The Story of the Heavens

Appendix 558

LIST OF PLATES.

PLATE

I. The Planet Saturn Frontispiece

II. A Typical Sun-spot To face page 9

A. The Sun " " 44

III. Spots and Faculæ on the Sun " " 37

IV. Solar Prominences or Flames " " 57

V. The Solar Corona " " 62

VI. Chart of the Moon's Surface " " 81

B. Portion of the Moon " " 88

VII. The Lunar Crater Triesnecker " " 93

VIII. A Normal Lunar Crater " " 97

IX. The Lunar Crater Plato " " 102

X. The Lunar Crater Tycho " " 106

XI. The Planet Jupiter " " 254

XII. Coggia's Comet " " 340

C. Comet A., 1892, 1 Swift " " 358

XIII. Spectra of the Sun and of three Stars " " 47

D. The Milky Way, near Messier II. " " 462

XIV. The Great Nebula in Orion " " 466

XV. The Great Nebula in Andromeda " " 468

E. Nebulæ in the Pleiades " " 472

F. ô Centauri " " 474

XVI. Nebulæ observed with Lord Rosse's Telescope " " 476

XVII. The Comet of 1882 " " 357

XVIII. Schiaparelli's Map of Mars " " 221

LIST OF ILLUSTRATIONS.

FIG. PAGE

1. Principle of the Refracting Telescope 11

2. Dome of the South Equatorial at Dunsink Observatory, Co. Dublin 12

3. Section of the Dome of Dunsink Observatory 13

4. The Telescope at Yerkes Observatory, Chicago 15

5. Principle of Herschel's Reflecting Telescope 16

6. South Front of the Yerkes Observatory, Chicago 17

7. Lord Rosse's Telescope 18

8. Meridian Circle 20

9. The Great Bear 27

10. Comparative Sizes of the Earth and the Sun 30

11. The Sun, photographed September 22, 1870 33

12. Photograph of the Solar Surface 35

13. An ordinary Sun-spot 36

14. Scheiner's Observations on Sun-spots 38

15. Zones on the Sun's Surface in which Spots appear 39

16. Texture of the Sun and a small Spot 43

17. The Prism 45

18. Dispersion of Light by the Prism 46

19. Prominences seen in Total Eclipses 53

20. View of the Corona in a Total Eclipse 62

21. View of Corona during Eclipse of January 22, 1898 63

22. The Zodiacal Light in 1874 69

23. Comparative Sizes of the Earth and the Moon 73

24. The Moon's Path around the Sun 76

25. The Phases of the Moon 76

26. The Earth's Shadow and Penumbra 78

27. Key to Chart of the Moon (Plate VI.) 81

28. Lunar Volcano in Activity: Nasmyth's Theory 97

29. Lunar Volcano: Subsequent Feeble Activity 97

30. " " Formation of the Level Floor by Lava 98

31. Orbits of the Four Interior Planets 115

32. The Earth's Movement 116

33. Orbits of the Four Giant Planets 117

34. Apparent Size of the Sun from various Planets 118

35. Comparative Sizes of the Planets 119

36. Illustration of the Moon's Motion 130

37. Drawing an Ellipse 137

38. Varying Velocity of Elliptic Motion 140

39. Equal Areas in Equal Times 141

40. Transit of the Planet of Romance 153

41. Variations in Phase and apparent Size of Mercury 160

42. Mercury as a Crescent 161

43. Venus, May 29, 1889 170

44. Different Aspects of Venus in the Telescope 171

45. Venus on the Sun at the Transit of 1874 177

46. Paths of Venus across the Sun in the Transits of 1874 and 1882 179

47. A Transit of Venus, as seen from Two Localities 183

48. Orbits of the Earth and of Mars 210

49. Apparent Movements of Mars in 1877 212

50. Relative Sizes of Mars and the Earth 216

51, 52. Drawings of Mars 217

53. Elevations and Depressions on the Terminator of Mars 217

54. The Southern Polar Cap on Mars 217

55. The Zone of Minor Planets between Mars and Jupiter 234

56. Relative Dimensions of Jupiter and the Earth 246

57-60. The Occultation of Jupiter 255

61. Jupiter and his Four Satellites 258

62. Disappearances of Jupiter's Satellites 259

63. Mode of Measuring the Velocity of Light 264

64. Saturn 270

65. Relative Sizes of Saturn and the Earth 273

66. Method of Measuring the Rotation of Saturn's Rings 288

67. Method of Measuring the Rotation of Saturn's Rings 289

68. Transit of Titan and its Shadow 295

69. Parabolic Path of a Comet 339

70. Orbit of Encke's Comet 346

71. Tail of a Comet directed from the Sun 363

72. Bredichin's Theory of Comets' Tails 366

73. Tails of the Comet of 1858 367

74. The Comet of 1744 368

75. The Path of the Fireball of November 6, 1869 375

76. The Orbit of a Shoal of Meteors 378

77. Radiant Point of Shooting Stars 381

78. The History of the Leonids 385

79. Section of the Chaco Meteorite 398

80. The Great Bear and Pole Star 410

81. The Great Bear and Cassiopeia 411

82. The Great Square of Pegasus 413

83. Perseus and its Neighbouring Stars 415

84. The Pleiades 416

85. Orion, Sirius, and Neighbouring Stars 417

86. Castor and Pollux 418

87. The Great Bear and the Lion 419

88. Boötes and the Crown 420

89. Virgo and Neighbouring Constellations 421

90. The Constellation of Lyra 422

91. Vega, the Swan, and the Eagle 423

92. The Orbit of Sirius 426

93. The Parallactic Ellipse 444

94. 61 Cygni and the Comparison Stars 447

95. Parallax in Declination of 61 Cygni 450

96. Globular Cluster in Hercules 463

