north of the Equator. These differ- 
 ences have still to be accounted for; and the high velocities 
 are invariably found to exist where the water is deep, while 
 the low velocities occur in shallow water. We must therefore 
 look to the conformation of the shores and bottom of the sea 
 as an important element in the phenomena of the tides." l 
 
 Theoretically, if the whole Earth were uniformly covered 
 with water, the average velocity of the tidal wave round the 
 
 1 JOHNSON, Physical Atlas. 
 
TIDES ON THE ENGLISH COAST. 51 
 
 Earth would be rather more than 1000 miles per hour, and 
 the writer of the foregoing extract seems to think that this 
 velocity is nearly reached in the Southern Ocean, where there 
 exists a vast stretch of water not broken in upon by any 
 important masses of land. 
 
 Though 1 have mentioned the islands of the Pacific as 
 localities where special anomalies exist in connection with the 
 tides, it must not be forgotten that much nearer home, to wit 
 on the coasts of Hampshire and the Isle of Wight and some 
 other localities, some strange departures from the normal con- 
 dition of things tidal are often exhibited. In the case of Hamp- 
 shire, owing to the fact that the tides in the Solent and at 
 Spithead do not run easterly on the flood and westerly on 
 the ebb, as is the case in the open Channel, but run from 
 
 Half-flood to half-ebbeasterly, 
 Half-ebb to half-floodwesterly 
 
 Southampton and places up Southampton Water have four 
 tides in the 24 hours instead of two, so that, after flowing to 
 half-flood, and filling up with the west-travelling tide, when the 
 tide changes outside Calshot Castle, there is a slack and a 
 partial ebb, until the eastern tide brings enough water to push 
 the flood home to its full. Likewise on the ebb, when the tide 
 changes, there is a slack and slight flow, until the suction of 
 the west-going tide draws the water away down Channel. 1 
 
 The situation of the Isle of Wight as an island opposite an 
 estuary may, no doubt, be taken to suggest that similar tidal 
 vagaries exist elsewhere in the world. 
 
 As regards anomalies elsewhere in the British Isles, it is 
 stated by a Scotch writer who studied very closely the geo- 
 graphical circumstances of the West of Scotland that in the 
 strait between the island of Isla and the islets of Chenzie and 
 
 1 I owe the foregoing account of the tides in the Solent to Mr. C. G. Brodie, 
 F.R.A.S., an experienced yachtsman, and I have never seen this information 
 in print. 
 
52 THE TIDES. 
 
 Oersa the time occupied by the ebb-tide out of the theoretical 
 12 hours is lof hours, whilst the flood-tide occupies only i| 
 hours. 
 
 The last matter to be mentioned in connection with the tides 
 is the striking and remarkable phenomenon which, bearing 
 various local names, is commonly called in English a " Bore." 
 It is to be seen only at the mouths of rivers which contract at 
 a sharp angle from a wide estuary to a narrow channel, and 
 happens only when a spring-tide of unusual height rushes 
 up the estuary into the narrow channel, carrying all before 
 it with a great roar. 
 
 From all accounts the bore on the river Tsien-Tang-Kiang, 
 in China, must be regarded as one of the most remarkable in 
 the world ; and there is the further fact attaching to it, that 
 it has been made the subject of a very full and complete 
 scientific investigation by a thoroughly competent observer, 
 Admiral W. U. Moore, whose account was communicated in 
 1889 to the Institution of Civil Engineers. His remarks are 
 so usefully comprehensive that a summary of them will make 
 my account of bores in general much more complete than it 
 could otherwise have been. [Plate XXXIII.] 
 
 To begin with the name "bore." The Admiral ascribes 
 it to an Icelandic word meaning "billow." It is also called in 
 England the "hygre," and "eagre"; also "egre." The 
 Admiral derives '" eagre " from the French " eau-guerre," or 
 " water-war," which sounds ingenious, whether authentic or not. 
 In France it is known as the " mascaret," and in Brazil as 
 the " pororoca." It seems to occur in 6 or 8 rivers in the 
 British Isles, including the Severn, the Wye, the Trent, and 
 the Solway ; in two or three French rivers namely, the Seine, 
 the Garonne, and the Loire ; in some of the Indian rivers, 
 including the Ganges, the Brahmaputra and the Indus ; in 
 the branches which compose the mouth of the Amazon in 
 S. America ; and in one river at least in China. It is rarely 
 observed except at a spring-tide, and as a rule shows itself 
 
THE 
 
 53 
 
 on the days of Full and New Moon, appearing with the first 
 of every flood-tide for 3 or 4 days succeeding those phases ; 
 after which the tide comes in with only a swift rush unaccom- 
 panied by noise or violent commotion. 
 
 The 3 following conditions appear to be necessary to create 
 a bore : 
 
 1 . A swiftly flowing river. 
 
 2. An extensive bar of sand, dry at low-water, except in 
 certain narrow channels kept open by the outgoing stream. 
 
 3. The estuary into which the river is discharged must be 
 funnel-shaped, with a wide mouth which is open to receive 
 the tidal wave coming in from the Ocean. 
 
 If either of these 3 conditions is wanting there will be no 
 bore. For example, in the case of the Thames, the third 
 condition exists, but the first and second are wanting ; for the 
 Thames is not a swift river, and has no bar, dry at low-water. 
 In the Severn all 3 conditions are found, and accordingly 
 there is a bore ; not a very large one, it is true, but still the 
 most noteworthy in the British Isles. 
 
 The bore of the Tsien-Tang-Kiang has all 3 conditions 
 well developed. The estuary into which the river falls has a 
 vast area of sand at its head, and is favourably situated for 
 the reception of the incoming tidal wave from the Pacific. 
 The range of the tide immediately outside the Hang-Chau 
 Gulf is 12 ft., but as the wave becomes compressed in advancing 
 towards its head at the end of the navigable waters, it is as 
 much as 25 ft. at ordinary spring-tides, and 34ft. when there 
 is the favourable combination of a wind blowing on shore, and 
 a Moon in perigee at the time of Full or New. The navigable 
 breadth of the estuary at its head (where the tidal wave rises 
 to its greatest height) is about ith or -|th of what it is at the 
 mouth ; and if there were no river discharging into the bay 
 the range would probably be 60 ft. or 70 ft., as in the Bay of 
 Fundy. 
 
 The speed of the advancing tidal wave was measured by the 
 
54 THE TIDES. 
 
 officers of H.M.S. Rambler, and found to be 14^ statute miles 
 an hour. The breadth of the bore is about I mile, and its 
 front presents the appearance of a gleaming white cascade of 
 bubbling foam, 8 ft. to 12 ft. in height. The noise is not the 
 least impressive feature of this phenomenon. On a calm still 
 night it can be distinctly heard 14 or 15 miles off, and more 
 than an hour before it arrives. The noise increases very 
 gradually until the bore comes abreast of an observer on the 
 bank of the river, when he has to endure a roar but little 
 inferior to that of the Rapids below Niagara. 1 
 
 South America seems to offer an example of a bore of a very 
 remarkable character. The following description of a bore on 
 the river Amazon penned by La Condamine a great many 
 years ago is a fitting pendant to Admiral Moore's account of 
 the Tsien-Tang-Kiang bore : 
 
 " During three days before the New and Full Moons, the 
 period of the highest tides, the sea, instead of occupying six 
 hours to reach its flood, swells to its highest limit in one or 
 two minutes. The noise of this terrible flood is heard five or 
 six miles off, and increases as it approaches. Presently you 
 see a liquid promontory 12 or 15 feet high, followeid by 
 another, and another, and sometimes by a fourth. These 
 watery mountains spread across the whole channel, and advance 
 with a prodigious rapidity, rending and crushing everything in 
 their way. Immense trees are sometimes uprooted by it, 
 and sometimes whole tracts of land are swept away." 
 
 1 Abridged and added to from Admiral Moore's paper in the Minutes of 
 Proceedings of the Institution of Civil Engineers, Session 1889-90, vol. xcix. 
 Part I. A still more detailed account will be found in the Journal of the China 
 Branch of the Royal Asiatic Society, vol. xxiii. 1888. See also Sir G. H. 
 DARWIN'S Treatise on Tides. 
 
CHAPTER V. 
 THE PLANETS GENERALLY. 
 
 What the planets are. May be conveniently divided into two groups. 
 The Inferior Planets. The Superior Planets. The Minor Planets. 
 Certain planets have satellites. The purpose served by them. 
 Certain planets have phases. The planets in Conjunction. The 
 planets in Opposition. Transits across the Sun. Characteristics 
 common to all the planets. Statement of these by Hind. Kepler's 
 Three Laws. Sir J. HerscheVs statement. Conjunction of two 
 planets. Instances of this. Various discarded planetary systems. 
 Suggested I ntr a- Mercurial and Trans- Neptunian planets. 
 
 ROUND the Sun, as a centre, there circulate a considerable 
 number of bodies which we call planets l : these are now 
 known to be, indeed, many hundreds in number, but we can 
 count on our fingers those which alone are worthy of 
 general attention. Those which are known to everybody and 
 which have been recognised as planets from the earliest times 
 are still fewer in number, and comprise only Mercury, Venus, 
 the Earth, Mars, Jupiter, and Saturn. For the purposes of 
 astronomy the Earth, though strictly a planet in the proper 
 sense of the word, may be left out of consideration, because 
 we, being on the Earth, cannot approach its study in the same 
 way in which we deal with the other planets just named. The 
 study of the Earth concerns the sciences of geography and 
 geology in particular, and, except for the purpose of noting its 
 place in the solar system, because it is one of the cortege of 
 
 1 Greek, TrAaKJjTijs, a wanderer, 
 55 
 
56 THE PLANETS GENERALLY. 
 
 planets which travel round the Sun, the astronomer has not 
 much concern with it. He uses it, however, for the arbitrary 
 purpose of separating the planets into two groups, putting into 
 one group those which are nearer the Sun than the Earth and 
 into the second group all the other planets outside the orbit of 
 the Earth. 
 
 The former are called " Inferior " planets, and, so far as we 
 know, are only two in number, namely, Mercury and Venus : 
 the others are called " Superior " planets, and include not only 
 the other three named above (Mars, Jupiter, and Saturn), but 
 two other large planets still farther off, Uranus and Neptune, 
 together with some 700 miscellaneous planets known as the 
 " Minor " planets, which circulate round the Sun in orbits 
 lying between Mars and Jupiter. 
 
 It will be readily understood, from what has just been said, 
 that the designations "Inferior" and "Superior" are not a 
 little misleading, because both the Inferior planets are very 
 much larger than nearly all the Superior ones, reckoned in 
 respect of their numbers. 
 
 There is another important distinction between the two 
 classes of planets. The Inferior ones have no satellites, whilst 
 all the large Superior ones are provided with attendants^ 
 which are called satellites, though frequently spoken of as 
 "moons," because serving the purposes served by our Moon. 
 This distinction, as regards the possession or non-possession 
 of satellites, may possibly be ascribed to design on the part 
 of the Creator. Mercury and Venus, being so comparatively 
 near to the Sun, do not need the benefit afforded by a satellite 
 in the way of supplementary light. The Earth, as we have 
 seen, is so favoured by having a companion to afford additional 
 light, and probably it may be said with truth that, as all the 
 other Superior planets have satellites, and, with the exception 
 of Neptune, satellites greater in number than the Earth has, 
 such satellites may be regarded as performing the special office 
 of supplying in some degree to their primaries light by way 
 
MOVEMENTS OF THE PLANETS. 57 
 
 of compensation for the limited amount of Sunlight which they 
 receive because of their vast distance from the Sun. There 
 is another important distinction between the Inferior and 
 Superior planets. The former are subject to phases which 
 are identical in character with the phases of the Moon 
 Crescents, Quarters, Full, and so on ; whilst the Superior 
 planets, with the exception of Mars and Jupiter (in a slight 
 degree), exhibit no appreciable phases. 
 
 The phases of Mercury and Venus involve the consequence 
 that they pass round the Sun, sometimes on this side of the 
 Sun looked at from the Earth, and sometimes on the farther 
 side of the Sun. When passing on our side, then, at the 
 moment at which Earth, planet, and Sun are exactly in the 
 same straight line, the planet is said to be in "Conjunction" 
 with the Sun. When on the opposite side, with the Earth, Sun 
 and planet in the same straight line, the planet is said to be in 
 " Opposition." A moment's thought will make it evident that 
 when in these two positions (and also, unless they are at a 
 certain distance, on either side) the planets will be lost in 
 the Sun's rays, and will therefore be invisible to us. 
 
 There is one exception to the rule of these planets being 
 invisible when in Conjunction, and that is when either of them 
 is in a straight line, so disposed that the planet may be seen 
 actually on and passing across the Sun's disc. This pheno- 
 menon, which is rare, constitutes what is called a " transit " of 
 the planet. But the consideration of this in detail belongs to 
 a later chapter. 
 
 The circumstances of the Superior Planets are altogether 
 different. They never can be in Conjunction with the Sun in 
 the same sense that the Inferior Planets can be, because they are 
 always going round the Sun in orbits outside that of the Earth. 
 The epoch of Conjunction with them puts them in a straight 
 line but in a different order, namely, in the order of Earth, Sun, 
 Planet. When this happens they are invisible from the Earth 
 because lost in the Sun's rays ; and that state of things subsists 
 
58 THE PLANETS GENERALLY, 
 
 for a certain length of time before and after Conjunction, 
 dependent on the brilliancy of the particular planet and our 
 optical means to view it when immersed to some degree in 
 the Sun's rays, which means in some degree of twilight. 
 
 The Superior Planets are also on occasions in Opposition, 
 but here again the term has not quite the same meaning as it 
 has when applied to an Inferior Planet. An Inferior Planet is, 
 as we have seen, lost in the Sun's rays ; but a Superior Planet 
 is at its very best, so far as the Sun is concerned, when in 
 Opposition, because it is on the meridian at midnight when the 
 Sun is on the meridian at midday, the order of position being 
 Sun, Earth, Planet. 
 
 The only Superior Planet subject to a clearly evident phase 
 is Mars, which in two positions in its orbit (Quadratures, 
 E. and W.) suffers a slight encroachment first on one side 
 and then on the other side of its disc. Theoretically, Jupiter 
 should exhibit a slight phase under analogous conditions, but 
 it is not very easy to appreciate it ; still, it must be deemed, 
 when at its quadratures, to be slightly gibbous (as the term is), 
 but much less so than Mars. The defalcation of the light is 
 on the limb of the planet which is farthest from the Sun. 
 
 There are certain characteristics common to all the planets, 
 which have been stated by Hind in the following terms : 
 
 i. They move in the same invariable direction round the 
 Sun, their course, as viewed from the N. side of the 
 Ecliptic, being contrary to the motion of the hands of a 
 watch. 
 
 2. They describe oval or elliptical paths round the Sun, not, 
 however, differing greatly from circles. 
 
 3. Their orbits are more or less inclined to the Ecliptic, and 
 intersect it in two points, which are the " Nodes," one half of 
 the orbit lying N. and the other half S. of the Earth's path. 
 
 4. They are opaque bodies, like the Earth, and shine by 
 reflecting the light which they receive from the Sun. 
 
 5. They revolve upon their axes in the same way as the 
 
THE ORBITS OF THE PLANETS. 
 
 59 
 
 Earth. This, we know by telescopic observation, to 
 
 case with many planets, 
 
 and, by analogy, the rule 
 
 may be extended to all. 
 
 Hence they will have the 
 
 alternation of day and 
 
 night, like the inhabitants 
 
 of the Earth ; but their 
 
 days are of different lengths 
 
 to our own. 
 
 6. Agreeably to the 
 principles of Gravitation, 
 their velocity is greatest at 
 those parts of their orbits 
 which lie nearest the Sun, 
 and least at the opposite 
 parts which are most 
 distant from it ; in other | 
 words, they move quickest > 
 in perihelion and slowest 
 in aphelion. 
 
 Although the matter is 
 somewhat technical', I 
 think it well to mention 
 here, in order to make I 
 these general statements | 
 complete, the laws regu- w 
 lating the movements of | 
 the planets which * 
 bear the name of Kepler. 1 
 They may be stated as s 
 follows : 
 
 I. The planets move in "g 
 ellipses, having the Sun "* 
 in one focus. 
 
 be the 
 
6o 
 
 THE PLANETS GENERALLY. 
 
 2. The radius-vector of each planet describes equal areas in 
 equal times. 
 
 3. The squares of the periodic times of the planets are 
 proportional to the cubes of their mean distances. 
 
 These laws hold good for all the planets, and also for all 
 their satellites relatively to their respective primaries. 
 
 A few words may be added to make these laws a little more 
 clear to the non-mathematical reader. Everybody understands 
 
 what the centre 
 of a circle is, 
 and that from 
 the centre 
 every part of 
 the circumfer- 
 ence is equi- 
 distant; but, in 
 the case of an 
 ellipse, there 
 is no point 
 inside it which 
 is equidistant 
 from the cir- 
 cumference ; 
 and, in order 
 to draw such a 
 figure, one 
 
 must make use of two points inside. Each of these points is 
 called a "focus." 
 
 A radius-vector is an imaginary line drawn from the Sun to 
 a planet at the circumference of the ellipse which constitutes 
 the planet's orbit. The statement that the radius-vector of 
 each planet describes equal areas in equal times will be best 
 grasped by an inspection of Fig. 71, where the shaded portions 
 represent equal areas, whilst the distances along the circum- 
 ference, though very unequal in extent, are yet traversed by the 
 
 Fig. 71. Diagram illustrating Kepler's 
 Second Law. 
 
KEPLER'S LAWS. 
 
 6t 
 
 planet in equal periods of time. Such is the case because every 
 planet moves faster when nearest the Sun than it does when 
 farthest oft" from the Sun. 
 
 Kepler's Third Law involves a curious point : if the dis- 
 tance of the Earth from the Sun be taken as unity (To), and its 
 period taken in days, then if the squares of the periods of the 
 planets be divided by the cubes of their mean distances from 
 the Sun, the result in quotients will be the same substantially 
 for all the planets, the slight discrepancies in the quotients 
 being due to inexactness in the observations on which the 
 calculations are based. 
 
 This law applies to all the satellites, so that an identical 
 quotient will be obtained for each group of satellites, though, 
 comparing one group with another, the quotients will vary 
 inter se. 
 
 The foregoing statement, calculated for the planets, is 
 exhibited in the following table : 
 
 Planet. 
 
 Distance from 
 sun : a 
 
 Period in 
 days : p 
 
 P~ 
 
 a 
 
 Mercury 
 
 0-38710 
 
 87-969 
 
 3342I 
 
 Venus .... 
 
 072333 
 
 224-701 
 
 I334I3 
 
 Earth .... 
 
 I -OOOOO 
 
 365 256 
 
 133408 
 
 Mars .... 
 
 1-52369 
 
 686-979 
 
 I334IO 
 
 Ceres (as typical Minor 
 
 
 
 
 Planet) . 
 
 2*77692 
 
 1679^55 
 
 I322IO 
 
 Jupiter .... 
 
 5-20277 
 
 4332-55 
 
 133294 
 
 Saturn .... 
 
 9-5385* 
 
 10759-220 
 
 -33375 
 
 Uranus .... 
 
 19-18239 
 
 3068(3 821 
 
 133422 
 
 Neptune 
 
 30-03627 
 
 60126-722 
 
 I334I3 
 
 To draw an ellipse, the following points must be borne in 
 mind, The eccentricity of an ellipse is the ratio of the 
 distance between the centre and either focus to the length of 
 the semi-axis-major. It is usually given as a decimal fraction, 
 
62 THE PLANETS GENERALLY. 
 
 the semi-axis-major being taken as unity, or ro. Thus, an 
 eccentricity given as 0-25 means that the distance between the 
 centre and either focus is th of the semi-axis-major. This is 
 sometimes symbolised by the Greek letter < and with an 
 angular measurement named . In that case the eccentricity is 
 obtainable by finding from the tables what is the natural sine 
 of the angle <. 
 
 In order to draw an ellipse of a prescribed eccentricity first of 
 all draw a line of any convenient length to represent the axis- 
 major of the intended ellipse ; bisect it and mark the point of 
 bisection ; then from the centre set off in each direction along 
 the line, according to the selected scale, distances equal to 
 the eccentricity ; the points so determined will be foci of the 
 required ellipse. Fix pins at these points and at one of the 
 extremities of the axis, and then proceed as follows. Tie a 
 loop of cotton or silk tightly round these pins ; remove 
 the pin which is at the extremity of the axis-minor ; stretch 
 the thread tightly with the point of a pencil and move the 
 pencil round under the guidance of the thread kept tightly 
 drawn. 
 
 Perhaps an actual example in figures will make the modus 
 operandi of this more clear. Say you want to draw an ellipse 
 of the eccentricity 075. Draw a line 10 inches long on stiff 
 white paper or card-board ; bisect it ; set off on each side of the 
 point of bisection distances of 3! inches (i.e. 7*5 half-inches) ; 
 these points will be the foci of the required ellipse. Then 
 proceed with the aid of the thread as above. Of course any 
 units may be employed in devising a scale, but perhaps inches, 
 as in the above example, will generally be found most convenient 
 when it is desired to obtain the form of a planetary or cometary 
 orbit. 
 
 Sir John Herschel put forth, many years ago, a fancy statement 
 for the purpose of enabling a reader to obtain a rough general 
 idea of the dimensions of the solar system and of its constituent 
 planets. The statement needs some revision and expansion, 
 
THE DISTANCES OF THE PLANETS. 
 
 to meet present circumstancestreatment which I have applied 
 to it ; and I now present it in the following form : 
 
 Imagine a large open common ; on it place a globe 2 feet in 
 diameter by way of representing the Sun ; Mercury will then 
 be represented by a mustard-seed at a distance of 82 feet ; 
 Venus by a pea at a distance of 142 feet ; the Earth also by a 
 pea at a dis- 
 tance of 215 
 feet ; Mars 
 by a small 
 pepper -corn 
 at a distance 
 of 327 feet ; 
 the Minor 
 Planets by 
 grains of sand 
 at distances 
 varying from 
 500 to 600 
 feet; then a 
 moderate- 
 sized orange 
 ^th of a mile 
 distant from 
 the central 
 point will 
 represent 
 Jupiter ; a 
 
 small orange fths of a mile, Saturn ; a full-sized cherry f ths of 
 a mile, Uranus ; and lastly, a plum i miles, Neptune, the most 
 distant planet yet known, though astronomers suspect there 
 exists another planet still farther off and hope one day to find it. 
 
 Extending this scheme, the aphelion distance of Encke's 
 Comet would be 880 feet ; the aphelion distance of Donati's 
 Comet 6 miles, and the nearest fixed star 7500 miles. 
 
 Fig. 72. Conjunction of Venus and Saturn, 
 Dec. 19, 1845. 
 
6 4 
 
 THE PLANETS GENERALLY. 
 
 An idea of the absolute movements day by day of the planets 
 in their orbits would be obtained by imagining Mercury to 
 move every day 3 feet; Venus 2 feet; the Earth if feet; 
 Mars i feet ; Jupiter io inches ; Saturn 7^ inches ; Uranus 
 5 inches ; Neptune 4 inches. These figures serve also to 
 illustrate the fact previously mentioned that the orbital velocity 
 
 of a. planet de- 
 creases as its 
 distance from 
 the Sun in- 
 creases : and 
 by a vast 
 stretch of the 
 imagination we 
 might suppose 
 a place in the 
 Universe 
 where a planet 
 would not 
 move round 
 the Sun at all ; 
 in other words, 
 where Gravita- 
 tion would 
 cease so far as 
 our solar 
 system was 
 concerned. 
 
 A matter of 
 
 some interest, as a spectacle, is the occasional conjunction of 
 two or three planets in the same part of the heavens. It is 
 exceedingly rare to get more than two planets together in the 
 same field of a telescope, but a combination of two only is not 
 at all uncommon. Besides those which are here illustrated, 
 some more recent instances may be mentioned. 
 
 Fig. 73 Conjunction of Mars and the Moon, 
 Sept. 28, 1909. 
 
CONJUNCTIONS OF THE PLANETS. 65 
 
 In September 1878 Mercury and Venus were together in 
 the same field of the telescope for some hours. According 
 to Nasmyth, the contrast in the appearance of the two planets 
 was very marked. Venus looked like clean silver, whilst Mer- 
 cury had more the appearance, of lead or zinc. This last 
 statement is rather curious, because Mercury is generally 
 credited with being of a rosy tinge. 
 
 On August 9, 1886, Venus, Saturn, and the bright star 
 8 Geminorum were in the same field. 
 
 On May 6 of the same year Venus and Mars were very 
 close to one another, Venus being o 5' to the south. 
 
 That same month of May 1906 yielded two other con- 
 junctions visible in telescopes armed with low-power eye- 
 pieces having large fields. 
 
 On May n Venus and Jupiter were close together, Venus 
 being T n' to the N. A week later, on May 18, Mars and 
 Jupiter were closer still together, Mars being i 6' N. Such 
 a succession of planetary conjunctions, conspicuous planets 
 being involved, is unique. 
 
 On August 17, 1911, Mars and Saturn were within 21' of 
 each other, and therefore in the same field. McEwen, at 
 Glasgow, remarked that : 
 
 " Saturn presented a bright chrome colour in contrast to the 
 bright ochre tint of Mars. It must, however, be admitted at 
 a first glance that Mars did look somewhat insignificant com- 
 pared with Saturn with its rings, although to the naked eye 
 Mars appeared much the brighter of the two planets." 
 
 An observer in America, Conroy, at Los Angeles, wrote 
 much to the same effect : 
 
 " The difference in the colours of the two planets was not 
 as pronounced as I had supposed it would be. Mars glowed 
 with his usual strong, ruddy hue. To the naked eye, and 
 still more in a field-glass, Saturn was decidedly yellow, with 
 a greenish tinge." 
 
 5 
 
66 THE PLANETS GENERALLY. 
 
 The 1 8th century produced a planetary conjunction which, 
 if correctly recorded, must have been singularly striking, 
 for it is said that Venus, Jupiter, Mars, and Mercury were 
 all seen together in the same field of the telescope. 
 
 Whilst we nowadays clearly understand that the Sun is the 
 centre of our planetary system, yet the realisation of that fact 
 is quite a thing of modern times, being hardly more than three 
 centuries old. Our system has been called the Copernican 
 System, from the Polish astronomer, Copernicus, who gave it 
 shape, though not quite its final shape. Up to his time, and 
 indeed for a century or more later, there were rival systems 
 in the field. They may be named in something like the order 
 of date as the Ptolemaic System, the Egyptian System, and 
 the Tychonic System. But it seems hardly worth while to 
 describe these in detail. 
 
 The question is a natural one : Are there more planets 
 circulating round the Sun than those already spoken of? It 
 is probably true to say that there are, and the question of a planet 
 within the orbit of Mercury, and also of one beyond the orbit 
 of Neptune, are matters which have attracted the thoughts of 
 many astronomers, though without any very certain results. 
 
 The romance of an intra-Mercurial planet caused great 
 searchings of heart 50 odd years ago, and many were fas- 
 cinated with the story of the French doctor, Lescarbault. The 
 idea of a Trans- Neptunian planet has not yet reached the stage 
 of romance, much less that of fascination. 
 
CHAPTER VI. 
 
 THE MOST INTERESTING AND FAMILIAR 
 PLANETS. 
 
 A classification of the planets. Mercury. Difficult to observe. 
 Spots. Phases. Schiaparelli's observations. A xial rotation. 
 Statistics. How to find Mercury or Venus. Venus. Movements 
 resemble those of Mercury. Physical Features. Possible moun- 
 tains. A tmosphere. A lleged satellite. Phases. Galileo's ana- 
 gram. Statistics. Mars. The Earth's nearest neighbour. Cele- 
 brated for its colour. Subject to a slight phase. This planet very 
 accessible for observation. Its apparent movements. Physical 
 appearance. Much controversy as to this. Polar snows. Spots. 
 Markings very permanent. Its colour. Satellites. Statistics. 
 Jupiter. Easy of observation. The largest planet. Belts. Spots. 
 Jovian spots and Sun-spots. Satellites. Large ones easily found 
 and followed. Small ones very difficult. Phenomena. Velocity 
 of light. Statistics. Saturn. Its rings. General description of 
 them. How designated. Changes in the appearance of the rings 
 from time to time. Some details respecting them. The ball. 
 The satellites as tests for telescopes. Statistics. 
 
 THE classification of the planets in a previous chapter into 
 < Inferior' and 'Superior,' though desirable from a scien- 
 tific point of view, is not one which appeals much to the 
 popular observer of astronomical phenomena, who is con- 
 cerned more particularly with what he is able to see. 
 Accordingly, it will be convenient to adopt now a new classi- 
 fication, which cuts across the previous one, because of its 
 being framed upon quite a different basis. Whilst one group 
 responds readily to the general title of the " Interesting and 
 Familiar Planets," it would be somewhat unphilosophical to 
 
 6 7 
 
68 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 gibbet the residue as the " Uninteresting Planets," for the 
 statement would not be true of some of them, and I can only 
 give them the vague title of "planets which do not attract 
 the notice of the generality of readers." 
 
 Under the title of " Interesting and Familiar Planets " I 
 shall deal with Mercury, Venus, Mars, Jupiter, and Saturn, all 
 of them shining, as a rule, with a sufficient amount of general 
 brightness to attract the notice of almost everybody from time 
 to time ; but Venus, Mars, and Jupiter, under all circum- 
 stances, do so most. Mercury and Venus, being within the 
 orbit of the Earth, can never be very far from the Sun. Venus, 
 however, on occasions, shines with such splendour that twi- 
 light has no appreciable effect in impairing it. Mercury, 
 however, being so much nearer the Sun than Venus, is more 
 difficult to find and follow, because it is never out of bright 
 twilight. The other planets belonging to this chapter Mars, 
 Jupiter, and Saturn are all intrinsically bright, especially Mars, 
 and, as they wander all over the heavens, one or other of 
 them is almost always in view at some hour of a given night. 
 Inasmuch as all these five planets have special features of 
 their own, it will be well to give them sections of this chapter 
 to themselves. 
 
 MERCURY. 
 
 Mercury does not receive much attention, owing to the diffi- 
 culty of seeing it, as already stated. Its greatest possible 
 elongation or distance from the Sun not exceeding 27 45' 
 (and it being in general much less), the difficulty is obvious. 
 The greatest possible elongation on the E. side happens at 
 the end of March or beginning of April, Mercury being an 
 "evening star"; whilst the greatest possible elongation on 
 the W. side happens in September, when Mercury is a 
 " morning star." 
 
 The chances of seeing it are best for us in England when 
 an elongation coincides with a northerly position of the planet 
 
MERCURY. 69 
 
 in declination, even though the elongation is less than it 
 might be at other times. It may often be seen with the naked 
 eye, shining with pink or rosy light. It was so seen by many 
 observers in April 1905. 
 
 The observations of Schroter at Lilienthal, and of Sir VV. 
 Herschel, led them to think they had obtained decisive 
 evidence of high mountains on the planet's surface, and that 
 one in particular in its southern hemisphere manifested its 
 presence by the 
 planet's southern 
 horn having a 
 truncated (or 
 blunted) appearance 
 near Inferior Con- 
 junction, which 
 might be due to a 
 mountain obstruct- 
 ing the light of the 
 Sun from reaching 
 as far as the point 
 to which the cusp 
 theoretically ex- 
 tended. 
 
 Denning, in 1882, 
 saw some dark 
 irregular spots upon Fig. 74. Mercury, Sept. 17, 1885. (Gttiot.) 
 the planet ; also a 
 
 brilliant spot and a large white area. The southern horn 
 was also much blunted. He states that his results led him 
 to infer that the markings upon Mercury are far more 
 decided and more easily discernible than those of Venus, 
 and that Mercury's surface resembles in physical appearance 
 that of Mars. A French observer, Guiot, in 1885, remarked 
 on September 17 that both the horns of Mercury (then almost 
 a semicircle) were truncated j but that only the southerji horn 
 
70 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 was so five days later. He mentions no signs of shading 
 or spots. 
 
 I have already stated in a previous chapter that Mercury is 
 subject to phases, and will repeat here the bare fact only by 
 way of reminder ; and will merely add that it has sometimes 
 been found that the illuminated portion is less than it should 
 be, according to calculation. This statement rests upon the 
 testimony of some competent observers, and remains un- 
 explained. Explanation is the more difficult because there is 
 no sufficient evidence that Mercury possesses an atmosphere. 
 
 There is some ground for the opinion that it is more easy to 
 notice the appearance of this planet's surface than is the case 
 with Venus. More than one observer besides Denning, quoted 
 above, has gone so far as to suggest that, if viewed under 
 favourable circumstances, the surface presents an aspect more 
 nearly resembling that of Mars than any other planet. 
 
 The astronomer who in recent times has made the most 
 systematic study of Mercury is Schiaparelli, some of whose 
 conclusions are rather startling. First of all, he considered his 
 best chances of studying the planet's surface to be when the 
 Sun is above the horizon, and that the resulting inconvenience 
 is less distracting than the tremors which manifest themselves 
 when the planet is viewed low down towards the horizon when 
 the sun is absent. He thought, indeed, that some of the mark- 
 ings which he noticed were permanent ; hence the supposed 
 analogy between Mercury and Mars. But the most sen- 
 sational of Schiaparelli's conclusions is that Mercury's axial 
 rotation takes place, not in the 24 hours, or thereabouts, 
 generally supposed, but in 88 days, being the period occupied 
 by the planet in going round the Sun. 
 
 This conclusion is mentioned because of Schiaparelli's ex- 
 perience and standing as an observer, but it is impossible to 
 accept it in the present state of our knowledge, though some 
 other observers, including Lowell, in 1896, have seemed in- 
 clined to agree with Schiaparelli, 
 
MERCURY. 71 
 
 By means of a dark spot seen in April 1904, McHarg fixed 
 the period of rotation at 24 h. 8 m., which accords with all 
 previous values except Schiaparelli's. 
 
 Mercury revolves round the Sun in almost exactly 88 days 
 at a mean distance of about 36,000,000 miles, which may 
 vary between the limits of 43,347,000 miles and 28,570,000 
 miles. These great extremes in the distance of Mercury from 
 the Sun at different times are due to the great eccentricity of 
 the planet's orbit, which is greater than that of any of the older 
 planets, though exceeded by many of the Minor Planets dis- 
 covered in modern times. The apparent diameter of Mercury 
 varies between4^" in Superior Conjunction and 13" in Inferior 
 Conjunction. The real diameter may be taken to be about 
 3000 miles, or perhaps a little less. 
 
 It may be useful to many of my readers to suggest to them 
 a convenient method for finding either Mercury or Venus in 
 daylight by means of a telescope unprovided with an equatorial 
 mounting or circles. For the successful use of the method 
 certain favourable but simple conditions respecting the 
 telescope and the planets are required. The telescope must 
 be perfectly steady on a substantial stand, and anchored in 
 some way so that it will not move after having been once 
 placed in a definite position, to be presently named ; and it 
 must be provided with an eye-piece of low power having the 
 largest possible field. The planet to be sought must have a 
 declination, which shall not differ more than about 3 or so 
 from that of the Sun, and the planet's right ascension must be 
 greater than that of the Sun. If the difference of declination 
 much exceeds 3 the chances of picking up the planet will be 
 much diminished. 
 
 The above conditions being fulfilled, the method consists in 
 using the Sun to find the position in the sky which corresponds 
 with the planet's declination ; and, the telescope being pointed 
 to what is believed to be about the planet's declination, the 
 Observer h^s only to wait until, by the rotation of the Earth, 
 
72 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 the planet is brought into the field of the telescope. Two 
 further preliminaries must be observed : the telescope must be 
 carefully focussed either on a Sun-spot or by means of the 
 Sun's limb. A dark glass must be used in doing this, and 
 when this has been done a pale neutral glass should be used 
 whilst the planet is being swept for. 
 
 Accurate focussing of the telescope is very important ; other- 
 wise the planet may escape the eye which is looking for it, 
 because a diffused unage is easily overlooked. The focussing 
 having been assured, the Sun must be carefully brought into 
 the centre of the field, and the line along which it travels 
 into and out of the field must be carefully noted. This is 
 done most easily if the eye-piece of the telescope is provided 
 with two wires crossing each other. 
 
 The Sun having been brought to the centre of the field, the 
 telescope must be moved upwards (or downwards) at right 
 angles to the apparent line of the Sun's movement by the 
 amount of the difference (estimated from the centre of the Sun) 
 between the Sun's right ascension and the planet's right 
 ascension, the centre of the field being taken in both cases as 
 the point aimed at. 
 
 No circles being available, the observer should remember 
 that, the diameter of the Sun's disc being approximately , 
 the telescope must be moved vertically by as many half- 
 degrees as equal the difference between the declinations 
 of the Sun and the planet respectively. For instance, if 
 the difference is 2^, the telescope must be moved by the 
 amount of 5 diameters of the Sun. The observer has now 
 nothing more to do but to wait with his eye at the telescope 
 until there has elapsed the time in minutes which is the 
 amount of difference between the R.A. of the Sun and that of 
 the planet. 1 
 
 1 For further details and examples of this method, which was put forward 
 by Dr. R. J. Ryle, see The Journal of the British Astronomical Association, 
 vol. xv. p. TOO, December 1904. 
 
FIGS. 75-77 
 
 PLATE XXIV. 
 
 72] 
 
FIG. 78 
 
 PLATE XXV. 
 
 The Various Phases of Venus. 
 
 [73 
 
VENUS. 
 
 73 
 
 VENUS. 
 
 What has been 
 said already with 
 respect to Mercury 
 will have paved the 
 way for some of the 
 things which will now 
 have to be said 
 respecting Venus ; 
 but, as regards one 
 matter its brilliancy 
 on occasions Venus 
 stands out in advance 
 of all the planets. 
 Such is the case 
 especially whenever 
 we look at it in the 
 evening or the 
 morning, fulfilling 
 the functions, in 
 popular parlance, of 
 the " evening star " 
 or the " morning 
 star." But on certain 
 occasions, at rare 
 intervals, when the 
 planet is at or near 
 its greatest N. Lati- 
 tude and about 5 
 weeks from Inferior 
 Conjunction, it shines 
 with surpassing 
 splendour, equal to, 
 or even greater than, 
 
 Fig. 79. Venus near its|inferior 
 conjunction. (Schroter.) 
 
 Fig. 80. Venus, Dec. 23, 1885. 
 
 (Lihou.) 
 
74 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 that of Sirius (a Canis Majoris). This only happens about 
 once in years, and occurred last in 1910, and will recur 
 in 1918. The brightness is sometimes such that the planet 
 casts a shadow. Such was the case on January 12, 1902, as 
 recorded by Giacobini at Nice. 
 
 The further fact will therefore seem to follow quite naturally 
 that the planet is often readily visible in the daytime, especially 
 if, by means of graduated circles, the seeker knows exactly 
 where to look for it. 1 , It is the opinion of those who have made 
 a special study of Venus that, on account of its brilliancy, it is 
 easier to detect its physical features by daylight, or in quite 
 early twilight, rather than when it has a dark sky behind it. 
 These features include shadings or patches of shade, and the 
 truncature of one or both horns when the planet shows as a 
 crescent ; and these facts indicate beyond doubt not only.that 
 the visible surface is not even, but that mountains exist on it. 
 It is not, however, usual to speak definitely of the existence of 
 mountains, less precise words, such as markings, or shadings, 
 or spots being used. 
 
 A Portuguese observer, M. Lacerda, has stated that the 
 southern horn is always longer than the northern one ; that 
 is to say, that the northern one is often more blunt than the 
 southern one. The same observer remarked that the most 
 favourable times for viewing the planet were always between 
 half an hour before and one hour after sunrise ; and that the 
 corresponding times at sunset, when the planet was in the W., 
 never afforded him such good results. 
 
 As regards the physical appearance of the surface of Venus 
 the difficulties are very much the same as those which are 
 encountered in viewing Mercury, and the visual results are not 
 very different ; that is to say, in addition to the blunted horns 
 already mentioned, spots are visible from time to time. 
 
 It is from these facts that the conclusion has been drawn 
 that, as in the case of Mercury, mountains probably exist ; but 
 
 1 S$e p. 71, ante. 
 
VENUS. '- 75 
 
 there is a conflict of opinion as to whether these mountains 
 have an objective existence on the body of the planet, or 
 whether the shadings, which have been assumed to be moun- 
 tains, are merely shadings in an atmosphere which simulate 
 mountains. 
 
 The fact that Venus has an atmosphere of considerable 
 density seems well established, especially by the appearance 
 presented by the planet when under observation during transit 
 across the Sun. A further proof of the existence of an atmo- 
 sphere was furnished on July 26, 1910, on the occasion of an 
 occultation of the star rj Geminorum by the planet. The star's 
 brightness diminished rapidly during 2 or 3 seconds before 
 immersion, and increased rapidly during i or 2 seconds after 
 emersion. It was thought by the French observers who noted 
 these results that a variation of light during 2 seconds would 
 be explained by the existence of an atmosphere about 68 mik s 
 in height. There is such a considerable coincidence in the 
 various figures arrived at as regards Venus's atmosphere that 
 its reality and considerable extent are open to no doubt. Per- 
 haps even it is more dense than that of the Earth. 
 
 When Venus is near its Inferior Conjunction there may 
 sometimes be noticed an appearance not unlike the Lumiere 
 cendree, or "ashy light," frequently visible when the Moon 
 exhibits a narrow crescent, as mentioned in the previous 
 chapter. (Ante, p. 36.) 
 
 Though this phenomenon has been seen and recorded by 
 many observers during a long period of time, the most careful 
 and complete observations are those which were made by 
 Zenger at Prague in 1883. Without quoting the details gener- 
 ally which he noted, it may suffice to state that he considered 
 all the phenomena which are presented by Venus when its disc 
 is partly illuminated and partly unilluminated find a complete 
 counterpart in what we see when scrutinising the Moon ; and 
 that the varying tinges, sometimes simply dark, are analogous 
 tp what we often see in looking at a "young" Moon, or the 
 
j6 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 Moon eclipsed. In other words, that, as we know the variations 
 in the Moon's appearance which we see from time to time 
 under such circumstances depend on the varying conditions of 
 the Earth's atmosphere, so the different appearances presented 
 by Venus depend upon the varying conditions of the atmo- 
 sphere of Venus. We have seen that, in the case of Mercury, 
 the measured breadth of its phase, when half illuminated, does 
 not always accord with the theoretical breadth which ought 
 to be shown at that particular stage. The same discrepancy 
 occurs in the case of Venus. 
 
 There once raged a long controversy, spread over many 
 years during the i8th century, as to whether Venus had 
 a satellite. The testimony to that effect was varied and 
 strenuous, and proceeded from many observers ; but there is 
 now no question but that they deceived themselves, and in their 
 small telescopes mistook stars for companions to the planet, for 
 it is quite certain that if Venus did possess a satellite, it would 
 have been recognised long ago in some of the many great 
 telescopes which were brought into use in the second half of the 
 igth century. 
 
 The planet Venus has always occupied a prominent place in 
 the literature of poets and historians during more than two 
 thousand years. It would occupy too much space to offer any 
 quotations, but there is one literary trick (I can use no better 
 word) which is associated with the planet and which deserves 
 mention, especially because, as we go along, we shall find that 
 the same trick confronts us in the case of another planet. In 
 olden times, say three centuries ago, before the days of Copy- 
 right and Patent Laws and " Merchandise Marks Acts," when 
 a man discovered something the honour of which he desired to 
 attach to his own name, he announced it in obscure phrase- 
 ology, which secured him the priority of credit without disclosing 
 his discovery in detail. Thus it was that Galileo, who dis- 
 covered the phases of Venus, is said to" have announced his 
 discovery in the following Latin logogriphe, or anagram ; 
 
FIGS. 81-86 
 
 PLATE XXVI. 
 
 March 22, 6 h. 
 
 March 26, 7 h. 
 
 March 28, 
 
 March 30, 6f h. 
 
 March 31, 6^ h. 
 
 76] 
 
 Venus, 1881 (W. F. Denning). 
 
 April 5, 6J h. 
 
FIGS. 87-92 
 
 PLATE XXVII. 
 
 May 14, 8J- in spec. (W. F. Gale). April 14, i2| in spec. (P. B. Molesivorth). 
 
 April 19, g\ in spec. (T. E. R. Phillips). April 21, 2\ in spec. (P. B. Molesworth). 
 
 May 21, 5 in O.G. (tf. /ft/M/*). April 8, 6J in spec. (//. Carder). 
 
 Mars, 1903. [77 
 
VENUS. 77 
 
 " Haec immatura a me, jam frustra, leguntur oy " ("These 
 things not ripe ; at present [read] in vain [by others] are read 
 by me " ), the " me " being Galileo. 
 
 This Latin sentence, when transposed, becomes : " Cynthia 
 figuras aemulatur Mater Amorum " (" The Mother of the Loves 
 [Venus] imitates the phases of Cynthia [the Moon] "). 
 
 The letters " oy " are, it will be observed, redundant, so far 
 that they cannot be made use of in the transposition. 
 
 There seems reason to believe that the special brightness of 
 Venus at its best is due to some exceptional condition of things 
 which enables it to reflect a larger proportion of the Sun's rays 
 falling upon it than is the case with Mercury. 
 
 It is good practice for an amateur to try and ascertain up till 
 how long before^ and how soon after, Inferior Conjunction he 
 can see Venus in a telescope. The interval ought only to be 
 one of hours, and not many of them. 
 
 Venus travels round the Sun in 224 days at a mean distance 
 of 67,020,000 miles. The orbit is nearly that of a circle, 
 its eccentricity being the smallest of all the orbits of the 
 large planets, but several minor planet orbits are more nearly 
 circular. The apparent diameter of Venus varies between 9" 
 in Superior Conjunction and 65" in Inferior Conjunction. At 
 its elongations its apparent diameter is 25". The real diameter 
 is about 7500 miles ; that is to say, Venus is nearly, but not 
 quite, so large as the Earth. The period of its axial rotation 
 is disputed, but it probably amounts to about 23! hours. 
 
 MARS. 
 
 We will now proceed to the important planet, Mars, passing 
 over the Earth for the reasons already given : that, though the 
 Earth is a planet, and a very important one too, we cannot, 
 because we are on it, study its appearance in the way in which, 
 with the assistance of telescopes, we study the appearance of 
 other planets. 
 
78 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 Mars and Jupiter, which will occupy our attention in the next 
 section, are the planets which most often attract our notice 
 in the sky by night because one or other of them is almost 
 always visible at some time or other between sunset and 
 sunrise. Moreover, Mars, by reason of its normal fiery colour, 
 can never be mistaken, or at any rate should never be mis- 
 taken, for any other planet or for any star. 
 
 Mars exhibits, on occasions, a slight phase, but it is not 
 very noticeable. When the planet is in Opposition that is to 
 say, is on the meridian at midnight it presents a perfectly 
 circular disc ; but at other times it is gibbous, the maximum 
 defalcation of light occurring when the planet is in Quadra- 
 ture, or 6 hours away from the Sun, either E. or W. At 
 these epochs the planet resembles the Moon 3 days on either 
 side of the epoch of Full Moon. 
 
 By reason of its proximity to the Earth, it comes into 
 Opposition about once in every two years, or, to be more 
 exact, every 780 days, this being what is called its "synodic 
 period." When in perihelion (that is, nearest to the Sun) 
 and in perigee (that is, nearest to the Earth) at the same 
 time, which coincidence occurs every 15 years, Mars rivals 
 Jupiter in brilliancy. This happened last in the summer of 
 1909, and will not occur again until 1924. But the fact that 
 we get a good view of Mars at the short interval of every two 
 years gives us great facilities for studying it, and should be 
 an encouragement to tracing its movements in the heavens 
 amongst the stars. This is not so conveniently done in the 
 case of the other Superior Planets because they take so many 
 more years in making their circuits round the Sun, and move 
 so much slower amongst the stars. It will be interesting, there- 
 fore, to state in detail what those movements are as we on the 
 Earth see them. Starting when Mars has just passed through 
 Conjunction, it emerges from the Sun's rays, rising some 
 minutes before the Sun, and having a direct, that is, easterly 
 motion ; but as this motion is only half that of the Earth in the 
 
FIGS. 93-98 
 
 PLATE XXVIII. 
 
 May 12, 9^ in spec. (T. E. R. Phillips). April 30, laf in spec. (P. B. Molesworlh). 
 
 March 31, 8| in spec. (. M. Antoniadi). March 31, 6 in spec. (E. A. L. Attkins). 
 
 March 31, fij in spec. (ir. /. //a//). May 7, 9} in spec. (T. E. R, Phillips). 
 Marc 
 
FIG. 99-100 
 
 PLATE XXIX. 
 
 Sept. 20, 1909. 
 
 Nov. 5, 1909. 
 
 Mars (Antoniadi). 
 
 179 
 
MARS. 79 
 
 same direction, Mars appears to recede from the Sun in a 
 westerly direction, notwithstanding that its true motion 
 amongst the stars is towards the E. This continues for 
 nearly a year, and ceases when it has attained an angular 
 distance from the Sun, measured along the Ecliptic, of about 
 137. Then for a few days it does not seem to move at all. 
 After that its motion becomes retrograde or westerly among 
 the stars, and so continues until it reaches a point 180 from 
 the Sun, or, in other words, is in Opposition or on the meridian 
 at midnight, when therefore it is seen at its best by us. At 
 this time its retrograde motion amongst the stars attains its 
 greatest rapidity, but it soon slackens and becomes slower and 
 slower until it has arrived at a point 137 from the Sun. Then 
 its motion again becomes direct and so continues till once 
 again the planet is lost in the Sun's rays, soon after which it 
 reaches Conjunction, and another two-year period of changes 
 begins. Though they are renewed on the same principles, 
 there will be changes in the details ; the retrogradation does 
 not always commence or finish at 137, for it may begin as soon 
 as 128 is reached, or may not begin until 146 is reached, 
 the arc described varying between 10 and 19!. The 
 duration of the retrograde motion in the former case is 60 
 days, and in the latter 80 days. The period in which these 
 changes take place, at the interval between two successive 
 Conjunctions or two successive Oppositions, constitutes the 
 synodical period of 780 days already mentioned. 
 
 The physical appearance of Mars as seen in our telescopes 
 may be regarded as not subject to much change except in one 
 particular. I say this advisedly, because although during the 
 past 30 years there has been a flood of controversy respect- 
 ing the appearances presented by the surface of Mars, and 
 there has been a great disposition to indulge in extravagant 
 language, there is abundant evidence to show that there are 
 certain defined marks which are unchanged and are probably 
 unchangeable. 
 
80 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 I will deal with and dispose first of all, of the appearances 
 which are mentioned in the preceding paragraph as being the 
 one particular exception to the rule of unchangeability. This 
 statement refers to the spaces around the poles, which are 
 commonly reputed to be signs of the existence of snow. I 
 think this may be taken to be a certainty, because they are 
 observed to diminish when brought under the influence of the 
 Sun at the commencement of Mars's summer, and to increase 
 again on the approach of Mars's winter. The illustrations 
 annexed are sufficiently self-descriptive. 
 
 Some anomalies have been noticed from time to time in 
 regard to these polar patches, not sufficiently great, however, I 
 think, to negative their being masses of snow, but still somewhat 
 strange. For instance, whilst both Madler and Secchi found 
 the north patch to be concentric with the North Pole of the 
 planet, yet that the south patch was not concentric with the 
 South Pole. Sir W. Herschel, as far back as 1784, noticed that 
 the patches were -not exactly opposite to one another. 
 
 Spots on Mars are frequently seen, and have enabled 
 astronomers to arrive at very consistent conclusions as to the 
 period of the planet's axial rotation, which may certainly be set 
 down at 24 hours 37 minutes. 
 
 The geography (to use the obviously wrong word) of the 
 surface of Mars has been attentively studied during the three 
 centuries which have elapsed since the invention of the 
 telescope, and drawings of every kind, by astronomers of every 
 sort, using telescopes of every size, exhibit a consistency which 
 is very remarkable. No wonder the whole globe has been 
 mapped out into areas, hypothetically regarded as land and 
 water, to which names, many of them very bizarre, have been 
 given. The original series of names was restricted in number, 
 and included the names of some twenty leading observers of 
 note in the astronomical world. Without saying that these 
 names have been formally discarded, yet a new series of 
 names, Latin in form and in a certain sense mythical, have 
 
FIG. lOOa 
 
 PLATE xxixa 
 
 MARS. 
 October 21, 1909 . 
 
 (S. Boltoti) 
 
MARS. 8 r 
 
 been brought into use and seem to be meeting with acceptance 
 from astronomers. 
 
 After the polar patches spoken of already the one most 
 obvious feature which most generally attracts notice when that 
 particular hemisphere of Mars where it is situated happens to be 
 under observation is that known as the " Kaiser Sea," some- 
 times called the " V " mark, from resemblance to that letter ; 
 but which much more -readily brings to mind the continent of 
 South America, if one could imagine a piece stuck on at the 
 southern tip at right angles to the general trend of tha't con- 
 tinent. The shape of a leg of mutton has also been suggested. 
 
 The ruddy colour of Mars has been notorious from the 
 earliest times in which v:ritten mention of the planet has been 
 handed down, and Sir John Herschel ascribed it to " an ochrey 
 tinge in the general soil like what the red-sandstone districts 
 on the Earth may possibly offer to the inhabitants of Mars, only 
 more decided." This idea is not so far-fetched as might at 
 first be thought. 
 
 There are parishes in Gloucestershire, one of them named 
 Red Marley, which, to those who have visited them, would bring 
 home Herschel's idea. There might easily be imparted to the 
 Earth, when viewed from Mars, a very distinct reddish colour 
 supposing that there were many thousands of square miles all 
 geologically resembling the soil of the parish of Red Marley. 
 
 Another long-standing idea with respect to the surface of 
 Mars is that it is visibly divided, as the Earth is, into land and 
 water, the ruddy areas being land and the almost equally 
 greenish areas being water. 
 
 The great controversy of the present day respecting Mars is 
 the reality, or otherwise, of an immense number of "canals" 
 said to exist all over it, and to show themselves in the form of 
 numerous dark lines, very straight, and so well defined as to 
 indicate for them an artificial origin. The observer who first 
 put forth this alleged fact and its explanation has found a few 
 supporters, or men who have been claimed as such because 
 6 
 
82 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 they thought they had seen markings on the planet which 
 might be regarded as straight lines intercepting one another at 
 various angles. On the other hand, it is undoubtedly true that 
 the vast majority of observers, using telescopes of every size and 
 kind, have never suggested the existence of any such precise 
 markings, or been able to find them when invited to look for 
 them. 
 
 Professor W. H. Pickering, taking an 'intermediate view, has 
 reviewed the controversy respecting the markings on Mars in 
 the following terms : 
 
 "It has lately been shown by Messrs. Lane, Maunder, and 
 Evans that many of the finer Martian canals are probably non- 
 existent, their appearance being due to certain singular optical 
 illusions. Most of the broader canals, however, in the dark 
 regions of the planet undoubtedly exist, and the same is almost 
 certainly true of some of those in the light regions, such as 
 Nilosyrtis and Nectar. The chief cause of the illusion seems 
 to be the system of lakes, or oases, as they are sometimes 
 called, which were first discovered in large numbers at 
 Arequipa. 
 
 "There is a curious tendency of the human eye to see such 
 dark points united by faint narrow lines, and it has been shown 
 by means of diagrams that these lines sometimes appear when 
 the diagram is at such a distance that the dark dots are them- 
 selves invisible. But even without the dots the lines may some- 
 times appear, joining different portions of the dark regions. 
 We must therefore divide the Martian canals into two classes : 
 those that are genuine and those that are not. . . . 
 
 " This phenomenon of spurious canals is certainly very 
 singular, but we must IDC careful that its interest and unexpected- 
 ness do not lead us into the error of affirming that, because 
 many Martian canals are spurious, therefore all Martian canals 
 are imaginary. It seems indeed a great pity that so much 
 time and energy should have been expended in many observa- 
 tories in mapping canals in the bright regions of the planet, 
 and comparatively so little time spent on the darker regions, 
 where changes are constantly taking place, and where we should 
 naturally expect the more interesting developements to occur." 
 
FIG. 101 
 
 PLATE XXX, 
 
 ***$% 
 
 
 82] 
 
FIGS. 102-107 
 
 PLATE XXXI. 
 
 [83 
 
MARS. 83 
 
 At one time it was urged that, not only was Mars crossed and 
 recrossed by sharply defined dark lines, but that many of these 
 lines were doubled : hence arose the word " germination " as 
 applicable to them. Weighing the pros and cons of the con- 
 troversy on the principles of the law of evidence as applied 
 by lawyers, I cannot consider that the arguments put forth in 
 support of the multiplicity of sharply defined markings is 
 established, and think that the only thing which is established is, 
 that there are numerous markings on Mars which take various 
 shapes, and, when clearly visible, are at best ill-defined, iand 
 that very often they are not clearly visible. Finally, that their 
 visibility depends in no small degree on the personality of the 
 observer and on atmospheric and other circumstances. 
 
 There is one matter connected with Mars which has yet to 
 be mentioned, namely, its satellites. Though these cannot 
 be said to concern the general reader because of their diminu- 
 tive size, yet a certain amount of historic interest attaches to 
 them. They were only discovered as recently as the year 
 1877, when an American observer, A. Hall, conceived the idea 
 of turning to account the favourable Opposition of that year to 
 search for a satellite, as he had at command the fine refracting 
 telescope of the Washington Observatory, carrying an object- 
 glass 26 in, in diameter. His efforts were soon rewarded by 
 the discovery not only of one, but of two satellites, which have 
 been named Phobos and Deimos, the names of the steeds said 
 by Homer to have drawn the chariot of Mars. 
 
 When it is stated that Phobos at its best is no brighter than a 
 star of Magnitude 1 1 , whilst Deimos is as faint as a star of Magni- 
 tude 13, it will be realised at once that only telescopes of very 
 large size can observe them. Historically it is interesting to note 
 that, in Gulliver's Travels, the astronomers of Laputa are 
 spoken of as having discovered that Mars had two satellites, 
 whilst Voltaire, in his " Romance of Micromegas," ascribes to 
 some of his characters also the discovery of two Martial 
 satellites " which had escaped the scrutiny of our astronomers." 
 
84 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 It is to be presumed that Voltaire was only a copyist of Dean 
 Swift. 
 
 Mars travels round the Sun in 686 days, at a mean distance 
 of 140,000,000 miles. The eccentricity of the orbit, though a 
 good deal less than that of the orbit of Venus, is nevertheless 
 very considerable, so that the planet's distance from the_ Sun 
 may on occasions be as great as 154,000,000 miles, or as little 
 as 128,000,000 miles. The planet's apparent diameter varies 
 between 4" in Conjunction and 30" in Opposition. Owing to 
 the great eccentricity of the orbit the apparent diameter, as 
 seen from the Earth, will also differ greatly at different times. 
 The real diameter may be regarded as almost exactly 5000 
 miles. 
 
 JUPITER. 
 
 On the whole, Jupiter may be said to be the planet most 
 easily brought within the reach of everybody, and for this 
 reason ; it is generally visible for many months in every year ; 
 it is more or less conspicuous owing to its normal brightness, 
 and, from the standpoint of the mere sightseer, its belts and 4 
 principal satellites are within the reach of quite small telescopes. 
 Indeed, instances are on record of the satellites, when suffi- 
 ciently near to join forces as regards their combined light, 
 have, under very favourable circumstances of atmosphere and 
 the observer's keenness of vision, been visible to the naked eye. 
 
 Jupiter is the largest of all the planets, having a 
 diameter of about 88,000 miles. So large a body rotating on 
 its axis in the short time of 10 hours or thereabouts, it follows 
 that, by the laws of rotatory motion, the compression of the 
 polar diameter is very marked, amounting, according to the 
 best authorities, to about T Vth of the equatorial diameter. 
 
 The belts have long been known as a notable feature of the 
 planet. There is a certain amount of permanency about them, 
 yet it cannot be said that they are permanent. To look at 
 them, they are dusky streaks of different breadths, which 
 
JUPITER. 85 
 
 breadths vary from time to time. Sometimes they chiefly 
 appear as two or three broad belts, at another time the 
 observer will notice a greater number of belts, all much 
 narrower than those he may have seen on some previous 
 occasion. They are all parallel to the planet's Equator, though 
 commonly absent actually under the Equator. On very rare 
 occasions a single belt may be noticed lying askew to the 
 general trend of the belts. The latest recorded instance of 
 this was in April 1910, S. Bolton being the observer. It may 
 be taken for granted that in looking at Jupiter we are not 
 looking at anything in the nature of a solid body, but only at 
 a cloudy envelope, which may or (more likely) may not en- 
 compass a solid globe. It has been suggested that the 
 changes visible on Jupiter are proofs of the manifestation of 
 energy in the form of heat on the planet. 
 
 The question as to their colour sometimes arises, because, 
 though generally grey or greyish, distinct tinges of brown may 
 be traced, whilst in 1877 a great red spot burst forth, which 
 remained for many years a striking and permanent feature. 
 The later history of this spot is very remarkable, and there is 
 a mystery about it which is still unsolved. It retained its 
 shape and colour for about four years, up till the autumn of 
 1882, when it began sensibly to fade ; and during the ensuing 
 year it became extremely faint, though still preserving its form. 
 In the years between 1884 and 1906 it underwent various 
 changes, never recovering its original bright colour. In 1906, 
 whilst the shape remained, the tinge of colour was no more 
 than grey, though something slightly wanner was sometimes 
 suspected. In 1909 the spot was all but invisible, though its 
 outline could be detected ; but it more than ever presented the 
 appearance of being something which was floating in a basin 
 or hollow. In 1910 it again became visible, though only for 
 a few weeks, and now one can hardly say more than that its 
 place can be discovered. 
 
 The illustrations annexed will indicate the fact that during 
 
86 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 the red spot's visibility, dating from 1878, its original outline 
 was oval, and that, notwithstanding the loss of colour, which 
 marked many subsequent years, yet at times it seems to have 
 closed up and lost its oval shape. The question has been 
 mooted whether the oval spot of 1878, with its strongly defined 
 colour, could be identical with an elliptical ring which was 
 observed and occupied the same position in latitude in 1869 and 
 1870, but which did not possess any definite colour. That 
 elliptical ring seems to have disappeared unnoticed, but the 
 red spot of 1878 at one time showed signs of becoming itself 
 transformed into an elliptical ring and closing up. The red 
 spot, minus nearly or all its colour, seems still to be visible, 
 or at least traceable, but there is distinct evidence that it has 
 in the course of years moved on that is to say, does not 
 occupy the same position in longitude which it did when first 
 discovered, and for many years afterwards. 
 
 This history, though very condensed, will justify the remark 
 that there is something mysterious about this spot, for which 
 no counterpart can be found anywhere in the domain of 
 astronomy. It remains to be added that though we talk about 
 the red spot as having been discovered in 1877, there seems 
 considerable evidence that a spot of the same shape was 
 noticed very many years earlier : indeed, as far back as 1666, 
 as witness the accompanying copy of an old sketch (Fig. 129), 
 ascribed to Azout and Cassini jointly. 
 
 White spots have also been noticed of various sizes at various 
 times, and also occasionally dark spots, but no explanation of 
 the physical character of them is available. We have evidently 
 a good deal to learn respecting Jovian spots, and several 
 surmises have already been put forward. Whilst it has been 
 thought that some connection exists between Sun-spots as 
 regards their period and the position of Jupiter in its orbit, the 
 idea has been extended to the point that there is an identity 
 in time between the prevalence of spots on the Sun and spots 
 on Jupiter. Whether these spots stand to one another as 
 
FIGS. 109-116 
 
 PLATE XXXIII. 
 
 Jupiter's Red Spot and the Regions near (Denning). 
 
