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diff --git a/25267-8.txt b/25267-8.txt new file mode 100644 index 0000000..419de67 --- /dev/null +++ b/25267-8.txt @@ -0,0 +1,8393 @@ +The Project Gutenberg EBook of Astronomy for Amateurs, by Camille Flammarion + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Astronomy for Amateurs + +Author: Camille Flammarion + +Translator: Frances A. Welby + +Release Date: April 30, 2008 [EBook #25267] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK ASTRONOMY FOR AMATEURS *** + + + + +Produced by Jason Isbell, Greg Bergquist and the Online +Distributed Proofreading Team at https://www.pgdp.net + + + + + + + +[Illustration: Paul Renaud. + +CONTEMPLATION] + + + + + ASTRONOMY FOR + AMATEURS + + + BY + CAMILLE FLAMMARION + AUTHOR OF POPULAR ASTRONOMY + + + _AUTHORIZED TRANSLATION BY_ + FRANCES A. WELBY + + + _ILLUSTRATED_ + + [Illustration] + + + NEW YORK AND LONDON + D. APPLETON AND COMPANY + 1910 + + + + +COPYRIGHT, 1904, BY + +D. APPLETON AND COMPANY + + +_Published October, 1904_ + + + + +TO + +MADAME C.R. CAVARÉ + + ORIGINAL MEMBER OF THE ASTRONOMICAL SOCIETY OF FRANCE + CHÂTEAU DE MAUPERTHUIS + + +MADAME: I have dedicated none of my works, save Stella--offered to the +liberal-minded, the free and generous friend of progress, and patron of +the sciences, James Gordon Bennett, editor of the New York Herald. In +this volume, Madame, I make another exception, and ask your permission +to offer it to the first woman who consented to be enrolled in the list +of members of the Astronomical Society of France, as foundress of this +splendid work, from the very beginning of our vast association (1887); +and who also desired to take part in the permanent organization of the +Observatory at Juvisy, a task of private enterprise, emancipated from +administrative routine. An Astronomy for Women[1] can not be better +placed than upon the table of a lady whose erudition is equal to her +virtues, and who has consecrated her long career to the pursuit and +service of the Beautiful, the Good, and the True. + + CAMILLE FLAMMARION. + + OBSERVATORY OF JUVISY, _November, 1903_. + + + + + CONTENTS + + + CHAPTER PAGE + + INTRODUCTION 1 + + I. THE CONTEMPLATION OF THE HEAVENS 10 + + II. THE CONSTELLATIONS 28 + + III. THE STARS, SUNS OF THE INFINITE. A JOURNEY + THROUGH SPACE 56 + + IV. OUR STAR THE SUN 88 + + V. THE PLANETS. A. MERCURY, VENUS, THE + EARTH, MARS 113 + + VI. THE PLANETS. B. JUPITER, SATURN, URANUS, + NEPTUNE 146 + + VII. THE COMETS 172 + + VIII. THE EARTH 205 + + IX. THE MOON 232 + + X. THE ECLIPSES 259 + + XI. ON METHODS. HOW CELESTIAL DISTANCES + ARE DETERMINED, AND HOW THE SUN IS + WEIGHED 287 + + XII. LIFE, UNIVERSAL AND ETERNAL 317 + + INDEX 341 + + + + + LIST OF ILLUSTRATIONS + + + Contemplation _Frontispiece_ + From a painting by Paul Renaud + + FIG. PAGE + + 1. The great Book of the Heavens is open to all eyes 15 + + 2. The earth in space. June solstice, midday 20 + + 3. The Great Bear (or Dipper) and the Pole Star 34 + + 4. To find the Pole Star 35 + + 5. To find Cassiopeia 37 + + 6. To find Pegasus and Andromeda 37 + + 7. Perseus, the Pleiades, Capella 38 + + 8. To find Arcturus, the Herdsman, and the Northern Crown 40 + + 9. The Swan, Vega, the Eagle 41 + + 10. The Constellations of the Zodiac: summer and autumn; + Capricorn, Archer, Scorpion, Balance, Virgin, Lion 46 + + 11. The Constellations of the Zodiac: winter and spring; + Crab, Twins, Bull, Ram, Fishes, Water-Carrier 47 + + 12. Orion and his celestial companions 48 + + 13. Winter Constellations 51 + + 14. Spring Constellations 52 + + 15. Summer Constellations 53 + + 16. Autumn Constellations 54 + + 17. The double star Mizar 69 + + 18. Triple star [xi] in Cancer 72 + + 19. Quadruple star [epsilon] of the Lyre 73 + + 20. Sextuple star [theta] in the Nebula of Orion 74 + + 21. The Star-Cluster in Hercules 79 + + 22. The Star-Cluster in the Centaur 80 + + 23. The Nebula in Andromeda 81 + + 24. Nebula in the Greyhounds 82 + + 25. The Pleiades 83 + + 26. Occultation of the Pleiades by the Moon 85 + + 27. Stellar dial of the double star [gamma] of the Virgin 86 + + 28. Comparative sizes of the Sun and Earth 93 + + 29. Direct photograph of the Sun 96 + + 30. Telescopic aspect of a Sun-Spot 97 + + 31. Rose-colored solar flames 228,000 kilometers (141,500 + miles) in height, _i.e._, 18 times the diameter of the + Earth 103 + + 32. Orbits of the four Planets nearest to the Sun 115 + + 33. Orbits of the four Planets farthest from the Sun 116 + + 34. Mercury near quadrature 117 + + 35. The Earth viewed from Mercury 119 + + 36. The Evening Star 123 + + 37. Successive phases of Venus 124 + + 38. Venus at greatest brilliancy 126 + + 39. The Earth viewed from Venus 130 + + 40. Diminution of the polar snows of Mars during the + summer 136 + + 41. Telescopic aspect of the planet Mars (Feb., 1901) 137 + + 42. Telescopic aspect of the planet Mars (Feb., 1901) 138 + + 43. Chart of Mars 140 + + 44. The Earth viewed from Mars 144 + + 45. Telescopic aspect of Jupiter 150 + + 46. Jupiter and his four principal satellites 155 + + 47. Saturn 159 + + 48. Varying perspective of Saturn's Rings, as seen from + the Earth 161 + + 49. The Great Comet of 1858 174 + + 50. What our Ancestors saw in a Comet 177 + + After Ambroise Paré (1858) + + 51. Prodigies seen in the Heavens by our Forefathers 178 + + 52. The orbit of a Periodic Comet 182 + + 53. The tails of Comets are opposed to the Sun 185 + + 54. A Meteor 191 + + 55. Shooting Stars of November 12, 1799 196 + + From a contemporary drawing + + 56. Fire-Ball seen from the Observatory at Juvisy, August + 10, 1899 199 + + 57. Explosion of a Fire-Ball above Madrid, February 10, + 1896 200 + + 58. Raphael's Fire-Ball (_The Madonna of Foligno_) 202 + + 59. A Uranolith 203 + + 60. Motion of the Earth round the Sun 222 + + 61. Inclination of the Earth 224 + + 62. The divisions of the globe. Longitudes and latitudes 226 + + 63. To find the long and short months 230 + + 64. The Full Moon slowly rises 234 + + 65. The Moon viewed with the unaided eye 236 + + 66. The Man's head in the Moon 237 + + 67. Woman's head in the Moon 238 + + 68. The kiss in the Moon 239 + + 69. Photograph of the Moon 240 + + 70. The Moon's Phases 241 + + 71. Map of the Moon 247 + + 72. The Lunar Apennines 251 + + 73. Flammarion's Lunar Ring 253 + + 74. Lunar landscape with the Earth in the sky 254 + + 75. Battle between the Medes and Lydians arrested by an + Eclipse of the Sun 266 + + 76. Eclipse of the Moon at Laos (February 27, 1877) 269 + + 77. The path of the Eclipse of May 28, 1900 273 + + 78. Total eclipse of the Sun, May 28, 1900, as observed + from Elche (Spain) 281 + + 79. The Eclipse of May 28, 1900, as photographed by + King Alfonso XIII, at Madrid 285 + + 80. Measurement of Angles 289 + + 81. Division of the Circumference into 360 degrees 291 + + 82. Measurement of the distance of the Moon 292 + + 83. Measurement of the distance of the Sun 297 + + 84. Small apparent ellipses described by the stars as a + result of the annual displacement of the Earth 306 + + + + +INTRODUCTION + + +The Science of Astronomy is sublime and beautiful. Noble, elevating, +consoling, divine, it gives us wings, and bears us through Infinitude. +In these ethereal regions all is pure, luminous, and splendid. Dreams of +the Ideal, even of the Inaccessible, weave their subtle spells upon us. +The imagination soars aloft, and aspires to the sources of Eternal +Beauty. + +What greater delight can be conceived, on a fine spring evening, at the +hour when the crescent moon is shining in the West amid the last glimmer +of twilight, than the contemplation of that grand and silent spectacle +of the stars stepping forth in sequence in the vast Heavens? All sounds +of life die out upon the earth, the last notes of the sleepy birds have +sunk away, the Angelus of the church hard by has rung the close of day. +But if life is arrested around us, we may seek it in the Heavens. These +incandescing orbs are so many points of interrogation suspended above +our heads in the inaccessible depths of space.... Gradually they +multiply. There is Venus, the white star of the shepherd. There Mars, +the little celestial world so near our own. There the giant Jupiter. +The seven stars of the Great Bear seem to point out the pole, while they +slowly revolve around it.... What is this nebulous light that blanches +the darkness of the heavens, and traverses the constellations like a +celestial path? It is the Galaxy, the Milky Way, composed of millions on +millions of suns!... The darkness is profound, the abyss immense.... +See! Yonder a shooting star glides silently across the sky, and +disappears!... + +Who can remain insensible to this magic spectacle of the starry Heavens? +Where is the mind that is not attracted to these enigmas? The +intelligence of the amateur, the feminine, no less than the more +material and prosaic masculine mind, is well adapted to the +consideration of astronomical problems. Women, indeed, are naturally +predisposed to these contemplative studies. And the part they are called +to play in the education of our children is so vast, and so important, +that the elements of Astronomy might well be taught by the young mother +herself to the budding minds that are curious about every issue--whose +first impressions are so keen and so enduring. + +Throughout the ages women have occupied themselves successfully with +Astronomy, not merely in its contemplative and descriptive, but also in +its mathematical aspects. Of such, the most illustrious was the +beautiful and learned Hypatia of Alexandria, born in the year 375 of our +era, public lecturer on geometry, algebra, and astronomy, and author of +three works of great importance. Then, in that age of ignorance and +fanaticism, she fell a victim to human stupidity and malice, was dragged +from her chariot while crossing the Cathedral Square, in March, 415, +stripped of her garments, stoned to death, and burned as a dishonored +witch! + +Among the women inspired with a passion for the Heavens may be cited St. +Catherine of Alexandria, admired for her learning, her beauty and her +virtue. She was martyred in the reign of Maximinus Daza, about the year +312, and has given her name to one of the lunar rings. + +Another celebrated female mathematician was Madame Hortense Lepaute, +born in 1723, who collaborated with Clairaut in the immense calculations +by which he predicted the return of Halley's Comet. "Madame Lepaute," +wrote Lalande, "gave us such immense assistance that, without her, we +should never have ventured to undertake this enormous labor, in which it +was necessary to calculate for every degree, and for a hundred and fifty +years, the distances and forces of the planets acting by their +attraction on the comet. During more than six months, we calculated from +morning to night, sometimes even at table, and as the result of this +forced labor I contracted an illness that has changed my constitution +for life; but it was important to publish the result before the arrival +of the comet." + +This extract will suffice for the appreciation of the scientific ardor +of Madame Lepaute. We are indebted to her for some considerable works. +Her husband was clock-maker to the King. "To her intellectual talents," +says one of her biographers, "were joined all the qualities of the +heart. She was charming to a degree, with an elegant figure, a dainty +foot, and such a beautiful hand that Voiriot, the King's painter, who +had made a portrait of her, asked permission to copy it, in order to +preserve a model of the best in Nature." And then we are told that +learned women can not be good-looking!... + +The Marquise du Châtelet was no less renowned. She was predestined to +her career, if the following anecdote be credible. Gabrielle-Émilie de +Breteuil, born in 1706 (who, in 1725, was to marry the Marquis du +Châtelet, becoming, in 1733, the most celebrated friend of Voltaire), +was four or five years old when she was given an old compass, dressed up +as a doll, for a plaything. After examining this object for some time, +the child began angrily and impatiently to strip off the silly draperies +the toy was wrapped in, and after turning it over several times in her +little hands, she divined its uses, and traced a circle with it on a +sheet of paper. To her, among other things, we owe a precious, and +indeed the only French, translation of Newton's great work on universal +gravitation, the famous Principia, and she was, with Voltaire, an +eloquent propagator of the theory of attraction, rejected at that time +by the Académie des Sciences. + +Numbers of other women astronomers might be cited, all showing how +accessible this highly abstract science is to the feminine intellect. +President des Brosses, in his charming Voyage en Italie, tells of the +visit he paid in Milan to the young Italian, Marie Agnesi, who delivered +harangues in Latin, and was acquainted with seven languages, and for +whom mathematics held no secrets. She was devoted to algebra and +geometry, which, she said, "are the only provinces of thought wherein +peace reigns." Madame de Charrière expressed herself in an aphorism of +the same order: "An hour or two of mathematics sets my mind at liberty, +and puts me in good spirits; I feel that I can eat and sleep better when +I have seen obvious and indisputable truths. This consoles me for the +obscurities of religion and metaphysics, or rather makes me forget them; +I am thankful there is something positive in this world." And did not +Madame de Blocqueville, last surviving daughter of Marshal Davout, who +died in 1892, exclaim in her turn: "Astronomy, science of sciences! by +which I am attracted, and terrified, and which I adore! By it my soul is +detached from the things of this world, for it draws me to those unknown +spheres that evoked from Newton the triumphant cry: '_Coeli enarrant +gloriam Dei!_'" + +Nor must we omit Miss Caroline Herschel, sister of the greatest observer +of the Heavens, the grandest discoverer of the stars, that has ever +lived. Astronomy gave her a long career; she discovered no less than +seven comets herself, and her patient labors preserved her to the age of +ninety-eight.--And Mrs. Somerville, to whom we owe the English +translation of Laplace's Mécanique céleste, of whom Humboldt said, "In +pure mathematics, Mrs. Somerville is absolutely superior." Like Caroline +Herschel, she was almost a centenarian, appearing always much younger +than her years: she died at Naples, in 1872, at the age of +ninety-two.--So, too, the Russian Sophie Kovalevsky, descendant of +Mathias Corvinus, King of Hungary, who, an accomplished mathematician at +sixteen, married at eighteen, in order to follow the curriculum at the +University (then forbidden to unmarried women); arranging with her young +husband to live as brother and sister until their studies should be +completed. In 1888 the Prix Bordin of the Institut was conferred on +her.--And Maria Mitchell of the United States, for whom Le Verrier gave +a _fête_ at the Observatory of Paris, and who was exceptionally +authorized by Pope Pius IX to visit the Observatory of the Roman +College, at that time an ecclesiastical establishment, closed to +women.--And Madame Scarpellini, the Roman astronomer, renowned for her +works on shooting stars, whom the author had the honor of visiting, in +company with Father Secchi, Director of the Observatory mentioned above. + +At the present time, Astronomy is proud to reckon among its most famous +workers Miss Agnes Clerke, the learned Irishwoman, to whom we owe, +_inter alia_, an excellent History of Astronomy in the Nineteenth +Century;--Mrs. Isaac Roberts, who, under the familiar name of Miss +Klumpke, sat on the Council of the Astronomical Society of France, and +is D. Sc. of the Faculty of Paris and head of the Bureau for measuring +star photographs at the Observatory of Paris (an American who became +English by her marriage with the astronomer Roberts, but is not +forgotten in France);--Mrs. Fleming, one of the astronomers of the +Observatory at Harvard College, U.S.A., to whom we owe the discovery of +a great number of variable stars by the examination of photographic +records, and by spectral photography;--Lady Huggins, who in England is +the learned collaborator of her illustrious husband;--and many others. + + * * * * * + +The following chapters, which aim at summing up the essentials of +Astronomy in twelve lessons for amateurs, will not make astronomers or +mathematicians of my readers--much less prigs or pedants. They are +designed to show the constitution of the Universe, in its grandeur and +its beauty, so that, inhabiting this world, we may know where we are +living, may realize our position in the Cosmos, appreciate Creation as +it is, and enjoy it to better advantage. This sun by which we live, this +succession of months and years, of days and nights, the apparent motions +of the heavens, these starry skies, the divine rays of the moon, the +whole totality of things, constitutes in some sort the tissue of our +existence, and it is indeed extraordinary that the inhabitants of our +planet should almost all have lived till now without knowing where they +are, without suspecting the marvels of the Universe. + + * * * * * + +For the rest, my little book is dedicated to a woman, muse and +goddess--the charming enchantress Urania, fit companion of Venus, +ranking even above her in the choir of celestial beauties, as purer and +more noble, dominating with her clear glance the immensities of the +universe. Urania, be it noted, is feminine, and never would the poetry +of the ancients have imagined a masculine symbol to personify the +pageant of the heavens. Not Uranus, nor Saturn, nor Jupiter can compare +with the ideal beauty of Urania. + +Moreover, I have before me two delightful books, in breviary binding, +dated the one from the year 1686, the other from a century later, 1786. +The first was written by Fontenelle for a Marquise, and is entitled +Entretiens sur la Pluralité des Mondes. In this, banter is pleasantly +married with science, the author declaring that he only demands from his +fair readers the amount of application they would concede to a novel. +The second is written by Lalande, and is called Astronomie des Dames. In +addressing myself to both sexes, I am in honorable company with these +two sponsors and esteem myself the better for it. + + + + +CHAPTER I + +THE CONTEMPLATION OF THE HEAVENS + + +The crimson disk of the Sun has plunged beneath the Ocean. The sea has +decked itself with the burning colors of the orb, reflected from the +Heavens in a mirror of turquoise and emerald. The rolling waves are gold +and silver, and break noisily on a shore already darkened by the +disappearance of the celestial luminary. + +We gaze regretfully after the star of day, that poured its cheerful rays +anon so generously over many who were intoxicated with gaiety and +happiness. We dream, contemplating the magnificent spectacle, and in +dreaming forget the moments that are rapidly flying by. Yet the darkness +gradually increases, and twilight gives way to night. + +The most indifferent spectator of the setting Sun as it descends beneath +the waves at the far horizon, could hardly be unmoved by the pageant of +Nature at such an impressive moment. + +The light of the Crescent Moon, like some fairy boat suspended in the +sky, is bright enough to cast changing and dancing sparkles of silver +upon the ocean. The Evening Star declines slowly in its turn toward the +western horizon. Our gaze is held by a shining world that dominates the +whole of the occidental heavens. This is the "Shepherd's Star," Venus of +rays translucent. + +Little by little, one by one, the more brilliant stars shine out. Here +are the white Vega of the Lyre, the burning Arcturus, the seven stars of +the Great Bear, a whole sidereal population catching fire, like +innumerable eyes that open on the Infinite. It is a new life that is +revealed to our imagination, inviting us to soar into these mysterious +regions. + +O Night, diapered with fires innumerable! hast thou not written in +flaming letters on these Constellations the syllables of the great +enigma of Eternity? The contemplation of thee is a wonder and a charm. +How rapidly canst thou efface the regrets we suffered on the departure +of our beloved Sun! What wealth, what beauty hast thou not reserved for +our enraptured souls! Where is the man that can remain blind to such a +pageant and deaf to its language! + +To whatever quarter of the Heavens we look, the splendors of the night +are revealed to our astonished gaze. These celestial eyes seem in their +turn to gaze at, and to question us. Thus indeed have they questioned +every thinking soul, so long as Humanity has existed on our Earth. Homer +saw and sung these self-same stars. They shone upon the slow succession +of civilizations that have disappeared, from Egypt of the period of the +Pyramids, Greece at the time of the Trojan War, Rome and Carthage, +Constantine and Charlemagne, down to the Twentieth Century. The +generations are buried with the dust of their ancient temples. The Stars +are still there, symbols of Eternity. + +The silence of the vast and starry Heavens may terrify us; its immensity +may seem to overwhelm us. But our inquiring thought flies curiously on +the wings of dream, toward the remotest regions of the visible. It rests +on one star and another, like the butterfly on the flower. It seeks what +will best respond to its aspirations: and thus a kind of communication +is established, and, as it were, protected by all Nature in these silent +appeals. Our sense of solitude has disappeared. We feel that, if only as +infinitesimal atoms, we form part of that immense universe, and this +dumb language of the starry night is more eloquent than any speech. Each +star becomes a friend, a discreet confidant, often indeed a precious +counsellor, for all the thoughts it suggests to us are pure and holy. + +Is any poem finer than the book written in letters of fire upon the +tablets of the firmament? Nothing could be more ideal. And yet, the +poetic sentiment that the beauty of Heaven awakens in our soul ought +not to veil its reality from us. That is no less marvelous than the +mystery by which we were enchanted. + +And here we may ask ourselves how many there are, even among thinking +human beings, who ever raise their eyes to the starry heavens? How many +men and women are sincerely, and with unfeigned curiosity, interested in +these shining specks, and inaccessible luminaries, and really desirous +of a better acquaintance with them? + +Seek, talk, ask in the intercourse of daily life. You, who read these +pages, who already love the Heavens, and comprehend them, who desire to +account for our existence in this world, who seek to know what the Earth +is, and what Heaven--you shall witness that the number of those +inquiring after truth is so limited that no one dares to speak of it, so +disgraceful is it to the so-called intelligence of our race. And yet! +the great Book of the Heavens is open to all eyes. What pleasures await +us in the study of the Universe! Nothing could speak more eloquently to +our heart and intellect! + +Astronomy is the science _par excellence_. It is the most beautiful and +most ancient of all, inasmuch as it dates back to the indeterminate +times of highest antiquity. Its mission is not only to make us +acquainted with the innumerable orbs by which our nights are +illuminated, but it is, moreover, thanks to it that we know where and +what we are. Without it we should live as the blind, in eternal +ignorance of the very conditions of our terrestrial existence. Without +it we should still be penetrated with the naïve error that reduced the +entire Universe to our minute globule, making our Humanity the goal of +the Creation, and should have no exact notion of the immense reality. + +To-day, thanks to the intellectual labor of so many centuries, thanks +also to the immortal genius of the men of science who have devoted their +lives to searching after Truth--men such as Copernicus, Galileo, Kepler, +Newton--the veil of ignorance has been rent, and glimpses of the marvels +of creation are perceptible in their splendid truth to the dazzled eye +of the thinker. + +The study of Astronomy is not, as many suppose, the sacrifice of oneself +in a cerebral torture that obliterates all the beauty, the fascination, +and the grandeur of the pageant of Nature. Figures, and naught but +figures, would not be entertaining, even to those most desirous of +instruction. Let the reader take courage! We do not propose that he +shall decipher the hieroglyphics of algebra and geometry. Perish the +thought! For the rest, figures are but the scaffolding, the method, and +do not exist in Nature. + +[Illustration: FIG. 1.