97. Position of the Great Nebula in Orion 466

98. The Multiple Star th Orionis 467

99. The Nebula N.G.C. 1499 471

100. Star-Map, showing Precessional Movement 493

101. Illustration of the Motion of Precession 495

THE

STORY OF THE HEAVENS.

"The Story of the Heavens" is the title of our book. We have indeed a wondrous story to narrate; and could we tell it adequately it would prove of boundless interest and of exquisite beauty. It leads to the contemplation of grand phenomena in nature and great achievements of human genius.

Let us enumerate a few of the questions which will be naturally asked by one who seeks to learn something of those glorious bodies which adorn our skies: What is the Sun--how hot, how big, and how distant? Whence comes its heat? What is the Moon? What are its landscapes like? How does our satellite move? How is it related to the earth? Are the planets globes like that on which we live? How large are they, and how far off? What do we know of the satellites of Jupiter and of the rings of Saturn? How was Uranus discovered? What was the intellectual triumph which brought the planet Neptune to light? Then, as to the other bodies of our system, what are we to say of those mysterious objects, the comets? Can we discover the laws of their seemingly capricious movements? Do we know anything of their nature and of the marvellous tails with which they are often decorated? What can be told about the shooting-stars which so often dash into our atmosphere and perish in a streak of splendour? What is the nature of those constellations of bright stars which have been recognised from all antiquity, and of the host of smaller stars which our telescopes disclose? Can it be true that these countless orbs are really majestic suns, sunk to an appalling depth in the abyss of unfathomable space? What have we to tell of the different varieties of stars--of coloured stars, of variable stars, of double stars, of multiple stars, of stars that seem to move, and of stars that seem at rest? What of those glorious objects, the great star clusters? What of the Milky Way? And, lastly, what can we learn of the marvellous nebulæ which our telescopes disclose, poised at an immeasurable distance? Such are a few of the questions which occur when we ponder on the mysteries of the heavens.

The history of Astronomy is, in one respect, only too like many other histories. The earliest part of it is completely and hopelessly lost. The stars had been studied, and some great astronomical discoveries had been made, untold ages before those to which our earliest historical records extend. For example, the observation of the apparent movement of the sun, and the discrimination between the planets and the fixed stars, are both to be classed among the discoveries of prehistoric ages. Nor is it to be said that these achievements related to matters of an obvious character. Ancient astronomy may seem very elementary to those of the present day who have been familiar from childhood with the great truths of nature, but, in the infancy of science, the men who made such discoveries as we have mentioned must have been sagacious philosophers.

Of all the phenomena of astronomy the first and the most obvious is that of the rising and the setting of the sun. We may assume that in the dawn of human intelligence these daily occurrences would form one of the first problems to engage the attention of those whose thoughts rose above the animal anxieties of everyday existence. A sun sets and disappears in the west. The following morning a sun rises in the east, moves across the heavens, and it too disappears in the west; the same appearances recur every day. To us it is obvious that the sun, which appears each day, is the same sun; but this would not seem reasonable to one who thought his senses showed him that the earth was a flat plain of indefinite extent, and that around the inhabited regions on all sides extended, to vast distances, either desert wastes or trackless oceans. How could that same sun, which plunged into the ocean at a fabulous distance in the west, reappear the next morning at an equally great distance in the east? The old mythology asserted that after the sun had dipped in the western ocean at sunset (the Iberians, and other ancient nations, actually imagined that they could hear the hissing of the waters when the glowing globe was plunged therein), it was seized by Vulcan and placed in a golden goblet. This strange craft with its astonishing cargo navigated the ocean by a northerly course, so as to reach the east again in time for sunrise the following morning. Among the earlier physicists of old it was believed that in some manner the sun was conveyed by night across the northern regions, and that darkness was due to lofty mountains, which screened off the sunbeams during the voyage.

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