 - 861 
 
 i 1880, Nov. 19 
 3 1881, Dec. 7 
 5 1883, Oct. 15 
 7 1885, Feb. 25 
 
 M. 
 
 23 
 40 
 37 
 50 
 
 2 1881, Sept. 26 
 4 1882, Oct. 30 
 6 1884, Feb. 6 
 8 1885, May 9 
 
 H. M. 
 
 13 ii 
 
 16 10 
 
 9 29 
 
FIGS. 117-128 
 
 PLATE XXXIV. 
 
JUPITER. 
 
 cause and effect, or whether both are indications of disturbances 
 of cosmical origin from outside the solar system is a matter 
 on which no opinion can be pronounced with our present 
 limited knowledge. 
 
 As regards Jupiter's belts taken collectively it seems not open 
 to doubt that they exhibit from time to time not only distinct 
 traces of colour, such as pale purple, or brown, or orange, but that 
 this colour varies from time to time in a way which almost im- 
 plies that its greatest developement is coincident with a maximum 
 display of 
 Sun-spots. 
 This was 
 Browning's 
 idea, put 
 forth many 
 years ago ; 
 but I am 
 not aware 
 that any 
 recent ob- 
 server has 
 given his 
 attention to 
 the matter 
 from this 
 standpoint. 
 
 The satellites of Jupiter, 8 in number, have two distinct 
 histories, so to speak ; that is to say, that the newly discovered 
 ones have a history and individual characteristics which en- 
 tirely dissociate them from the 4 original satellites, as they 
 may be conveniently termed. The original 4 were discovered 
 by Galileo in January 1610 as the first-fruits of the application of 
 the telescope to the observation of Jupiter. A man named 
 Simon Marius, who put in a claim for priority over Galileo, 
 named them lo, Europa, Ganymede, and Callisto ; but this claim 
 
 North 
 Fig. 129. 
 
88 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 was so universally (but perhaps not rightly) considered to be 
 fraudulent that astronomers agreed to show their opinion by 
 ignoring the names prescribed by Marius, and simply to 
 identify the satellites by their order of distance from their 
 primary, designating them as I., II., III., IV. The condition 
 of things here implied remained undisturbed until 1892, when 
 a distinguished American astronomer, E. E. Barnard, dis- 
 covered a 5th satellite, very much smaller than all the others, 
 revolving round its primary within the orbit of I. Rather 
 more than 12 years later another American, Perrine, dis- 
 covered a 6th and a yth satellite, both revolving outside 
 IV. ; and in 1908 Melotte, an assistant at the Greenwich Ob- 
 servatory, introduced an 8th satellite to the astronomical 
 world. These various discoveries can be most conveniently 
 exhibited by resort to a table as follows : 
 
 Designation. 
 
 Discoverer and Date of 
 Discovery. 
 
 Mean 
 Distances in 
 Radii of 4. 
 
 Sidereal 
 Period. 
 
 
 
 
 d. h. 
 
 V. 
 
 Barnard, Sept. 9, 1892 
 
 
 O 12 
 
 I. 
 
 Galileo, Jan. 1610 
 
 6-0 
 
 i 18 
 
 II. 
 
 ?5 J ) J 
 
 9-6 
 
 3 13 
 
 III. 
 
 ? J 5 J > 
 
 i5'3 
 
 7 4 
 
 IV. 
 
 5< > 1 
 
 26-9 
 
 16 18 
 
 VI. 
 
 Perrine, Dec. 3, 1904 
 
 
 251 
 
 VII. 
 
 ,, Feb. 1905 - 
 
 
 265 
 
 VIII. 
 
 Melotte, Feb. 28, 1908 
 
 
 26 months 
 
 All these new satellites are, as may have been expected, so 
 very small as to be beyond the reach of any but the largest 
 telescopes in the world. I shall therefore here dismiss them, 
 and confine my remarks to the four old satellites. These well 
 deserve the attention of the amateur astronomer, not simply 
 because of the fact that they are easily visible in the most 
 ordinary telescopes, but because they are incessantly moving 
 
JUPITER. 89- 
 
 about ; and their movements give rise to certain phenomena 
 called transits and occupations. A transit occurs when a 
 satellite passes in front of the planet, as seen from the Earth, 
 and an occultation when the satellite passes behind the planet. 
 When an instance of the former phenomenon appears the 
 observer will see, by careful scrutiny, the satellite's disc and the 
 black shadow cast by the satellite on the planet. These two 
 appearances must be carefully discriminated, for the satellite 
 itself is apt to escape notice, whilst its shadow is mistaken for 
 the satellite itself. An occultation is, in its essential features, 
 the same as a total eclipse of the sun. In a total solar eclipse 
 the bright body of the sun is wholly concealed by the super- 
 posed Moon. Similarly, in an occultation of a Jovian satellite 
 the bright satellite is entirely concealed by the planet. But 
 there is this difference : in a solar eclipse the Moon, which 
 does the work, is not only opaque, but black ; but in a Jovian 
 occultation the occulting body which does the work, namely, 
 the planet, whilst it is opaque is nevertheless illuminated, 
 because nothing happens either to weaken or put an end to 
 the light which the planet, like every other planet, receives 
 from the Sun. These phenomena obtain full recognition in 
 the various national Nautical Almanacs, and the information 
 given in the British Nautical Almanac is borrowed by 
 Whitaker's Almanac, and so is brought within the reach of 
 everybody, and no further amplification of the subject is 
 necessary here. 
 
 Under ordinary circumstances the satellites exhibit simple 
 illuminated discs, but with adequate optical assistance it is 
 found that they have markings or shadings of irregular shape. 
 Comparing one with another, it would appear that III. is 
 commonly the brightest and IV. the faintest ; but no very 
 positive statement can be made as to I. and II., or even as 
 to the relative brilliancy of any one of the four compared with 
 the others, for it seems certain, or probable, that all of them 
 are subject to changes of brilliancy. There is no clear evi- 
 
90 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 dence of their ever showing any signs of colour. W.-H. Pick- 
 ering has noted the curious fact that, twice during each 
 revolution, and at intervals of 34 hours, the third satellite 
 exhibits a marked elliptical outline, and that its chief shading 
 is not a band, but is forked. He thinks also that there is 
 something abnormal in the circumstances of II. and IV. as 
 distinguished from I. 
 
 Observation of the satellites of Jupiter as far back as 1675 
 led to the discovery that light is not transmitted instantaneously 
 through space, but takes an appreciable time. A Danish 
 astronomer, Romer, was the hero of this. He found that the 
 observed times of the eclipses did not tally with the calculated 
 times, and that the differences were systematically affected 
 by opposite signs of error, according as Jupiter was near to 
 or remote from the Earth. This fact led him to suspect that 
 the varying differences in the distances was the cause of the 
 varying differences in the times ; in other words, the greater 
 the distance of the planet from the Earth the longer the time 
 occupied in the light making itself manifest to us on the 
 Earth. Romer's conclusions were that light travelled at the 
 rate of 192,000 miles per second, a conclusion remarkably near 
 the truth, considering Romer's inferior instruments, for by 
 more modern methods, with altogether superior instruments, 
 it has been found that Romer's figures are only wrong by 
 being about 2000 miles in defect, the true velocity being 
 194,000 miles per second. 
 
 Jupiter revolves round the Sun in rather more than iif years 
 at a mean distance of 483,000,000 miles. The eccentricity of 
 its orbit is small, so that its greatest possible and least possible 
 distances do not differ very much from its mean distance, 
 being 506,000,000 miles and 460,000,000 miles respectively. 
 The planet's apparent diameter varies between 60" in Oppo- 
 sition and 30" in Conjunction. The equatorial diameter is 
 rather more than 88,000 miles, making Jupiter the largest 
 planet in the solar system. 
 
SATURN. 9 1 
 
 SATURN. 
 
 There are probably very few people who have any knowledge 
 of anything scientific who have never heard of Saturn and 
 its ring. The planet, though inferior in lustre to Mars and 
 Jupiter, is always to be found without difficulty when in a dark 
 sky, shining, as it does, like a star of the second or third 
 Magnitude. It compares, however, unfavourably with its rivals 
 because it has a dull, leaden hue. 
 
 Though its appendage is often spoken of as "the Ring," 
 using the word in the singular number, yet it is really a system 
 of rings which surrounds the planet, and the number grows 
 with the size of the telescope used to scrutinise it. Whilst a 
 small telescope will only show one ring, a larger one will 
 show this one divided into two ; a still larger one will show 
 the outermost of the two again divided into two. In addition 
 to these there is a third main ring, which is the innermost of all. 
 Unlike the rings just spoken of, this innermost ring is not 
 bright, but dusky ; and the name originally given to it on its 
 discovery, rather more than half a century ago, of the " crape 
 ring," has not quite fallen into disuse, and is not altogether 
 inappropriate. 
 
 The history of the discovery of this ring is rather curious, 
 and suggests a mysterious origin and developement of it. In 
 1838 a distinguished German astronomer, J. G. Galle, pub- 
 lished an observation in which he said he had noticed a 
 shading-off of the innermost bright ring towards the planet. 
 His remark seems not to have attracted any particular notice 
 until 1850, when G. P. Bond in America, and Dawes in Eng- 
 land, independently discovered the dusky ring, and recognised 
 it distinctly to be a ring, but transparent in so far that the body 
 of the planet could be seen through it. 
 
 This dusky ring is now a recognised feature of Saturn, and 
 it would seem to be wider and more easily visible than for- 
 
92 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 merly, and a division of the dusky ring into two rings has been 
 suspected. The germs of its discovery are to be seen in Galle's 
 note of 1838 ; whence, perhaps, it is permissible to suggest that 
 the ring has gone through stages of developement during the 
 last three-quarters of a century. There is no trace in the 
 writings of either of the Herschels of their having detected any 
 traces of a ring inside the innermost bright one, though it must 
 be confessed that Picard in 1673, an< ^ Hadley in 1723, saw 
 something which might perchance be identifiable with the dusky 
 ring of the observers of the igth century. 
 
 Saturn and its system, treated as a whole, is not only a very 
 remarkable and interesting object, regarded as a spectacle, but 
 every 30 years undergoes interesting transformations which 
 must now be described. For convenience of reference it is 
 customary to call the outermost bright ring A, the innermost 
 bright ring B, and the dusky ring C. 
 
 Figs. 136-137 show the interior edge of the crape ring as 
 drawn in March 1888 by J. G. E. Elger. The irregularities 
 are very noteworthy, but I am not aware that they have ever 
 been confirmed ; at any rate, in anything like the form 
 suggested by Elger. 
 
 Though under ordinary circumstances that is to say, during 
 a considerable succession of years we see Saturn as a ball 
 surrounded by its rings, yet, owing to the orbit of Saturn being 
 inclined to the plane of the Ecliptic, we see the rings at inter- 
 vals either opened out very wide or not opened out at all, but 
 presented edgeways. 
 
 Perhaps this will be made a little more clear by giving some 
 dates. In 1907 the Earth was in the plane of the rings ; they 
 were more or less invisible for a short time (October 1907 
 January 1908), being placed edgeways to the view of us on the 
 Earth. In 1907 the Sun began to illuminate the southern side 
 of the rings, after having for 14! years shone upon the northern 
 side. After 1907 the planet moved on, the rings beginning to 
 open out and become wider every year until 1915, when they 
 
FIGS, 130-132 
 
 PLATE XXXV. 
 
 Feb. 1887 (Terby). 
 Saturn. 
 
FIGS. 133-135 
 
 PLATE XXXVI, 
 
 July 30, 1899 (Antoniadi). 
 
 Jan. 27, 1912 (Phillips). 
 
 Saturn. 
 
 [93 
 
SATURN. 
 
 will attain their maximum breadth. After that they will again, 
 to our vision, become narrower. 
 
 When 1922 is reached the planet will have accomplished one- 
 half (approximately) of a revolution round the Sun, and will 
 again have reached the condition of being seen edgeways, the 
 sun beginning to illuminate the northern side of the rings. 
 For the previous 14! years we shall have seen one and the 
 same side of the rings, but henceforth for 14! years to come 
 we shall see, also continuously, for that period the same side of 
 
 Fig. 136. Ring C, March 21, 
 1887. 
 
 Fig. 137.- Ring C, March 27, 
 1887. 
 
 the rings : but it will be the opposite side to what we had seen 
 previously, because now the planet with its rings will have 
 passed to the opposite side of the Ecliptic. 
 
 Continuing our predictions, on or about 1928 the rings will 
 again have attained their maximum opening, but we shall see, 
 of course, the opposite side of them to what we saw in 1914. 
 Continuing our calendar of changes, the rings will, about 1936, 
 reach the same stage identically as had been reached in 1907 ; 
 that is to say, the planet will have completed one entire circuit 
 of the Sun, and will start again on precisely the same sue- 
 
94 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 cession of changes as that with which it had commenced in 
 1907, the Sun beginning again to illuminate the southern side 
 of the rings. 
 
 From the foregoing it will be clear that from now, and for 
 several years after the first publication of this book, the planet 
 will be at its best for observation in telescopes of all sizes. 
 
 The changes which have just been sketched out involve, 
 both theoretically and practically, many incidental details too 
 numerous to be gone into here ; but the reader will no doubt 
 understand that, as we are dealing not with a ring all in one 
 piece, but with a bundle of rings, so to speak, the effects are 
 somewhat complicated. One of the most natural effects is that, 
 when the edgeways stage is nearly reached, or just passed, 
 instead of the edge being a continuous line of light, it is a 
 broken line. The diagrams annexed will make this sufficiently 
 clear without any detailed explanation. 
 
 The outer edge of the outer ring is visible throughout, but 
 with extreme difficulty when standing by itself as between b 
 and c and f and g, and towards a and h but the brighter 
 portions from c to d and from e to f indicate that the light of 
 the outer ring is reinforced by that reflected by the inner edge 
 of the inner ring. The bright knots at b and g represent the 
 light of the outer ring strengthened by the concurrent reflection 
 from the inner edge of the outer ring, and the outer edge of 
 the inner ring, which last-named reaches us through the inter- 
 space between the two main rings, which is often called the 
 Cassini Division, from the name of its discoverer, J. D. Cassini. 
 
 One curious fact seems well established, namely, that the 
 rings are not concentric with the ball. This is a peculiarity 
 which one would not naturally have expected, but it has been 
 shown mathematically to be essential to the stability of the 
 ring system ; and if this feature did not exist, and if the rings 
 did not revolve round the planet, they would collapse on to the 
 planet. Thus expressed, the statement suggests that the rings 
 are solid, but it is generally considered that such is not the case ; 
 
SATURN. 
 
 95 
 
 on the contrary, that they are made up of myriads of discrete 
 particles of matter, so closely compacted together that to our re- 
 mote eyes they appear as a solid mass. Considered as a system 
 the rings are sensibly more luminous than the planet, and B is 
 brighter than A, B itself being least bright at its inner edge. 
 
 Measurements and opinions vary as to the thickness of the 
 rings. Sir J. Herschel thought that 250 miles would be an 
 outside limit for the thickness ; G. P. Bond put it at no more 
 
 Fig. 138. Saturn, Feb. 7, 1890. 
 
 Photographed at Mount Wilson, U.S. 
 
 than 40 miles ; probably 100 miles is near the mark. The 
 general dimensions may be exhibited in the following table, 
 which represents the latest and best measures obtainable, being 
 those of Prof. E. E. Barnard, put forth in 1895. 
 
 Miles. 
 
 Outer diameter of outer ring .... 172,310 
 
 Inner diameter of outer ring .... 150,560 
 
 Outer diameter of inner ring .... 146,020 
 
 Inner diameter of inner ring .... 110,200 
 
 Inner diameter of crape ring .... 88, 190 
 
 Width of the Cassini division .... 2,270 
 
96 THE MOST INTERESTING AND FAMILIAR PLANETS. 
 
 To the foregoing may be added, from another source, 18,640 
 miles as the distance of the ring B from the ball. 
 
 Thus far I have said nothing about the physical appear- 
 ance of the ball. It has certain features in common with 
 Jupiter that is to say, faint belts may often be seen 
 upon it, and occasionally a bright spot ; but these are very 
 rare. 
 
 Taking the planet as a whole, it was suggested by Lassell 
 that the South Pole is generally darker and more bluish in 
 tinge than the North Pole. The general hue of the planet is 
 yellowish-white, which to the naked eye is commonly regarded 
 as dull grey a seeming contradiction. There exists no 
 clear evidence that Saturn has an atmosphere in the usual 
 sense of the term, though its existence seems probable, from 
 the central portions being brighter than the circumference. 
 Theoretically it should exhibit in Quadrature a slight phase, 
 but it must be so small that no wonder none has ever been 
 noticed. 
 
 Saturn is attended by satellites, 10 in all, of such diverse 
 sizes that they furnish excellent tests for telescopes. The 
 largest is that known as Titan, which is supposed to be about 
 2700 miles in diameter. All the satellites have received 
 name.s, and those which come next in order of visibility are 
 lapetus, Rhea, Dione, Tethys, and Enceladus. Telescopes of 
 the largest size are required to show Mimas, Hyperion, Phoebe, 
 and Themis. It is obvious, from the foregoing statement, that, 
 with the exception of Titan and lapetus, amateur observers 
 will not need to give much attention to these satellites. Titan 
 may be compared to a star of Mag. 8 and lapetus to one of 
 Mag. 9 ; but lapetus is generally considered to vary in 
 brightness, being brightest when in the western part of its 
 orbit. 
 
 Saturn revolves round the Sun in 29^ years at a mean 
 distance of 886,000,000 miles, in an orbit slightly eccentric. 
 Its apparent diameter varies between 1 5" in Conjunction and 20" 
 
SATURN. 97 
 
 in Opposition. According to Barnard, its equatorial diameter 
 is 76,470 miles, and its polar diameter 69,770, which figures 
 imply a polar compression of ^. This result is not altogether 
 in accordance with the results of previous measures which 
 have made the compression more considerable. Hind put it 
 as much as i. 
 
CHAPTER VII. 
 THE LESS KNOWN PLANETS* 
 
 The Planets of this chapter of little interest to the amateur. History of 
 the discovery of Uranus. Difficulties as to its orbit. Siispicions of 
 the orbit being disturbed bv another planet. The search for it. 
 The researches of Adams and Leverrier. The discovery of Neptune. 
 Brief description of the planet. 7/5 one satellite. The Minor 
 Planets. First organised search for them. Early discoveries. 
 Recent discoveries facilitated by photography. The planets now 
 very numerous. And few of them of any interest. Their fantastic 
 names. Some particulars of the first four. Summary respecting 
 their orbits. 
 
 THE planets which will come under our notice in this chapter 
 are of no intrinsic interest whatever to the amateur star-gazer, 
 who, if he tried to find them, would in general have great 
 difficulty in doing so ; and, having found half a dozen of the 
 brightest of them, which perhaps he might do, he would very 
 quickly come to the conclusion that they were not worth the 
 search. In spite of this, however, certain of them have great 
 historic interest, the tale of which must now be. unfolded. 
 
 On the evening of March 13, 1781, Sir W. (then Mr.) Herschel 
 was examining some small stars near H Geminorum, and one 
 of them attracted his special attention. With a view of seeing 
 what he could make of it with a stronger eye-piece, he replaced 
 the eye-piece which he had been using by one of greater 
 power. 
 
 A star thus examined by the use of different eye-pieces always 
 retains its stellar character of rays emanating from a point ; but 
 
 9 8 
 
URANUS. 99 
 
 Herschel found that the object which he had under view did 
 not behave thus, but that increasing the power increased the 
 diameter considerably, thus proving that, whatever the object 
 was, it was at any rate not a star. Apparently no suspicion 
 entered his head that he was looking at a new planet, for the 
 idea of there being any new planets never, up to that time, 
 seems to have entered seriously into anybody's head. 
 
 Finding that the object was in motion amongst the stars, he 
 jumped at the conclusion that he had found a new Comet, 
 and he announced it as such to the Royal Society on April 26. 
 But previously to this, as early as March 17, the stranger 
 had been examined by Maskelyne, the Astronomer Royal, at 
 Herschel's instigation. Maskelyne seems to have suspected 
 the planetary nature of the new body almost from the first. 
 Notice of the discovery of something having been made public 
 the stranger was observed at various European observatories 
 for many weeks, still treated as a comet. 
 
 When its movements were subjected to calculation on the 
 supposition that it was a comet, and, like most comets, one 
 moving in a parabolic orbit, it was soon found that this sup- 
 position broke down, its course, on the parabolic theory, being 
 falsified more and more as the observations were prolonged. 
 
 The final stage in the researches as to the real nature of the 
 newly discovered visitor were reached when Lexell authorita- 
 tively announced that the object which astronomers had been 
 following was not a comet but a planet, hitherto unknown, 
 revolving round the Sun in a nearly circular orbit. 
 
 This announcement came as a shock, in a certain sense, to 
 many people, because it seems to have been thought that the 
 number of the moving luminaries visible to the naked eye, 
 recognised as 7 from the earliest ages, 1 was a perfect number 
 which it was almost an outrage to challenge. A long controversy, 
 which was not really finally closed till the middle of the 
 
 1 The Sun, Mercury, Venus, the Earth, Mars, Jupiter, Saturn. The Sun was 
 always, in early times, considered a moving body. 
 
100 THE LESS KNOWN PLANETS 
 
 i gth century, arose as to the name to be given to the new 
 planet. Herschel, in pursuance of the fashion of the times, 
 proposed to call it the " Georgium Sidus,"a suggestion naturally 
 not very acceptable to foreigners, nor indeed very reasonable. 
 The French proposal, put forth either by Lalande or Laplace, 
 to call it " Herschel" was equally irrational ; and, finally, there was 
 a large preponderance of opinion in favour of a mythological 
 name which would harmonise in some sense with the name of 
 the next nearest planet, Saturn. Agreement thus far did not 
 immediately settle the matter, and Neptune, Astraea, Cybele, and 
 Uranus all had their supporters. Finally, however, the last of 
 these names, urged by Bode, gained the day. 
 
 The conservatism of the English mind even in things 
 astronomical was shown by the fact that the names "Herschel " 
 and " Georgium Sidus " in one shape or other were kept up for 
 a very long time in England, and the word " Georgian " did 
 not disappear from the Nautical Almanac until the volume 
 for 1850 published in 1846. The actual name used for many 
 years had been in the English form, " The Georgian," instead of 
 Georgium Sidus, which only lasted a very few years after 1781. 
 
 The question, Did anybody catch sight of Uranus before 
 Herschel ? naturally suggested itself to astronomers ; and search 
 amongst old records of observations of stars eventually led 
 to it being ascertained that the planet had been observed 
 on 20 occasions between 1690 and 1771 ; by Le iMonnier, 
 in particular, on no less than 12 occasions. Had this 
 astronomer possessed a methodical, orderly mind it seems 
 almost certain that he could have anticipated Herschel in 
 determining the planetary nature of the " star " so many times 
 seen by him ; but he was not a man of an orderly mind, if we 
 may rely upon Arago's statement that he had once been 
 shown by Bouvard one of Le Monnier's observations of the 
 planet written on a perfumer's hair-powder paper-bag. 
 
 The physical appearance of Uranus, owing to its great 
 distance from us, and small apparent size at its best, need not 
 
JRANTJS. - 10 1 
 
 detain us. Suffice it to say, therefore, that belts and spots on 
 it have been suspected by observers with telescopes sufficiently 
 powerful to grapple with it. It has also been thought to have 
 some inherent light of its own besides what it derives from the 
 Sun. 
 
 Sir W. Herschel thought he had discovered 6 satellites as 
 belonging to Uranus, but it is now recognised that only two of 
 these were genuine discoveries. Two other satellites were found 
 in 1847 by Lassell and O. Struve respectively, and the assured 
 number stands at present only at 4. They have been named 
 Ariel, Umbriel, Titania, and Oberon, in the order of distance 
 from the planet, reckoning outwards. 
 
 Uranus revolves round the Sun in rather more than 84 years 
 at a mean distance of 1,781,000,000 miles. The orbit is some- 
 what less eccentric than that of Jupiter. Its apparent diameter 
 varies but slightly, and may be taken at something under 4", the 
 real diameter being about 31,000 miles. One of the difficulties 
 which had to be solved in connection with Uranus was the 
 choice of a symbol for it. The one in use is a composite affair 
 embracing a capital H, the initial of HerschePs surname ; but 
 the Germans employ one " made in Germany " which 
 does not differ much from the symbol in common use for 
 Mars. 
 
 The next section will bring the name of Uranus before us 
 again in a very striking connection. 
 
 NEPTUNE. 
 
 The story of the discovery of the planet Neptune has often 
 been told, but it will bear repetition ; at any rate, this volume 
 would not be complete without the story being told again, even 
 if only in a concise form. It involves, indeed, the history of 
 Uranus, some part of which must be given as a preface to the 
 story of Neptune. It has already been stated that Uranus had 
 been observed on numerous occasions before the official date of 
 
102 THE LESS KNOWN PLANETS. 
 
 its discovery by W. Herschel, and that these observations 
 began as far back as 1690. 
 
 It is the practice of astronomers, in calculating the orbit of a 
 new planet or comet, to base their calculations on as long a 
 chain of observations as possible, and from the undoubted fact 
 that when they began to calculate the path of Uranus round the 
 Sun they were able to start their chain from as early a date 
 as 1690, they had great hopes that very trustworthy details of 
 the orbit would soon be evolved. The man who took this 
 matter in hand was the French astronomer, Alexis Bouvard. 
 
 Bouvard, who in 1821 produced his first detailed results, 
 was obliged to confess that those results were very unsatis- 
 factory, in so far that those which depended upon the careful 
 observations made in 1781-1820 would not harmonise with those 
 made during the 91 years prior to 1781. He thought only of 
 one way of getting over the difficulty, and that was by the 
 summary process of rejecting all the earlier observations as 
 worthless. 
 
 For a while this seemed to remove all difficulties, and the 
 conclusions from theory published in 1821 and based on the 
 then recent observations, appeared to fit in quite satisfactorily 
 with the observations then being made. But this happy state 
 of things only lasted a few years. Discordancies soon appeared 
 between the places which ought to have been occupied in the 
 heavens by Uranus according to Bouvard's theory of the 
 character of its orbit and the places in which, by observation, 
 the planet was actually found. It seemed to be affected by 
 some influence which at one time pushed it forwards and at 
 another time pulled it backwards in its orbit. 
 
 It gradually became certain that there was some cause at 
 work which disturbed the planet's movements, and the con- 
 clusion was eventually arrived at that the cause was some 
 unknown planet revolving round the Sun in an orbit outside 
 that of Uranus. An English amateur, the Rev. T. Hussey, 
 seems to have been the first to have put forward this idea in 
 
NEPTUNE. 103 
 
 a positive form, which he did to Professor G. B. Airy, the 
 Astronomer Royal, but who had been Professor of Astronomy 
 in the University of Cambridge. 
 
 Other astronomers accepted the idea, but the first to take 
 overt action was a young Cambridge Undergraduate, J. C. Adams, 
 who as early as 1841 made up his mind to investigate the 
 question. Lack of time prevented him seriously starting his 
 labours until 1843. He carried them on for if years on the 
 supposition that there really was an undiscovered planet, and 
 in October 1845 he forwarded to Airy provisional elements of 
 the orbit and probable mass of a planet which would explain 
 the irregularities in the movements of Uranus. This, on the 
 theoretical side of the question, was the settlement of the 
 question, but, most unfortunately for the credit both of Adams 
 and Airy, the latter ignored at the time the young Cambridge 
 student and his labours and conclusions. 
 
 The scene now changes for a time to France. In the summer 
 of 1845 a young Frenchman, U. J. J. Le Verrier, of Paris, took 
 up the question of the anomalous movements of Uranus, and in 
 November of that year published his first Essay to show what 
 was not the cause disturbing the orbit of Uranus. A few 
 months afterwards, namely in June 1846, he published a second 
 Essay, in which he showed what was the cause, namely, the 
 attraction exercised by an unknown planet. He assigned 
 elements to it, just as Adams had done 8 months previously. 
 
 A copy of this second Essay reached Airy on June 23, and 
 when he found how close was the accord both between the sug- 
 gested elements and the suggested position of the planet in the 
 heavens, as assigned by the two young mathematicians working 
 in ignorance of one another, it at last dawned upon him that 
 perhaps Adams's labours were not so unworthy of consideration 
 as apparently he had thought when they first came into his 
 possession many months previously. Impressed for the first 
 time, he communicated with Professor Challis, at Cambridge, 
 who had the command of a large telescope suitable for hunting 
 
104 THE LESS KNOWN PLANETS. 
 
 up the planet, and Challis began his search on July i ; but he 
 was confronted by one serious difficulty : he possessed no star- 
 map of the particular part of the heavens in which it might be 
 expected that the planet would be found. He therefore had to 
 make a map for himself, and this of course was a time-taking 
 matter which hindered rapid progress. However, he eventually 
 prepared the necessary chart, and when it was ready he set to 
 work to use it ; but it was not until September 29 that he found 
 an object whose appearance attracted his attention. This 
 subsequently proved to be the planet he was searching for. 
 
 Further consideration showed that he had observed it, 
 regarding it as a star, on August 4 and 12, and that the sup- 
 posed star of August 12, was missing from the chart of 
 July 30. 
 
 Meanwhile, still in ignorance of what was going on in 
 England, Le Verrier published in August a third Essay assign- 
 ing more positively the probable position of the planet in the 
 heavens. He sent a summary of this revised information to 
 Encke, the Director of the Berlin Observatory, and invited him 
 to examine the heavens in and near the predicted place. 
 Encke, fortunately, had just become possessed of a newly 
 published map of the locality where the planet was expected 
 to be found, and therefore he was not called upon to waste 
 time in making a map for himself, as Challis had been obliged 
 to do. 
 
 Encke had with him two young assistants, whose names 
 afterwards became famous in the astronomical world, J. G. Galle 
 and H. L. D'Arrest. These men, under Encke's directions, set 
 to work the same night that Le Verrier's letter arrived, Galle 
 calling out one by one the stars visible in the telescope, whilst 
 D'Arrest checked the map. This work had gone on for a 
 certain time when Galle found what seemed to be an 8th mag. 
 star which was not marked on the map. It was seen again on 
 September 24, and, having moved, was soon proved to be the 
 planet wanted. An examination of the dates just given will 
 
NEPTUNE. 105 
 
 make it quite clear that the honour of the discovery was shared 
 in fairly even proportions by England and France. 
 
 Adams and Le Verrier both assigned a position for the 
 planet which proved to be nearly true and substantially 
 identical (with a slight preponderance in favour of Le Verrier), 
 whilst Challis was the first to find the planet, and Galle the 
 first to recognise that the object seen was the planet. It 
 should be added that it was not until October i, two days after 
 he had suspected that he had found the planet, that Challis 
 became aware of Galle's definite conclusion arrived at six days 
 previously. In the language of the gamester, we may with 
 perfect accuracy say "honours divided." 
 
 It was a long time (many years, in fact) before French men 
 of science settled down philosophically to accept the verdict, 
 which may now, however, be regarded as the verdict of the 
 world, though even to this day one may find French writers 
 glossing over or suppressing Adams's name in connection with 
 Neptune's discovery. 
 
 The remarkable feature about it was that two men of 
 different nationalities, working in different ways, with different 
 materials, each unknown to the other, should have fixed the 
 position in the heavens of a planet which nobody had ever 
 seen, accurately within 2^ in Adams's case, and within about i 
 in Le Verrier's case. I may well end my statement of the 
 matter in the words of Hind : 
 
 " Such is a brief history of this most brilliant discovery, the 
 grandest of which astronomy can boast, and one that is destined 
 to a perpetual record in the annals of science an astonishing 
 proof of the power of the human intellect." 
 
 After much discussion " Neptune " was the name agreed 
 upon for the new planet. Galle suggested "Janus," but this 
 name was disapproved of as too suggestive of the idea that the 
 orbit of Neptune marked the entrance into the solar system 
 from outside. And perhaps it was well that this suggested 
 
106 THE LESS KNOWN PLANETS. 
 
 alternative name was rejected, now that we seem drifting into 
 the belief that there is yet another planet farther off than 
 Neptune waiting to be discovered. 
 
 Information is sadly lacking as to the physical appearance of 
 Neptune, owing to its immense distance and small apparent 
 size. Markings in the nature of belts, and even a ring, have 
 been hinted at by several observers ; but it may be said that 
 practically we know nothing on the subject. If a ring existed 
 it would only open out every 82 years, being the point of a semi- 
 revolution round the Sun ; so it might be many years yet before 
 its existence could be certainly known. 
 
 The existence of one satellite seems to be assured, and a 
 second has been suspected, but here again there is a great lack 
 of assured knowledge, and it is not a little surprising that, with 
 the large telescopes lately brought into use, especially in 
 America, so little attention should have been given to Neptune. 
 
 Neptune revolves round the sun in 164 years at a mean 
 distance of 2,791,000,000 miles. The eccentricity of the orbit is 
 small. The planet's apparent diameter only varies between 
 2'6" and 2*8". Its true diameter is about 37,000 miles. 
 
 THE MINOR PLANETS 
 
 The discovery of the planet Uranus had other after-influences 
 besides leading to the discovery of Neptune. The fact that the 
 ancient tradition of seven moving heavenly bodies, and no more, 
 had been broken in upon put it into the minds of certain 
 astronomers that, as there was an eighth planet (Sun and Moon 
 having anciently been treated as planets), namely Uranus, why 
 not others ? 
 
 The actual circumstances which gave a practical start to the 
 idea that there were more planets to be found if they were 
 looked for are rather curious. A certain J. D.Titius, of Wit- 
 temberg, in Germany, discovered the following curious 
 coincidences. 
 
THE MINOR PLANETS. 
 
 107 
 
 Take the numbers o, 3, 6, 12, 24, 48, 96, 192, 384, each of 
 which after the 3 is double its predecessor ; add 4 to each 
 number and we get 4, 7, 10, 16, 28, 52, 100, 196, 388. 
 
 Now these numbers approximately represent the distances of 
 the planets from the Sun, taking the Earth's distance as the unit 
 or standard, calling it 10. 
 
 This statement will be more clear if it is tabulated thus : 
 
 Planets. 
 
 Mercury . 
 
 Venus . ... 
 
 Earth . 
 
 Mars 
 
 [Ceres, not known in 1772] . 
 
 Jupiter 
 
 Saturn 
 
 [Uranus, not known in 1772] 
 [Neptune, not known in 1772] 
 
 True distance 
 
 from Q. 
 
 Distance by 
 Bode's Law. 
 
 3'*7 
 
 4'00 
 
 7-23 
 
 7-00 
 
 lO'OO 
 
 lO'OO 
 
 !5'23 
 
 1 6-00 
 
 [27-66] 
 
 28-00 
 
 52-03 
 
 52-00 
 
 95-39 
 
 lOO'OO 
 
 [191-83] 
 
 196-00 
 
 [300-37] 
 
 388-00 
 
 Another German astronomer, J. E. Bode, became acquainted 
 with Titius's figures, and, adopting the idea as his own, and 
 noticing at that time (1772) that there was no planet represented 
 by the figures 28, 196, and 388, predicted that more planets 
 existed and should be looked for. It does not appear that 
 VV. Herschel was influenced in any way by the foregoing figures 
 as regards Uranus, but in 1800 some German observers, six in 
 number, assembled at Lilienthal and formed themselves into a 
 society of explorers, under Schroler as President, to search for 
 additional planets. Such zeal was soon rewarded, and the first- 
 fruits were the planets Ceres, Pallas, Juno, and Vesta. No 
 more seeming to be forthcoming, the work was abandoned in 
 1816 ; but a Prussian amateur named Hencke,at Driesen,took up 
 the work on his own account about 1830, but with no immediate 
 success. 
 
108 THE LESS KNOWN PLANETS. 
 
 The discovery of Neptune in 1846 infused new life into the 
 movement for hunting up small planets, one of which indeed, 
 afterwards named Astraea, had been found on December 8, 
 1845, by Hencke at Driesen, whose single-handed labour has 
 just been mentioned. The year 1846 produced none. Three 
 were found in 1847, one in 1848, one in 1849, three in 1850, and 
 two in 18.51. Thenceforward the discoveries became much 
 more rapid, and by the end of 1860 a total of 62 had been 
 reached ; 1870 brought the number up to in ; and since then 
 they have grown with ever-increasing rapidity up to the present 
 total, which exceeds 700. 
 
 The system of looking for them has latterly been materially 
 altered. For many years after the search was first begun it 
 was carried out very much on the lines on which the search for 
 Neptune was conducted, namely, by ocular comparison of the 
 stars visible in a telescope with maps of the stars in the same 
 locality ; but of recent years the extensive introduction of photo- 
 graphy has greatly facilitated the discovery of new planets. I 
 am very sceptical as to the usefulness of these discoveries being 
 continued. The actual interest attaching to these bodies is in 
 nearly every case nil, and the labour involved in keeping pace 
 with their record and in calculating their orbits is out of all 
 proportion to the ultimate useful result. That this would 
 appear to be the opinion of astronomers generally is shown by 
 the fact that practically the whole work is now concentrated in 
 German hands, no other nation seeming to pay much attention 
 to these planets. Under these circumstances, I shall sum up in 
 very concise form the rest of the information which I shall give. 
 
 It will excite no surprise that these planets are in a constant 
 state of confusion as regards their identity. Let us suppose 
 that one is found by having imprinted itself on a photographic 
 plate ; the question at once arises, Is it a new one ? or is it an 
 old one which, having been missing, has turned up again ? Here 
 are endless traps for the astronomical author who wishes to 
 make an accurate enumeration of these planets. It may also 
 
THE MINOR PLANETS. 
 
 109 
 
 be added that of those which have been found and duly enrolled 
 no fewer than sixty are now ticked off as "lost" very likely 
 lost for ever ; or, if rediscovered, may never have their positions 
 at rediscovery brought into touch with their positions years 
 ago, and so proof of their identity may never be attainable. 
 
 These objects have borne various generic names. " Minor 
 Planets " may now be taken as their recognised name, whilst 
 the name first proposed for them by Sir W. Herschel, 
 
 Fig. 139. How Minor Planets are recognised as such. 
 
 "Asteroids," though no longer recognised by the scientific 
 world, is nevertheless a designation not unfrequently met with. 
 This remark, in a lesser degree, applies also to the name 
 " Planetoid." As regards their individual names, at the out- 
 set names taken from the mythologies of ancient Greece and 
 Rome, together with the old Latin names, in some cases, of the 
 places of discovery, were almost exclusively employed ; but of 
 recent years, reasonable names having become exhausted, 
 
110 THE LESS KNOWN PLANETS. 
 
 invented and made-up names, many of them of the most 
 ridiculous and fantastic character, have been chosen. 
 
 Female Christian names abound, the origin of which will 
 often not bear investigation from the standpoint of dignity and 
 etiquette ; for instance, the planets Lumen, Bertha, and Zelia 
 are said to immortalise the daughters of a well-known French 
 astronomer. The difficulty now of finding new planets and of 
 getting hold of the older ones is sufficiently shown by the 
 successive deterioration which has taken place in the size of 
 those discovered as discoveries multiplied. The average 
 brightness of the first ten, reckoned in star magnitude, was 8J; 
 of the second ten it was 9^ ; of the third ten it was io ; of the 
 fourth ten it was n. From this average figure the average has 
 progressively gone down, and I suppose that none are now 
 found which are brighter than the I3th or I4th magnitude a 
 sufficient justification, I think, for saying that they are not 
 worth looking after. 
 
 The 4 oldest and Eros are really only those in the slightest 
 degree worth consideration. Ceres is sometimes as bright as 
 a star of the 7th mag., and sometimes shines with a reddish 
 tinge, and has been thought to possess an atmosphere. Pallas, 
 when nearest the Earth at Opposition, is of the 7th mag., and 
 is of a yellowish tinge. Juno is of the 8th mag., and reddish. 
 Vesta is the brightest of the lot, and occasionally rises to the 
 6th mag., shining with a light which some consider to be pure 
 white, while others ascribe to it a yellowish tinge. 
 
 After these 4 oldest and probably largest of the Minor Planets, 
 the only one which has any intrinsic interest or importance is 
 Eros. The annexed diagram, Fig. 140, shows the fact that 
 Eros, owing to the character of its orbit, comes on occasions 
 very near the Earth, and on that account is available for 
 enabling us to ascertain the distance of the Earth from the 
 Sun, and it has been so used accordingly. Unfortunately, its 
 existence was not known on the last occasion, in which it was 
 at its nearest distance to the Earth, which was in 1894, and it 
 
THE MINOR PLANETS. 
 
 Ill 
 
 will not again be at its least distance from the Earth until 
 1924. 
 
 As regards their sizes, Barnard has given the following 
 figures for diameter : Ceres 520 miles, Pallas 304, and Vesta 
 
 MARS 333 
 
 Fig. 140. The Orbits of Eros, Mars, and the Earth. 
 
 211. Except, perhaps, Juno, Hornstein thinks that none of the 
 others are larger than 25 miles in diameter, and most of them 
 much less from 1 5 to 5 miles. 
 
 One remarkable fact about these planets is that their orbits 
 
112 THE LESS KNOWN PLANETS. 
 
 are in many cases much more inclined to the Ecliptic than any 
 of the orbits of the older planets. Hence the term " ultra- 
 zodiacal planets" was once suggested. 
 
 Many orbits are eccentric to a very extreme degree ; No. 699 
 seems to have the most eccentric orbit, the eccentricity 
 amounting to 0*412, from which it follows that its perihelion 
 distance is 142,285,000 miles and its aphelion distance 
 292,871,000 miles remarkable extremes. 
 
 The least eccentric orbit is that of No. 699 (unnamed), in 
 which the eccentricity amounts to only o'oio. 
 
 The most inclined orbit is that of Pallas (2), in which the 
 inclination amounts to 34 44'. 
 
 The least inclined orbit is that of Ortrud, in which the 
 inclination amounts to only o 26'. 
 
 Perhaps it will appear hereafter that there is one other planet 
 with an inclination less than this, i893Y, whose inclination is 
 believed to be only o 18'. 
 
 The planet nearest to the sun is Eros (433), which revolves 
 round the Sun in 643 days, or 1*76 years. 
 
 The honour of being farthest off rests with Hector (624), 
 whose period is 12'! years. Hector has, as its nearest neigh- 
 bours, Achilles (588), Patroclus (617), and Nestor (659), all 
 three with periods only slightly less than 12 years. 
 
 After the discovery of Pallas, Olbers suggested that Ceres 
 and Pallas might be fragments of some larger planet shattered 
 by some great catastrophe. The idea sounds plausible, and 
 certainly is attractive, but is considered to be impossible on 
 mathematical grounds. 
 
CHAPTER VIII. 
 ECLIPSES. 
 
 The Principles of eclipses. Other kindred phenomena. Two anec- 
 dotes. The difference between eclipses of the Sun and of the Moon. 
 Total eclipses. Partial eclipses. Annual number of eclipses. 
 The Saros. Method of using the Saros. Eclipses of the Sun 
 considered. The accompaniments of a large partial eclipse of the 
 Sun. Of a total eclipse. The terror of savages. Instances of 
 this. The darkness. The fall of temperature. The red flames. 
 Baily's Beads. The Corona. Details relating thereto. The 
 Moon's shadow. Shadow-bands. Bushes of light. The Corona, 
 a solar appendage. Connection between its shape and spots on 
 the Sun. Coming eclipses. Eclipse expeditions. Eclipses of 
 the Moon. The Moon when totally eclipsed. Anecdote of Columbus. 
 Incident in the South African War. Transits of Mercury and 
 Venus. Method of measuring the Sun's distance. Transits and 
 eclipses of the satellites of Jupiter. Occultation of planets and 
 stars by the Moon. Occultation of stars and planets by planets. 
 
 THOUGH the title of this chapter is given as " eclipses " simply, 
 the reader will find, when he gets towards the end of it, that 
 it includes some other phenomena which are of kindred 
 character, and which are technically known as " Transits " and 
 " Occupations." 
 
 The word " eclipse " usually brings to one's mind certain 
 occasional events which are specially connected with the Sun 
 and the Moon, and which, so far as their principles are con- 
 cerned, are in the highest degree simple ; but, simple as they 
 are, it is strange how little they are understood even by people 
 of education and position, as the two following anecdotes will 
 show. 
 
 8 "3 
 
114 ECLIPSES. 
 
 Some years ago less than twenty there lived in the 
 
 town of two sisters, who were recognised as cultivated 
 
 and well-educated women. They had prepared to watch an 
 eclipse of the Moon which began on one day but ended on 
 another day, according to the customary civil reckoning ; that 
 is to say, it began late in the evening of one day, and ended 
 after midnight in the early hours of the next day. 
 
 Accordingly, the almanac gave the date as, we will say, 
 December 21-22. Through some mischance the sisters failed 
 to begin to watch the eclipse on the evening of the 2ist, and 
 comforted themselves by saying, " It is coming again to- 
 morrow night, because the almanac says that it will happen on 
 the 2ist and on the 22nd ! " 
 
 The second anecdote concerns the eclipse of the Sun of 
 
 August 28, 1905. A royal personage then at said to 
 
 a gentleman of her suite, " I want to see the eclipse to-day ; 
 please make the necessary preparations [smoked glass, etc.], 
 and call me at the proper time out on to the terrace." Of 
 course she received a suitable answer, which included the 
 words, "You must be ready at ten minutes to n." The hour 
 of 10.50 arrived; then 10.55 \ tnen Ir : st ^ no royal sight- 
 seer on the terrace. The gentleman sent a very pressing 
 message into the house, with the only result that a head 
 appeared out of an upper window, followed by the somewhat 
 irritable remark, " I'm coming ! why are you in such a 
 hurry ? " Which not unnaturally evoked the reply, " I'm not in 
 a hurry, ma'am ; but the eclipse is in a hurry, and you are likely 
 to lose the most striking feature of it." 
 
 Eclipses, commonly so-called, are either of the Sun or of the 
 Moon ; and according to the degree, considerable or incon- 
 siderable, of the loss of light involved, so they bear different 
 specific names. Eclipses of either luminary may be either 
 "total" or "partial,' 3 whilst an eclipse of the Sun may also 
 bear a third name : it may be " annular." 
 
 To understand the general principles of eclipses should not 
 
FIGS. 141 and 141 a 
 
 PLATE xxxvn 
 
 AN ERUPTIVE PROMINENCE. 
 
 A QUIESCENT PROMINENCE. 
 "Red Flames" on the Sun, now generally termed "Prominences." 
 
ECLIPSES OF THE SUN. 115 
 
 be a difficult matter, bearing in mind that eclipses of the Sun 
 and eclipses of the Moon depend upon totally different 
 principles. 
 
 The Moon, in the course of its monthly journey round the 
 Earth, passes, at the stage of New Moon always, not far 
 from the Sun, travelling either higher in the heavens or lower 
 in the heavens than the actual place of the Sun. But on rare 
 occasions it may happen to pass quite in front of the Sun. 
 This will result in an eclipse of the Sun. The eclipse will be 
 total if the Moon passes centrally over the Sun and the Moon 
 is suitably placed in its orbit to cover the whole of the Sun ; it 
 will be annular if the Moon, though centrally placed in front 
 of the Sun, is not large enough to cover the whole of the Sun ; 
 it will be partial if it passes only over the upper portion 
 of the Sun or the lower portion. Something also depends 
 upon the position on the Earth of the observer. One observer, 
 A. B., may be so placed that the centre of the Earth, the centre 
 of the Moon, and the centre of the Sun are all exactly in the 
 same straight line. A. B. will therefore see a central and total 
 eclipse. l 
 
 Another observer, A. B.'s brother, whom we will call B. B., is 
 on the Earth in a latitude several hundred miles more northerly 
 or more southerly than A. B. To such a one the Moon will 
 be displaced from the position in which A. B. sees it : B. B. will 
 therefore only see the Moon passing over the southern or the 
 northern part of the Sun. He will therefore only see a partial 
 eclipse. 
 
 If the Moon were always at the same distance from the 
 Earth, and Earth and Moon were always at the same distance 
 from the Sun, every eclipse might be total, and would be the 
 same ; that is to say, the Sun would always be covered with 
 the same overlap, and the time during which it remained 
 covered would be always the same. 
 
 But the distances referred to are not always the same ; they 
 
 1 Unless it is only an annular one, 
 
jl6 ECLIPSES. 
 
 vary considerably. It follows therefore that if, when the Moon 
 is nearest the Earth, the Sun should be at its farthest possible 
 distance from the Earth, the Moon would look its largest and 
 the Sun would look its smallest. This would have the effect of 
 making the overlap during totality the largest possible, and 
 therefore the duration of the Sun's invisibility the longest 
 possible. If, on the other hand, the Moon was at its greatest 
 distance from the Earth, and the Sun at its nearest, the Moon 
 would look its smallest and the Sun its largest. Under such 
 circumstances, the Moon would be too small to conceal the 
 whole of the Sun ; and such are the circumstances under which 
 the eclipse would be annular to an observer viewing it from 
 such a latitude on the Earth as would make the Earth, the 
 Moon, and the Sun to be in the same straight line. 
 
 Another consequence follows from the ever-varying position of 
 the Moon as regards its distance from the Earth. An eclipse 
 may be total at one place, but in the course of an hour or two 
 the Moon's distance from the Earth may have varied so that it 
 has become more distant and therefore looks smaller, and an 
 observer on the Earth and on the central line at the same time 
 will see that the apparent diameter of the Moon has become 
 diminished, so that it is no longer large enough to cover the 
 whole of the Sun. To such an observer the eclipse will rank 
 as an annular or semi-annular one. Such was the eclipse of 
 April 17, 1912. 
 
 Turn we now to eclipses of the Moon. Though, so far as 
 names go, such eclipses are either " total " or " partial," yet 
 the totality or partiality depends upon principles quite different 
 from those which bring about the same nominal results in the 
 case of the Sun. 
 
 The Earth and the Moon being both illuminated by the Sun, 
 both, of course, cast a shadow into space, just as every opaque 
 object put in front of a source of light has its shadow thrown 
 behind it. If, therefore, at the time that the Moon is in that 
 position of its orbit known as the Opposition (when it is on the 
 
FIG. 142 
 
 PLATE XXXVIII. 
 
 116] 
 
 Solar Eclipses visible in England, 1891-1922. 
 
FIG. 143 
 
 PLATE XXXTX. 
 
ECLIPSES OF THE MOON. 117 
 
 meridian at midnight), and Moon, Earth, and Sun happen to 
 be exactly (or nearly) in the same straight line, the Moon, in 
 its progress round the Earth, will plunge into the Earth's 
 shadow, either wholly or partly, and the result will be that 
 the Moon will be wholly or partly lost to the view of all the 
 inhabitants of the hemisphere which is turned away from the 
 Sun. The Moon, when completely plunged in the Earth's 
 shadow, may either become completely invisible or signs of its 
 presence in the sky may be obtainable from the fact that a faint 
 reddish tinge seems to pervade its surface, and so keeps it 
 dimly in view. This visibility or invisibility has nothing to do 
 with the principles of the eclipse ; but I shall discuss the 
 matter under another head later on. 
 
 It is now time to go somewhat more fully into details re- 
 specting these eclipses. If the orbits of the Earth and the 
 Moon were in the same plane an eclipse of the Sun would 
 happen once in every month at the epoch of New Moon ; and 
 an eclipse of the Moon would also happen every month at the 
 epoch of Full Moon ; but the Moon moves round the Earth 
 in an orbit which is inclined to the ecliptic at an angle of 
 about 5, and therefore it is only on occasions that the Moon 
 will be found immediately in front of the Sun so as to bring 
 about an eclipse of the Sun, or immediately behind the Earth 
 (looked at from the Sun), and so bring about an eclipse of the 
 Moon. The effect of this inclination, coupled with certain other 
 disturbed conditions which subsist with respect to the Moon's 
 orbit, brings about a result that the possible number of eclipses 
 in the course of a year are limited, and vary. There must 
 always be two, and cannot be more than seven, eclipses in a 
 year. When there are only two they must always be of the 
 Sun. In the case of the seven, five of them may be solar, in 
 which case only two can be lunar, though under no circum- 
 stances can there be more than three lunar eclipses in one 
 year, and in some years there may be none at all. 
 
 If the almanacs for a few successive years are consulted it 
 
Il8 ECLIPSES. 
 
 would seem that the succession of the eclipses is Very irre- 
 gular, yet that is not so in reality if the almanacs of 18 
 successive years are consulted, and, better still, the almanacs 
 of thrice that period, or 54 years, are examined. If either 
 or both of these things are done it will be found that eclipses 
 recur almost in the same order every 18 years 10 days, or in 
 every 54 years 31 days. 
 
 This fact was known more than 3000 years ago to the 
 Chaldaean astronomers. They called the scheme the " Saros," 
 and it furnished them, as it would furnish us, with the means 
 of predicting eclipses for any number of years in advance. 
 It does something more, for it not only enables the amateur 
 to predict eclipses for himself, but also enables him to say in 
 advance what will approximately be the path of an eclipse 
 across the Earth. If we take any given eclipse, say of the 
 Sun, visible at any particular place, a nearly similar eclipse 
 will be visible nearly in the same locality 18 years and 
 10 days later, but the locality will be a certain number of 
 miles different, and S. of the previous line of central eclipse. 
 
 To give a concrete instance. There was a total eclipse of 
 the Sun visible in the north of Norway on August 9, 1896, at 
 the hour of 4.30 in the morning. That eclipse will recur 
 on August 21, 1914, but the central line, still in Norway, will 
 be so many miles S. of the line of 1896, and the time will 
 be much more convenient, because it will be nearer the break- 
 fast-hour of most people. The gradual transformation of the 
 central lines of eclipses will be realised by a perusal of the 
 following particulars of the eclipse of the Sun of June 1295, 
 when it appeared at the North Pole. In 1367 it had got 
 forwards to the month of August, and southwards to the North 
 of Europe ; in 1439 it was visible all over Europe ; at its nine- 
 teenth appearance in 1601 it was central in London ; on May 5, 
 i Si 8, it was also visible in London, and was again nearly 
 central in the metropolis on May 15, 1836. At its next ap- 
 pearance on May 26, 1854, the central line passed over North 
 
ECLIPSES OF THE SUN. 1 19 
 
 Africa ; on June 6, 1872, it crossed France ; on June 17, 1890, 
 it crossed North Africa and Turkey in Asia ; on June 28, 1908, 
 it was central in Mexico, Florida, and across the Atlantic to 
 Senegambia. At its thirty-ninth appearance on August 10, 
 1980, the Moon's shadow will pass S. of the Equator, and, 
 as the eclipse will take place near midnight, it will be invisible 
 in Europe, Africa, and Asia, and visible only in South America. 
 At every subsequent period the eclipse will go more and more 
 towards the S., until at its seventy-eighth appearance on 
 September 30, 2665, it will go off at the South Pole of the 
 Earth, and therefore the series will have ended. 
 
 Thus far we have been considering eclipses of the Sun and 
 Moon as mixed up in regard to certain general principles ; but 
 we must now deal with solar and lunar eclipses separately, 
 because they differ so much in the details relating to their 
 observation that it is necessary to keep them distinct. An 
 eclipse of the Sun in cases where only a portion of the Sun 
 is obscured offers really no features of interest unless the 
 portion obscured is very large, not less than nine-tenths of the 
 Sun's diameter. When this amount of obscuration occurs there 
 are a few subsidiary occurrences calculated to interest the 
 student of nature ; for instance, the reduction in the sunlight 
 available for lighting up the landscape is very marked, and, 
 though not a cloud is visible, yet the sky puts on a dark, lurid 
 appearance suggestive of a severe thunderstorm being at hand. 
 The temperature of the air becomes much reduced, perhaps to 
 the amount of 5 Fahrenheit, or even more, and the personal 
 sensation of chilliness experienced is even greater than the 
 thermometer implies. Birds distinctly manifest their know- 
 ledge that something special is taking place, for, even if they 
 do not definitely go to roost, they are evidently uncomfortable 
 and suspicious. If any trees near are in leaf images of the 
 crescent Sun will be cast on flat surfaces such as a boarder 
 even a book, laid on the ground so that images of the Sun 
 may pass through the foliage. Finally, the maximum phase is 
 
t20 ECLIPSES. 
 
 accompanied by a sudden gust of wind. All these phenomena 
 were seen in different parts of England on the occasion of the 
 large eclipse of April 17, 1912. 
 
 It is when a total eclipse of the Sun happens that a solar 
 eclipse shows to the greatest advantage, many of the features 
 manifested being of a very sensational character, the excite- 
 ment of the spectators being greatly accentuated by the 
 rapidity with which the transformations take place, and the 
 limited amount of time available for looking at them. I am 
 here speaking of eclipses of the Sun observed by educated 
 and sensible people, who know all, or at any rate something, 
 about the matter. But when the spectators comprise ignorant 
 natives, whether Indians or Negroes or Aborigines generally, 
 a total eclipse of the Sun is usually the occasion of remarkable 
 scenes in which alarm and despair and anger are intermingled. 
 From the various records which I have gathered up of such 
 scenes, I select the following as typical of many such narra- 
 tives. But the first quotation will show that we need not go so 
 far off as the lands inhabited by Indians for an example of an 
 eclipse panic. 
 
 The Earl of March quotes from a letter written by a certain 
 Sir Thomas Prendergast, from Pantglase, under date of 
 August 3, 1748, the following sentence : 
 
 " I would have spun out a few lines more in relation to the 
 eclipse, such as the care taken to get in all the hay before it ; 
 prayers said in churches, preparatory and preventive ; and 
 many other demonstrations of terror and religion." l 
 
 What happened on the occasion of the total eclipse of 
 July 29, 1878, was thus described in an American newspaper 
 by a spectator resident at Fort Sill, Indian Territory : 
 
 " On Monday last we were permitted to see the eclipse of the 
 Sun in a beautiful bright sky. Not a cloud was visible. We 
 had made ample preparation, laying in a stock of smoked glass 
 
 1 "A Duke and his Friends" (London, 1911). 
 
FIG. 144 
 
 PLATE XL. 
 
 The Solar Corona, July 29, 1878 (/. P. Murphy}. 
 
 I20l 
 
FIGS. 145-146 
 
 PLATE XL1. 
 
 The Solar Corona, August 29, 1886 (Harvard Annals, xviii.), 
 
 The Solar Corona, Dec. 22, 1889 (Perry}. 
 
TOTAL ECLIPSES OF THE SUN. 121 
 
 several days in advance. It was the grandest sight I ever 
 beheld; but it frightened the Indians badly. Some of them 
 threw themselves upon their knees and invoked the Divine 
 blessing ; others flung themselves flat on the ground, face 
 downward ; others cried and yelled in frantic excitement and 
 terror. Finally, one old fellow stepped from the door of his 
 lodge, pistol in hand, and, fixing his eyes on the darkened Sun, 
 mumbled a few unintelligible words, and, raising his arm, took 
 direct aim at the luminary, fired off his pistol, and, after throwing 
 his arms about his head in a series of extraordinary gesticula- 
 tions, retreated to his own quarters. As it happened, that very 
 instant was the conclusion of totality. The Indians beheld 
 the glorious orb of day once more peep forth, and it was 
 unanimously voted that the timely discharge of that pistol 
 was the only thing that drove away the shadow and saved 
 them from the public inconvenience that would have certainly 
 resulted from the entire extinction of the Sun." 
 
 We will now go back to the general concomitants of a 
 total eclipse of the Sun as they present themselves to a rational 
 observer, who can deal with the matter in a calm and philoso- 
 phical spirit. When the Moon has reached the Sun, and its 
 forward limb has broken in upon the Sun's disc, nothing 
 remarkable is to be noted until the Moon's movement has so 
 far progressed as to have made a substantial encroachment on 
 the Sun. When perhaps half of the Sun has become obscured 
 a fall in the temperature of the air around the observer will 
 begin to be felt. The next thing which will be noticed will be 
 a change in the appearance and colour of the sky. The 
 ordinary blue will become much deeper, soon passing into a 
 dull dark slate colour which will eventually reach purple. 
 
 This purple colour has been likened to a canopy overhanging 
 the sky nearly, but not quite, down to the horizon ; for the 
 lowermost strip, so to speak, of the canopy reaching actually to 
 the horizon is not purple, but orange, more or less, in colour, 
 which hue is due to the fact that the Sun's light which reaches 
 the observer from the horizon has to pass through a very thick 
 
*22 ECLIPSES. 
 
 stratum of atmosphere which absorbs much of the violet light of 
 the spectrum. 
 
 This will indicate that the total phase is at hand, and that 
 instant and the two or three minutes (according to circum- 
 stances) which will follow constitute the high-water mark of the 
 excitement of the spectators. Though the duration of totality 
 might, according to theory, reach such an extreme as seven 
 minutes, this extreme never is reached, and from two to four 
 minutes is the general duration of the eclipses which have been 
 observed during recent years. This means that an immense 
 amount of work, such as photographing and note-taking, has to 
 be compressed into a very limited amount of time, and amid 
 much nervous excitement. 
 
 The first feature which suddenly springs into view are jets of 
 Red Flames, now more generally called Prominences, which 
 spring up at various points round the Sun's circumference. It 
 was at one time supposed that these Red Flames were only to 
 be seen during total eclipses, but modern instruments and 
 methods have brought it about that they can always be seen, 
 so far as their positions and shapes are concerned. These 
 Red Flames are now recognised to be masses of incandescent 
 gas mixed with other gases, one of which, now called helium, 
 is not found on the Earth. 
 
 Almost coincident with the appearance of the Red Flames, or 
 even before them, numerous beads of light spring up along the 
 forward limb of the Moon. These are known as " Baily's 
 Beads," having been first systematically described by the late 
 Mr. Francis Baily in 1836. Their explanation is somewhat 
 obscure. It has been supposed that they are outstanding 
 portions of the solar disc peeping through lunar valleys, whilst 
 the adjacent mountains project far beyond the smooth circular 
 outline of the Sun's disc, which is no longer visible as a con- 
 tinuous circle. This may be one of the causes which give rise 
 to the Baily's Beads, but the optical phenomenon known as the 
 irradiation of light is no doubt a contributory cause. 
 
TOTAL ECLIPSES OF THE SUN. 123 
 
 The most important feature of a total eclipse of the Sun is 
 the Corona, but there is so much to be said about this that it 
 will be preferable to dispose of the other accessory details of a 
 total eclipse before embarking on the Corona. 
 
 The first and most obvious proof that the moment of totality 
 has been reached is the general darkness (virtually that of 
 night) which prevails everywhere, darkness usually so great as 
 to necessitate the use of lamps for reading clocks and watches. 
 This intense degree of darkness is not, however, invariably 
 experienced, for under special circumstances which cannot 
 always be foreseen or explained the darkness is very much less 
 intense than the typical darkness just alluded to. The two 
 total eclipses which I have had the good fortune to witness 
 were marked by both these characteristics. During the eclipse 
 of 1900 the darkness was, I apprehend, normal, but in 1905 the 
 darkness may be described as having been rather disappointing. 
 The evident cause was the prevalence of so much cloud all over 
 the sky, and probably that would be the explanation of all cases 
 in which the darkness was not very intense. But incidentally 
 the special circumstances of any particular eclipse would have 
 to be taken into account. The duration and the extent of the 
 apparent overlapping of the Sun by the Moon, whether much 
 or little, would certainly affect the intensity of the resulting 
 obscurity. 
 
 The shadow cast by the Moon on the Earth of course moves 
 progressively along the recognised central line of the eclipse, 
 and its movement can be seen and followed by an observer 
 suitably placed. The words " suitably placed," in this connection, 
 mean that the spectator occupies an elevated position, say on 
 the top, or high up on the side, of a hill, or on the top of a 
 church-tower that is to say, occupies some coign of vantage 
 which enables him to scan a far-distant horizon. Doing this, he 
 will be able to catch sight of the shadow coming up to his own 
 position, hanging over it momentarily, and then rapidly pass- 
 ing off in the opposite direction. The necessity for an observer 
 
124 ECLIPSES. 
 
 being wide awake who is desirous of catching sight of this 
 shadow will be understood by the statement that it travels at 
 the rate of thirty miles in a minute. 
 