--The great Book of the Heavens is open to all +eyes.] + +We simply beg of you to open your eyes, to see where you are, so that +you may not stray from the path of truth, which is also the path of +happiness. Once you have entered upon it, no persuasion will be needed +to make you persevere. And you will have the profound satisfaction of +knowing that you are thinking correctly, and that it is infinitely +better to be educated than to be ignorant. The reality is far beyond all +dreams, beyond the most fantastic imagination. The most fairy-like +transformations of our theaters, the most resplendent pageants of our +military reviews, the most sumptuous marvels on which the human race can +pride itself--all that we admire, all that we envy on the Earth--is as +nothing compared with the unheard-of wonders scattered through +Infinitude. There are so many that one does not know how to see them. +The fascinated eye would fain grasp all at once. + +If you will yield yourselves to the pleasure of gazing upon the +sparkling fires of Space, you will never regret the moments passed all +too rapidly in the contemplation of the Heavens. + +Diamonds, turquoises, rubies, emeralds, all the precious stones with +which women love to deck themselves, are to be found in greater +perfection, more beautiful, and more splendid, set in the immensity of +Heaven! In the telescopic field, we may watch the progress of armies of +majestic and powerful suns, from whose attacks there is naught to fear. +And these vagabond comets and shooting stars and stellar nebulæ, do they +not make up a prodigious panorama? What are our romances in comparison +with the History of Nature? Soaring toward the Infinite, we purify our +souls from all the baseness of this world, we strive to become better +and more intelligent. + + * * * * * + +But in the first place, you ask, what are the Heavens? This vault +oppresses us. We can not venture to investigate it. + +Heaven, we reply, is no vault, it is a limitless immensity, +inconceivable, unfathomable, that surrounds us on all sides, and in the +midst of which our globe is floating. THE HEAVENS ARE ALL THAT EXISTS, +all that we see, and all that we do not see: the Earth on which we are, +that bears us onward in her rapid flight; the Moon that accompanies us, +and sheds her soft beams upon our silent nights; the good Sun to which +we owe our existence; the Stars, suns of Infinitude; in a word--the +whole of Creation. + +Yes, our Earth is an orb of the Heavens: the sky is her domain, and our +Sun, shining above our heads, and fertilizing our seasons, is as much a +star as the pretty sparkling points that scintillate up there, in the +far distance, and embellish the calm of our nights with their +brilliancy. All are in the Heavens, you as well as I, for the Earth, in +her course through Space, bears us with herself into the depths of +Infinitude. + +In the Heavens there is neither "above" nor "below." These words do not +exist in celestial speech, because their significance is relative to the +surface of this planet only. In reality, for the inhabitants of the +Earth, "low" is the inside, the center of the globe, and "high" is what +is above our heads, all round the Earth. The Heavens are what surround +us on all sides, to Infinity. + +The Earth is, like her fellows, Mercury, Venus, Mars, Jupiter, Saturn, +Uranus, Neptune, one of the planets of the great solar family. + +The Sun, her father, protects her, and directs all her actions. She, as +the grateful daughter, obeys him blindly. All float in perfect harmony +over the celestial ocean. + +But, you may say, on what does the Earth rest in her ethereal +navigation? + +On nothing. The Earth turns round the colossal Sun, a little globe of +relatively light weight, isolated on all sides in Space, like a +soap-bubble blown by some careless child. + +Above, below, on all sides, millions of similar globes are grouped into +families, and form other systems of worlds revolving round the numerous +and distant stars that people Infinitude; suns more or less analogous to +that by which we are illuminated, and generally speaking of larger bulk, +although our Sun is a million times larger than our planet. + +Among the ancients, before the isolation of our globe in Space and the +motions that incessantly alter its position were recognized, the Earth +was supposed to be the immobile lower half of the Universe. The sky was +regarded as the upper half. The ancients supplied our world with +fantastic supports that penetrated to the Infernal Regions. They could +not admit the notion of the Earth's isolation, because they had a false +idea of its weight. To-day, however, we know positively that the Earth +is based on nothing. The innumerable journeys accomplished round it in +all directions give definite proof of this. It is attached to nothing. +As we said before, there is neither "above" nor "below" in the Universe. +What we call "below" is the center of the Earth. For the rest the Earth +turns upon its own axis in twenty-four hours. Night is only a partial +phenomenon, due to the rotary motion of the planet, a motion that could +not exist under conditions other than that of the absolute isolation of +our globe in space. + +[Illustration: FIG. 2.--The earth in space. June solstice, midday.] + +Since the Sun can only illuminate one side of our globe at one moment, +that is to say one hemisphere, it follows that Night is nothing but the +state of the part that is not illuminated. As the Earth revolves upon +itself, all the parts successively exposed to the Sun are in the day, +while the parts situated opposite to the Sun, in the cone of shadow +produced by the Earth itself, are in night. But whether it be noon or +midnight, the stars always occupy the same position in the Heavens, +even when, dazzled by the ardent light of the orb of day, we can no +longer see them; and when we are plunged into the darkness of the night, +the god Phoebus still continues to pour his beneficent rays upon the +countries turned toward him. + +The sequence of day and night is a phenomenon belonging, properly +speaking, to the Earth, in which the rest of the Universe does not +participate. The same occurs for every world that is illuminated by a +sun, and endowed with a rotary movement. In absolute space, there is no +succession of nights and days. + +Upheld in space by forces that will be explained at a later point, our +planet glides in the open heavens round our Sun. + +Imagine a magnificent aerostat, lightly and rapidly cleaving space. +Surround it with eight little balloons of different sizes, the smallest +like those sold on the streets for children to play with, the larger, +such as are distributed for a bonus in large stores. Imagine this group +sailing through the air, and you have the system of our worlds in +miniature. + +Still, this is only an image, a comparison. The balloons are held up by +the atmosphere, in which they float at equilibrium. The Earth is +sustained by nothing material. What maintains her in equilibrium is the +ethereal void; an immaterial force; gravitation. The Sun attracts her, +and if she did not revolve, she would drop into him; but rotating round +him, at a speed of 107,000 kilometers[2] (about 66,000 miles) per hour, +she produces a centrifugal force, like that of a stone in a sling, that +is precisely equivalent, and of contrary sign, to its gravitation toward +the central orb, and these two equilibrated forces keep her at the same +medium distance. + +This solar and planetary group does not exist solitary in the immense +void that extends indefinitely around us. As we said above, each star +that we admire in the depths of the sky, and to which we lift up our +eyes and thoughts during the charmed hours of the night, is another sun +burning with its own light, the chief of a more or less numerous family, +such as are multiplied through all space to infinity. Notwithstanding +the immense distances between the sun-stars, Space is so vast, and the +number of these so great, that by an effect of perspective due solely to +the distance, appearances would lead us to believe that the stars were +touching. And under certain telescopic aspects, and in some of the +astral photographs, they really do appear to be contiguous. + +The Universe is infinite. Space is limitless. If our love for the +Heavens should incite in us the impulse, and provide us with the means +of undertaking a journey directed to the ends of Heaven as its goal, we +should be astonished, on arriving at the confines of the Milky Way, to +see the grandiose and phenomenal spectacle of a new Universe unfold +before our dazzled eyes; and if in our mad career we crossed this new +archipelago of worlds to seek the barriers of Heaven beyond them, we +should still find universe eternally succeeding to universe before us. +Millions of suns roll on in the immensities of Space. Everywhere, on all +sides, Creation renews itself in an infinite variety. + +According to all the probabilities, universal life is distributed there +as well as here, and has sown the germ of intelligence upon those +distant worlds that we divine in the vicinity of the innumerable suns +that plow the ether, for everything upon the Earth tends to show that +Life is the goal of Nature. Burning foci, inextinguishable sources of +warmth and light, these various, multi-colored suns shed their rays upon +the worlds that belong to them and which they fertilize. + +Our globe is no exception in the Universe. As we have seen, it is one of +the celestial orbs, nourished, warmed, lighted, quickened by the Sun, +which in its turn again is but a star. + +Innumerable Worlds! We dream of them. Who can say that their unknown +inhabitants do not think of us in their turn, and that Space may not be +traversed by waves of thought, as it is by the vibrations of light and +universal gravitation? May not an immense solidarity, hardly guessed at +by our imperfect senses, exist between the Celestial Humanities, our +Earth being only a modest planet. + +Let us meditate on this Infinity! Let us lose no opportunity of +employing the best of our hours, those of the silence and peace of the +bewitching nights, in contemplating, admiring, spelling out the words of +the Great Book of the Heavens. Let our freed souls fly swift and rapt +toward those marvelous countries where indescribable joys are prepared +for us, and let us do homage to the first and most splendid of the +sciences, to Astronomy, which diffuses the light of Truth within us. + +To poetical souls, the contemplation of the Heavens carries thought away +to higher regions than it attains in any other meditation. Who does not +remember the beautiful lines of Victor Hugo in the Orientales? Who has +not heard or read them? The poem is called "Ecstasy," and it is a +fitting title. The words are sometimes set to music, and the melody +seems to complete their pure beauty: + + J'étais seul près des flots par une nuit d'étoiles. + Pas un nuage aux cieux, sur les mers pas de voiles; + Mes yeux plongeaient plus loin que le monde réel, + Et les bois et les monts et toute la nature + Semblaient interroger, dans un confus murmure, + Les flots des mers, les feux du ciel. + + Et les étoiles d'or, légions infinies, + A voix haute, à voix basse, avec mille harmonies + Disaient, en inclinant leurs couronnes de feu; + Et les flots bleus, que rien ne gouverne et n'arrête, + Disaient en recourbant l'écume de leur crête: + ... C'est le Seigneur, le Seigneur Dieu! + +_Note: Free Translation_ + + I was alone on the waves, on a starry night, + Not a cloud in the sky, not a sail in sight, + My eyes pierced beyond the natural world... + And the woods, and the hills, and the voice of Nature + Seemed to question in a confused murmur, + The waves of the Sea, and Heaven's fires. + + And the golden stars in infinite legion, + Sang loudly, and softly, in glad recognition, + Inclining their crowns of fire;... + And the waves that naught can check nor arrest + Sang, bowing the foam of their haughty crest... + Behold the Lord God--Jehovah! + +The immortal poet of France was an astronomer. The author more than +once had the honor of conversing with him on the problems of the starry +sky--and reflected that astronomers might well be poets. + +It is indeed difficult to resist a sense of profound emotion before the +abysses of infinite Space, when we behold the innumerable multitude of +worlds suspended above our heads. We feel in this solitary contemplation +of the Heavens that there is more in the Universe than tangible and +visible matter: that there are forces, laws, destinies. Our ants' brains +may know themselves microscopic, and yet recognize that there is +something greater than the Earth, the Heavens;--more absolute than the +Visible, the Invisible;--beyond the more or less vulgar affairs of life, +the sense of the True, the Good, the Beautiful. We feel that an immense +mystery broods over Nature,--over Being, over created things. And it is +here again that Astronomy surpasses all the other sciences, that it +becomes our sovereign teacher, that it is the _pharos_ of modern +philosophy. + +O Night, mysterious, sublime, and infinite! withdrawing from our eyes +the veil spread above us by the light of day, giving back transparency +to the Heavens, showing us the prodigious reality, the shining casket of +the celestial diamonds, the innumerable stars that succeed each other +interminably in immeasurable space! Without Night we should know +nothing. Without it our eyes would never have divined the sidereal +population, our intellects would never have pierced the harmony of the +Heavens, and we should have remained the blind, deaf parasites of a +world isolated from the rest of the universe. O Sacred Night! If on the +one hand it rests upon the heights of Truth beyond the day's illusions, +on the other its invisible urns pour down a silent and tranquil peace, a +penetrating calm, upon our souls that weary of Life's fever. It makes us +forget the struggles, perfidies, intrigues, the miseries of the hours of +toil and noisy activity, all the conventionalities of civilization. Its +domain is that of rest and dreams. We love it for its peace and calm +tranquillity. We love it because it is true. We love it because it +places us in communication with the other worlds, because it gives us +the presage of Life, Universal and Eternal, because it brings us Hope, +because it proclaims us citizens of Heaven. + + + + +CHAPTER II + +THE CONSTELLATIONS + + +In Chapter I we saw the Earth hanging in space, like a globe isolated on +all sides, and surrounded at vast distances by a multitude of stars. + +These fiery orbs are suns like that which illuminates ourselves. They +shine by their own light. We know this for a fact, because they are so +far off that they could neither be illuminated by the Sun, nor, still +more, reflect his rays back upon us: and because, on the other hand, we +have been able to measure and analyze their light. Many of these distant +suns are simple and isolated; others are double, triple, or multiple; +others appear to be the centers of systems analogous to that which +gravitates round our own Sun, and of which we form part. But these +celestial tribes are situated at such remote distances from us that it +is impossible to distinguish all the individuals of each particular +family. The most delicate observations have only revealed a few of them. +We must content ourselves here with admiring the principals,--the +sun-stars,--prodigious globes, flaming torches, scattered profusely +through the firmament. + +How, then, is one to distinguish them? How can they be readily found and +named? There are so many of them! + +Do not fear; it is quite a simple matter. In studying the surface of the +Earth we make use of geographical maps on which the continents and seas +of which it consists are drawn with the utmost care. Each country of our +planet is subdivided into states, each of which has its proper name. We +shall pursue the same plan in regard to the Heavens, and it will be all +the easier since the Great Book of the Firmament is constantly open to +our gaze. Our globe, moreover, actually revolves upon itself so that we +read the whole in due sequence. Given a clear atmosphere, and a little +stimulus to the will from our love of truth and science, and the +geography of the Heavens, or "uranography," will soon be as familiar to +us as the geography of our terrestrial atom. + +On a beautiful summer's night, when we look toward the starry sky, we +are at first aware only of a number of shining specks. The stars seem to +be scattered almost accidentally through Space; they are so numerous and +so close to one another that it would appear rash to attempt to name +them separately. Yet some of the brighter ones particularly attract and +excite our attention. After a little observation we notice a certain +regularity in the arrangement of these distant suns, and take pleasure +in drawing imaginary figures round the celestial groups. + +That is what the ancients did from a practical point of view. In order +to guide themselves across the trackless ocean, the earliest Phenician +navigators noted certain fixed bearings in the sky, by which they mapped +out their routes. In this way they discovered the position of the +immovable Pole, and acquired empire over the sea. The Chaldean pastors, +too, the nomad people of the East, invoked the Heavens to assist in +their migrations. They grouped the more brilliant of the stars into +Constellations with simple outlines, and gave to each of these celestial +provinces a name derived from mythology, history, or from the natural +kingdoms. It is impossible to determine the exact epoch of this +primitive celestial geography. The Centaur Chiron, Jason's tutor, was +reputed the first to divide the Heavens upon the sphere of the +Argonauts. But this origin is a little mythical! In the Bible we have +the Prophet Job, who names Orion, the Pleiades, and the Hyades, 3,300 +years ago. The Babylonian Tables, and the hieroglyphs of Egypt, witness +to an astronomy that had made considerable advance even in those remote +epochs. Our actual constellations, which are doubtless of Babylonian +origin, appear to have been arranged in their present form by the +learned philosopher Eudoxus of Cnidus, about the year 360 B.C. Aratus +sang of them in a didactic poem toward 270. Hipparchus of Rhodes was the +first to note the astronomical positions with any precision, one hundred +and thirty years before our era. He classified the stars in order of +magnitude, according to their apparent brightness; and his catalogue, +preserved in the Almagest of Ptolemy, contains 1,122 stars distributed +into forty-eight Constellations. + +The figures of the constellations, taken almost entirely from fable, are +visible only to the eyes of the imagination, and where the ancients +placed such and such a person or animal, we may see, with a little +good-will, anything we choose to fancy. There is nothing real about +these figures. And yet it is indispensable to be able to recognize the +constellations in order to find our way among the innumerable army of +the stars, and we shall commence this study with the description of the +most popular and best known of them all, the one that circles every +night through our Northern Heavens. Needless to name it; it is familiar +to every one. You have already exclaimed--the Great Bear! + +This vast and splendid association of suns, which is also known as the +Chariot of David, the Plow or Charles's Wain, and the Dipper, is one of +the finest constellations in the Heavens, and one of the oldest--seeing +that the Chinese hailed it as the divinity of the North, over three +thousand years ago. + +If any of my readers should happen to forget its position in the sky, +the following is a very simple expedient for finding it. Turn to the +North--that is, opposite to the point where the sun is to be found at +midday. Whatever the season of the year, day of the month, or hour of +the night, you will always see, high up in the firmament, seven +magnificent stars, arranged in a quadrilateral, followed by a tail, or +handle, of three stars. This magnificent constellation never sinks below +our horizon. Night and day it watches above us, turning in twenty-four +hours round a very famous star that we shall shortly become acquainted +with. In the figure of the Great Bear, the four stars of the +quadrilateral are found in the body, and the three at the extremity make +the tail. As David's Chariot, the four stars represent the wheels, and +the three others the horses. + +Sometimes our ancestors called them the Seven Oxen, the "oxen of the +celestial pastures," from which the word septentrion (_septem triones_, +seven oxen of labor) is derived. Some see a Plowshare; others more +familiarly call this figure the Dipper. As it rotates round the pole, +its outline varies with the different positions. + +It is not easy to guess why this constellation should have been called +the Bear. Yet the name has had a certain influence. From the Greek word +_arctos_ (bear) has come arctic, and for its antithesis, antarctic. From +the Latin word _trio_ (ox of labor) has come septentrion, the seven +oxen. Etymology is not always logical. Is not the word "venerate" +derived from Venus? + +In order to distinguish one star from another, the convention of +denoting them by the letters of the Greek Alphabet has been adopted, for +it would be impossible to give a name to each, so considerable is their +number.[3] + +[alpha] and [beta] denote the front wheels of the Chariot generally +known as the "pointers;" [gamma] and [delta] the hind wheels; [epsilon], +[zeta], [eta] the three horses. All these stars are of the second order +of magnitude (the specific meaning of this expression will be explained +in the next chapter), except the last ([delta]) of the quadrilateral, +which is of the third order. + +[Illustration: FIG. 3.--The Great Bear (or Dipper), and the Pole-Star.] + +Figure 3 gives the outline of this primitive constellation. In revolving +in twenty-four hours round the Pole, which is situated at the +prolongation of a line drawn from [beta] to [alpha], it occupies every +conceivable position,--as if this page were turned in all directions. +But the relative arrangement of the seven stars remains unaltered. In +contemplating these seven stars it must never be forgotten that each is +a dazzling sun, a center of force and life. One of them is especially +remarkable: [zeta], known as Mizar to the Arabs. Those who have good +sight will distinguish near it a minute star, Alcor, or the Cavalier, +also called Saidak by the Arabs--that is, the Test, because it can be +used as a test of vision. But further, if you have a small telescope at +your disposal, direct it upon the fine star Mizar: you will be +astonished at discovering two of the finest diamonds you could wish to +see, with which no brilliant is comparable. There are several double +stars; these we shall become acquainted with later on. + +Meantime, we must not forget our celestial geography. The Great Bear +will help us to find all the adjacent constellations. + +[Illustration: FIG. 4.