 Another very curious and interesting feature of a total 
 eclipse of the Sun is one which has only come into prominence 
 of recent years, namely the " Shadow Bands." They become 
 visible a few minutes before totality, say five. They are wavy 
 streaks of light and shade which dance across the landscape, 
 and are best seen if the observer can so place himself as to face 
 an upright, white-plastered, or stone wall to serve as a screen to 
 receive the shadows as they pass along. Nothing is known of 
 their cause, or of any laws which regulate them. They vary at 
 different eclipses in distance apart, in breadth, and in the speed 
 with which they travel. 
 
 One other thing may be mentioned : the brushes of light which 
 precede the immediate appearance of the Corona on the side of 
 the dark Moon opposite to the disappearing crescent of the Sun. 
 It does not seem that these brushes of light are directly associa- 
 ted either with the Corona or with Baily's Beads, or indeed with 
 any phenomenon already mentioned. They appear, in point of 
 fact, to have an entirely independent existence, and I am not 
 acquainted with any well-considered explanation of their origin. 
 
 The Corona is, after all, the one special feature of every total 
 eclipse of the Sun on which every observer, as a rule, concen- 
 trates his attention, lunless he is officially turned off to some- 
 thing else. Briefly described, the Corona is a broad ring of light 
 seen to surround the Moon at the instant of totality, lasting 
 during totality, and disappearing on the return of the Sun to 
 visibility. It is usual to consider the Corona in a twofold 
 aspect that is to say, we speak of the " inner Corona " and the 
 " outer Corona." The two together constitute a broad bright 
 ring of light of varying diameter, or perhaps it will be best to 
 consider the inner Corona as a ring averaging in breadth, 
 whilst the outer Corona extends i, 2, or more degrees from the 
 Sun, at which distance it generally has ost its more or less 
 
FIG. 147 
 
 PLATE XL! I. 
 
 124] 
 
 The Solar Corona, 1898 (C. Michie Smith], 
 
FIG. 148 
 
 PLATE XLII1. 
 
 [125 
 
THE CORONA. 125 
 
 circular outline, its edges developing into long rays or streamers 
 of varying length, and stretching from various parts of the Sun's 
 circumference. I say " Sun's circumference " because it is now 
 well understood that the Corona belongs to, and is an appendage 
 of the Sun, but looked at merely from the sight-seeing point of 
 view it might equally seem to be a ring around and belonging 
 to the Moon. Indeed, in early days it was considered to be a 
 lunar appendage, and it was only during recent years that it has 
 become certainly established that the Corona, whatever it is, 
 belongs exclusively to the Sun. Its general appearance will be 
 best understood by a careful examination of the accompanying 
 illustrations, which represent its appearance at many different 
 dates, and as portrayed by various observers ; some by resort to 
 hand-drawing, but the majority due to photography. 
 
 By far the most interesting recent discovery connected with 
 the Corona is the fact that its variations in shape depend upon 
 an undoubted law, but the circumstances of that law are not all 
 understood. The law, stated baldly, is that the outline of the 
 Corona varies in a most marked degree according to whether 
 the eclipse coincides (or nearly coincides) in point of time with an 
 epoch of maximum or an epoch of minimum Sun-spots. In the 
 former case the general outline of the Corona is roughly circular 
 and compact, whilst in the latter case it is not only exceedingly 
 irregular, but is characterised by remarkable streamers extend- 
 ing 2 or more on each side of the Sun in prolongation of the 
 solar Equator, accompanied by narrow flames of light at either 
 pole. 
 
 Speaking generally, I think we are entitled to assume that 
 the Corona is something in the nature of an atmosphere sur- 
 rounding the Sun ; but its indescribable texture (so to speak), 
 and the uncertainty and irregularity of its streamers, and its 
 undoubted connection, in some way, with the presence or 
 absence of Spots on the Sun render it one of the great mysteries 
 of modern astronomy, the perfect unravelling of which has yet 
 to be accomplished. 
 
126 ECLIPSES. 
 
 A question is often put by that well-known personage, " the 
 man in the street," in the dual form of " What is the good of an 
 eclipse of the Sun ?" and " What is the good of taking so much 
 trouble and incurring so much expense to observe an eclipse of 
 the Sun ?" Perhaps no very direct answer can be given, and a 
 cynical mind might take pleasure in recalling Sir George 
 Cornwall Lewis's classic denunciation of astronomy, which he 
 stigmatised as a " science of pure curiosity." The remark, 
 though by no means fair or strictly accurate if applied to the 
 science of astronomy as a whole, has some application to the 
 special subject of Eclipses. They are only observed and can 
 only be observed to satisfy human curiosity, which desires to 
 know as much as possible about the occult things of the universe, 
 in this case the physical constitution of the Sun, well described 
 by Proctor in the title of one of his books as the " Ruler, Light, 
 Fire, and Life " of the system. 
 
 The elaborate observations of the last 35 years in par- 
 ticular have thrown a flood of light on the origin of 
 those phenomena which form the accessories of a total 
 eclipse of the Sun, and so indirectly help to reveal the con- 
 stitution of the Sun. Of the special sights which present 
 themselves during a total eclipse, beyond doubt the Corona is 
 the most interesting and most striking. In the early days of 
 exact observations the question was long in controversy whether 
 the Corona was connected with the Moon or the Sun. It is 
 now a matter of perfect certainty, as has been already stated, 
 that the Corona is a solar and not a lunar feature, and that the 
 Moon has only a secondary share in the matter for the reason 
 that its own solid body blocks out the sunlight from observers 
 on the Earth, and so enables them to see the display of light 
 which emanates from the Sun and constitutes the Corona. 
 
 The question of the shape of the Corona, as connected with 
 the prevalence of Sun-spots, is such an important one that it 
 is worth while to recapitulate the facts in a slightly different 
 form; thus : When a total eclipse of the Sun occurs at or 
 
FORTHCOMING ECLIPSES. 127 
 
 near the epoch of the Sun-spot maximum, the Corona takes 
 a distinctly compact shape, with its outline of very much the 
 same breadth all the way round the Sun, whatever streamers or 
 special off-shoots may be visible. On the other hand, when 
 an eclipse occurs at an epoch of Sun-spot minimum, there is 
 a marked deficiency in the breadth of the Corona at the 
 N. and S. poles of the Sun, but in the equatorial regions, 
 both E. and W., the Corona throws out broad, elongated 
 streamers, which on some occasions have been traced to a 
 distance of 4 from the Sun's limbs. The meaning of these 
 differences is at present unknown, but the facts are unquestion- 
 able. It is interesting to note that the eclipse of 1900 was 
 the first that was made the subject of a prediction, that as it 
 coincided with an epoch of few or no Sun-spots, its outline 
 would be elongated in the Sun's equatorial regions ; and this 
 proved to be the case. 
 
 The Corona itself is no new, or even modern, discovery. 
 The record of its existence certainly goes back to 1567, and 
 perhaps even much further than that. What is modern and 
 newly recognised is that the general outline of the Corona 
 varies periodically, with some relation to the spots on the Sun. 
 
 It may interest the reader to hear something about the 
 eclipses which will happen during the next few years. The 
 information which follows is taken chiefly from the Nautical 
 Almanac, and the Rev. S. J. Johnson's Historical and Future 
 Eclipses. 
 
 1913, March 22. Total eclipse of the Moon, invisible at 
 Greenwich, but visible in Polynesia. (Mag. \'$j6.} 
 
 1913, April 6. Partial eclipse of the Sun, invisible at Green- 
 wich, visible in North- West America and North-East Asia. 
 
 1913, September i. Partial eclipse of the Sun, invisible at 
 Greenwich, visible in Labrador. (Mag. O'i5.) 
 
 1913, September 15. Total eclipse of the Moon, invisible in 
 Greenwich, visible in the Indian Ocean. (Mag. 1*43.) 
 
 1913, September it). Partial eclipse of the Sun, invisible at 
 Greenwich, visible in the South Polar regions. (Mag. 0*82.) 
 
128 ECLIPSES. 
 
 1914, February 24. Annular eclipse of the Sun, visible only 
 in the South Polar Regions. 
 
 1914, March 12. Partial eclipse of the Moon, partly visible 
 at Greenwich in the early morning. 
 
 1914, August 21. Total eclipse of the Sun, visible at Green- 
 wich as a partial eclipse (Mag. 0^65 1). The central line passes 
 through Southern Russia, north-westwards through Norway. 
 
 1914, September 4. Partial eclipse of the Moon, invisible at 
 Greenwich, and visible only in Polynesia. 
 
 The foregoing statement of the eclipses of 1913 and 1914 
 embraces all the eclipses of these years, but considerations of 
 space require me now to continue the statement on a principle 
 of selection, and I give, therefore, now only eclipses of the Sun, 
 and only such as are either annular or total, and also visible 
 either in England or within easy reach of England. 
 
 1916, February 3. Total eclipse visible in the Atlantic, just 
 missing the shores of Ireland. 
 
 1921, April 8. Annular eclipse, visible about the Shetland 
 Islands. 
 
 I 9 2 5? January 24. Total eclipse, visible in North America 
 and across the Atlantic to beyond the N. of Scotland. 
 
 1927, June 29. Total eclipse, visible in North Wales, Lan- 
 cashire, North Yorkshire, and Durham, but total for only about 
 20 seconds or a little more. This eclipse is actually the first 
 total eclipse visible at all in England since 1724. 
 
 After 1927, England will have no chance of another total 
 eclipse until August n, 1999, when the shadow-line will cross a 
 part of Cornwall and Devonshire. 1 In point of fact, many 
 centuries will elapse ere another eclipse will occur fulfilling the 
 four following conditions presented by the eclipse of 1905 : 
 such a long duration of darkness ; a locality with so good a 
 promise of a clear sky ; such a high altitude for the Sun above 
 the horizon ; and a locale so accessible from the shores of 
 
 ' This is what is commonly stated, but according to the map in Oppolzer's 
 Canon der Finstcrnisse, the central line does not touch England, but passes 
 a certain number of miles to the S. and so into France. 
 
OBSERVATIONS OF ECLIPSES. 1 29 
 
 England as was Spain. Finally, it may be stated that on 
 October 7, 2135, there will be an eclipse the central line of 
 which will pass over the middle of England. 
 
 Speaking generally, total eclipses of the Sun may be said not 
 to vary very much in number from century to century, but the 
 greater facilities for travel which we can now command, com- 
 pared with the limited opportunities possessed by our ancestors, 
 or even by our grandfathers, make the subject of eclipses 
 much more familiar to us nowadays than was formerly the 
 case ; and the eclipses since the middle of the igth century, 
 observed as they have been in many parts of the world which 
 used to be more or less inaccessible, have yielded the numerous 
 and important disclosures respecting the constitution of the 
 Sun which have been mentioned earlier in this chapter. 
 
 As regards the question of instruments, it is no longer 
 sufficient to be content with simple eye-observations of the 
 visible sights offered by an eclipse to persons armed with 
 only ordinary telescopes. Of course a telescope (which need 
 not be a very large one) is necessary, or, at least, very useful 
 for observing the outward appearances exhibited during the 
 progress of a solar eclipse. Indeed, an opera-glass, or even 
 the naked eye, suffices to disclose many interesting features ; but, 
 to perform eclipse observations of the highest value in the 
 most up-to-date fashion, a good deal more is wanted than a 
 mere telescope. Moreover, the astronomer requires the active 
 assistance of a photographer and of a practical chemist, to say 
 nothing of an outfit of clocks and of time-keepers to manage 
 them. Accordingly, the impedimenta of a fully equipped 
 eclipse expedition are vastly more numerous, more heavy, 
 more bulky, than was the case in by-gone days ; and it is only 
 the modern application of steam 1o railways and ships which 
 enables astronomers of the 2oth century to do the work which 
 the scientific exigencies of the century demand. 
 
 Even with the facilities here referred to, it will easily be 
 understood that it is no joke to organise and carry to a success- 
 
 9 
 
133 ECLIPSES. 
 
 ful issue eclipse expeditions from England to such far-off 
 localities as India, or Polynesia, or the West Indies, though 
 such things have been done several times within recent years. 
 When, however, English astronomers in England had, in 1905, 
 the chance of a total eclipse of the Sun no farther off than 
 Spain, perhaps 700 miles away, it was obvious that there would 
 be a rush to see it, which would not have occurred if it had been 
 a question of a voyage to Java, or Tierra del Fuego. Hence it 
 came about that the eclipse of 1905, already mentioned, had 
 been looked forward to with great interest by vast numbers of 
 English people, astronomers and non-astronomers. These 
 may be said to have had their appetite whetted by the eclipse 
 of May 1900, also visible as near to England as Spain and 
 Portugal. But this eclipse was under the important disability 
 that its duration was very short, only i^ minutes a period too 
 brief wherein to see or do much. On the other hand, the 
 eclipse of 1905 was due to last 3^ minutes, an interval to be 
 deemed substantial, seeing that under no circumstances, as 
 already stated, can the most favourable totality last for more 
 than about 6 or 7 minutes. 1 
 
 Therefore the probabilities were that large numbers would 
 flock to Spain from England (and, for the matter of that, 
 from France and Germany) to see the eclipse of 1905. 
 Accordingly, some account of the preparations which had 
 to be made (indeed which always have to be made before 
 total eclipses) will probably interest the reader. 
 
 Preparations began much further back than a few months 
 before the great event. Though it is rather the fashion to run 
 down Spain and things Spanish, it must be stated, to the credit 
 of the Spanish Government, that more than 4 years in 
 advance did the Madrid Observatory begin taking steps to 
 prepare for the eclipse, first by the issue of a very good map of 
 the path of the central line across Spain, and afterwards by the 
 issue of additional maps and a pamphlet of suggestions and 
 
 1 Whitmell, Monthly Notices, Royal Astronomical Society, vol. Ix. p. 435. 
 
ORGANISATION OF ECLIPSE PARTIES. 13! 
 
 advice. These preliminary documents proved most useful to 
 the English Astronomical Societies and private individuals who 
 undertook to organise the necessary travelling arrangements. 
 
 In all such matters there are certain very important points 
 to be handled, to which all others must be subordinate. First 
 and foremost comes the question of probable weather at possible 
 observing stations situated in or near the central line. Infor- 
 mation as to this had to be sought from existing records already 
 published by Spanish meteorological authorities. These were 
 obtained, consulted, and tabulated with the following general 
 results. 
 
 It was found that there was a probability of fog and haze 
 prevailing at the end of August on the N. coast of 
 Spain, at or near the actual coast-line, though this could be 
 evaded by journeying 50 miles inland by roads or railways 
 to towns without hotel accommodation. Still further inland, 
 especially at and near the important city of Burgos, it 
 was found that eligible positions could be selected for ob- 
 serving the eclipse, all the more eligible because, Burgos 
 being at a considerable elevation above the sea, a fair amount 
 of fresh air at a moderate temperature was understood to be 
 obtainable 
 
 The question of temperature constituted all along a great 
 difficulty in making up eclipse-observing parties, it being well 
 known that the summer temperature of the S.E. of Spain 
 is quite tropical in its character. Next after the question of 
 temperature came the question of sleeping accommodation, 
 beds and bedding to the taste of Mr. and Mrs. John Bull being 
 difficult to obtain, indeed almost non-existent in Spain. 
 
 When the eclipse came within a measurable distance that is 
 to say, about a year and a half before the appointed day the 
 British Astronomical Association nominated a special committee 
 to consider the travelling and observing arrangements which it 
 was expedient to make. The question of travelling was dealt 
 with first. The difficulties which it was known would have to 
 
132 ECLIPSES. 
 
 be faced in respect of the extreme heat and the general lack of* 
 comfortable sleeping accommodation led the Committee, in the 
 first instance, to contemplate the employment of a large ocean- 
 going steamer, which should land parties to settle themselves 
 at different places on the S.E. coast, with Valencia as the 
 permanent headquarters for the steamer, for a week or more, 
 making use of the steamer, as much as possible, as a floating 
 hotel. 
 
 Several steamship companies applied to one and all refused 
 to negotiate with the Committee except on terms and conditions 
 which were so excessive as to be prohibitive. The con- 
 templated grand expedition in its complete form had then to 
 be abandoned, and the 70 or more scientific excursionists 
 who had given in their names to go somewhere or other were 
 left to make arrangements for themselves as best they could. 
 
 The redoubtable Cook then came upon the scene, and offered 
 personally to conduct parties overland through France to 
 Burgos, and, partly by land and partly by sea, to the Balearic 
 Islands via Marseilles. 
 
 The Polytechnic Institution offered to organise another party 
 from London to Burgos at a helter-skelter pace and cheap 
 fares. Their number (20) was soon made up. Besides the 
 foregoing there were attempts made, with more or less (gener- 
 ally less) success, to get up detachments for Gijon, on the 
 N. coast of Spain, for Valencia on the S.E. coast, and for 
 Philippeville in Algiers. 
 
 The merits of these various subsidiary observing centres 
 generally turned on the facilities available for local travelling 
 from the chief centre and on the question of hotels ; for, happily 
 so far as the Mediterranean portion of the eclipse area was 
 concerned, there was never any serious doubt or risk about fine 
 weather and a clear sky being assured. 
 
 Observations of eclipses of the Sun differ from all other 
 astronomical observations in a very important particular. 
 Most observations are performed by one chief observer with or 
 
ORGANISATION OF ECLIPSE PARTIES. 133 
 
 without some assistance from a subordinate, who will perform 
 such minor duties as calling out or writing down times as 
 indicated by a clock, or opening or shutting photographic 
 shutters and slides. An ordinary observer, with or without a 
 little help from a junior, can, as a rule, take his own time in 
 performing the task which he has undertaken, or which has 
 been allotted to him. Things are quite otherwise, however, 
 when a total eclipse of the Sun is in question. There is then 
 no opportunity for leisurely work. A dozen different things 
 have to be performed, or looked at, practically all at once at 
 any rate, within the compass of a few minutes, which seldom 
 exceed three or four at the outside. 
 
 A well-disciplined eclipse observer has, therefore, to make 
 up his mind, not only that he cannot see everything himself, 
 but that he can hardly hope to see even one-tenth of every- 
 thing. The work, therefore, calls for much self-denial on the 
 part of the earnest votary of science, who must patiently 
 resolve to concentrate his mind on some one or two special 
 points, whilst his next-door neighbour on one side concentrates 
 his thoughts on a third or fourth special point, and another 
 neighbour gives his mind perhaps to a fifth, or sixth, special 
 point ; and so all the expected phenomena are, by judicious 
 pre-arrangement, shared out amongst the different members of 
 a party or expedition. 
 
 Before every eclipse it is usual for the members of a party, 
 especially if they belong to some public or State Observatory, to 
 go through a sort of military rifle and aiming drill, to practise 
 what they will have to perform during the critical brief minutes 
 of totality, and to make sure beforehand that each understands 
 his own duty and his own instrument, etc., and will not 
 trespass upon the duties of his coadjutors, or have a fiasco 
 with his own instruments or apparatus. Prior to the eclipse of 
 1900 the Astronomer Royal's party at Greenwich had a grand 
 rehearsal, which was afterwards repeated with models of a 
 sham eclipse, much to the amusement of the spectators, at 
 
134 ECLIPSES. 
 
 a meeting of the Royal Astronomical Society at Burlington 
 House. 
 
 Inspired by this precedent, one day in July 1905, the Eclipse 
 Committee of the British Astronomical Association gathered 
 together a number of those who intended to observe the eclipse, 
 and carried out a very useful, though informal, exchange of 
 ideas as to what observations were possible with the instrumental 
 appliances at the command of each with a view of avoiding to 
 some degree, by pre-arrangement, waste of time and waste of 
 labour on the great day. And some of those who were posted 
 up in the intricacies of French and Spanish railway travelling, 
 and Spanish hotel life, unfolded their experiences for the benefit 
 of novices present. 
 
 As regards the work which was to be performed that is, the 
 observations which were to be made the Eclipse Committee 
 just named entrusted the preparation of an "agenda" to 
 Mr. E. W. Maunder, of the Royal Observatory, Greenwich, and 
 it is needless to add that the work was well and judiciously 
 done. It had scarcely been accomplished when Mr. Maunder 
 had to resign his secretaryship of the Eclipse Committee because 
 the Canadian Government had honoured him with an invitation 
 to join their observing party, which was going to the far-off 
 locality of Labrador, and which, therefore, rendered it necessary 
 for him to leave England some weeks before the Spanish parties 
 did so. 
 
 At well-nigh the eleventh hour, when all other attempts to 
 negotiate an expedition, wholly or almost wholly, by sea, had 
 failed, it was discovered that the P. & O. Mail steamer leaving 
 Tilbury on August 25 was due to cross the line of central 
 eclipse, or totality as it is generally called, on the very day, 
 and almost at the very hour, of the eclipse, and negotiations 
 were entered into with the Company with a view of arranging 
 that the ship should heave-to for two or three hours to enable 
 the passengers ta have a leisurely view of the phenomenon. So 
 soon as this decision was arrived at it was communicated to all 
 
PREPARATIONS FOR THE ECLIPSE CF 1905. 135 
 
 the members of the British Astronomical Association, and 
 others who had desired to see the eclipse without incurring 
 the many disagreeables of a land journey across France and 
 Spain during the hot days of August. Thanks to the officials of 
 the P. & O. Company, the details were soon worked out. 
 
 This review of the situation will enable the reader to under- 
 stand something of the nature of the preliminary matters which 
 had to be handled ; but my statement of them is very far from 
 being exhaustive, for I have limited myself to matters affecting 
 those who were going abroad from England. 
 
 I have said nothing about what the Americans proposed to 
 do, and the Americans always carry out their scientific expedi- 
 tions in good style, and with thoroughness ; nor have I said 
 anything about French or German efforts. France has an 
 Astronomical Association, run very much on the same lines as 
 the English Association, and it was at one time hoped that 
 some sort of organised co-operation might have been arrived at 
 between the two bodies ; but this did not come about, chiefly 
 because the travelling necessities of the two nations were 
 diverse, the English having to cross the water to get to Spain, 
 whilst the French were already next door. 
 
 Since the eventful month of December in the eventful year 
 1870, when the distinguished French astronomer, Janssen, 
 escaped from beleaguered Paris in a balloon in order to observe 
 the total eclipse of the Sun of December 22, 1870, there have 
 been many expeditions to all parts of the world to observe 
 occurrences of the same phenomenon. So far as I can re- 
 member, there has never been an instance, till the year 1905, 
 of an expedition of astronomers and astronomically-minded 
 people having been avowedly organised to observe an eclipse 
 at a " station " on the high seas. 
 
 The nearest approach to this would seem to have been the 
 stoppage for an hour or two in mid-Atlantic, on May 29, 1900, 
 of the ss. Austral, of the Orient Line, on its outward voyage to 
 Australia in order that its passengers might view the total 
 
136 ECLIPSES. 
 
 phase of that day. There was, however, no set purpose on 
 the part of the steamship company to provide this special show 
 for the benefit of the passengers. The episode was contrived 
 by Colonel Markwick, R.A., F.R.A.S., who had obtained an 
 assurance that the steamer would cross the eclipse line at the 
 right place and time. The eclipse of April 17, 1912, was by an 
 arrangement with the captain viewed by Mr. W. B. Gibbs, 
 F.R.A.S., on board the Union Castle s.s. Balmoral Castle off 
 the coast of Portugal. 
 
 Nor do I think there was any set purpose in the mind of 
 the captain of the French man-of-war Le Comte tfArtois, 
 who, in the middle of the i8th century, observed at sea the 
 eclipse of February 9, 1766. Possibly, however, it was by 
 design that the Spanish Admiral, Don Antonio Ulloa, saw the 
 total eclipse of June 24, 1778, at sea, when passing from the 
 Azores to Cape St. Vincent. His observations, published in 
 the Philosophical Transactions, 1779, considering their early 
 date, are extremely interesting. 
 
 The land observations in 1905 call for no special notice in 
 this place as regards the personal adventures of the observers 
 who chose terra firma in Spain for their work, but the fortunes 
 of the sea-going party, of whom I was one, are worth a brief 
 mention because of their novelty. This section of observers 
 took ship at Tilbury on board the P. & O. steamer Arcadia, 
 Captain Cubitt. After an uneventful voyage, only varied by 
 landing for a few hours at Gibraltar, we arrived in the forenoon 
 of the eventful day, August 30, at the exact spot in the 
 Mediterranean, not far from the Balearic Isles, in the precise 
 latitude and longitude which it was calculated would put us on 
 the central line of the eclipse ; and so it did, and we saw 
 everything most successfully, thanks to Captain Cubitt's kind 
 and painstaking co-operation. 
 
 Before the eclipse we knew that there was one special 
 problem to be solved which dominated all others : could we 
 fjnd the proper position, and, having found it, CQuld we keep it 
 
FIGS. 149-151 
 
 PLATE XLIV. 
 
 No. i. ii h. 46 m. scfs. G.M.T. 
 
 No. 3. 12 h. ii m. 
 
 The Eclipse of the Sun, April 17, 1912, as seen at Bournemouth. 
 
 (E. W. Barlow, photo.} 
 
 [(Notice that 2 and 3 represent crescents of the Sun of the same form, 
 but a different part of the Sun is exposed to view.) 
 
 136] 
 
FIGS. 152-153 
 
 PLATE XLV. 
 
 snd stage. 
 
 Total Eclipse of the Moon, Jan. 28, 1888. 
 
FIGS. 154-155 
 
 PLATE XLVI. 
 
 1366] 
 
 4th stage. 
 
 Total Eclipse of the Moon, Jan. 28, 1888. 
 
PLATE XLVII. 
 
 5th stage. 
 
 Total Eclipse of the Moon, Jan. 28, 1888. 
 FIGS. 157-160 
 
 Oceultation of Jupiter by the Moon, Aug. 12, 1892 (W. H. Pickering}. 
 
 [137 
 
SKETCHING THE CORONA. 
 
 137 
 
 for two hours, and especially for the 10 minutes which would 
 include the critical events of the eclipse ; and would the ship 
 be steady enough on the water to enable the necessary observa- 
 tions to be made ? Everything happened just as was wanted, 
 
 Fig. 161. The Corona, Aug. 8, 1896, as sketched by 
 E. J. Stone's system. 
 
 the most remarkable thing of all being the steadiness and the 
 fixity of the ship. This last was accomplished by the ship 
 being kept moving at the calculated speed of three knots an 
 hour, which neutralised the strong set of the current in the 
 reverse direction. All of us, or most of us, were able to 
 
138 ECLIPSES. 
 
 observe the usual concomitants of total eclipses of the Sun ; but 
 the only feature needing notice here was the lack of darkness 
 of the usual intensity, or anything like it. Probably that was 
 the result of our viewing the eclipse with nothing but water 
 surrounding our place of observation. 
 
 Fig. 161 represents a diagram devised by E. J. Stone for 
 noting down in haste the streamers, etc., visible in a total 
 Eclipse of the Sun. The diagram is an instance of its actual 
 use by Stone on the occasion of the Total Eclipse of the Sun 
 of August 9, 1896. The diagram, however, may be usefully 
 employed for other purposes if copies of it, printed on cards, 
 are kept for use with a telescope. In the case of occultations 
 of stars by the Moon the points on the lunar limb, where the 
 stars will disappear and reappear, may be marked before- 
 hand ; and so time may be saved, and the stages of the 
 phenomenon not lost because the observer is not sure where 
 to look for the stars. Other uses for such cards will present 
 themselves to an observer from time to time ; for instance, 
 in observing the Sun or double stars they will come in very 
 handy. 
 
 We will now consider the eclipses of the Moon in some 
 further detail. It may be said, generally, that whilst, for 
 reasons mentioned in an earlier part of this chapter, these 
 eclipses are more often visible to those who choose to look for 
 them than eclipses of the Sun, yet they kindle much less 
 enthusiasm than eclipses of the Sun, partly for the reason, no 
 doubt, that they are devoid of sensational features of display 
 and points of general interest. Indeed, almost the only matter 
 which an intending observer of a total eclipse of the Moon has 
 to put down on his agenda is the question, What will be the 
 aspect of the Moon when most deeply immersed in the Earth's 
 shadow? will it be visible at all? or will it be invisible? or, if 
 visible, how will it look ? Of course one may say that, by rights, 
 it ought to be altogether invisible, and so very frequently it is ; 
 
PLATE XLVIII 
 
 TOTAL ECLIPSE OF THK MOON. 
 
 1867. 
 
 (Tempel) 
 
ECLIPSES OF THE MOON. 139 
 
 but, on the other hand, it is frequently visible between the 
 extremes of showing traces of its existence, and showing its 
 whole disc quite prominently of a more or less bright coppery 
 colour. There are no discoverable laws which regulate these, 
 variations, and it can only be said, very vaguely, that they 
 depend upon the variable condition of the Earth's atmosphere. 
 If the portion of the atmosphere through which it so happens 
 that the Sun's rays have to pass are highly saturated with aqueous 
 vapour, the red rays will be transmitted freely, and the Moon's 
 surface will be highly illuminated. If, on the other hand, 
 aqueous vapour is deficient, the red rays will be more or less 
 absorbed, and, as the blue will predominate, the illumination 
 will be extinguished. 
 
 When, on the occasion of a total eclipse, some parts of the 
 Moon's disc are visible and others invisible, the variation 
 may be considered due to the prevalence of moisture in some 
 parts of the atmosphere through which the Moon's rays reach 
 us, and its absence in other parts, thus emphasising the dis- 
 tinctions just pointed out. It is right to add that, by various 
 competent authorities, the foregoing explanations are deemed 
 unsatisfactory ; but nothing better has as yet been offered in 
 substitution. 
 
 There have been total eclipses of the Moon recorded which 
 have played a part in certain mundane events. An experience 
 which befel Christopher Columbus is a case in point. In 
 February 1504 Columbus found himself at the island of 
 Jamaica in great straits for want of provisions, which the 
 islanders refused to provide, and he was therefore at his wits' 
 end to know what to do. What followed shall now be told in 
 the words of his son : 
 
 " He bethought himself that, within three days, there would 
 be an eclipse of the Moon in the first part of the night ; and 
 then sends an Indian of Hispaniola with us to call the principal 
 Indians of that province, saying he would talk with them about 
 a matter of concern. Being come that day before the eclipse was, 
 
140 ECLIPSES. 
 
 he ordered the interpreter to tell them that we were Christians 
 and believed in God, who dwelt in heaven and took care of the 
 good and punished the wicked . . . that, as for the Indians, 
 seeing how negligent they were in bringing provisions for our 
 commodities, He was angry with them, and had decreed to 
 punish them with plague and famine ; which because, perhaps, 
 they would not believe, God had appointed to give them a 
 manifest token of it in the heaven, that they might plainly 
 know the punishment was to come from Him. Therefore, he 
 bid them observe that night when the Moon appeared, and 
 they should see her rise angry and of a bloody hue, to denote 
 the mischief God intended should fall on them. Having said 
 this to them, the Indians went away, some afraid and others 
 looking upon it as an idle story ; but the eclipse, beginning as 
 the Moon was rising, and increasing the higher she was, the 
 Indians took notice of it, and were so frightened that they came 
 running from all parts loaded with provisions, crying and 
 lamenting, and prayed the admiral by all means to intercede 
 with God for them, that He might not make them feel the 
 effects of His wrath, and promising for the future carefully to 
 bring him all he wanted. The admiral said he would speak 
 with God, and shut himself up while the eclipse lasted, they 
 still crying out to him to assist them ; and when the admiral 
 saw the eclipse began to go off, and the Moon would soon 
 shine, he came out of his cabin, saying he had prayed to his 
 God for them, and promised Him in their names they would be 
 good for the future, and use the Christians well, bringing them 
 provisions and other necessaries ; and that therefore God 
 forgave them, and as a token of it they should see the angriness 
 and bloody colour of the Moon would go off. This proving so, 
 just as he spoke it, they gave the admiral many thanks, and 
 praised God, continuing so till the eclipse was quite passed. 
 From that time forward they always took care to provide all 
 that was necessary, ever praising the God of the Christians ; 
 for they believed the eclipses they had seen at other times had 
 denoted mischiefs to befall them ; and, being ignorant of the 
 cause of them, and that they happened at certain times, not 
 believing it possible to know on earth what was to happen in 
 the heavens, they certainly concluded the God of the Christians 
 had revealed it to the admiral." l 
 
 1 See Pinkerton, Voyages, vol. xii. p. 148. 
 
EXTERNAL 
 CONTACT 
 
 11 
 
 INTERNAL 
 CONTACT 
 
 in 
 
 
 Fig. 163. Phases of the Transit of an Inferior Planet. 
 
 141 
 
142 ECLIPSES. 
 
 This story records alike the credulity of the natives and the 
 mingled piety and astuteness of the great navigator. It might 
 well be regarded as an example of that worst of all frauds, a 
 " pious fraud." 
 
 The most recent instance of the utilisation of a total eclipse 
 of the Moon occurred on December 16, 1899. What happened 
 is thus described by the Times correspondent with Lord 
 Methuen's army at the Modder River in South Africa : 
 
 "The Full Moon has prevented satisfactory search-light 
 communication lately, but Kimberley took advantage eagerly 
 of the eclipse last night to get important despatches through." 
 
 Akin to eclipses of the Sun are two astronomical phenomena 
 which go by the names of " Transits " and " Occultations." 
 They are entirely identical in principle with solar eclipses, but 
 involve other celestial bodies. 
 
 In a previous chapter it has been pointed out that the two 
 Inferior Planets, Mercury and Venus, are constantly passing 
 round the Sun, and between the Earth and the Sun ; and that 
 when the Earth, Planet, and Sun are in an exact straight line 
 the planet, whichever it be, will be seen projected on the 
 Sun's disc. On such occasions (which are not very often 
 in the case of Mercury and very rare in the case of Venus) 
 the planet presents the appearance of a sharply defined round 
 black spot. The occurrence of such a transit offers an 
 opportunity for determining the distance of the Earth from 
 the Sun. Mercury is not so suitable for this purpose as 
 Venus, because of its proximity to the Sun; but Venus 
 has frequently been used for obtaining a solution of this 
 problem. The actual modus operandi is somewhat complex 
 and beyond the scope of this volume. Suffice it, then, to say 
 that it depends for its success on the skill and care with which 
 observers at remote distances from one another on the Earth 
 
OCCULTATIONS. 143 
 
 can determine micrometrically the exact points on the Sun, as 
 viewed from northern and southern stations on the Earth, at 
 which the planet appears to enter and to quit the Sun's disc in 
 the course of its passage across the Sun. By the application of 
 trigonometry (or mathematics applied to angles) the distance 
 desired to be known can be calculated. 
 
 The satellites of Jupiter also perform transits over their 
 primary's disc the observation of which, though of no important 
 scientific value, furnish interesting spectacles from a star-gazing 
 standpoint. They also suffer eclipse by passing behind the 
 planet. Both these Jovian phenomena are dealt with in the 
 various almanacs which embrace scientific events. 
 
 An Occultation, in the literal meaning of the word, is the 
 covering over of one celestial body by another. Accordingly, 
 in a dictionary ^ense, when a total eclipse of the Sun takes place 
 the Sun is occulted by the Moon ; but the word " Occultation " is 
 by usage confined to cases where the Moon hides a planet or 
 a star, or one planet hides another planet or a star. Occulta- 
 tions by the Moon of stars which lie in its path across the 
 heavens are common enough and occur daily. Sometimes the 
 Moon occults a planet, which naturally intensifies the interest 
 attaching to the event. In the case of the larger planets and 
 stars brighter than the 6th mag. anticipations of the occurrence 
 will be found stated in the Nautical Almanac whence the 
 information is copied into Whitaker's Almanac and other 
 almanacs. When an Occultation occurs between the time of 
 New Moon and First Quarter the effect is very striking, because 
 the star occulted is suddenly extinguished at a point where the 
 sky appears uniformly dark, and where there seems no sufficient 
 reason for anything to interfere suddenly with the star. Occul- 
 tations may be said to be celestial phenomena specially within 
 the reach of amateurs because, when they take place with the 
 Moon young in age, they happen at conveniently early hours in 
 the evening, and are within the reach of telescopes however 
 small. 
 
CHAPTER IX. 
 COMETS. 
 
 Always objects of popular interest. Very numerous. Telescopic comets. 
 Great comets visible to the naked eye. Changes in the appearance 
 of a comet after its first discovery. Often easily mistaken for a 
 nebula. Usual changes exhibited by a telescopic comet. Become 
 visible as they approach the Sun. What is a comet's tail ? Where 
 does it come from ? Why do some comets have tails and not others ? 
 These questions difficult to answer. Sir J . HerscheVs opinion. 
 General account of tails. Some tails probably cylindrical. Bre- 
 dichen's Types of tails. The "Light-pressure" theory. Orbits of 
 comets. Periodical comets. Celebrated comets. Some statistics. 
 
 IT may safely be said that the remarkable objects to be dealt 
 with in the present chapter have had a good deal to do with the 
 recent spread of a taste for astronomy, assisted by the increased 
 space devoted to scientific subjects by the ordinary newspaper 
 press, and by the liberal subventions granted in the United 
 States, especially during the last 30 years, by wealthy men 
 there for the establishment and endowment of astronomical 
 observatories. 
 
 I name the period of 30 years because that takes us back to 
 the "great comet of 1882," which attracted world-wide atten- 
 tion, much more I think than did the "great comets" of 1858 
 and 1 86 1, which were in all respects finer objects than the 
 comet of 1882. All these will require notice further on. For 
 the present I must start with some much less attractive details, 
 the true understanding of which is essential if we would get a 
 clear and satisfactory grip of this branch of astronomy. 
 
CLASSIFICATION of COMETS, 145 
 
 Comets may be said generally to range themselves in two 
 classes : very small ones, seldom if ever visible to the naked 
 eye, and large ones easily visible to the naked eye, and always 
 exhibiting tails the length of which may vary between two or 
 three diameters of the Moon and half the extent of the visible 
 sky. The last-named sort of comet appears only at long inter- 
 vals of time, but a naked-eye comet with a tail two or three 
 
 Nov. it. Nov. 15. 
 
 Figs. 164-165. Brooks's Comet of 1898. (X.) 
 
 degrees long may be said to present itself every two or three or 
 half a dozen years. 
 
 Here we have to face, at the outset, a popular view of things 
 which altogether fails to accommodate itself to the superior 
 knowledge of the professed astronomer. Ask the first person 
 you meet the question, "What is a Comet?" and the answer 
 will always be something like this : " A celestial object which 
 10 
 
146 COMETS. 
 
 appears unexpectedly and has a tail." Such an explanation and 
 such a limited definition totally fail to represent the facts of the 
 case as brought home to the astronomer working with a duly 
 equipped telescope. He would tell us that, in the course of two 
 or three years, he had seen probably at least half a dozen 
 comets, none of them visible to the naked eye, and none of 
 them possessed of a tail. In point of fact, it may be stated 
 broadly that, in the course of a generation, dozens of comets 
 come within our reach, most of them very diminutive in size 
 and rarely having tails. Such comets are designated in 
 astronomical parlance as " telescopic comets," though it occa- 
 sionally happens that here and there one, some weeks or months 
 after its first discovery, draws nearer to the Earth, increases 
 greatly in size, puts forth a tail, and becomes to the man in the 
 street alone worthy of the title of "comet." 
 
 Donati's Comet of 1858, universally known as the "great 
 comet " of that year, was the one within my own personal 
 recollection which in the most striking manner best illustrates 
 what I have just said. Discovered by Donati at Florence on 
 June 2, 1858, I first saw it in a 7^-inch refractor in August of 
 that year. On one evening in the first week in September I 
 could just manage to see it in a portable 3-inch telescope. It 
 then gradually increased in size, and on October 5 had become 
 one of the largest and most magnificent comets on record, not 
 quite so much from the length of its tail (though that extended 
 to about 50) as from the wide, fan-like expanse of the tail, and 
 its great brightness. 
 
 I have cited Donati's Comet as illustrative, albeit in an 
 extreme degree, of the changes which telescopic comets often 
 undergo, but the ordinary comet of this class occupies a much , 
 more humble position in the ken of the astronomer. 
 
 Whether such an object is found as the result of systematic 
 search for comets or is picked up by chance in moving a 
 telescope about in the sky, it will usually, when first glimpsed, 
 present the appearance of a little tiny, cloudy patch which may 
 
COMET HUNTING. 
 
 M7 
 
 or may not have a sharp, star-like centre. Even when found 
 
 and presenting such an aspect, the fact of its being truly a comet 
 
 cannot at first sight be known for a certainty, for there are 
 
 many nebulae and small clusters of small stars which can be at 
 
 first sight, and indeed often have been, regarded as comets, and 
 
 been publicly announced as such. The discreet astronomer 
 
 who is jealous of his reputation does not rush at once to the 
 
 nearest telegraph office 
 
 or newspaper office and 
 
 announce his discovery 
 
 of a comet. He watches 
 
 for a few hours to see 
 
 whether the object 
 
 which he is scrutinising 
 
 is stationary or in 
 
 motion with respect to 
 
 the neighbouring stars. 
 
 It generally happens 
 
 that three or four hours 
 
 will enable him to 
 
 answer this question 
 
 one way or the other, 
 
 but it frequently occurs 
 
 that the sudden arrival 
 
 of clouds shuts out the 
 
 object under scrutiny 
 
 too soon after its dis- 
 
 Fig. 168. Diagram to illustrate the 
 Recognition of a Comet as distin- 
 guished from a Nebula. 
 
 covery for its motion, if any, to be ascertained, and the 
 observer who thinks and hopes he has found a new comet 
 has to wait till the following night before he can safely 
 announce his success. 
 
 What I may call an ordinary telescopic comet usually passes 
 through the following stages of developement : when first found 
 it is a mere luminous patch, in or near the centre of which a 
 slight concentration of light either is seen at the very first, or 
 
148 COMETS. 
 
 after an interval developes. This, when it acquires something 
 like a distinct central brightness, becomes known as the 
 "nucleus." The general size of the comet and its brilliancy 
 increase, supposing that the comet is approaching both the 
 Earth and the Sun : the hazy, nebulous matter around the 
 nucleus becomes broader and brighter, and is then spoken of 
 as the " coma." That may be the end of the developement, but 
 very likely the coma will go on expanding in one direction, 
 and, after giving the whole object an elongated or oval 
 appearance, the elongation will still go on and become 
 eventually a real tail. These transformations occur during 
 the gradual approach of the comet to the Sun, which will 
 generally be the same as saying its gradual approach to the 
 Earth. Here comes in the question, What will be the time of 
 day, or rather of night, when the comet will be visible ? This 
 depends on circumstances which vary in the case of each 
 successive comet. 
 
 Bearing in mind that, so far as we on the Earth are concerned, 
 comets only as a rule become visible when approaching the 
 Sun, it may be stated as something like a general rule that, 
 when a comet is discovered in the evening twilight, it will 
 gradually become more and more immersed in the twilight 
 until it is lost in the rays of the setting Sun. After an interval 
 of a few days, or two or three or more weeks, it will reappear on 
 the other side of the Sun in the morning twilight, and gradually 
 recede from the Sun until it becomes lost either in broad day- 
 light, or, if its path takes it amongst the stars with a dark back- 
 ground, it will be lost to view owing to its continuous diminution 
 of apparent size due to its increasing distance from the Sun and 
 the Earth alike. 
 
 The foregoing account of what may be called the rise and 
 fall of a comet, so far as its career from a terrestrial point 
 of view is concerned, will suffice to convey a general notion 
 of what happens to these bodies ; but, of course, particular 
 comets, by reason of their notorious vagaries in the heavens, 
 
TELESCOPIC COMETS. 149 
 
 may come and go without conforming to the stages of history 
 set forth above. For instance, it often happens that a comet 
 is seen for the first time when its visible career, so far as we 
 are concerned, is coming to an end by reason of the fact that 
 its nearest approach to the Earth and to the Sun happened 
 some weeks previously, when no one saw it, and that when it 
 was first seen it was well on its way on its return journey to 
 the unknown realms from which it came. 
 
 Fig. 167. Telescopic Comet Fig. 163. Telescopic Comet 
 without a Nucleus. with a Nucleus. 
 
 The subject of cometary astronomy is such a very large one 
 that it is not easy to know where to draw the line as regards 
 going into details. The changes which the small telescopic 
 comets usually undergo require, for their proper study, tele- 
 scopes of considerable power, and it is doubtful whether these 
 changes appeal to the general reader or popular student. It is 
 far otherwise, however, with the tails of comets. The recorded 
 varieties of tail and the changes which have been noted in 
 the tails of particular comets open up a large field both for 
 
150 COMETS. 
 
 descriptive writing and for speculation. It must suffice, how- 
 ever, here to state a few general outlines. 
 
 Three questions frequently asked are : " What is a comet's 
 tail made of?" "Where does it come from?" and "Why do 
 some comets have tails and not others ?" 
 
 It must be confessed that no very satisfactory answers can 
 be given to any one of these three questions. 
 
 The first, especially, is an inscrutable one, and a remark made 
 by the late Sir John Herschel, some three-fourths of a century 
 ago, may be cited as an indirect indication of the uncertainties 
 which confront us. He said, in a famous passage, that the 
 tails of comets probably, as a rule, only weigh a few ounces ! 
 This statement may sound, and perhaps is, fanciful ; but it is 
 hard to disprove it, and it is equally difficult to prove it, and a 
 contented confession of agnosticism is perhaps the safest 
 attitude to assume. 
 
 The second question, " Where does the tail of a comet come 
 from ?" is a little more easy to deal with, because we have some 
 evidence of our eyes, which counts for something in this con- 
 nection. Whilst in a certain number of cases it may be said, 
 with Topsy, that the tails simply " grow " by visible expansion 
 from the comet, yet there are not a few well-established cases 
 in which a tail has been seen to emanate from the bright 
 central head of a comet precisely as a jet of water may be seen 
 to be thrown up from the mouth of a fountain. The third comet 
 of 1862, as sketched by Professor Challis, of Cambridge, was a 
 remarkable instance of what may be called the jet origin of 
 a comet's tail ; but there are many other instances on record. 
 The natural idea which the observation of a comet developing 
 a tail from its nucleus suggests is that the nucleus is a source 
 of radiant, luminous matter which is thrown up in the fashion of 
 an Iceland geyser. This is how the matter may be said to 
 come home to the eye of a spectator ; but the difficulty is to 
 realise how such a vast mass of luminous matter can be pro- 
 duced in or from the head of a comet, bearing in mind the 
 
FIGS. 169-170 
 
 PLATE XLIX. 
 
 "8 
 
 3 
 1 S 
 
 150] 
 
FIG. 171 
 
 PLATE L. 
 
 Encke's Comet, Sept. 22, 1848. 
 
 (As seen at the Hartwell Observatory.) 
 
THE TAILS OF COMETS. 151 
 
 evidence we possess of the ethereal character of these bodies, 
 and their lack of solid substance and weight. On this question 
 of lack of mass it will be necessary, and more convenient, to 
 say something later on. 
 
 The question as to why some comets have tails and not 
 others is another of those points connected with cometary 
 astronomy which is inscrutable. Speaking generally, it may be 
 said that very small comets have no tails, and that very large 
 comets always have tails. This, however, brings us no nearer 
 to a solution of the question. At any rate, it may certainly 
 be affirmed that very small comets which are no brighter than 
 the stars of the loth magnitude or smaller (and there are such), 
 never have tails, whilst, on the other hand, such a thing as a 
 large and compact comet visible to the naked eye and without 
 a tail is unknown. It is true that one or two comets are on 
 record as tailless, and as large in size as a Full Moon, but our 
 knowledge of them depends upon ancient writers whose 
 habitual looseness of language and lack of precision seriously 
 discount their testimony. 
 
 It will now be desirable to describe in some detail certain of 
 the features which have been recorded in the case of comets 
 seen in the past. In the first place, when a comet has a tail, 
 the tail is nearly always turned more or less directly away from 
 the Sun ; that is to say, it has shot forth in a direction behind 
 the comet rather than in front of it or towards the Sun. This 
 is no more than the common case of the tail of anything, 
 whether it be the train of a queen or the tail of a cow. 
 There are a few instances on record of comets having had 
 not only a normal tail, properly so called, but a short stubby 
 tail on the side of the Sun and pointing towards the Sun. 
 Such a tail is usually spoken of by old writers as a "beard," 
 and the sense of the expression will be obvious from what 
 has just been said as regards tails generally. This fact of 
 tails of comets being usually turned away from the Sun was 
 noted by an observant foreigner named Apian in 1531 ; but 
 
152 COMETS. 
 
 the Chinese seem to have noticed the same fact 700 years 
 previously. 
 
 When a comet has a tail, in the majority of cases there is 
 only one such appendage, but two tails are not uncommon, and 
 there have been cases of three, four, and five tails, whilst the 
 celebrated comet of 1744 had six well-defined separate tails. 
 It is important to note that it sometimes happens that, though a 
 comet can only be fairly described as having one tail, yet now 
 and again there may be noticed long, thin, streaks of cometary 
 matter emanating from the same centre as the main tail, and 
 these streaks ought rightly to be numbered as distinct tails. 
 This attribute of subsidiary streamers in the nature of tails 
 was not in the past very much dwelt upon by observers 
 describing comets which they had studied ; but the application 
 of photography to cometary observations has in recent years in 
 several cases brought very distinctly under our notice what 
 must really be spoken of as a multiplicity of tails. Photo- 
 graphy grasps undoubtedly a wider range of details than does 
 human vision at the eye-end of a telescope. 
 
 Under ordinary circumstances, while a common type of 
 comet has a common type of simple tail, there is nothing in 
 general to catch the eye and lead one to any precise conception 
 of the actual form of the tail ; but in what may be called 
 more perfectly developed tails, one sees the two edges dis- 
 tinctly brighter than the centre, and this compels the conclusion 
 that the real form of such a tail is cylindrical, or, in many cases, 
 conical. That a tail is of this formation is obviously suggested 
 by the fact that, if we look at any luminous cylinder sideways, 
 even if really illuminated evenly all round, it will in projection 
 look brighter at its apparent edges, because the eye will be 
 viewing the edges through a concentrated thickness of material, 
 whereas the portion of the cylinder midway between the 
 illuminated edges will only be of a single thickness, so to 
 speak. This may be tested in several obvious ways in 
 connection with domestic illumination in our houses, and 
 
CLASSIFICATION OF TAILS. 
 
 153 
 
 assuredly gives us a clue to the true form of many cometary 
 tails. 
 
 Where a comet has evidently two distinct tails (not the 
 appearance of two tails in virtue of the explanation just given) 
 it almost always happens that the two tails are of different 
 length, and that the shorter one is inferior in brilliancy to the 
 longer one. 
 
 Except in the case of small comets with short tails, it is 
 seldom that a tail is straight ; it is most usual for the tail to 
 
 Fig. 172. Medal distributed by the Monks to avert Misfortune 
 during the Appearance of the Great Comet of 1680. 
 
 be curved, and the curvature is the natural result of the comet's 
 head moving forwards, and the tail not being able to keep 
 pace with it because of its more flimsy material. This, at least, 
 seems a fair and proper way of describing the condition of 
 things. 
 
 Two astronomers of the present day, working on different 
 lines, have endeavoured to classify the tails of comets on the 
 supposition that there is an individuality about tails, which 
 shows that they are not all formed in the same way or under 
 similar conditions. The most svstematic of these classifications 
 
154 COMETS. 
 
 is due to the Russian astronomer Bredichin, who has worked 
 at the matter with great zeal and moderation and discretion 
 of language and conclusions. I lay stress on this description 
 of his labours because there has been of late years a great 
 disposition on the part of astronomers of a certain sort to put 
 forth wild speculations respecting the formation and condition 
 of the tails of comets, with a very limited amount of proof 
 available to support their views. Bredichin's investigations 
 led him to divide the tails of comets into three classes: (i) 
 long, straight tails ; (2) curved, plume-like tails ; (3) short, 
 stubby, and sharply curved brushes of light. 
 
 Bredichin's First Type of tails he considers formed of matter 
 upon which the Sun exercises a repulsive action very much 
 greater than the Sun's attractive action in virtue of the general 
 principles of Gravitation, so that the particles of cometary 
 matter quit their point of origin in the head of the comet with 
 a relative velocity which rapidly increases, and eventually 
 becomes enormous. The long, straight streamers, which I 
 have already alluded to, were well exemplified in Bond's draw- 
 ings of Donati's comet of 1858, and tails of this type are 
 composed, according to Bredichin, of hydrogen gas. The 
 Second Type of tail is by far the most usual one. Here the 
 repulsive force is much less than in the previous case, and 
 the comet may be said to be more completely and continuously 
 under the attractive control of the Sun. Some kind of hydro- 
 carbon gas is suggested as the constituent of tails of this class. 
 Tails of the Third Type, because they do not seem as a rule 
 capable of much expansion of size, are thought not to be subject 
 to any great amount of repulsive influence, but to be dominated 
 far more definitely by the normal laws of Gravitation. The 
 matter of which they are composed is thought to be in a state 
 indicative of far greater heaviness than obtains in either of 
 the two previous classes, and to consist of the vapour of iron, 
 perhaps also of sodium, and of other substances. It is quite 
 evident that these points are of a very speculative character ; 
 
FIG. 173 
 
 PLATE LI 
 
 154] 
 
 Halley's Comet, Naked-eye View in Mexico (Z.. G. Leon), 
 
FIG. 174 
 
 PLATE LI I. 
 
 Curious Aspect of the Head of Halley's Comet, June 8, 1910. 
 
 (L. G. Leon.} 
 
 L'55 
 
CLASSIFICATION OF TAILS. 155 
 
 but still Bredichin's ideas cannot be condemned as destitute 
 of possibility and probability. 
 
 An experienced American astronomer, Professor W. H. 
 Pickering, of Harvard College Observatory, divides the tails 
 of comets into two classes, and sets up a distinction on lines 
 entirely different from those of Bredichin. He seems to con- 
 sider that, either simultaneously or successively, as the case 
 may be, a tail which we should at the first glance regard as a 
 simple tail, really, when carefully looked into, may comprise 
 either simultaneously or successively a tail which has its origin 
 in the comet's head, surrounding and enveloping which there 
 is another tail (which perhaps rather should be called an en- 
 velope), which is of a different and uncertain origin. Pickering 
 says that, "judged by the photographs of recent comets, the 
 former kind is much the more common of the two, and 
 consists usually of a bunch of rays, more or less straight, pro- 
 ceeding from the nucleus directly away from the Sun." He 
 thinks that his second type of tail is well represented in the 
 pictures in existence of the "great comet of 1811," of the 
 " great comet of 1901," and of the first comet of 1910. He 
 considers that Swift's comet, of 1892 (i), was an instance of 
 both types of tail being present at the same time, and that 
 Halley's comet in 1910 was a case of a comet having a tail 
 of a different type after its perihelion passage from what it had 
 before the perihelion passage ; that at the earlier period the 
 tail had its origin in the nucleus, but that at the later period 
 the tail was altogether different, and was a large envelope, 
 wrapping up the head, but distinct from it. Pickering goes 
 on to suggest that the enveloping type of tail is much smoother 
 in structure than the type which issues from the nucleus, and 
 that it is the kind which seems to have been present in at least 
 three of the five great comets of the igth century, namely, 
 thoseofiSii, 1858, and 1882. 
 
 The foregoing classifications, however we may regard them, 
 do not directly help us in coming to a conclusion as to the 
 
156 COMETS. 
 
 originating cause of a tail where a comet, when discovered, is 
 tailless, and afterwards becomes furnished with a tail. As to 
 this the theory generally favoured by astronomers nowadays 
 is that what is called " light pressure " is concerned in the 
 creation of cometary tails, probably under impulses which 
 cannot yet be defined or explained, but which are of electrical 
 character. " Light pressure," as a phrase standing by itself, 
 may conveniently be defined as being based on the supposition 
 that all sources of light exercise a sort of repulsive push on all 
 materials on which the light impinges, whatever may be the 
 source of the light or the nature of the material. 
 
 Thus far the attention of the reader has only been called 
 to a few general propositions which might throw light upon 
 naked-eye observations of any casual comet which might 
 appear ; but much more must be said if we would obtain a 
 comprehensive grasp of cometary astronomy. The question 
 of the number of the comets and of their paths through space 
 opens up a variety of topics which, though in a certain sense 
 subsidiary to what has gone before, are of the greatest intrinsic 
 interest. 
 
 In olden times it was not considered that comets, as regards 
 their movements, were subject to any laws, but that they came 
 and went away in a perfectly haphazard fashion. It was not 
 until quite modern times that it was realised that they were 
 subject, to a certain extent, to the same laws of motion as 
 operated in the case of the planets. The situation of things 
 is this : whilst it is true that a large number of comets come 
 to us from whence we know not, and then pass away whither 
 we know not, yet there are a certain, not inconsiderable, 
 number which may be regarded as permanent members of 
 the solar system, and come and go, and after a certain interval 
 come back again. These are termed " periodical comets," 
 and bear a certain analogy to the planets as regards their 
 movements, the principal point of difference being that, whereas 
 the planets all move in orbits not materially differing from 
 
FIG. 175 
 
 PLATE LIII. 
 
 The Great Comet of 1811, 
 
FIG. 176 
 
 PLATE LIV. 
 
 JS 
 
 [157 
 
PERIODICAL COMETS. 157 
 
 circles, not a single comet moves in an orbit which is anything 
 like a circle. The orbits of the periodical comets are all of 
 them ellipses of great eccentricity. Perhaps this will be better 
 understood by saying that all the periodical comets move in 
 oval orbits, which may be compared roughly to flattened circles. 
 
 The orbits of the periodical comets not only differ much in 
 eccentricity, but also in their dimensions. Thus it comes 
 about that Encke's comet, with its period of only a little more 
 than three years, performs its journey round the Sun in an orbit 
 within that of the planet Jupiter, whilst Halley's comet travels 
 so far away from the Sun in the course of its voyage of 75 
 years that when at its greatest distance it is quite outside 
 what we call the solar system, because it attains a point 
 outside the orbit of Neptune, the most remote of the known 
 planets. 
 
 The comets which are not periodic so far as we know, come 
 to us in paths which the mathematician calls "parabolas" and 
 " hyperbolas," though the number of the comets which have 
 been known for a certainty to have pursued hyperbolic orbits 
 are very limited. 
 
 Going back to the periodic comets whilst the known or 
 supposed periods vary between a handful of years and thou- 
 sands of years, they may be roughly grouped in three classes : 
 
 (1) Comets with periods between 3 and 15 years. 
 
 (2) Comets with periods averaging 70 years. 
 
 (3) Comets with periods of many hundreds of years. 
 
 Of only those comets which belong to Classes I and 2 can it 
 be positively asserted that they are permanent members of the 
 solar system. This is certain, because they have proved their 
 allegiance to the Sun by having paid him more than one visit ; 
 indeed several of them have paid several visits. Our know- 
 ledge of the comets in the third class is much less certain, for 
 the reason that, owing to the length of their periods, no oppor- 
 tunity has yet occurred for them to pay us a return visit. There 
 is indeed one comet of long period which astronomers once 
 
158 
 
 COMETS. 
 
 hoped might safely be regarded as a permanent member of the 
 system ; but the supposition still lacks proof. There appeared 
 in 1556 a brilliant comet which was thought at one time to be 
 a second appearance of the great comet of 1264, one of the 
 grandest on record. Its return about 1860 was confidently 
 reckoned on by many astronomers, but all were disappointed. 
 There have been other comets observed during recent years, 
 which, it has been calculated, move in elliptic orbits, and must 
 therefore be periodic in a literal sense ; but, as the periods of 
 some of these amount to thousands of years, it is evident, not 
 only that the world will have to wait for a very long time before 
 seeing them, but also that doubt attaches to the exact 
 characters of their orbits, owing to the vast extent of the 
 same, to say nothing, in some instances, of the lack of a 
 sufficient number of trustworthy observations when they were 
 within our reach. 
 
 The following are the names of the short-period comets 
 which may be regarded as well-recognised members of the 
 solar system : 
 
 No. 
 
 Name. 
 
 Period 
 in years. 
 
 Next 
 retui n. 
 
 I. 
 2. 
 
 3- 
 
 4- 
 5 
 
 Encke's . . . ; 
 Tempel's Second (1873, ii.) . 
 Tempel-Swift's . . . 
 Winnecke's . . . ". ; 
 
 3-29 
 
 5 ! S 
 
 5'53 
 5'54 
 5-58 
 
 1914 
 1914 
 1914 
 
 *9*5 
 
 1912 
 
 6. 
 
 7 
 
 Finlay's ..... 
 D'Arrest's 
 
 6-54 
 664 
 
 1913 
 1917 
 
 8. 
 
 Wolfs 
 
 676 
 685 
 
 1918 
 i9 T 3 
 
 10. 
 n. 
 
 I 2 
 
 Borelly's 
 Brooks's Second (1889 v.) . 
 
 7-00 
 707 
 
 7'44 
 
 1918 
 1917 
 1918 
 
 13 
 
 Tuttle's 
 
 13-66 
 
 19*3 
 
 
 
 
 
FIG. 177 
 
 PLATE LV. 
 
 15.31 
 
FIGS. 178-183 
 
 PLATE LVI. 
 
 June 30. 
 
 July 6. 
 Thft nntnp.t nf 18fiO. 
 
 July 
 ( r.a.-b<hp.Up.tt.i and 
 
FAMILIES OF COMETS. 
 
 159 
 
 With reference to two or three of the comets in the fore- 
 going list, the date of whose next return is suggested, it is 
 
 Fig. 184. The Comet Families of Saturn, Uranus, and Neptune 
 
 (Drawn by H. C. Wilson). 
 
 to be understood that, though they have made several returns 
 in the past, they have not been seen very recently, and in some 
 degree a mystery hangs over them, their orbits appearing to 
 
i6o 
 
 COMETS, 
 
 have been deranged by the influence of the planet Jupiter. 
 The whole group of 13 consists of small comets not as a rule 
 visible to the naked eye, though some of them are some- 
 times so visible when favourably placed with respect to the 
 Earth and the Sun. 
 
 All the comets in the list on p. 158, except Tuttle's, are to 
 be regarded as members of what is called the " Jupiter family 
 of comets," and some other comets whose orbits are not at 
 present well established will probably be put in the same group 
 at a future time. It is considered now that all the superior 
 planets beyond Jupiter, namely, Saturn, Uranus, and Neptune, 
 have " families " of comets associated with them. 
 
 The long-period comets which are recognised as being 
 those which it is safe to regard as members of the solar 
 system, though not all of them have been seen twice, are the 
 following : 
 
 No. 
 
 Name. 
 
 Period 
 in years. 
 
 Next 
 return. 
 
 I. 
 2. 
 
 Westphal's(i852, iv.) . 
 Pons's(i8i2) .... 
 
 6o(?) 
 70-68 
 
 1913 
 
 J 955 
 
 3- 
 
 Di Vice's (1846, iv.) . 
 
 73'25 
 
 1919 
 
 4- 
 
 Olbers's (1815) .... 
 
 74'5 
 
 iq6o 
 
 5- 
 
 Brorsen's (1847, v.) 
 
 74'97 
 
 1922 
 
 6. 
 
 Halley's 
 
 76-78 
 
 1986 
 
 
 
 
 
 The only one of these six comets which calls for any special 
 mention is the last-named, Halley's ; but the story of Halley's 
 comet is now so well known that it would be tedious to give it 
 at any length. 
 