--To find the Pole-Star.] + +If a straight line is drawn (Fig. 4) from [beta] through [alpha], which +forms the extremity of the square, and is prolonged by a quantity equal +to the distance of [alpha] from the tip of the handle, we come on a star +of second magnitude, which marks the extremity of a figure perfectly +comparable with the Great Bear, but smaller, less brilliant, and +pointing in the contrary direction. This is the Little Bear, composed, +like its big brother, of seven stars; the one situated at the end of the +line by which we have found it is the Pole-Star. + +Immovable in the region of the North Pole, the Pole-Star has captivated +all eyes by its position in the firmament. It is the providence of +mariners who have gone astray on the ocean, for it points them to the +North, while it is the pivot of the immense rotation accomplished round +it by all the stars in twenty-four hours. Hence it is a very important +factor, and we must hasten to find it, and render it due homage. It +should be added that its special immobility, in the prolongation of the +Earth's axis, is merely an effect caused by the diurnal movements of our +planet. Our readers are of course aware that it is the earth that turns +and not the sky. But evidence of this will be given later on. In looking +at the Pole-Star, the South is behind one, the East to the right, and +the West to the left. + +Between the Great and the Little Bear, we can distinguish a winding +procession of smaller stars. These constitute the Dragon. + +We will continue our journey by way of Cassiopeia, a fine constellation +placed on the opposite side of the Pole-Star in relation to the Great +Bear, and shaped somewhat like the open limbs of the letter W. It is +also called the Chair. And, in fact, when the figure is represented with +the line [alpha] [beta] below, the line [chi] [gamma] forms the seat, +and [gamma] [delta] [epsilon] its back. + +If a straight line is drawn from [delta] of the Great Bear, and +prolonged beyond the Pole-Star in a quantity equal to the distance which +separates these two stars, it is easy to find this constellation (Fig. +5). This group, like the preceding, never sets, and is always visible, +opposite to the Great Bear. It revolves in twenty-four hours round the +Pole-Star, and is to be seen, now above, now below, now to the right, +now to the left. + +[Illustration: FIG. 5.--To find Cassiopeia.] + +[Illustration: FIG. 6.--To Find Pegasus and Andromeda.] + +If in the next place, starting from the stars [alpha] and [delta] in the +Great Bear, we draw two lines which join at Polaris and are prolonged +beyond Cassiopeia, we arrive at the Square of Pegasus (Fig. 6), a vast +constellation that terminates on one side in a prolongation formed of +three stars. + +These three last stars belong to Andromeda, and themselves abut on +Perseus. The last star in the Square of Pegasus is also the first in +Andromeda. + +[gamma] of Andromeda is a magnificent double orb, to which we shall +return in the next chapter, _i.e._, the telescope resolves it into two +marvelous suns, one of which is topaz-yellow, and the other +emerald-green. Three stars, indeed, are visible with more powerful +instruments. + +[Illustration: FIG. 7.--Perseus, the Pleiades, Capella.] + +Above [beta] and near a small star, is visible a faint, whitish, +luminous trail: this is the oblong nebula of Andromeda, the first +mentioned in the history of astronomy, and one of the most beautiful in +the Heavens, perceptible to the unaided eye on very clear nights. + +The stars [alpha], [beta] and [gamma] of Perseus form a concave bow +which will serve in a new orientation. If it is prolonged in the +direction of [delta], we find a very brilliant star of the first +magnitude. This is Capella, the Goat, in the constellation of the +Charioteer (Fig. 7). + +If coming back to [delta] in Perseus, a line is drawn toward the South, +we reach the Pleiades, a gorgeous cluster of stars, scintillating like +the finest dust of diamonds, on the shoulder of the Bull, to which we +shall come shortly, in studying the Constellations of the Zodiac. + +Not far off is a very curious star, [beta] of Perseus, or Algol, which +forms a little triangle with two others smaller than itself. This star +is peculiar in that, instead of shining with a fixed light, it varies in +intensity, and is sometimes pale, sometimes brilliant. It belongs to the +category of variable stars which we shall study later on. All the +observations made on it for more than two hundred years go to prove that +a dark star revolves round this sun, almost in the plane of our line of +sight, producing as it passes in front of it a partial eclipse that +reduces it from the second to the fourth magnitude, every other two +days, twenty hours, and forty-nine minutes. + +And now, let us return to the Great Bear, which aided us so beneficently +to start for these distant shores, and whence we shall set out afresh in +search of other constellations. + +If we produce the curved line of the tail, or handle, we encounter a +magnificent golden-yellow star, a splendid sun of dazzling brilliancy: +let us make our bow to Arcturus, [alpha] of the Herdsman, which is at +the extremity of this pentagonal constellation. The principal stars of +this asterism are of the third magnitude, with the exception of [alpha], +which is of the first. Alongside of the Herdsman is a circle consisting +of five stars of the third and fourth magnitude, save the third, +[alpha], or the Pearl, which is of the second magnitude. This is the +Corona Borealis. It is very easily recognized (Fig. 8). + +[Illustration: FIG. 8.--To find Arcturus, the Herdsman, and the Northern +Crown.] + +A line drawn from the Pole-Star to Arcturus forms the base of an +equilateral triangle, the apex of which, situated opposite the Great +Bear, is occupied by Vega, or [alpha] of the Lyre, a splendid diamond of +ideal purity scintillating through the ether. This magnificent star, of +first magnitude, is, with Arcturus, the most luminous in our Heavens. It +burns with a white light, in the proximity of the Milky Way, not far +from a constellation that is very easily recognized by the arrangement +of its principal stars in the form of a cross. It is named Cygnus, the +Bird, or the Swan (Fig. 9), and is easy to find by the Square of +Pegasus, and the Milky Way. This figure, the brilliancy of whose +constituents (of the third and fourth magnitudes) contrasts strongly +with the pallor of the Milky Way, includes at its extremity at the foot +of the Cross, a superb double star, [beta] or Albirio: [alpha] of Cygnus +is also called Deneb. The first star of which the distance was +calculated is in this constellation. This little orb of fifth magnitude, +which hangs 69,000,000,000,000 kilometers (42,000,000,000,000 miles) +above our Earth, is the nearest of all the stars to the skies of Europe. + +[Illustration: FIG. 9.--The Swan, Vega, the Eagle.] + +Not far off is the fine Eagle, which spreads its wings in the Milky Way, +and in which the star Altaïr, [alpha], of first magnitude, is situated +between its two satellites, [beta] and [gamma]. + +The Constellation of Hercules, toward which the motions of the Sun are +impelling us, with all the planets of its system, is near the Lyre. Its +principal stars can be recognized inside the triangle formed by the +Pole-Star, Arcturus, and Vega. + +All the Constellations described above belong to the Northern +Hemisphere. Those nearest the pole are called circumpolar. They revolve +round the pole in twenty-four hours. + +Having now learned the Northern Heavens, we must come back to the Sun, +which we have left behind us. The Earth revolves round him in a year, +and in consequence he seems to revolve round us, sweeping through a vast +circle of the celestial sphere. In each year, at the same period, he +passes the same points of the Heavens, in front of the same +constellations, which are rendered invisible by his light. We know that +the stars are at a fixed position from the Earth, whatever their +distance, and that if we do not see them at noon as at midnight, it is +simply because they are extinguished by the dazzling light of the orb of +day. With the aid of a telescope it is always possible to see the more +brilliant of them. + +The Zodiac is the zone of stars traversed by the Sun in the course of a +year. This word is derived from the Greek _Zodiakos_, which signifies +"animal," and this etymology arose because most of the figures traced +on this belt of stars represent animals. The belt is divided into twelve +parts that are called the twelve Signs of the Zodiac, also named by the +ancients the "Houses of the Sun," since the Sun visits one of them in +each month. These are the signs, with the primitive characters that +distinguish them: the Ram [Aries], the Bull [Taurus], the Twins +[Gemini], the Crab [Cancer], the Lion [Leo], the Virgin [Virgo], the +Balance [Libra], the Scorpion [Scorpio], the Archer [Sagittarius], the +Goat [Capricorn], the Water-Carrier [Aquarius], the Fishes [Pisces]. The +sign [Aries] represents the horns of the Ram, [Taurus] the head of the +Bull, and so on. + +If you will now follow me into the Houses of the Sun you will readily +recognize them again, provided you have a clear picture of the principal +stars of the Northern Heavens. First, you see the Ram, the initial sign +of the Zodiac; because at the epoch at which the actual Zodiac was +fixed, the Sun entered this sign at the vernal equinox, and the equator +crossed the ecliptic at this point. This constellation, in which the +horns of the Ram (third magnitude) are the brightest, is situated +between Andromeda and the Pleiades. Two thousand years ago, the Ram was +regarded as the symbol of spring; but owing to the secular movement of +the precession of the equinoxes, the Sun is no longer there on March 21: +he is in the Fishes. + +To the left, or east of the Ram, we find the Bull, the head of which +forms a triangle in which burns Aldebaran, of first magnitude, a +magnificent red star that marks the right eye; and the Hyades, +scintillating pale and trembling, on its forehead. The timid Pleiades, +as we have seen, veil themselves on the shoulder of the Bull--a +captivating cluster, of which six stars can be counted with the unaided +eye, while several hundred are discovered with the telescope. + +Next the Twins. They are easily recognized by the two fine stars, +[alpha] and [beta], of first magnitude, which mark their heads, and +immortalize Castor and Pollux, the sons of Jupiter, celebrated for their +indissoluble friendship. + +Cancer, the Crab, is the least important sign of the Zodiac. It is +distinguished only by five stars of fourth and fifth magnitudes, +situated below the line of Castor and Pollux, and by a pale cluster +called Præsepe, the Beehive. + +The Lion next approaches, superb in his majesty. At his heart is a +gorgeous star of first magnitude, [alpha] or Regulus. This figure forms +a grand trapezium of four stars on the celestial sphere. + +The Virgin exhibits a splendid star of first magnitude; this is Spica, +which with Regulus and Arcturus, form a triangle by which this +constellation can be recognized. + +The Balance follows the Virgin. Its scales, marked by two stars of +second magnitude, are situated a little to the East of Spica. + +We next come to the eighth constellation of the Zodiac, which is one of +the most beautiful of this belt of stars. Antares, a red star of first +magnitude, occupies the heart of the venomous and accursed Scorpion. It +is situated on the prolongation of a line joining Regulus to Spica, and +forms with Vega of the Lyre, and Arcturus of the Herdsman, a great +isosceles triangle, of which this latter star is the apex. + +The Scorpion, held to be a sign of ill luck, has been prejudicial to the +Archer, which follows it, and traces an oblique trapezium in the sky, a +little to the east of Antares. These two southernmost constellations +never rise much above the horizon for France and England. In fable, the +Archer is Chiron, the preceptor of Jason, Achilles and Æsculapius. + +Capricorn lies to the south of Altaïr, on the prolongation of a line +from the Lyre to the Eagle. It is hardly noticeable save for the stars +[alpha] and [beta] of third magnitude, which scintillate on its +forehead. + +The Water-Carrier pours his streams toward the horizon. He is not rich +in stars, exhibiting only three of third magnitude that form a very +flattened triangle. + +Lastly the Fishes, concluding sign of the Zodiac, are found to the +south of Andromeda and Pegasus. Save for [alpha], of third magnitude, +this constellation consists of small stars that are hardly visible. + +These twelve zodiacal constellations will be recognized on examining the +chart (Figs. 10-11). + +We must now visit the stars of the Southern Heavens, some of which are +equally deserving of admiration. + +[Illustration: FIG. 10.--The Constellations of the Zodiac: summer and +autumn; Capricorn, Archer, Scorpion, Balance, Virgin, Lion.] + +It should in the first place be noted that the signs of the Zodiac and +the Southern Constellations are not, like those which are circumpolar, +perpetually visible at all periods of the year. Their visibility depends +on the time of year and the hour of the night.[4] + +In order to admire the fine constellations of the North, as described +above, we have only to open our windows on a clear summer's evening, or +walk round the garden in the mysterious light of these inaccessible +suns, while we look up at the immense fields in which each star is like +the head of a celestial spear. + +But the summer is over, autumn is upon us, and then, too soon, comes +winter clothed in hoar-frost. The days are short and cold, dark and +dreary; but as a compensation the night is much longer, and adorns +herself with her most beautiful jewels, offering us the contemplation of +her inexhaustible treasures. + +[Illustration: FIG. 11.--The Constellations of the Zodiac: winter and +spring; Crab, Twins, Bull, Ram, Fishes, Water-Carrier.] + +First, let us do homage to the magnificent Orion, most splendid of all +the constellations: he advances like a colossal giant, and confronts the +Bull. + +This constellation appears about midnight in November, in the +south-eastern Heavens; toward eleven o'clock in December and January, +due south; about ten in February, in the south-east; about nine in +March, and about eight in April, in the west; and then sets below our +horizon. + +[Illustration: FIG. 12.--Orion and his celestial companions.] + +It is indisputably the most striking figure in the sky, and with the +Great Bear, the most ancient in history, the first that was noticed: +both are referred to in the ancient texts of China, Chaldea, and Egypt. + +Eight principal stars delineate its outline; two are of the first +magnitude, five of the second, and one of the third (Fig. 12). The most +brilliant are Betelgeuse ([alpha]) and Rigel ([beta]): the former +marking the right shoulder of the Colossus as it faces us; the second +the left foot. The star on the left shoulder is [gamma] or Bellatrix, of +second magnitude; that of the right foot, [chi], is almost of the third. +Three stars of second magnitude placed obliquely at equal distances from +each other, the first or highest of which marks the position of the +equatorial line, indicate the Belt or Girdle. These stars, known as the +Three Kings, and by country people as the Rake, assist greatly in the +recognition of this fine constellation. + +A little below the second star of the Belt, a large white patch, like a +band of fog, the apparent dimensions of which are equal to that of the +lunar disk, is visible to the unaided eye: this is the Nebula of Orion, +one of the most magnificent in the entire Heavens. It was discovered in +1656 by Huyghens, who counted twelve stars in the pale cloud. Since that +date it has been constantly studied and photographed by its many +admirers, while the giant eye of the telescope discovers in it to-day an +innumerable multitude of little stars which reveal the existence of an +entire universe in this region. + +Orion is not merely the most imposing of the celestial figures; it is +also the richest in sidereal wonders. Among these, it exhibits the most +complex of all the multiple systems known to us: that of the star +[theta] situated in the celebrated nebula just mentioned. This marvelous +star, viewed through a powerful telescope, breaks up into six suns, +forming a most remarkable stellar group. + +This region is altogether one of the most brilliant in the entire +firmament. We must no longer postpone our homage to the brightest star +in the sky, the magnificent Sirius, which shines on the left below +Orion: it returns every year toward the end of November. This marvelous +star, of dazzling brilliancy, is the first, [alpha], in the +constellation of the Great Dog, which forms a quadrilateral, the base of +which is adjacent to a triangle erected from the horizon. + +When astronomers first endeavored to determine the distance of the +stars, Sirius, which attracted all eyes to its burning fires, was the +particular object of attention. After long observation, they succeeded +in determining its distance as 92 trillion kilometers (57 trillion +miles). Light, that radiates through space at a velocity of 300,000 +kilometers (186,000 miles) per second, takes no less than ten years to +reach us from this sun, which, nevertheless, is one of our neighbors. + +The Little Dog, in which Procyon ([alpha], of first magnitude) shines +out, is above its big brother. With the exception of [alpha], it has no +bright stars. + +[Illustration: FIG. 13.--Winter Constellations.] + +Lastly, toward the southern horizon, we must notice the Hydra, Eridanus, +the Whale, the Southern Fish, the Ship, and the Centaur. This last +constellation, while invisible to our latitudes, contains the star that +is nearest to the Earth, [alpha], of first magnitude, the distance of +which is 40 trillion kilometers (25 trillion miles). + +[Illustration: FIG. 14.--Spring Constellations.] + +The feet of the Centaur touch the Southern Cross, which is always +invisible to us, and a little farther down the Southern Pole reigns +over the icy desert of the antarctic regions. + +[Illustration: FIG. 15.--Summer Constellations.] + +[Illustration: FIG. 16.--Autumn Constellations.] + +In order to complete the preceding descriptions, we subjoin four charts +representing the aspect of the starry heavens during the evenings of +winter, spring, summer, and autumn. To make use of these, we must +suppose them to be placed above our heads, the center marking the +zenith, and the sky descending all round to the horizon. The horizon, +therefore, bounds these panoramas. Turning the chart in any direction, +and looking at it from north, south, east, or west, we find all the +principal stars. The first map (Fig. 13) represents the sky in winter +(January) at 8 P.M.; the second, in spring (April) at 9 P.M.; the third, +in summer (July) at the same hour; the fourth, the sky in autumn +(October) at the same time. + +And so, at little cost, we have made one of the grandest and most +beautiful journeys conceivable. We now have a new country, or, better, +have learned to see and know our own country, for since the Earth is a +planet we must all be citizens of the Heavens before we can belong to +such or such a nation of our lilliputian world. + +We must now study this sublime spectacle of the Heavens in detail. + + + + +CHAPTER III + +THE STARS, SUNS OF THE INFINITE + +A JOURNEY THROUGH SPACE + + +We have seen from the foregoing summary of the principal Constellations +that there is great diversity in the brightness of the stars, and that +while our eyes are dazzled with the brilliancy of certain orbs, others, +on the contrary, sparkle modestly in the azure depths of the night, and +are hardly perceptible to the eye that seeks to plumb the abysses of +Immensity. + +We have appended the word "magnitude" to the names of certain stars, and +the reader might imagine this to bear some relation to the volume of the +orb. But this is not the case. + +To facilitate the observation of stars of varying brilliancy, they have +been classified in order of magnitude, according to their apparent +brightness, and since the dimensions of these distant suns are almost +wholly unknown to us, the most luminous stars were naturally denoted as +of first magnitude, those which were a little less bright of the second, +and so on. But in reality this word "magnitude" is quite erroneous, for +it bears no relation to the mass of the stars, divided thus at an epoch +when it was supposed that the most brilliant must be the largest. It +simply indicates the apparent brightness of a star, the real brilliancy +depending on its dimensions, its intrinsic light, and its distance from +our planet. + +And now to make some comparison between the different orders. Throughout +the entire firmament, only nineteen stars of first magnitude are +discoverable. And, strictly speaking, the last of this series might just +as well be noted of "second magnitude," while the first of the second +series might be added to the list of stars of the "first order." But in +order to form classes distinct from one another, some limit has to be +adopted, and it was determined that the first series should include only +the following stars, the most luminous in the Heavens, which are +subjoined in order of decreasing brilliancy. + + +STARS OF THE FIRST MAGNITUDE + + 1. Sirius, or [alpha] of the Great Dog. + 2. Canopus, or [alpha] of the Ship. + 3. Capella, or [alpha] of the Charioteer. + 4. Arcturus, or [alpha] of the Herdsman. + 5. Vega, or [alpha] of the Lyre. + 6. Proxima, or [alpha] of the Centaur. + 7. Rigel, or [beta] of Orion. + 8. Achernar, or [alpha] of Eridanus. + 9. Procyon, or [alpha] of the Little Dog. + 10. [beta] of the Centaur. + 11. Betelgeuse, or [alpha] of Orion. + 12. Altaïr, or [alpha] of the Eagle. + 13. [alpha] of the Southern Cross. + 14. Aldebaran, or [alpha] of the Bull. + 15. Spica, or [alpha] of the Virgin. + 16. Antares, or [alpha] of the Scorpion. + 17. Pollux, or [beta] of the Twins. + 18. Regulus, or [alpha] of the Lion. + 19. Fomalhaut, or [alpha] of the Southern Fish. + + +THE STARS OF THE SECOND MAGNITUDE + +Then come the stars of the second magnitude, of which there are +fifty-nine. The stars of the Great Bear (with the exception of [delta], +which is of third magnitude), the Pole-Star, the chief stars in Orion +(after Rigel and Betelgeuse), of the Lion, of Pegasus, of Andromeda, of +Cassiopeia, are of this order. These, with the former, constitute the +principal outlines of the constellations visible to us. + +Then follow the third and fourth magnitudes, and so on. + + * * * * * + +The following table gives a summary of the series, down to the sixth +magnitude, which is the limit of visibility for the unaided human eye: + + 19 stars of first magnitude. + 59 of second magnitude. + 182 of third magnitude. + 530 of fourth magnitude. + 1,600 of fifth magnitude. + 4,800 of sixth magnitude. + +This makes a total of some seven thousand stars visible to the unaided +eye. It will be seen that each series is, roughly speaking, three times +as populated as that preceding it; consequently, if we multiply the +number of any class by three, we obtain the approximate number of stars +that make up the class succeeding it. + +Seven thousand stars! It is an imposing figure, when one reflects that +all these lucid points are suns, as enormous as they are potent, as +incandescent as our own (which exceeds the volume of the Earth by more +than a million times), distant centers of light and heat, exerting their +attraction on unknown systems. And yet it is generally imagined that +millions of stars are visible in the firmament. This is an illusion; +even the best vision is unable to distinguish stars below the sixth +magnitude, and ordinary sight is far from discovering all of these. + +Again, seven thousand stars for the whole Heavens makes only three +thousand five hundred for half the sky. And we can only see one +celestial hemisphere at a time. Moreover, toward the horizon, the vapor +of the atmosphere veils the little stars of sixth magnitude. In reality, +we never see at a given moment more than three thousand stars. This +number is below that of the population of a small town. + + * * * * * + +But celestial space is unlimited, and we must not suppose that these +seven thousand stars that fascinate our eyes and enrich our Heavens, +without which our nights would be black, dark, and empty,[5] comprise +the whole of Creation. They only represent the vestibule of the temple. + +Where our vision is arrested, a larger, more powerful eye, that is +developing from century to century, plunges its analyzing gaze into the +abysses, and reflects back to the insatiable curiosity of science the +light of the innumerable suns that it discovers. This eye is the lens of +the optical instruments. Even opera-glasses disclose stars of the +seventh magnitude. A small astronomical objective penetrates to the +eighth and ninth orders. More powerful instruments attain the tenth. +The Heavens are progressively transformed to the eye of the astronomer, +and soon he is able to reckon hundreds of thousands of orbs in the +night. The evolution continues, the power of the instrument is +developed; and the stars of the eleventh and twelfth magnitudes are +discovered successively, and together number four millions. Then follow +the thirteenth, fourteenth, and fifteenth magnitudes. This is the +sequence: + + 7th magnitude 13,000. + 8th " 40,000. + 9th " 120,000. + 10th " 380,000. + 11th " 1,000,000. + 12th " 3,000,000. + 13th " 9,000,000. + 14th " 27,000,000. + 15th " 80,000,000. + +Accordingly, the most powerful telescopes of the day, reenforced by +celestial photography, can bring a stream of more than 120 millions of +stars into the scope of our vision. + +The photographic map of the Heavens now being executed comprises the +first fourteen magnitudes, and will give the precise position of some +40,000,000 stars, distributed over 22,054 sheets, forming a sphere 3 +meters 44 centimeters in diameter. + +The boldest imagination is overwhelmed by these figures, and fails to +picture such millions of suns--formidable and burning globes that roll +through space, sweeping their systems along with them. What furnaces are +there! what unknown lives! what vast immensities! + +And again, what enormous distances must separate the stars, to admit of +their free revolution in the ether! In what abysses, at what a distance +from our terrestrial atom, must these magnificent and dazzling Suns +pursue the paths traced for them by Destiny! + + * * * * * + +If all the stars radiated an equal light, their distances might be +calculated on the principle that an object appears smaller in proportion +to its distance. But this equality does not exist. The suns were not all +cast in the same mold. + +Indeed, the stars differ widely in size and brightness, and the +distances that have been measured show that the most brilliant are not +the nearest. They are scattered through Space at all distances. + +Among the nearer stars of which it has been found possible to calculate +the distance, some are found to be of the fourth, fifth, sixth, seventh, +eighth, and even ninth magnitudes, proving that the most brilliant are +not always the least distant. + +For the rest, among the beautiful and shining stars with which we made +acquaintance in the last chapter may be cited Sirius, which at a +distance of 92 trillion kilometers (57 trillion miles) from here still +dazzles us with its burning fires; Procyon or [alpha] of the Little Dog, +as remote as 112 trillion kilometers (69-1/2 trillion miles); Altaïr of +the Eagle, at 160 trillion kilometers (99 trillion miles); the white +Vega, at 204 trillion kilometers (126-1/2 trillion miles); Capella, at +276 trillion kilometers (171 trillion miles); and the Pole-Star at 344 +trillion kilometers (213-1/2 trillion miles). The light that flies +through Space at a velocity of 300,000 kilometers (186,000 miles) per +second, takes thirty-six years and a half to reach us from this distant +sun: _i.e._, the luminous ray we are now receiving from Polaris has been +traveling for more than the third of a century. When you, gentle reader, +were born, the ray that arrives to-day from the Pole-Star was already +speeding on its way. In the first second after it had started it +traveled 300,000 kilometers; in the second it added another 300,000 +which at once makes 600,000 kilometers; add another 300,000 kilometers +for the third second, and so on during the thirty-six years and a half. + +If we tried to arrange the number 300,000 (which represents the distance +accomplished in one second) in superposed rows, as if for an addition +sum, as many times as is necessary to obtain the distance that +separates the Pole-Star from our Earth, the necessary operation would +comprise 1,151,064,000 rows, and the sheet of paper required for the +setting out of such a sum would measure approximately 11,510 kilometers +(about 7,000 miles), _i.e._, almost the diameter of our terrestrial +globe, or about four times the distance from Paris to Moscow! + +Is it not impossible to realize that our Sun, with its entire system, is +lost in the Heavens at such a distance from his peers in Space? At the +distance of the least remote of the stars he would appear as one of the +smallest. + + * * * * * + +The nearest star to us is [alpha] of the Centaur, of first magnitude, a +neighbor of the South Pole, invisible in our latitudes. Its distance is +275,000 radii of the terrestrial orbit, _i.e._, 275,000 times 149 +million kilometers, which gives 41 trillions, or 41,000 milliards of +kilometers (= 25-1/2 trillion miles). [A milliard = 1,000 millions, the +French billion. A trillion = 1,000 milliards, or a million millions, the +English billion. The _French_ nomenclature has been retained by the +translator.] At a speed of 300,000 kilometers (186,000 miles) per second +the light takes four years to come from thence. It is a fine double +star. + +The next nearest star after this is a little orb invisible to the +unaided eye. It has no name, and stands as No. 21,185 in the Catalogue +of Lalande. It almost attains the seventh magnitude (6.8). Its distance +is 64 trillion kilometers (39-1/2 trillion miles). + +The third of which the distance has been measured is the small star in +Cygnus, already referred to in Chapter II, in describing the +Constellations. Its distance is 69 trillion kilometers (42-1/2 trillion +miles). This, too, is a double star. The light takes seven years to +reach us. + +As we have seen, the fine stars Sirius, Procyon, Aldebaran, Altaïr, +Vega, and Capella are more remote. + +Our solar system is thus very isolated in the vastness of Infinitude. +The latest known planet of our system, Neptune, performs its revolutions +in space at 4 milliards, 470 million kilometers (2,771,400,000 miles) +from our Sun. Even this is a respectable distance! But beyond this +world, an immense gulf, almost a void abyss, extends to the nearest +star, [alpha] of the Centaur. Between Neptune and Centauris there is no +star to cheer the black and cold solitude of the immense vacuum. One or +two unknown planets, some wandering comets, and swarms of meteors, +doubtless traverse those unknown spaces, but all invisible to us. + +Later on we will discuss the methods that have been employed in +measuring these distances. Let us now continue our description. + + * * * * * + +Now that we have some notion of the distance of the stars we must +approach them with the telescope, and compare them one with another. + +Let us, for example, get close to Sirius: in this star we admire a sun +that is several times heavier than our own, and of much greater mass, +accompanied by a second sun that revolves round it in fifty years. Its +light is exceedingly white, and it notably burns with hydrogen flames, +like Vega and Altaïr. + +Now let us approach Arcturus, Capella, Aldebaran: these are yellow stars +with golden rays, like our Sun, and the vapor of iron, of sodium, and of +many other metals can be identified in their spectrum. These stars are +older than the first, and the ruddy ones, such as Antares, Betelgeuse, +[alpha] of Hercules, are still older; several of them are variable, and +are on their way to final extinction. + +The Heavens afford us a perennial store of treasure, wherein the +thinker, poet or artist can find inexhaustible subjects of +contemplation. + +You have heard of the celestial jewels, the diamonds, rubies, emeralds, +sapphires, topazes, and other precious stones of the sidereal casket. +These marvels are met with especially among the double stars. + +Our Sun, white and solitary, gives no idea of the real aspect of some of +its brothers in Infinitude. There are as many different types as there +are suns! + +Stars, you will think, are like individuals: each has its distinct +characteristics: no two are comparable. And indeed this reflection is +justified. While human vanity does homage to Phoebus, divine King of +the Heavens, other suns of still greater magnificence form groups of two +or three splendid orbs, which roll the prodigious combinations of their +double, triple, or multiple systems through space, pouring on to the +worlds that accompany them a flood of changing light, now blue, now red, +now violet, etc. + +In the inexhaustible variety of Creation there exist Suns that are +united in pairs, bound by a common destiny, cradled in the same +attraction, and often colored in the most delicate and entrancing shades +conceivable. Here will be a dazzling ruby, its glowing color shedding +joy; there a deep blue sapphire of tender tone; beyond, the finest +emeralds, hue of hope. Diamonds of translucent purity and whiteness +sparkle from the abyss, and shed their penetrating light into the vast +space. What splendors are scattered broadcast over the sky! what +profusion! + +To the naked eye, the groups appear like ordinary stars, mere luminous +points of greater or less brilliancy; but the telescope soon discovers +the beauty of these systems; the star is duplicated into two distinct +suns, in close proximity. These groups of two or several suns are not +merely due to an effect of perspective--_i.e._, the presence of two or +more stars in our line of sight; as a rule they constitute real physical +systems, and these suns, associated in a common lot, rotate round one +another in a more or less rapid period, that varies for each system. + +One of the most splendid of these _double stars_, and at the same time +one of the easiest to perceive, is [zeta] in the Great Bear, or Mizar, +mentioned above in describing this constellation. It has no contrasting +colors, but exactly resembles twin diamonds of the finest water, which +fascinate the gaze, even through a small objective. + +Its components are of the second and fourth magnitudes, their distance = +14"[6]. Some idea of their appearance in a small telescope may be +obtained from the subjoined figure (Fig. 17). + +Another very brilliant pair is Castor. Magnitudes second and third. +Distance 5.6"". Very easy to observe. [gamma] in the Virgin resolves +into two splendid diamonds of third magnitude. Distance, 5.0". Another +double star is [gamma] of the Ram, of fourth magnitude. Distance, 8.9". + +[Illustration: FIG. 17.--The double star Mizar.] + +And here are two that are even more curious by reason of their coloring: +[gamma] in Andromeda, composed of a fine orange star, and one +emerald-green, which again is accompanied by a tiny comrade of the +deepest blue. This group in a good telescope is most attractive. +Magnitudes, second and fifth. Distance, 10". + +[beta] of the Swan, or Albireo, referred to in the last chapter, has +been analyzed into two stars: one golden-yellow, the other sapphire. +Magnitudes, third and fifth. Distance, 34". [alpha] of the Greyhounds, +known also as the Heart of Charles II, is golden-yellow and lilac. +Magnitudes, third and fifth. Distance 20".[7] + +[alpha] of Hercules revolves a splendid emerald and a ruby in the skies; +[zeta] of the Lyre exhibits a yellow and a green star; Rigel, an +electric sun, and a small sapphire; Antares is ruddy and emerald-green; +[eta] of Perseus resolves into a burning red star, and one smaller that +is deep blue, and so on. + + * * * * * + +These exquisite double stars revolve in gracious and splendid couples +around one another, as in some majestic valse, marrying their +multi-colored fires in the midst of the starry firmament. + +Here, we constantly receive a pure and dazzling white light from our +burning luminary. Its ray, indeed, contains the potentiality of every +conceivable color, but picture the fantastic illumination of the worlds +that gravitate round these multiple and colored suns as they shed floods +of blue and roseate, red, or orange light around them! What a fairy +spectacle must life present upon these distant universes! + +Let us suppose that we inhabit a planet illuminated by two suns, one +blue, the other red. + +It is morning. The sapphire sun climbs slowly up the Heavens, coloring +the atmosphere with a somber and almost melancholy hue. The blue disk +attains the zenith, and is beginning its descent toward the West, when +the East lights up with the flames of a scarlet sun, which in its turn +ascends the heights of the firmament. The West is plunged in the +penumbra of the rays of the blue sun, while the East is illuminated with +the purple and burning rays of the ruby orb. + +The first sun is setting when the second noon shines for the inhabitants +of this strange world. But the red sun, too, accomplishes the law of its +destiny. Hardly has it disappeared in the conflagration of its last +rays, with which the West is flushed, when the blue orb reappears on the +opposite side, shedding a pale azure light upon the world it +illuminates, which knows no night. And thus these two suns fraternize in +the Heavens over the common task of renewing a thousand effects of +extra-terrestrial light for the globes that are subject to their +variations. + +Scarlet, indigo, green, and golden suns; pearly and multi-colored Moons; +are these not fairy visions, dazzling to our poor sight, condemned while +here below to see and know but one white Sun? + +As we have learned, there are not only double, but triple, and also +multiple stars. One of the finest ternary systems is that of [gamma] in +Andromeda, above mentioned. Its large star is orange, its second green, +its third blue, but the two last are in close juxtaposition, and a +powerful telescope is needed to separate them. A triple star more easy +to observe is [zeta] of Cancer, composed of three orbs of fifth +magnitude, at a distance of 1" and 5"; the first two revolve round their +common center of gravity in fifty-nine years, the third takes over three +hundred years. The preceding figure shows this system in a fairly +powerful objective (Fig. 18). + +[Illustration: FIG. 18.--Triple star [zeta] in Cancer.] + +In the Lyre, a little above the dazzling Vega, [epsilon] is of fourth +magnitude, which seems a little elongated to the unaided eye, and can +even be analyzed into two contiguous stars by very sharp sight. But on +examining this attractive pair with a small glass, it is further obvious +that each of these stars is double; so that they form a splendid +quadruple system of two couples (Fig. 19): one of fifth and a half and +sixth magnitudes, at a distance of 2.4", the other of sixth and +seventh, 3.2" distant. The distance between the two pairs is 207". + +[Illustration: FIG. 19.--Quadruple star [epsilon] of the Lyre.] + +In speaking of Orion, we referred to the marvelous star [theta] situated +in the no less famous Nebula, below the Belt; this star forms a +dazzling sextuple system, in the very heart of the nebula (Fig. 20). How +different to our Sun, sailing through Space in modest isolation! + +Be it noted that all these stars are animated by prodigious motions that +impel them in every direction. + +[Illustration: FIG. 20.--Sextuple star [theta] in the Nebula of Orion.] + +There are no fixed stars. On every side throughout Infinity, the burning +suns--enormous globes, blazing centers of light and heat--are flying at +giddy speed toward an unknown goal, traversing millions of miles each +day, crossing century by century such vast spaces as are inconceivable +to the human intellect. + +If the stars appear motionless to us, it is because they are so remote, +their secular movements being only manifested on the celestial sphere by +imperceptible displacements. But in reality these suns are in perpetual +commotion in the abysses of the Heavens, which they quicken with an +extraordinary animation. + +These perpetual and cumulative motions must eventually modify the aspect +of the Constellations: but these changes will only take effect very +slowly; and for thousands and thousands of years longer the heroes and +heroines of mythology will keep their respective places in the Heavens, +and reign undisturbed beneath the starry vault. + +Examination of these star motions reveals the fact that our Sun is +plunging with all his system (the Earth included) toward the +Constellation of Hercules. We are changing our position every moment: in +an hour we shall be 70,000 kilometers (43,500 miles) farther than we are +at present. The Sun and the Earth will never again traverse the space +they have just left, and which they have deserted forever. + +And here let us pause for an instant to consider the _variable stars_. +Our Sun, which is constant and uniform in its light, does not set the +type of all the stars. A great number of them are variable--either +periodically, in regular cycles--or irregularly. + +We are already acquainted with the variations of Algol, in Perseus, due +to its partial eclipse by a dark globe gravitating in the line of our +vision. There are several others of the same type: these are not, +properly speaking, variable stars. But there are many others the +intrinsic light of which undergoes actual variations. + +In order to realize this, let us imagine that our Earth belongs to such +a sun, for example, to a star in the southern constellation of the +Whale, indicated by the letter [omicron], which has been named the +"wonderful" (Mira Ceti). Our new sun is shining to-day with a dazzling +light, shedding the gladness of his joyous beams upon nature and in our +hearts. For two months we admire the superb orb, sparkling in the azure +illuminated with its radiance. Then of a sudden, its light fades, and +diminishes in intensity, though the sky remains clear. Imperceptibly, +our fine sun darkens; the atmosphere becomes sad and dull, there is an +anticipation of universal death. For five long months our world is +plunged in a kind of penumbra; all nature is saddened in the general +woe. + +But while we are bewailing the cruelty of our lot, our cherished +luminary revives. The intensity of its light increases slowly. Its +brilliancy augments, and finally, at the end of three months, it has +recovered its former splendors, and showers its bright beams upon our +world, flooding it with joy. But--we must not rejoice too quickly! This +splendid blaze will not endure. The flaming star will pale once more; +fade back to its minimum; and then again revive. Such is the nature of +this capricious sun. It varies in three hundred and thirty-one days, and +from yellow at the maximum, turns red at the minimum. This star, Mira +Ceti, which is one of the most curious of its type, varies from the +second to the ninth magnitudes: we cite it as one example; hundreds of +others might be instanced. + +Thus the sky is no black curtain dotted with brilliant points, no empty +desert, silent and monotonous. It is a prodigious theater on which the +most fantastic plays are continually being acted. Only--there are no +spectators. + +Again, we must note the _temporary stars_, which shine for a certain +time, and then die out rapidly. Such was the star in Cassiopeia, in +1572, the light of which exceeded Sirius in its visibility in full +daylight, burning for five months with unparalleled splendor, dominating +all other stars of first magnitude; after which it died out gradually, +disappearing at the end of seventeen months, to the terror of the +peoples, who saw in it the harbinger of the world's end: that of 1604, +in the Constellation of the Serpent, which shone for a year; of 1866, of +second magnitude, in the Northern Crown, which appeared for a few weeks +only; of 1876, in the Swan; of 1885, in the Nebula of Andromeda; of +1891, in the Charioteer; and quite recently, of 1901, in Perseus. + +These temporary stars, which appear spontaneously to the observers on +the Earth, and quickly vanish again, are doubtless due to collisions, +conflagrations, or celestial cataclysms. But we only see them long after +the epoch at which the phenomena occurred, years upon years, and +centuries ago. For instance, the conflagration photographed by the +author in 1901, in Perseus, must have occurred in the time of Queen +Elizabeth. It has taken all this time for the rays of light to reach us. + + * * * * * + +The Heavens are full of surprises, on which we can bestow but a fleeting +glance within these limits. They present a field of infinite variety. + +Who has not noticed the Milky Way, the pale belt that traverses the +entire firmament and is so luminous on clear evenings in the +Constellations of the Swan and the Lyre? It is indeed a swarm of stars. +Each is individually too small to excite our retina, but as a whole, +curiously enough, they are perfectly visible. With opera-glasses we +divine the starry constitution: a small telescope shows us marvels. +Eighteen millions of stars were counted there with the gauges of William +Herschel. + +Now this Milky Way is a symbol, not of the Universe, but of the +Universes that succeed each other through the vast spaces to Infinity. + +Our Sun is a star of the Milky Way. It surrounds us like a great circle, +and if the Earth were transparent, we should see it pass beneath our +feet as well as over our heads. It consists of a very considerable mass +of star-clusters, varying greatly in extent and number, some projected +in front of others, while the whole forms an agglomeration. + +[Illustration: FIG. 21.--The Star-Cluster in Hercules.] + +Among this mass of star-groups, several thousands of which are already +known to us, we will select one of the most curious, the Cluster in +Hercules, which can be distinguished with the unaided eye, between the +stars [eta] and [zeta] of that constellation. Many photographs of it +have been taken in the author's observatory at Juvisy, showing some +thousands of stars; and one of these is reproduced in the accompanying +figure (Fig. 21). Is it not a veritable universe? + +[Illustration: FIG. 22.--The Star-Cluster in the Centaur.] + +Another of the most beautiful, on account of its regularity, is that of +the Centaur (Fig. 22). + +These groups often assume the most extraordinary shapes in the +telescope, such as crowns, fishes, crabs, open mouths, birds with +outspread wings, etc. + +We must also note the _gaseous nebulæ_, universes in the making, +_e.g._, the famous Nebula in Orion, of which we obtained some notion a +while ago in connection with its sextuple star: and also that in +Andromeda (Fig. 23). + +[Illustration: FIG. 23.--The Nebula in Andromeda.] + +[Illustration: FIG. 24.--Nebula in the Greyhounds.] + +Perhaps the most marvelous of all is that of the Greyhounds, which +evolves in gigantic spirals round a dazzling focus, and then loses +itself far off in the recesses of space. Fig. 24 gives a picture of it. + +[Illustration: FIG. 25.