 Sir Isaac Newton and Edmund Halley share between them 
 the honours of the comet which now bears the name of the 
 latter, and even in a skeleton form its story is very interesting. 
 Sir Isaac Newton gave to the world in 1687 his celebrated 
 
HALLEY'S COMET. 161 
 
 treatise on Universal Gravitation which is best known by the 
 simple name Principle but of which the full title is Philoso- 
 phice Naturalis Prinoipia Mathematica. The cost of publishing 
 this book appears to have been borne by H alley, and, after 
 studying his venture, the idea came into his head to try and 
 see whether Newton's labours could be utilised for obtaining 
 some insight into the movements of comets. A comet seen 
 by Halley himself in 1682, though not discovered by him, 
 seemed to offer the desired opportunity, and he calculated its 
 orbit on Newton's principles. One thing led to another, and, 
 after finishing his calculations with regard to the comet of 
 1682, he turned his attention to the recorded observations of 
 comets which had appeared in 1607 and 1531. The results 
 as to the nature of their orbits were so nearly identical in 
 all particulars that he did not long hesitate in coming to the 
 conclusion that the three comets were really one comet, and 
 that therefore it was a periodical member of the solar system. 
 He had sufficient confidence in his own work to venture on the 
 prediction that the comet would return again about 1758 ; and 
 so it did. The story of its discovery on the night of Christmas 
 Day of that year by a Saxon farmer named Palitzsch, living near 
 Dresden, and of the calculations made in anticipation of its 
 return, is a thrice-told tale. Halley died in 1742, and left 
 behind him a plaintive record of his hopes that " impartial 
 posterity will not refuse to acknowledge that this [periodicity] 
 was first discovered by an Englishman." 
 
 Halley's Comet paid another visit to these parts of Space in 
 1835, and the whole subject of mathematics as applied to orbits 
 had made such progress between 1758 and 1835 that the comet's 
 perihelion passage, as calculated, was found to be wrong only 
 to the extent of about 4 days. 
 
 The last return of Halley's Comet to perihelion in the spring 
 of 1910 will be fresh in the minds of all my readers how it was 
 for the inhabitants of the northern hemisphere a great disap- 
 pointment, whilst dwellers on the opposite side of the world 
 ii 
 
1 62 COMETS. 
 
 enjoyed a magnificent sight. The pictures annexed will give 
 its appearance at various times, and as seen in various places. 
 In England it showed itself as quite an ordinary comet, just 
 visible to the naked eye, and not very conveniently placed, 
 being near the Sun in the evening twilight. But, after its peri- 
 helion passage on April 19, when it had passed round to the 
 other side of the Sun, and was visible in the early morning, 
 those who had that opportunity by reason of their being in 
 Africa, Australia, or New Zealand, saw the comet as a magnifi- 
 cent object with a tail extending half over the celestial vault. 
 
 The world-wide interest felt in Halley's Comet in 1910 is 
 well shown by the following account of it which came from the 
 far-off island of New Guinea : 
 
 " On May 9 the comet, looking like a muffled star, was seen 
 in the East, and its tail, a broad beam of brilliant light, ex- 
 tended upwards through about 30. Below the comet and a 
 little to the South of it Venus shone like a little moon, appear- 
 ing far bigger than any planet I have ever seen. The comet 
 grew enormously, and in the early morning of May 14, the last 
 time that we saw it completely before it had passed the Earth, 1 
 .the tail blazed across the heavens like an immense searchlight 
 beam to the zenith and beyond. On May 26 it appeared 
 again in the evening reduced in size to about 45, and several 
 nights we watched it growing always smaller, until it vanished 
 from our sight. Superlative expressions will not describe 
 Halley's Comet as we saw it in New Guinea ; it was a wonder- 
 ful appearance and one never to be forgotten. Our coolies 
 and the Javanese declared that it portended much sickness 
 and death. Though we tried to question them about it, we 
 never learnt how it impressed the minds of the natives." 2 
 
 A matter which caused much discussion, both as a matter of 
 prophecy and fulfilment (or non-fulfilment), was whether the 
 comet had crossed the Sun as seen from the Earth, and 
 whether it had been detected whilst doing so. The conclusions 
 
 1 A probable mistake for Sun. 
 
 3 WOLLASTON, Pigmies and Papuans* 
 
FIG. i8c; 
 
 PLATE LVII. 
 
 Halley's Comet, May 1, 1910. 
 
 Photographed at the Transvaal Observatory. 
 
FIGS. 186-191 
 
 PLATE LVIII. 
 
 May 5, 3- l 5-l-45 a.m. C.T.S. 
 
 May 13, 3.10-3.37 a.m. C.T.S. 
 
 May 30, 9.20-9.60 p.m. C.T.S. June 5, 10.00-10.30 p.m. C.T.S. 
 
 Halley's Comet, 1910 (D. W. Morehouse). 
 
 [163 
 
HALLEYS COMET IN IQIO. 
 
 1 6 3 
 
 arrived at were indeterminate : it is probable that the comet did 
 cross the Sun's disc, and ought to have been seen, but it was 
 not seen. On the other hand, it appears quite certain that the 
 Earth passed through some part of the comet's tail, though 
 nothing inconvenient happened. 
 
 It may be stated, by the way, that the question of a collision 
 
 JUNE 6 
 
 SCOMKI 
 
 EARTH 
 
 Fig. 192. Path of Halley's Comet, 1910. 
 
 between a comet and the Earth has often occupied men's minds 
 in past times, and given rise to panics ; but there never has been 
 the slightest justification for alarm. It is quite certain that in 
 1 86 1 the Earth passed through a very thick part of the tail of 
 the great comet of that year, but nothing happened beyond a 
 sensation of fogginess which impaired the light of the Sun, 
 
164 
 
 COMETS. 
 
 shining at the time, and led in one case, at least, to a demand for 
 artificial light at the early hour of 7 p.m. on June 30, when it 
 was also noted that the sky had a yellow auroral glare, the Sun 
 shining, but not as usual. 
 
 To give a list of all the comets to which might be applied the 
 adjective " celebrated," and still more to describe them, would 
 run into many pages. Let it suffice, then, to mention the 
 following, belonging to the igth century: 1811, 1825, 1843, 
 1858, 1861, 1874, 1880, and 1882. Thus far in the 2Oth century 
 we have had only Halley's (1910), and one or two which can 
 
 only be 
 described 
 as good 
 second- 
 class 
 c o m e t s 
 (1902, i. ; 
 1910, i.). 
 
 The 
 spectro- 
 scope has, 
 of course, 
 been ap- 
 plied to 
 
 comets, as to other celestial objects. The general result is 
 to show that cometary spectra, more often than not, belong 
 to one type only, that of the hydro-carbons. 
 
 Up to the present time historians and astronomers together 
 have recorded a total of about uoo comets. Of course down 
 to the 1 7th century the comets noted were all naked-eye 
 ones ; but, seeing how nowadays the naked- eye comets fall 
 short in number of the telescopic comets, it is safe to assert 
 that, since the Christian era, several thousand cornets have 
 visited our system. 
 
 In case a reader may be surprised at the number of comets 
 
 Fig. 193. The Warner Prize Medal. 
 

 
 165 
 
1 66 COMETS. 
 
 discovered in America of late years having been so large com- 
 pared with the number discovered in all other parts of the world, 
 it may be worth while to mention that in America prizes in 
 money and medals are systematically awarded to those who are 
 able to prove priority in picking up new comets. The Warner 
 gold medal, illustrated on p. 164, is one of the stimulants which 
 American astronomers have before them to encourage zealous 
 work on behalf of science. 
 
 This chapter may be usefully concluded by some brief notes 
 in detail on the comets which have been selected to illustrate it. 
 
 THE GREAT COMET OF 1744. 
 
 This comet historically was long a mystery, for the statement 
 that it had 6 tails, announced in books all over the world, was 
 very generally distrusted because it depended on the unsup- 
 ported testimony of one man. But some years ago, in a curious 
 way, there came out evidence of a contemporary writer that the 
 comet had really possessed a number of separate tails ; and the 
 illustration here given shows that there were not only six, but 
 considerably more than six tails. The number of six seems to 
 have been arrived at by counting the streamers in pairs, each 
 pair comprising the two sides of one tail properly so-called. 
 
 THE GREAT COMET OF 1843 (i.). 
 
 This comet appeared with great suddenness, and was endued 
 with peculiarly rapid motion, and had a tail fully 100 long. It 
 would seem to have been one of the grandest comets on record, 
 and, comparing together the testimony of those who on the one 
 hand had seen the great comet of 1811 as well, and on the 
 other hand those who had not seen 1811 but had seen Donati's 
 Comet of 1858, I consider that one is justified in saying that 
 the 1843 comet was the grandest of the iQth century in point of 
 size and brilliancy. 
 
FIG. 195 
 
 PLATE LIX. 
 
 Coggia's Comet, 1874, on July 13 (F. Brodie). 
 
 1661 
 
FIG. 196 
 
 PLATE LX. 
 
 [i66 
 
FIGS. 197-198 
 
 PLATE LXI. 
 
FIGS. 199 200 
 
 PLATE LX1I. 
 
 Nov. 13. 
 
 and 
 
 Nov. 21. 
 nf thp 
 
 Tftrnpt of 1882. 
 
FIGS. 201-202 
 
 PLATE LXIII. 
 
FIGS. 203-204 
 
 PLATE LXIV. 
 
 [167 
 
CELEBRATED COMETS. 167 
 
 DONATI'S COMET, 1858 (vi.). 
 
 This comet, though inferior in size, as just stated, to the great 
 comet of 1843, may be regarded as having been the most 
 beautiful comet of the igth century, owing to its plume-like 
 shape, and to its possession of certain long, straight streamers 
 not reproduced in the engraving. The star visible near the 
 comet's head is Arcturus. 
 
 THE COMET OF 1860 (Hi.). 
 
 This comet was not one of very remarkable size, but the 
 pictures are given for the reason that they exemplify in a strik- 
 ing degree the jet-shaped emanations which occasionally are 
 noticed to proceed from the head of a comet. This feature was 
 also brought out in a very marked manner in the comet of 
 1862 (ii.). 
 
 COGGIA'S COMET, 1874 (iv.). 
 
 Coggia's Comet of 1874 may be described as a good specimen 
 of a second-class fine comet. It was a striking object in the 
 evening sky during the month of July, but it is engraved in this 
 book as being a good example of the way in which some comets 
 seem to shed off independent envelopes, or shells of matter, one 
 after another. 
 
 THE GREAT COMET OF 1882 (iii.). 
 
 This was a fine naked-eye comet, with a tail very much in the 
 shape of a Turkish scimitar. The main tail gave one the 
 impression of being inside a long and wide, but very ethereal or 
 flimsy, envelope. But the special feature of this comet was its 
 nucleus, which was and still is unique in its form. It was 
 elliptical, and of great length in proportion to its breadth ; it 
 
1 68 COMETS. 
 
 was placed longitudinally with regard to the general direction 
 of the tail ; and, to crown all, instead of having the usual one 
 special bright centre, it was always seen to have three bright 
 centres, sometimes four, and on one occasion a fifth was 
 suspected, all of them a little distance from one another. 
 
 SWIFT'S COMET, 1892 (i.). 
 
 We have passed now from the epoch of hand-drawn pictures 
 of comets to representations based upon photography. Whilst 
 it is, of course, a truism that the Sun is a more accurate drafts- 
 man than the human eye and hand together, it must be confessed 
 that photography often fails to bring home to the eye many 
 details which sometimes strike even the most inattentive 
 observer. 
 
 But this cuts both ways, because not only in the case of 
 comets, but also in the case of nebulae, photography frequently 
 catches features which are invisible, not only in the telescope 
 used by a particular observer, but in all telescopes, whatever may 
 be their size. It was owing to photography that Swift's Comet 
 was the first to bring out features connected with the tails of 
 comets which may be said to have revolutionised our ideas as 
 to the physical condition of those bodies. Barnard well remarks 
 that this " has occurred in the case of comets with which the 
 older method of observing would have promised little or nothing 
 of interest." Swift's comet may be mentioned as one of those 
 which seemed to be endued with a rotation of the head and tail 
 about an axis passing lengthwise through the tail. 
 
 RORDAME'S COMET, 1893 (ii.), 
 
 illustrates a remark in the last paragraph about photography, 
 bringing out details not readily grasped by the naked eye, for 
 some of its peculiarities are of the same sort as those of Swift's 
 Comet. 
 
FIGS. 205-208 
 
 PLATE LXV. 
 
 J68] 
 
FlGS. 20Q-2I2 
 
 PLATE LXVI. 
 
 .I68 
 
FIGS. 213-214 
 
 PLATE LXVIT. 
 
 I68&] 
 
FIGS. 21 s-2i6 
 
 PLATE LXVIII. 
 
 Oct. 21. 
 
 Oct. 22. 
 
 Brooks's Comet of 1893 (iv.). 
 
 (168 
 
FIG. 217 
 
 PLATE LXIX. 
 
 Borelly's Comet of 1903 (iv.), ( /?. /. Wallace}. 
 
 I68./J 
 
FIG. 218 
 
 PLATE LXX. 
 
 Dec. 29, 1905. 
 Giacobini's Comet of 1906 (i.), (E. E. Barnard}. 
 
FIGS. 219-220 
 
 PLATE LXXI. 
 
 Dec. 29, 1905. 
 
 168 f] 
 
 Jan. 5, 1906. 
 
 Giacobini's Comet of 1906 (i.), (E. E. Barnard}. 
 
FIG. 221 
 
 PLATE LXXII. 
 
REMARKABLE COMETS. 169 
 
 BROOKS'S COMET OF 1893 (iv.). 
 
 This seems to have been a comet damaged by some external 
 violence, strange as the idea may seem. Barnard wrote thus 
 about it : 
 
 " Indeed, the singular freaks of that comet's tail compel us 
 to seek an explanation in some outside cause inherent neither 
 in the comet nor in the Sun. The tail, which one day was in 
 a normal condition, was on the next broken and disturbed, as 
 if it had encountered some resisting medium in its flight 
 through space. The disturbance seemed to come from the 
 direction towards which the comet was moving. On the suc- 
 ceeding morning it was badly broken, and hung in cloud-like 
 masses, some of which were entirely torn off from the tail and 
 appeared to be drifting away in space. On another occasion 
 the tail was concave towards the direction of motion, and had 
 the appearance of beating against a current of resistance. It 
 was disjointed in places, and near the end was abruptly bent 
 at nearly a right angle, as if at that point it had encountered a 
 stronger current of resistance. If one examines these pictures 
 there seems no escape from the conclusion that this comet's 
 tail did actually encounter some resisting or disturbing medium 
 about October 21, 1893, and for several days subsequent to that 
 date ; whether this was a swarm of meteors such as we know 
 exist in space near the Sun, or some sort of resisting matter, of 
 which we as yet know nothing, is a subject for time to settle." 
 
 BORELLY'S COMET, 1903 (iv.). 
 
 This comet manifested signs of disintegration of a curious 
 nature that is to say, signs of a part of its tail having actually 
 broken off from the main tail ; which latter, after losing the 
 aforesaid fragment, began to grow again in consequence of a 
 new supply of matter being forthcoming from the nucleus. 
 
 GIACOBINI'S COMET, 1906 (i.). 
 
 Observations of this comet were unfortunately much interfered 
 with owing to the prevalence of bad weather ; but, notwith- 
 
170 COMETS. 
 
 standing this, Barnard got some good photographs of it, and 
 was also able to make some striking notes. He says that the 
 comet's appearance on December 29, 1905, was 
 
 "in some respects quite unique. From a rather large head 
 and a slender neck, the tail widens out on each side in a 
 graceful curve, which partly closes in again and gives a strong 
 convexity to the tail. The edges of these convexities are 
 sharply defined, and are outlined by a rather narrow bright rim 
 or border. The appearance of the tail strongly suggests a 
 hollow, convex, transparent cone with a sensible thickness. A 
 straight-edge placed along the sides of the tail shows this 
 convexity strikingly, as may be seen on an examination of the 
 plate. I have not noticed quite this appearance before in a 
 comet's tail." 
 
 DANIEL'S COMET, 1907 (iv.). 
 
 The original negative of this comet showed the tail to have 
 six branches, but, owing to the extreme faintness of two of 
 them, only four are depicted in the illustration. The star near 
 the end of the tail with a black dot in it was y Geminorum. 
 
 MOREHOUSE'S COMET, 1908 (Hi.). 
 
 This comet, though not in itself a very large one, attracted 
 considerable notice in the astronomical world owing to the 
 transformations which it underwent. The two pictures, both 
 dated October 1 5, taken, one in England and the other in 
 America, within a few hours of one another, will give a clue to 
 the cause of this excitement. Barnard's photograph vividly 
 brings out the fact that the tail of the comet underwent a 
 serious and real disruption. 
 
 H ALLEY'S COMET, 1910 (ii.). 
 
 So much has been said already about Halley's Comet that 
 it seems only necessary here to remind the reader that it was 
 only in the Southern Hemisphere, and after the comet had 
 
FIG. 222 
 
 PLATE LXXIII. 
 
 On Oct. 15, at 14 h. 3iTm. 
 
 Morehouse's Comet of 1908 (Hi.), (E. E. Barnard}. 
 
 170] 
 
FIGS. 223-224 
 
 PLATE LXXIV. 
 
 Nov. 15, 12 h. 6 m. G.M.T. 
 
 Morehouse's Comet of 1908 (iii.), (Yerkes Observatory). [170* 
 
FIG. 225 
 
 PLATE LXXV. 
 
 Morehouse's Comfit of 1908 (iii.\. on Nov. 13. 
 
FIGS. 226-229. 
 
 PLATE LXXVI. 
 
 May 25. 
 
 May 27. 
 
 May 28. June 2. 
 
 Halley's Comet, 1910 (C. H. Gingrich}. 
 
PLATE LXXVII. 
 
 
 The Daylight Comet of 1911 (W. B. Gibbs}. 
 
 As seen in North Africa. 
 
FIGS. 231-232 
 
 PLATE LXXVIII. 
 
 o 
 
 f 
 
 o 
 
REMARKABLE COMETS. 171 
 
 passed its perihelion, that the most striking views of it were 
 obtained. Hence it comes about that the pictures here given 
 may excite distrust as to their accuracy on the part of dwellers 
 in the Northern Hemisphere. 
 
 BROOKS'S COMET, 1911 (<:). 
 
 The picture dated Sept. 24 [Plate LXXVIII.] brings out 
 the case of a comet with a very large head having a very 
 slender tail proceeding from it. The photograph vividly recalls 
 to my mind one of the earliest comets I ever saw. I am not 
 certain of the exact name and date, though I think it was one 
 of three visible in the summer of 1857, discovered by Klinkerfues 
 at Gottingen on August 20. 
 
 By way of a last word, it may be well to explain why, in 
 nearly all cases, the stars which appear in the comet-pictures 
 given in this volume show as streaks and not as points. It is 
 because the several comets being themselves in motion, it is 
 always necessary, when long exposures are desired (in order 
 to get good views of the comets), that the driving-clocks of the 
 telescopes employed should be timed to keep pace with the 
 comets rather than with the diurnal movement of the stars. 
 
CHAPTER X. 
 SHOOTING-STARS. 
 
 Various classes of luminous, meteors. Shooting-stars. Fireballs. 
 Aerolites. Radiant points of shooting-stars. Account of the most 
 important showers. Position in the heavens of some of the chief 
 radiant points. Historical allusions. Celebrated great showers. 
 Fireballs. Their general resemblance to one another. Re- 
 markable fireballs described by Webb and Brodie. Their sizes, 
 distances, and movements. Computation of their paths. Connection 
 between meteors and comets. Shooting-stars, fireballs, and aerolites 
 all of the same nature. Circumstances attending the fall of aerolites. 
 
 " SHOOTING-STAR " is the popular name for a celestial object 
 which is scientifically spoken of as a " luminous meteor," and 
 luminous meteors are subdivided into small luminous meteors 
 and fireballs, with what are called aerolites thrown in. 
 Though the first two subdivisions are visually closely allied, 
 the third may seem to be somewhat detached, though it is not 
 so in reality. A simple shooting-star is just exactly what its 
 name imports at first sight a star which shoots ; yet it is not 
 a star, and it does not shoot. 
 
 Postponing for a while a consideration of the nature of all 
 these bodies, we will first of all consider how and when they 
 show themselves. It is safe to say that several shooting-stars 
 may be seen on any clear night throughout the year when the 
 air is transparent and the Moon is absent. Thoughtlessly 
 looked at, the observer will fancy that they dart forth casually 
 in the sky, first at one point and then at another point ; but 
 such is not the case. It is true that these isolated meteors 
 
 172 
 
FIG. 233 
 
 PLATE LXXIX. 
 
 A Meteor in Flight (E. E. Barnard). 
 
 ("The object gradually increased in brilliancy, and as gradually faded 
 172] out, ending in two short flashes of light.") 
 
FIG. 234 
 
 PLATE LXXX. 
 
 ^ 
 
 i 
 
 3 
 | 
 
 o- 
 
 w 
 
 
 [173 
 
TELESCOPIC METEORS. 
 
 173 
 
 used to be thought independent of one another, and they were 
 formerly called " sporadic " meteors, which meant that they 
 were haphazard outbursts of light. The designation has, 
 however, now lost nearly all its importance and significance, 
 because the prolonged observation which has been given to 
 these bodies during recent years has enabled astronomers to 
 realise that they 
 belong to 
 families, each 
 with its own 
 centre in the 
 heavens, which 
 is called its 
 "radiant point." 
 The recognised 
 radiant points 
 are now very 
 numerous, in- 
 deed, several 
 hundred in 
 number ; but of 
 these the 
 majority would 
 not readily 
 attract notice 
 except after 
 prolonged and 
 patient atten- 
 tion. On the other hand, there are a certain few radiant 
 points from which, at definite dates, and in great numbers, 
 shooting-stars emanate ; and it is to these that I will in the 
 first instance direct the reader's attention. 
 
 The most important shower of shooting-stars is undoubtedly 
 that named the Perseids, because they belong to the constella- 
 tion Perseus and show themselves on or about August 10. 
 
 Fig. 235. Flight of Telescopic Meteors 
 
 (Brooks). 
 
174 SHOOTING-STARS. 
 
 Meteors may be noticed some days before and some days after 
 the precise date just mentioned. They constitute a very rich 
 annual shower of swift and bright meteors, which leave streaks 
 behind them. The approximate centre of the shower may be 
 taken to be a point 4 N.E. of the star rj Persei ; say, Right 
 Ascension 3 h. 4 m., and Declination 57 N. 
 
 The next most important shower is that appertaining to the 
 constellation Andromeda, and known as the Andromedes, with 
 the radiant point about 4 N.W. of the star y Andromedae ; say, 
 Right Ascension i h. 40 m., and Declination 44 N. Date : 
 November 27. 
 
 The third most important shower may be said to be the 
 Lyrids, belonging to the constellation Lyra, with the radiant 
 point about 85 S.W. of a Lyrae ; say, Right Ascension 18 h., 
 Declination 33 N. These meteors move swiftly, and the 
 brighter ones leave streaks. Date : April 20. 
 
 The next few paragraphs will give some of the more im- 
 portant showers, arranged in the order of dates from January 
 onwards. 
 
 January 2, the Quadrantids, belonging to the constellation 
 Quadrans. The radiant point will be found about 12 N.N.E. 
 of /3 Bootis ; say, Right Ascension I5h. 29m., and Declina- 
 tion 53 N. This is a rich annual shower. 
 
 July 28, the Aquarids, belonging to the constellation Aquarius. 
 The radiant point will be found about 5 N.N.W. of 8 Aquarii ; 
 say, Right Ascension 22 h. 36 m., and Declination 12 S. This is 
 an active display of slow and enduring meteors which may be 
 depended upon to recur annually. 
 
 October 18, the Orionids, belonging to the constellation 
 Orion. The radiant point will be found 2 E. of v Orionis ; say, 
 Right Ascension 6h. 8 m., and Declination 15 N. This is a 
 very rich shower, which occurs every year, and, though dated 
 for October 18, watch for it should begin on October 9, and be 
 continued till October 29. 
 
 November 13, the Leonids, belonging to the constellation 
 
SHOWERS OF METEORS. 175 
 
 Leo. The radiant point will be found 3 W.N.W. of y Leonis ; 
 say, Right Ascension ioh., and Declination 22 N. This is a 
 great historic shower, which manifested sensational displays in 
 1799, 1833, and 1866, and did not reappear in its pristine 
 splendour, as was confidently expected, in 1899. A slight dis- 
 play certainly belonging to this shower may be expected every 
 year between November 9 and 17. 
 
 November 20, the Taurids, belonging to the constellation 
 Taurus. The radiant point will be found 5 N.N.W. of 
 v Tauri ; say, Right Ascension 4h. 8m., and Declination 23 N. 
 This is a well-known shower of slow meteors. 
 
 December 10, the Geminids, belonging to the constella- 
 tion Gemini. The radiant point will be found 3 W.N.W. of 
 a Geminorum ; say, Right Ascension 7 h. 22m., and Declina- 
 tion 33 N. 
 
 It will be understood that the showers enumerated in the 
 preceding paragraphs are those which may be regarded as 
 the most notable ; but, as has already been stated, shooting- 
 stars belonging to many other groups may be noticed almost 
 every night in the year. It would take up too much space 
 in these pages to specify, and state the positions of, even a 
 tithe of the other recognised radiant points ; but observations 
 of luminous meteors, small as well as large, may be suggested 
 to amateurs as a very interesting study, the fruits of which, if 
 collected and tabulated with care, will be very useful in pro- 
 moting the progress of meteoric astronomy. Denning has 
 remarked that brilliant meteors often emanate from the con- 
 stellation Scorpio in the month of June. This might be a 
 suggestion worth following up. 
 
 Shooting-stars often appear in the pages of history, and 
 have done so from ancient times. One of the earliest allusions 
 to them dates from A.D. 472, when we are told by Theophanes, 
 the Byzantine historian, that the sky at Constantinople ap- 
 peared to be on fire with flying meteors. A remarkable dis- 
 play took place in England and France on. April 4, 1095, when, 
 
176 SHOOTING-STARS. 
 
 the stars seemed to be " falling like a shower of rain from 
 heaven upon the Earth." 
 
 There was a great display on November 13, 1799, visible 
 throughout America, and of which Alexander Humboldt has 
 left a thrilling narrative ; but the greatest display on record 
 appears to have been that of November 13, 1833, following 
 fine displays in 1831 and 1832. The 1833 shower was visible 
 over nearly the whole of North America, and, from the accounts 
 which have reached us, it must have been one of imposing 
 grandeur. In many parts of the country the population, 
 especially the Negro population, were terror-stricken, such 
 was the beauty and magnificence of the spectacle presented. 
 The following account is from the pen of a planter in South 
 Carolina : 
 
 " I was suddenly awakened by the most distressing cries that 
 ever fell on my ears. Shrieks of horror and cries for mercy 
 I could hear from most of the Negroes of the three plantations, 
 amounting in all to about six or eight hundred. While earnestly 
 listening for the cause I heard a faint voice near the door 
 calling my name. I arose, and, taking my sword, stood at the 
 door. At this moment I heard the same voice still beseeching 
 me to rise, and saying, ' O my God, the world is on fire ! ' I 
 then opened the door, and it is difficult to say which excited 
 me the most the awfulness of the scene or the distressed 
 cries of the Negroes. Upwards of one hundred lay prostrate 
 on the ground some speechless, and some with the bitterest 
 cries, but with their hands raised, imploring God to save the 
 world and them. The scene was truly awful ; for never did 
 rain fall much thicker towards the Earth. East, west, north, 
 and south it was the same." 
 
 Though I have spoken of shooting- stars as being visible 
 almost always everywhere, this statement must not be taken 
 to imply a uniform distribution over the heavens, because it 
 is evident that in certain hours of Right Ascension (that is, 
 in the constellations occupying those hours) there are more 
 centres of meteor-radiation than in others. In other words, 
 
RADIANT POINTS OF METEORS. 
 
 177 
 
 that meteor-centres are most abundant in the first 4 hours 
 of R.A., whilst they are fewest in the hours between X and 
 XIV hours. A somewhat similar disparity may be traced 
 in the declinations, there being an obvious maximum between 
 41 and 60 of North Declination. These results are due to 
 the un- 
 tiring in- 
 dustry of 
 Denning, 
 who is our 
 principal 
 meteor 
 observer. 
 Unfortu- 
 nately, no 
 c o r r e - 
 s p o n d - 
 ing sta- 
 tistics are 
 available 
 for the 
 Southern 
 Hemi- 
 sphere, 
 becaus e 
 luminous 
 meteors 
 have 
 never 
 
 been catalogued and studied there as they have been in the 
 Northern Hemisphere. Dissecting the year by months, it 
 has been found that an overwhelming preponderance of 
 meteors are associated with the month of August ; indeed, 
 the two months of July and August together provide 50 per 
 cent, of the total number of meteors catalogued during the 
 
 12 
 
 Iju 
 
 Fig. 236. Meteor Radiant Point in Gemini 
 (Dec. 12) on Nov. 28 Dec. 9, 1864. 
 
178 SHOOTING-STARS. 
 
 past half-century that systematic observation of luminous 
 meteors has been carried on. 
 
 The character of a radiant point, and in some sense the 
 details of the observations which, under ordinary circumstances, 
 can be carried out in connection with it, will be better realised 
 by an examination of a plan (Fig. 236) showing the meteors 
 marked down on some particular night as having been, seen 
 emanating from the radiant point in question. 
 
 Fig. 234 represents an arrangement devised by Mr. F. W. 
 Longbottom for doing what he calls "fishing for meteors." 
 He arranges in a row several rapid cameras and takes his 
 chance of their being able to catch any meteors which may 
 show thtmselves in the regions of the sky towards which the 
 cameras point. The stars, of course, are shown by streaks, 
 but that does not matter, as their streaks can never be mis- 
 taken for the streak which a meteor would leave, the difference 
 between the two being always very marked. If the time of 
 commencing and finishing the exposure is noted, a map of 
 the stars recorded on the plate can be made by pricking 
 off their position on the trail at any desired moment. It is 
 a good plan to stop exposure when a meteor is seen to cross 
 the field covered by the camera-lens; then the end of each 
 star-trail shows the position of the stars at the moment the 
 photograph was taken, just before the actual attempt. It is 
 desirable that the exposures should be made so that the star- 
 trails (or most of them) begin and end on the plate, though, 
 of course, near the Pole the exposure would be long. The 
 time at which the meteor is seen should be noted, and also, 
 of course, any other particulars deserving to be recorded. 
 
 We will now proceed to consider the question of Fireballs. 
 It is doubtful whether any distinction of either origin or nature 
 can properly be drawn between shooting-stars and fireballs, 
 or .that there is any distinction at all between them excepting 
 that of size, to which perhaps may be added that of duration 
 of visibility. The grounds for this assumption of identity of 
 
PLATE LXXXI. 
 
 [78! 
 
FIGS. 238-247 
 
 PLATE LXXXII. 
 
 NEW HAVEN. ., 
 
 PALISADES. 
 
 HAVERFORD 
 
 Meteor as seen at New Haven, Conn.; Palisades, N.Y.; Haverford, Pa.; 
 and Williamstown, Mass., Nov. 14, 1868. 
 
First View. 
 
 Second View : 1783, Aug. 18 (Sanby and Robinson). 
 
 1878, June 7 (Denning). 
 
 1863, Oct. 19 (Schmidt). 
 
 Fireballs. 
 
l8o SHOOTING-STARS. 
 
 origin and nature between the two classes of bodies now under 
 consideration depend on the fact that various meteor-showers, 
 such as the Perseids and the Leonids, and many others, 
 whilst mainly consisting of star-like points of light, yet now 
 and again yield meteors of great brilliancy, comparable alike in 
 size and brilliancy to the isolated objects which are specifically 
 
 I. 2. 
 
 Figs. 252, 253. Curious Form of Trail left by the Fireball of 
 Oct. 19, 1877. 
 
 i. First effect. 2. Second effect (10 min. later). 
 
 termed " fireballs." Speaking generally, of course, it must be 
 confessed that the large and conspicuous fireballs of sufficient 
 size and importance to get into the newspapers appear in the 
 heavens singly, and, though usually noiseless, sometimes are 
 seen to burst, making a great noise. In this case they are 
 generally pear-shaped. When moving slowly they usually give 
 
FIRE-BALLS. l8l 
 
 forth trains of sparks, which either disappear promptly or 
 sometimes linger for many minutes, and drift slowly away, 
 apparently under the influence of currents of wind high up in 
 the atmosphere. 
 
 There is a strong family resemblance between all fireballs, 
 and a drawing of one would be typical of a large number, as 
 will be realised by an examination of the illustrations here 
 
 Fig. 254. Successive Changes in a Fireball during its Visibility. 
 
 given. As good a description as could be had of an average 
 fireball will be found in the following account of one seen by 
 the Rev. T. W. Webb on November 12, 1861. He said : 
 
 "We were walking, a party of three persons, along a wide 
 turnpike road, fully lighted by a Moon 10 days old, when we 
 were surrounded and startled by an instantaneous illumination, 
 not like lightning, but rather resembling the effect of moon- 
 light suddenly coming out from behind a dark cloud on a windy 
 
ig 2 SttOOTlNG-SfARS. 
 
 night. It faded very speedily, but on looking up we all per- 
 ceived, at a considerable altitude, perhaps 60 or 70, a superb 
 mass of fire sweeping onwards and falling slowly in a curved path 
 
 down the W.S.W. 
 sky. . . . Ruddy 
 sparks, of the colour 
 of glowing coals, were 
 left behind at its 
 smaller end, and its 
 path was marked by 
 a long pale streak of 
 little permanency. 
 Its termination, un- 
 fortunately, was con- 
 cealed by boughs of 
 trees, among which, 
 however, it was traced 
 till possibly some 10 
 above the horizon, but 
 it had previously 
 undergone a great 
 diminution. . . . The 
 whole duration may 
 have been as much 
 as five seconds. Its 
 aspect was decidedly 
 that of a lignefied and 
 inflamed mass, and 
 the immediate im- 
 pression was that of 
 rapid descent." 
 
 The following 
 Fig. 255,-Meteor of Nov. 12, 1861 description of the 
 
 ( w ' bb )- luminous track of a 
 
 large meteor, seen 
 
 on February 22, 1909 (which seems to have been indeed a 
 fireball), and was widely observed along the S. coast of 
 England, is from the pen of Mr. C. G. Brodie. The meteor 
 was quite unique, I think, in the astonishing length and 
 
hn 
 
 
 
 183 
 
184 SHOOTING-STARS. 
 
 vagaries of the trail which it left behind. He says that on the 
 day in question 
 
 " While crossing to the Isle of Wight from Portsmouth, my 
 attention was called to a luminous streak in the southern sky. 
 I did not actually see the meteor, but this must have fallen 
 about 7.30 p.m., as we were leaving the harbour. The trail, 
 when I first saw it, extended from near Procyon, passing west 
 under a and y Orionis as a plain luminous streak somewhat 
 laminated in structure. Passing from W r . to S., it entered 
 Eridanus, zigzagging in a curious fashion, exhibiting a shoulder 
 reminding one of a bayonet, above p Eridani ; and then passing 
 S. and W. to about <r Eridani, where it ended in a bluish- 
 white, round, luminous nucleus. From this another streak 
 stretched directly eastwards, passing under the two lower stars 
 of Orion (/3 and /c) into Canis Major ; this streak was very thin. 
 The commencement of the upper streak between Procyon 
 and Orion next became curved upon itself, forming a large 
 loop, the cusp being downwards. Before we reached Ryde 
 (say 7.55 p.m. to 8 p.m.), the upper limb had drifted round 
 westwards into an almost vertical position, the angle became 
 less acute, and the nucleus disappeared, the lower streak 
 drifting southwards. The whole trail had become narrower 
 and less distinct. As late as 8.40, while driving from the 
 Wootton station, there was still a trace of the upright limb 
 in the western sky in the form of an irregular narrow streak. 
 Several people told me that the fireball was so brilliant as to 
 resemble the sudden turning on of an acetylene lamp behind 
 them. This shows that the meteor must have been exception- 
 ally bright, as the sky was clear and there was a young Moon. 
 The way in which the luminous track altered its position 
 suggested to my mind that it was drifting by the action of the 
 wind, which on that day was registered as S.-E., and the 
 day following was still easterly." 
 
 It has been found that certain dates may be stated at which 
 fireballs may specially be looked for. The following are some 
 of these dates: January 2, February 7, April 11-12, 19-20, 
 June 6, July 25-30, August 7-13, September 1-2, 6-7, November 
 1-2, 6-9, 11-15, J 9> 2 7> December 8, 11-12, 21. 
 
PATHS OF FIRE-BALLS. 185 
 
 Attempts have often been made to subject particular fire- 
 balls to computation as regards their distances, sizes, and 
 velocities ; but the suddenness of their appearance, and the 
 rapidity of their movements and of the changes which they 
 undergo render the results in all cases very uncertain. Subject 
 to this view it may be stated that their height above the 
 Earth's surface commonly varies between a few miles up to 
 80 miles or more ; their absolute diameter between perhaps 
 50 yards and 2 miles; and their velocity between 2 miles and 
 40 miles per second. The foregoing figures are actual results 
 in the case of particular fireballs. It may be remarked, how- 
 ever, that one is apt to exaggerate estimates of diameter, and 
 also of velocity, measured in the first instance as so many 
 degrees in the sky in so many minutes. The only cases in 
 which trustworthy results can be assured are in the instances, 
 naturally very rare, in which two trained observers in widely 
 separated parts of the country may each have the good 
 fortune to see the same fireball start on its career and be 
 able to follow it to the end. There are a few instances of this 
 on record, and the calculated results may in such cases be, to 
 a large extent, depended upon. 
 
 There must now be mentioned a matter connected with 
 celestial mechanics, which might with equal propriety be 
 attached to the chapter on comets or to this one on meteors. 
 I allude to the modern discovery of the association between 
 certain comets and certain displays of luminous meteors. 
 This may now be regarded as a clearly ascertained fact, though 
 it is far from easy to pronounce dogmatically on the circum- 
 stances so far as they are yet known. The simple fact, concisely 
 expressed, is that. there are meteor-showers revolving round the 
 Sun in orbits so closely resembling the orbits of certain comets 
 that we are driven to the startling conclusion that some of the 
 recognised meteor-showers are either off-shoots from comets 
 or are the actual materials of disintegrated comets. There is, 
 at any rate, one instance of this which is hardly open to serious 
 
1 86 SHOOTING-STARS. 
 
 question. The former well-known Comet of Biela has abso- 
 lutely disappeared, but there exists a swarm of meteors 
 travelling round the Sun which present themselves every 
 November, radiating from the constellation Andromeda, 
 which pursue a path practically identical with that which used 
 to be followed by Biela's Comet, so long as we knew it as a 
 comet ; and the conclusion is inevitable that the comet, as it 
 originally was, has been broken up and become a swarm of 
 meteors. 
 
 Whilst it is obvious that such a conclusion sets us all 
 thinking, it is not easy to say how far, or in what direction, 
 our thoughts ought to go. 
 
 The following is a summary statement of the association of 
 certain comets with certain meteor-showers : 
 
 Comet. 
 
 Tebbutt's 
 Halley's 
 1862 (iii.) 
 Tempel's 1866 (i.) 
 Biela's 
 
 Meteors. 
 Lyrids 
 Aquarids 
 Perseids 
 Leonids 
 Andromedes 
 
 Radiant Point. 
 
 Lyra 
 Aquarius 
 Perseus 
 Leo 
 Andromeda 
 
 Date. 
 
 April 20 
 May 1-6 
 Aug. 10-12 
 Nov. 13 
 Nov. 27 
 
 The circumstances of Tempel's Comet are specially remark- 
 able, and, as they have been investigated very fully by Kirk- 
 wood, some details will interest the reader. It has already been 
 stated in an earlier part of this chapter that the Leonid meteors 
 first attracted the attention of a scientific observer in 1799, and 
 that at a subsequent date it was clearly ascertained that the 
 shooting-stars seen in 1799, 1833, and 1866 were periodic 
 manifestations of the same shower ; but it was not till near the 
 last-named date that the association of a certain comet with this 
 shower became fully understood. 
 
 The subject was started in its first developement by the dis- 
 covery, on December 19, 1865, of a small comet by Tempel, then 
 at Marseilles. It was generally observed for 7 weeks, and, 
 although not a very conspicuous object, its relations to the 
 
THE LEONID METEORS. 
 
 i8 7 
 
 Earth and Uranus may be said to have given it an importance 
 surpassed by 
 very few 
 comets. The 
 final computa- 
 tion of its 
 orbit showed 
 that it was a 
 period ic al 
 comet revolv- 
 ing round the 
 Sun in 33'28 
 years. This 
 comparatively 
 short period 
 led to cata- 
 1 ogue s of 
 comets being 
 searched, and 
 it was found 
 that, reckon- 
 ing backwards 
 33 '28 years a 
 good many 
 times, there 
 were coinci- 
 dences (with 
 breaks) back 
 to the year 
 465 B.C. of 
 comets which 
 might be 
 identical. If 
 one can 
 assume that such a date may be safely taken as a terminus a 
 
 Fig. 257. Orbit of the Leonids of Nov. 13 and 
 of the Comet of 1866 (i) relatively to the 
 Orbit of Certain Planets. 
 
 Points on the orbit opposite to the letters A, B, C are the 
 positions of the 3 detached swarms, according to Kirkwood 
 
1 88 SHOOTING-STARS. 
 
 quo, we have, as a result, 72 periods of 33*28 years down to 
 A.D. 1366. A comet in 1366 is regarded as another absolutely 
 certain terminus a quo for later centuries. From 1366 to 1866 
 is 499*3 years, or fifteen periods of 33*28 years. 
 
 Professor H. A. Newton, working on independent lines, traced 
 back the great showers of 1866 and 1833 to A.D. 902. He 
 showed that there were five possible periods for the revolution 
 of the swarm round the Sun, namely, 180 days, 185 days, 355 
 days, 377 days, or 33^ years. This important uncertainty was, 
 however, first definitely solved by Professor}. C. Adams in 1867, 
 who, by working on Newton's labours, found definitely that the 
 periodic time was about 33*25 years. 
 
 The conclusion that Tempel's Comet and the great meteoric 
 swarm of 1866 and previous dates move in the same orbit, and 
 that the swarm of meteors was in fact derived from the comet, 
 was reached almost simultaneously by Peters, Le Verrier, and 
 Schiaparelli ; but the matter was carried a good deal farther by 
 Kirkwood, who found very clear proofs not only of a second, but 
 also of a third cluster belonging to the same family, moving in 
 orbits clearly identical in form with those of the comet and the 
 1866 meteors. It need hardly be pointed out what an interest- 
 ing series of coincidences have thus been brought to light. I 
 have not space to go into further details, but Kirkwood gathered 
 up from a long series of observations of meteor-showers, spread 
 over several centuries in each case, materials which furnished 
 him with the information on which he based his conclusions. 
 
 We will pass now to the consideration of aerolites, and this 
 brings us face to face with the important questions which I 
 have not yet broached : What is a shooting-star ? What is a 
 fireball ? Whence comes an aerolite ? I think it must be 
 said that these questions must be answered together, and that 
 
AEROLITES. 189 
 
 the conjoint answer must be that all these bodies are, or have 
 been, masses of solid matter floating about in space, coming 
 from whence we know not, but which, when they reach the 
 Earth's atmosphere at about 80 miles above the Earth's surface, 
 (i) take fire and fizzle away, or (2) take fire and burst, or 
 (3) fall to the ground as solid masses of stony matter, which are 
 either in their original form and of their original size, or which, 
 when we see them on the ground, are the broken-up fragments 
 of some larger mass, which has become disintegrated, either in 
 the upper regions of our atmosphere or farther off in Space. 
 
 With aerolites we rather pass from the domain of astronomy 
 into that of chemistry, geology, mineralogy, and geography, and 
 therefore my treatment of the subject in these pages must be 
 brought into somewhat narrow limits. The crucial fact which 
 we have to bear in mind is that now and again stony or semi- 
 metallic masses, composed of many diverse materials, fall on the 
 Earth, from whence coming we know not. 
 
 The number of such falls, recognised as such, has now reached 
 a considerable total, and covers a large field both in time and 
 area ; that is to say, that instances of such falls have been 
 recorded at many dates, beginning with more than 2000 years 
 ago ; and the produce of such falls may be found in every part 
 of the habitable globe. But many aerolites have been trans- 
 ported by the hand of man from the place where they fell to 
 some neighbouring or distant public museum. Hence it comes 
 about that specimens of aerolites are to be found alike in the 
 British Museum and in many other public museums in different 
 parts of the world. Naturally, most of the aerolites which have 
 been found were in the stone-cold condition, and their extra- 
 terrestrial origin had to be inferred from analogy and chemical 
 analysis ; but a few cases are on record in which the aerolite 
 was seen to fall, and was examined by an eye-witness and 
 found to be still warm. The following is a typical case in point. 
 On April 20, 1876, a mass of meteoric iron weighing about 
 7 Ibs. fell at Rowton, in Shropshire. We are told that shortly 
 
190 SHOOTING-STARS. 
 
 before 4 p.m. a sound like that of thunder, followed by reports 
 as of cannon, shook the air, and was heard during rain-showers 
 for many miles round in that neighbourhood. No fireball was 
 observed. The iron was found about an hour afterwards in a 
 meadow, where it had sunk into the earth to a depth of 18 
 inches. When dug out it was still quite hot. 
 
 In the foregoing case the material was metallic, more or less. 
 But in other cases, and the majority, the material has been 
 generally stone of sorts, either a conglomerate mass of mixed 
 composition or a mass somewhat basaltic in its nature. It is 
 obvious that opportunities for actually observing the fall of an 
 aerolite are few and far between, and that the most which we 
 can do is to study their appearance and investigate their 
 chemical composition in the light of the facts gathered up for 
 us as regards the time and place of their fall. 
 
CHAPTER XI. 
 THE STARS. 
 
 The apparent movement of the stars on a starlight night. The stars 
 in magnitudes. Diurnal movement of the Earth. Its conse- 
 quences. The stars visible vary with the latitude. The expression 
 "fixed stars." Stars that are visible to the naked eye. The 
 identification of the stars. Bayer's system of lettering stars. 
 Flamstecd's numbers. Sir J. HerscheVs striking remarks. Total 
 number of naked-eye stars. Amount of star-light. Twinkling. 
 Double stars. Binary stars. Coloured stars. Complementary 
 colours. Triple and multiple stars. Variable stars. Notable 
 variable stars. Temporary stars. Tycho Brake's Star. Recent 
 temporary stars. 
 
 WE are now starting on what is obviously a very large subject, 
 and one which has numerous ramifications, and I propose to 
 treat the sequence of the different branches somewhat in the 
 order in which the student of the stars would be likely to 
 approach the subject, first of all as an observer using only his 
 eyes, and then proceeding to employ an opera-glass, a small 
 telescope, and a larger telescope all in succession. The 
 dominant idea which will run as a thread through this and the 
 later chapters dealing with the constellations will be that the 
 reader will wish to make himself acquainted with the actual 
 geography (though this is not the proper word ! ) of the heavens, 
 with the view of knowing what interesting objects to look for 
 and where to find them. 
 
 1 Jt should be " uranography," from Oupai/os heaven, and ypa^w, I write. 
 191 
 
192 THE STARS. 
 
 I will now proceed to deal with a variety of general con- 
 siderations relating to the stars, individually and collectively, 
 including their apparent movements through the different 
 seasons of the year. Some of these topics may seem to be dry, 
 but clear conceptions as to many of them are of prime im- 
 portance. 
 
 Everybody, I suppose, knows that the Earth turns on its axis 
 as a wheel turns on its axle. The visible consequences of this 
 act should be thoroughly realised, and this will best be done 
 by the reader taking his station on a clear, starlight night in 
 some high and fairly open position facing the N., but with 
 a tolerably wide range of view all round. Let him, in the 
 first instance, try and fix in his mind the grouping of the stars 
 in the W., somewhere about the point where the Sun has 
 set. Next let him turn his eyes and take note of the 
 stars immediately overhead. Finally, let him examine the 
 stars due E. of his position, and fix in his mind their general 
 appearance. 
 
 Having taken stock, as it were, of these three portions of 
 the heavens, let him go indoors for an hour, or, better still, for 
 a couple of hours, and then come out again and refresh his 
 memory by trying to regain the conceptions of two hours ago ; 
 and he will find some difficulty in doing so. Several of the 
 principal stars which he had previously noted as low down in 
 the western horizon will have disappeared. Those which had 
 been overhead will have appreciably moved on towards the 
 W., whilst, when he directs his eyes to the eastern horizon, 
 he will discover a fresh set of stars which he had not seen 
 before, those which he had seen having visibly risen higher up 
 towards the zenith. 
 
 If, instead of coming out a second time the same evening, the 
 reader had postponed for a week his second inspection of the 
 heavens, he would have noticed very material changes in 
 the aspect of affairs. Every group of stars would have moved 
 on ; those which had been in the W. would have dis- 
 
APPARENT MOVEMENTS OF THE STARS. 
 
 193 
 
 appeared, and a new assortment would have started up in the 
 east. If, instead of resuming his work in a week, he had 
 waited a month, the changes in the aspect of the sky would 
 have been still more radically different ; and, to cut a long story 
 short, if he had prolonged his study of the sky by only looking 
 at it once a month for 12 months, he would, at the end of 
 the twelfth month, have seen all the stars, and in identically 
 
 Fig. 259. Apparent Changes in a Group of Stars in the Course 
 of 12 hours between Rising and Setting. 
 
 the same positions in which they had been on the night of his 
 first view one year previously. Otherwise expressed, what 
 would have happened would have been this : he would have 
 had under notice all the constellations, and therefore all 
 the stars, which under any possible circumstances could be 
 seen in the latitude of his place of observation. 
 This mention of the word " latitude " opens up a subsidiary 
 13 
 
194 THE STARS. 
 
 matter of great practical importance. In consequence of the 
 axis of the Earth being inclined about 23 to the Ecliptic (the 
 apparent annual path of the Sun), the whole body of stars need 
 to be considered under three heads : 
 
 1. Those in the neighbourhood of the Poles which never go 
 below the horizon, but which are visible on every clear night 
 throughout the year. 
 
 2. Those which I have first described, which come into view 
 and pass out of view, being obliterated in turn by the Sun's 
 rays as the Sun in its annual course passes through the signs 
 of the Zodiac ; and, 
 
 3. Those which lie towards the S., including those which 
 gather round the South Pole, all of which are perpetually 
 concealed from the observer in a given northern latitude. 
 
 The foregoing statement respecting the visibility of particular 
 constellations and stars needs a twofold extension. In the 
 first place, if the observer in the first-mentioned latitude sup- 
 pose we say London travels to the North of Scotland, he will 
 lose some of the stars which, in the latitude of London, he 
 glimpsed when they were passing along his extreme southern 
 horizon. 
 
 If, on the other hand, he moves away from London to the 
 extreme South of France, he will find, travelling along his 
 southern horizon, stars of the existence of which he had 
 obtained no knowledge when at his original station in the 
 latitude of London. If he should proceed farther S., right 
 away 6000 miles to the Cape of Good Hope, or on to Australia, 
 he will come face to face with an entire reversal of everything 
 which he had seen when in the latitude of London. The 
 North Pole, the Great Bear, the Little Bear, and all the 
 constellations in their neighbourhood would have disappeared 
 irrecoverably. The constellations which had passed over the 
 zenith in London will be low down in the northern horizon, 
 the previously visible North Pole, and its Pole-star, will have 
 disappeared, and been replaced by another Pole, and another 
 
THE STARS AS SEEN IN DIFFERENT LATITUDES. 195 
 
 Pole-star, 1 and an entirely new set of constellations will pass 
 over the zenith at the Cape and in Australia, so that in point 
 of fact the aspect of the nocturnal heavens will have become 
 completely revolutionised. 
 
 The statement just made as regards the consequences of 
 an observer transferring himself from London, in the North 
 latitude of 51, to a place in the corresponding latitude in the 
 Southern Hemisphere, which would be somewhat to the S. 
 of New Zealand, may be otherwise expressed thus : that the 
 stars which are within the "circle of perpetual apparition," 
 otherwise known as " circumpolar stars," and are therefore 
 perpetually visible in England, will be perpetually invisible in 
 New Zealand, and the stars which are perpetually out of view 
 in England will be perpetually in view in New Zealand. It 
 must be understood that this statement, to be literally true in 
 substance, depends on identical latitudes being compared, and 
 that the latitude of 51, which is assumed to be that of London, 
 finds its literal counterpart not actually in New Zealand, but 
 a little distance S. of the most southerly point of New 
 Zealand. 
 
 I hope that the foregoing statements as to the changes in 
 the aspects of the heavens which will be noticed by an observer 
 watching the stars from night to night throughout a period of 
 one year will be sufficiently intelligible ; and that what is meant 
 is that the whole vault of heaven with its myriads of fixed stars 
 is in constant movement as an unchanging whole. But this 
 presentation of the matter, though convenient and indeed 
 necessary to convey general ideas, is not quite literally true ; 
 it is one of those conventional untruths which are often useful 
 in astronomy as a preliminary to pave the way to precise 
 
 1 Whilst the Northern Hemisphere has, as its representative Pole-star, a 
 fairly bright star (a Ursa Minoris), which is very close to the exact polar 
 point, it is to be regretted that the South Pole has no sufficient Pole-star, the 
 nearest star to the South Pole (<r Octantis) being only of magnitude 5, and 
 some distance from the polar point." 
 
196 THE STARS. 
 
 accuracy. The term " fixed stars " is so old and so universally 
 used that I think it may be said to deceive nobody. Moreover, 
 it is perfectly well known that certain objects which are often 
 colloquially included under the name of " stars " are not fixed, 
 but wander hither and thither, and are known as "planets," 
 which very word itself implies that they do not occupy fixed 
 positions. 1 Furthermore, precise modern observations, con- 
 ducted with special skill and care, have brought to light the 
 fact that a very considerable number of stars are endued with 
 actual proper motion of their own, so that they move relatively 
 to one another, though by amounts which are entirely beyond 
 the grasp of the naked eye. 
 
 The stars being of different apparent size, which for our 
 present purpose means brilliancy, have been classified in magni- 
 tudes which range from the 1st to the i8th, though the higher 
 figures which one meets with in various astronomical publica- 
 tions are very uncertain and fanciful. 
 
 It is usually considered that the range of naked-eye vision ends 
 with the 6th magnitude inclusive ; but with many persons the 
 limit must be put at 5^, whilst with a few other people it may 
 be extended to 6|. Beyond this the range goes to 7, 8, 9, 10, 
 n, and 12; and there all accurate values may be deemed to 
 cease, though one often comes upon higher figures. All the 
 recognised figures began with eye estimations in bygone times. 
 It is obvious that this is a most unsatisfactory and unbusiness- 
 like way of estimating the brightness of a star, and, though 
 organised photometric methods have often been proposed, they 
 have only, up till now, been carried out to a limited extent. 
 The observers at Harvard College, United States, have pub- 
 lished catalogues of naked-eye stars estimated in brightness 
 by means of an instrument called a photometer, 2 and the value 
 of their labours is very great indeed. 
 
 Independently of instrumental values of star-magnitudes, it 
 
 1 Gr. 7r\avrjr>)s, a wanderer. 
 
 " Gr. $u>s, light, and pirpov, a measure. 
 
THE CLASSIFICATION OF STARS. 197 
 
 is customary to subdivide magnitudes decimally from o to 9, 
 which gives an air of exactitude to the figures assigned, which 
 can only be regarded as, in many cases, a sham. 
 
 When we come to deal with the stars in detail it will be seen 
 that other classifications besides those depending on brilliancy 
 have to be resorted to ; so that we shall have to put into 
 separate sections " coloured stars," " double stars," " temporary 
 stars," " variable stars," and " moving stars." Next will follow, 
 as a complement to double stars, " triple," " quadruple," and 
 " multiple stars," clusters of stars, and nebulae, and last, but 
 not least, the Milky Way. But, before entering on such details, 
 there are several other matters which must be brought under 
 the notice of the reader. 
 
 Postponing a consideration of the constellations to the chapter 
 specially dedicated to them it will yet be convenient in this 
 chapter to say something about the identification of the stars. 
 In early times, after a targe number of the important constella- 
 tions had been named (and the origin of most of these names 
 is lost in antiquity), it soon came into men's minds that some 
 means of distinguishing one star from another in the same 
 constellation was urgently necessary. This was a matter taken 
 in hand by the Arabian astronomers during the centuries 
 following the Christian era. Most of the names of particular 
 stars now in use (Aldebaran, Altair, etc.) are of Arabic origin, 
 with additions of Greek and Latin origin (Arcturus, Spica 
 Virginis, etc.). These names served their purpose in a certain 
 way, and for a certain time, but the need of more precise names 
 was soon felt, hence Aldebaran came to be called Oculus Tauri, 
 the "eye of the bull/ 5 a phrase supposed to give some indica- 
 tion of where the star was to be found. 
 
 It requires no great amount of acuteness to realise that 
 such methods to indicate stars as these were so rough and 
 vague as to be practically useless ; but a very marked ad- 
 vance in the direction of scientific exactness was made in 
 1603 by a German astronomer named Bayer, who in that 
 
198 THE STARS. 
 
 year published the first Celestial Atlas, the title of which 
 was Vranoinetria, Omnium Asterismorum continens Sche- 
 mata Novd Methodo delineata. In this work the stars of 
 each constellation were distinguished by having attached 
 to them the letters of the Greek alphabet, and these have 
 been used ever since. It would seem that Bayer started 
 with the idea that he would label the stars in the order of 
 brightness from a and /3, and so downwards as far as might be 
 necessary till the alphabet was exhausted. The common idea 
 is that the order of the alphabet, as we know it, did and does 
 represent the order of the stars so estimated ; and occasionally 
 it has been argued that the brightness of a star must have 
 varied, because it does not occupy its proper position in bright- 
 ness according to its position in the Greek alphabet. There 
 is, however, no doubt that such an argument is worthless, and 
 that the idea of accurate sequence cannot be carried further 
 than to say that the brightest star in every constellation always 
 had a allotted to it, and perhaps the second brightest ft but 
 that all the rest followed somewhat, but perhaps not altogether, 
 at haphazard. 
 
 The next worker in this field was our own John Flamsteed, 
 once Astronomer Royal. He prepared and in 1725 published 
 his Catalogus Britannicus, which contained 3310 stars 
 observed at Greenwich, and reduced to 1690, all the stars 
 of which were numbered by his modern editor, Francis Baily, 
 from No. i onwards in each constellation. Flamsteed's num- 
 bers are still in general use, and they, together with Bayer's 
 Greek letters, are to be found engraved in almost every star- 
 atlas in existence. When Bayer's letters are used they are 
 prefixed to the genitive case of the Latin name of the con- 
 stellation, thus : a Ursae Majoris, /3 Canis Minoris, and so on. 
 In addition to Bayer's Greek letters and Flamsteed's numbers 
 there are a few stars indicated by Roman letters. The use 
 of these letters, but to a very limited extent, was really started 
 before Bayer's time by an Italian, Piccolomini of Siena, but 
 
SIR J. HERSCHEL ON THE STARS GENERALLY. 199 
 
 his use of them was limited. A long time elapsed after the 
 invention of the telescope, and the commencement of methodical 
 observations of stars as regards their exact places in the 
 heavens, before the constellations and stars of the Southern 
 Hemisphere were submitted to critical instrumental measure- 
 ment. 
 
 This did not come about till Lacaille published, in 1763, his 
 Cesium Australe Stelliferum, which contains 1943 southern 
 Stars, observed by him at the Cape. Lacaille had the whole 
 Southern Hemisphere to himself, so to speak, and he turned 
 his opportunities to account not only by observing its stars but 
 also by attaching letters, Greek and Roman, to them, at the 
 same time creating 14 new southern constellations. In the 
 particular case of the constellation Argo, one of vast extent 
 and with many large stars, Lacaille got into a good deal of 
 difficulty in the lettering that is to say in finding letters for the 
 1 80 stars to which he deemed it desirable to attach letters. 
 Thus it came about that, besides using up the Greek alphabet, 
 he employed the whole of the Roman alphabet, both in capital 
 and small letters, repeating indeed each several times, and so, 
 of course, paving the way for a good deal of confusion. 
 
 Sir John Herschel once made some remarks on the subject 
 of the stars which are so very striking as to deserve quotation, 
 the more so as they help to indicate the utilitarian side of 
 astronomy, and moreover constitute what the French call 
 politely a dementi to the absurd statement once made by the 
 late Sir George Cornwall Lewis that astronomy is only a science 
 of " pure curiosity." These are Sir John's words : 
 
 " The stars are the land-marks of the universe, and, amidst 
 the endless and complicated fluctuations of our system, seem 
 placed by its Creator as guides and records, not merely to 
 elevate our minds by the contemplation of what is vast, but to 
 teach us to direct our actions by reference to what is immutable 
 in His works. It is indeed hardly possible to over-appreciate 
 their value in this point of view. Every well-determined star, 
 
200 THE STARS. 
 
 from the moment its place is registered, becomes to the 
 astronomer, the geographer, the navigator, the surveyor, a 
 point of departure which can never deceive or fail him, the 
 same for ever and in all places, of a delicacy so extreme as 
 to be a test for every instrument yet invented by man, yet 
 equally adapted for the most ordinary purposes ; as available 
 for regulating a town clock as for conducting a navy to the 
 Indies ; as effective for mapping down the intricacies of a 
 petty barony as for adjusting the boundaries of transatlantic 
 empires. When once its place has been thoroughly ascertained 
 and carefully recorded, the brazen circle on which that useful 
 work was done may moulder, the marble pillar totter on its base, 
 and the astronomer himself survive only in the gratitude of his 
 posterity ; but the record remains, and transfuses all its own 
 exactness into every determination which takes it for a ground- 
 work, giving to inferior instruments, nay, even to temporary 
 contrivances, and to the observations of a few weeks or days, all 
 the precision attained originally at the cost of so much time, 
 labour, and expense." 
 
 As regards the number of the stars there is great mis- 
 apprehension in the minds of many people. One's natural 
 impulse is to exaggerate the numbers. Bearing in mind the 
 difficulty of drawing precise lines of demarcation between 
 the different magnitudes (the difference between the ist and 
 the 2nd not excepted), the following may be stated as 
 approximately the numbers for the several magnitudes : 
 
 Magnitudes. No. of Stars. 
 
 1st . , . . . . 21 
 
 2nd . ... . . . 65 
 
 3rd . ... . . - 190 
 
 4th . <v . .... -425 
 
 5th . . . . . . .1100 
 
 6th . 3200 
 
 Below the 6th magnitude the uncertainties are too great to 
 make exact estimates justifiable, and it is not safe to say more 
 than that the visible stars, from the ist magnitude down to the 
 9th inclusive, have been estimated by experienced observers 
 
STATISTICS OF THE STARS. 2OI 
 
 to be about' 130,000 in number, though Argelander raised this 
 figure to 200,000. 
 
 It is generally considered that the total number of stars 
 visible to the naked eye in England on any given night must 
 not be put higher than 2500, whilst the grand total of all the 
 stars which could be counted in England, all the months 
 lumped together, may be said to be no more than about 4000, 
 though Heis, of Miinster, turned this into 5000. 
 
 Such statistics as these are not very profitable, because 
 different enumerators are certain to do their work of taking 
 a census of the stars on different principles : still, the subject 
 could not be entirely passed over. 
 