--The Pleiades.] + +Without going thus far, and penetrating into telescopic depths, my +readers can get some notion of these star-clusters with the help of a +small telescope or opera-glasses, or even with the unaided eye, by +looking at the beautiful group of the Pleiades, already familiar to us +on another page, and using it as a test of vision. The little map +subjoined (Fig. 25) will be an assistance in recognizing them, and in +estimating their magnitudes, which are in the following order: + + Alcyone 3.0. + Electra 4.5. + Atlas 4.6. + Maia 5.0. + Merope 5.5. + Taygeta 5.8. + Pleione 6.3. + Celæno 6.5. + Asterope 6.8. + +Good eyes distinguish the first six, sharp sight detects the three +others. + +In the times of the ancient Greeks, seven were accounted of equal +brilliancy, and the poets related that the seventh star had fled at the +time of the Trojan War. Ovid adds that she was mortified at not being +embraced by a god, as were her six sisters. It is probable that only the +best sight could then distinguish Pleione, as in our own day. The +angular distance from Atlas to Pleione is 5'. + +The length of this republic, from Atlas and Pleione to Celæno, is 4'/23" +of time, or 1°6' of arc; the breadth, from Merope to Asterope, is +36'.[8] + +In the quadrilateral, the length from Alcyone to Electra is 36', and the +breadth from Merope to Maia 25'. To us it appears as though, if the Full +Moon were placed in front of this group of nine stars, she would cover +it entirely, for to the naked eye she appears much larger than all the +Pleiades together. But this is not so. She only measures 31', less than +half the distance from Atlas to Celæno; she is hardly broader than the +distance from Alcyone to Atlas, and could pass between Merope and +Taygeta without touching either of these stars. This is a perennial and +very curious optical illusion. When the Moon passes in front of the +Pleiades, and occults them successively, it is hard to believe one's +eyes. The fact occurred, _e.g._, on July 23, 1897, during a fine +occultation observed at the author's laboratory of Juvisy (Fig. 26). + +[Illustration: FIG. 26.--Occultation of the Pleiades by the Moon.] + +Photography here discovers to us, not 6, 9, 12, 15, or 20 stars, but +hundreds and millions. + +These are the most brilliant flowers of the celestial garden. + +[Illustration: FIG. 27.--Stellar dial of the double star [gamma] of the +Virgin.] + +We, alas, can but glance at them rapidly. In contemplating them we are +transported into immensities both of space and time, for the stellar +periods measured by these distant universes often overpower in their +magnitude the rapid years in which our terrestrial days are estimated. +For instance, one of the double stars we spoke of above, [gamma] of the +Virgin, sees its two components, translucent diamonds, revolve around +their common center of gravity, in one hundred and eighty years. How +many events took place in France, let us say, in a single year of this +star!--The Regency, Louis XV, Louis XVI, the Revolution, Napoleon, Louis +XVIII, Louis Philippe, the Second Republic, Napoleon III, the +Franco-German War, the Third Republic.... What revolutions here, during +a single year of this radiant pair! (Fig. 27.) + +But the pageant of the Heavens is too vast, too overwhelming. We must +end our survey. + +Our Milky Way, with its millions of stars, represents for us only a +portion of the Creation. The illimitable abysses of Infinitude are +peopled by other universes as vast, as imposing, as our own, which are +renewed in all directions through the depths of Space to endless +distance. Where is our little Earth? Where our Solar System? We are fain +to fold our wings, and return from the Immense and Infinite to our +floating island. + + + + +CHAPTER IV + +OUR STAR THE SUN + + +In the incessant agitation of daily life in which we are involved by the +thousand superfluous wants of modern "civilization," one is prone to +assume that existence is complete only when it reckons to the good an +incalculable number of petty incidents, each more insignificant than the +last. Why lose time in thinking or dreaming? We must live at fever heat, +must agitate, and be infatuated for inanities, must create imaginary +desires and torments. + +The thoughtful mind, prone to contemplation and admiration of the +beauties of Nature, is ill at ease in this perpetual vortex that +swallows everything--satisfaction, in a life that one has not time to +relish; love of the beautiful, that one views with indifference; it is a +whirlpool that perpetually hides Truth from us, forgotten forever at the +bottom of her well. + +And why are our lives thus absorbed in merely material interests? To +satisfy our pride and vanity! To make ourselves slaves to chimeras! If +the Moon were inhabited, and if her denizens could see us plainly +enough to note and analyze the details of human existence on the surface +of our planet, it would be curious and perhaps a little humiliating for +us, to see their statistics. What! we should say, is this the sum of our +lives? Is it for this that we struggle, and suffer, and die? Truly it is +futile to give ourselves such trouble. + +And yet the remedy is simple, within the power of every one; but one +does not think of it just because it is too easy, although it has the +immense advantage of lifting us out of the miseries of this weary world +toward the inexpressible happiness that must always awaken in us with +the knowledge of the Truth: we need only open our eyes to see, and to +look out. Only--one hardly ever thinks of it, and it is easier to let +one's self be blinded by the illusion and false glamor of appearances. + +Think what it would be to consecrate an hour each day to voluntary +participation in the harmonious Choir of Nature, to raise one's eyes +toward the Heavens, to share the lessons taught by the Pageant of the +Universe! But, no: there is no time, no time for the intellectual life, +no time to become attached to real interests, no time to pursue them. + +Among the objects marshaled for us in the immense spectacle of Nature, +nothing without exception has struck the admiration and attention of +man as much as the Sun, the God of Light, the fecundating orb, without +which our planet and its life would never have issued from nonentity, +_the visible image of the invisible god_, as said Cicero, and the poets +of antiquity. And yet how many beyond the circle of those likely to read +these pages know that this Sun is a star in the Milky Way, and that +every star is a sun? How many take any account of the reality and +grandeur of the Universe? Inquire, and you will find that the number of +people who have any notion, however rudimentary, of its construction, is +singularly restricted. Humanity is content to vegetate, much after the +fashion of a race of moles. + +Henceforward, you will know that you are living in the rays of a star, +which, from its proximity, we term a sun. To the inhabitants of other +systems of worlds, our splendid Sun is only a more or less brilliant, +luminous point, according as the spot from which it is observed is +nearer or farther off. But to us its "terrestrial" importance renders it +particularly precious; we forget all the sister stars on its account, +and even the most ignorant hail it with enthusiasm without exactly +knowing what its rôle in the universe may be, simply because they feel +that they depend on it, and that without it life would become extinct on +this globe. Yes, it is the beneficent rays of the Sun that shed upon +our Earth the floods of light and heat to which Life owes its existence +and its perpetual propagation. + +Hail, vast Sun! a little star in Infinitude, but for us a colossal and +portentous luminary. Hail, divine Benefactor! How should we not adore, +when we owe him the glow of the warm and cheery days of summer, the +gentle caresses by which his rays touch the undulating ears, and gild +them with the touch? The Sun sustains our globe in Space, and keeps it +within his rays by the mysteriously powerful and delicate cords of +attraction. It is the Sun that we inhale from the embalmed corollas of +the flowers that uplift their gracious heads toward his light, and +reflect his splendors back to us. It is the Sun that sparkles in the +foam of the merry wine; that charms our gaze in those first days of +spring, when the home of the human race is adorned with all the charms +of verdant and flowering youth. Everywhere we find the Sun; everywhere +we recognize his work, extending from the infinitely great to the +infinitely little. We bow to his might, and admire his power. When in +the sad winter day he disappears behind the snowy eaves, we think his +fiery globe will never rise to mitigate the short December days which +are alleviated with his languid beams. + +April restores him to superb majesty, and our hearts are filled with +hope in the illumination of those beauteous, sunny hours. + + * * * * * + +Our celestial journey carried us far indeed from our own Solar System. +Guided by the penetrating eye of the telescope, we reached such distant +creations that we lost sight of our cherished luminary. + +But we remember that he burns yonder, in the midst of the pale cosmic +cloud we term the Milky Way. Let us approach him, now that we have +visited the Isles of Light in the Celestial Ocean; let us traverse the +vast plains strewn with the burning gold of the Suns of the Infinite. + +We embark upon a ray of light, and glide rapidly to the portals of our +Universe. Soon we perceive a tiny speck, scintillating feebly in the +depths of Space, and recognize it as our own celestial quarters. This +little star shines like the head of a gold pin, and increases in size as +we advance toward it. We traverse a few more trillion miles in our rapid +course, and it shines out like a fine star of the first magnitude. It +grows larger and larger. Soon we divine that it is our humble Earth that +is shining before us, and gladly alight upon her. In future we shall not +quit our own province of the Celestial Kingdom, but will enter into +relations with this solar family, which interests us the more in that it +affects us so closely. + +[Illustration: FIG. 28.--Comparative sizes of the Sun and Earth.] + +The Sun, which is manifested to us as a fine white disk at noon, while +it is fiery red in the evening, at its setting, is an immense globe, +whose colossal dimensions surpass those of our terrestrial atom beyond +all conceivable proportion. + +In diameter, it is, in effect, 108-1/2 times as large as the Earth; that +is to say, if our planet be represented by a globe 1 meter in diameter, +the Sun would figure as a sphere 108-1/2 meters across. This is shown on +the accompanying figure (Fig. 28), which is in exact proportion. + +If our world were set down upon the Sun, with all its magnificence, all +its wealth, its mountains, its seas, its monuments, and its inhabitants, +it would only be an imperceptible speck. It would occupy less space in +the central orb than one grain in a grenade. If the Earth were placed in +the center of the Sun, with the Moon still revolving round it at her +proper distance of 384,000 kilometers (238,500 miles), only half the +solar surface would be covered. + +In volume the Sun is 1,280,000 times vaster than our abode, and 324,000 +times heavier in mass. That the giant only appears to us as a small +though very brilliant disk, is solely on account of its distance. Its +apparent dimensions by no means reveal its majestic proportions to us. + +When observed with astronomical instruments, or photographed, we +discover that its surface is not smooth, as might be supposed, but +granulated, presenting a number of luminous points dispersed over a +more somber background. These granulations are somewhat like the pores +of a fruit, _e.g._, a fine orange, the color of which recalls the hue of +the Sun when it sinks in the evening, and prepares to plunge us into +darkness. At times these pores open under the influence of disturbances +that arise upon the solar surface, and give birth to a Sun-Spot. For +centuries scientists and lay people alike refused to admit the existence +of these spots, regarding them as so many blemishes upon the King of the +Heavens. Was not the Sun the emblem of inviolable purity? To find any +defect in him were to do him grievous injury. Since the orb of day was +incorruptible, those who threw doubt on his immaculate splendor were +fools and idiots. And so when Scheiner, one of the first who studied the +solar spots with the telescope, published the result of his experiments +in 1610, no one would believe his statements. + +Yet, from the observations of Galileo and other astronomers, it became +necessary to accept the evidence, and stranger still to recognize that +it is by these very spots that we are enabled to study the physical +constitution of the Sun. + +They are generally rounded or oval in shape, and exhibit two distinct +parts; first, the central portion, which is black, and is called the +_nucleus_, or _umbra_; second, a clearer region, half shaded, which has +received the name of _penumbra_. These parts are sharply defined in +outline; the penumbra is gray, the nucleus looks black in relation to +the dazzling brilliancy of the solar surface; but as a matter of fact it +radiates a light 2,000 times superior in intensity to that of the full +moon. + +[Illustration: FIG. 29.--Direct photograph of the Sun.] + +Some idea of the aspect of these spots may be obtained from the +accompanying reproduction of a photograph of the Sun (taken September 8, +1898, at the author's observatory at Juvisy), and from the detailed +drawing of the large spot that broke out some days later (September 13), +crossed by a bridge, and furrowed with flames. As a rule, the spots +undergo rapid transformations. + +[Illustration: FIG. 30.--Telescopic aspect of a Sun-Spot.] + +These spots, which appear of insignificant dimensions to the observers +on the Earth, are in reality absolutely gigantic. Some that have been +measured are ten times as large as the Earth's diameter, _i.e._, 120,000 +kilometers (74,500 miles). + +Sometimes the spots are so large that they can be seen with the unaided +eye (protected with black or dark-blue glasses). They are not formed +instantaneously, but are heralded by a vast commotion on the solar +surface, exhibiting, as it were, luminous waves or _faculæ_. Out of this +agitation arises a little spot, that is usually round, and enlarges +progressively to reach a maximum, after which it diminishes, with +frequent segmentation and shrinkage. Some are visible only for a few +days; others last for months. Some appear, only to be instantly +swallowed in the boiling turmoil of the flaming orb. Sometimes, again, +white incandescent waves emerge, and seem to throw luminous bridges +across the central umbra. As a rule the spots are not very profound. +They are funnel-shaped depressions, inferior in depth to the diameter of +the Earth, which, as we have seen, is 108 times smaller than that of the +Sun. + + * * * * * + +The Sun-Spots are not devoid of motion, and from their movements we +learn that the radiant orb revolves upon itself in about twenty-five +days. This rotation was determined in 1611, by Galileo, who, while +observing the spots, saw that they traversed the solar disk from east +to west, following lines that are oblique to the plane of the ecliptic, +and that they disappear at the western border fourteen days after their +arrival at the eastern edge. Sometimes the same spot, after being +invisible for fourteen days, reappears upon the eastern edge, where it +was observed twenty-eight days previously. It progresses toward the +center of the Sun, which is reached in seven days, disappears anew in +the west, and continues its journey on the hemisphere opposed to us, to +reappear under observation two weeks later, if it has not meantime been +extinguished. This observation proves that the Sun revolves upon itself. +The reappearance of the spots occurs in about twenty-seven days, because +the Earth is not stationary, and in its movement round the burning +focus, a motion effected in the same direction as the solar rotation, +the spots are still visible two and a half days after they disappeared +from the point at which they had been twenty-five days previously. In +reality, the rotation of the Sun occupies twenty-five and a half days, +but strangely enough this globe _does not rotate in one uniform period_, +like the Earth; the rotation periods, or movements of the different +parts of the solar surface, diminish from the Sun's equator toward its +poles. The period is twenty-five days at the equator, twenty-six at the +twenty-fourth degree of latitude, north or south, twenty-seven at the +thirty-seventh degree, twenty-eight at the forty-eighth. The spots are +usually formed between the equator and this latitude, more especially +between the tenth and thirtieth degrees. They have never been seen round +the poles. + +Toward the edges of the Sun, again, are very brilliant and highly +luminous regions, which generally surround the spots, and have been +termed _faculæ_ (_facula_, a little torch). These faculæ, which +frequently occupy a very extensive surface, seem to be the seat of +formidable commotions that incessantly revolutionize the face of our +monarch, often, as we said, preceding the spots. They can be detected +right up to the poles. + +Our Sun, that appears so calm and majestic, is in reality the seat of +fierce conflagrations. Volcanic eruptions, the most appalling storms, +the worst cataclysms that sometimes disturb our little world, are gentle +zephyrs compared with the solar tempests that engender clouds of fire +capable at one burst of engulfing globes of the dimensions of our +planet. + +To compare terrestrial volcanoes with solar eruptions is like comparing +the modest night-light that consumes a midge with the flames of the fire +that destroys a town. + +The solar spots vary in a fairly regular period of eleven to twelve +years. In certain years, _e.g._, 1893, they are vast, numerous and +frequent; in other years, _e.g._, 1901, they are few and insignificant. +The statistics are very carefully preserved. Here, for instance, is the +surface showing sun-spots expressed in millionths of the extent of the +visible solar surface: + + 1889 78 + 1890 99 + 1891 569 + 1892 1,214 + 1893 1,464 + 1895 974 + 1896 543 + 1897 514 + 1898 375 + 1899 111 + 1900 75 + 1901 29 + 1902 62 + +The years 1889 and 1901 were _minima_; the year 1893 a _maximum_. + +It is a curious fact that terrestrial magnetism and the boreal auroras +exhibit an oscillation parallel to that of the solar spots, and +apparently the same occurs with regard to temperature. + +We must regard our sun as a globe of gas in a state of combustion, +burning at high temperature, and giving off a prodigious amount of heat +and light. The dazzling surface of this globe is called a _photosphere_ +(light sphere). It is in perpetual motion, like the waves of an ocean of +fire, whose roseate and transparent flames measure some 15,000 +kilometers (9,300 miles) in height. This stratum of rose-colored flames +has received the name of _chromosphere_ (color sphere). It is +transparent; it is not directly visible, but is seen only during the +total eclipses of the Sun, when the dazzling disk of that luminary is +entirely concealed by the Moon; or with the aid of the spectroscope. The +part of the Sun that we see is its luminous surface, or photosphere. + +From this agitated surface there is a constant ejection of gigantic +eruptions, immense jets of flame, geysers of fire, projected at a +terrific speed to prodigious heights. + +For years astronomers were greatly perplexed as to the nature of these +incandescent masses, known as prominences, which shot out like +fireworks, and were only visible during the total eclipses of the Sun. +But now, thanks to an ingenious invention of Janssen and Lockyer, these +eruptions can be observed every day in the spectroscope, and have been +registered since 1868, more particularly in Rome and in Catania, where +the Society of Spectroscopists was founded with this especial object, +and publishes monthly bulletins in statistics of the health of the Sun. + +These prominences assume all imaginable forms, and often resemble our +own storm-clouds; they rise above the chromosphere with incredible +velocity, often exceeding 200 kilometers (124 miles) per second, and +are carried up to the amazing height of 300,000 kilometers (186,000 +miles). + +[Illustration: FIG. 31.--Rose-colored solar flames 228,000 kilometers +(141,500 miles) in height, _i.e._, 18 times the diameter of the Earth.] + +The Sun is surrounded with these enormous flames on every side; +sometimes they shoot out into space like splendid curving roseate +plumes; at others they rear their luminous heads in the Heavens, like +the cleft and waving leaves of giant palm-trees. Having illustrated a +remarkable type of solar spot, it is interesting to submit to the reader +a precise observation of these curious solar flames. That reproduced +here was observed in Rome, January 30, 1885. It measured 228,000 +kilometers (141,500 miles) in height, eighteen times the diameter of the +earth (represented alongside in its relative magnitude). (Fig. 31.) + +Solar eruptions have been seen to reach, in a few minutes, a height of +more than 100,000 kilometers (62,000 miles), and then to fall back in a +flaming torrent into that burning and inextinguishable ocean. + +Observation, in conjunction with spectral analysis, shows these +prominences to be due to formidable explosions produced within the +actual substance of the Sun, and projecting masses of incandescent +hydrogen into space with considerable force. + +Nor is this all. During an eclipse one sees around the black disk of the +Moon as it passes in front of the Sun and intercepts its light, a +brilliant and rosy aureole with long, luminous, branching feathers +streaming out, like aigrettes, which extend a very considerable distance +from the solar surface. This aureole, the nature of which is still +unknown to us, has received the name of _corona_. It is a sort of +immense atmosphere, extremely rarefied. Our superb torch, accordingly, +is a brazier of unparalleled activity--a globe of gas, agitated by +phenomenal tempests whose flaming streamers extend afar. The smallest of +these flames is so potent that it would swallow up our world at a single +breath, like the bombs shot out by Vesuvius, that fall back within the +crater. + +What now is the real heat of this incandescent focus? The most accurate +researches estimate the temperature of the surface of the Sun at +7,000°C. The internal temperature must be considerably higher. A +crucible of molten iron poured out upon the Sun would be as a stream of +ice and snow. + +We can form some idea of this calorific force by making certain +comparisons. Thus, the heat given out appears to be equal to that which +would be emitted by a colossal globe of the same dimensions (that is, as +voluminous as twelve hundred and eighty thousand terrestrial globes), +entirely covered with a layer of incandescent coal 28 kilometers (18 +miles) in depth, all burning at equal combustion. The heat emitted by +the Sun, at each second, is equal to that which would result from the +combustion of eleven quadrillions six hundred thousand milliards of tons +of coal, all burning together. This same heat would bring to the boil in +an hour, two trillions nine hundred milliards of cubic kilometers of +water at freezing-point. + +Our little planet, gravitating at 149,000,000 kilometers (93,000,000 +miles) from the Sun, arrests on the way, and utilizes, only the half of +a milliard part of this total radiation. + +How is this heat maintained? One of the principal causes of the heat of +the Sun is its condensation. According to all probabilities, the solar +globe represents for us the nucleus of a vast nebula, that extended in +primitive times beyond the orbit of Neptune, and which in its +contraction has finally produced this central focus. In virtue of the +law of transformation of motion into heat, this