 A question which has been raised, though it can hardly be 
 said to have been settled, on any sure basis, is the question 
 whether the stars, or any of them, transmit any measurable 
 quantity of heat. Experiments carried out many years ago at 
 the Greenwich Observatory and elsewhere seem to suggest an 
 affirmative answer, but when I quote one of the results in the 
 form in which it was announced, scepticism on the subject will 
 not be deemed unreasonable. Here is this result : That 
 Arcturus, at an altitude of 25 above the horizon, was found to 
 emit the same amount of heat as that which would be felt from 
 3 cubic inches of boiling water at a distance of 400 yards ! An 
 analogous difficulty I had almost said impossibility arises in 
 connection with the question, What is the amount of light 
 given out by the stars ? All attempts to express this in figures 
 seem to me perfectly futile, and that we cannot safely do more 
 than say that, contrasting a starless night with a night on which 
 the stars are shining brightly, there is in the latter case a 
 sensation of less darkness than in the former case. Beyond 
 this I do not deem it safe to particularise. 
 
 Fabry, at Marseilles, published in 1910 the results of certain 
 efforts made by him by way of developing previous attempts by 
 Nevvcomb, Burns, and Yntema, a Dutchman, to determine 
 the intrinsic brightness of the sky so far as star-light was 
 
202 THE STARS. 
 
 concerned: It need hardly be said that the task to be per- 
 formed proved a very difficult one and the results very 
 contradictory all round ; so much so that I hesitate to attempt 
 to summarise them, beyond saying, what is an evident 
 truism, that the stars collectively do afford some light to the 
 Earth. 
 
 We must not pass away from the consideration of the stars 
 as isolated or single objects without saying something on the 
 interesting and time-honoured question of their twinkling. 
 This optical phenomenon came before all of us in our earliest 
 years. Who has forgotten : 
 
 "Twinkle, twinkle, little star; 
 How I wonder what you are ! 
 Up above the world so high, 
 Like a diamond in the sky"? 
 
 This has been in part replaced by the advance of modern 
 science, and accordingly we have the following revised version 
 in circulation : 
 
 "Twinkle, twinkle, little star; 
 Now I've found out what you are, 
 When unto the midnight sky 
 I the spectroscope apply." 
 
 Familiar as the phenomenon is to all of us, full scientific 
 explanations of it are lacking. In its effects it is evidently 
 largely dependent upon the condition of the Earth's atmosphere, 
 the varying influence of which undoubtedly affects the extent 
 of the twinkling noticed on any given night. The weather 
 indications which twinkling bespeaks seem uncertain when it is 
 a question of excessive twinkling, which may indicate fine 
 weather or the approach of weather of the contrary character ; 
 but it seems quite certain that the absence of twinkling (that is 
 to say, if the stars are dull and devoid of rays) renders the 
 approach of rain a certainty. Bright stars twinkle much more 
 
TWINKLING OF THE STARS. 203 
 
 than faint ones ; indeed, it may be said that faint stars do not 
 twinkle at all. Again, stars low down near the horizon twinkle 
 more than those high up towards the zenith ; and an observer 
 in a low-lying position on the Earth will notice the twinkling to 
 be more marked than when he looks at the same stars from a 
 mountainous or considerably elevated level above the sur- 
 rounding country in other words sees the stars through a 
 comparatively rarefied atmosphere. These facts accentuate 
 the certainty that twinkling is a matter largely, one might 
 perhaps almost say wholly, dependent on atmospheric con- 
 ditions. It has been suggested, however, that this question of 
 the density or rarefaction of the air, dependent on a star's 
 position above the horizon, must not be pushed too far because 
 (as is supposed) several of the principal fixed stars, presumably 
 on account of the nature and peculiarity of their light, vary 
 considerably in their display of twinkling, independently of 
 their position in the heavens. For instance, Procyon (a Canis 
 Minoris) and Arcturus (a Bootis) twinkle much less, under all 
 circumstances, than Vega (a Lyrae), a notable bluish-white star. 
 A French observer, Dufour, has laid it down that red stars 
 twinkle less than white ones and that twinkling is more 
 visible during twilight than later on. 
 
 The subject of twinkling was very exhaustively studied by the 
 late C. Montigny, an amateur, who lived at Brussels, where 
 I had many interesting conversations with him in 188 . 
 He arrived at some very striking conclusions. He found 
 that twinkling is more pronounced when rainy weather is 
 impending, and also more pronounced in winter than in summer. 
 Dry weather in spring and autumn stands on about the same 
 footing, but autumnal wet weather developes the phenomenon 
 in a much more marked manner than does spring wet weather. 
 Variations in the barometer and in the humidity of the atmo- 
 sphere, as indicated by the hygrometer, also affect the amount of 
 twinkling ; it is also more developed when a rainy period likely 
 to last two or three days is approaching, than merely before a 
 
204 THE STARS. 
 
 single casual rainy day ; it also varies with the aggregate total 
 rainfall of a group of days, being greater as the rainfall is 
 greater, suddenly and considerably decreasing directly the rain 
 has passed away. 
 
 Montigny's observations and conclusions were not based on 
 crude, haphazard eye-observations, but on an instrument of his 
 own invention, which he called a scintilometer, using the French 
 word for twinkling as the basis of the name of his appliance. 
 He found the number of scintillations (angltcc, twinkles) 
 observable per second to vary from a minimum of 50 during 
 June to July to 97 in January and 101 in February, increasing 
 or decreasing month by month in regular gradation. He also 
 found that a display of Aurora Borealis exercised a marked 
 influence in increasing the twinkling. But this was not all in 
 regard to his discoveries. It came into his head that possibly 
 the different classes of stars as classed by Secchi with respect 
 to their spectra might yield some definite results in regard to 
 twinkling; and he was not disappointed. Anticipating here 
 what belongs to a later part of this volume, a proper account of 
 Secchi's classes of stars, I may state that Montigny, as the result 
 of some hundreds of observations of 41 bright stars belonging 
 to Secchi's first 3 classes, was led to the following conclu- 
 sions : that stars of the first class yielded an average number of 
 86 scintillations per second, stars of the second class 69, and 
 stars of the third class only 56. The more perfectly any star 
 possesses the distinguishing characteristics of its class the more 
 nearly does the number of its scintillations agree with the law 
 indicated by the above statement. This law may be stated thus : 
 The more considerably the spectrum of a star is interrupted 
 by dark lines, the less frequent are its scintillations ; from 
 which it follows that on the characteristic of each star depends 
 its twinkling, both as regards its frequency and the colours 
 which it displays. 
 
 Sufficient has now been said by way of treating the stars as 
 isolated objects in the heavens, and we must now proceed to 
 
DOUBLE STARS. 
 
 205 
 
 consider the stars in combination, beginning 
 with pairs of stars, and leading up to clusters 
 of indescribable multitudes. I pass over such 
 recundite matters as the " proper motions " of 
 stars, " star-drift," and the " motion of the Solar 
 System in space," as involving difficult technical 
 details not likely to interest the readers for 
 whom this volume is primarily intended. 
 
 DOUBLE STARS. 
 
 A very large number of stars, including some 
 of the largest and some of the smallest visible, 
 though they appear to the naked eye, or through 
 an opera-glass or a small telescope, to be single 
 stars, yet, with increased optical assistance, are 
 found to consist of two stars so close together 
 as previously to have been regarded as only 
 one star. Other stars seeming to be single are 
 eventually found to comprise three stars, and so 
 on, ifour stars, or five stars, until the word 
 "multiple" has to be used. We will start 
 with a common form of double star, though in 
 numerous cases greatly increased optical assist- 
 ance shows that one or other member of a pair, 
 regarded only as a pair, is itself double again. 
 Up to the time of Sir W. Herschel very 
 'few double stars were known. His powerful 
 telescopes enabled him to convert 500 stars 
 apparently single into doubles ; and now the re- 
 searches and perseverance of modern observers 
 have resulted in the number of recognised double 
 stars being increased to many thousands. 
 
 The mere fact of looking at a star and 
 finding it in a small telescope to be single, 
 
 Fig. 260. 
 Two Stars 
 at Different 
 Distances seen 
 as a " Double 
 Star." 
 
206 THE STARS. 
 
 whilst a larger telescope, or more power on the small one, 
 reveals its duplicity, though a thing interesting in itself, 
 falls far short of the great interest which attaches to many of 
 these objects after prolonged study of them. Herschel at 
 first merely supposed that he was looking at 2 stars either 
 stationary side by side at the same distance from the Earth 
 or at 2 stars in nearly the same line of sight at distances 
 altogether different. The annexed diagram (Fig. 260) will make 
 clear what is involved in this simple statement regarding a star 
 only optically double. Herschel, however, was led by the force 
 of circumstances into a discovery which both astonished and 
 captivated him. In the early stages of his work as a double- 
 star observer he recorded the angular position of all his double 
 stars with respect to the N. and S. points of the heavens, and 
 their distances from one another. He continued observations of 
 this character for the sole purpose of trying to discover whether 
 observations at different periods of the year gave indications 
 of his stars being subject to displacement by way of parallax 
 in consequence of the Earth's annual motion round the Sun. 
 
 Instead, however, of obtaining any information to help him 
 as regards parallax, he found in a very large number of cases 
 that these pairs of stars were experiencing relative change, and 
 that their distances were varying ; as also the angle with the 
 meridian of a line joining the centres of the 2 stars. In other 
 words, he found that there were in existence systems consist- 
 ing of 2 stars revolving about each other in elliptic orbits, 
 and evidently linked together. The interest attaching to this 
 discovery is of a twofold nature. JjuirST'of all, there was the 
 unforeseen and captivating novelty of it, and then there was the 
 important fact that it was ultimately found that the Newtonian 
 Law of Gravitation was in operation far beyond the confines of 
 the solar system to which it had been previously supposed to be 
 limited. 
 
 The actual application of the law to Herschel's discoveries 
 did not take place till many years after those discoveries^ when 
 
PLOTTING DOUBLE STARS MEASUREMENTS. 2C7 
 
 Savary, in 1830, computed an orbit for the star Ursa Majoris 
 which is now recognised as a binary, the smaller star of 
 which steadily circulates round the larger one in a period of 
 
 Fig. 261. Diagram for sketching of the Corona in Total 
 Eclipses of the Sun. 
 
 Devised by E. J . Stone, and available for plotting measurements of 
 Double Stars. 
 
 about 60 years. This star may be well commended to the 
 notice of amateurs for the reason that both components are 
 large, the larger one being of magnitude 4, and the smaller one 
 
208 THE STARS. 
 
 of magnitude 5^, and the distance between them generally 
 being about 2" of arc, more or less. Herschel made his dis- 
 covery known in a memorable paper presented to the Royal 
 Society in 1802. The number of stars which, after about 25 
 years' study, he found to be endued with orbital motion was 
 no more than 50, but since his day an immense amount of 
 time and labour has been bestowed on that class of star, and the 
 assured binaries are now to be numbered by hundreds, not to say 
 thousands, if we takecount of those which are suspectedof motion. 
 
 Ursa Majoris goes through its changes in a comparatively 
 short period of time that is to say, there are not many 
 stars whose periods are shorter than 60 years ; but there 
 are a great number whose certain periods run into hundreds 
 of years, and therefore with many of them prolonged observa- 
 tions, spread over a long expanse of years, will have to be 
 carried out before the certainty of their movements and the 
 precise details thereof can be established. HerschePs discoveries 
 were taken up and turned to account by F. G. W. Struve, who 
 in 1837 published a great book containing measures of 3112 
 double stars. After him came Dawes, Secchi, Seabroke, and 
 many others ; but the greatest living observer of double stars is 
 undoubtedly the American astronomer S. W. Burnham, whose 
 zeal and industry have attained colossal proportions, but he has 
 nowadays many fellow-labourers in various parts of the world. 
 Burnham's own experiences have for obvious reasons been 
 somewhat restricted to the Northern Hemisphere with some 
 degrees of Southern Declination included ; but a great develope- 
 ment of double-star work is now proceeding at the Cape and in 
 Australia. At the Cape the lead is being taken by R. T. A. 
 Innes, the Director of the recently established Observatory at 
 Johannesburg, in the Transvaal ; and, as time goes on, we may 
 expect a large output of work from that centre. 
 
 At the end of this volume a list will be given of some of the 
 more interesting and easy double stars adapted for observation 
 by small telescopes. 
 
FIG. 262 
 
 PLATE LXXXIV 
 
 COLOURED STARS. 
 
 1. i] Cassiopeia?, yellow purple: 2. 7 Andromedae, orange, .areen ; 3. Piscium, 
 
 pale f^reen, blue : 4. < Cancri, orange, blue ; 5. <* Circtni, white, brick red : 
 
 6. e Bootis, pale orange, pale green. 
 
THE COLOURS OF STARS. 209 
 
 Many double stars exhibit the curious and beautiful pheno- 
 menon of complementary colours. In such cases the larger 
 star is usually more or less reddish or orange, and the smaller 
 one bluish-green or greenish-blue. If complementary colours 
 are noticed in the components of a double star of very unequal 
 size the circumstance may be attributed often to the effect of 
 contrast. Perhaps it may be useful to put on record here a 
 table of the complementary colours, though somewhat of a 
 digression, for the subject is one that belongs to the science of 
 optics rather than to astronomy proper. 
 
 Red is complementary to bluish-green. 
 Orange ,,. ,, sky-blue. 
 
 Yellow ., ,, violet-blue. 
 
 Greenish-yellow ,, violet. 
 Green ,, ,, pink. 
 
 The meaning of the foregoing table is this : that if any two 
 colours which are complementary, as above, are put upon a 
 rapidly revolving disc in proper proportions, when the disc is 
 set in motion on its axis a composite tint, almost white, is 
 exhibited to the spectator's eye. 
 
 As regards this question of the colours of double stars, an 
 examination made many years ago of the colours assigned, in 
 Struve's catalogue, to 596 of his bright stars, yielded the 
 following results : 375 pairs were of the same colour and 
 intensity ; 101 pairs were of the same colour but of different 
 intensity, whilst 120 pairs were of totally different colours. 
 
 As regards the colours of isolated stars not treated as 
 doubles, an examination of the heavens will lead to its being 
 noticed that single stars of a fiery red or deep orange hue are 
 quite common, but isolated blue or green stars are very rare. 
 
 In looking into the expressed opinions of observers who, 
 under various circumstances, have made statements as to the 
 colours of stars, it will be found that frequently great diversity 
 exists a diversity which is often inexplicable, and which it is 
 
210 THE STARS. 
 
 hardly permissible to put down to actual changes of colour. 
 Subject to this caution, the following stars may be named as 
 coloured according to the colours prefixed : 
 
 White Stars. a Canis Majoris, a Leonis, /3 Leonis, a Lyrae, 
 
 a Piscis Australis, a Ursas Minoris. 
 Red Stars. a Tauri. a Scorpii, a Orionis. 
 Blue Stars. a Aurigse, ft Orionis, 7 Orionis, a Canis Minoris, 
 
 a Virginis. 
 
 Green Stars. a Aquike, a Cygni. 
 Yellow Stars.* Bootis. 
 
 The amateur observer will find it interesting to compare the 
 statement of colours just given with his own ideas on the subject 
 as obtained by naked-eye observations ; and I am far from 
 saying that he will be able satisfactorily to confirm the accuracy 
 of the statements made in the foregoing table. There is really 
 only one thing which stands out conspicuously certain in 
 regard to the colours of stars, and that is, the enormous number 
 which are dotted all over the heavens which exhibit various 
 shades of colour intermediate between crimson at one end of 
 the scale and yellowish at the other. An observer who sets 
 himself the task of examining this matter for himself will 
 probably be surprised at the immense number of stars to which 
 he will be able to apply the word " orange " (in various 
 gradations). 
 
 Thus far we have been considering single stars and pairs of 
 stars, but the study of sidereal astronomy does not by any 
 means end here, because, when examining the heavens, we 
 come across, as already indeed mentioned, triple, quadruple, 
 and multiple stars ; that is to say, stars which to the naked eye 
 appear to be single, but which, with adequate optical assistance, 
 are found to be compound, as these various designations imply. 
 It is not, however, necessary to dwell on these stars, except for 
 the one purpose of stating that, besides there being pairs of 
 stars which we call " binary," because they revolve round one 
 another, and therefore are distinguishable from simple optical 
 
PLATE LXXXV 
 
 COLOURED STARS. 
 
 7. s Bootis, orange, purple ; 8. .t Coronas, white, blue ; 9. e Normae, bright 
 
 green, bright purple; 10. ct Herculis, orange, emerald green; 11. ft Cygni. 
 
 yellow, sapphire blue : 12. ff Cassiopeia?, pale green, bright blue. 
 
VARIABLE STARS. 211 
 
 double stars, which are only double in appearance, there are 
 certain triple stars which are subject to the complication that 
 there are three stars in orbital motion. These are known as 
 "ternary" systems. Here we have either 2 stars revolving 
 round one primary, or the 2 smaller stars of the trio revolving 
 round one another, and this subordinate pair jointly revolving 
 round the 3rd, which is really the first, and needs to be called 
 the primary star of the triple system. The possible complica- 
 tions to which such a condition of things brings us face to face 
 are very obvious, and I will content myself by inviting the reade/ 
 to inspect the diagrams here given without pursuing the matter 
 into further detail. 
 
 VARIABLE STARS. 
 
 Having discussed changes of colour in the stars, the question 
 of changes of brightness naturally comes next, and opens up 
 the subject which bears the recognised title of " variable stars." 
 Suspicions as to changes in the brilliancy of particular stars 
 were long current, but, save in one or two exceptional instances, 
 this branch of sidereal astronomy is of modern origin. Seem- 
 ingly, the first star to be recognised as systematically subject 
 to marked changes of brilliancy is the star which more than 
 2 centuries ago received the name of Mira Ceti a phrase 
 which becomes, when duly spread out, " Mira Stella, the 
 wonderful star in the constellation Cetus," and which supporters 
 of new-fangled pronunciation try to indicate by calling it " Meeray 
 Say tee" ! Bayer recorded the star in his Atlas of 1603, and gave 
 it the designation Omicron (o), and this is still its accepted 
 scientific title. 
 
 This star is one of the most interesting of all the known 
 variables, alike from the regularity with which it accomplishes 
 its changes and the ease with which those changes can be 
 observed by anybody. Its period is 331 days 8 h. ; in other 
 words, it reaches its greatest brightness about 12 times in 
 
212 THE STARS. 
 
 II years, when it sometimes attains the brilliancy of a star 
 of the 2nd magnitude, at which brilliancy it remains stationary 
 for about a fortnight. It then diminishes during about 3 
 months, until it sinks down to a star of magnitude 9^, or even 
 becomes totally invisible. It remains in this condition for 
 about 5 months, and then gradually recovers, during the 
 next following 3 months, its maximum brilliancy. The 
 foregoing periods and figures are only to be regarded as 
 average ones, because there is strong evidence that the changes 
 of this star are themselves subject to secondary periods of 
 change ; that is to say, that its maximum brilliancy is itself 
 periodical, and that every eleventh maximum is marked by a 
 special display of brilliancy above the average. Hence it 
 follows that, whilst the average duration of the naked-eye 
 visibility is about 18 weeks, in 1859-60 it was observed with 
 the naked eye during 21 weeks, whilst in 1868 it was so seen 
 only during 12 weeks. The variability of Mira was first noticed 
 in 1596 by D. Fabricius. 
 
 Another variable star of great interest, perhaps some would 
 think almost more so than Mira Ceti, is Algol (/3 Persei), the 
 variability of which stands second in point of date, for it seems 
 to have been first recognised by Montanari in 1669, though it 
 was not until observations by Goodricke in 1782 that its period 
 was ascertained with some degree of certainty. This is gener- 
 ally stated in the following form : The normal brightness of the 
 star is that of mag. 2j. From this it descends nearly, but not 
 quite, to mag. 4 during a period of 4h. 23m. It remains at 
 its minimum for about 20 m., then in the course of 5h. 37111. 
 it regains its normal maximum, and remains there for about 
 2d. 10 h. The time occupied in the entire series of changes 
 is 2d. 20 h. 48m. The further study which has been given 
 during recent years to the subject of variable stars has resulted 
 in the discovery of a not inconsiderable number which go 
 through their changes in periods measured by a few days, and 
 under physical circumstances akin to those which govern the 
 

 
 
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 1 8 CASSIOPEIA. 
 
 Fig. 265. 
 
 ^ Uns^ MAJORIS. 
 
 Fig. 266. Fig. 267. 
 
 Mean Light-curves of certain Variable Stars. 
 
 213 
 
214 THE STARS. 
 
 changes of Algol ; and accordingly we now speak of certain 
 stars as " stars of the Algol type " ; and by way of explanation 
 it has been suggested that a non-luminous satellite revolves 
 round the primary star and eclipses it at stated intervals. 
 
 Another variable star of great interest, which, like Algol, is 
 very handy for observers in the Northern Hemisphere, is 8 Cephei, 
 also one of Goodricke's stars, and recognised by him in 1784 
 to be a variable. Counting from minimum to minimum, its 
 period is 5 d. 8h. 47m., and its range of brilliancy from 
 mag. 3! to mag. 4f, or thereabouts. The interval between 
 maximum and maximum is unequally divided as regards the 
 minimum stage, for the time occupied in descending from 
 maximum to minimum is considerably greater than the time 
 occupied in rising from minimum to maximum. The intervals 
 are 3d. 19 h. and id. 14 h. respectively. 
 
 ,3 Lyrae is a variable which differs very much in the sequence 
 of its changes from those which have just been described, for 
 it has a double maximum and minimum within what is now 
 recognised to be its complete period of 12 d. 21 h. 53m. This 
 peculiarity misled Goodricke, who discovered the variability 
 of this star in 1784, and induced him to assign to it a period 
 of only half the true complete period as just given. The 
 changes are as follows : starting from a maximum of mag. 3^, 
 the star descends to its first minimum of mag. 4 ; then it rises 
 to maximum again, and descends to a second minimum, but 
 at this second minimum it descends lower than before, namely, 
 to mag. 4^. It is easy to see how it came about that Good- 
 ricke was misled into fixing the period at one-half its true 
 amount. Argelander ascertained that the period itself, taken 
 as a whole, is periodic ; that up to 1840 it was increasing, and 
 then began to decrease, which decrease was still in progress 
 when he made that remark in 1866. I do not find any recent 
 observations which throw light upon this point. 
 
 The foregoing stars all belong to the Northern Hemisphere, 
 but the Southern Hemisphere has in r) Argus a once naked- 
 
>OO 3OO JOO 
 
 T URS^B MAJORIS. 
 
 <5^L 
 Fig. 268. 
 
 Fig. 270. 
 
 IOO tOO JOO 
 
 tOO tOO 3QQ 
 
 S UKS^E MAJORIS. 
 
 /2 7 A3 
 
 Fig. 289. 
 
 R CAM-ELOPARD i 
 
 Fig. 271. 
 
 Mean Light-curves of certain Variable Stars. 
 
 215 
 
2l6 THE STARS. 
 
 eye variable, the uncertainties of which have puzzled several 
 generations of astronomers. Its magnitude during the past 
 150 years has been noted as 4, 2, i, 2, i, 2^, 3, 4^, 5, 6, 7, 
 7^. This last magnitude was assigned to the star in March 
 1886, and since then rj seems to have further gone down to 
 mag. 8, where it was in 1907, and probably is still. All that 
 we can infer is that it exhibits two or three maxima at intervals 
 preparatory to a great descent so as to become invisible to 
 the naked eye. Schonfeld summarily settled the question of 
 period by saying that 77 Argus has no regular period ; and there 
 is much to be said for this unsatisfactory conclusion, which 
 accords in substance with the opinion of Sir J. Herschel, ex- 
 pressed at an earlier date, that this is a star "fitfully variable 
 to an astonishing extent, and whose fluctuations are spread 
 over centuries, apparently in no settled period, and with no 
 regularity of progression." 
 
 Thus far I have been dealing with notable naked-eye stars, 
 and there are a few others of that sort which can hardly be 
 called notable. When, however, we resort to the telescope 
 and direct our attention to telescopic variable stars an enor- 
 mous number rush in upon us, many of them of great interest 
 to those who possess good eyes, patience, and telescopes of 
 adequate power. It would be monotonous and somewhat 
 beyond the scope of these pages to particularise any of these 
 stars, but the diagrams here given will convey some idea of 
 the changes which they undergo and the delicate character 
 of the observations required before safe conclusions can be 
 arrived at. 
 
 It is customary with astronomers, when they wish to indicate 
 in the most easily appreciated form variations in variable stars, 
 to resort to diagrams in which dates and magnitudes are repre- 
 sented by the ordinates and abscissas of curves. This brings 
 the changes much more readily home to a reader than mere 
 tables of figures. Figs. 264 to 275, record the changes 
 which were noted to have taken place in certain well-known 
 
00 JOO 
 
 R DRACONIS 
 " 7 - 
 
 Fig. 272. 
 
 T CEPHEJ. 
 3 
 
 Fig. 273. 
 
 100 too 
 
 S CEPUEI. 
 
 R CASSIOPELE. 
 
 Fig. 274. Fig. 275. 
 
 Mean Light-curves of certain Variable Stars. 
 
 217 
 
2l8 THE STARS. 
 
 variable stars at the dates stated, whilst Fig. 276 records the 
 fluctuations in the temporary star Nova Persei between 
 February and April 1901 as recorded at Oxford by Mr. A. A. 
 Rambaut, the Radcliffe observer. 
 
 TEMPORARY STARS. 
 
 A branch of sidereal astronomy which has much of the 
 sensational about it is that which is covered by the title 
 "Temporary Stars." At many epochs in the world's history 
 there have suddenly burst forth in the heavens, and shone as 
 bright stars for limited periods of time, stars which probably 
 ought not to be called stars at all. Some of the objects thus 
 recorded by old monastic and other writers undoubtedly were 
 only mere luminous meteors, or fireballs, and a few of them 
 comets ; but, apart from these objects we have trustworthy 
 records of stars suddenly becoming visible in places where no 
 stars had been seen before, and which remained visible for 
 weeks or months before their final disappearance. The cases 
 are not numerous of a star suddenly appearing and rising in 
 brilliancy to become conspicuous, for it has been more common 
 for a conspicuous star to appear suddenly in a place where no 
 star had been previously seen, and then at once to begin a 
 downward career. 
 
 It will be prudent, if we desire to take our stand on the firm 
 ground of fact, not to go too far back in seeking for instances 
 of temporary stars, and Tycho Brahe's star of 1572 in Cassio- 
 peia is the most ancient which I desire to put forward. He 
 has left us a full account of it, the substance of which is that 
 it became visible in November 1572, and remained visible 
 for 17 months, or till March 1574. At its best it was 
 brighter than Sirius, and rivalled Venus. Tycho Brahe, having 
 no telescope, of course lost the star as soon as it descended 
 below the 6th magnitude, and nobody seems to have seriously 
 attempted to look into the matter until D'Arrest, in 1864, pub- 
 
TEMPORARY STARS. 
 
 2I 9 
 
 lished a map of an area in Cassiopeia which was supposed to 
 include the place of Tycho's star. Argelander, having assigned 
 a position to the star, pointed out that there was a little star 
 almost exactly in the right place, and Hind and Plummer 
 followed this up in 1873 by stating that this little star was 
 variable. There the matter remains, no one apparently having 
 attempted to follow it up since. The exact position of Tycho's 
 
 Fig. 276. Light Changes in Nova Persei, 1901. 
 
 star, as given by Argelander, brought up for precession to 
 January i, 1913, is as follows : 
 
 R.A. 
 
 h. m. s. 
 O 19 56 
 
 Declination . 63 40-0' N. 
 
 The reason that some attention was given to the subject in 
 1873 was tnat tne theory was current that Tycho's star was a 
 
220 THE STARS. 
 
 reappearance of objects alleged to have been temporary stars, 
 and visible in 945 and 1264 ; so that, if those objects had been 
 temporary stars, there was the slight possibility (very slight) 
 that Tycho's star was the reappearance of a variable star whose 
 period was 300 years, more or less. But all this would seem to 
 be an argument devoid of foundation, and there is no solid 
 reason whatever for suspecting that Tycho's star was to reappear 
 after the lapse of three centuries. 
 
 The year 1604 was marked by the appearance of a temporary 
 star in the constellation Ophiuchus, which became nearly as 
 bright as Venus, and lasted a year or more. Kepler wrote a 
 book about it which has come down to us. 
 
 In 1670 a new star appeared in Cygnus, which rose to the 
 brightness of a star of the 3rd magnitude, and lasted two years 
 from first to last, during which period it more than once 
 increased in brightness, and then diminished, before it finally 
 disappeared. 
 
 A long interval elapsed before we had another new star. 
 On April 28, 1848, a 5th-magnitude star was seen by Hind in 
 Ophiuchus, which a few weeks later rose to the 4th magnitude, 
 and then descended to the nth or I2th magnitude, at which it 
 may or may not still be. 
 
 May 1866 gave us a new star, which created a considerable 
 sensation because of the sudden outburst which characterised 
 it. As a star of mag. 9^ it was recorded by Argelander 
 in 1855, but Birmingham, at Tuam, in Ireland, saw it on 
 May 12, 1866, as a star of mag. 2. Combining the negative 
 testimony of Schmidt, of Athens, with the positive testimony 
 of Birmingham, it would seem that this star suddenly rose 
 from the 4th to the 2nd magnitude in about three hours 
 on the evening on which Birmingham saw it. It soon began 
 to fade away, and by the end of the month had fallen to 
 mag. 8. It continued below magnitude 9 all through the 
 following summer, but rose to 7^ in September, and was 
 nearly stationary in brightness for the remainder of the year. 
 
QVADRANS MVRAL1S SIVE TICHONICUS. 
 
 Fig. 277. Tycho Brahe's Mural Quadrant for measuring 
 Vertical Angles. 
 
222 THE STARS. 
 
 This star is now permanently put upon the list of variable 
 stars under the designation of T Coronae ; but it seems to 
 have been ignored by variable-star observers during recent 
 years. 
 
 On November 24, 1876, Schmidt, at Athens, observed anew 
 star of the 3rd magnitude in Cygnus, yellowish in colour. By 
 the end of December it had descended to the 7th magnitude, 
 and afterwards became still "smaller. The last recorded 
 observation of it which I have been able to find is dated 
 September 2, 1877, when the spectrum was reduced to a single 
 line, the continuous spectrum and all the other lines having 
 disappeared. 
 
 August 1885 saw the outburst in the constellation Andromeda 
 of a new star, which created at the time a great deal of excite- 
 ment. This excitement was largely due to the position of the 
 star, which, seemingly in the great nebula, was not of it, having 
 the appearance of standing out sensibly in front of the nebula. 
 When first seen, which appears to have been on August 22, or 
 a few days previously, the star was of about the 6th magnitude. 
 It never got beyond that, and rapidly began to decline until it 
 reached about the iith magnitude, and then it became visually 
 lost in the nebula, though from first to last the impression 
 conveyed on those who viewed it, including myself, was that 
 it had nothing to do with the nebula itself. 
 
 Later in the same year, on December 17, J. E. Gore found 
 a new star in Orion which, during its visibility, passed from 
 mag. 6 to mag. 9, or less, and then disappeared, and 
 afterwards again came into view, and is now permanently 
 enrolled as a variable star, though no explanation can be offered 
 of its sudden increase of light in the month in which it was 
 first found. It is now known as U Orionis. 
 
 Early in 1892 a new star appeared in the constellation 
 Auriga, the circumstances connected with which are highly 
 interesting. The fact of the star's existence was communicated 
 to Dr. Copeland, Director of the Observatory of Edinburgh, 
 
NEW STARS. 223 
 
 by means of an anonymous postcard, which led him at once 
 to search for and find the star, which he was told was of the 
 5th magnitude. The authorship of the postcard was after- 
 wards avowed by a certain Dr. Anderson, who found the star 
 by means of McClure's edition of Klein's Star Atlas, used in 
 conjunction with a small pocket-telescope. 
 
 When news of the discovery was conveyed to the other side 
 of the Atlantic, Professor Pickering, of Harvard College 
 Observatory, found that Anderson's star had been photo- 
 graphed by him 13 times between December 10, 1891, and 
 January 20, 1892. He considered that his plates took all stars 
 down to the 9th magnitude, and that, as the new star did not 
 appear on the plate of December 8, it must have brightened 
 up between December 8 and December 10. The new star, 
 henceforth known as Nova Aurigas, remained of the 4th or 5th 
 magnitude till the end of February, when it rapidly diminished, 
 and on April 26 was no more than of the i6th magnitude. 
 Later on in the summer it brightened up to about the loth 
 magnitude, and then fell again to the I2th magnitude. 
 
 In 1901 a new star appeared in Perseus, which lasted a long 
 time, and underwent various and noteworthy changes. There 
 is some little uncertainty as to who first discovered it. It 
 seems to have had several independent discoverers on Febru- 
 ary 22, but the first public announcement was made by 
 Dr. Anderson of Edinburgh, the discoverer of Nova Aurigce 
 nine years previously. It is interesting to add that it was also 
 discovered on the same night, February 21, at KiefT, in 
 Russia, by a boy 16 years of age named Borisiak. When 
 Dr. Anderson first saw the star he put its magnitude at 2|, 
 whilst Borisiak, perhaps erroneously, called it i. The evidence 
 as to its history seems to show that on February 20 the star 
 had not become visible. After February 22 it became a very 
 bright ist-magnitude star, though it only remained such for a 
 day or two, and by March 18 had descended to the 4th magni- 
 tude, which in June had become the 6th magnitude, and at the 
 
224 THE STARS. 
 
 end of the year the yth. These changes were not regular, 
 because its brilliancy oscillated several times. The final history 
 of this Nova was very remarkable, because it seems to have 
 either turned into a nebula, or, in some mysterious way, to 
 have given birth to one ; but the details as to this would occupy 
 too much space for these pages. 
 
 Other new stars of recent date are the following : Nova 
 Lacertae, discovered on December 30, 1910, by the Rev. 
 T. E. Espin ; Nova Sagittarii, discovered photographically in 
 September 1899 at Arequipa, in Peru, but the fact not known 
 till an examination of the plates in 1911 ; Nova Geminorum, 
 discovered in March, 1912, by Enebo at Dombaas, in Nor- 
 way. It showed spectroscopically the characteristic hydrogen 
 bands, accompanied by dark bands on the side towards the 
 violet. 
 
 Professor E. C. Pickering, in 1881, proposed the following 
 classification to link together all the stars which come under 
 the designation of " temporary " or " variable " stars : 
 
 1. Temporary stars. Examples : Tycho Brahe's star of 1572, 
 new star in Corona 1866. 
 
 2. Stars undergoing great variations in light in periods of 
 several months or years. Examples : o Ceti, and x Cygni. 
 
 3. Stars undergoing slight changes according to laws as yet 
 unknown. Examples : a Orionis and a Cassiopeia?. 
 
 4. Stars whose light is continually varying, but the changes 
 repeated with great regularity in a period not exceeding a few 
 days. Examples : /3 Lyrse and 8 Cephei. 
 
 5. Stars which every few days undergo for a few hours a 
 remarkable diminution in light, this phenomenon recurring with 
 great regularity. Examples : j3 Persei and S Caneri. 
 
 In the case of stars belonging to class 5, the observed 
 variations could be very satisfactorily explained by the theory 
 that the reduction in light is caused by a dark eclipsing 
 satellite. 
 
 The foregoing accounts of recent new stars will suffice to 
 
OPENINGS FOR WORK. 225 
 
 give the reader a general idea of what these objects are, and 
 I hope to bring it home to amateur astronomers that, if they 
 choose to avail themselves of opportunities which from time to 
 time occur, they may often be able to render useful service to 
 science, and, at the same time, to earn some credit and distinc- 
 tion for themselves. 
 
CHAPTER XII. 
 GROUPS OF STARS AND NEBULA 
 
 Stars in groups classified. Irregular groups. Clusters of stars more 
 or less compressed. Nebula. Classification of nebula. Annular 
 nebula. Elliptic nebula. Spiral nebula. Planetary nebula. 
 Nebulous stars. Large nebula of irregular form. Exemplification 
 of these classes named. Distribution of nebula and clusters over 
 the heavens. The Milky Way. Brief description of its position. 
 Its historic names. 
 
 HAVING started in the previous chapter with single stars and 
 gradually got up to multiple stars which phrase may be said to 
 mean, say, half a dozen stars under one roof, as it were we 
 must now pass on to groups of stars which are to be met with 
 in the heavens in great numbers and embracing all gradations 
 of quantity from a few dozen up to literally myriads, according 
 to the Greek use of that word. 1 
 
 The variety of these groups to be found in the heavens is 
 very great, both as regards the number of the stars composing 
 the groups, and also as to their general shape. We may con- 
 veniently consider the objects now to be described under 
 three general heads, the third of which will need special 
 subdivision by itself. The three main divisions may be as 
 follows : 
 
 (1) Irregular groups, many of them visible to the naked eye. 
 
 (2) Clusters of stars more or less compressed and sym- 
 
 1 /xupiot = ten thousand, also "countless." 
 226 
 
FIG. 278 
 
 PLATE LXXXVI. 
 
 The Pleiades (Tempel). 
 
 With the Nebula near Merope. 
 
 226] 
 
FIG. 279 
 
 PLATE LXXXVII. 
 
 Nebulae in the Pleiades, Dec. 8, 1888 ( Isaac Roberts). 
 
 [227 
 
CLASSIFICATION OF CLUSTERS AND NEBUL/E. 227 
 
 metrical, and resolvable into separate stars with adequate 
 optical assistance. 
 
 (3) Nebulae for the most part irresolvable, however powerful 
 may be the telescopes which are brought to bear on them. 
 
 The third class may be subdivided as follows, the sub- 
 divisions having regard chiefly to differences of shape. 
 (i) Annular nebulas. 
 
 (ii) Elliptic nebulas. 
 
 (iii) Spiral nebulas. 
 
 (iv) Planetary nebulae. 
 
 (v) Nebulous stars. 
 
 (vi) Large nebulas of irregular form. 
 
 The foregoing classification may be considered as compre- 
 hending all the known clusters and nebulas ; but the reader 
 must be warned beforehand that only a few objects in some of 
 the classes, and none in the other classes are at all within the 
 reach of the comparatively small telescopes which the readers 
 of this work are supposed to possess. 
 
 Many of the objects in class (i) are more or less non-teles- 
 copic, so to speak ; that is to say, are too large and scattered 
 to be advantageously viewed in any telescope other than a low- 
 power opera-glass with a very large field. 
 
 The Pleiades and Hyades, both in Taurus, are undoubtedly 
 the best known of these groups. Indeed, so old are they 
 historically that the first mention of them begins with Homer. 
 The tradition is well known, and as old as Ovid, that there 
 were originally 7, but that one of them has been lost. The 
 origin of this idea is unknown, and it would seem that one 
 ought to say that the tradition is scientifically untrue, because, 
 not only can 7 still be counted, but a good many more. 
 This group is really a very good test of eye-sight, because, 
 whilst ordinary eyes often do not get beyond six in the 
 counting, good eyes and extra good eyes can get up to 8, 10, 
 or even 12. A proof that there is nothing magical in the 
 number 7 is found in the fact that 9 of the stars have for 
 
228 GROUPS OF STARS AND NEBULA. 
 
 unnumbered centuries borne specific names, which, with their 
 magnitudes, are as follows : The brightest is known as Alcyone 
 (alias r) Tauri) of the 3rd magnitude ; next come Electra and 
 Atlas, both 3^ ; then Maia 4, Merope 4^, Taygeta 4^, whilst 
 Celeno, Asterope, and Pleione are all much about the same 
 size, say mag. 6. But besides these more or less conspicuous 
 members of the group, several dozen stars of smaller size are 
 revealed in the telescope. There is a matter connected with 
 the Pleiades which is somewhat mysterious. In 1859 a well- 
 known observer, Tempel, noticed amongst the group an object 
 which he took to be a telescopic comet ; but, as it was after- 
 wards found to be a fixture, and not to be moving, it was clear 
 that it was not a comet, but a nebula which had suddenly 
 manifested itself. As time went on and attention was given to 
 the subject it became certain, not only that Tempel had 
 observed a genuine nebula, but that nebulous matter was to 
 be seen in various parts of the cluster, no less than five of 
 the chief stars (Alcyone, Electra, Maia, Merope, and Celeno) 
 being involved in nebulosity. It seems certain that this 
 nebulous matter has only come into view during the past 
 half-century, but it is impossible to offer any explanation of 
 the fact. 
 
 The Hindoos call the Pleiades "The Hen and Chickens." 
 The Australian black-fellows call them " Meamei " = " The 
 Seven Sisters." In Don Quixote Sancho Panza describes his 
 fancied ride through space, saying : " We happened to travel 
 that road where the seven she-goat stars were " ; and the Don 
 adds : " It was impossible for us to reach that part where are 
 the Pleiades, or the seven goats, as Sancho calls them." 
 
 The Hyades constitute a group of stars altogether inferior to 
 the Pleiades in interest, not only because the stars are smaller, 
 but because they are much scattered. Still, they must be 
 treated as being a group, and they have been recognised as such 
 for many centuries. 
 
 In the constellation Cancer we have another historic group 
 
FIG. 280 
 
 PLATE LXXXV1II. 
 
 The Cluster 13 M. Herculis (W. E. Wilson}. 
 
 2281 
 
FIG. 281 
 
 PLATE LXXXIX. 
 
 [229 
 
CONSPICUOUS CLUSTERS 229 
 
 known as Praesepe, which makes a very effective show in a 
 telescope of large field and low power. This object is some- 
 times met with in old scientific books under the name of the 
 " Bee-hive,' ; but that name, as well as its Latin name, is lost in 
 antiquity. Fully 2000 years ago it was recorded by two Greek 
 authors as available to indicate the approach of rain, the idea 
 being that, under such prospect, the group lost its sharp stellar 
 appearance and became misty. 
 
 The constellation known as Coma Berenices is made up of 
 a number of stars which, though it may be named in connec- 
 tion with the three preceding groups, has its constituent 
 stars too scattered to be quite fairly comparable with them. 
 
 We must now proceed to consider the objects which are 
 included under the second of the main heads already specified, 
 namely, Clusters of Stars. These are of various sizes and 
 shapes. Many of them appear in small telescopes as nebulas 
 and nothing else, but in some cases even a small amount of 
 additional optical power renders it easy to see that the 
 seemingly nebulous mass really consists of a number of 
 separate stars. A certain number of the objects belonging 
 to the class which we are now considering are specially labelled 
 " Globular Clusters." They have received this name because 
 they present the appearance of stars massed together as globes, 
 though the causes which gave them this form and keep them 
 retaining it are unknown. The most striking object of this 
 character in the Northern Hemisphere is the cluster known as 
 13 M. Herculis for which the Southern Hemisphere provides 
 a magnificent counterpart in the clusters surrounding the Stars 
 co Centauri and 47 Toucani. 
 
 The letter M. attached to the cluster in Hercules, just named, 
 deserves explanation. It stands for the initial of the surname 
 of a famous French astronomer, Messier, who earned the 
 thanks of posterity by cataloguing, nearly a century and a half 
 ago, all the objects in the heavens which he was able to 
 observe in a telescope with an aperture of only 2 inches. 
 
230 GROUPS OF STARS AND NEBULAE. 
 
 With such a telescope he was naturally unable to realise very 
 distinctly the difference between the objects which we now 
 call clusters and those which we call nebulae ; and he lumped 
 all together under the comprehensive title " Nebulosities and 
 Masses of Stars." His labours, notwithstanding that his 
 opportunities were limited, are still of use to us in so far 
 that, whenever we come across a cluster or nebula with 
 Messier's number and letter prefixed to it, we know at once 
 that it can be seen with a small telescope, however imperfectly. 
 
 Smyth described 13 M. Herculis as "an extensive and mag- 
 nificent mass." Sir J. Herschel saw signs of its stars forming 
 curved lines, which feature Lord Rosse interpreted as indicating 
 a spiral formation. I have not myself seen o> Centauri or 
 47 Toucani, and therefore cannot speak of them from personal 
 knowledge ; but, judging by the language used by those who 
 have seen them, they must be magnificent objects, surpassing 
 the cluster in Hercules. Indeed, Pickering expressly describes 
 < Centauri as " undoubtedly the finest in the sky," and 47 
 Toucani as " second only " to w Centauri. 
 
 Next to this as regards the clusters visible in England seems 
 to come 5 M. Libras, very accurately described by Webb as a 
 "beautiful assemblage of minute stars greatly compressed in 
 the centre." Sir W. Herschel counted not less than 200 stars 
 in it, whilst Smyth's description is very accurate in saying that 
 it has " out-liers in all directions and a bright central blaze." 
 Messier committed himself to an opinion respecting this cluster 
 which illustrates a remark which I have already made, that 
 these objects vary much in appearance, according to the size of 
 the telescope employed in viewing them. We shall see 
 presently many proofs of this. Meanwhile, Messier's remark 
 respecting 5 M. Librae should be posted up as a caution to men 
 of science. " He assured himself that it did not contain a 
 single star." 
 
 Other clusters of the type of those which have gone before 
 will be found amongst the list in the Appendix. 
 
FIG. 282 
 
 PLATE XC. 
 
FIGS. 283-285 
 
 PLATE XCI. 
 
 2 M. Aquarii. 5 M. Librae. 
 
 (Sir J. Herschel.) 
 
 2 M. Aquarii (Earl of Rosse). 
 
 This picture shows how a large telescope opens out the stars which 
 
 [appear squeezed together in a small telescope. [231 
 
REMARKABLE CLUSTERS. 23! 
 
 Respecting one of these globular clusters, 80 M. Scorpii, a 
 singular circumstance is on record. In 1860 a well-known 
 observer Pogson, directing his telescope to a part of the 
 heavens which should have included the cluster, found that it 
 had disappeared, and that a 7th-magnitude star was occupying 
 its place. A fortnight later the star had disappeared and the 
 cluster was again visible, presenting its normal appearance. 
 These changes were also noticed by two German observers, 
 and therefore there can be no doubt about their reality. It 
 seems impossible to suppose that any physical change had 
 taken place in the cluster, and the conclusion is therefore 
 inevitable that the star was a temporary one, quite independent 
 of the cluster, which had burst out in front of it and lasted a 
 very few days, and had then disappeared, owing to the operation 
 of some unknown cause or causes. 
 
 Of clusters, not globular, but large and attractive, 67 
 M. Cancri may be named as noteworthy. But by far the 
 most striking and beautiful of the loose and irregular clusters 
 in the heavens, probably that which surrounds the star K. Crucis 
 is the finest. Sir J. Herschel, when at the Cape in 1833 and 
 following .years, observed this cluster and described.it as 
 one of the most beautiful of its class. Some 40 years later, 
 Russell, at the Sydney Observatory, carefully charted its stars, 
 with the result that he found that many of them in the 40 
 years' interval had moved from Herschel's position, and in 
 consequence (it was to be assumed) of their being endued 
 with proper motion. Russell's description of the cluster is as 
 follows: "The colours of this cluster are very beautiful, and 
 fully justify Herschel's remark that it looks like a ' superb piece 
 of fancy jewellery.' " 
 
 We will now pass on to the nebulae, properly so-called, the 
 number of which has been greatly augmented of recent years. 
 Sir W. Herschel developed Messier's catalogue of 103 objects 
 into hundreds, which Sir John Herschel's labours at the Cape 
 and elsewhere brought up to thousands. In 1864 he published 
 
232 GROUPS OF STARS AND NEBUL/E. 
 
 a complete general catalogue of all those then known, which 
 numbered 5079 objects. This catalogue seems to have 
 stimulated the developement of this branch of sidereal astro- 
 nomy, because when Dreyer republished Sir John Herschel's 
 catalogue revised, corrected and enlarged, the new edition 
 comprised 7840 objects ; and this number has since been 
 largely added to, especially by work in America, and as the 
 incidental res.ult of searches for new comets and double stars. 1 
 
 It should be clearly stated that, for the profitable examination 
 of nebulas of all kinds, large telescopes are indispensable, and 
 that the number which can be viewed even with moderate 
 satisfaction in small ones is very limited ; but, in order to 
 present a complete survey of these objects, according to the 
 classification laid down on a previous page, I shall be obliged 
 to name a certain number which are hopelessly beyond the 
 reach of small telescopes. 
 
 Of "Annular Nebulae " the heavens afford only a few examples 
 scarcely a dozen in all. The most remarkable is 57 M. Lyras, 
 situated about midway between /3 and y Lyras, and the only 
 annular nebula within reach of a telescope of moderate power. 
 Sir J. Herschel described this as having the appearance of a 
 flat, oval, solid ring with the central vacuity not quite dark, 
 out " filled in with faint nebula like a gauze stretched over a 
 hoop." Lord Rosse, Chacornac, and Secchi, all claimed to 
 have resolved this object into stars, whilst Huggins asserted 
 that it was wholly gaseous. 
 
 This question of gaseous nebulae seems to 'me one of great 
 difficulty in several respects, and I must confess myself not to 
 be satisfied with many of the claims put forward based on 
 spectroscopic observations. 
 
 " Elliptic Nebulae " of various degrees of eccentricity are not 
 uncommon, but there is only one conspicuous large one, namely, 
 
 1 If I do not make use anywhere of the phrase " white nebulae," which some 
 writers have recently tried to acclimatise, it is because I think it an unneces- 
 sary and illogical phrase. Practically all nebulae are " white." 
 
PLATE XCII. 
 
 The Clusters 33 and 34 Ijl VI. Persei (A. A. Rambaut, Radcliffe 
 
 Observatory, Oxford}. 
 
 232] 
 
PLATE XC1II. 
 
 The Great Nebula in Andromeda (H. J. Shepstowe). 
 
 [232.1 
 
FIGS. 288-289 
 
 PLATE XCIV. 
 
 
 
FIG. 290 
 
 PLATE XCV. 
 
 Spiral Nebula in Ursa Major (H. J. Shepstowe). 
 
 [233 
 
SPIRAL NEBULAE. 233 
 
 the " Great Nebula in Andromeda " (31 M.). Its elliptic outline 
 is shown in a small telescope, and the nebula is sufficiently 
 large and bright to be seen in any small telescope ; but instru- 
 ments of great size are required to show the curious details of 
 rifts or black streaks which run nearly parallel to the major 
 axis of the oval on the S. side. Taken as a whole, the nebula 
 must be pronounced as irresolvable, and certainly non-gaseous, 
 and a considerable number of isolated stars are to be found 
 within its limits. There is no other elliptic nebula within the 
 reach of small telescopes, and therefore it is not much use my 
 pointing out that there are several which have double stars at 
 or near each end of the ellipse, which in these cases is very 
 elongated compared with its breadth. 
 
 The existence of the class of nebulae known as " Spiral " or 
 " Whirlpool " nebulae was first made known by the 3rd Earl of 
 Rosse when he brought his great reflectors at Parsonstown to 
 bear on these objects. Two or three in particular of those 
 whose structure was discovered by him are well known because 
 they have been engraved in a great number of books ; but 
 the observations and researches of recent years, especially 
 those of Huggins and Roberts, have rendered it probable that 
 masses of nebulous matter, and indeed aggregations of stars 
 generally assuming a spiral form, are much more common than 
 was supposed when Lord Rosse brought to an end his own 
 discoveries in this field. 
 
 The two most important spiral nebulas, determined to be such 
 by Lord Rosse, are those known as 51 M. Canum Venaticorum, 
 and 99 M. Virginis. The former exemplifies in a very remark- 
 able degree, not only the changes which take place in the 
 appearance of clusters and nebulae according as they are viewed 
 through small or large telescopes, but also the danger of jump- 
 ing at conclusions and using dogmatic language in dealing with 
 these matters. Figs. 288 and 289 represent this nebula as 
 drawn by Admiral Smyth, Sir J. Herschel and Lord Rosse 
 respectively, whilst Fig. 290 supplies a photographic view. 
 
234 GROUPS OF STARS AND NEBUUE. 
 
 Except for the direct evidence of the fact which is available, it 
 would be difficult for any chance spectator to suppose that all 
 these pictures represented the same object. In the case of 
 99 M. Virginis, the spiral form may be said to be so obtrusively 
 obvious in Lord Rosse's sketch, as not to need even a moment's 
 argument. An inquiring mind will naturally ask the question, 
 What meaning is to be attached to the spiral formations in the 
 heavens which are here brought under notice ? I must frankly 
 admit that I am not prepared with an answer to this question ; 
 which becomes still more difficult when we call to mind the fact 
 that an American observer, Holden, speaking of a planetary 
 nebula (presently to be described), says that it " is apparently 
 composed of rings overlying each other, and it is difficult to 
 resist the conviction that these are arranged in space in the 
 form of a true helix" another way of expressing the idea of a 
 spiral being concerned. 
 
 The term "planetary" was applied by Sir W. Herschel to 
 certain nebulae, small in number and, with one special exception, 
 small in size, which exhibit the appearance of discs having well- 
 defined edges, either circular or slightly oval and of uniform 
 luminosity, which features caused them to offer considerable 
 resemblance to certain of the planets. 97 M. Ursae Majoris is 
 the most striking of these, as it is also the largest, for it has a 
 diameter of 2' 40". Lord Rosse's picture of it evidently justifies 
 the name of "Owl Nebula" which he gave to it, albeit his 
 picture negatives the general description of these planetary 
 nebulas with which I started at the commencement of this 
 paragraph. The planetary nebula which I mentioned just now 
 as presenting the features of a helix is 37 y IV. Draconis, as 
 viewed in the Lick telescope ; but of course no ordinary tele- 
 scope will bring out the details which Holden has described. 
 
 Planetary nebulae seem to possess some peculiarities which 
 differentiate them from nebulae generally. The great majority 
 of them are situated in, or close to, the Milky Way ; they are 
 much more numerous in the Southern Hemisphere than in the 
 
FIG. 291 
 
 PLATE XCVL 
 
 The Nebula 4620 h = 58 Itf VIII. Cygni (E. E. Barnard}. 
 
 1 234 
 
FIG. 292 
 
 PLATE XCVII. 
 
 The Nebulae 81 and 82 M. and a nebulous Star in 
 Ursa Major (Isaac Roberts}. 
 
 [235 
 
IRREGULAR NEBULAE. 
 
 235 
 
 Northern ; they are most of them gaseous, according to spectro- 
 scopic observations ; and many of them seem to exhibit a bluish 
 tinge of colour. 
 
 " Nebulous stars " can only be described as stars which are 
 surrounded by or, perhaps it will be better to say which seem 
 to be surrounded by nebulous matter symmetrical or circular 
 in outline. Hind remarked that the stars thus enveloped 
 " have nothing in their appearance to distinguish them from 
 others entirely destitute of such appendages." The brightest 
 nebulous star, 
 recognised as such, 
 is i Orionis, of 
 mag. 3^ ; though 
 the star iwhich is 
 generally named as 
 the most repre- 
 sentative of its 
 class is 45 I# IV. 
 Geminorum, which 
 Sir John Herschel 
 described as an 
 8th-magnitude star 
 " exactly in the 
 centre of an exactly 
 round bright atmo- 
 sphere 25" in diameter." There are not many of these stars 
 known, and the few there are cannot be usefully observed 
 except with large telescopes. 
 
 The 6th and last class of nebulae which require notice are 
 altogether of irregular form and large size. Though most of 
 them which will now be mentioned are discernible in small 
 telescopes, yet here, again, instruments of great light-gathering 
 power are indispensable for their satisfactory examination. 
 
 Mention has already been made of the " Great Nebula in 
 Andromeda," which, for some reasons, might with propriety be 
 
 (Sir J. Herschel.) (Earl of Rosse.) 
 
 Figs. 293 and 294. Planetary Nebula 97 M. 
 Ursae Majoris. 
 
 Generally known as " The OwkNebula." 
 
236 GROUPS OF STARS AND NEBULA. 
 
 enrolled in the class which we are now considering, especially 
 on account of its size and brilliancy, and because its elliptic 
 form, which was the reason for including it under the head of 
 elliptic Nebulas, disappears almost entirely with optical assist- 
 ance on a large scale. 
 
 Subject to this remark, the "Great Nebula in the Sword- 
 handle of Orion " must be put first in importance in any list of 
 irregular nebulae. Its size and brightness led to its discovery 
 very soon after the invention of the telescope, and it has 
 received more attention from the pens and pencils of astrono- 
 mers than any other object in the sidereal heavens. The first 
 feature which immediately forces itself on our attention when it 
 is looked at is the singular vacuity which is called " The Fish's 
 Mouth," from its supposed likeness to the mouth of various sorts 
 of fish. This is no sooner seen than the second object to attract 
 attention immediately does so, namely, "The Trapezium"of stars, 
 the most important of which is 6 Orionis, which, on account of 
 its near neighbours, is generally spoken of as a " multiple star." 
 The largest member of the family being 6, the use of the word 
 "Trapezium" naturally implies that there are three other stars 
 close at hand to make up the figure which geometricians call a 
 trapezium : but this is not the end of the matter. 
 
 Whilst any small telescope will reveal without much difficulty 
 the 4 special stars, a 5th and 6th come into view when more 
 telescopic power is available ; indeed, these 5th and 6th 
 stars constitute a very good test of telescopes of 5 or 6 or 
 more inches of aperture. But it is claimed that three more 
 stars exist in or closely adjacent to the Trapezium, bringing 
 up the total number to 9. The existence of these 3 supple- 
 mentary stars rests especially on the authority of Huggins, and 
 has been vehemently disputed. A fair summary of the situation 
 appears to be this : that there are other stars in or close to the 
 Trapezium ; that they are variable ; and that the 6th star 
 itself is variable. This last statement seems undoubtedly true, 
 and, if the 3 smaller stars are also variable, we have a com- 
 
FIG. 295 
 
 PLATE XCVIII. 
 
 236] 
 
FIG. 296 
 
 PLATE XC1X. 
 
 The Great Nebula in Orion (W. E. Wilson}. 
 
 [237 
 
THE GREAT NEBULA IN ORION. 
 
 237 
 
 plete explanation of the contradictions which have been indulged 
 in on the subject. This nebula, as a whole, illustrates in a 
 striking degree the discordances which constantly present them- 
 selves between hand-drawings of sidereal objects and photo- 
 graphs. The hand-drawings of this nebula all fail to do more 
 than con- 
 vey the 
 idea of 
 its being 
 a flat 
 patch of 
 nebulous 
 matter. 
 Or, if this 
 s t a t e - 
 ment 
 too defi- 
 nite, it 
 must 
 certainly 
 be said 
 that they 
 fail to 
 convey 
 any suffi- 
 cient in- 
 d i cations 
 of the 
 rlocculent 
 
 texture which is such a special feature of all the photographs 
 which I have ever seen. It is the existence of masses of 
 seemingly flocculent material which makes it so difficult to 
 accept the theory that nebulae, such as this one, are masses of 
 incandescent gas. 
 
 The nebula known as 30 Doradus is a very singular one, 
 
 North. 
 Fig. 297." The Trapezium of Orion," Jan. 1866. 
 
 (Huggins.) 
 
2.38 GROUPS OF STARS AND NEBULA. 
 
 owing to the strange convolutions of the nebulous matter, which 
 almost defy description. It is faintly visible to the naked eye, 
 of course as a mere patch, within the limits of the Nubecula 
 Major, to be presently described. 
 
 The nebula surrounding the star 77 Argus is another very 
 remarkable object remarkable alike from its special features as 
 well as its history. When Sir J. Herschel was at the Cape in 
 1833 and following years, he gave very careful attention to this 
 nebula and to the position of the chief star in it. He specially 
 pointed out a void space in the middle of the nebula, and that 
 the star was wholly surrounded by nebulous matter. He 
 remarked that " It is not easy for language to convey a full 
 impression of the beauty and sublimity of the spectacle which 
 this nebula offers as it enters the field of the telescope (fixed 
 in R.A.) by the diurnal motion, ushered in as it is by so glorious 
 and innumerable a procession of stars, to which it forms a sort 
 of climax." Some sensation was caused in astronomical circles 
 in 1863 by a statement, put forth by a Tasmanian observer 
 named Abbott, that the void space had altered in form, and that 
 the star 77 no longer had nebulous matter close up to it. These 
 allegations were proved to have been quite unfounded, and it is 
 difficult to realise how Abbott could have been led to make 
 them. Herschel had published, in connection with his obser- 
 vations, a careful drawing of the nebula, and it was found, 50 
 years afterwards, that his drawing still represented accurately 
 the general appearance of the object. 
 
 The nebula 20 M. Sagittarii is the chief member of an im- 
 portant group which, perhaps, would be better described as a 
 single mass of nebulous matter pieced together and exhibiting 
 a strange shape. Its special feature is a "three-forked rift or 
 vacant area, abruptly and uncouthly crooked, and quite void 
 of nebulous light." This is Sir J. HerschePs description 
 of it, and he goes on to say that a beautiful triple star " is 
 situated precisely on the edge of one of these nebulous 
 masses, just where the interior vacancy forks out into two 
 
FIG. 298 
 
 PLATE C. 
 
 The Nebula surrounding ?/ Argus (C. E. Peek, 1882), 
 
 238] 
 
FIG. 299 
 
 PLATE CI. 
 
 [239 
 
NOTEWORTHY NEBUL/E. 
 
 239 
 
 channels," This nebula is sometimes called the " Trifid Nebula 
 in Sagittarius." 
 
 It is unfortunate that Sagittarius should be a constellation 
 not very favourably situated for observation in England, for 
 in the nebula 8 M. Sagittarii we have another striking object 
 of a very diversified shape, and which is a mixture of nebula 
 and stars in the same field. It is an interesting question in 
 regard to cases such as this whether any relations subsist 
 between the nebulous matter and the stars ; that is to 
 say, whether the stars are 
 actually connected with the 
 nebula, or are merely opti- 
 cally superposed in front of 
 it. The question is one 
 which, in general, can only 
 be dealt with as a matter 
 of individual opinion. I 
 have already stated on a 
 previous page the strong 
 conviction that, in the case 
 of the temporary star which 
 burst forth some years ago 
 in the great nebula in 
 Andromeda, in viewing the pig. 300. The Nebula 17 M. Clypei 
 star, we were looking at an Sobieskii (Chambers). 
 
 object which happened to 
 
 be in front of the nebula, and had no connection with the 
 nebulous mass which we saw in the background. The nebula 
 8 M. Sagittarii may be detected by the naked eye ; but, of 
 course, a telescope, and one of some power, is needed to 
 bring out its features. 
 
 In the constellation known indifferently as Scutum Sobieskii, 
 or Clypeus Sobieskii, we have a nebula (17 M.) which is often 
 called, but not very judiciously, "The Horse-shoe Nebula," 
 though now the name of "The Omega Nebula" is more gener- 
 
240 GROUPS OF STARS AND NEBUIJE. 
 
 ally and properly attached to it. In real truth, when seen at 
 its best, it takes the form of 2 Greek omegas coupled together 
 at their bases by a bar of nebulous matter ; but the amateur 
 with a small telescope must be satisfied if he makes out the 
 shape of this object to be that of a swan without legs. One 
 needs, in these days, to be very wary of accepting suggestions 
 of changes in nebulae, but there does appear to be some 
 evidence that, within 50 years of Sir John Herschel's careful 
 record of the appearance of this nebula, it did undergo some 
 real change of form, according to the testimony of several 
 experienced observers and draughtsmen. 
 
 The next obje'ct which comes before us in the order of Right 
 Ascension is a very well-known nebula commonly called " The 
 Dumb-bell Nebula in Vulpecula." The name is very appro- 
 priate in speaking of it after viewing it with a telescope of 
 moderate size say, up to 6 or 8 inches of aperture ; but 
 greater optical power so completely transforms its appearance 
 that the idea of a dumb-bell quite passes out of one's thoughts. 
 The truth of this statement will be readily realised by an 
 examination in succession of the illustrations given (see Figs. 
 301-304). In a small telescope it appears like 2 somewhat 
 round nebulosities in contact. Sir J. Herschel saw it with 
 "an elliptical outline of faint light enclosing the two chief 
 masses"; but Lord Rosse's 2 reflectors made material changes 
 in its appearance. His 3-ft. reflector destroyed the regular 
 elliptic outline noted by Sir J. Herschel, whilst the 6-ft. re- 
 flector brought about a still more striking transformation, 
 and introduced a considerable number of stars individually 
 recognisable as such. 
 
 The constellation Cygnus furnishes a striking nebulous 
 aggregation (No. 4618 of Herschel's " General Catalogue "). 
 This has been described as a very large space 20' or 30' long 
 in Declination, and I hr. or more wide in R.A., full of stars and 
 nebula mixed. 
 
 The Southern Hemisphere contains 2 objects, known re- 
 
FIGS. 301-302 
 
 PLATE CII. 
 
 240] 
 
FIGS. 303-304 
 
 PLATE CIII. 
 
FIGS. 305-306 
 
 PLATE 
 
 Nebulous Region of > Ophiuchi. 
 
 Nebulous Region of y Cygni (E. E. Barnard}. 
 2406] Nebulosity not visible in telescope, but disclosed by photography, 
 
FIG. 307 
 
 PLATE CV. 
 
 The Nebula 14 Ijl V. Cygni (Lick Observatory}. 
 
 [240C 
 
FIG. 308 
 
 PLATE CVT. 
 
 The " Trifid Nebula " in Sagittarius. 
 
 240^1 
 
FIG. 309 
 
 PLATE CVII. 
 
 The " Trifld Nebula " in Sagittarius. 
 
 2400 
 
FIG. 310 
 
 PLATE CVIII. 
 
 Stars in Cygnus (Henry, at the Paris Observatory). 
 
 2 4 0/J 
 
FIG. 311 
 
 PLATE CIX. 
 
FIG. 312 
 
 PLATE CX, 
 
FIGS. 313-314 
 
 PLATE CXI. 
 
 Double Cluster in Perseus. 
 
 Black space void of stars with Constellation Sagittarius. 
 
 .[241 
 
DISTRIBUTION OF NEBULAE IN THE HEAVENS. 241 
 
 spectively as the Nubecula Major and the Nubecula Minor, 
 which are large patches of nebulous matter which received 
 their names from their cloud-like appearance and relative size. 
 The former is in the constellation Dorado, and the latter in 
 Toucan. Both are visible to the naked eye on a dark night, 
 but the smaller one is overpowered by moonlight. Sir J. 
 Herschel described them as " consisting of swarms of stars, 
 clusters, and nebulae of every description." The larger one is 
 about four times the size of the smaller. I am not acquainted 
 with any more complete or modern description of either. 
 Unfortunately, the Southern Hemisphere seems altogether lack- 
 ing in astronomical authors who might write books describing 
 what they had seen in the same way as the multitude of 
 European and American authors have described, and continue 
 to describe, the celestial sights visible in the Northern Hemi- 
 sphere. This absence of literary enterprise on the other side 
 of the world is much to be regretted, and we still have to 
 draw largely on the great work published in 1847 by Sir J. 
 Herschel, in which he recorded the results of his observations 
 at the Cape in 1834 and subsequent years. 1 
 
 A chapter on clusters and nebulae would not be complet 
 without some allusion to their distribution in the sky, which ii 
 exceedingly irregular. Subject to certain special exceptions, 
 it may be said that the fixed stars, commonly so-called, are 
 distributed fairly evenly over the whole sky ; but this is a 
 long way from being the case with the nebulas, as will be 
 readily understood by a simple inspection of Sir J. Herschel's 
 " Catalogue " of 5079 of these objects, which was published 
 in 1864. An examination of this volume discloses the follow- 
 ing striking results. Whilst Hour XII. of Right Ascen- 
 sion includes 686 nebulae, including clusters, and Hour XI. 
 421, Hour XIX. has only 79, and Hour XX. only 90. In 
 other words, the constellation Virgo and its neighbours 
 
 1 Results of Observations made during the years 1834-8 at the Cape of Good 
 Hope. 
 
 16 
 
242 GROUPS OF STARS AND NEBULAE. 
 
 include ith of the total number of nebulas recorded up to the 
 middle of the igth century ; and I do not suppose the rela- 
 tive proportions have been seriously destroyed by the later 
 discoveries. The regions nearest to the Milky Way are 
 least abundant in nebulas, whilst the two richest regions are 
 those which lie at the 2 poles of that great belt. Another 
 circumstance, doubtless of significance though we cannot tell 
 its meaning, is that the great majority of the nebulas indicated 
 by the spectroscope to be gaseous are situated either within 
 or on the borders of the Milky Way, whilst in the regions near 
 the poles of the Milky Way such nebulae are scarce, though 
 there are plenty of non-gaseous nebulae situated in those 
 localities. 
 
 This chapter must not be closed without a few words re- 
 specting the Milky Way itself, because it is one vast nebula 
 running right round the heavens in the form of a belt, or ring ; 
 at the same time a description of its course, if put into words, 
 would occupy more space than is here available. Any one 
 wishing to follow it right round the heavens through the various 
 constellations can do so in no better way than by patiently 
 going over the ground with Sir J. Herschel's well-known Out- 
 lines of Astronomy in his hands. 1 It is long and elaborate, 
 but very carefully framed. Suffice it, then, to say that the 
 course of the Milky Way conforms nearly to that of a great 
 circle inclined at an angle of about 63 to the Equinoctial, and 
 cutting that circle in R.A. 6h. 47m. and 8h. 47111. From this 
 it follows that its northern pole is situated in about R.A. 
 12 h. 47m., and Declination 27 N., whilst its southern pole 
 may be considered to be at oh. 47 m., and Declination 27 S. 
 
 Passing over the numerous and varied attractive features of 
 the Milky Way, which are too numerous and too varied to be 
 detailed here, mention must be made of a singular void space 
 in the constellation Sagittarius, the precise position of which 
 
 1 Herschel's description has been reprinted in my Handbook of Astronomy, 
 4th edition, vol. iii., and some other modern works. 
 
THE MILKY WAY. 243 
 
 is R.A. 17 h. 56m., and Declination 27 51' S. This black hole 
 is almost circular, and on the N.W. of it there are 4 stars, 
 the brightest of which is orange in colour. To the E. of this 
 hole there is another void space in the shape of a narrow 
 crescent ; but this space appears less black and less sharply 
 defined than the main vacuity previously described. 
 
 My last words here will be to recall the fact that, strange as 
 it may appear, the idea of spilt milk is associated in several 
 languages with what we still persist in calling "The Milky 
 Way," and that for centuries upon centuries past it has been 
 the subject of grotesque nomenclature and fantastic specula- 
 tions. Whilst the grotesque nomenclature may be said to 
 have ceased, I fear it cannot be said that, though we have 
 reached the 2oth century, fantastic speculations have come to 
 an end. 
 
CHAPTER XIII. 
 THE CONSTELLATIONS. 
 
 The subject one of great interest. The best way of learning their posi- 
 tions. The effects of the diurnal movement. Star-atlases and plani- 
 spheres. The constellations best learnt in the open air. List of 
 stars of the ist magnitude. Standard stars of the first 4 magnitudes. 
 Alignment of Stars. Origin of the constellations. Modern addi- 
 tions. A hasty survey of the Northern Hemisphere. 
 
 A VERY attractive chapter might be written on the constella- 
 tions in history and poetry with respect to their origin, names, 
 and gradual developement in numbers during a period, to put 
 it moderately, of not less than 3000 years ; but it would be 
 foreign to the design of this work to deal with the subject from 
 these standpoints, which would be more within the province of 
 the antiquarian than of the astronomer. The scope of this 
 work is so essentially to present the useful and practical side 
 of things that I must be wary of the temptation to stray away 
 from the limits thus imposed on me. 
 
 An account of the constellations in detail has been formed 
 into an independent chapter (post] to facilitate their study in the 
 open air with as little as possible to embarrass the student beyond 
 the unavoidable distractions of having to handle a star-atlas 
 and a lamp. I thus limit the suggested impedimenta because 
 many years' experience has taught me the mischief of trying to 
 do too many things at the same time ; and therefore I urge very 
 strongly the importance of earnest efforts to become familiar 
 
 244 
 
HOW TO STUDY THE CONSTELLATIONS. 245 
 
 with the constellations in respect to their positions and the 
 names and situation of the principal stars in each. 
 
 It is not an uncommon thing for a writer sitting down to 
 describe the constellations with an educational idea in view 
 to treat each constellation as if it were a parish in a county a 
 geographical unit standing quite by itself. This, in my opinion, 
 is a way of looking at the constellations which must be carried 
 out with great discretion and considerable reserve, because it 
 is often apt to lead to stars and other objects being lost for the 
 particular night by reason of the diurnal movement taking 
 them out of sight whilst the student is looking another way. 
 
 What I mean will be better understood if I put it in this way. 
 When, on a given night, an observer wishes to lay himself out 
 for a night's work, let him begin by ascertaining what con- 
 stellations are on the meridian when his work begins, and, 
 having just grasped them generally, let him begin by examining 
 the stars which are on the meridian in the extreme South (this 
 for England), and then work backwards northwards on the 
 same R.A. towards the North Pole behind him. He need not 
 trouble about constellations and stars, say, within 30 of the 
 Pole, because these are visible all the year round, and therefore 
 are always within his reach ; but I do urge very strongly the 
 advantage of working in accordance with the hour of R.A., 
 which is on or near the meridian, and taking up his objects 
 selected for study as they severally come to meridian, and 
 guarding his eyes and thoughts from wandering promiscuously, 
 not only over the heavens, but even up and down the same 
 constellation. One thing is quite certain : the constellations, 
 as regards their relative positions, can only be effectively learnt 
 by open-air comparisons of the face of the heavens with a star- 
 map. 
 
 Whilst there are many star-atlases and planispheres in 
 circulation nowadays, there are undoubted ad vantages attending 
 the use of a map in which stars are portrayed in white on a 
 dark blue or black background. I have therefore used during 
 
246 THE CONSTELLATIONS. 
 
 many years, with very satisfactory results, the star-maps in 
 Keith Johnston's Atlas of Astronomy edited by Hind. Next 
 after this I would name McClure's Atlas published by the 
 Society for Promoting Christian Knowledge, which is an 
 English edition of a well-known German atlas, originally com- 
 piled by Heis of Miinster ; but McClure has greatly improved 
 it and added to it. The stars are, however, given as black 
 points on white paper. There is also given a deal of informa- 
 tion descriptive of the most striking stars and clusters of stars 
 and nebulae which deserve examination. 
 
 A clever American, Dr. C. J. Kullmer, of Syracuse, N.Y., 
 has invented a " Star-finder " somewhat in the form of an 
 ordinary Equatorial, so far as its fundamental principle is con- 
 cerned, but with various accessory features, and it has met with 
 a large amount of acceptance in America, though I do not think 
 that the instrument has yet become known in England. The 
 engraving will indicate its general form better than an elaborate 
 description. Regarded as an Equatorial in principle, the arrow 
 takes the place of the telescope tube. The instrument must 
 first be placed facing N. and the dials set for the day and hour ; 
 then the constellations can be sighted along the arrow without 
 further change. Star-maps on the dial show the grouping of 
 the stars in their actual position as seen in the sky, and the 
 arrow-points at the constellations, whether they are above the 
 horizon or not, and if the desired constellation is not visible at 
 the time, then, by revolving arrow and dial, the time of rising 
 can be found. The instrument stands about 10 inches high, 
 and the dial is 6 inches in diameter. It is adjustable to any 
 latitude in the Northern Hemisphere. Conversely to finding a 
 constellation or bright star which it is desired to find, it may be 
 used to identify the name of any constellation or bright star 
 towards which the arrow is directed. It also shows sidereal 
 time, which is read off opposite the graduation for March 21. 
 An incidental, but often very useful, item of information, which 
 can be arrived at with the assistance of the printed instructions 
 
KULLMER S STAR-FINDER. 
 
 247 
 
 supplied with the instrument, 
 is this : where a given con- 
 stellation or position in the 
 heavens will be (so far as the 
 observer's chance of seeing 
 it is concerned) in the sky on 
 a given day. Such informa- 
 tion would often be useful to 
 an observer who, knowing 
 the expected position, say, of 
 a new comet on a given day, 
 wants to know whether, and 
 at what hour, such comet 
 will be above his horizon so 
 that he may have a chance 
 of seeing it. Were Dr. Kull- 
 mer's invention to become 
 generally known in England 
 it would, "I think, be in much 
 request, for we have nothing 
 of the kind in use in this 
 country. 
 
 I will suppose the reader 
 to have made himself ac- 
 quainted with the apparent 
 sizes and positions of some 
 of the stars, and that he 
 intends to get up the whole 
 subject of the constellations 
 in a systematic manner. The means for doing this will be 
 found in a chapter specially devoted to the constellations in 
 detail, 1 and I will now proceed with a variety of general con- 
 siderations relating to the stars. 
 
 It is assumed that the reader is standing out in the open air, 
 
 1 See Chapter XIII (post). 
 
 Fig. 315. Kullmer's "Star- 
 finder." 
 
248 THE CONSTELLATIONS. 
 
 if possible in some elevated position, with as large an expanse 
 of sky, as clear of terrestrial obstructions, as possible, and that 
 he is armed with a suitable star-map, and something in the 
 nature of a bull's-eye lantern, which may be either of the common 
 type, and burning oil ; or, better still, that he has a portable 
 electric lamp. 
 
 The first thing to be attempted is to try and identify the 
 brightest stars, which are those of the ist of the 6 magnitudes 
 which are regarded as embracing the stars visible to the naked 
 eye. It will be useful to give a list of these stars in two forms : 
 (i) in the order of brightness, and (2) in the order of their Right 
 Ascension ; that is to say, in the order in which they succes- 
 sively rise, come to the meridian, and set. 
 
 FIRST-MAGNITUDE STARS IN ORDER OF BRIGHTNESS. 
 
 a Canis Majoris (Siritts}. 
 
 a. Argus {Canopus). Not visible in England. 
 
 a Centauri. Not visible in England. 
 
 a Bootis (Arcturus). 
 
 ft Orionis {Rigel). 
 
 a Aurigse (Capella). 
 
 a Lyrse ( Vega). 
 
 a Canis Minoris {Procyon). 
 
 a Orionis (Betelgeuse). 
 
 a Eridani (Achernar). Not visible in England. 
 
 a Tauri (Aldebaran). 
 
 ft Centauri. Not visible in England. 
 
 a Crucis. Not visible in England. 
 
 a Scorpii (Antares). 
 
 a Aquilae (Altair). 
 
 a Virginis (Spica). 
 
 a Piscis Australis (Fomalhattt). 
 
 ft Crucis. Not visible in England. 
 
 ft Geminorum (Polhix}. 
 
 a Leonis (ReguZus). 
 
 ci Cygni {Deneb.}, 
 
STANDARD STARS. 
 
 249 
 
 FIRST-MAGNITUDE STARS IN ORDER OF RIGHT ASCENSION. 
 
 h. m. 
 
 a Eridani (Achernar) . . 
 
 a Tauri {A Idebaran} 
 
 a Aurigse (Capella) 
 
 j3 Orionis (Rtgel) . 
 
 a Orionis ( Betelgeuse) . 
 
 a Argus (Canopus] 
 
 c Canis Majoris (Siritts) 
 
 a Canis Minoris {Procyoii) . 
 
 ft Geminorum {Pollux} . 
 
 a Leonis (Regulus) 
 
 a? Crucis . . % . 
 
 ft Crucis .... 
 
 a Virginis (Spica) . 
 
 ft Centauri .... 
 
 a Bootis {Arcturus} 
 
 a 2 Centauri .... 
 
 a Scorpii (Antares) 
 
 a Lyra ( Vega) . 
 
 a Aquilse (Altair) . 
 
 a Cygni (Deneb.) . 
 
 a Piscis Australis {Fomalhaut} 
 
 The dates appended are those on which the stars in question 
 will be found on or near the meridian at midnight. 
 
 It will be noticed that these stars are nearly equally divided 
 between the Northern and Southern Hemispheres ; that 10 are 
 Northern and n are Southern stars. 
 
 Seidel has suggested the following as standard stars for their 
 respective magnitudes : 
 
 Mag. 
 
 1. a Aquiloe, a Virginis, a Orionis. 
 
 2. a Ursse Majoris. 7 Cassiopeiae, Algol (at max.). 
 
 3. y Lyrse, 5 Herculis, 9 Aquilae. 
 
 / p Herculis, X Draconis (too bright). 
 ' I /x Bootis, 6 Herculis (not bright enough). 
 
 The reader is recommended to make himself familiar with all 
 the stars in the foregoing lists, because those in the first list 
 
 i 34 
 
 ~ 5741 
 
 October 17 
 
 4 3 
 
 + 16 20 
 
 November 28 
 
 5 I0 
 
 + 45 54 
 
 December 8 
 
 5 10 
 
 - 8 18 
 
 December 8 
 
 5 5o 
 
 + 723 
 
 December 28 
 
 6 22 
 
 -5238 
 
 December 27 
 
 6 41 
 
 - 1635 
 
 December 31 
 
 7 34 
 
 + 527 
 
 January 14 
 
 7 39 
 10 3 
 
 + 28 14 
 
 -t- 12 23 
 
 January 15 
 February 21 
 
 12 21 
 
 -6236 
 
 March 28 
 
 12 42 
 
 - 59 12 
 
 April 2 
 
 13 20 
 
 _ 10 42 
 
 April it 
 
 13 57 
 
 -5956 
 
 April 21 
 
 14 ii 
 
 + 1938 
 
 April 24 
 
 H 33 
 
 _ 60 28 
 
 April 30 
 
 16 24 
 
 _ 26 14 
 
 May 27 
 
 18 33 
 
 + 3842 
 
 June 29 
 
 19 46 
 
 + 838 
 
 July 18 
 
 20 38 
 
 + 44 57 
 
 July 31 
 
 22 52 
 
 - 30 5 
 
 September 3 
 
250 THE CONSTELLATIONS. 
 
 will serve to give him an idea of where the respective constella- 
 tions and indirectly where the other constellations are to be 
 found, whilst the second list will help him to recognise a star 
 of a named magnitude because he will know what a star of 
 such a magnitude should look like. 
 
 One of the most worrying difficulties which has to be faced in 
 studying the constellations, is the varying positions which they 
 occupy between their rising and setting. This really amounts, 
 more or less, to their being upside down at setting, compared 
 with what they look like when rising. This inevitable transform- 
 ation is another reason for students confining their attention 
 as much as possible to constellations which are on the meridian 
 at the time that study is going on ; or, at any rate, to constella- 
 tions within a couple of hours or so on either side of the 
 meridian. The fact that such upside-down changes do indeed 
 apparently take place will be better realised by an examination 
 of the annexed diagram than by any attempt to explain the 
 matter verbally. 
 
 Having identified a few conspicuous stars, the student must 
 habituate himself, first of all, to drawing imaginary lines from 
 one star to another, either literally on his map or mentally in 
 his head ; and then to seeing whether he can pick up in the 
 heavens a particular object he wants by running his eye across 
 the sky in accordance with the line or lines on his map, which 
 he must mentally reproduce by recalling his map. This pro- 
 cess of star-hunting is technically called " allineation" or 
 "alignment." It is obviously difficult to put in writing how to 
 do it, and the student must learn to do it for himself by the 
 exercise of thought and ingenuity. For instance, if he sees 
 on his map that the distance from star a to star /3 in a 
 certain constellation is so much, and that the small star p 
 which he wants to look at is in the same straight line with 
 a and /3 and fths of the distance beyond /3 that 3 is from a, 
 he must estimate, by more than one attempt perhaps to see, 
 when looking up at the stars, whither fths forwards from /3 
 
STAR CATALOGUES. 251 
 
 will take him : then, if his estimate on the map is fairly correct, 
 and if he is able to estimate where fths will take him on the 
 sky, he will find that the star /x for which he is looking is in the 
 place where he ought to find it. 
 
 This method of finding unknown stars by means of imaginary 
 lines drawn to and from known ones is the only means 
 available to those unprovided with an equatorial telescope 
 with its customary Right Ascension and Declination circles. 
 There are various popular star-charts and books with diagrams 
 in circulation with suggested lines drawn on them hither and 
 thither between different stars. Some of these books will be 
 useful to the tyro, but it not unfrequently happens that the con- 
 necting lines are engraved too heavily, and not only disfigure 
 the plates, but embarrass the eye in consulting the plates. 
 
 Though I do not intend to give a detailed statement of the 
 constellations on their historical side, it may be well just to 
 summarise what their history is. It begins, for my present 
 purpose, as far back as Ptolemy, who flourished A.D. 100-170 at 
 Alexandria. He enumerated 48 Constellations, 21 of which 
 were Northern, 12 Zodiacal, and 15 Southern. Tycho Brahe, 
 who died in 1601, added 2. Bayer (he of the Atlas) 
 added, or rather perhaps accepted as additions, 12 constella- 
 tions, all of them Southern. Royer, in 1679, added 5. Halley, 
 about the same period, added i, Robur Caroli, to commemorate 
 the oak of King Charles II. Flamsteed's maps contain 2 
 constellations, presumably invented by himself; and Hevelius 
 in 1690, added n. During the i8th century no fewer than 
 27 constellations, nearly all of them Southern, were set up by 
 Lacaille and others. Many of these 18th-century additions 
 have been either formally or informally repudiated a fact 
 which will explain names appearing in books and maps pub- 
 lished a century or so ago which are not now to be found in 
 modern maps or in modern lists. 
 
 The total embraced in the statement just made mounts up to 
 109. Even that number does not exhaust the names which have 
 
252 THE CONSTELLATIONS. 
 
 been proposed but promptly ignored. The situation was well 
 summed up once by Sir J. Herschel, who caustically wrote as 
 follows : " The constellations seem to have been purposely 
 named and delineated to cause as much confusion and incon- 
 venience as possible. Innumerable snakes twine through long 
 and contorted areas of the heavens, where no memory can 
 follow them ; bears, lions, and fishes, small and large, Northern 
 and Southern, confuse all nomenclature." 
 
 Constellation reformers have, as was to be expected, sprung 
 up at various times, but, as often happens with reformers, they 
 did not obtain much thanks. Two, however, stand out 
 especially unworthy of thanks, owing to their reckless and 
 ill-advised schemes of reform, namely, Dr. B. A. Gould 
 and R. A. Proctor. 
 
 Subject to reservations which have already been laid down, 
 the following may be offered as a brief general summary of the 
 positions of certain of the constellations relatively to one another. 1 
 
 We will start with Ursa Major, the Great Bear, the most 
 conspicuous of the constellations which never set in Great 
 Britain, Canada, and the Northern States of North America. 
 The tail and hind quarters consist of 7 brilliant stars, 4 of 
 which (a, /3, y, ), have long been compared to a waggon, the 
 other 3 (e, , ?/) being the horses ; or the 7 taken together 
 make "The Plough," a very old English name. The hind 
 wheels, or the two farthest (/3, a) from the horses, are known as 
 " The Pointers," because they point to the Pole-star (a Ursas 
 Minoris) at the tip of the Little Bear's tail ; and farther on 
 straight ahead to the constellations Cepheus and Cassiopeia, 
 situated in the Milky Way where it is nearest the Pole. 
 Cassiopeia includes several bright stars so grouped that they 
 form the letter M or W, according to the aspect in which they 
 are viewed. The two most northerly wheels of the waggon 
 (8 a, Ursae Majoris) point to the bright star Capella (a Aurigae), 
 which is also circumpolar in our latitudes. 
 
 1 Condensed from my Handbook of Astronomy , vol. iii. 
 
CONSPICUOUS ISOLATED STARS. 253 
 
 The stars in Ursa Major may be usefully employed as scales 
 of distances for degrees of arc. The nearest "pointer" (a) is 
 28| from the Pole ; from a to /3 is 5 ; from )8 to y is 8 ; from 
 y to 8 is 4^ ; from 5 to e is 5^ ; from to is 4^ ; from to rj 
 is 7 - 1 
 
 Descending diagonally across the heavens along the Milky 
 Way from Cassiopeia towards Capella we come to a Persei, and 
 a little farther on we find the variable Algol (/3 Persei) ; if we 
 pass across the Milky Way in the opposite direction we shall 
 arrive at a Cygni, whilst beyond this and a little out of the 
 Milky Way is Vega (a Lyrse). Draco includes a long chain of 
 stars sweeping partly round the Little Bear ; and in the space 
 bounded by Cassiopeia, Cygnus, and Draco, is Cepheus. 
 
 Another very conspicuous group in the Northern Hemisphere 
 is that known as "The Square of Pegasus." Near y Pegasi, 
 and pointing directly towards it, are two conspicuous stars in 
 Andromeda (a /3), and a third (y) is a little beyond them. 
 Andromeda, as a constellation, will be readily known by the 
 connection of its a with the 3 stars of Pegasus (a, /3, y) which 
 make up the Pegasus " square." 
 
 An imaginary line through the Great Bear and Capella will 
 reach in a forward direction the Pleiades ; and then, turning a 
 right angle towards the Milky Way, will reach Aldebaran (a Tauri) 
 and the shoulders, a, y, of Orion. Orion is the most striking 
 constellation in the whole heavens, comprising as it does so 
 
 1 The lack of astronomical knowledge in high places is amusingly and 
 strikingly brought out in a recently published book by Professor James Stuart. 
 Alluding to conversations he had had with Mr. Gladstone, he says : "It was 
 on one of these occasions, on a bright starlight night, that Mr. Gladstone said, 
 when he had been looking at the stars, ' Why is it that the Great Bear seems 
 so much more frequently in the sky than other constellations?' I said, 
 ' Because it never sets.' He said, ' Do you mean to say that it never sets? I 
 thought all the stars rose and set.' When I explained the matter to him it 
 seemed somewhat of a new idea, and he said, 'Well, I think that explains 
 Homer's phrase, 6i|/e Svwv, if applied to the Great Bear that is to say, " late in 
 going down."' Mr. Gladstone was never anything of a physical scientist." 
 J. Stuart, Reminiscences, London, 1912, p. 240. 
 
254 THE CONSTELLATIONS. 
 
 many conspicuous stars, namely, a, -y, in the shoulders, 5, e, in 
 the belt, and K and )8 in the legs. Aldebaran is a star of reddish 
 tint, and the most prominent in the V-shaped cluster of the 
 Hyades, which is not far from the Pleiades. Aldebaran, the 
 Pleiades, and Algol make the upper, while a Ceti with Aries 
 form the lower points of a W. The head of Aries is denoted 
 by two principal stars (a, $). 
 
 A line from the Pole-star taken midway between the Great 
 Bear and Capella passes to a and 3 Geminorum, the two well- 
 known stars Castor and Pollux ; continued southwards it will 
 meet Procyon (a Canis Minoris). From thence, by bending the 
 line across the Milky Way and carrying it as far again, it will 
 reach Sirius (a Canis Majoris) and so southwards to a Columbas 
 Noachi. 
 
 Algol and a and /3 Geminorum point at Regulus (a Leonis) 
 the Lion's heart, at one end of an arc with /3 Leonis, the tuft of 
 the Lion's tail at the other end. S. of and preceding Regulus 
 is Cor Hydras (a), the space between them being occupied by 
 Sextans. 
 
 The Pole-star and the middle horse of the Great Bear (<T) 
 direct us to Spica (a Virginis) at a considerable distance, whilst 
 beyond and in the horizon will be Centaurus. 
 
 The Pole-star and the first horse of the Great Bear (77) point 
 nearly to Arcturus (a Bootes), which forms with Spica and 
 Regulus a splendid triangle. In a southerly direction another 
 triangle is formed by Arcturus, Spica, and Antares (a Scorpii). 
 
 Corona Borealis is nearly in a line between Vega (a Lyras) 
 and Arcturus (a Bootis), whilst the head of Hercules and the 
 head of Ophiuchus lie between Lyra and Scorpio. In the 
 Milky Way, below the part nearest to Lyra, and on a line drawn 
 from Arcturus through the head of Hercules, is Altair (a Aquilas), 
 which makes, with Vega and a Cygni, a conspicuous triangle. 
 Closely following Aquila is Delphinus, a small constellation with 
 9 rather conspicuous stars. 
 
 Two of the stars in " The Square of the Pegasus," already 
 
THE ZODIACAL CONSTELLATIONS. 255 
 
 mentioned 03, a), point, at double their distance, southwards to 
 Fomalhaut (a Piscis Australis). 
 
 The line of the Ecliptic may without difficulty be traced by 
 the eye by means of the stars now to be enumerated. Not far 
 from the Pleiades are the Hyades and Aldebaran (a Tauri), a 
 little S. of the Ecliptic. To the N.W. of Aldebaran, at some 
 distance, is the chief star of Aries (a), whilst to the N.E. of 
 that star are a and /3 Geminorum. Regulus (a Leonis) is on 
 the line of the Ecliptic, and Spica (a Virginis) is only a little 
 S. of it. The Ecliptic thus known, the zodiacal constellations 
 may be easily distinguished in their successive order from W. 
 to E. Thus Aries lies immediately between Andromeda on 
 the N. and Cetus on the S., the 3 constellations reaching 
 nearly from the horizon to the zenith ; Taurus will be recognised 
 by the Pleiades, Aldebaran (a) and the Hyades ; Gemini by 
 Castor and Pollux, (a, j3) ; Cancer, the highest, or most northerly 
 of the signs, by the cluster Prassepe, but as a constellation, 
 having no stars larger than /3, and that only of mag. 3! ; Leo 
 from the stars Regulus (a) and Denebola (/3) ; Virgo by Spica (a) ; 
 Libra by /3 (which, however, is only of mag. 2|) ; Scorpio by its 
 brilliantly red star Antares, and 9 other stars of the 3rd magni- 
 tude, or brighter ; Sagittarius, the lowest or most southerly of 
 the signs, with its e of mag. 2 ; Capricornus, with its 8 of mag. 3 ; 
 Aquarius, under the neck of Pegasus, with no stars as bright as 
 mag. 3 ; and Pisces, between Pegasus, Andromeda, and Cetus, 
 also with no bright stars. 
 
 It must be understood that the foregoing paragraphs are very 
 rough as regards the information they give, and do not embrace 
 the constellations of the Southern hemisphere, which are invisible 
 in England. 
 
CHAPTER XIV. 
 TELESCOPES. 
 
 Telescopes are of two kinds. Reflectors, Refractors. Various kinds of 
 reflectors. Brief description of each. Principle of a refractor. 
 Spherical aberration. Chromatic aberration. The opera-glass. 
 Stands for telescopes. Importance of a good stand. Equatorial 
 stands. Advantages of an equatorial mounting. Accessories to 
 a telescope. Driving-clock. Sidereal clock. The housing of a 
 telescope. Advantages of an observatory. Detailed description of 
 how to build one. 
 
 THIS chapter is not intended to be either a treatise on optics, or 
 even a full statement of the different classes of instruments 
 used in astronomy. 
 
 I only purpose to offer some information likely to be useful to 
 amateurs able and willing to give a certain amount of time and 
 lay out a moderate amount of money in the purchase of instru- 
 ments suitable for observing some of the more easy celestial 
 objects which have been described in the preceding pages. 
 
 TWO KINDS OF TELESCOPES. 
 
 Telescopes are of two kinds ; and there is a radical difference 
 between them. In a " Reflector " the rays of light coming 
 from a distant object are received on a curved surface of metal, 
 or silvered glass, and reflected back to a " focus," where they 
 are viewed by a subsidiary piece of optical apparatus in the 
 nature of a microscope, and which is called an " eye-piece." 
 In a "Refractor" the rays of light are received by a glass 
 256 
 
REFLECTING TELESCOPES. 257 
 
 lens, through which they pass, and, after passing, are brought to 
 a point called a " focus, 3 ' where they are viewed by what I have 
 called a sort of microscope, though its proper name is " eye- 
 piece," as already given. 
 
 To compare reflectors and refractors as regards their relative 
 merits is not altogether easy, because measurements in feet 
 and inches of each are not comparable. A reflector 6 inches 
 in diameter is an instrument altogether different from a refractor 
 of the same dimensions. Such a reflector is less efficient, and 
 less handy, but, it must be admitted, is also less costly than its 
 refractor brother ; but, notwithstanding these facts, I do not 
 recommend reflectors, for several reasons, and one in particular. 
 The mirror, which constitutes the essential feature of the 
 reflector, is difficult to keep in condition ; that is to say, however 
 good its condition at the start, it sooner or later gets out of 
 condition. If it is of polished metal it soon tarnishes, if of 
 silvered glass it gets dull, and in either case it is troublesome 
 to get at either for moving or cleaning. 
 
 As between one reflector and another, it must be explained 
 that there are some differences which make reflectors of one 
 type not quite so unhandy as those of another type. There are 
 4 principal types of reflector in use, namely, the " Gregorian," 
 the " Cassigranian," the " Newtonian," and the " Herschelian." 
 The 2 former of these are the least inconvenient to use because 
 the mirrors, which are at the eye-end of the tube, being pierced 
 in the centre, the observer looks straight at his object, whereas 
 in the Newtonian and Herschelian forms the eye-piece and the 
 observer are at the side of the tube, and therefore there has to 
 be a diagonal reflector inside ; and the observer, every time he 
 wishes to look with the naked eye at the object he is observing, 
 has to twist his body round. A Herschelian reflector, especially 
 if it is a large one, is still more troublesome to work, because 
 the eye-piece is up in the air, and therefore the observer must 
 be there also. However, Herschelian reflectors are quite 
 obsolete, and this, to some extent, is true of the Gregorian and 
 17 
 
258 TELESCOPES, 
 
 Cassigranian forms. The real competition nowadays is between 
 Newtonians and refractors, and a purchaser will have to exercise 
 his own discretion in making a choice, and in many cases will 
 be swayed by the apparently cheaper price of the Newtonian, 
 whilst ignorant of its drawbacks, some of which have been 
 stated. It must, however, be confessed that the substitution in 
 recent times of comparatively light silvered-glass mirrors for 
 the old-fashioned heavy metal mirrors has done something to 
 popularise the Newtonian reflectors of moderately large size. 
 
 A refractor takes its name from the fact that it receives light 
 from an object on the outer side, and brings it nearly to a point 
 called the " focus." Such a telescope, in its simplest form, 
 consists merely of a double convex lens at one end of a tube, 
 which forms an image of the object to be viewed, whilst a 
 second and smaller double-convex lens, fixed at the other end 
 of the tube, serves as a simple microscope to magnify the 
 image formed by the first lens. The first is called the "object- 
 glass," whilst the magnifying lens is called the "eye-piece." 
 This is stating the matter in its broadest and most elementary 
 shape, and, though it is quite possible to construct a telescope 
 with only two pieces of glass combined as stated, practically 
 it is desirable to arrange things a little more elaborately. Two 
 simple lenses combined as above reveal certain optical incon- 
 veniences called " spherical aberration " and " chromatic aber- 
 ration." The result of spherical aberration is that the object 
 does not come to as sharp and defined a focus as is desirable, 
 whilst chromatic aberration is indicated by the fact 'that the 
 image of the distant object on view is inconveniently fringed 
 with colour. These two drawbacks, which, when a large lens 
 is used for an object-glass, are very serious, are " corrected " 
 (as the expression is) by making both object-glass and eye- 
 piece compound instead of simple ; that is, by forming both 
 object-glass and eye-piece of two lenses instead of one. 
 
 On the right disposition of these lenses, as regards the 
 curvature given to them, depends the success or failure of the 
 
ELEMENTARY IDEAS. 259 
 
 optician's efforts to cure the inconveniences referred to. All 
 this, however, is very technical, and does not concern the 
 general reader, who buys his telescope with all these points 
 worked out by the optician, and he has nothing to do with 
 them except to pay his purchase-money on the supposition 
 that they have been properly dealt with. In all cases, however, 
 an intending purchaser will do well to consult an expert friend, 
 if he has one within reach, in order to ascertain that both the 
 optical part of his proposed purchase and also the metal 
 working-parts are all satisfactory. 
 
 Up to this point I have been talking of the telescope in its 
 simplest form, but it must be borne in 'mind that, short of 
 a telescope properly so-called, a not inconsiderable amount of 
 useful and profitable astronomical study can be accomplished 
 by the aid of a common opera-glass, binocular, or field-glass. 
 This especially applies now and again to observations of comets, 
 eclipses, and occultations. An opera-glass, of course, is naught 
 else but 2 small telescopes placed side by side, one for the use 
 of each eye. Such an instrument, in its common form, starts 
 with an assumption which is frequently contrary to the fact, 
 namely, that both eyes of an observer are alike, and that what 
 suits one eye will suit the other eye. This is often not the 
 case, and accordingly in the better-made and higher-priced 
 binoculars provision is made, not only for eyes being different, 
 but for the centres of the eyes of one person being at a 
 different distance apart compared with the eyes of another 
 person. 
 
 In making preparations for carrying on astronomical obser- 
 vations the question turns entirely at the outset on the money 
 available for providing the outfit. Of course, this may be 
 anything from ,5 up to ,5000. But what I have in view 
 in these pages is an effort to assist in a very modest outlay 
 say, anything between $ and ,100 leaving the question of 
 an apartment in which to house the instrument to stand over 
 to the end of this chapter, and be dealt with separately. 
 
260 TELESCOPES. 
 
 STANDS FOR TELESCOPES. 
 
 When asked, as I often am, to give advice as to the purchase 
 of a telescope one point invariably crops up the difficulty of 
 impressing on an inexperienced purchaser the importance of 
 providing his telescope, whatever its size or price, with a 
 suitable and efficient stand. If the aperture of the telescope 
 is to be no more than 2 inches, and the cost perhaps ^10, 
 the only stand which such a telescope would have, or want, 
 will be a tripod of some sort, either entirely of brass to stand 
 on a table (known as a ** pillar-and-claw stand "), or of metal 
 and wood combined to stand on the ground. Such an in- 
 strument will have 2 motions, up and down and right and left. 
 Now these motions, quite convenient and suitable when the 
 objects to be looked at are terrestrial, are very inconvenient 
 and unsuitable in dealing with celestial objects, and for this 
 reason : the stars moving across the sky by virtue of the 
 diurnal motion (as explained in Chapter XL, ante} do so 
 diagonally (or on the skew), and a telescope which normally 
 moves up and down and right and left does not readily lend 
 itself to moving askew. 
 
 EQUATORIAL STANDS. 
 
 A telescope mounted so as to follow the movements of the 
 stars requires to be tilted so that the main part of the stand 
 shall point exactly to the Pole. This secured, then one pushing 
 motion of the telescope incessantly from left to right will keep 
 any star once brought into the field of view continuously in 
 view, so long as the pushing motion lasts. In other words, the 
 stand which we started with, whose technical name is an 
 " Alt- azimuth," has been converted by being tilted into an 
 " Equatorial." Various expedients for this conversion have 
 often been suggested, but they are rough and troublesome, 
 and the intending purchaser of a telescope had much better 
 
STANDS FOR TELESCOPES. 
 
 26l 
 
 begin at the outset by buying a properly devised " Equatorial 
 Stand," as an apparatus for following the star by one move- 
 ment is technically called. 
 
 The various stands which are illustrated in this chapter will 
 show the progressive developement of stands, from the smallest 
 and humblest 
 " pillar- and- 
 claw " up to the 
 largest and 
 most costly 
 equatorials 
 of world - wide 
 celebrity. It is 
 not contem- 
 plated to give 
 any detailed 
 account of these 
 large instru- 
 ments, but 
 only to make 
 the reader 
 acquainted with 
 such develope- 
 ments of im- 
 provements and 
 accessories as 
 will keep the ex- 
 penditure within Fig. 316. Astronomical and Look-out Tele- 
 the limits, more scope ("Pillar and Claw"), 
 
 or less, of ;ioo. 
 
 Two things come up for consideration as soon as we have 
 decided on mounting the telescope as an equatorial, (i) Shall 
 the stand be portable, or be a fixture somewhere ? And (2) shall 
 the pushing motion required to keep an object constantly in 
 the field be given by hand or automatically ? 
 
262 TELESCOPES. 
 
 As regards the stand to carry an equatorial, such stands, in 
 the form of wooden tripods, are easily portable when they are 
 required to carry telescopes of no more than about 4 in. of 
 aperture. But an equatorial is shorn of its special usefulness 
 if unprovided with setting circles, such as are required to bring 
 it to a point in the heavens whose R.A. and Declination are 
 known. Even without circles an equatorial stand is wasted if 
 some fixed marks are not available on the ground out of doors 
 on which to place the 3 feet of the tripod so as to ensure the 
 main axis of the instrument pointing to the Pole, which is the 
 essential principle of the thing. 
 
 This difficulty of how to avoid the inconvenience of having 
 no assigned position in which to set up the tripod, after each 
 time it is removed, is sometimes met by an observer erecting 
 in his garden an iron stand as a permanency, and taking out 
 into the open air only the head which constitutes the equatorial, 
 together with the telescope, every night whenever he proposes 
 to do work. This condition of things secures a certain amount 
 of exactitude in getting his equatorial into its proper place for 
 use ; but it is quite evident that, to carry backwards and for- 
 wards between a house and a garden a telescope, and the 
 important parts of its stand, every night that it is wanted is 
 alike a time-taking, and, for various reasons, an unsatisfactory 
 procedure. It is better by far not only to have a fixed stand, 
 but to keep the equatorial head, and likewise the telescope, 
 permanently in place, and cover the whole by a structure of 
 some sort which may be called either a shed with a movable 
 top or an observatory with a revolving dome, which obviously 
 sounds much better. 
 
 ACCESSORIES TO A TELESCOPE. 
 
 With an instrument properly housed it becomes possible to 
 add, not necessarily at first, if funds do not permit, but later 
 on, a driving-clock. This is simply an arrangement of clock- 
 
EQUATORIAL STANDS. 
 
 263 
 
 work which, when coupled on to the telescope by suitable 
 
 means, drives or pushes the telescope continuously forwards, 
 
 so as to keep the object which is under observation continuously 
 
 in view without 
 
 the necessity of 
 
 the observer 
 
 constantly 
 
 having to push 
 
 the telescope a 
 
 labour which is 
 
 not only very 
 
 tedious, but one 
 
 which hinders 
 
 him using his 
 
 hands for 
 
 making notes or 
 
 drawings. 
 
 With a tele- 
 scope equatori- 
 ally mounted, 
 and provided 
 with setting 
 circles and 
 driven by clock- 
 work, a time- 
 piece will be 
 required ex- 
 hibiting sidereal 
 time ; in other 
 words, announc- 
 ing what is the 
 
 Hour of R.A. which is on the meridian at any given moment. 
 Of course, a properly constructed sidereal clock, graduated 
 to 24 hours, is desirable, but it is a luxury ; and a common 
 French dining-room clock, costing 2 or ; ^3, answers the 
 
 Fig. 317. 3-inch Portable Equatorial 
 Telescope. 
 
264 TELESCOPES 
 
 purpose of a sidereal clock if it keeps fairly good time, 
 and if the owner is able to obtain Greenwich time every day 
 or two from a local post-office or otherwise. In my early 
 days as a young astronomer I did a great deal of work with 
 such a clock during several years, and had no difficulty in 
 picking up in the heavens any object I wanted to find, so 
 soon as I had obtained sidereal time from my make-shift 
 clock, the setting circles of my instrument being in good 
 adjustment. The methods of adjusting an equatorial to fit 
 it for work must be sought for in books specially written for 
 the purpose. 1 
 
 THE HOUSING OF A TELESCOPE. 
 
 What some people would call a telescope-house, as they would 
 speak of a motor-house or a chicken-house, is scientifically 
 called an "observatory." Having had some practical ex- 
 perience in the construction of observatories suitable for 
 amateurs, in 3 cases for myself and in several cases for 
 friends, it has occurred to me that the usefulness of this book 
 would be increased if it contained some practical hints and 
 suggestions for the guidance of those who possess, or who 
 intend to acquire, a telescope large enough and good enough 
 to be worth a permanent fixed shelter. 
 
 My first essay in this direction was in 1866, when I put up 
 at Sydenham a wooden observatory, 10 ft. square, with a 
 revolving roof and walls, wholly constructed of timber, the 
 roof and walls being covered with weather-boards screwed to the 
 jointed timbers. I will not further describe this structure, the 
 builder's charge for which was ^58, because I have much more 
 recently erected at Sydenham what is more or less a facsimile 
 of it, with some alterations and improvements suggested by the 
 
 1 See, for instance, my Handbook of Astronomy, vol. iii., " Astronoinical 
 Insiruments." 
 
FIG. 318 
 
 PLATE CXII, 
 
 264] 
 
FIG. 319 
 
 PLATE CXIII. 
 
 
 Equatorial Telescope, with Object-glass of 10 inches 
 
 aperture (Cooke). [265 
 
TELESCOPE-HOUSES. 265 
 
 experience of years. Suffice it to say, regarding the 1866 
 observatory, that when circumstances compelled me to go and 
 reside in a different part of the country, I at once found a 
 purchaser for it, who was much struck with the ease and 
 facility with which the whole was taken to pieces and conveyed 
 into Hampshire. 
 
 In 1869 I went to live in a house at Bickley which had a 
 tower, and, by arrangement with my landlord, I supplied, as the 
 roof of the tower which he built, a revolving dome to cover a 
 4~in. Cooke equatorial. This dome was of wood, weather- 
 boarded, and of practically the same design as the roof erected 
 3 years previously at Sydenham. 
 
 Moving to East Bourne, in 1874, to a house of my own, built 
 after my own plans, I provided a tower about 50 ft. high as part 
 of the house, the topmost story of which was built and fitted 
 up as an observatory, surmounted by the wooden dome brought 
 from Bickley. This eventually covered a 6-in. Grubb equatorial, 
 with which instrument I carried on observations during a 
 period of 28 years. 
 
 My reason for making the top of the tower appurtenant to 
 the house into an observatory was because my 5 years' ex- 
 perience at Bickley taught me the great advantage of so 
 doing. 
 
 Inducements to observe in cold, wintry weather are very 
 much more effective when the observer is able to walk to and 
 from his observatory under cover ; compared with a different 
 state of things which he has to face when it is a question of 
 dressing up in a greatcoat and other things preparatory to 
 walking any number of yards in the open air, possibly over 
 damp grass, or through snow. 
 
 Many years ago a writer in Nature made a ridiculous 
 attack on my plea for putting a movable dome on the top of a 
 high tower, such as mine at East Bourne, because, sooner or 
 later, the said roof would be found to have descended into the 
 garden. How baseless this writer's foolish opinion was, is 
 
266 TELESCOPES. 
 
 sufficiently shown by the fact that my dome passed unscathed 
 through 32 winters and summers at East Bourne in a situation 
 very much exposed to the full force of south-westerly gales, 
 whenever they occurred, no other precautions being taken than 
 two ties of not very thick rope. Only once, during the whole 
 long period named, did I ever see the dome rise off its ball- 
 bearings to an extent suggesting that, if the rope had not been 
 there, it might have gone overboard. As a matter of fact, 
 often for many weeks and months together I neglected to tie 
 the rope, and nothing happened. 
 
 I proceed now to describe my fourth observatory, to be seen 
 at Sydenham, which, as I have said above, embodies previous 
 experiences. Its revolving dome (by the way, it is not a dome 
 but a 13-sided polygon) has occupied in more than 40 years 
 three different sites, and its timbers, without even the exception 
 of a square inch of surface, are as sound and as good as on the 
 day on which they left the carpenter's shop at Uckfield, in 
 which they were originally put together. This last-named fact 
 I attribute entirely to the circumstance that, instead of following 
 the usual trade custom of giving outside woodwork 2 or 3 
 coats of paint all at once at long intervals of time, I made it a 
 rule, as far as possible, to put on a single coat of paint something 
 like every second year. 
 
 It will be useful to explain the successive steps involved 
 in the erection of an observatory, taking the reader through 
 the actual modus operandi based on the fiction that I am 
 describing an entirely new structure, and not one a portion 
 of which had actually been erected previously somewhere 
 else. 
 
 A good solid foundation is a sine qua non to start with, for 
 without it a telescope of any considerable weight will constantly 
 be getting out of adjustment, even though there may be no risk 
 of it and its house toppling over. The extent of the care which 
 it is expedient to spend over foundations is largely a geological 
 question. A rocky, gravel, or chalk soil is usually very stable, 
 
FIG. 320 
 
 PLATE CXIV. 
 
 Standard Photographic Equatorial, for the International Survey 
 of the Heavens (Sir H. Grubb). 
 
 266] 
 
FIG. 321 
 
 PLATE CXV. 
 
 27-inch Refractor of the Vienna Observatory (Sir H . Grubb). 
 
 [267 
 
A SIMPLE OBSERVATORY. 267 
 
 except that rock is often very susceptible to changes of tem- 
 perature, but this would not, as a rule, involve inconvenient or 
 dangerous settlements. It is far otherwise, however, with a 
 clay soil. This is a very trying soil to deal with where the 
 stability of a structure of great weight has to be secured in a 
 limited area, such as the pier of an equatorial weighing any- 
 thing from a quarter of a ton to 2 or 3 tons. The soil at 
 Sydenham is a stiff clay, which at different seasons of the 
 year is either very wet and sticky or hard and dry and full of 
 fissures. Accordingly, to prepare for an observatory the plan 
 of which was to be a square 10 ft. on each side, I excavated a 
 space 1 2 ft. square and 9 in. deep, and filled the same with 
 77 navvy barrow-loads of cement-concrete composed of broken 
 stone, fragments of brick, old glass, and crockery, and indeed 
 of any hard rubbish for which I had no use, and which I wanted 
 to get rid of. 
 
 This concrete foundation was left untouched, as it happened, 
 for about 3 months, an interval amply sufficient, of course, to 
 test its stability. On this concrete bed, a square enclosure of 
 brickwork was built in the form of a dwarf Q-inch wall of 8 
 courses of bricks, the topmost one being formed of bricks 
 on edge set in cement. 
 
 Of course it will be understood that so extensive a concrete 
 foundation as that which I provided is quite unnecessary in 
 a general way, and that the only place where concrete is 
 necessary by way of foundation is under the centre of the 
 observatory, that it may serve as a base for the brickwork 
 pillar which is to carry the iron stand of the equatorial, 
 presuming that the telescope is to be mounted equatorially in 
 the German fashion. Whether or not the walls require to be 
 built on concrete must depend on local circumstances. 
 Ordinarily it will not be necessary for observatories of the 
 type with which this section is intended to deal. 
 
 I will now give particulars of my foundations. I may as well 
 remark that the large quantity of rough core which I used was 
 
268 TELESCOPES. 
 
 rather because I had it and wanted to get rid of it, than because 
 it was really necessary. 
 
 FOUNDATIONS. 
 
 The following are particulars of the foundations, and of the 
 cost of the same : 
 
 s- d. 
 
 Excavation of 108 cubic feet (labour) . . . o 12 o 
 Concrete : 
 
 77 barrow-loads of broken stone, etc. . I 10 o 
 
 5 bags of cement 16 o 
 
 Labour 170 
 
 45 
 
 BRICKWORK IN WALLS AND FLOOR. 
 
 The foundations being finished, the next thing to be done 
 was to build a dwarf wall running round four sides of a square 
 loft, across. This wall received, in my case, only the four-sided 
 wooden frame which constituted the walls of the observing- 
 room; but in ordinary cases this wall would be called upon to 
 carry the joists of the floor of the said room. I preferred, how- 
 ever, at Sydenham not to have a wooden floor, but to form a 
 floor by means of an additional layer of concrete, rising about 
 6 in. inside the quadrangular enclosure formed by the brick wall 
 and brought to a smooth surface by cement. The advantage 
 of such a surface for an observatory floor is the facility with 
 which observing chairs or stools, or indeed seats of any kind, 
 can be pushed hither and thither ; for a boarded floor, especially 
 one formed of imperfectly seasoned boards (as is often unavoid- 
 able when economy has to be considered), is very inconvenient 
 and disagreeable. A concrete floor is, moreover, more easily 
 cleaned and kept clean. The one only objection is that it is 
 cold to the feet, but this can be got over by having a mat or 
 
FIG. 322 
 
 PLATE CXVI. 
 
 Eye-end of the Vienna Refractor. 
 
 268] 
 
FIG. 323 
 
 PLATE CXVI1, 
 
 30-inch Refractor of the Pulkova Observatory (Repsold}. 
 
 [269 
 
DETAILS OF A SIMPLE OBSERVATORY. 269 
 
 two, capable of being moved from place to place at pleasure. 
 The following was the cost of the 
 
 CONCRETE FLOOR. 
 
 s. d. 
 
 34 barrow-loads (say 50 cubic feet) of coarse, 
 
 broken stone . . .'--. . . . r 14 o 
 31 barrow-loads of small broken stone, or gravel . I 18 9 
 Mortar, composed of 6 barrow-loads of sand, i|- 
 
 bags of lime, and a little cement . . .067 
 5 bags of cement for top dressing . . . .100 
 Labour 2710 
 
 The above cost includes a few bricks, and some cement and 
 labour, for fixing the door-frame, building the pillar for the 
 equatorial stand, and two steps outside the observatory. 
 
 The lower walls were formed, as has been already stated, of 
 8 courses of red bricks in 9 in. work, the topmost course being 
 bricks on edge. The two first courses in the ground were of 
 common stock bricks, being cheaper than the Sussex red bricks. 
 The pier to carry the equatorial was circular and raised 
 21 inches above the surface of the floor, and was surmounted 
 by a circular piece of York stone. 
 
 The cost of this brickwork, exclusive of the pillar, may be 
 exhibited as follows : 
 
 BRICKS AND MORTAR FOR THE JOB. 
 
 s. d. 
 
 1 100 red bricks 3 5 o 
 
 200 stock bricks . . . . . . .070 
 
 18 barrow-loads of sand (ITJ cubic yards) . . o 12 o 
 4| bags of lime (| cubic yard) . . . . o 4 10 
 
 Labour 3 16 o 
 
 S 4 10 
 
 We have now to consider the upper (wooden) walls of the 
 observatory. These are formed of upright and horizontal 
 
270 TELESCOPES. 
 
 timbers, 4 inches square in section. The uprights are 12 in 
 number, tied together at the top, in the middle, and at the 
 bottom. The actual construction consists of 4 frames put 
 together in the first instance as independent frames and then 
 joined together by strong bolts with nuts. All the frames are 
 6ft. high; 2 of them are loft. 8 ins. long and the other 2 
 (which fit into these) are loft, long, so that when all 4 are 
 fastened together, and in their places, the external length of 
 each side of the square is 10 ft. 8 ins. Each of the sides is tri- 
 sected by means of the uprights. In the centre third of one 
 side a door is hung. The upper half of the centre third of 
 2 of the other sides is appropriated to a window, whilst the 
 fourth side is covered throughout. 
 
 As regards the outer covering of the walls, I had some 
 difficulty in making up my mind. In my first Sydenham 
 observatory the walls were weather-boarded, and painted 
 inside and out. Weather-boarding is a perfectly satisfactory 
 method of covering a frame, but at Sydenham, in 1908, I 
 decided on using galvanised corrugated iron, as much more 
 quickly put up and much cheaper. I considered the possibility 
 of using uralite, but rejected it, as I found that the fixing of it 
 would be troublesome. In an observatory erected in the Isle 
 of Wight by a relative of mine, and on very much the same 
 principles of construction, the outer covering of the frame-work 
 was upright match-boarding, with the usual grooves and 
 tongues. This also is a perfectly satisfactory covering where 
 time and cost have not to be studied, and where material of 
 good quality can be obtained. In my Sydenham observatory 
 the frames are not covered at all inside, and I think they are 
 best left uncovered. Of course, the effect of covering the 
 framework is pleasant to the eye, but on the other hand it 
 renders more difficult the problem of keeping the inside and 
 outside temperature of an observatory equable, which is a 
 matter of much importance, to secure the good definition of 
 objects seen through any telescope. , 
 
FIGS. 324-325 
 
 PLATE CXVIII. 
 
 I 
 
 o 
 
 EC 
 
 II 
 
 CM X 
 
 oo 
 
 IS 
 o o 
 
 .2 
 
 $ 
 
 270] 
 
FIG. 326 
 
 PLATE CXIX. 
 
 36-inch Refractor of the Lick Observatory (Warner & Swasey}. 
 
 [271 
 

 FURTHER DETAILS. 27 1 
 
 UPPER WALLS. 
 
 * d. 
 Timber frame-work, door, 2 windows . . . 8 10 o 
 
 Lock and sundry fittings 099 
 
 17 pieces of galvanised corrugated iron (6' x 2') 
 
 and screws 11211 
 
 Labour for fixing the wall-work . . . .118 
 
 ii 14 4 
 
 The entrance-door is on the N. side, and there are windows 
 on the E. and W. sides. These supply adequate light, and 
 may be regarded as away from what is normally the windward 
 or stormy points of the compass, so far at least as the South 
 of England is concerned. The windows, each about 2 ft. 
 square, open as casements, with hinges on the upper side. 
 Hung in this way, not on the right or left sides, as is usual with 
 casements, the windows, even when open, do not generally 
 allow rain to blow in if it should so happen that they have been 
 left open and rain comes on during the observer's absence. 
 
 Use is made of the transverse ties of the framework of the 
 walls by treating several of them either as they are, as shelves, 
 or as supports for shelves of greater width than the 4 in. 
 of the ties themselves ; but 4 in. is quite sufficient for a shelf 
 to accommodate most of the loose articles which are required 
 inside an observatory, except the larger books and such things 
 as boxes containing eye-pieces, etc. 
 
 The clock is placed in the S.W. angle of the observatory. 
 It may be described as a very good ordinary regulator, 
 showing, of course, sidereal time, with a secondary dial gradu- 
 ated to 24 hours. It was made by a very first-rate London 
 clockmaker, now deceased, who, I think, had never heard of 
 a sidereal clock ; anyhow, had never made one until he made 
 mine under my supervision. It cost ^28, and often goes for 
 many weeks with a rate of about a second a day not bad, for 
 what I may call a merely civilian clock. 
 
272 TELESCOPES. 
 
 At East Bourne I used to rate it by means of a transit 
 theodolite discarded from the Ordnance Survey, and which I 
 therefore picked up cheap ; but now at Sydenham I have no 
 transit instrument, or even a substitute for one, as I find it easy 
 enough to convey the time from the Westminster clock every 
 few days by means of a good watch with a second's hand. 
 This celebrated clock, as is well known, is seldom more than 
 i second wrong. The time thus obtained and imparted to my 
 clock after an interval of an hour or two is never sufficiently 
 wide of the exact time to cause any difficulty in finding a 
 celestial object by means of the equatorial, my meridian being, 
 it is to be remembered, only by a very little difference W. of 
 Greenwich. 
 
 Proceeding onwards, and, as a literal fact, upwards in the 
 construction of the observatory, the next and, in a certain 
 sense, final matter is the roofing-in, and this is the most 
 difficult and troublesome matter of all. It is so because a 
 revolving top (commonly called a dome, though in small ob- 
 servatories it is seldom such), the plan of which is a circle, or 
 a polyhedron rising from a circle, has to be arranged to work 
 on the top of the square of the walls. It is in effect a circle 
 inscribed in a square, to use the language of geometry, which 
 has to be dealt with, and it is self-evident that the circle must 
 be so contrived that it has a bearing on the middle of the 
 straight sides of the square, which means, of course, that 
 the 4 corners of the square obtain no cover from the domed 
 roof. 
 
 In order to obtain as stable a bearing for the dome as possible, 
 the angles of the wall-frames are tied by substantial pieces 
 of timber, which convert what was a quadrangle into a not 
 quite regular octagon. If this conversion is judiciously carried 
 out by the joiner the effect is that the revolving dome is pro- 
 vided with a substantial bearing which is practically circular 
 and continuous. 
 
 The corners mentioned above as exposed to "the sky have 
 
FURTHER DETAILS. 273 
 
 to be filled in with a water-tight roof. This is best done by 
 providing a triangular ceiling at each corner of match-board 
 covered with lead, turned up about 2 inches against the channel- 
 plate (to be described presently), and turned down over the 
 edge of the walls to an extent sufficient to prevent rain being 
 blown up under the lead. An overlap of 2 inches should in 
 general suffice, unless the building is in a very exposed situa- 
 tion. I have used lead, and recommend it, because it is, of 
 course, water-tight if put on by a competent plumber, and can 
 be used again if the observatory has to be removed to another 
 locality. It is true that lead is expensive, and cheaper materials 
 may be employed, such are sheet-zinc, tarred felt, and 
 painted canvas, including Willesden canvas ; but these materials 
 can never be removed for use a second time, and the 3 last- 
 named are not only perishable in a general sense, but are 
 difficult to keep in water-tight repair. 
 
 Here it may be remarked that an eaves-gutter to carry off 
 the rain which falls on the roof may perhaps be deemed by 
 some persons to be desirable, but this is a refinement which 
 I have not adopted, because the rain-water which falls on the 
 roof runs downwards more or less clear of the walls to the 
 concrete footings of the brick wall outside the building, whence 
 it finds its way, by gravitation, to an ordinary storm-water 
 garden drain some 6 feet below the level on which the observa- 
 tory is built. 
 
 FLAT PART OF ROOF. 
 
 The cost of the flat roofing at the corners just described was 
 as follows : 
 
 s. d. 
 60 ft. run of 6-in. match-boarding . . . .076 
 
 Labour (carpenter) o 19 II 
 
 71 sq. ft. of 3-lb. lead 219 
 
 Labour (plumber) 0166 
 
 Nails, screws, and other materials . . .016 
 
 18 
 
274 TELESCOPES. 
 
 THE DOME. 
 
 We now come to the most troublesome feature in every 
 observatory the construction and movement of the dome. 
 
 On the top of the 4 walls and on the continuous bearing 
 already mentioned there is fixed a circular wall-plate, as it is 
 called by the builders. This plate is formed of timber put 
 together in pieces about 2 ft. in length, so that when they are 
 all fitted together they shall make a ring 9 ft. 8 in. in its internal 
 diameter, and loft. 4 in. in its external diameter; in other 
 words, the width of the rim is 4 in. On the top of this are 
 fixed segments of a circle, 9 in number, of cast-iron, slightly 
 hollowed in the middle, with a rim i^in. high on the outside, 
 and somewhat less on the inside. Thus is formed a sort of 
 circular tramway, in which 3 or more iron spheres or old- 
 fashioned cannon-balls, about 4 in. in diameter, run. These 
 permit the rolling movement of the dome. 
 
 I have only 3 such balls for the loft, dome, but 4, or even 5, 
 might perhaps be better. They would, however, only be 
 better if they were all very truly identical in diameter. It is 
 doubtful whether 5 such balls could be obtained in simple 
 cast-iron ; they would have to be turned to a given diameter 
 in a lathe by a competent workman, which would involve a 
 good deal of extra expense beyond the cost of the simple 
 casting. Yet, unless they were true spheres and of identical 
 diameter to a nicety, they would be useless for distributing 
 the weight of the dome over the additional points of bearing 
 beyond the bearing afforded by the 3 balls with which one 
 started. 
 
 It should be added that even 3 balls have a tendency to 
 get together, however carefully they may have been started 
 with an angular interval between them of 120. I find it a 
 good plan to mark on the dome itself inside, or on the circular 
 wall-plate, points which are 120 apart, and now and again 
 to bring I ball up to one of these marks, and then see how 
 
FIG. 327 
 
 PLATE CXX. 
 
 W// %ejgg|L^ 
 
 36-inch Refractor of the Lick Observatory (Warner &> Swasey). 
 
 274 1 
 
FIG. 328 
 
 PLATE CXXI. 
 
 Eye-end of the Lick Refractor. 
 
FIG. 329 
 
 PLATE CXXII. 
 
 2746] 
 
FIG. 330 
 
 PLATE CXXIII. 
 