condensation, which has +not yet reached its limit, suffices to raise this colossal globe to its +level of temperature, and to maintain it there for millions of years. In +addition, a substantial number of meteors is forever falling into it. +This furnace is a true pandemonium. + +The Sun weighs three hundred and twenty-four thousand times more than +the Earth--that is to say, eighteen hundred and seventy octillions of +kilograms: + + 1,870,000,000,000,000,000,000,000,000,000 + (1,842,364,532,019,704,433,497,536,945 tons). + +In Chapter XI we shall explain the methods by which it has been found +possible to weigh the Sun and determine its exact distance. + + * * * * * + +I trust these figures will convey some notion of the importance and +nature of the Sun, the stupendous orb on whose rays our very existence +depends. Its apparent dimension (which is only half a degree, 32', and +would be hidden from sight, like that of the full moon, which is about +the same, by the tip of the little finger held out at arm's length), +represents, as we have seen, a real dimension that is colossal, _i.e._, +1,383,000 kilometers (more than 857,000 miles), and this is owing to the +enormous distance that separates us from it. This distance of +149,000,000 kilometers (93,000,000 miles) is sufficiently hard to +appreciate. Let us say that 11,640 terrestrial globes would be required +to throw a bridge from here to the Sun, while 30 would suffice from the +Earth to the Moon. The Moon is 388 times nearer to us than the Sun. We +may perhaps conceive of this distance by calculating that a train, +moving at constant speed of 1 kilometer (0.6214 mile) a minute, would +take 149,000,000 minutes, that is to say 103,472 days, or 283 years, to +cross the distance that separates us from this orb. Given the normal +duration of life, neither the travelers who set out for the Sun, nor +their children, nor their grandchildren, would arrive there: only the +seventh generation would reach the goal, and only the fourteenth could +bring us back news of it. + +Children often cry for the Moon. If one of these inquisitive little +beings could stretch out its arms to touch the Sun, and burn its fingers +there, it would not feel the burn for one hundred and sixty-seven years +(when it would no longer be an infant), for the nervous impulse of +sensation can only be transmitted from the ends of the fingers to the +brain at a velocity of 28 meters per second. + +'Tis long. A cannon-ball would reach the Sun in ten years. Light, that +rapid arrow that flies through space at a velocity of 300,000 kilometers +(186,000 miles per second), takes only eight minutes seventeen seconds +to traverse this distance. + + * * * * * + +This brilliant Sun is not only sovereign of the Earth; he is also the +head of a vast planetary system. + +The orbs that circle round the Sun are opaque bodies, spherical in +shape, receiving their light and heat from the central star, on which +they absolutely depend. The name of planets given to them signifies +"wandering" stars. If you observe the Heavens on a fine starry night, +and are sufficiently acquainted with the principal stars of the Zodiac +as described in a preceding chapter, you may be surprised on certain +evenings to see the figure of some zodiacal constellation slightly +modified by the temporary presence of a brilliant orb perhaps surpassing +in its luminosity the finest stars of the first magnitude. + +If you watch this apparition for some weeks, and examine its position +carefully in regard to the adjacent stars, you will observe that it +changes its position more or less slowly in the Heavens. These wandering +orbs, or _planets_, do not shine with intrinsic light; they are +illuminated by the Sun. + +The planets, in effect, are bodies as opaque as the Earth, traveling +round the God of Day at a speed proportional to their distance. They +number eight principal orbs, and may be divided into two quite distinct +groups by which we may recognize them: the first comprises four planets, +of relatively small dimensions in comparison with those of the second +group, which are so voluminous that the least important of them is +larger than the other four put together. + +In order of distance from the Sun, we first encounter: + + MERCURY, VENUS, THE EARTH, AND MARS + +These are the worlds that are nearest to the orb of day. + +The four following, and much more remote, are, still in order of +distance: + + JUPITER, SATURN, URANUS, AND NEPTUNE + +This second group is separated from the first by a vast space occupied +by quite a little army of minute planets, tiny cosmic bodies, the +largest of which measures little more than 100 kilometers (62 miles) in +diameter, and the smallest some few miles only. + +The planets which form these three groups represent the principal +members of the solar family. But the Sun is a patriarch, and each of his +daughters has her own children who, while obeying the paternal influence +of the fiery orb, are also obedient to the world that governs them. +These secondary asters, or _satellites_, follow the planets in their +course, and revolve round them in an ellipse, just as the others rotate +round the Sun. Every one knows the satellite of the Earth, the Moon. All +the other planets of our system have their own moons, some being even +more favored than ourselves in this respect, and having several. Mars +has two; Jupiter, five; Saturn, eight; Uranus, four; and Neptune, one +(at least as yet discovered). + +In order to realize the relations between these worlds, we must +appreciate their distances by arranging them in a little table: + + Distance in Distance in + Millions of Millions of + Kilometers. Miles. + Mercury 57 35 + Venus 108 67 + The Earth 149 93 + Mars 226 140 + Jupiter 775 481 + Saturn 1,421 882 + Uranus 2,831 1,755 + Neptune 4,470 2,771 + +The Sun is at the center (or, more properly speaking, at the focus, for +the planets describe an ellipse) of this system, and controls them. +Neptune is thirty times farther from the Sun than the Earth. These +disparities of distance produce a vast difference in the periods of the +planetary revolutions; for while the Earth revolves round the Sun in a +year, Venus in 224 days, and Mercury in 88, Mars takes nearly 2 years to +accomplish his journey, Jupiter 12 years, Saturn 29, Uranus 84, and +Neptune 165. + +Even the planets and their moons do not represent the Sun's complete +paternity. There are further, in the solar republic, certain vagabond +and irregular orbs that travel at a speed that is often most immoderate, +occasionally approaching the Sun, not to be consumed therein, but, as it +appears, to draw from its radiant source the provision of forces +necessary for their perigrinations through space. These are the +_Comets_, which pursue an extremely elongated orbit round the Sun, to +which at times they approximate very closely, at other times being +excessively distant. + +And now to recapitulate our knowledge of the Solar Empire. In the first +place, we see a colossal globe of fire dominating and governing the +worlds that belong to him. Around him are grouped planets, in number +eight principal, formed of solid and obscure matter, gravitating round +the central orb. Other secondary orbs, the satellites, revolve round the +planets, which keep them within the sphere of their attraction. And +lastly, the comets, irregular celestial bodies, track the whole extent +of the great solar province. To these might be added the whirlwinds of +meteors, as it were disaggregated comets, which also circle round the +Sun, and give origin to shooting stars, when they come into collision +with the Earth. + +Having now a general idea of our celestial family, and an appreciation +of the potent focus that controls it, let us make direct acquaintance +with the several members of which it is composed. + + + + +CHAPTER V + +THE PLANETS + +_A._--MERCURY, VENUS, THE EARTH, MARS + + +And now we are in the Solar System, at the center, or, better, at the +focus of which burns the immense and dazzling orb. We have appreciated +the grandeur and potency of the solar globe, whose rays spread out in +active waves that bear a fecundating illumination to the worlds that +gravitate round him; we have appreciated the distance that separates the +Sun from the Earth, the third of the planets retained within his domain, +or at least I trust that the comparisons of the times required by +certain moving objects to traverse this distance have enabled us to +conceive it. + +We said that the four planets nearest to the Sun are Mercury, at a +distance of 57 million kilometers (35,000,000 miles); Venus, at 108 +million (67,000,000 miles); the Earth, at 149 million (93,000,000 +miles); and Mars at 226 million (140,000,000 miles). Let us begin our +planetary journey with these four stations. + + +MERCURY + +A little above the Sun one sometimes sees, now in the West, in the +lingering shimmer of the twilight, now in the East, when the tender +roseate dawn announces the advent of a clear day, a small star of the +first magnitude which remains but a very short time above the horizon, +and then plunges back into the flaming sun. This is Mercury, the agile +and active messenger of Olympus, the god of eloquence, of medicine, of +commerce, and of thieves. One only sees him furtively, from time to +time, at the periods of his greatest elongations, either after the +setting or before the rising of the radiant orb, when he presents the +aspect of a somewhat reddish star. + +This planet, like the others, shines only by the reflection of the Sun +whose illumination he receives, and as he is in close juxtaposition with +it, his light is bright enough, though his volume is inconsiderable. He +is smaller than the Earth. His revolution round the Sun being +accomplished in about three months, he passes rapidly, in a month and a +half, from one side to the other of the orb of day, and is alternately a +morning and an evening star. The ancients originally regarded it as two +separate planets; but with attentive observation, they soon perceived +its identity. In our somewhat foggy climates, it can only be discovered +once or twice a year, and then only by looking for it according to the +indications given in the astronomic almanacs. + +[Illustration: FIG. 32.--Orbits of the four Planets nearest to the Sun.] + +Mercury courses round the Sun at a distance of 57,000,000 kilometers +(35,000,000 miles), and accomplishes his revolution in 87 days, 23 +hours, 15 minutes; _i.e._, 2 months, 27 days, 23 hours, or a little less +than three of our months. If the conditions of life are the same there +as here, the existence of the Mercurians must be four times as short as +our own. A youth of twenty, awaking to the promise of the life he is +just beginning in this world, is an octogenarian in Mercury. There the +fair sex would indeed be justified in bewailing the transitory nature of +life, and might regret the years that pass too quickly away. Perhaps, +however, they are more philosophic than with us. + +[Illustration: FIG. 33.--Orbits of the four Planets farthest from the +Sun.] + +The orbit of Mercury, which of course is within that of the Earth, is +not circular, but elliptical, and very eccentric, so elongated that at +certain times of the year this planet is extremely remote from the solar +focus, and receives only half as much heat and light as at the opposite +period; and, in consequence, his distance from the Earth varies +considerably. + +[Illustration: FIG. 34.--Mercury near quadrature.] + +This globe exhibits _phases_, discovered in the seventeenth century by +Galileo, which recall those of the Moon. They are due to the motions of +the planet round the Sun, and are invisible to the unaided eye, but with +even a small instrument, one can follow the gradations and study Mercury +under every aspect. Sometimes, again, he passes exactly in front of the +Sun, and his disk is projected like a black point upon the luminous +surface of the flaming orb. This occurred, notably, on May 10, 1891, and +November 10, 1894; and the phenomenon will recur on November 12, 1907, +and November 6, 1914. + +Mercury is the least of all the worlds in our system (with the exception +of the cosmic fragments that circulate between the orbit of Mars and +that of Jupiter). His volume equals only 5/100 that of the Earth. His +diameter, in comparison with that of our planet, is in the ratio of 373 +to 1,000 (a little more than 1/3) and measures 4,750 kilometers (2,946 +miles). His density is the highest of all the worlds in the great solar +family, and exceeds that of our Earth by about 1/3; but weight there is +less by almost 1/2. + +Mercury is enveloped in a very dense, thick atmosphere, which doubtless +sensibly tempers the solar heat, for the Sun exhibits to the Mercurians +a luminous disk about seven times more extensive than that with which we +are familiar on the Earth, and when Mercury is at perihelion (that is, +nearest to the Sun), his inhabitants receive ten times more light and +heat than we obtain at midsummer. In all probability, it would be +impossible for us to set foot on this planet without being shattered by +a sunstroke. + +Yet we may well imagine that Nature's fecundity can have engendered +beings there of an organization different from our own, adapted to an +existence in the proximity of fire. What magnificent landscapes may +there be adorned with the luxuriant vegetation that develops rapidly +under an ardent and generous sun? + +[Illustration: FIG. 35.--The Earth viewed from Mercury.] + +Observations of Mercury are taken under great difficulties, just because +of the immediate proximity of the solar furnace; yet some have detected +patches that might be seas. In any case, these observations are +contradictory and uncertain. + +Up to the present it has been impossible to determine the duration of +the rotation. Some astronomers even think that the Sun's close proximity +must have produced strong tides, that would, as it were, have +immobilized the globe of Mercury, just as the Earth has immobilized the +Moon, forcing it perpetually to present the same side to the Sun. From +the point of view of habitation, this situation would be somewhat +peculiar; perpetual day upon the illumined half, perpetual night upon +the other hemisphere, and a fairly large zone of twilight between the +two. Such a condition would indeed be different from the succession of +terrestrial days and nights. + +As seen from Mercury, the Earth we inhabit would shine out in the starry +sky[9] as a magnificent orb of first magnitude, with the Moon +alongside, a faithful little companion. They should form a fine double +star, the Earth being a brilliant orb of first magnitude, and the Moon +of third, a charming couple, and admired doubtless as an enchanted and +privileged abode. + +It is at midnight during the oppositions of the Earth with the Sun that +our planet is the most beautiful and brilliant, as is Jupiter for +ourselves. The constellations are the same, viewed from Mercury or from +the Earth. + +But is this little solar planet inhabited? We do not yet know. We can +only reply: why not? + + +VENUS + +When the sunset atmosphere is crimson with the glorious rays of the King +of Orbs, and all Nature assumes the brooding veil of twilight, the most +indifferent eyes are often attracted and captivated by the presence of a +star that is almost dazzling, and illuminates with its white and limpid +light the heavens darkened by the disappearance of the God of Day. + +Hail, Venus, Queen of the Heavens! the "Shepherd's Star," gentle mother +of the loves, goddess of beauty, eternally adored and cherished, sung +and immortalized upon Earth, by poets and artists. Her splendid +brilliancy attracted notice from earliest antiquity, and we find her, +radiant and charming, in the works of the ancients, who erected altars +to her and adorned their poetry with her grace and beauty. Homer calls +her Callisto the Beautiful; Cicero names her Vesper, the evening star, +and Lucifer, the star of the morning--for it was with this divinity as +with Mercury. For a long while she was regarded as two separate planets, +and it was only when it came to be observed that the evening and the +morning star were always in periodic succession, that the identity of +the orb was recognized. + +Her radiant splendor created her mythological personality, just as the +agility of Mercury created that of the messenger of the gods. + +We do not see her aerial chariot in the Heavens drawn by a flight of +doves with white and fluttering wings, but we follow the lustrous orb +led on through space by solar attraction. And in the beautiful evenings +when she is at her greatest distance from our Sun, the whole world +admires this white and dazzling Venus reigning as sovereign over our +twilight[10] for hours after sunset, and in addition to the _savants_ +who are practically occupied with astronomy, millions of eyes are raised +to this celestial splendor, and for a moment millions of human beings +feel some curiosity about the mysteries of the Infinite. The brutalities +of daily life would fain petrify our dreams, but thought is not yet +stifled to the point of checking all aspirations after eternal truth, +and when we gaze at the starry sky it is hard not to ask ourselves the +nature of those other worlds, and the place occupied by our own planet +in the vast concert of sidereal harmony. + +[Illustration: FIG. 36.--The Evening Star.] + +Even through a small telescope, Venus offers remarkable phases. + +[Illustration: FIG. 37.--Successive phases of Venus.] + +Fig. 37 gives some notion of the succession of these, and of the +planet's variations in magnitude during its journey round the Sun. +Imagine it to be rotating in a year of 224 days, 16 hours, 49 minutes, 8 +seconds at a distance of 108 million kilometers (67,000,000 miles), the +Earth being at 149 million kilometers (93,000,000 miles). Like Mercury, +at certain periods it passes between the Sun and ourselves, and as its +illuminated hemisphere is of course turned toward the orb of day, we at +those times perceive only a sharp and very luminous crescent. At such +periods Venus is entirely, so to say, against the Sun, and presents to +us her greatest apparent dimension (Fig. 38). Sometimes, again, like +Mercury, she passes immediately in front of the Sun, forming a perfectly +round black spot; this happened on December 8, 1874, and December 6, +1882; and will recur on June 7, 2004, and June 5, 2012. These transits +have been utilized in celestial geometry in measuring the distance of +the Sun. + +You will readily divine that the distance of Venus varies considerably +according to her position in relation to the Earth: when she is between +the Sun and ourselves she is nearest to our world; but it is just at +those times that we see least of her surface, because she exhibits to us +only a slender crescent. Terrestrial astronomers are accordingly very +badly placed for the study of her physical constitution. The best +observations can be made when she is situated to right or left of the +Sun, and shows us about half her illuminated disk--during the day for +choice, because at night there is too much irradiation from her dazzling +light. + +These phases were discovered by Galileo, in 1610. His observations were +among the first that confirmed the veracity of the system of Copernicus, +affording an evident example of the movement of the planets round the +sun. They are often visible to the unaided eye with good sight, either +at dusk, or through light clouds. + +[Illustration: FIG. 38.--Venus at greatest brilliancy.] + +Venus, surrounded by a highly dense and rarefied atmosphere, which +increases the difficulties of observing her surface, might be called the +twin sister of the Earth, so similar are the dimensions of the two +worlds. But, strange as it may seem to the many admirers, who are ready +to hail in her an abode of joy and happiness, it is most probable that +this planet, attractive as she is at a distance, would be a less +desirable habitation than our floating island. In fact, the atmosphere +of Venus is perpetually covered with cloud, so that the weather there +must be always foggy. No definite geographical configuration can be +discovered on her, despite the hopes of the eighteenth-century +astronomers. We are not even sure that she rotates upon herself, so +contradictory are the observations, and so hard is it to distinguish +anything clearly upon her surface. A single night of observation +suffices to show the rotation of Mars or of Jupiter; but the beautiful +Evening Star remains obstinately veiled from our curiosity. + +Several astronomers, and not the least considerable, think that the +tides produced by the Sun upon her seas, or globe in its state of +pristine fluidity, must have been strong enough to seize and fix her, as +the Earth did for the Moon, thus obliging her to present always the same +face to the Sun. Certain telescopic observations would even seem to +confirm this theoretical deduction from the calculations of celestial +mechanics. + +The author ventures to disagree with this opinion, its apparent +probability notwithstanding, because he has invariably received a +contrary impression from all his telescopic observations. He has quite +recently (spring of 1903) repeated these observations. Choosing a +remarkably clear and perfectly calm atmosphere, he examined the splendid +planet several times with great attention in the field of the telescope. +The right or eastern border (reversed image) was dulled by the +atmosphere of Venus; this is the line of separation between day and +night. Beneath, at the extreme northern edge, he was attracted on each +occasion by a small white patch, a little whiter than the rest of the +surface of the planet, surrounded by a light-gray penumbra, giving the +exact effect of a polar snow, very analogous to that observed at the +poles of Mars. To the author this white spot on the boreal horn of +Venus does not appear to be due to an effect of contrast, as has +sometimes been supposed. + +Now, if the globe of Venus has poles, it must turn upon itself. + +Unfortunately it has proved impossible to distinguish any sign upon the +disk, indicative of the direction and speed of its rotary movement, +although these observations were made, with others, under excellent +conditions.--Three o'clock in the afternoon, brilliant sun, sky clear +blue, the planet but little removed from the meridian--at which time it +is less dazzling than in the evening. + +There is merely the impression; but it is so definite as to prevent the +author from adopting the new hypothesis, in virtue of which the planet, +as it gravitates round the Sun, presents always the same hemisphere. + +If this hypothesis were a reality, Venus would certainly be a very +peculiar world. Eternal day on the one side; eternal night on the other. +Maximum light and heat at the center of the hemisphere perpetually +turned to the Sun; maximum cold and center of night at the antipodes. +This icy hemisphere would possibly be uninhabitable, but the resources +of Nature are so prodigious, and the law of Life is so imperious, so +persistent, under the most disadvantageous and deplorable terrestrial +conditions, that it would be transcending our rights to declare an +impossibility of existence, even in this eternal night. The currents of +the atmosphere would no doubt suffice to set up perpetual changes of +temperature between the two hemispheres, in comparison with which our +trade-winds would be the lightest of breezes. + +Yes, mystery still reigns upon this adjacent earth, and the most +powerful instruments of the observatories of the whole world have been +unable to solve it. All we know is that the diameter, surface, volume +and mass of this planet, and its weight at the surface, do not differ +sensibly from those that characterize our own globe: that this planet is +sister to our own, and of the same order, hence probably formed of the +same elements. We further know that, as seen from Venus (Fig. 39), the +Earth on which we live is a magnificent star, a double orb more +brilliant even than when viewed from Mercury. It is a dazzling orb of +first magnitude, accompanied by its moon, a star of the second and a +half magnitude. + +And thus the worlds float on in space, distant symbols of hopes not +realized on any one of them, all at different stages of their degree of +evolution, representing an ever-growing progress in the sequence of the +ages. + +[Illustration: FIG. 39.