 [275 
 
THE ROOF OF THE OBSERVATORY. 275 
 
 far the other 2 balls have got away from what should be their 
 marks. When the displacement has become considerable it 
 should be rectified by prising up the dome (with a strong lever, 
 such as a piece of quartering), so as to set free the 2 displaced 
 balls, which can then be moved backwards or forwards to their 
 proper positions. It is obvious that if the balls get very much 
 displaced, so that, say, the interval between 2 of them has 
 become as much as 160 or 180, a very great strain is put 
 upon the dome, which will tend to overbalance itself, and come 
 down upon the iron channel-plate so as eventually not to be 
 movable at all, even under the most powerful manual pressure. 
 
 The construction of the dome is the most difficult, and indeed 
 the only difficult, part of the whole undertaking. We have, 
 first of all, to start with a cill, on which the roof has afterwards 
 to be built up. It is absolutely necessary that this cill should 
 be very strong and rigid, because it has not only to sustain the 
 weight of the rafters and roofing of the dome, but also to stand 
 the strain due to the fact that the whole of the superincumbent 
 weight rests on only 3 points (i.e. balls), and, moreover, is 
 subject to the strain which naturally arises each time that the 
 dome is pushed round on its ball-bearings. 
 
 When the diameter of the cill is no more than about 8 ft. the 
 cill may be best made of 5 or 6 layers of i-in. boarding, cut in 
 segments and glued and screwed together, the joints of each 
 one of the 5 or 6 rings thus superposed breaking joint with the 
 ring on either side of it, until the desired thickness is arrived 
 at by the requisite number of rings. On the inside of the 
 composite ring thus built up a band of sheet-iron may be 
 fastened by way of giving further stiffness. 
 
 As the diameter of my dome was more than 8 ft., to wit, 
 10 ft., I had the foundation cill of the dome constructed some- 
 what differently. Instead of its consisting of one ring of 5 or 6 
 layers of wood in contact, it consists of 2 rings, each of one 
 thickness of stout timber, 2| in, thick, separated from one 
 another by stout upright ties 7 in. long, and secured on the 
 
276 TELESCOPES. 
 
 upper side and on the lower side by coach-screws countersunk 
 on the lower side. This gives a very strong and substantial 
 compound ring on which to build up the roof. 
 
 To the underside of the foundation cill, however it may be 
 constructed, 2 concentric rings of iron are fixed by screws 
 passing through holes in the iron rings. The holes for the 
 screws must be countersunk. These rings must be carefully 
 forged, or, better still, be made of rolled iron about i in. wide 
 and ^ in. thick. The central point between these 2 rings, 
 when fixed to the wooden cill, and the central point of the 
 hollow channel in the fixed plate (already described) of the 
 main building, must coincide exactly that is to say, must be 
 circumferences of circles of absolutely identical radius. Unless 
 there is this absolute coincidence there will be great and 
 inconvenient friction when the dome comes to be turned round 
 on its ball-bearings. It is this part of the whole observatory 
 which most requires careful setting out and good workmanship. 
 
 From the upper side of what I have called the foundation 
 ring rise the rafters, 14 in number. These do not meet in what 
 is called, in an ordinary roof, the ridge-piece, but at various 
 points in a rectangular framework, about 2 ft. by I ft. 6 in., the 
 exact size depending in every case upon what is wished to be 
 the pitch of the roof, and the width, when open, of the shutters. 
 The fourth side of the rectangle is, so to speak, non-existent 
 that is to say, it is formed by a cross-bar of iron, set edgeways, 
 so as to block as little as possible of the sky when the telescope 
 is directed to that part of the sky which lies behind the bar. 
 Two shutters, meeting one another half-way, rise on hinges 
 attached to 2 adjacent rafters, which, of course, for that pur- 
 pose, are arranged parallel to one another. The rectangular 
 frame, which is supported by the rafters, constitutes a flat roof 
 to the dome. 
 
 In order that the telescope may be able, on occasions, to be 
 pointed to the zenith, this flat roof is made to open on hinges 
 at the back (i.e. away from the shutters), and is guided up and 
 
FIG. 331 
 
 PLATE CXXIV. 
 
 Equatorials under Construction at the Dublin Works, 1912 (Grubb}. 
 
 No. i for the Johannesburg Observatory ; Object-glass 26 inches. 
 276] No. 2 for the Santiago Observatory, Chili ; Object-glass 24 inches. 
 
FIGS. 332-333 
 
 PLATE CXXV. 
 
 l 
 
 IS 
 
 CO 
 
THE ROOF OF THE OBSERVATORY. 277 
 
 down by having 2 iron quadrants working through iron catches, 
 motion being imparted by a pair of ropes running through 
 pulleys inside the sloping roof. The flat roof is covered with 
 thin lead, and the hinges are protected by large pieces of 
 leather running all along the back-side, and made, as far as 
 possible, waterproof by means of paint. By the foregoing 
 arrangement the flat roof, or lid, of the dome (as perhaps it had 
 better be called) may be raised from the horizontal, through 
 90, to the vertical ; but I rarely raise it so much, not wishing 
 to strain the leather covering of the hinges. 
 
 In order to open the 2 main shutters, the lid has to be raised 
 3 or 4 in. to get it clear of the shutters. Special provision is 
 made by grooves on each side of each shutter to keep out the 
 rain, or, rather, to allow any rain which gets in to run down. 
 
 The shutters can be, and often are, arranged on a different 
 plan, whereby they do not lift but slide, one sliding to the right, 
 one to the left ; or the two are replaced by one which may be 
 constructed to slide either to the right or to the left as may be 
 wished. The lid also, in this form of construction, slides on 
 bearings of its own, formed as a framework outside the sloping 
 roof. I have never been called upon to manipulate shutters 
 arranged in this fashion, and therefore cannot speak from 
 personal knowledge of them ; but I should fancy that it was 
 more difficult with such shutters to exclude the rain than with 
 shutters such as I have at Sydenham. At any rate, my lid, 
 which was constructed to slide in this way, I had altered at 
 once to its present form. 
 
 There is yet another form of shutter which has some advan- 
 tages in windy situations. It really consists of two shutters, 
 but, instead of lifting in two halves, or sliding to the right or 
 left, as just described, it slides up and down ; and when down 
 that is, open for use, projects downwards, overhanging the 
 eaves of the building. This is very inconvenient. If up-and- 
 down shutters are to be employed at all, they had better be 
 so arranged as never to uncover more than half the opening 
 
278 TELESCOPES. 
 
 in a vertical direction. In other words, to open the observatory 
 for use, the upper half of the shutter must slide down over the 
 lower half ; or the lower half must slide up behind the upper 
 half. 
 
 This method of procedure is open to the objection (which in 
 certain temperatures of the atmosphere is very real) that it 
 limits the ventilation of the observatory, and requires a cumber- 
 some system of weights to counterpoise the shutters when they 
 go up and down ; which weights dangle about inside the 
 observatory in a way which is exceedingly inconvenient, though 
 more or less unavoidable. Besides these objections, this 
 system of shutter is much more expensive to construct, and 
 not easy to maintain in smooth and pleasant working order, 
 to say nothing of the difficulty of excluding rain and making 
 the place watertight. 
 
 The question of the material for the roof I have always solved 
 by using |-in. match-board, fastened with screws, and well 
 stopped with white lead and painted. When my observatory 
 was re-erected at Sydenham in 1908, after 37 years' exposure 
 to the weather, not one single board was found to be in the 
 least decayed or damaged so as to need replacement. Two or 
 three boards had been cracked in taking them to pieces at 
 East Bourne, but these cracks were readily made good by white 
 lead-stopping and paint. In the case of a new roof constructed 
 of boards suspected to be insufficiently seasoned, it might be 
 a good precaution to cover them with canvas, well painted on 
 both sides, and fastened down with copper tacks. 
 
 Willesden canvas, sheet copper, or zinc (without boards), may 
 also be used for the dome. I have heard Willesden canvas 
 well spoken of, but have not used it in any position exposed to 
 the weather for any length of time. The copper or zinc may 
 be of the ordinary roofing thickness, or even thinner. The 
 pieces must be cut into sectors to fit the bays of the dome. 
 Each piece must be secured at the top and bottom, and on 
 cross-battens, with copper or zinc nails ; but the sides must be 
 
I-IGS. 334-337 
 
 PLATE CXXVI. 
 
 20-ft. Papier-mache Dome 
 erected at the Royal Observatory, 
 Cape Town, with opening extend- 
 ing beyond the Zenith (Grubb). 
 
 Barcelona University (Grubb). 
 
 15-ft. Papier-mache Dome, 
 mounted on iron-framed Ob- 
 servatory covered with wood 
 
 (Grubb). 
 
 2781 
 
 Papier-mache Dome of 37-ft. 
 diameter, erected at Calton Hill 
 Observatory, Edinburgh (Grubb), 
 
FIGS. 338-340 
 
 PLATE CXXVII. 
 
 o .1' 
 
 
 [279 
 
FURTHER DETAILS OF THE ROOF. 279 
 
 counter-lapped (not soldered) in order to allow for expansion 
 by summer heat. Patterns for the sectors must be prepared 
 in brown paper after the frame of the dome has been put 
 together. 
 
 Dome : 
 
 J. d. 
 Contract price of dome, including iron rings and 
 
 iron channel-plate . . . . . 30 18 II 
 
 Labour : carpenter putting same together at 
 
 Sydenham . . . . . . I 19 8 
 
 32 18 7 
 
 Adding together all the items given previously under their 
 various heads (about .69), it may be taken that the Sydenham 
 observatory, as it stands, represents a cost of, as nearly as 
 possible, ^70, after adding the value of some etceteras which 
 I did not have occasion to buy specially. The cost of -repro- 
 ducing it de novo might be more, because of the rise in the 
 price of labour and materials since the dome was constructed 
 in 1869 ; but, on the other hand, several pounds might be saved 
 in the foundations. 
 
 Thus far I have been describing what I have, more or less, 
 done myself, or what has been done under my own direct 
 supervision ; but I am prepared to find that many of my present 
 readers will think that my observatory, as it now stands at 
 Sydenham, is too solid ; in other words, has been too costly 
 for the purposes of amateurs of moderate means and ambition, 
 though it was far from my intention to spend on it more than 
 I could help. 
 
 I fear there might be some foundation for this criticism, and, 
 accordingly, I would recommend, as an alternative to my plans, 
 a proposal which was put forth nearly 40 years ago by the late 
 Rev. E. L. Berthon, Vicar of Romsey, the inventor of the now 
 celebrated " Berthon " boat. A description of Mr. Berthon's 
 ,form of observatory, from his own pen, appeared in The 
 
280 TELESCOPES. 
 
 English Mechanic of October 13, 1871 ; and, as a consequence 
 of the publicity acquired in that way and otherwise, I have 
 reason to believe that a number of structures on the Romsey 
 model have been erected in various parts of the United 
 Kingdom. 
 
 One such was put up about 20 years ago by the late Mr. 
 T. R. Clapham, of Austwick Hall, near Lancaster, a descrip- 
 tion of which, from his own pen, appears in the second volume 
 of my Handbook of Astronomy. Mr. Clapham was a clever 
 and ingenious amateur mechanic, and his observatory, which I 
 have visited, represented Mr. Berthon's ideas, with sundry 
 minor improvements and developements of an advantageous 
 character ; but I will not go over again the ground which 
 Mr. Clapham kindly occupied for me in the pages of the book 
 which I have just mentioned. 
 
 My object in going into the foregoing details hns been to 
 encourage my readers who possess telescopes which, though in 
 a certain sense portable, are not readily portable, to make them 
 fixtures, and house them in observatories properly fitted up. 
 There can be no question whatever that a smaller telescope, 
 equatorially mounted on a fixed stand, and protected from the 
 weather, is capable, in careful hands, of yielding more useful and 
 profitable results, and in a more pleasant and convenient manner, 
 than a larger telescope mounted only on an altazimuth stand 
 which has to be carried in and out of a dwelling-house on every 
 occasion that it is used. It is not always easy to instil such 
 ideas as these into the minds of junior astronomers starting on 
 an astronomical career. To all such I would simply say that 
 I am giving expression to the experience of half a century 
 derived from the ownership in succession of telescopes with 
 apertures of i| inches (unmounted), 3 inches (mounted on an 
 equatorial block without circles), 4 inches (mounted equatorially 
 in an observatory) and 6 inches (ditto). Perhaps the most 
 common mistake made by juniors of the type which I have now 
 in mind is that of spending all their available money in increas- 
 
-Pics. 341-342 
 
 PLATE CXXVIII. 
 
 Sir W. Peek's Observatory, Rousden, Devonshire. 
 
 - K 
 
 Mr. J. Tebbutt's Observatory, Windsor, N.S.W. 
 
FIG. 343 
 
 PLATE CXXTX. 
 
THE TREPTOW OBSERVATORY. 28 1 
 
 ing the aperture of their instrument, and in regarding its stand 
 and its house as minor matters. This is a very grave mistake, 
 especially in regard to its stand. The use or non-use of an 
 equatorial mounting, however rough, with circles however coarse 
 in their graduations, contrasted with an altazimuth mounting, 
 however smooth and delicately made, is great : it means the 
 difference between an hour's work in studying a dozen objects 
 with ease, or 2 hours' work in hunting for and studying half a 
 dozen objects with trouble and difficulty. 
 
 I have met with cases of persons owning equatorials with 
 detachable telescope-tubes whose modus operandi is to keep 
 the tubes in boxes in their houses, and have equatorial stands 
 in the open air in their gardens covering up the circles, etc., 
 with boxes or waterproof covers when not in use, carrying the 
 tubes out of the house and back again as was required ; but, 
 however unavoidable in view of particular circumstances this 
 procedure may be, it is not one which will be found conducive 
 to good work or much work. 
 
 Fig. 344 is a view of a telescope of entirely novel con- 
 struction so far as its mounting is concerned, which has been 
 erected near Berlin by an enterprising German astronomer, 
 Dr. Archenhold, in spite of much hostile criticism on the part 
 of German men of science. The problem to be solved was how 
 to work a telescope of great size and power without the expense 
 and inconvenience of a very bulky and unhandy stand covered 
 by an enormous dome expensive to construct and laborious to 
 manipulate. The difficulty of working giant telescopes with 
 tubes 50 feet or more long is very great, especially when it is a 
 question of observing at one time objects low down towards the 
 horizon, and at another time objects overhead in the zenith. 
 This difficulty nowadays is met in large observatories, con- 
 structed regardless of expense, by surrounding the main pier of 
 an equatorial with a travelling floor, which can be raised or 
 lowered at the pleasure of the observer. Such a system is 
 illustrated elsewhere (see Figs, 338-340, ante}. By means 
 
282 TELESCOPES. 
 
 of such a floor the observer can put his seat in any position 
 which suits him, but the time and labour involved in bringing 
 about the necessary changes are very obvious. Dr. Archenhold 
 has been able to arrange to keep the eye-piece near the centre 
 of motion by swinging the telescope tube in a great fork, which, 
 provided with suitable counterpoises, permits of the tube being 
 run up into the air as may be required, whilst the heavy mov- 
 able parts are placed on a solid concrete foundation, which 
 secures due stability coupled with great compactness. In this 
 way the working parts of the mounting are housed under a 
 structure not expensive or difficult to build, because of no con- 
 siderable size, whilst the telescope tube, when not in use, is 
 brought down into a horizontal position and protected from the 
 weather by a cheap portable roof, which is made to run on it or 
 off it as required. The result of fitting up the instrument in 
 this fashion has been to do away with the necessity of having a 
 large and costly dome ; and the whole instrument, with its pro- 
 tecting roof, has cost no more than about ,13000, of which 
 ,2300 went in the object-glass, which is said to be an excellent 
 one, by Steinheil, of Munich, and is 27 inches in diameter. It 
 will be interesting to watch the future history of this novel 
 construction, which was only finished and brought into use in 
 April 1909. 
 
FIGS. 344-345 
 
 PLATE CXXX. 
 
 Telescope at the Treptow Observatory, Berlin. 
 
 282] 
 
 4-ft. Reflector of the Melbourne Observatory, 
 
FIGS. 346-347 
 
 PLATE CXXXI. 
 
 28-inch. Refractor of the Greenwich Observatory. 
 
 In use for visual work. 
 
 Meridian Circle, U.S. Naval Observatory, Washington. 
 
 [283 
 
CHAPTER XV. 
 TIME AND ITS MEASUREMENT. 
 
 Years. Months. Weeks. Days. Hours. The Sidereal year. The 
 Mean Solar Year. The Anomalistic Year. Hipparchus. The 
 Calendar and the reforms it has undergone. By Julius Ccesar. 
 By Pope Gregory XIII. His Calendar adopted by England. 
 But not by Russia. " Old Style." " New Style." The Lunar 
 Month. The Week. Quotation from Laplace. Savages count 
 time by " Moons." Divisions of the Day. The 24-hour Day. 
 a.m. and p.m. Railway time. The " Prime Meridian." 
 Greenwich chosen for this. Standard time. Usage of different 
 Nations. Where does the dzy begin ? The Transit Instrument and 
 how to use it for obtaining the time. 
 
 " TEMPUS FUGIT " is a truism which affects us all, from babyhood 
 to dotage ; but it is a matter which, on its historical side, has 
 many fascinating features. 
 
 A chapter on " Time and its Measurement " might readily 
 reach a great length, but I will put forward now rather the 
 utilitarian side. The subject will be most conveniently ap- 
 proached by posing certain questions to be used as pegs on 
 which to hang such information as it is intended to give. Let 
 us start, then, with the following questions : 
 
 1. What is a year? 
 
 2. What is a month ? 
 
 3. What is a week ? 
 
 4. What is a day ? 
 
 5. What is an hour ? 
 
 6. Where does time begin and end ? 
 
 7. How is it measured ? 
 
 8. Who starts and runs the almanac ? 
 
284 TIME AND ITS MEASUREMENT. 
 
 All these questions may be said, at the first glance, to have a 
 very commonplace appearance, and the solid science which lies 
 behind them all is far from being obvious ; nor do the questions, 
 when properly handled, admit of such simple and easy answers 
 as might at first sight appear. 
 
 What is a year ? The answer is the time occupied by the 
 Earth in performing one complete journey round the Sun, This 
 answer seems sufficiently simple, but it is not so in reality, 
 because we have to consider where the Earth starts from, and 
 where it arrives at the end of the interval which we call the 
 " year." This interval, simpliciter, is the interval which elapses 
 between two successive passages of the Sun through the same 
 equinox, and primd facie ought to be the time which elapses 
 from the moment when the Sun leaves a fixed star until it 
 returns to it again. This kind of year constitutes the "sidereal 
 year," and in our current notation consists of 365 d. 6 h. 9 m. 
 It unfortunately happens, however, that the equinoxes are not 
 fixed points, but are possessed of a small retrograde motion 
 from E. to W., which is constantly in progress, and the result 
 is that the Sun gets round again to the equinox from which 
 it started before it gets round to the Star from which it is 
 supposed to have started. The difference of time is a little 
 more than 20 minutes, so that the year (which we call the 
 " mean solar year ") is 20 minutes shorter than the year measured 
 by the stars, or sidereal year. The length of the mean solar 
 year is therefore 365 d. 5 h. 48m., neglecting fractions, and is 
 the year which we talk about in common conversation and in 
 almanacs prepared for terrestrial purposes. 
 
 Besides this, astronomers take note of the " anomalistic year," 
 which is different again, being 365 d. 6h. 13 m., and depends 
 upon the rather abstruse fact of the line of apsides of the 
 Earth's orbit beinj* subject to a progressive motion in virtue 
 of which the time between the Earth passing one perihelion 
 and another differs from both the mean solar year and the 
 sidereal year. 
 
WEEKS AND YEARS. 285 
 
 The month and the week depend more directly upon the 
 Moon than upon the Sun for their basis, as we do not speak of 
 a solar month or a solar week. Still, we have the calendar 
 month of 30 days, which is of very ancient origin, having been 
 handed down to us from a remote period when the Sun was 
 assumed to pass through the 12 signs of the Zodiac at an even 
 pace, with 30 days allotted to each span ; but, as this supposition 
 is at variance with the fact, it was soon found that, to treat the 
 year as consisting of 12 months of 30 days each, or 360 days in 
 all, led to such an estimate of the year landing people in 
 difficulties. Hence arose the necessity of putting on an odd 
 period of several days to secure some sort of uniformity between 
 the movement of the Sun (or to speak more correctly, the 
 movement of the Earth round the Sun), and the year as 
 adopted for the purposes of civil reckoning. When an adjust- 
 ment of some kind was first found to be indispensable it began 
 with the addition of 5 days to the year, one of which was allotted 
 to certain of the 12 months. Then it was discovered, and this 
 more than 2000 years ago, that 5 days was not enough, and 
 that it ought to be 5^ days. Next it was found that the period 
 of 5^ days was several minutes too much, and that 5 h. 55m. 
 was nearer the mark. This discovery was due to the great Greek 
 astronomer, Hipparchus, who flourished in the 2nd century B.C. 
 
 It is in the highest degree creditable to him that he arrived 
 at a value so very near the truth, for the best modern results 
 show that he was only wrong by about 6 minutes. This state- 
 ment does not exhaust the details of this very tangled question. 
 Julius Csesar was the man who may be said to have started our 
 calendar nearly in its modern form. He could not, of course, 
 take count of fractions of a day, and was obliged to assume that 
 the discrepancy already mentioned was an exact quarter of a 
 day, and would be cured by dropping in a whole day every 
 fourth year. l The idea was plausible, and it answered its pur- 
 
 1 The bissextile day=the second sextileday, or the 6th day before the Kalends 
 of March (the Roman Notation) reckoned twice. 
 
286 TIME AND ITS MEASUREMENT. 
 
 pose for a long while, but by the middle of the i6th century things 
 had gone astray again, so that the year began 10 days out of 
 place from the day settled by the Council of Nicasa as the ist 
 day of the year, namely March 21. This was the origin of what 
 we call the Gregorian reform of the calendar, which took its 
 name from Pope Gregory XIII., who brought it about in 1582. 
 He succeeded in imposing his suggestion on the States of 
 Europe of the Roman Obedience, but the Protestant States and 
 the Greek Church did not follow suit. In England the new 
 style was not adopted till 1752, when by Act of Parliament 
 1 1 days were ordered to be dropped out of the English chrono- 
 logy at that epoch. This enactment caused a good deal of 
 annoyance and inconvenience at the time, and explains why in 
 so many places in English history we find double dates, marked 
 O.S. (old style) and N.S. (new style), and why the national 
 financial year, which used to end at Lady-day, now ends on 
 April 5. Even to this day the Greek Church sticks to the old 
 Julian calendar, and the discrepancy between the two styles 
 has grown to 13 days. 
 
 Various other expedients have been propounded, some of them 
 of great exactness, for rendering more scientifically exact the 
 Gregorian Calendar, with its arrangement of leap years and so 
 on, as we now use it ; but, as it is a matter of adding or subtract- 
 ing an extra day in the course of several thousand years, no 
 useful purpose would be served by dwelling on any of these 
 proposals in this place. 
 
 The Lunar Month of 28 days, or thereabouts, must be 
 mentioned, not that it has any great bearing upon our daily 
 affairs except as regards a calendar of the high and low tides of 
 the ocean a matter which comes home to dwellers on the sea- 
 coast. 
 
 We must now say something about the " week," which is a 
 unit of time of the widest application. Its origin is lost in 
 antiquity, and, though it is usual to regard it as the one-fourth 
 portion of the lunar month, it is impossible to doubt that, after 
 
TIME BY THE MOON. 287 
 
 all said and done, it is a memorial of the creation of the 
 world, and therefore in use for nearly 6000 years. Laplace's 
 observations on this subject deserve to be noted : " The week, 
 from the very highest antiquity, in which its origin is lost, has, 
 without interruption, run on through ages uniting itself with the 
 successive calendars of different nations. . . . It is, perhaps, the 
 most ancient and most incontestable monument of human 
 intelligence, and appears to indicate that all such intelligence 
 came from one common source " which, Laplace might have 
 added, was divine. 1 
 
 The part played by the Moon in the computation of time must 
 not be too lightly esteemed because, from the earliest ages and 
 down even to the present time amongst savage and semi- 
 civilised nations, the phases of the Moon, beginning with the 
 first appearance of the New Moon, furnish a chronological scale 
 accessible to everybody and easily utilised. Hence we find 
 that savages often indicate considerable periods of time, which 
 we should speak of as so many months or years, by saying that 
 such and such a thing happened so many " Moons " ago. This 
 meaning, in other words, that, since the event in question 
 happened, they have seen the Moon wax and wane so many 
 times. It is easy to see that, if a canoe was upset on the 
 day that the young Moon was first seen, and that a young 
 Moon was seen again last night, the interval is that of one 
 " Moon," an interval which might be indicated in days if, since 
 the accident, every sunrise or sunset had been noted by means 
 of a notch cut in a stick. Even this method of computing 
 intervals of time has been used on occasions ; for instance, by 
 shipwrecked crews. 
 
 This brings us to the next unit of time the " day." This, 
 of course, is in universal use all over the world by everybody 
 for every conceivable purpose, but here again the insoluble 
 problem comes before us, Who invented the idea of dividing 
 
 1 Bishop Christopher Wordsworth, in his Commentary on Genesis, has some 
 interesting remarks which deserve attention. 
 
288 TIME AND ITS MEASUREMENT. 
 
 the day into 24 hours, or the alternative reckoning of 12 hours 
 of day and 12 hours of night ? Here, again, are questions which 
 cannot be answered off-hand, and which in a certain sense are 
 unprofitable questions. Hipparchus seems to have divided the 
 day into two equal portions of 12 hours each, beginning one of 
 his portions at midnight and the other at noon; but it is not 
 clear whether this was his own original idea or whether it was 
 borrowed from somebody else. So many systems were for- 
 merly in vogue, alike as to principles and details of counting 
 the hours, that it would be monotonous to attempt to describe 
 them. Suffice it to say, generally, that whilst the total of 24 
 was in general use, there have been great varieties of prac- 
 tice as to the grouping and as to the starting-points of the 
 hours. While some started from sunrise, others started from 
 sunset. While some started from midday, others started 
 from midnight. Others, again, ignoring a 24-hour division of 
 the day, grouped the hours into triplets or quadruplets, 
 which last-named system still prevails on board ship under the 
 name of " watches." 
 
 Even the present generation of inhabitants of the Earth have 
 seen, or are seeing, some momentous changes, two in particular 
 which may be said to be not remotely connected with the intro- 
 duction of railways. So long as people travelled in horsed 
 vehicles, or on foot, there would never be much confusion 
 between a.m. (ante-meridian) and p.m. (post-meridian) because, 
 as a rule, in by-gone centuries people did not travel by night, or 
 begin anything extending into the small hours of the morning. 
 When, however, long main lines of railway, covering hundreds 
 or even thousands of miles, became available for travel, the 
 question of time-tables, and of resort to them by passengers, 
 became serious, and the a.m.'s and p.m.'s of our forefathers 
 became very ensnaring. The English railways, in that conser- 
 vative spirit of the nation which occasionally is not to be 
 admired, have met the difficulty by various shifts, none of 
 which can be pronounced satisfactory. Whilst one line uses 
 

 THE DIVISION OF DAYS INTO HOURS. 289 
 
 light-faced figures for times between 6 a.m. and 6 p.m., and 
 black figures for the hours of night between 6 p.m. and 6 a.m., 
 another line uses the same sort of figures for all hours and 
 contents itself with a.m. and p.m., and leaves it to the 
 passenger to find his way through the time-table as best he 
 can. A third line, keeping to the same sort of figures, indicates 
 times between noon and midnight by a thin line between the 
 hour and the minute figures. These expedients are all very 
 lame and unsatisfactory. Certain foreign nations have done 
 much better by boldly taking the 24 hours of the day as the 
 only proper scale, and timing their trains from o o'clock to 
 24 o'clock. Without doubt this is what, sooner or later, we 
 shall come to in England, following, for instance, the Italians, 
 and more recently the French (to some extent), who have not 
 only adopted the 24-hour day for railway purposes, but for every 
 purpose. 
 
 The second modern change in the computation of time 
 alluded to above has had reference to what is called the 
 "prime meridian," or zero for time on the Earth. Formerly 
 every nation computed its time from its own capital, or some 
 such equivalent fixed point of longitude. Thus, time in Great 
 Britain was reckoned from the Greenwich meridian ; in Ireland 
 from Dublin ; in France from Paris ; in Spain from Madrid ; 
 in Germany from Berlin, and so on. So that a traveller passing, 
 say, from Spain into Germany, would start with his watch 
 showing Madrid time. When he entered France he would 
 have to alter his watch from Madrid time to Paris time. 
 When he quitted the eastern frontier of France his watch, 
 regulated by Paris time, would be no good for German railway 
 time-tables; and soon. The inconveniences attaching to this 
 state of things have probably been experienced by many 
 readers of these pages, but they are diminishing, and in the 
 near future will practically cease to exist because the whole 
 world is learning the advantage of having only one prime 
 meridian for the whole world. By common consent, the 
 I 9 
 
2QO TIME AND ITS MEASUREMENT. 
 
 meridian of Greenwich has been selected as the prime meridian 
 of the world, with provision for local adjustments to meet the 
 fact that the Earth turns on its axis once in 24 hours, and that 
 it cannot, therefore, always be noon or midnight at every place 
 on the Earth's surface at the same absolute moment of time. 
 
 What those adjustments are we have now to consider in a 
 summary form, but, for details, reference must be made to such 
 publications as Whitaker's Almanac. 
 
 It has been agreed by various nations that they shall take 
 their time from Greenwich by differences of only whole hours, 
 so that our ideal traveller from Spain to Germany will never 
 have to alter the minutes and seconds of his watch, but only to 
 remember that when he gets into Germany, or Austria, the 
 official hour will be one hour in advance of Greenwich ; in 
 Turkey and Egypt 2 hours in advance, and so on. On the 
 other hand, when he goes to America he will find that the 
 official hour at New York is 5 hours behind Greenwich, and that 
 the time is spoken of as " Eastern Time," the word " eastern " 
 having reference to the position of New York with respect 
 to the States of America. Further W., as he crosses the 
 American continent, he will come upon three other " times " 
 namely, " Central," " Mountain," and " Pacific " times, which 
 are respectively 6, 7, and 8 hours behind Greenwich time, 
 whilst Eastern Canada starts the scale with " Atlantic " time, 
 4 hours slow of Greenwich. This system of nomenclature, 
 depending on Greenwich, is not limited to the Northern Hemis- 
 phere, because our South African and Australasian Colonies have 
 similarly adopted the Greenwich meridian. Some of these 
 have split the hours and taken the intermediate |-hour as the 
 local standard time. It will show the comprehensiveness of 
 this movement for standardising local times when I state that 
 in Victoria, New South Wales, and Queensland local times are 
 linked to 10 hours fast of Greenwich, whilst South Australia has 
 chosen 9^ hours, and New Zealand n^ hours fast of Greenwich 
 for their respective bases. 
 
TIME ALL OVER THE WORLD. 
 
 291 
 
 The annexed diagram, which is published ihere by the kind- 
 ness of the Society for the Propagation of the Gospel, though it 
 
 '2NIDWCMT II30P* 
 
 Fig. 348. Time all over the world (by permission of 
 the S.P.G.). 
 
 is not actually graduated according to the official nomenclature 
 dependent on hours in advance of or behind the Greenwich 
 meridian, will yet serve the useful purpose of informing 
 
292 TIME AND ITS MEASUREMENT. 
 
 readers what are the local times relatively to Greenwich of 
 the countries which are named. 
 
 The meridian of Greenwich runs through France and North- 
 West Africa, and at Accra, on the Gold Coast, there is a certain 
 house of which it is said that the Greenwich meridian cuts 
 through it exactly to within r^tfth of a second. The writer of 
 the article in the S.P.G. magazine from which this diagram 
 is borrowed playfully remarks that : 
 
 "There is one place in the world, in the middle of the 
 Pacific Ocean, where the time seems to go all wrong. The 
 Editor was once crossing from New Zealand to South America, 
 when, on Sunday evening, as he had finished holding services 
 for the passengers, the captain passed word round the ship that 
 the next day would also be Sunday, the same day of the month. 
 He did not, however, hold any more services, but the week of 
 which this day was the beginning had 8 days in it. As a storm 
 continued during the whole time, it seemed a very long week." 
 
 This allusion to what always happens when a ship passes the 
 iSoth meridian from Greenwich, deserves some elucidation, and 
 I am-able to present the converse of what has just been narrated. 
 
 Mr. C. O. Burge, a retired Civil Engineer, writes : 
 
 " Just before arriving in New Zealand we had to cross the 
 meridian 180 West and East, the antipodes of longitude, and, in 
 order to keep time with the world's almanac, had to lose a 
 day that is to say, to go directly from Saturday to Monday ; 
 but, as the captain's birthday would have been on the missing 
 Sunday, and it would have been lost if, to use an expression 
 appropriate to my nationality, the omission had been celebrated 
 on the Sunday, it was decided to leave out Saturday instead. 
 All of us, therefore, who did not return in the reverse direction 
 lost a day never to be recovered, unless in the little pieces of 
 the extended days of our return to the old country, possibly 
 years later, while those who remained in the Antipodes never 
 got it back at all. For us, there were only 364 days in that 
 year, a sort of true Leap Year, for we jumped over a day a 
 missing 
 
 "' Syllable of recorded time.' 
 
WHEN THE DAY BEGINS. 293 
 
 " In the case of voyages in the opposite direction that is to 
 say, eastwards across this meridian an extra day must be 
 interpolated to keep time with the world. It is said that an 
 Irishman, which he wasn't at all, as he would say, being born 
 on the ocean, was launched into this sea of troubles on the 
 day following the 29th February of a Leap Year when the ship 
 in which his mother was a passenger was crossing the 180 
 meridian eastwards. His natal day was therefore the inter- 
 polated 30th of February, which for him never occurred again. 
 So, though he lived to a great age, he never had a subsequent 
 birthday." ' 
 
 This chapter may include the asking of, and the trying to 
 answer, a very tricky question, " Where does any given day, 
 say, New Year's Day, begin ? " The most definite answer 
 which can be given seems to be this that, in the case of all 
 nations which use maps which have the longitude of Greenwich 
 as their zero longitude, their day must be regarded as com- 
 mencing at the longitude of 180 E., and that accordingly as 
 one starts from that longitude and works westwards, so the day 
 begins, place by place, on the surface of the Earth as the E. 
 longitude diminishes from 180 down to no longitude at all, 
 which is therefore Greenwich itself. 
 
 As the i Both degree of E. longitude passes through a point 
 in the Northern Hemisphere in Eastern Siberia, and in the 
 Southern Hemisphere slightly to the E. of New Zealand, 
 therefore in a certain paradoxical, or imaginary, sense the day 
 for people in the Northern Hemisphere, whose longitude 
 standard is Greenwich, may be said to depend on Eastern 
 Siberia 2 as the place where their day begins, whilst people in 
 the Southern Hemisphere under corresponding circumstances 
 may be said to have their day start from near the eastern 
 coast of New Zealand. 
 
 1 C. O. Burge, Adventures of a Civil Engineer, p. 244. London, 1909. 
 
 2 This is only true in theory, because practically the line of demarcation is 
 treated as passing through Behring's Straits, and all Siberia as having East 
 longitude for lime purposes. 
 
294 TIME AND ITS MEASUREMENT. 
 
 The foregoing pages may suffice for furnishing some ele- 
 mentary ideas on the general principles which underlie the 
 measurement of time from the standpoint of one who regards 
 the matter in its immediate bearings on the daily affairs of 
 life ; but a good deal more would have to be said before the 
 subject of " Time " could be deemed at all exhausted. It 
 would be necessary to tell the reader how the astronomical 
 facts which control our measurement of time are brought down 
 from the heavens on to the surface of the Earth, and how 
 everything is tabulated to form the basis, first of our calendar, 
 and then of our almanacs but all these things would take us 
 too far afield from the main purpose of the present volume. 
 
 In the chapter on the telescope * I have named all the 
 equipment necessary for the ordinary purposes of an amateur 
 observer ; but if he wishes to go beyond the mere telescope 
 and the clock, and the building to house both, there is one 
 accessory instrument which he will find very useful, namely, 
 the transit instrument for keeping his clock correct without 
 the necessity of bringing the time home by his watch every 
 few days, and then having in each case to convert the civil 
 mean time into sidereal time. 
 
 The principle of the transit instrument is very simple, and 
 the practical use of it is not at all difficult or troublesome ; so 
 much so that in remote country districts, away from towns and 
 railway-stations, one occasionally comes upon a non-scientific 
 country gentleman who, making no professions of astronomy, 
 has and uses a transit instrument of some sort for mere time- 
 keeping purposes. 
 
 The principle of the instrument is this : that every star crosses 
 the meridian of a given place at a definite time, as laid down 
 in the Natitical Almanac ; and, if instrumental means are 
 at command for determining the exact moment when a star 
 crosses the meridian, and a Nautical Almanac (or some 
 sufficient substitute) is also at command, the time is imme- 
 1 Chapter XIV., ante. 
 
THE TRANSIT INSTRUMENT. 
 
 295 
 
 diately obtainable, 
 upon the pre- 
 cision of the 
 instrument used 
 and the care 
 which is exer- 
 cised. Accord- 
 ingly a large 
 and carefully 
 adjusted transit 
 instrument will 
 give a more 
 accurate result 
 than one which 
 is small and 
 only roughly 
 adjusted. And 
 such an instru- 
 ment will give 
 a better result 
 than no instru- 
 ment at all, for 
 the time of 
 the meridian 
 passage of a 
 star can be 
 ascertained by 
 such a thing as 
 a wall running 
 truly N. and S., 
 the arrival of 
 the star coming 
 up from the 
 E. in the line 
 of the wall 
 
 The accuracy of the result will depend 
 
 Fig. 349. The Transit Instrument for 
 obtaining the time. 
 
296 TIME AND ITS MEASUREMENT. 
 
 being noted by a clock, or even a watch with a seconds 
 hand. 
 
 In all such cases the principle is simply this : the almanac 
 says that the star ought to arrive at the meridian at a certain 
 instant marked by the time expressed in hours, minutes, and 
 seconds. If the star arrives seemingly too soon the clock 
 or the watch is too slow. If the star should arrive after its 
 appointed time the clock or watch is too fast. In carrying 
 out observations such as those just described the observer will 
 have to convert sidereal time into mean solar time in order 
 to find when the star ought to appear ; and he will also have 
 to convert mean solar time into sidereal time when he wants 
 to know what hour of R.A. is on the meridian at a given 
 moment. 
 
 The ordinary small or " Portable Transit Instrument " ex- 
 ternally consists of 3 principal parts, which will be understood 
 without difficulty by looking at the illustration (Fig. 349). There 
 are (i) the. telescope ; (2) the stand on which it is mounted ; and 
 (3) the declination circl^. The telescope tube is made in 2 
 parts, which are connected by a centre-piece, a cube in shape. 
 Into the centre-piece, at right angles to the main tube, are 
 fitted 2 branch tubes usually conical, which together form the 
 horizontal axis of the telescope. The smaller ends of these 
 transverse tubes are accurately ground to form 2 perfectly 
 equal cylinders or pivots. These pivots rest on Y's, which are 
 angular bearings surmounting the side-standards which support 
 the instrument as a whole. One of the Y's is fixed in a 
 horizontal groove, so that by means of a screw a small azi- 
 muthal motion may be imparted to the tubes as a whole which 
 constitute the upper portion of the instrument. The vertical 
 screws which go through the base are available for raising 
 or lowering the entire instrument so as to make sure that the 
 bearings which rest in the Y's shall be truly horizontal. 
 
 At one end of the horizontal axis a graduated circle is fixed, 
 which is to be so adjusted that the telescope can be set to 
 
THE USE OF THE TRANSIT INSTRUMENT. 
 
 297 
 
 stars of any given declination. This circle is divided into 
 degrees and subdivisions of a degree to be read, when great 
 exactness is required, by means of a Verneer. At the opposite 
 end of the horizontal axis provision is made to receive light 
 coming from a lamp, and designed to illuminate the wires 
 which are fixed in the eye-piece of the telescope. This light 
 from the lamp, when it reaches the centre-piece, is reflected 
 up the telescope to the eye-piece by means of a diagonal 
 reflector fixed in the tube. A movable striding level runs 
 across from standard to standard 
 to be used to ensure the hori- 
 zontality of the horizontal axis. 
 The lamp may or may not be 
 furnished with a sliding dia- 
 phragm to admit much or little 
 light according as the star to be 
 observed is a bright one, or a 
 small one likely to be overcome 
 if too much light is admitted. 
 
 Assuming that the transit 
 instrument, so far as its special 
 features have already been ds- 
 scribed, is in good workmg 
 order, the climax of its success 
 depends upon the wires which 
 
 appear in the field of view when the instrument is open for use 
 (Fig. 350). Literally only one vertical wire is required, because, 
 supposing the instrument is in proper adjustment when the 
 telescope is moved up and down, that one vertical wire travels 
 in the meridian of the place of observation. It is, however, 
 found in practice that an observer watching a star crossing 
 one wire is more likely to make a trifling mistake in estimating 
 the right moment by the clock than if he notes clock-time at 
 5 wires and strikes an average. It is usual, therefore, to 
 provide $ vertical wires, the calculation of an average from 
 
 359. The Planet Venus 
 an( j a star as seen in a 
 Transit Instrument. 
 
298 TIME AND ITS MEASUREMENT. 
 
 which is easy. While it must be stated that 3 wires are better 
 than i, but not so good as 5, yet 7 are better than either 3 or 
 5, and are provided in the large Transit Circles used in the 
 great public observatories. 
 
 There is in every transit instrument one horizontal wire 
 which serves to subdivide the field of view horizontally, and to 
 indicate the place where the star may be expected to cross 
 the field if the declination circle has been properly adjusted 
 to the tabular declination of the star ; but the horizontal wire 
 has no direct connection with the results yielded as regards the 
 time. It need hardly be stated that the accuracy of the ulti- 
 mate result depends upon the instrument as a whole being 
 accurately adjusted to its work, and this means that when 
 moved up and down it should always be in the meridian ; that 
 the horizontal axis should be truly level ; that the wires and 
 the object should both be in focus at the same time ; that the 
 centre wire should be exactly in the optical axis of the tele- 
 scope ; and that the main tube should be truly at right angles 
 to the horizontal axis. All these requirements are obtained by 
 means of suitable adjustment screws, which need not be more 
 particularly described here. 1 
 
 Fig. 351 is intended to represent graphically a thing which 
 is not very generally understood the " Equation of Time " : 
 what it is, and why it should exist, or be required to be acted 
 upon. The explanation is really very simple. We talk roughly 
 of the day as an interval of time depending on the Sun crossing 
 the meridian every day, or really on the rotation of the Earth 
 on its axis and such is the case, broadly stated ; but the day 
 which depends on the Sun differs from and is longer than the 
 sidereal day by an amount (3m. 56 s.) which, though trifling, 
 will disturb the even course of events unless adjusted somehow, 
 and the equation of time, as it is called, supplies the means of 
 adjustment. The fons et origo of the whole inconvenience is 
 
 1 See for such details my Handbook of Astronomy, vol. ii., " Astronomical 
 Instruments," and other books of the like nature. 
 
THE EQUATION OF TIME. 299 
 
 the fact that the Earth's orbit not being a circle, but an ellipse, 
 the Earth's pace in moving round the Sun (or the apparent 
 daily motion of the Sun through the zodiac) is not uniform, but 
 is faster with the Sun in perigee in January than it is with the 
 Sun in apogee in July. Hence it follows that, to keep an even 
 day of 24 hours throughout the year (the " mean solar day "), 
 we must equalise in some way the irregular length of the 
 
 Fig. 351. Diagram to represent graphically the 
 Equation of Time. 
 
 apparent solar day, and the Equation of Time is the expedient 
 adopted. 
 
 I have never seen the actual circumstances involved in the 
 measurement of time and the differences of time resulting from 
 the Earth's rotation on its axis so graphically expressed as they 
 have been by Mr. E. W. Maunder in an obscure but very 
 excellent monthly penny magazine called The Cottager, pub- 
 lished by the Religious Tract Society. The whole article is 
 
30O TIME AND ITS MEASUREMENT. 
 
 worth reading, but the particular passage which I wish to 
 assimilate will make the idea sufficiently clear. The ideal 
 observer is supposed to have gone up in a balloon from a place 
 in East London, near the East India Dock Gates, and to have 
 risen say 500 ft. somewhat higher than the cross of St. Paul's. 
 The writer then proceeds as follows : 
 
 "Taking a watch in our hand, we will note what happens. 
 As we look out, we see all London below us. To the E. it does 
 not stretch very far, but we can trace it on both sides of the 
 winding Thames out to Barking and Woolwich. N. and S. it 
 stretches farther ; W. we cannot see distinctly where it ends. 
 
 " It is not the great city itself, however, to which I wish to 
 draw your attention, but to the fact that it is all on the move. 
 It is slipping away from under us, ten times faster than any 
 express train in which we ever rode. We started from the 
 Dock Gates our watch has only beat 6 seconds and the great 
 tower of Limehouse Church has rushed by. We see St. Paul's 
 hurrying to us ; in 12 seconds more the Tower passes us on 
 the left, and 6 seconds later the great Cathedral has reached us. 
 
 " Four seconds more bring the Law Courts beneath our feet ; 
 another 12 seconds and it is the Marble Arch. It takes only 7 
 seconds for Hyde Park and Kensington Gardens to glide by ; 
 and Shepherd's Bush, Acton, and Ealing are sweeping forward 
 towards us. In I minute from the time that we rose up at the 
 Dock Gates the mighty city has gone by. Another minute 
 takes us out of Middlesex, and in 10 minutes from our start we 
 pass Bristol. If we had tried to reach it by the Great Western 
 Railway we should have required 2^ hours for the journey." 
 
CHAPTER XVI. 
 THE SPECTROSCOPE ASTRONOMICALLY. 
 
 What is a spectrum ? The decomposition of sunlight. Brief history 
 of the application of prisms to sunhght. Labours of Grimaldi. 
 Of Sir I. Newton. Of Wollaston. Of Fraunhofer. The lines in 
 the spectrum named by him. And after him. Some details as to 
 these. Their interpretation. The labours of Huggins and others. 
 Application of the spectroscope to celestial objects. Secchi's star 
 types. Motions of the stars as ascertained by the spectroscope. 
 
 A SPECTROSCOPE is, of course, from its very name, 1 an instru- 
 ment for examining a spectrum, and therefore we must begin 
 at the beginning, and learn what a spectrum is, and how an 
 instrument for examining it is constructed. But before getting 
 as far as this it will be desirable to give a little historical 
 retrospect. 
 
 The celebrated Italian astronomer and ecclesiastic, Antonio 
 Secchi, S J., once remarked that it might almost be said that, 
 in offering to us the brilliant colours of the rainbow, the 
 Creator has in effect invited us to examine the composition of 
 light and to study its nature. This mystery, however, was not 
 revealed to us until a comparatively recent period. The 
 " triangular glass " (as the prism was once called) has long 
 been known : its power to colour the rudest objects, and to 
 transform them into a cluster of precious stones, was a source 
 of amusement for the world in general, though a matter deemed 
 little worthy of the notice of the philosopher. 
 
 1 Spectrum, and a-Koireui, I view. 
 301 
 
302 THE SPECTROSCOPE ASTRONOMICALLY. 
 
 A certain Grimaldi was one of the first to study the prism 
 scientifically, and he did so with much care and success. He 
 made a hole in the shutter of a darkened room, through which 
 he let in a ray of sunlight, which he submitted to the action of 
 his prism. He was thus enabled to break up his ray of light, 
 which came from the Sun, and so obtain the solar spectrum, 
 which in due course he carefully described. After this experi- 
 ment, he proceeded to transmit rays of sunlight through glass 
 spheres filled with water. This enabled him to propound an 
 explanation of the rainbow, which was subsequently worked 
 out by Newton. Grimaldi's modus operandi, reproduced pic- 
 torially, was the basis of all those engravings, showing how a 
 ray of simple white light is split up into colours, which are 
 found in every book ever written on the subject. 
 
 It seems hardly necessary to dwell on the details of this, 
 though perhaps I had better do so. The ray of light entering 
 a room through the hole in the shutter meets the prism, 
 and, passing through it, comes out on the opposite side, 
 not as a single ray, as it entered, but split or decomposed 
 (to use the technical term). When it reaches the screen 
 it has become a wide strip of coloured light, red at one 
 end and violet at the other, with many intermediate shades 
 of colour in between. Newton repeated the experiment 
 in consequence of information derived from Grimaldi, and 
 so far improved upon it as to point out that passing the 
 spectrum through a second prism did not cause any further 
 change. He communicated his supplementary discovery to 
 his friend Arland, of Geneva, in a rough pen-and-ink sketch, 
 to which he prefixed the important legend, " Nee variat 
 lux fracta colorem " (The decomposed light undergoes no 
 change). 
 
 This impossibility of decomposing any further a ray which 
 has already traversed one prism constitutes in reality the 
 discovery made by Newton ; but he got a step beyond this, for 
 he recomposed white light out of colours by determining the 
 
SPECTRUM ANALYSIS HISTORICALLY. 303 
 
 proportions in which it was necessary to do this in order to 
 reproduce a light analogous to that of the Sun. He also 
 assigned names to the different colours. 
 
 A long interval of time elapsed after Newton before any 
 substantial progress was made in this department of Optics. 
 Wollaston was the next man. In looking at a narrow slit of 
 sunlight through a prism, he saw that the spectrum, instead of 
 being continuous, showed gaps in the form of black streaks, 
 which divided the spectrum into many compartments. This 
 discovery attracted no attention, and remained without fruit 
 until Fraiinhofer, wishing to determine more exactly the index 
 of refraction of certain sorts of glass which he was using, 
 perceived, and, so to speak, rediscovered what Wollaston had 
 previously discovered. He contrived methods of studying these 
 streaks, sketched them, and eventually defined their positions 
 relatively to one another by direct measurement. In conse- 
 quence of his industrious labours, the black streaks or lines 
 just alluded to are universally known nowadays as " Fraiin- 
 hofer's Lines," though priority for their discovery rests dis- 
 tinctly with Wollaston. 
 
 There is no great difficulty in seeing these lines. It is 
 necessary to look directly at the slit, and to focus the eye-piece 
 of a telescope of sorts on to the slit, so as to see the slit very 
 clearly defined. Then, after having placed the prism in the 
 path of the luminous rays, and in the position which answers 
 to that of minimum deviation, the telescope must be brought 
 to bear on the prism, and when the eye-piece is again duly 
 adjusted, by being brought to a focus, the lines will be visible. 
 If the prisrn is a good one, and the telescope is achromatic, a 
 great number of very fine lines will be seen. 
 
 Fraiinhofer applied to the principal lines observed by himself 
 certain letters of the alphabet ; capitals for some, and small 
 letters for others. These leading lines must be looked for as 
 follows : A in the extreme red ; B in the moderate red ; C in 
 the reddish- orange ; D in the yellow-orange ; E and b in the 
 
304 THE SPECTROSCOPE ASTRONOMICALLY. 
 
 green ; F at the commencement of the blue ; G in the indigo ; 
 H in the violet. These standard letters, as they may be called, 
 are in universal use, but subsidiary letters have been introduced 
 since Fraiinhofer's time, and also certain figures for facilitating 
 the comparison of the different parts of the solar spectrum with 
 the recognised table of wave-lengths. The caution may, per- 
 haps, well be given here that the lines do not correspond with 
 what might be regarded as the boundaries of the colours of the 
 spectrum, but are wholly independent of them. 
 
 These letters being understood generally, some details may 
 well now be given which will make their use as an index to the 
 solar spectrum better appreciated. A is a strong line close to 
 the red end of the spectrum. B is a strong and rather broad 
 line i in the red near its middle. Between A and B is a group 
 of several lines collectively called a. C is a dark and well- 
 marked line where the red is passing into orange. Between 
 B and C Fraiinhofer counted 9 fine lines ; between C and D 
 he counted about 30. D, in the orange, where it is passing into 
 yellow, consists of 2 strong lines close together. Between D 
 and E Fraiinhofer counted 84 lines. E, in the yellowish-green, 
 is a compound band of several lines, the middle one of which 
 is stronger than the rest. At b there are 3 strong lines, the 
 2 farthest from E being close together. Between E and b 
 Fraiinhofer counted 24 lines, and between b and F more than 
 50. The lines F, G, and H, which are at the commencement 
 of the blue, in the indigo, and in the violet respectively, 
 are well defined. Between F and G Fraiinhofer counted 
 185 lines, between G and H 190 lines, and many lines beyond 
 Hand between H and I at the extreme violet end of the 
 spectrum. 
 
 It will readily be realised that these dark lines are gaps or 
 breaks in the spectrum, but it will not be so easily realised why 
 there should be these gaps, indicative, as they are, primarily, of 
 the absence of rays of certain refrangibilities from the beam of 
 sunlight which we are supposed to be describing. It is obvious 
 
SPECTRUM ANALYSIS GENERALLY. 30^ 
 
 that something lies behind the absence of so many intermediate 
 rays of light, narrow though they be, and slight as may be the 
 joint effect they may have on the spectrum of the Sun on a 
 cursory inspection of it. 
 
 The story of the history of the successive stages in which 
 knowledge gradually accumulated in the interpretation of these 
 mysteries is far too long to be told here, but the substance 
 of it is this : that various metals and earths in a state of 
 incandescence or combustion, when examined through the 
 prisms of a spectroscope, yield certain bright lines, and 
 that in many cases the distribution of these bright lines is 
 coincident with the presence of dark lines in the spectrum of 
 sunlight. 
 
 When some of these spectra are carefully compared with the 
 lines in the spectrum of the Sun, and the coincidence of bright 
 lines of known origin with dark lines of unknown origin is 
 established, the inference is drawn (through stages of proof 
 which I do not detail) that the absence of light where the dark 
 lines appear is due to the presence in the Sun of a substance 
 identical in nature with a substance which is on the Earth, and 
 is, when examined, found to yield the particular bright lines 
 just spoken of, and no other bright lines. 
 
 The example usually cited to illustrate this is that of sodium. 
 Formerly no interpretation could be given of the D lines in the 
 solar spectrum. At a later stage in the progress of experiments 
 it was found that, when sodium (or its equivalent, common 
 salt) was burnt in the flame of a spirit-lamp, there was pre- 
 sented in the spectroscope no other prominent lines, bright or 
 dark, than the double D line. Hence physicists came to the 
 conclusion that sodium in the form of vapour was one of the 
 substances which is burning perpetually in the Sun. I must 
 cut a long story short by saying that many researches and 
 experiments by various eminent men at various dates and at 
 various places have led to the inference that a large number 
 of jnetals and mineral substances known on the Earth exist 
 
 20 
 
306 THE SPECTROSCOPE ASTRONOMICALLY. 
 
 on the Sun, and, by suitable treatment by means of spectro- 
 scopes, can be individualised. On the other hand, there are 
 lines in the solar spectrum which cannot be interpreted except 
 on the assumption that there are the Sun substances absent from 
 the Earth, and physicists have felt themselves justified in 
 individualising some of these, and giving them newly invented 
 names, such as helium and coronium. 
 
 In the first instance, and during all the early years of the use 
 of the spectroscope astronomically, its application was chiefly 
 to the Sun, and, though Fraiinhofer carried out some experi- 
 ments on certain conspicuous stars, it cannot be said that the 
 method of spectrum analysis was applied on any considerable 
 scale in other astronomical fields than the Sun until Muggins, 
 in 1864, began his famous researches into the constitution of 
 planets, comets, clusters, and nebulae. 
 
 Thus far general principles. The next matter which should 
 receive attention is the construction in practice of spectro- 
 scopes for actual use in the study of, not simply the Sun, 
 but any and all celestial objects. This, however, is a large 
 subject, altogether beyond the scope of this elementary 
 volume. 
 
 And, indeed, the subject of astronomical spectroscopy itself 
 is far too vast to be brought in at the tail-end of a popular book 
 on general astronomy, and is, moreover, a study not likely to 
 be taken up by the readers for whom this volume is more 
 especially designed. I shall therefore conclude by alluding 
 to two topics which may perhaps induce a few of my readers 
 to wish to go a step further by the aid of books specially 
 dedicated to spectroscopic astronomy. 
 
 The first matter to be mentioned is Secchi's classification 
 of stars. Whilst Huggins, working in conjunction with his 
 friend, Dr. W. A. Miller, of King's College, examined some- 
 thing like loo stars spectroscopically, Secchi investigated the 
 spectra of about 500 stars, and was led to distribute them 
 into 4 classes or types, an account of which he published 
 
307 
 
308 THE SPECTROSCOPE ASTRONOMICALLY. 
 
 in 1868. Secchi's types may be briefly summarised as 
 follows : 
 
 1. White stars, of which Sirius and Vega are types, yielding 
 spectra crossed by 4 broad dark lines, due to hydrogen, much 
 broader than those in the solar spectrum. Sodium and mag- 
 nesium may be easily identified in such stars. 
 
 2. Yellow stars, such as Aldebaran, Capella, Pollux, Arcturus, 
 and a Cygni, wherein the hydrogen lines are much less con- 
 spicuous than in Type I., but metallic lines, magnesium 
 especially, are numerous. 
 
 3. Stars with exceedingly beautiful spectra, crossed by 10 or 
 more dark bands, each band very dark and sharp on the violet 
 side, and gradually growing fainter towards the red end. 
 Betelgeuse (a Orionis), a Herculis, and Antares (a Scorpii), are 
 the principal stars of this type. 
 
 4. Red stars, which show 3 broad dark bands, shaded in the 
 reverse direction to those of the 3rd type. 
 
 These 4 types of stellar spectra are generally recognised by 
 astronomers, though, after Secchi, far more numerous observa- 
 tions, carried out by Vogel, Duner, Lockyer, and others, led to 
 other classifications. However, Secchi's 4 types have not been 
 generally superseded, though it ought to be added that he 
 himself was inclined to constitute a 5th class of stars showing 
 bright lines in their spectra. 
 
 The following points may be stated summarily. 
 
 The following stars have banded spectra : a Orionis ; o Ceti ; 
 a Herculis ; p Ursa majoris ; /3 Andromeda ; a Tauri ; /3 Pegasi ; 
 a Scorpii ; y Crucis. Stars of the helium type are mainly dis- 
 tributed in the galactic zones ; Orion stars are mainly of the 
 helium type ; Sirian stars of the hydrogen type ; Procyon stars 
 of the calcium type. 
 
 The last matter in connection with stellar spectroscopy, 
 which must just be named, is Huggins's interesting and in- 
 genious application of the spectroscope to isolated stars, with 
 the view of determining their velocities of approach and 
 
SPECTRUM ANALYSIS APPLIED PRACTICALLY. 309 
 
 recession in the line of sight to and from the Sun. Though 
 the whole idea of such an attempt to prove stellar movement 
 by means of the spectroscope seems a high flight of imagina- 
 tion, yet it does not appear that there are sufficient grounds for 
 distrusting the results arrived at in the case of several dozen 
 stars, though these results require us to talk about miles per 
 second as the pace at which the stars in question are travelling 
 to and from somewhere. 
 
CHAPTER XVII. 
 
 TABLE OF THE CONSTELLATIONS, WITH 
 A BRIEF DESCRIPTIVE ACCOUNT OF 
 EACH. 
 
 BY the entries in the column headed " Centre " it is meant to 
 be inferred that a line of Right Ascension and a line of Declina- 
 tion taken off the map will intercept at a point which may be 
 regarded as about the centre of the constellation. This, how- 
 ever, is only true of the more compact constellations, for there 
 are some, like Draco, Cetus, and Argo, which are so long and 
 straggling that they extend over several hours of R.A. When, 
 therefore, I state that the constellations are here arranged in 
 the order of R.A. , the statement must be regarded as needing 
 some qualification in many cases. In the column of " Declina- 
 tion " + means North, and South. 
 
 Name of Constellation. 
 
 Centre. 
 
 R.A. 
 
 Dec I. 
 
 Pisces 
 
 Sculptor (Apparatus sculptoris) . . . 
 Andromeda ....... 
 Phcenix . . . . . , 
 
 h. m. 
 O 2O 
 
 o 30 
 
 o 40 
 
 I 
 I 
 
 * 45 
 
 2 O 
 2 25 
 2 30 
 2 40 
 
 3 20 
 
 + 10 
 
 + 38 
 - 48 
 
 + 60 
 
 12 
 + 32 
 
 - 33 
 
 + 20 
 - 72 
 + 42 
 
 Cassiopeia 
 
 Cetus 
 
 Triangulum ....... 
 
 Fornax (Chenrica) ...... 
 Aries 
 Hydrus 
 
 Perseus 
 
 310 
 
THK POSITION OF THE CONSTELLATIONS. 
 
 Name of Constellation. 
 
 Centre. 
 
 R.A. 
 
 Decl. 
 
 
 h. m. 
 
 3 20 
 3 So 
 3 So 
 4 3 
 4 40 
 5 o 
 5 20 
 5 25 
 5 30 
 5 40 
 5 40 
 5 40 
 6 o 
 6 40 
 7 o 
 7 o 
 7 30 
 7 40 
 7 So 
 8 o 
 830 
 8 40 
 8 40 
 9 o 
 9 30 
 10 o 
 
 10 10 
 
 10 20 
 10 30 
 10 40 
 
 II 
 II 
 II 20 
 12 20 
 12 30 
 12 30 
 12 40 
 13 
 13 20 
 
 
 
 - 52 
 - 6 3 
 - 30 
 + 18 
 - 42 
 - 60 
 
 + 3 
 20 
 
 - 52 
 - 77 
 - 34 
 + 70 
 + 42 
 _ 24 
 -f- 24 
 - 3 
 + 6 
 - 32 
 + 45 
 _ 40 
 
 + 20 
 _ 62 
 - 6 9 
 - 30 
 
 - 45 
 - 35 
 i 
 
 + 33 
 + 15 
 - 78 
 
 12 
 
 + 58 
 - 15 
 - 60 
 
 - 18 
 - 68 
 
 + 27 
 + 40 
 - 47 
 
 Reticulum (Rhomboidalis) .... 
 
 Taurus . . . . ; ' . " . . 
 Cselum (Ccela sculpt oris) . . . 
 
 Orion . .... * ' .... 
 Lepus . . . . * 
 Pictor (Equleus pictoris) . . 
 Mensa (Mons tnensa) . . . . . 
 
 Camelopardus . .... . . 
 Auriga 
 Canis Major *. 
 Gemini 
 Monoceros 
 
 Argo(/VAO 
 
 Argo 
 Cancer ........ 
 Argo (Carina) 
 
 Argo (Ma/us) 
 Argo ( Vela] 
 
 Sextans 
 Leo Minor 
 Leo 
 Chamseleon 
 Hydra 
 Ursa Major 
 Crater 
 Crux . . . . . . 
 Corvux x 
 Musca Australis 
 Coma Berenices 
 Canes Venatici 
 Centaurus 
 
312 
 
 CONSTELLATIONS. 
 
 
 Centre. 
 
 TU^ r/- 4 ii_.' 
 
 
 
 R.A. 
 
 Decl. 
 
 
 h. m. 
 
 o 
 
 Virgo 
 
 13 2O 
 
 2 
 
 Bootes 
 
 14 35 
 
 + 3O 
 
 Circinus 
 
 14 50 
 
 
 Lupus 
 
 15 o 
 
 - 4 
 
 Libra 
 
 15 10 
 
 .- 14 
 
 Apus ........ 
 
 15 3 
 
 - 76 
 
 Serpens ....... 
 
 15 35 
 
 + ' 8 
 
 Corona Borealis 
 
 15 4 
 
 + 30 
 
 Triangulum Australe ..... 
 
 15 40 
 
 - 65 
 
 Ursa Minor 
 
 15 40 
 
 -t- 7& 
 
 Norma ........ 
 