--The Earth viewed from Venus.] + +When we contemplate this radiant Venus, it is difficult, even if we can +not form any definite idea as to her actual state as regards habitation, +to assume that she must be a dreary desert, and not, on the contrary, +to hail in her a celestial land, differing more or less from our own +dwelling-place, travailing with her sisters in the accomplishment of the +general plan of Nature. + +Such are the characteristic features of our celestial neighbor. In +quitting her, we reach the Earth, which comes immediately next her in +order of distance, 149 million kilometers (93,000,000 miles) from the +Sun, but as we shall devote an entire chapter to our own planet, we will +not halt at this point, but cross in one step the distance that +separates Mars from Venus. + +Let us only remark in passing, that our planet is the largest of the +four spheres adjacent to the Sun. Here are their comparative diameters: + + The Earth = 1. In Kilometers. In Miles. + Mercury 0.373 4,750 2,946 + Venus 0.999 12,730 7,894 + Earth 1.000 12,742 7,926 + Mars 0.528 6,728 4,172 + +It will be seen that Venus is almost identical with the Earth. + + +MARS + +Two hundred and twenty-six millions of kilometers (140,000,000 miles) +from the Sun is the planet Mars, gravitating in an orbit exterior to +that which the Earth takes annually round the same center. + +Unfortunate Mars! What evil fairy presided at his birth? From +antiquity, all curses seem to have fallen upon him. He is the god of war +and of carnage, the protector of armies, the inspirer of hatred among +the peoples, it is he who pours out the blood of Humanity in +international hecatombs. Here, again, as in the case of Mercury and +Venus, the appearance has originated the idea. Mars, in fact, burns like +a drop of blood in the depths of the firmament, and it is this ruddy +color that inspired its name and attributes, just as the dazzling +whiteness of Venus made her the goddess of love and beauty. Why, indeed, +should the origins of mythology be sought elsewhere than in astronomy? + +While Humanity was attributing to the presumptive influence of Mars the +defects inherent in its own terrestrial nature, this world, unwitting of +our sorrows, pursued the celestial path marked out for it in space by +destiny. + +This planet is, as we have said, the first encountered after the Earth. +Its orbit is very elongated, very eccentric. Mars accomplishes it in a +period of 1 year, 321 days, 22 hours, _i.e._, 1 year, 10 months, 21 +days, or 687 days. The velocity of its transit is 23 kilometers (14.5 +miles) per second; that of the Earth is 30 (19 miles). Our planet, +traveling through space at an average distance of 149 million kilometers +(93,000,000 miles) from the central focus, is separated from Mars by an +average distance of 76 million kilometers (47,000,000 miles); but as its +orbit is equally elliptic and elongated it follows that at certain +epochs the two planets approach one another by something less than 60 +million kilometers (37,000,000 miles). These are the periods selected +for making the best observations upon our neighbor of the ruddy rays. +The oppositions of Mars arrive about every twenty-six months, but the +periods of its greatest proximity, when this planet approaches to within +56 million kilometers (34,700,000 miles) of the Earth, occur only every +fifteen years. + +Mars is then passing perihelion, while our world is at aphelion (or +greatest distance from the Sun). At such epochs this globe presents to +us an apparent diameter 63 times smaller than that of the Moon, _i.e._, +a telescope that magnifies 63 times would show him to us of the same +magnitude as our satellite viewed with the unaided eye, and an +instrument that magnified 630 times would show him ten times larger in +diameter. + +In dimensions he differs considerably from our world, being almost half +the size of the Earth. In diameter he measures only 6,728 kilometers +(4,172 miles), and his circumference is 21,125 kilometers (13,000 +miles). His surface is only 29/100 of the terrestrial surface, and his +volume only 15/100 of our own. + +This difference in volume causes Mars to be an earth in miniature. When +we study his aspects, his geography, his meteorology, we seem to see in +space a reduction of our own abode, with certain dissimilarities that +excite our curiosity, and make him even more interesting to us. + +The Martian world weighs nine times and a half less than our own. If we +represent the weight of the Earth by 1,000, that of Mars would be +represented by 105. His density is much less than our own; it is only +7/10 that of the Earth. A man weighing 70 kilograms, transported to the +adjacent globe, would weigh only 26 kilograms. + +The earliest telescopic observations revealed the existence of more or +less accentuated markings upon the surface of Mars. The progress of +optics, admitting of greater magnifications, exhibited the form of these +patches more clearly, while the study of their motions enabled the +astronomers to determine with remarkable precision the diurnal rotation +of this planet. It occurs in 24 hours, 37 minutes, 23.65 seconds. Day +and night are accordingly a little longer on Mars than on the Earth, but +the difference is obviously inconsiderable. The year of Mars consists of +668 Martian days. The inclination of the axis of rotation of this globe +upon the plane of its orbit is much the same as our own. In +consequence, its seasons are analogous to ours in intensity, while twice +the length, the Martian year being almost equal to two of our years. The +intensity of the seasons is indeed more accentuated than upon the Earth, +since the orbit of Mars is very elongated. But there, as here, are three +quite distinct zones: the torrid, the temperate, and the glacial. + +By means of the telescope we can follow the variations of the Martian +seasons, especially in what concerns the polar snows, which regularly +aggregate during the winter, and melt no less regularly during the heat +of the summer. These snows are very easily observed, and stand out +clearly with dazzling whiteness. The reader can judge of them by the +accompanying figure, which sums up the author's observations during one +of the recent oppositions of Mars (1900-1901). The size of the polar cap +diminished from 4,680 kilometers to 840. The solstice of the Martian +summer was on April 11th. The snows were still melting on July 6th. +Sometimes they disappear almost entirely during the Martian month that +corresponds to our month of August, as never happens with our polar ice. +Hence, though this planet is farther away from the Sun than ourselves, +it does not appear to be colder, or, at any rate, it is certain that the +polar snows are much less thick. + +On the other hand, there are hardly ever clouds on Mars; the Martian +atmosphere is almost always limpid, and one can say that fine weather is +the chronic state of the planet. At times, light fogs or a little vapor +will appear in certain regions, but they are soon dissipated, and the +sky clears up again. + +[Illustration: FIG. 40.--Diminution of the polar snows of Mars during +the summer.] + +Since the invention of the telescope, a considerable number of drawings +have been made, depicting Mars under every aspect, and the agreement +between these numerous observations gives us a sufficient acquaintance +with the planet to admit of our indicating the characteristic features +of its geography, and of drawing out _areographic_ maps (_Ares_, Mars). +Its appearance can be judged of from the two drawings here reproduced, +as made (February, 1901) at the Observatory of Juvisy, and from the +general chart drawn from the total sum of observations (Figs. 41, 42 and +43). + +It will be seen at the first glance that the geography of Mars is very +different from that of our own globe: while three-quarters of the Earth +are covered with the liquid element, Mars seems to be more evenly +divided, and must indeed have rather more land than water. We find no +immense oceans surrounding the continents, and separating them like +islands; on the contrary, the seas are reduced to long gulfs compressed +between the shores, like the Mediterranean for example, nor is it even +certain that these gray spots do all represent true seas. It has been +agreed to term _sea_ the parts that are lightly tinged with green, and +to give the name of _continent_ to the spots colored yellow. That is the +hue of the Martian soil, due either to the soil itself, which would +resemble that of the Sahara, or, to take a less arid region, that seen +on the line between Marseilles and Nice, in the vicinity of the +Esterels; or perhaps to some peculiar vegetation. During ascents in a +balloon, the author has often remarked that the hue of the ripe corn, +with the Sun shining on it, is precisely that presented to us by the +continents of Mars in the best hours for observation. + +[Illustration: FIG. 41.--Telescopic aspect of the planet Mars (Feb., +1901).] + +As to the "seas," it is pretty certain that there must be water, or +some kind of liquid, deriving above all from the melting of the polar +snows in spring and summer; but it may possibly be in conjunction with +some vegetation, aquatic plants, or perhaps vast meadows, which appear +to us from here to be the more considerable in proportion as the water +that nourishes them has been more abundant. + +[Illustration: FIG. 42.--Telescopic aspect of the planet Mars (Feb., +1901).] + +Mars, like our globe, is surrounded with a protective atmosphere, which +retains the rays of the Sun, and must preserve a medium temperature +favorable to the conservation of life upon the surface of the planet. +But the circulation of the water, so important to terrestrial life, +whether animal or vegetable, which is effected upon our planet by the +evaporation of the seas, clouds, winds, rains, wells, rivers and +streams, comes about quite differently on Mars; for, as was remarked +above, it is rarely that any clouds are observed there. Instead of being +vertical, as here, this circulation is horizontal: the water coming from +the source of the polar snows finds its way into the canals and seas, +and returns to be condensed at the poles by a light drift of invisible +vapors directed from the equator to the poles. There is never any rain. + +We have spoken of _canals_. One of the great puzzles of the Martian +world is incontestably the appearance of straight lines that furrow its +surface in all directions, and seem to connect the seas. M. +Schiaparelli, the distinguished Director of the Observatory of Milan, +who discovered them in 1877, called them canals, without, however, +postulating anything as to their real nature. Are they indeed canals? +These straight lines, measuring sometimes 600 kilometers (372 miles) in +length, and more than 100 kilometers (62 miles) in breadth, have much +the same hue as the seas on which they open. For a quarter of a century +they have been surveyed by the greater number of our observers. But it +must be confessed that, even with the best instruments, we only approach +Mars at a distance of 60,000 kilometers (37,200 miles), which is still a +little far off, and we may be sure that we do not distinguish the true +details of the surface.[11] These details at the limits of visibility +produce the appearance of canals to our eyes. They may possibly be lines +of lakes, or oases. The future will no doubt clear up this mystery for +us. + +[Illustration: FIG. 43.--Chart of Mars.] + +As to the inhabitants of Mars, this world is in a situation as +favorable as our Earth for habitation, and it would be difficult to +discover any reason for perpetual sterility there. It appears to us, on +the contrary, by its rapid and frequent variations of aspect, to be a +very living world. Its atmosphere, which is always clear, has not the +density of our own, and resembles that of the highest mountains. The +conditions of existence there vary from ours, and appear to be more +delicate, more ethereal. + +There as here, day succeeds to night, spring softens the rigors of +winter; the seasons unfold, less disparate than our own, of which we +have such frequent reason to complain. The sky is perpetually clear. +There are never tempests, hurricanes, nor cyclones, the wind never gets +up any force there, on account of the rarity of the atmosphere, and the +low intensity of weight. + +Differing from ours, this world may well be a more congenial +habitation. It is more ancient than the Earth, smaller, less massive. It +has run more quickly through the phases of its evolution. Its astral +life is more advanced, and its Humanity should be superior to our own, +just as our successors a million years hence, for example, will be less +coarse and barbarous than we are at present: the law of progress governs +all the worlds, and, moreover, the physical constitution of the planet +Mars is less dense than our own. + +There is no need to despair of entering some day into communication with +these unknown beings. The luminous points that have been observed are no +signals, but high summits or light clouds illuminated by the rising or +setting sun. But the idea of communication with them in the future is no +more audacious and no less scientific than the invention of spectral +analysis, X-rays, or wireless telegraphy. + +We may suppose that the study of astronomy is further advanced in Mars +than on the Earth, because humanity itself has advanced further, and +because the starry sky is far finer there, far easier to study, owing to +the limpidity of its pure, clear atmosphere. + +Two small moons (hardly larger than the city of Paris) revolve rapidly +round Mars; they are called Phobos and Deimos. The former, at a distance +of 6,000 kilometers (3,730 miles) from the surface, accomplishes its +revolution rapidly, in seven hours, thirty-nine minutes, and thus makes +the entire circle of the Heavens three times a day. The second +gravitates at 20,000 kilometers (12,400 miles), and turns round its +center of attraction in thirty hours and eighteen minutes. These two +satellites were discovered by Mr. Hall, at the University of Washington, +in the month of August, 1877. + + * * * * * + +Among the finest and most interesting of the celestial phenomena admired +by the Martians, at certain epochs of the year,--now at night when the +Sun has plunged into his fiery bed, now in the morning, a little before +the aurora,--is a magnificent star of first magnitude, never far removed +from the orb of day, which presents to them the same aspects as does +Venus to ourselves. This splendid orb, which has doubtless received the +most flattering names from those who contemplate it, this radiant star +of a beautiful greenish blue, courses in space accompanied by a little +satellite, sparkling like some splendid diamond, after sunset, in the +clear sky of Mars. This superb orb is the Earth, and the little star +accompanying it is the Moon. + +[Illustration: FIG. 44.--The Earth viewed from Mars.] + +Yes, to the Martians our Earth is a star of the morning and evening; +doubtless they have determined her phases. Many a vow, and many a hope +must have been wafted toward her, more than one broken heart must have +permitted its unrealized dreams to wander forth to our planet as to an +abode of happiness where all who have suffered in their native world +might find a haven. But our planet, alas! is not as perfect as they +imagine. + +We must not dally upon Mars, but hasten our celestial excursion toward +Jupiter. + + + + +CHAPTER VI + +THE PLANETS + +_B._--JUPITER, SATURN, URANUS, NEPTUNE. + + +Before we attack the giant world of our system, we must halt for a few +moments upon the minor planets which circulate between the orbit of Mars +and that of Jupiter. These minute asters, little worlds, the largest of +which measures scarcely more than 100 kilometers (62 miles) in diameter, +are fragments of cosmic matter that once belonged to a vast ring, formed +at the time when the solar system was only an immense nebula; and which, +instead of condensing into a single globe coursing between Mars and +Jupiter, split up into a considerable quantity of particles constituting +at the present time the curious and highly interesting Republic of the +Asteroids. + +These lilliputian worlds at first received the names of the more +celebrated of the minor mythological divinities--Ceres, Pallas, Juno, +Vesta, etc., but as they rapidly increased in number, it was found +necessary to call them by modern, terrestrial names, and more than one +daughter of Eve, the Egeria of some astronomer, now has her name +inscribed in the Heavens. The first minor planet was discovered on the +first day of the nineteenth century, January 1, 1801, by Piazzi, +astronomer at Palermo. While he was observing the small stars in the +constellation of the Bull beneath the clear Sicilian skies, this famous +astronomer noticed one that he had never seen before. + +The next night, directing his telescope to the same part of the Heavens, +he perceived that the fair unknown had moved her station, and the +observations of the following days left him no doubt as to the nature of +the visitor: she was a planet, a wandering star among the +constellations, revolving round the Sun. This newcomer was registered +under the name of Ceres. + +Since that epoch several hundreds of them have been discovered, +occupying a zone that extends over a space of more than 400 million +kilometers (249,000,000 miles). These celestial globules are invisible +to the naked eye, but no year passes without new and numerous recruits +being added to the already important catalogue of these minute asters by +the patient observers of the Heavens. To-day, they are most frequently +discovered by the photographic method of following the displacement of +the tiny moving points upon an exposed sensitive plate. + + +JUPITER + +And now let us bow respectfully before Jupiter, the giant of the worlds. +This glorious planet is indeed King of the Solar System. + +While Mercury measures only 4,750 kilometers (2,946 miles) in diameter, +and Mars 6,728 kilometers (4,172), Jupiter is no less than 140,920 +kilometers (87,400 miles) in breadth; that is to say, eleven times +larger than the Earth. He is 442,500 kilometers (274,357 miles) in +circumference. + +In volume he is equivalent to 1,279 terrestrial globes; hence he is only +a million times smaller than the Sun. The previously described planets +of our system, Mercury, Venus, the Earth, and Mars combined, would form +only an insignificant mass in comparison with this colossus. A hundred +and twenty-six Earths joined into one group would present a surface +whose extent would still not be quite as vast as the superficies of this +titanic world. This immense globe weighs 310 times more than that which +we inhabit. Its density is only the quarter of our own; but weight is +twice and a half times as great there as here. The constituents of +things and beings are thus composed of materials lighter than those upon +the Earth; but, as the planet exerts a force of attraction twice and a +half times as powerful, they are in reality heavier and weigh more. A +graceful maiden weighing fifty kilograms would if transported to Jupiter +immediately be included in the imposing society of the "Hundred Kilos." + +Jupiter rotates upon himself with prodigious rapidity. He accomplishes +his diurnal revolution in less than ten hours! There the day lasts half +as long as here, and while we reckoned fifteen days upon our calendar, +the Jovian would count thirty-six. As Jupiter's year equals nearly +twelve of ours, the almanac of that planet would contain 10,455 days! +Obviously, our pretty little pocket calendars would never serve to +enumerate all the dates in this vast world. + +This splendid globe courses in space at a distance of 775,000,000 +kilometers (480,500,000 miles) from the Sun. Hence it is five times +(5.2) as remote from the orb of day as our Earth, and its orbit is five +times vaster than our own. At that distance the Sun subtends a diameter +five times smaller than that which we see, and its surface is +twenty-seven times less extensive; accordingly this planetary abode +receives on an average twenty-seven times less light and heat than we +obtain. + +In the telescope Jupiter presents an aspect analogous to that likely to +be exhibited by a world covered with clouds, and enveloped in dense +vapors (Fig. 45). + +It is, in fact, the seat of formidable perturbations, of strange +revolutions by which it is perpetually convulsed, for although of more +ancient formation than the Earth, this celestial giant has not yet +arrived at the stable condition of our dwelling-place. Owing to its +considerable volume, this globe has probably preserved its original +heat, revolving in space as an obscure Sun, but perhaps still burning. +In it we see what our own planet must have been in its primordial epoch, +in the pristine times of terrestrial genesis. + +[Illustration: FIG. 45.