 16 o 
 
 - 49 
 
 Draco 
 
 16 o 
 
 + 60 
 
 Scorpio 
 
 16 20 
 
 _ 26 
 
 Ara 
 
 16 50 
 
 - 55 
 
 Ophiuchus 
 Hercules ....... 
 
 17 10 
 17 10 
 
 - 4 
 + 27 
 
 Corona Australis 
 
 18 30 
 
 
 Scutum Sobieskii 
 
 18 30 
 
 _ 10 
 
 Telescopium 
 
 18 40 
 
 - 52 
 
 " Lyra 
 
 18 45 
 
 + 36 
 
 Sagittarius 
 
 19 o 
 
 - 2 5 
 
 Pavo .... 
 
 19 10 
 
 2 ** 
 
 Aquila (with Antinoiis) .... 
 
 19 30 
 
 -. 2 
 
 Sagitta 
 Vulpecula et Anser ..... 
 
 19 50 
 
 20 10 
 
 + 18 
 + -5 
 
 Cygnus 
 Delphinus ....... 
 
 20 30 
 
 20 35 
 
 -r 40 
 + 12 
 
 Capricornus 
 
 20 50 
 
 _ 20 
 
 Microscopium 
 
 21 O 
 
 - 37 
 
 
 21 IO 
 
 + 6 
 
 Indus 
 
 21 2O 
 
 - 58 
 
 Piscis Australis . . . . 
 
 21 40 
 
 - 32 
 
 Cepheus 
 
 22 
 
 4- 70 
 
 Grus , 
 
 22 2O 
 
 - 47 
 
 Aquarius 
 
 22 20 
 
 - 13 
 
 
 22 25 
 
 T 43 
 
 Pegasus 
 
 22 30 
 
 T"O 
 
 + 17 
 
 Toucan . . . . " . . . . . 
 
 23 45 
 
 - 68 
 
 
 Polar 
 
 (South) 
 
 
CONSTELLATIONS: R.A., OH. OM. TO 2 H. 25 M. 313 
 
 A few lines will now be given to each of these constella- 
 tions by way of assisting an observer in finding them and in 
 recognising their constituent stars. 1 
 
 Pisces (The Fishes) is a dull and uninteresting constellation, 
 the precise whereabouts of which can only be discovered by 
 glancing upon it from neighbouring constellations. It immedi- 
 ately adjoins, to the S., the " Square of Pegasus," by means of 
 which, therefore, it can be readily found. The 2 brightest stars 
 are 77 and y, each about mag. 3! , 
 
 Sculptor is a southern constellation, barely visible in England. 
 Its brightest star, a, is only of mag. 4. 
 
 Andromeda ("The Chained Lady") is one of the largest and 
 most important constellations in the northern heavens, contain- 
 ing as it does 3 stars of the 2nd mag. (a, /3, y), whilst 8 is 3^, 
 and v and o are both 3f. 
 
 Phoenix, a southern constellation, has the following bright 
 stars : a 2^, /3 and y both 3^, and c 3f. 
 
 Cassiopeia ("The Lady in her Chair") is a constellation of great 
 extent and of much interest to the telescopist, owing to the fact 
 that a part of the Milky Way, very rich in stars, runs through it. 
 Its naked-eye stars include the well-known W. group. The 
 chief stars are : a 2, y and /3 2|, 8 2|, and 77, e, , all about 3^. 
 
 Cetus (The Whale) is a very large constellation as regards its 
 area, but of no great interest from a naked-eye or telescopic 
 point of view. Its most interesting object is the celebrated 
 variable star Mira. The chief stars are : /3 2, a 2|, t, 77, r, andy, 
 all 3 i, and 6, f, , all 3 |. 
 
 Trianguhim (The Triangle). This is one of the ancient 
 constellations, notwithstanding its small size. Its principal stars 
 are /3 3, and a 3^. 
 
 Fornax Chemica (The Chemical Furnace). In speaking of 
 
 1 The more exact valuations now in use take account of differences of 
 magnitude amongst the larger stars to tenths. These refinements are, 
 however, ignored in the paragraphs which follow, and the magnitudes are 
 given only to quarters of a magnitude. 
 
314 CONSTELLATIONS: R.A., 2 H. 30 M. TO 5 H. OM. 
 
 this constellation it is usual to drop the word " Chemica." It 
 has no brighter star than one of mag. 4^. 
 
 Aries (The Ram). In the Ram's head there are 3 moderately 
 conspicuous stars which serve to indicate the position of the 
 constellation. These are : a 2, j3 2|, and y 4. 
 
 Hydrus (The Small Snake). This is a southern constellation 
 not far from the S. Pole. Principal stars : /3 2|, and a and y, 
 both about 3. 
 
 Perseus. This is a very brilliant constellation, because it 
 embraces a very rich portion of the Milky Way. Its chief stars 
 are : a 2, /3 2j, f, y, , 6, all about 3, and p, 3! . /3 Persei, better 
 known by its Arabic name of "Algol," is a very remarkable 
 variable star of short period. 
 
 Horologium (The Clock), a southern constellation, has one 
 fairly conspicuous star, a 3|. 
 
 Reticulum (The Net) is also a southern constellation. Chief 
 stars : a 3^, and /3 4. 
 
 Eridanus is a very long, straggling constellation, reaching 
 from the Equator to 60 of S. Declination. Its important stars 
 are invisible in England. They are : a (Achernar) I ; #, 2^ ; 
 /3 andy, 3 ; v 4 and $, 3^ ; together with e, d, Flamsteed's 12, v 7 and 
 r 4 , all about 3! . 
 
 Taurus (The Bull). This is a large and interesting constella- 
 tion comprising naked-eye and telescopic objects in great 
 variety. Amongst the former are the celebrated groups of the 
 Pleiades and the Hyades and the beautiful ist-magnitude star 
 Aldebaran. The other bright stars are : 182, ?, , 3, X, J , 3^ ; 
 together with e, o, , and Flamsteed's 17 and 27, all of about 3f. 
 Besides these there are no fewer than 48 stars ranging from 
 mag. 4 to 5J. 
 
 Caluni (The Graving Tool) is a small southern constellation, 
 the two brightest stars of which, a and y, are only 4^. 
 
 Dorado (The Sword-fish), a southern constellation, has for its 
 chief stars : a 3, and /3 4. This constellation contains a cele- 
 brated cluster of stars. 
 
FIG. 353. 
 
 PLATE CXXXII. 
 
 Central Portion of Orion (F. W. Longbottom). 
 
 314] 
 
FIGS. 354-355 
 
 PLATE CXXXIII. 
 
 [315 
 
CONSTELLATIONS: R.A., 5 H. 2O M. TO 7 H. O M. 315 
 
 Orion, This, though not in area the largest, is by far the 
 most brilliant and interesting of all the constellations, both as 
 regards its naked-eye stars and its telescopic objects. Its 
 position, too, is very good for observers in England, as it comes 
 to the meridian in the winter at a very convenient altitude. Its 
 2 brightest stars, /3 (Rigel) and a (Betelgeuse), are both, especi- 
 ally the former, brighter than the average ist-magnitude stars ; 
 then, besides, there are 4 of the 2nd magnitude, *, -y, , K. Next 
 follow d 2^, i 3, vr 1 3j, 77, X, r, 3^, and a- 3!, with 45 stars of mags. 
 4 to Si 
 
 Lepus (The Hare) is a small constellation immediately S. of 
 Orion, with the following conspicuous stars : a 2|, /3 3, and /M 3^, 
 and C, 17, y, 3f 
 
 ' Pictor (The Painter) is a southern constellation with the 
 following as its chief stars : a 3^, /3 4. 
 
 J/0/Z.T Mensa (The Table Mountain), in the Southern Hemi- 
 sphere, is one of the least important of all the accepted constella- 
 tions, and has no star brighter than 5^. 
 
 Columba Noachi (Noah's Dove), generally called Columba, is 
 a small constellation to the S. of Lepus, and only partly visible 
 in England. Its chief stars are : a 2 j, /3 3, and e 3!. 
 
 Camdopardus (The Camelopard) is a long, straggling con- 
 stellation with a large number of 4th-magnitude stars, but 
 nothing brighter. 
 
 Auriga (The Charioteer) is a constellation occupying a large 
 area, and with one star in particular, a (Capella), which is very 
 brilliant, being indeed in the judgment of some the second 
 brightest star visible in England, ranking after Sirius. The 
 other bright stars are : |3, 2 ; 0, i, 2| ; e, 77, 3! ; and 5, 3! . 
 
 Cants Major (The Greater Dog). This, though quite a small 
 constellation as regards its area, contains a large number of 
 conspicuous stars, including the brightest of all, Sirius. The 
 other bright stars are : e i, S if, |8 2, 77 2^, , o 3 , 3, and 
 Flamsteed's 22 and 28, both about 3^. 
 
 Bernini (The Twins) has 2 stars with familiar names as 
 
316 CONSTELLATIONS: R.A., 7 H. o M. IOH. TO o M. 
 
 leaders, together with several others of lesser magnitude. The 
 chief stars are : /3 (Pollux) i, a (Castor) i, y 2, /u, and e 3^, , s, X, 
 5 and K all about 3^, and 6 3f. 
 
 Monoceros (The Unicorn) has 2 stars of mag. 4 and nothing 
 larger ; it is, however, not an unimportant constellation, being 
 rich in telescopic objects owing to its position in the Milky Way. 
 
 Cants Minor (The Lesser Dog), though a small constellation, 
 will always be readily found by its a (Procyon), one of the 
 largest of the ist-magnitude stars. The next star, /3, is only of 
 mag. 3. 
 
 Argo (The Ship Argo) is not an easy constellation to describe 
 because of its great extent, and, by way of facilitating work in 
 its confines, it has been by common consent cut up into 4 
 divisions, respectively called Carina (The Keel), Mains (The 
 Mast), Puppis (The Poop), and Vela (The Sails), to which some 
 add a 5th, Pyxis Nautica, a part of Malus. The conspicuous 
 stars are : a (Canopus), a very bright ist-mag. ; then follow 
 ft *, 8, 2 ; i, , X, 2 ; K, $, 2| ; <9, p, p, y, 3 ; r, v, 3 J ; , i>, <r, o>, 3^ ; 
 X^ V') 3l- These stars will be found scattered all over the 
 constellation. Canopus is the second brightest star in the 
 heavens, being but slightly inferior to Sirius, which it only 
 precedes in R.A. by about 18 m. 
 
 Lynx is a troublesome constellation to find, its brightest star, 
 a, being only 3^ ; and the next one. Flamsteed's 38, only 3! . 
 
 Cancer (The Crab). The most conspicuous star is j3, only 3^ ; 
 but the cluster " Praesepe " will indicate this constellation to the 
 naked-eye observer. 
 
 Volans. The proper name of this southern constellation is 
 Piscis Volans (The Flying Fish) ; but, as there are 2 other Fishes 
 in the heavens (Pisces, the Zodiacal constellation, and Piscis 
 Australis), it has been agreed to drop the 3rd Piscis and 
 use only the word " Volans." Its chief stars are : y and /3, 
 both about 3|. 
 
 Antlia Pneumatica (The Air-pump). The brightest star is a 
 only of mag. 4^. 
 
FIG. 356 
 
 PLATE CXXXIV. 
 
 The " Southern Cross.' 
 
 516] 
 
FIG. 357 
 
 PLATE CXXXV. 
 
 The Spiral Nebula, 51 M. Canum Venaticorum (Earl of Rosse). 
 
 [317 
 
CONSTELLATIONS: R.A., IO H. TO M. TO 12 H. 2O M. 317 
 
 Sextans (The Sextant) is an insignificant constellation, and its 
 brightest star only 45. 
 
 Leo Minor (The Lesser Lion) lies to the N. of Leo Major ; 
 its brightest star is Flamsteed's 46, of mag. 4. 
 
 Leo (The Lion). The prominent feature of this constellation is 
 the group of stars known as " The Sickle." The chief stars are : 
 a (Regulus), i ; v, 0, 2\ ; 8, 2f ; e, 3 ; 0, 77, f, all 3^ ; and o, 3^ . 
 
 Chamceleon. This is a small and unimportant constellation 
 not far from the S. Pole, and with no star brighter than a, 4^. 
 
 Hydra (The Water-snake). A long-straggling constellation 
 extending through more dian 6 hours of R.A. Chief stars : 
 a, 2 ; , v, y, TT, e, all about 3 J. 
 
 Ursa Major (The Great Bear). This has already been some- 
 what fully described on a previous page. Its chief stars are : 
 (Alioth), i| ; a (Dubhe) and 77 (Benetnasch), both 2 ; 
 (Mizar), /3 and y, all 2j ; /*, ^, t, 0, all 3 ; o, e, X, 3^ ; *, ^, |, i/, 3|. 
 
 Crater (The Cup) is a small constellation sometimes treated 
 as part of Hydra. Its 2 principal stars are : Flamsteed's 19, 
 and 8, both of them scarcely of mag. 4. 
 
 Crux (The Cross). This is a southern constellation, small in 
 size, but with 4 conspicuous stars which suggested its name. 
 Opinions seem much divided as to whether it really is a striking- 
 group. The chief stars are : a ij, /3 if, y 2, and 8 3^. The fol- 
 lowing is the opinion of Mr. W. B. Gibbs, F.R.A.S. : 
 
 "The Southern Cross" is formed by five stars, of which only 
 one is of the ist magnitude, the others are of the 2nd and lower 
 magnitudes. Closely following, a few degrees away, are the two 
 bright stars a and 3 Centauri, which are sometimes called " The 
 Pointers." When the cross is vertical its longer diagonal points 
 to the S., and at any other time the South Pole may be approxi- 
 mately found by prolonging this diagonal 4^ times its own length 
 in the direction of the South Pole. Altogether these two stars 
 of the Centaur and those of the Southern Cross make a most 
 notable group, the most characteristic star-group of the Southern 
 Hemisphere." 
 
318 CONSTELLATIONS: R.A., 12 H. 30 M. TO 15 H. TOM. 
 
 Corvus (The Crow). A small constellation with some very 
 bright stars, several of which are suspected to be variable. 
 The 4 chief stars, y and )3, both 2f, and e and 8 both 3, form a 
 trapezium. 
 
 Musca Australis (The Southern Fly) is a southern constella- 
 tion. Chief stars : n 3, /3 3^, 5 and B.A.C. 3984, both 3|. 
 
 Coma Berenices (Berenice's Tresses) is a small constellation 
 of medium-sized stars distributed at somewhat even intervals. 
 The brightest, /3, is only 4^, but there are 17 as bright or 
 brighter than 5^. 
 
 Canes Venatici (The Hunting Dogs). This constellation has 
 but one bright star, a, called also " Cor Caroli." Hevelius 
 desired to form this into a separate constellation to commemo- 
 rate Charles II. 
 
 Centaurus (The Centaur) is a large and important southern 
 constellation with many bright stars, none of which are visible 
 in England. These are : a 2 , /3, both of mag. I ; 6 if ; y, 77, e, 
 2i 5 C, 8, 2f ; i, 3 ; K, 3! ; X, /z, a 1 , 3^, and v, 3! . 
 
 Virgo (the Virgin) has one very bright star, a (Spica), but 
 is a constellation chiefly noted for its many nebulae. The 
 other chief stars are : f, e, 3 ; , 3^ ; /3, 6, Flamsteed's 109, 
 all 3l ; 
 
 Bootes (The Bear Leader). This is one of the largest of the 
 northern constellations, and possesses in a (Arcturus) one of 
 the most brilliant of the northern stars, its rivals being a Aurigas, 
 and a Lyrae. Its other chief stars are : e, i\ ; 77, y, 3 ; 8, /3, p, 
 
 3*;C,3l. 
 
 Circinus (The Compasses) is a very small southern con- 
 stellation, the brightest star of which is a, 3^. 
 
 Lupus (The Wolf) is a southern constellation, a mere frag- 
 ment of which is visible in England. The bright stars are : 
 , 3, 2| ; y, 3 ; 1 , 3^ ; 8, *, 77, t, all 3^. 
 
 Libra (The Balance) is so low down in the southern horizon 
 that it is not easy to get hold of it, especially as its visibility 
 coincides with the short nights of the English summer. Its 
 
CONSTELLATIONS: R.A., 15 H. 30 M. TO i6n. 50 M. 319 
 
 principal stars are : /3, 2f, and a and Flamsteed's 20, both 
 about 3. 
 
 Apus{ (sometimes called Avis Indica, The Bird of Paradise) 
 is a small constellation not far from the South Pole, and its 
 brightest star, a, is only about mag. 4. 
 
 Serpens (The Serpent) is a straggling constellation, much 
 mixed up with Ophiuchus. The chief stars are : a, 2f ; 77, p., 3^ ; 
 and e, |, , all about 3^. 
 
 Corona Borealis (The Northern Crown) bears more resem- 
 blance to its name than most of the constellations do. Chief 
 stars : a, 2^, and /3, 3! ; with 13 stars between 4 and 55-. 
 
 Triangulum Australe (The Southern Triangle) is a small 
 southern constellation, with several bright stars : a, 2|, and y, /5, 
 each 3. 
 
 Ursa Minor (The Little Bear) is often spoken of as being a 
 facsimile of the Great Bear, but the idea is rather far-fetched. 
 The real importance of this constellation is due to the Northern 
 Polar point and the Pole Star being within its boundaries. Its 
 chief stars are : /3 (Kochab), and a (Polaris), both about 2 ; and 
 
 y,3i 
 
 Norma (The Rule) is an unimportant southern constellation, 
 whose brightest star (y 2 ) is only of mag. 4^. 
 
 Draco (The Dragon) is a constellation which may almost be 
 said to extend everywhere, for it reaches through nearly 12 hours 
 of R.A., and is circumpolar in England. The difficulties of 
 studying it are aggravated by the fact that when on the meridian 
 it is absolutely in the zenith. Chief stars : y, 2^ ; 77, 2| ; /3, 3 ; 
 C, 3i 5 i, , 3? 5 X, *> 3l 5 with 43 stars ranging from 4 to 5^. 
 
 Scorpio (The Scorpion) is a zodiacal constellation, rather un- 
 favourably placed for observers in England. Its principal star, 
 a, of mag. i, is known as Antares ( = the "rival of Mars"), a 
 name given to mark its red colour. The other chief stars are : 
 X, if ; (9, f , 2 ; S, K, 2 ; v, 2 | ; /3 1 , r, o-, TT, all 3 ; t l , 3^ ; ^, 2 , 77, 
 all 3i 
 
 Ara (The Altar) is a small constellation, but with a good 
 
320 CONSTELLATIONS: R.A., 17 H. IOM. TO 19 H, 50 M. 
 
 share of medium-sized stars. These are : ft 2| ; a, 3 ; , 3^ ; y, 
 32 J ^ *?> 3l J #> S D0tn about 4. 
 
 Ophiuchus^ sometimes called Serpentarius (The Serpent- 
 bearer), is much mixed up with Serpens, the animal carried, 
 and with Hercules. The chief stars are : a, 2| ; ?/, 2^ ; S, , 2| ; 
 ft 3 ; e, K, 0, i/, all about 3^ ; y and Flamsteed's 72, both 3|. 
 
 Hercules is a large and important constellation, with a great 
 variety both of naked-eye and of telescopic objects. Its 
 principal stars ars : ft 2! ; , 3 ; a, 8, 3^ ; TT, /n, 3! ; 77, y, 3!; with 
 41 stars from 4 to 55. 
 
 Corona Australia (The Southern Crown) is a southern con- 
 stellation with no stars brighter than mag. 4. It is to be 
 noticed that 6 of its naked-eye stars are disposed in a curved 
 line. 
 
 Scutum Sobieskii is sometimes called Clypeus Sobieskii, but 
 the single word Scutum (The Shield) is its more usual designa- 
 tion. Its brightest star is B.A.C. 6325 of mag. 4. 
 
 Telescopium (The Telescope) is a small southern constellation, 
 the brightest star of which is a, 3^. 
 
 Lyra (The Lyre) is a constellation small in size, but it pos- 
 sesses in its a (Vega) a very brilliant ist-magnitude star, and 
 a great variety of important telescopic objects. After Vega 
 come y, 3^ ; and ft 3^. 
 
 Sagittarius (the Archer), by reason of its low altitude in 
 England, is not generally appreciated, but it contains a con- 
 siderable number of important stars. Thus : e, 2 ; er, 2^ ; 8, 2-f ; 
 C, /> >7, \ TT, all 3 ; 0, 3[ ; 3 , r, 3^ ; /3 1 , 3! ; with 36 stars from 
 4 to 51 
 
 /W0 (The Peacock) is a small southern constellation with 
 some conspicuous stars : a, 2 ; ft 3^ ; 8, 3^ ; 77, 3! . 
 
 Aquila (The Eagle), though only a small constellation, is rich 
 in bright and double stars. The chief stars are : a, i ; y, 2| ; 
 , 3 ; 6, 8, X, 3^ ; whilst ?;, is a bright 4. 
 
 Sagitta (The Arrow) is a small but ancient constellation, with 
 2 stars, y, 8, both of them about 3^. 
 
CONSTELLATIONS, R.A., 2O H. IOM. TO 22 H. 2O M. 32! 
 
 ?cula et Anser. As a fox and a goose were 2 things 
 which formerly were supposed to go together (for a short time), 
 so Vulpecula had an Anser associated with him ; but the Anser 
 has long since disappeared down the Fox's throat, and as- 
 tronomers only talk now of the Fox. The brightest star is a, 4^ ; 
 but there are no fewer than 14 stars ranging from 4| to 5^. 
 
 Cygnus (The Swan) is a large and important constellation, 
 with much in it to interest all classes of students. A rich part 
 of the Milky Way occupies a considerable area of it, and a 
 large number of prominent red stars are also among its special 
 features. The chief stars are : a (Deneb) i^ ; y, 2| ; c, 2f ; d, j3 
 (Albireo), 3 ; , 3^ ; , to', 3! ; together with no fewer than 53 
 stars between 4 and 5^. 
 
 Delphinus (The Dolphin) is an unimportant northern constella- 
 tion, the brightest star of which is ft 3! . 
 
 Capricornus (The Goat) is a constellation low down in Eng- 
 land, with not much to attract the naked eye. Its chief stars 
 
 are : 5, 3 ; ft 3i J 2 , f , 7> a11 3f 
 
 Microscopium (The Microscope) is a small southern constella- 
 tion whose brightest star, l , is only 4|. 
 
 Equuleus (The Little Horse) is a small constellation whose 
 brightest star, a, is only 4. 
 
 Indus (The Indian) is a small southern constellation whose 
 brightest stars are : a, 3, and ft 3! ; but e of mag. 5^ is distin- 
 guished for its remarkably large proper motion. 
 
 Piscis Australis (The Southern Fish) has only one bright star, 
 a (Fomalhaut), \\. 
 
 Cephetis is a large and straggling constellation which reaches 
 nearly to the North Pole. Its chief stars are : a (Alderamin) 
 2i ; ft y, C, i?, i, all about 3$. 
 
 Grus (The Crane) is a southern constellation which, though 
 small, contains a considerable number of important stars. 
 These are : a, 2 ; ft 2| ; y, 3 ; 6, 3^. 
 
 Aqtiarius (The Water-bearer) has for its 2 principal stars 
 /i and a, both about 3 ; 8, <?, 3^ ; and e, f, 3! . 
 21 
 
322 CONSTELLATIONS, fcA., 22 H. 2$ M. TO OH. O M. 
 
 Lacerta (The Lizard) is a small northern constellation, of 
 which the largest star, a, is only 4 : but there are 1 5 other stars 
 up to 5i 
 
 Pegasus (The Winged Horse). The so-called " Square of 
 Pegasus " (of which a Andromeda, sometimes called d Pegasi, 
 is one member) is familiar to most star-gazers. The chief stars 
 of Pegasus are : e, a (Markab), /3 (Scheat), all about 2^ ; y 
 (Algenib), 13 > 3 ; 3^ ; and /*, 0, 3|. There are 30 stars 4 to sJr. 
 
 Toucan (The American Goose). This southern constellation 
 only includes one bright star, a 2}. 
 
 Octans (The Octant) is the constellation which includes the 
 South Pole. The brightest star is /u, 3! ; but the nearest star to 
 the Pole is <r, $f . 
 
APPENDIX I. 
 
 STATISTICS RESPECTING THE PLANETS 
 AND THEIR SATELLITES. 
 
 ijrs 
 
 X cs J3 
 <J O 
 
 c >> ~ 
 SoS 
 
 'S o 
 
 lO 1-1 
 
 o\ o 
 
 OO 
 TJ- 
 
 n 
 
 ?o 
 
 VI 
 
 I I I 
 
 bb 
 
 1-1 <N 00 
 
 Ti- 
 
 VO 
 
 vO QO CO 
 CO VO CO t^ 
 rr O 
 
 ^ 
 
 o^^o 
 
 i-i ro VO 
 
 cot-^o ION IOM O 
 O O '<-> io O\ ON O 
 
 S .S | 
 
 S > H S 
 323 
 
SOME STATISTICS OF THE SATELLITES OF 
 THE PLANETS. 
 
 Name or 
 Number. 
 
 Inclination 
 of Orbit. 
 
 Eccen- 
 tricity. 
 
 Mean Daily 
 Motion. 
 
 Sidereal 
 Period. 
 
 Mass. 
 
 THE SATELLITE OF THE EARTH. 
 
 
 O 1 tt 
 
 
 o / // 
 
 d. h. m. 
 
 
 The Moon 
 
 5 8 47 
 
 0-0549 
 
 13 10 35 
 
 27 7 43 
 
 0-012552 
 
 THE SATELLITES OF MARS. 
 
 
 o / 
 
 
 
 
 d. h. m. 
 
 
 Phobos . 
 
 27 28 
 
 0-0217 
 
 1128-8 
 
 7 39 
 
 ? 
 
 Deimos . 
 
 27 24 
 
 0-0031 
 
 285-1 
 
 i 6 17 
 
 ? 
 
 THE SATELLITES OF JUPITER. 
 
 
 o / 
 
 
 o 
 
 d. h. m. 
 
 
 V . . 
 
 2 2O 
 
 O'OO5O 
 
 722-6 
 
 o ii 57 
 
 ? 
 
 I . . 
 
 2 8 
 
 ? 
 
 203-4 
 
 i 18 27 
 
 00000 1 
 
 II . . 
 
 I .38 
 
 ? 
 
 107-3 
 
 3 13 13 
 
 O'OOOO2 
 
 Ill . . 
 
 i 59 
 
 O'OCOI 
 
 50-3 
 
 7 3 42 
 
 0-00008 
 
 IV . . 
 
 i 57 
 
 0-0072 
 
 21-5 
 
 16 16 32 
 
 0-00004 
 
 VI . . 
 
 28 56 
 
 0-156 
 
 i*43 
 
 251 
 
 ? 
 
 VII . . 
 
 31 o 
 
 0-024 
 
 i '35 
 
 265 
 
 ? 
 
 VIII . . 
 
 148 52 
 
 0-33 
 
 o'45 
 
 26 months 
 
 ? 
 
 THE SATELLITES OF SATURN. 
 
 , 
 
 
 
 
 d. h. m. 
 
 
 Mimas 
 
 27 29 
 
 0-019 
 
 381-9 
 
 o 22 77 
 
 0-00000007 
 
 Enceladus 
 
 28 4 
 
 0-004 
 
 2627 
 
 i 8 53 
 
 O'OCOOOO2 
 
 Tethys . 
 
 28 40 
 
 ? 
 
 190-6 
 
 I 21 l8 
 
 O'OOOOOI I 
 
 Dione 
 
 28 4 
 
 O'OO2 
 
 131-5 
 
 2 17 41 
 
 0-0000018 
 
 Rhea . . 
 
 28 22 
 
 0-0009 
 
 79-6 
 
 4 12 25 
 
 0-0000040 
 
 Titan . . 
 
 2 7 39 
 
 O-028 
 
 22'5 
 
 15 22 41 
 
 0-0002127 
 
 Themis . 
 
 39 6 
 
 0-23 
 
 17.27 
 
 2O 2O 24 
 
 ? 
 
 Hyperion. 
 
 27 14 
 
 0-129 
 
 16-9 
 
 21 6 38 
 
 ? 
 
 lapetus . 
 
 18 28 
 
 O-O28 
 
 4'5 
 
 79 7 56 
 
 O'OOOOI 
 
 Phrebe . 
 
 i/5 5 
 
 0-I65 
 
 0-6 
 
 55 I0 34 
 
 ? 
 
 THE SATELLITES OF URANUS. 
 
 
 o / 
 
 
 
 
 d. h. m. 
 
 
 Ariel . . 
 
 97 5 
 
 O'O2 
 
 I42-8 
 
 2 12 29 
 
 \Between 
 
 Umbriel . 
 
 98 2 
 
 O'O I 
 
 86-8 
 
 4 3 27 
 
 o-oooo i 
 
 Oberon . 
 
 98 i 
 
 ? 
 
 4i-3 
 
 8 16 56 
 
 and 
 
 Titania . 
 
 98 17 
 
 ? 
 
 26-7 
 
 13 " 7 
 
 } 0-00005 
 
 THE SATELLITE CF NEPTUNE. 
 
 
 O 1 
 
 
 
 
 d. h. m. 
 
 
 
 142 40 
 
 O-OO7 
 
 61-2 
 
 5 21 2 
 
 ? 
 
 (From the Connaissance des Temps, 1912.) 
 324 
 
APPENDIX II. 
 
 CATALOGUE OF CELESTIAL OBJECTS 
 EASY FOR SMALL TELESCOPES. 
 
 THE following Catalogue includes, with objects already men- 
 tioned, others which may be seen without difficulty in small 
 telescopes ; though, to bring out their specially attractive 
 features, large telescopes may often be necessary. 
 
 PLANETS. 
 
 MERCURY. 
 
 VENUS. 
 
 MARS. 
 
 CERES. 
 
 JUPITER. 
 
 SATURN. 
 
 DOUBLE STARS, CLUSTERS, AND NEBULA. 1 
 
 No double star is included unless bright enough to be easily 
 found (as a single star) with the naked eye, and unless the 
 two components are at least 4" or 5" apart. 
 
 No. 
 
 Name. 
 
 R.A. 
 
 Dec!. 
 
 Description. 
 
 I 
 
 2 
 
 3 
 
 47 Toucani . 
 31 M Andro- 
 raedae . . . 
 r) Cassiopeia; . 
 
 h. m. s. 
 
 o 19 36 
 
 o 37 19 
 o 43 3 
 
 -72 3 
 
 + 4 43 
 + 57 J 7 
 
 Superb globular cluster. 
 
 " The Great Nebula." 
 Double star, mags. 4, 
 7 : dist. 5". 
 
 Extracted from The Cycle of Celestial Objects by Smyth and Chambers, 
 d ed., price 6s. An indispensable companion to every telescope. 
 
 325 
 
326 
 
 APPENDIX. 
 
 No. 
 
 Name. 
 
 R.A. 
 
 Decl. 
 
 Description. 
 
 
 
 h. m. s. 
 
 , 
 
 
 4 
 
 Nubecula Minor 
 
 o 49 8 
 
 -73 55 
 
 Mass of nebula. 
 
 5 
 
 7 Arietis . . . 
 
 I 48 2 
 
 + 18 18 
 
 Double star, mags. 4^, 
 
 
 
 
 
 5 : dist. 8". 
 
 6 
 
 7 Andromedce . 
 
 i 57 45 
 
 + 41 5 1 
 
 Double star, mags. 3^, 
 
 
 
 
 
 5^ : dist. 10". 
 
 7 
 
 33 y VIPersei. 
 
 2 12 2 
 
 + 56 41 
 
 Double cluster in fine 
 
 
 
 
 
 field. 
 
 8 
 
 o Ceti . . . 
 
 2 14 17 
 
 - 3 25 
 
 Celebrated variable, 
 
 
 
 
 
 max. mag. 2 : fiery 
 
 
 
 
 
 red, invisible at min. 
 
 9 
 
 a Ceti . . . 
 
 2 57 3 
 
 + 3 4i 
 
 Orange star, mag. 2^. 
 
 10 
 
 |8 Persei . . . 
 
 3 i 39 
 
 + 40 34 
 
 Variable star, max. 2, 
 
 
 
 
 
 min. 4. 
 
 ii 
 
 77 Tauri . 
 
 3 4i 3 2 
 
 + 23 47 
 
 Chief star in the 
 
 
 
 
 
 " Pleiades." 
 
 12 
 
 5 Orionis . . 
 
 5 26 53 
 
 O 22 
 
 Double star, mags. 2 
 
 
 
 
 
 and 7 : dist. 53" 
 
 J 3 
 
 I M Tauri . . 
 
 5 28 27 
 
 + 21 57 
 
 "The Crab" nebula. 
 
 H 
 
 42 M Orionis 
 
 5 3 20 
 
 - 5 27 
 
 "The Great Nebula in 
 
 
 
 
 
 Orion" surrounding 
 
 
 
 
 
 the star 6. 
 
 15 
 
 a- Orionis . . 
 
 5 33 33 
 
 - 2 37 
 
 Multiple star, mags. 4, 
 
 
 
 
 
 8, and 7: dist. 12" and 
 
 
 
 
 
 42" : other stars. 
 
 16 
 17 
 
 30 Doradus . . 
 35 MGeminorum 
 
 5 39 29 
 6 2 40 
 
 -69 9 
 
 + 24 21 
 
 In the Nubecula Major. 
 Fine cluster of stars. 
 
 18 
 
 5 Lyncis . . . 
 
 6 18 6 
 
 + 58 28 
 
 Fiery red star, mag. 5^. 
 
 19 
 
 41 M Canis 
 
 
 
 
 
 Majoris . . 
 
 6 42 39 
 
 -20 37 
 
 Cluster of stars. 
 
 20 
 
 fj, Canis Majoris 
 
 6 51 32 
 
 -13 55 
 
 Fiery red double star, 
 
 
 
 
 
 mags. 5^ and 9^ : dist. 
 
 
 
 
 
 3"- 
 
 21 
 
 a Geminorum . 
 
 7 28 13 
 
 + 32 6 
 
 Double star, mags. 3 
 
 
 
 
 
 and 3^ : dist. 5". 
 
 22 
 
 7 Argils . . . 
 
 S 6 26 
 
 -47 o 
 
 Double star, mags. 2 
 
 
 
 
 
 and 6 : dist. 42". 
 
 23 
 
 44 M Cancri 
 
 8 34 30 
 
 + 20 17 
 
 Loose cluster,"Prsesepe." 
 
 24 
 
 77 Argus . . . 
 
 10 41 10 
 
 -59 9 
 
 "The Great Nebula in 
 
 
 
 
 
 Argo," surrounding 
 
 
 
 
 
 the star 77. 
 
APPENDIX. 
 
 327 
 
 No. 
 
 Name. 
 
 R.A. 
 
 Decl. 
 
 Description. 
 
 
 
 h. m. s. 
 
 1 
 
 
 25 
 
 54 Leonis . . 
 
 ie 50 12 
 
 + 25 17 
 
 Double star, mags. 4^ 
 
 
 
 
 
 and 7 : dist. 6". 
 
 26 
 
 a Crucis . . . 
 
 12 21 O 
 
 -62 33 
 
 Quintuple star, mags. i|, 
 
 
 
 
 
 2, and 5: dist. 5",9o' r . 
 
 27 
 
 y Crucis . . . 
 
 12 25 36 
 
 -56 33 
 
 Star, mag. 2, Companion, 
 
 
 
 
 
 mag. 5 : dist. 120". 
 
 28 
 
 7 Virginis . . 
 
 12 36 36 
 
 - o 54 
 
 Binary star, both mag. 
 
 
 
 
 
 4 : dist. 6". 
 
 29 
 
 K Crucis . . . 
 
 12 47 42 
 
 -59 48 
 
 Remarkable cluster. 
 
 30 
 
 a Canum Venat . 
 
 12 51 2O 
 
 + 38 51 
 
 Double star, mags. 2| 
 
 
 
 
 
 and 6| : dist. 20". 
 
 31 
 
 f Ursae Majoris 
 
 13 19 54 
 
 + 55 27 
 
 Double star, mags. 3 and 
 
 
 
 
 
 5 : dist. 14" : Alcor, 
 
 
 
 
 
 mag. 5, is distant I if . 
 
 32 
 
 w Centauri . . 
 
 13 20 45 
 
 -46 48 
 
 Large globular cluster. 
 
 33 
 
 a Centauri . . 
 
 H 32 47 
 
 -60 26 
 
 Double, mags. I and 2, 
 
 
 
 
 
 dist. 22". 
 
 34 
 
 TT Bootis . . . 
 
 14 36 2 
 
 + 16 50 
 
 Double star, mags. 3^ 
 
 
 
 
 
 and 6 : dist. 6". 
 
 35 
 
 )8 Librae . . . 
 
 15 ii 37 
 
 - 9 o 
 
 Mag. 2| : pale green 
 
 
 
 
 
 colour. 
 
 36 
 
 5 M Librae . . 
 
 i5 13 27 
 
 + 2 28 
 
 Loose cluster. 
 
 37 
 
 Scorpii . . . 
 
 15 58 52 
 
 -ii 6 
 
 Double star, mags. 4 5 
 
 
 
 
 
 and 7^ : dist. 7" ; 
 
 
 
 
 
 A also double. 
 
 38 
 
 j3 Scorpii . . . 
 
 15 59 37 
 
 -19 3i 
 
 Double star, mags. 2 
 
 
 
 
 
 and 5! : dist. 13" ; 
 
 
 
 
 
 A also double. 
 
 39 
 
 v Scorpii . . . 
 
 16 6 ii 
 
 19 12 
 
 Double star, mags. 4 
 
 
 
 
 
 and 7: dist. 40"; both 
 
 
 
 
 
 stars also double. 
 
 40 
 
 a Scorpii . . . 
 
 16 23 16 
 
 26 12 
 
 Double star, mags, i 
 
 
 
 
 
 and 7 : dist. 3" ; fiery 
 
 
 
 
 
 red star. 
 
 4i 
 
 13 M Herculis . 
 
 16 38 6 
 
 + 36 37 
 
 Very bright globular 
 
 
 
 
 
 cluster. 
 
 42 
 
 a Herculis . . 
 
 17 10 5 
 
 + 14 3 
 
 Double star, mags. 3^ 
 
 
 
 
 
 and 5! : dist. 5". 
 
 43 
 
 92 M Herculis . 
 
 17 14 4 
 
 + 43 H 
 
 Globular cluster. 
 
 44 
 
 8 M Sagittarii . 
 
 17 57 45 
 
 -24 22 
 
 Bright irregular nebula. 
 
328 
 
 APPENDIX. 
 
 No. 
 
 Name. 
 
 R.A. 
 
 Decl. 
 
 Description. 
 
 
 
 h. m. s. 
 
 , 
 
 
 45 
 
 17 M Scuti So- 
 
 
 
 
 
 bieskii . . . 
 
 18 14 50 
 
 16 14 
 
 "The Omega Nebula." 
 
 46 
 
 e Lyroe 
 
 18 41 i 
 
 + 39 34 
 
 Double - double and 
 
 
 
 
 
 multiple star. 
 
 47 
 
 II M Antinoi . 
 
 18 45 45 
 
 - 6 23 
 
 Loose cluster. 
 
 48 
 
 57 M Lyrse . . 
 
 18 49 50 
 
 + 32 54 
 
 Annular Nebula. 
 
 49 
 
 Q Serpentis 
 
 18 51 15 
 
 + 4 5 
 
 Double star, mags. 4| 
 
 
 
 
 
 and 4 : dist. 21". 
 
 5 
 
 /3Cygni . . . 
 
 19 26 41 
 
 + 27 45 
 
 Double Star, mags. 3 
 
 
 
 
 
 and 7 : dist. 34". 
 
 51 
 
 X C y8 ni 
 
 19 46 44 
 
 + 32 40 
 
 Variable star, max. mag. 
 
 
 
 
 
 4, and red : invisible 
 
 
 
 
 
 at minimum. 
 
 52 
 
 27 M Vulpeculoe 
 
 *9 55 M 
 
 + 22 26 
 
 "The Dumb -bell" 
 
 
 
 
 
 Nebula. 
 
 53 
 
 a? Capricorn! . 
 
 2O 12 30 
 
 -12 51 
 
 Wide pair of stars, mags. 
 
 
 
 
 
 3 and 4 : dist. 376" ; 
 
 
 
 
 
 a multiple object. 
 
 54 
 
 /3 2 Capricorni . 
 
 20 15 24 
 
 -15 5 
 
 Wide pair of stars, mags. 
 
 
 
 
 
 35- and 7 : dist. 205". 
 
 55 
 
 7 Delphini . . 
 
 2O 42 I 
 
 + 15 46 
 
 Double star, mags. 4 
 
 
 
 
 
 and 6^: dist. n". 
 
 56 
 
 15 M Pegasi . 
 
 21 28 15 
 
 - i 16 
 
 Globular cluster. 
 
 57 
 
 |8 Cephei . . . 
 
 21 27 22 
 
 470 7 
 
 Double star, mags. 3 
 
 
 
 
 
 and 8 : dist. 13". 
 
 58 
 
 2 M Aquarii 
 
 21 28 15 
 
 - i 16 
 
 Fine globular cluster. 
 
 59 
 
 /j, Cephei . . . 
 
 21 40 26 
 
 + 58 19 
 
 Variable star, max. mag. 
 
 
 
 
 
 4, min. 6 : deep garnet 
 
 
 
 
 
 in colour. 
 
 60 
 
 5 Cephei . . . 
 
 22 25 27 
 
 + 57 54 
 
 Variable star, max. mag. 
 
 
 
 
 
 3^, min. 45 ; also 
 
 
 
 
 
 double, Companion 
 
 
 
 
 
 mag. 7 : dist. 40". 
 
 61 
 
 8 Andromedse . 
 
 23 13 7 
 
 + 48 27 
 
 Fiery red star, mag. 5. 
 
 62 
 
 30 Piscium . . 
 
 23 56 49 
 
 - 6 34 
 
 Fiery red star, mag. 4^. 
 
INDEX. 
 
 The titles of the chapters are in small capitals. 
 
 Achromatism of telescopes, 258 
 Adams, J. C., his researches as to 
 Neptune, 103 ; meteor comets, 188 
 Aerolites, 188 
 Age of the Moon, 27 
 Airy, Sir G. B., 103 
 Algol, /3 Persei, 212 
 Almanacks, 89, 290 
 Altazamuth mounting, 260 
 Anagram on Venus, 76 
 Andromeda (constellation), 310, 313; 
 meteors of, 174 ; Great Nebula in, 
 235 
 
 Annular eclipses of the Sun, 116 
 Annular nebulae, 227, 232 
 Aphelion, 59 
 Apogee, 116 
 Apparent movements of the planets 
 
 56 
 
 Appendix I., Statistics respecting the 
 Planets, 323 ; Appendix II., Cata- 
 logue of Celestial Objects, 325 
 Aquarius (constellation), 312, 321 ; 
 
 meteors in, 174 
 
 Areas, Equal, Kepler's I^aw of, 60 
 Argo (constellation), 311, 316; Great 
 
 Nebula in, 238 ; Star TJ in, 238 
 Ascension, Right, 251, 310 
 Asteroids, 109 
 
 Astrca (Minor Planet), 108 ; name sug 
 gested for Uranus, 100 
 
 329 
 
 Astronomy, Different branches of, 2 
 Atlases, Celestial, 246 
 Aurora Borealis, 15 
 
 Axial rotation of the planets, 323 ; 
 of the Earth, 192 
 
 Baily's Beads, 122 
 
 Barnard, E. E-, 97 
 
 Bayer, J., his Star Atlas, 197 
 
 Beer and Madler's Map of the Moon, 29 
 
 Belts of Jupiter, 84 ; of Saturn, 96 ; 
 
 of Uranus, 101 
 Berthon, Rev. E- I/., his observatory, 
 
 279 
 
 Biela's Comet, 186 
 Binary stars, 207 
 
 Birds during eclipses of the Sun, 119 
 Bode, J. E-, his so-called I/aw, 107 ; 
 
 suggests a name for Uranus, 100 
 Bond, G. P., 91 
 Books for use in an observatory, 246, 
 
 325 
 
 " Bore " on rivers, 52 
 Borelly's Periodical Comet, 158, 169 
 Bouvard, A., 102 
 Bredechin, his classification of the 
 
 tails of comets, 154 
 Brodie, C. G., 182 
 
 Brooks, W. R., comets discovered by, 
 145, 158, 169, 17* 
 
330 
 
 INDEX. 
 
 Brorsen's Periodical Comets, 158, 160 
 Burnham, S. W., 208 
 
 Calendar, Reform of, 285 
 
 Calorific rays of the Sun, 23 ; of the 
 
 Moon, 39 
 Cancer (constellation), 311, 316; 
 
 " Praesepe " in, 228 
 Canes Venatici (constellation), 311, 
 
 318 ; spiral nebula in, 233 
 Cassegrainian telescope, 257 
 Cassini, J. D., 86 
 Cassiopeia (constellation), 310, 313 ; 
 
 temporary star in, 218 
 Catalogue of celestial objects for small 
 
 telescopes, 325 
 Cepheus, 312, 321 ; variable star in 
 
 214 
 
 Ceres (Minor Planet), 107 
 Cetus (constellation), 310, 313 ; vari- 
 able star in, 211 
 Chaldaean Astronomy, 118 
 Challis, Rev. J., 103, 150 
 Chepstow, Tides at, 48 
 Cheseaux, De, and the comet of 1744, 
 
 152 
 
 Christie, Sir W. H. M., 34 
 Chromatic aberration, 258 
 Chromosphere of the Sun, 13 
 Churchill, W. S., 33 
 Circles for telescopes, 262 
 Circumpolar stars, 195 
 Clapham, T. R., his observatory, 280 
 Clocks for observatories, 263 
 Clusters and nebulae, 226 
 Coggia's Comet of 1874, 167 
 Coloured stars, 209 
 Colours Of stars, 209 
 Columbus, Christopher, anecdote of, 
 
 139 
 Coma Berenices (constellation), 311, 
 
 318 ; stars in, 229 
 Coma of a comet, 148 
 COMETS, 144; periodical, 156; re- 
 
 markable, 164 ; meteors connected 
 
 with, 187 
 Comparative sizes of the Sun and 
 
 planets, 63 
 
 Complementary colours, 209 
 Conjunction of the planets, 57 ; see 
 
 also 64 
 CONSTELLATIONS, THE, 244 ; lists of, 
 
 310 ; how to study, 245 ; see also 
 
 313 et seq. 
 
 CONSTELLATIONS, TABLE OF THE, 310 
 Corona in eclipses of the Sun, 123 
 " Crab Nebula " in Taurus, 326 
 Craters on the Moon, 29 
 Cross, The Southern, 317 
 Cygnus (constellation), 312, 321 ; 
 
 temporary star in, 222 ; nebulae in, 
 
 240 
 
 D 
 
 Daniel's Comet, 170 
 
 Darkness during eclipses, 119 
 
 D' Arrest's Comet, 158 
 
 Dawes, W. R., 12, 91, 208 
 
 Day as a unit of time, 287 ; divisions 
 
 of, 288 
 Declination axis of an equatorial, 
 
 260 
 Declination of a heavenly body, 251, 
 
 310 
 Denning, W. F., 69 ; his observations 
 
 of meteors, 175 
 Diagonal eye-piece, 257 
 Diameter of the Sun and planets, 
 
 323 
 
 Dimensions of the solar system, 63 
 Diurnal movements of the heavens, 
 
 193 
 
 Di Vice's long-period comet, 160 
 Domes for observatories, 274 
 Donati's Comet of 1858, 146 
 Dorado (constellation), 311, 314; 
 
 nebula in, 237 
 Double stars, 205 
 " Dumb-bell " Nebula, 240 
 
INDEX. 
 
 331 
 
 Earth, 55 
 
 Earth-shine, 36 
 
 Eccentricity of orbits, 60 
 
 ECLIPSES, 113 
 
 Eclipse expeditions, 129 
 
 Eclipses, General outlines of, 113; 
 future, 127 
 
 Eclipses of Jupiter's satellites, 143 
 
 Eclipses of the Sun, 114, 121 ; ob- 
 served at sea, 135 
 
 Eclipses of the Moon, 116 
 
 Ecliptic, Obliquity of, 58 
 
 Ellipse, Properties of, 60 ; how to 
 draw, 6 1 
 
 Elliptic nebulae, 227, 232 
 
 Elongation of Mercury, 68 
 
 Encke, J. F., 104 
 
 Encke's Comet, 158 
 
 Equation of time, 44, 298 
 
 Equatorial instrument, 260 
 
 Eros (Minor Planet), no 
 
 " Establishment of the Port," 45 
 
 Eye-pieces, 258 
 
 Faculae on the Sun, 24 
 Faye's Periodical Comet, 158 
 Finlay's Periodical Comet, 158 
 Fire-balls, 178, 180 
 Flames, Red, on the Sun, 122 
 Flamsteed, Rev. J., 198 
 Foundations for an observatory, 268 
 Fraiinhofer, J., 303 
 Full Moon, 27, 36 
 
 Galaxy, 242 
 
 Galilean telescope, 259 
 
 Galle, J. G., 91, 104 
 
 Gemini (constellation), 311, 315 ; 
 
 meteors in, 175, 177 
 Georgium Sidus, 100 
 Giacobini's Comet, 169 
 
 Gladstone, W. E., 253 
 Globular clusters, 230 
 Granulations on the Sun's surface, 7 
 Gravitation, Theory of, 59, 206 
 Greenwich Observatory, 201 
 Gregorian calendar, 286 
 Gregorian telescope, 257 
 Grimthorpe, I^ord, 2 
 GROUPS OF STARS AND NEBULA, 226 
 
 II 
 
 Hale, G. E-, 20 
 
 Halley, E., 160 
 
 Halley's Comet, 161, 170 
 
 Harvard Photometry cited, 196 
 
 Harvest Moon, 32 
 
 Heat-rays of the Sun, 23 
 
 Helium, 306, 308 
 
 Hencke, K. C., his search for minor 
 
 planets, 108 
 Hercules (constellation), 312, 320; 
 
 cluster in, 230 
 Herschelian telescope, 257 
 Herschel, Sir J. F. W., 62, 199 
 Herschel, Sir W., 98, 109, 205 
 High- water, 42, 43 
 Hipparchus, 285 
 Holmes's Periodical Comet, 158 
 Homer cited, 253 
 " Horse-shoe " Nebula, 239 
 Hour-circle, 262 
 Hours, 283 
 
 Huggins, Sir W., 7, 232, 233, 308 
 Hunter's Moon, 33 
 Hyades, The, in Taurus, 227 
 Hygre (tidal phenomenon), 52 
 Hyperbola, 157 
 Hyperbolic comets, 157 
 
 Inclination of the Ecliptic, 59, 117; 
 
 of a planet's orbit, 59 
 Inferior Planets, 56 
 
332 
 
 INDEX. 
 
 Intra-Mercurial planets, 66 
 
 Iron, Meteoric, 189 
 
 Isle of Wight, Tides around, 51 
 
 Johnson, Rev. S. J., 127 
 Johnston, A. K., 50 
 Jupiter, 84 
 
 K 
 
 Kepler's I,aws, 59 
 
 Klein, H. J., his Atlas, 246 
 
 Kullmer's Star-finder, 247 
 
 199 
 
 " gagging " of the tides, 46 
 
 I^alande, J. J., 100 
 
 I^angley, S. P., 7, 12 
 
 I/a Place, 100 
 
 Ivassell, W., 1 01 
 
 I,aVerrier, U. J. J., 103 
 
 I<eo (constellation), 311, 317 ; meteors 
 in, 174, 187 
 
 Leonid meteors, 187 
 
 I^ewis, Sir G. C., 199 
 
 I<ibra (constellation), 312, 318 ; cluster 
 in, 230 
 
 I,ibrations of the Moon, 31 
 
 Ivight-pressure, 156 
 
 Ivight, transmission of , 90 
 
 lyow water, 43 
 
 Lumtire Cendree on the Moon, 36 
 
 3+yra (constellation), 312, 32O ; an- 
 nular nebula in, 232 ; meteors in, 
 174 J multiple star e in, 328 
 
 M 
 
 *Madler, J. H., 29 
 Magellanic Clouds, 241 
 Magnetism, terrestrial and solar spots 
 15 
 
 Magnitude of stars, 196, 200 ; list of 
 stars of the first magnitude, 248 
 
 Magnitude of the solar system, popular 
 illustration of, 62 
 
 Maps, Astronomical, 245 
 
 Mars, 77 ; phases of, 78 ; markings 
 on, 8 1 ; satellites of , 83 ; see also 58 
 
 Maunder, B. W., 17, 299 
 
 Mean distance of a planet, 323 
 
 Medal struck by monks, 1680, 153 ; 
 the Warner Prize, 164 
 
 Mediterranean Sea, tides in, 48 
 
 Mercury, 68 ; phases of, 57 ; transits 
 of, 142 ; see also, 56 
 
 Messier, his catalogue of nebulae, 229 
 
 Meteoric stones, 189 
 
 Meteors, Telescopic, 173 
 
 Milky Way, 242 
 
 Minor planets, 106 
 
 MiraCeti, 212, 326 
 
 Months, 283, 285 
 
 Montigny, C., his researches on twink- 
 ling, 203 
 
 MOON, THE, 26 ; phases of, 27 ; and 
 the weather, 34 ; genuine weather 
 influences, 37 ; as a measurer of time, 
 285, 287 ; mountains on, 28 
 
 Moonlight, Brightness of, 34 
 
 Moore, Admiral, 54 
 
 Morehouse's Comet, 170 
 
 Motions of the planets, 55, 57, 58 
 
 Mountains suspected on Mercury, 69 ; 
 on Venus, 74 
 
 Multiple stars, 205 
 
 N 
 
 Naked-eye, number of stars visible 
 to, 201 
 
 Nasmyth, J., "his willow-leaves" on 
 the Sun, 7 
 
 Nautical Almanack, 89, 100, 294 
 
 Neap Tides, 45 
 
 Nebulae, 231 ; varieties of, 227 ; dis- 
 tribution of, 241 
 
INDEX:. 
 
 333 
 
 Nebulous stars, 227 
 
 Needle, Magnetic, variation in the 
 
 declination of, 16 
 Neptune, 101 
 New stars, 218 
 Newton, Sir I., 160, 302 
 Newtonian telescope, 257 
 Node, Ascending, 58 ; Descending, 58 
 November meteors (I^onids), 186, 187 
 Nubecula Major, 241 
 Nubecula Minor, 241 
 Nucleus of a Sun-spot, 12 ; of a comet, 
 
 148 
 
 Object-glass, 258 
 Observations of eclipses, 129 
 Observatory, 264 ; construction of, 
 
 264 
 
 Occultations, 143 
 " Omega, nebula, "in ClypeusSobieskii, 
 
 239 
 
 Opera-glass, 259 
 
 Ophiucus, 312, 320 ; new star in, 220 
 Oppolzer, T. von, his catalogue of 
 
 eclipses cited, 128 
 Opposition, Planets in, 57 
 Optical double stars, 205 
 Orbits of planets, 58 ; of comets, 156 ; 
 
 of double stars, 206 ; of meteors, 186 
 Orion (constellation), 311, 315 ; Great 
 
 Nebula in, 236 ; meteors in, 174 
 
 Pacific Ocean, Tides in, 49 
 
 Pallas (Minor Planet), 107 
 
 Parabola, 157 
 
 Parallax, 206 
 
 Pegasus (constellation), 312, 322 ; the 
 
 " square " of, 322 
 Penumbra of a Sun-spot, 12 
 Perigee, 116 
 Perihelion, 59 
 
 Periodic comets, 156, 158, if>o 
 Periodicity of Sun-spots, 14 ; of 
 
 shoo ting stars, 173 
 
 Periods of the planets, 323 ; of comets, 
 158, 160 
 
 Perseus (constellation), 310, 314 ; 
 cluster in, 326; new star in, 219, 
 223 ; meteors in, 173 
 
 Perturbations of Uranus by Neptune, 
 102 
 
 Phases of Inferior Planets, 57 ; of the 
 Moon, 27 ; of Mars, 78 ; of Jupiter, 
 57 ; of Saturn's Rings, 92 
 
 Photometer, 196 
 
 Photometry of the stars, 196 
 
 Photosphere of the Sun, 13 
 
 Pickering, E. C., 224 
 
 Pickering, W. H., 82 ; his classifica- 
 tion of the tails of comets, 155 
 
 Pillar -and-claw stand, 260 
 
 PLANETS GENERALLY, THE, 55 
 
 PLANETS, THE FAMILIAR, 67 
 
 PLANETS, THE I^ESS KNOWN, 98 
 
 Planetary nebulae, 227 
 
 Planetoids. See Minor Planets 
 
 Planispheres, 245 
 
 Plans and specifications of an observa- 
 tory, 264 
 
 Pleiades, 227 
 
 Pole-Star (a Ursse Minoris), 195, 252, 
 
 254 
 
 Pons's Periodical Comet, 160 
 Prsesepein Cancer, 228 
 Prime Meridian, 289 
 "Priming and lagging" of the tides, 
 
 46 
 
 Principia, Newton's, 161 
 Proctor, R. A., 5 
 Prominences, Solar, 122 
 Ptolomy, C., his system, 66 
 
 Q 
 
 Quadrans Muralis (constellation), 
 
 meteors in, 174 
 Quadrature of the Moon, 43 ; planets 
 
 in, 58 
 
 Quadruple stars, 205 
 Quarters of the Moon, 27 
 
334 
 
 INDEX. 
 
 Radiant-points of meteors, 174 
 
 Radius-vector of a planet, 60 
 
 Rainfall and Sun-spots, 17 
 
 Range of the tides, 45 
 
 " Red Flames " in eclipses of the Sun j 
 
 122 
 
 Red spot on Jupiter, 85 
 Reflecting telescopes, 256 
 Refracting telescopes, 256 
 " Rice-grains " on the Sun, 6 
 Right Ascension, 251 
 Rings of Saturn, 91 
 Roberts, I., 233 
 
 Romer, Observations of, on I/ight, 90 
 Rordame's Comet, 168 
 Rosse, Third E)arl of, 232, 233 
 Rotation of the Sun, 10 ; of the 
 planets, 232 
 
 Sagittarius (constellation), 312, 320; 
 
 nebula in, 238 
 Saros, 118 
 Satellites of Mars, 83 ; of Jupiter, 87 ; 
 
 of Saturn, 96 ; of Uranus, 101 ; of 
 
 Neptune, 106 
 Saturn, 91 ; belts of, 96 ; satellites of, 
 
 96 
 
 Schiaparelli, 70 
 Schmidt, J.F.J., 222 
 SchrSter, J. J., 73 
 
 Schwabe, H., observations of Sun- 
 spots, 14 
 Scorpio (constellation), 312, 319 ; 
 
 variable cluster in, 231 
 Scutum Sobieskii (constellation), 312, 
 
 328 ; nebula in, 239 
 Seabroke, G. M., double-star observer, 
 
 208 
 
 Seas, I^unar, 29 
 Secchi, A., 208, 301 ; his Star-types, 
 
 204, 306 
 Semi-axis-major of a planet's orbit, 
 
 62 
 
 Shadow-bands in eclipses of the Sun, 
 124 
 
 Shadow cast by Venus, 74 ; of the Moon 
 during eclipses of the Sun, 123 
 
 SHOOTING-STARS, 172 
 
 Signs of the Zodiac, 284 
 
 Silvered-glass reflectors, 257 
 
 Site for an observatory, 265, 266 
 
 Smyth, Admiral, W. H., 325 
 
 Snow suspected on Mars, 80 
 
 SPECTROSCOPE, THE, ASTRONOMIC- 
 ALLY, 301 
 
 Spectrum analysis, 301 
 
 Spherical aberration, 258 
 
 Sporadic meteors, 173 
 
 Spots on the Sun, 9 ; on Jupiter, 84 ', 
 on Saturn, 96 
 
 Spring Tides, 45 
 
 Standard time, 290 
 
 Stands for telescopes, 260 
 
 STARS, THE, 191 
 Star -finder, Kullmer's, 247 
 Stars, Magnitudes of, 200 ; double, 
 205 ; binary, 206 ; multiple, 205 ; 
 variable, 211; temporary, 218; 
 coloured, 209 
 Stewart, B., 19 
 Stone, U. J., 18, 137 
 Struve, F. G. W., 208 
 Styles old and new, 286 
 SUN, THE, 5 
 
 Sun, Spots on, 9 ; periodicity of, 14 
 Superior Planets, 56 
 Swift, Dean, 83 
 
 Swift's Periodical Comets, 158, 168 
 Symbols of the Major Planets, 323 
 
 Tables of the Planets and Satellites, 
 
 323 
 
 Tails of comets, 153 
 Taurus (constellation), 311, 314 ; 
 
 "Crab Nebula" in, 326; meteors 
 
 in, 175 ; the Pleiades and Hyadesin, 
 
 227 
 
INDEX. 
 
 335 
 
 TELESCOPES, 256 
 
 Telescopes, various kinds of, 256 ; 
 hints as to the purchase of, 259 ; 
 stands for, 260 ; equatorial mount- 
 ing of, 260 
 
 Telescopic comets, 147 
 
 Telescopic meteors, 173 
 
 Tempel, W., 228 
 
 Tempel's Periodical Comets, 158 
 
 Temporary stars, 218 
 
 Terminator of the Moon, 30 
 
 Tidal-day, Definition of , 44 
 
 TIDES, THE, 41 
 
 TIME AND ITS MEASUREMENT, 283 
 
 Time, Equation of, 298 
 
 Time gun, 23 
 
 Total eclipses of the Sun, 119, 121 ; 
 of the Moon, 138 
 
 Toucan (constellation), 312, 322; 
 cluster in, 229, 239, 325 
 
 Trans-Neptunian planet (the sup- 
 posed), 66 
 
 Transit Circle, 298 
 
 Transit Instrument, 294 
 
 Transit of planets, 141 ; of Mercury, 
 142 ; of Venus, 142 ; of Jupiter's 
 satellites, 143 
 
 Trapezium of Orion, 236 
 
 Triple stars, 205 
 
 Tuttle's Periodical Comet, 158 
 
 Twinkling, 202 
 
 Tycho Brahe, 218 ; his system, 66 
 
 U 
 
 Uranus, 98 ; general account of, y8 ; 
 
 satellites of , 101 
 Ursa Major (constellation), 311, 317; 
 
 planetary nebula in, 235 
 
 Variable nebula, 231 
 
 Variable stars, 211 
 
 Velocity of light, 90 ; of the tidal wave, 
 5i 
 
 Venus, 73 ; transits of, 142 ; sus- 
 pected influence on Sun-spots, 19 ; 
 phases of, 57 
 
 Vesta (Minor Planet), 107 
 
 Vorticose movements on the Sun, 20 
 
 Vulpecula (constellation), 312, 321; 
 " Dumb-bell Nebula " in, 240 
 
 W 
 
 Weather influences imputed to the 
 
 Moon, 34 
 
 Webb, Rev. T. W., 181 
 Week, Days of, 283, 286 
 Westphal's Periodical Comet, 160 
 " Whirlpool" or "Spiral" nebulae, 22 
 " Willow leaves " on the Sun, 7 
 Wilson (Professor at Glasgow), 19 ; 
 
 his theory of Sun-spots, 19 
 Winnecke's Periodical Comet, 158 
 Wolf, Dr., his Periodical Comet, 158 
 Wolf, R., his observations on the Sun, 
 
 17 
 Wollaston, F., his observations on the 
 
 Sun, 303 
 
 Year, various kinds of, 284 ; length of 
 
 284 
 
 Zodiac, motion of the Sun through, 
 
 285 
 Zone of Sun-spots, 14 
 
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 LONDON AND AYLESBURY. 
 
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