--Telescopic aspect of Jupiter.] + +Since its orbital revolution occupies nearly twelve years, Jupiter +comes back into opposition with the Sun every 399 days, _i.e._, 1 year, +34 days, that is with one month and four days' delay each year. At these +periods it is located at the extremity of a straight line which, passing +by the Earth, is prolonged to the Sun. These are the epochs to be +selected for observation. It shines then, all night, like some dazzling +star of the first magnitude, of excessive whiteness: nor can it be +confounded either with Venus, more luminous still (for she is never +visible at midnight, in the full South, but is South-west in the +evening, or South-east in the morning), nor with Mars, whose fires are +ruddy. + +In the telescope, the immense planet presents a superb disk that an +enlargement of forty times shows us to be the same size to all +appearance as that of the Moon seen with the unaided eye. Its shape is +not absolutely spherical, but spheroid--that is, flattened at the poles. +The flattening is 1/17. + +We know that the Earth's axis dips a certain quantity on the plane of +her orbit, and that it is this inclination that produces the seasons. +Now it is not the same for Jupiter. His axis of rotation remains almost +vertical throughout the course of his year, and results in the complete +absence of climates and seasons. There is neither glacial zone, nor +tropic zone; the position of Jupiter is eternally that of the Earth at +the season of the equinox, and the vast world enjoys, as it were, +perpetual spring. It knows neither the hoar-frost nor the snows of +winter. The heat received from the Sun diminishes gradually from the +equator to the poles without abrupt transitions, and the duration of day +and night is equal there throughout the entire year, under every +latitude. A privileged world, indeed! + +It is surrounded by a very dense, thick atmosphere, which undergoes more +extensive variations than could be produced by the Sun at such a +distance. Spectral analysis detects a large amount of water-vapor, +showing that this planet still possesses a very considerable quantity of +intrinsic heat. + +Most conspicuous upon this globe are the larger or smaller bands or +markings (gray and white, sometimes tinted yellow, or of a maroon or +chocolate hue) by which its surface is streaked, particularly in the +vicinity of the equator. These different belts vary, and are constantly +modified, either in form or color. Sometimes, they are irregular, and +cut up; at others they are interspersed with more or less brilliant +patches. These patches are not affixed to the surface of the globe, like +the seas and continents of the Earth; nor do they circulate round the +planet like the satellites, in more or less elongated and regular +revolutions, but are relatively mobile, like our clouds in the +atmosphere, while observation of their motion does not give the exact +period of the rotation of Jupiter. Some only appear upon the agitated +disk to vanish very quickly; others subsist for a considerable period. + +One has been observed for over a quarter of a century, and appears to be +almost immobile upon this colossal globe. This spot, which was red at +its first appearance, is now pale and ghostly. It is oval (_vide_ Fig. +45) and measures 42,000 kilometers (26,040 miles) in length by 15,000 +kilometers (9,300 miles) in width. Hence it is about four times as long +as the diameter of our Earth; that is, relatively to the size of +Jupiter, as are the dimensions of Australia in proportion to our globe. +The discussion of a larger number of observations leads us to see in it +a sort of continent in the making, a scoria recently ejected from the +mobile and still liquid and heated surface of the giant Jupiter. The +patch, however, oscillates perceptibly, and appears to be a floating +island. + +We must add that this vast world, like the Sun, _does not rotate all in +one period_. Eight different currents can be perceived upon its surface. +The most rapid is that of the equatorial zone, which accomplishes its +revolution in 9 hours, 50 minutes, 29 seconds. A point situated on the +equator is therefore carried forward at a speed of 12,500 meters (7 +miles) per second, and it is this giddy velocity of Jupiter that has +produced the flattening of the poles. From the equator to the poles, the +swiftness of the currents diminishes irregularly, and the difference +amounts to about five minutes between the movement of the equatorial +stream, and that of the northern and southern currents. But what is more +curious still is that the velocity of one and the same stream is subject +to certain fluctuations; thus, in the last quarter of a century, the +speed of the equatorial current has progressively diminished. In 1879, +the velocity was 9 hours, 49 minutes, 59 seconds, and now it is, as we +have already seen, 9 hours, 50 minutes, 29 seconds, which represents a +substantial reduction. The rotation of the red patch, at 25 degrees of +the southern latitude, is effected in 9 hours, 55 minutes, 40 seconds. + +We are confronted with a strange and mysterious world. It is the world +of the future. + +This giant gravitates in space accompanied by a suite of five +satellites. These are: + + Names. Distance from surface of Jupiter. Time of revolution. + Kilometers. Miles. Days. Hours. + 5. 200,000 124,000 11 + 1. Io 430,000 266,000 1 18 + 2. Europa 682,000 422,840 3 13 + 3. Ganymede 1,088,000 674,560 7 4 + 4. Callisto 1,914,000 1,186,680 16 16 + +The four principal satellites of Jupiter were discovered at the same +time, on the same evenings (January 7 and 8, 1610), by the two +astronomers who were pointing their telescopes at Jupiter: Galileo in +Italy, and Simon Marius in Germany. + +On September 9, 1892, Mr. Barnard, astronomer of the Lick Observatory, +California, discovered a new satellite, extremely minute, and very near +the enormous planet. It has so far received no name, and is known as the +fifth, although the four principal are numbered in the order of their +distances. + +[Illustration: FIG. 46.--Jupiter and his four principal satellites.] + +The four classical satellites are visible in the smallest instruments +(Fig. 46): the third is the most voluminous. + +Such is the splendid system of the mighty Jupiter. Once, doubtless, this +fine planet illuminated the troop of worlds that derived their treasure +of vitality from him with his intrinsic light: to-day, however, these +moons in their turn shed upon the extinct central globe the pale soft +light which they receive from our solar focus, illuminating the brief +Jovian nights (which last less than five hours, on account of the +twilight) with their variable brilliancy. + +At the distance of the first satellite, Jupiter exhibits a disk +_fourteen hundred times_ vaster than that of the Full Moon! What a +dazzling spectacle, what a fairy scene must the enormous star afford to +the inhabitants of that tiny world! And what a shabby figure must our +Earth and Moon present in the face of such a body, a real miniature of +the great solar system! + +Our ancestors were well inspired when they attributed the sovereignty of +Olympus to this majestic planet. His brilliancy corresponds with his +real grandeur. His dominion in the midnight Heavens is unique. Here +again, as for Venus, Mars, and Mercury, astronomy has created the legend +of the fables of mythology. + +Let us repeat in conclusion that our Earth becomes practically invisible +for the inhabitants of the other worlds beyond the distance of Jupiter. + + +SATURN + +Turn back now for a moment to the plan of the Solar System. + +We had to cross 775 million kilometers (480,000,000 miles) when we left +the Sun, in order to reach the immense orb of Jupiter, which courses in +space at 626 million kilometers (388,000,000 miles) from the terrestrial +orbit. From Jupiter we had to traverse a distance of 646 million +kilometers (400,000,000 miles) in order to reach the marvelous system of +Saturn, where our eyes and thoughts must next alight. + +Son of Uranus and Vesta, Saturn was the God of Time and Fate. He is +generally represented as an aged man bearing a scythe. His mythological +character is only the expression of his celestial aspect, as we have +seen for the brilliant Jupiter, for the pale Venus, the ruddy Mars, and +the agile Mercury. The revolution of Saturn is the slowest of any among +the planets known to the ancients. It takes almost thirty years for its +accomplishment, and at that distance the Saturnian world, though it +still shines with the brilliancy of a star of the first magnitude, +exhibits to our eyes a pale and leaden hue. Here is, indeed, the god of +Time, with slow and almost funereal gait. + +Poor Saturn won no favor with the poets and astrologers. He bore the +horrid reputation of being the inexhaustible source of misfortune and +evil fates,--whereof he is wholly innocent, troubling himself not at all +with our world nor its inhabitants. + +This world travels in the vastness of the Heavens at a distance of 1,421 +million kilometers (881,000,000 miles) from the Sun. Hence it is ten +times farther from the orb of day than the Earth, though still +illuminated and governed by the Sun-God. Its gigantic orbit is ten times +larger than our own. + +Its revolution round the Sun is accomplished in 10,759 days, _i.e._, 29 +years, 167 days, and as this strange planet rotates upon itself with +great rapidity in 10 hours, 15 minutes, its year comprises no less than +25,217 days. What a calendar! The Saturnians must needs have a +prodigious memory not to get hopelessly involved in this interminable +number of days. A curious world, where each year stands for almost +thirty of our own, and where the day is more than half as short again as +ours. But we shall presently find other and more extraordinary +differences on this planet. + +In the first place it is nearly nine and a half times larger than our +world. It is a globe, not spherical, but spheroidal, and the flattening +of its poles, which is one-tenth, exceeds that of all the other planets, +even Jupiter. It follows that its equatorial diameter is 112,500 +kilometers (69,750 miles), while its polar diameter measures only +110,000 kilometers (68,200). + +In volume, Saturn is 719 times larger than the Earth, but its density is +only 128/1000 of our own; _i.e._, the materials of which it is composed +are much less heavy, so that it weighs only 92 times more than our +Earth. Its surface is 85 times vaster than that of the Earth, no +insignificant proportion. + +[Illustration: FIG. 47.--Saturn.] + +The dipping of Saturn's axis of rotation is much the same as our own. +Hence we conclude that the seasons of this planet are analogous to ours +in relative intensity. Only upon this far-off world each season lasts +for seven years. At the distance at which it gravitates in space, the +heat and light which it receives from the Sun are 90 times less active +than such as reach our selves; but it apparently possesses an atmosphere +of great density, which may be constituted so that the heat is +preserved, and the planet maintained in a calorific condition but little +inferior to our own. + +In the telescope, the disk of Saturn exhibits large belts that recall +those of Jupiter, though they are broader and less accentuated (Fig. +47). There are doubtless zones of clouds or rapid currents circulating +in the atmosphere. Spots are also visible whose displacement assists in +calculating the diurnal motions of this globe. + +The most extraordinary characteristic of this strange world is, however, +the existence of a vast _ring_, which is almost flat and very large, and +entirely envelops the body of the planet. It is suspended in the +Saturnian sky, like a gigantic triumphal arch, at a height of some +20,000 kilometers (12,400 miles) above the equator. This splendid arch +is circular, like an immense crown illuminated by the Sun. From here we +only see it obliquely, and it appears to us elliptical; a part of the +ring seems to pass in front of Saturn, and its shadow is visible on the +planet, while the opposite part passes behind. + +This ring, which measures 284,000 kilometers (176,080 miles) in +diameter, and less than 100 kilometers (62 miles) in breadth, is divided +into three distinct zones: the exterior is less luminous than the +center, which is always brighter than the planet itself; the interior is +very dark, and spreads out like a dusky and faintly transparent veil, +through which Saturn can be distinguished. + +What is the nature of these vast concentric circles that surround the +planet with a luminous halo? They are composed of an innumerable number +of particles, of a quantity of cosmic fragments, which are swept off in +a rapid revolution, and gravitate round the planet at variable speed and +distance. The nearer particles must accomplish their revolution in 5 +hours, 50 minutes, and the most distant in about 12 hours, 5 minutes, to +prevent them from being merged in the surface of Saturn: their own +centrifugal force sustains them in space. + +[Illustration: FIG. 48. Varying perspective of Saturn's Rings, as seen +from the Earth.] + +With a good glass the effect of these rings is most striking, and one +can not refrain from emotion on contemplating this marvel, whereby one +of the brothers of our terrestrial country is crowned with a golden +diadem. Its aspects vary with its perspective relative to the Earth, as +may be seen from the subjoined figure (Fig. 48). + +We must not quit the Saturnian province without mentioning the eight +satellites that form his splendid suite: + + Names. Distance from the planet. Time of revolution. + Kilometers. Miles. Days. Hours. Minutes. + 1. Mimas 207,000 128,340 22 37 + 2. Enceladus 257,600 159,712 1 8 53 + 3. Tethys 328,800 203,856 1 21 18 + 4. Dione 421,200 261,144 2 17 41 + 5. Rhea 588,400 364,808 4 12 25 + 6. Titan 1,364,000 845,680 15 22 41 + 7. Hyperion 1,650,000 1,023,000 21 6 39 + 8. Japhet 3,964,000 2,457,680 79 7 54 + +Here is a marvelous system, with, what is more, eight different kinds of +months for the inhabitants of Saturn; eight moons with constantly +varying phases juggling above the rings! + +Now we shall cross at a bound the 1,400 million kilometers (868,000,000 +miles) that separate us from the last station but one of the immense +solar system. + + +URANUS + +On March 13, 1781, William Herschel, a Hanoverian astronomer who had +emigrated to England, having abandoned the study of music to devote +himself to the sublime science of the Heavens, was observing the vast +fields with their constellations of golden stars, when he perceived a +luminous point that appeared to him to exceed that of the other +celestial luminaries in diameter. He replaced the magnification of his +telescope by more powerful eye-pieces, and found that the apparent +diameter of the orb increased proportionately with the amplification of +the power, which does not happen in the case of stars at infinite +distance. His observations on the following evenings enabled him to note +the slow and imperceptible movement of this star upon the celestial +sphere, and left him in no further doubt: there was no star, but some +much nearer orb, in all probability a comet, for the great astronomer +dared not predict the discovery of a new planet. And it was thus, under +the name of cometary orb, that the seventh child of the Sun was +announced. The astronomers sought to determine the motions of the new +arrival, to discover for it an elliptical orbit such as most comets +have. But their efforts were vain, and after several months' study the +conclusion was reached that here was a new planet, throwing back the +limits of the solar system to a point far beyond that of the Saturnian +frontier, as admitted from antiquity. + +This new world received the name of Uranus, father of Saturn, his +nearest neighbor in the solar empire. Uranus shines in the firmament as +a small star of sixth magnitude, invisible to the unaided eye for +normal sight, at a distance of 2,831,000,000 kilometers (1,755,000,000 +miles) from the Sun. Smaller than Jupiter and Saturn, this planet is yet +larger than Mercury, Venus, Mars, and the Earth together, thus +presenting proportions that claim our respect and admiration. + +His diameter may be taken at about 55,000 kilometers (34,200 miles), +that is, rather more than four times the breadth of the terrestrial +diameter. Sixty-nine times more voluminous than the Earth, and seventeen +times more extensive in surface, this new world is much less than our +own in density. The matter of which it is composed is nearly five times +lighter than that of our globe. + +Spectral analysis shows that this distant planet is surrounded with an +atmosphere very different from that which we breathe, enclosing gases +that do not exist in ours. + +The Uranian globe courses over the fields of infinity in a vast orbit +seventeen times larger than our own, and its revolution lasts 36,688 +days, _i.e._, 84 years, 8 days. It travels slowly and sadly under the +pale and languishing rays of the Sun, which sends it nearly three +hundred times less of light and heat than we receive. At this distance +the solar disk would present a diameter seventeen times smaller than +that which we admire, and a surface three hundred times less vast. A +dull world indeed! And what an interminable year! The idle people who +are in the habit of being bored must find time even longer upon Uranus +than upon our little Earth, where the days pass so rapidly. And if +matters are arranged there as here, a babe of a year old, beginning to +babble in its nurse's arms, would already have lived as long as an old +man of eighty-four in this world. + +But what most seriously complicates the Calendar of the Uranians is the +fact that the four moons which accompany the planet accomplish their +revolution in four different kinds of months, in two, four, eight, and +thirteen days, as is shown in the following table: + + Distance from the planet. Time of revolution. + Kilometers. Miles. Days. Hours. Minutes. + + 1. Ariel 196,000 121,520 2 12 29 + 2. Umbriel 276,000 171,120 4 3 27 + 3. Titania 450,000 279,000 8 16 56 + 4. Oberon 600,000 372,000 13 11 7 + +The most curious fact is that these satellites do not rotate like those +of the other planets. While the moons of the Earth, Mars, Jupiter, and +Saturn accomplish their revolution from east to west, the satellites of +Uranus rotate in a plane almost perpendicular to the ecliptic, and it is +doubtless the same for the rotation of the planet. + +If we had to quit the Earth, and fixate ourselves upon another world, +we should prefer Mars to Uranus, where everything must be so different +from terrestrial arrangements? But who knows? Perhaps, after all, this +planet might afford us some agreeable surprises. _Il ne faut jurer de +rien._ + + +NEPTUNE + +And here we reach the frontier of the Solar System, as actually known to +us. In landing on the world of Neptune, which circles through the +Heavens in eternal twilight at a distance of more than four milliard +kilometers (2,480,000,000 miles) from the common center of attraction of +the planetary orbs, we once again admire the prodigies of science. + +Uranus was discovered with the telescope, Neptune by calculation. In +addition to the solar influence, the worlds exert a mutual attraction +upon each other that slightly deranges the harmony ordered by the Sun. +The stronger act upon the weaker, and the colossal Jupiter alone causes +many of the perturbations in our great solar family. Now during regular +observations of the position of Uranus in space, some inexplicable +irregularities were soon perceived. The astronomers having full faith in +the universality of the law of attraction, could not do otherwise than +attribute these irregularities to the influence of some unknown planet +situated even farther off. But at what distance? + +A very simple proportion, known as Bode's law, has been observed, which +indicates approximately the relative distances of the planets from the +Sun. It is as follows: Starting from 0, write the number 3, and double +successively, + + 0 3 6 12 24 48 96 192 384. + +Then, add the number 4 to each of the preceding figures, which gives the +following series: + + 4 7 10 16 28 52 100 196 388. + +Now it is a very curious fact that if the distance between the Earth and +the Sun be represented by 10, the figure 4 represents the orbit of +Mercury, 7 that of Venus, 16 of Mars; the figure 28 stands for the +medium distance of the minor planets; the distances of Jupiter, Saturn, +and Uranus agree with 52, 100, and 196. + +The immortal French mathematician Le Verrier, who pursued the solution +of the Uranian problem, supposed naturally that the disturbing planet +must be at the distance of 388, and made his calculations accordingly. +Its direction in the Heavens was indicated by the form of the +disturbances; the orbit of Uranus bulging, as it were, on the side of +the disturbing factor. + +On August 31, 1846, Le Verrier announced the position of the +ultra-Uranian planet, and on September 23d following, a German +astronomer, Galle, at the Observatory of Berlin, who had just received +this intelligence, pointed his telescope toward the quarter of the +Heavens designated, and, in fact, attested the presence of the new orb. +Without quitting his study table, Le Verrier, by the sole use of +mathematics, had detected, and, as it were, touched at pen's point the +mysterious stranger. + +Only, it is proved by observation and calculation that it is less remote +than was expected from the preceding law, for it gravitates at a +distance of 300, given that from the Earth to the Sun as 10. + +This planet was called Neptune, god of the seas, son of Saturn, brother +of Jupiter. The name is well chosen, since the King of the Ocean lives +in darkness in the depths of the sea, and Le Verrier's orb is also +plunged in the semi-obscurity of the depths of the celestial element. +But it was primarily selected to do justice to an English astronomer, +Adams, who had simultaneously made the same calculations as Le Verrier, +and obtained the same results--without publishing them. His work +remained in the records of the Greenwich Observatory. + +The English command the seas, and wherever they dip their finger into +the water and find it salt, they feel themselves "at home," and know +that "Neptune's trident is the scepter of the world," hence this +complimentary nomenclature. + +Neptune is separated by a distance of four milliards, four hundred +million kilometers from the solar center. + +At such a distance, thirty times greater than that which exists between +the Sun and our world, Neptune receives nine hundred times less light +and heat than ourselves; _i.e._, Spitzbergen and the polar regions of +our globe are furnaces compared with what must be the Neptunian +temperature. Absolutely invisible to the unaided eye, this world +presents in the telescope the aspect of a star of the eighth magnitude. +With powerful magnifications it is possible to measure its disk, which +appears to be slightly tinged with blue. Its diameter is four times +larger than our own, and measures about 48,000 kilometers (29,900 +miles), its surface is sixteen times vaster than that of the Earth, and +to attain its volume we should have to put together fifty-five globes +similar to our own. Weight at its surface must be about the same as +here, but its medium density is only 1/3 that of the Earth. + +It gravitates slowly, dragging itself along an orbit thirty times vaster +than that of our globe, and its revolution takes 164 years, 281 days, +_i.e._, 164 years, 9 months. A single year of Neptune thus covers +several generations of terrestrial life. Existence must, indeed, be +strange in that tortoise-footed world! + +While in their rotation period, Mercury accomplishes 47 kilometers +(29-3/8 miles) per second, and the Earth 29-1/2 (18-1/8 miles), Neptune +rolls along his immense orbit at a rate of only 5-1/2 kilometers (about +3-1/4 miles) per second. + +The vast distance that separates us prevents our distinguishing any +details of his surface, but spectral analysis reveals the presence of an +absorbent atmosphere in which are gases unknown to the air of our +planet, and of which the chemical composition resembles that of the +atmosphere of Uranus. + +One satellite has been discovered for Neptune. It has a considerable +inclination, and rotates from east to west. + + * * * * * + +And here we have reached the goal of our interplanetary journey. After +visiting the vast provinces of the solar republic, we feel yet greater +admiration and gratitude toward the luminary that governs, warms, and +illuminates the worlds of his system. + +In conclusion, let us again insist that the Earth,--a splendid orb as +viewed from Mercury, Venus, and Mars,--begins to disappear from Jupiter, +where she becomes no more than a tiny spark oscillating from side to +side of the Sun, and occasionally passing in front of him as a small +black dot. From Saturn the visibility of our planet is even more +reduced. As to Uranus and Neptune, we are invisible there, at least to +eyes constructed like our own. We do not possess in the Universe the +importance with which we would endow ourselves. + +Neptune up to the present guards the portals of our celestial system; we +will leave him to watch over the distant frontier; but before returning +to the Earth, we must glance at certain eccentric orbs, at the mad, +capricious comets, which imprint their airy flight upon the realms of +space. + + + + +CHAPTER VII + +THE COMETS + +SHOOTING STARS, BOLIDES, URANOLITHS OR METEORIC STONES + + +What marvels have been reviewed by our dazzled eyes since the outset of +these discussions! We first surveyed the magnificent host of stars that +people the vast firmament of Heaven; next we admired and wondered at +suns very differently constituted from our own; then returning from the +depths of space, crossing at a bound the abyss that separates us from +these mysterious luminaries, the distant torches of our somber night, +terrible suns of infinity, we landed on our own beloved orb, the superb +and brilliant day-star. Thence we visited his celestial family, his +system, in which our Earth is a floating island. But the journey would +be incomplete if we omitted certain more or less vagabond orbs, that +occasionally approach the Sun and Earth, some of which may even collide +with us upon their celestial path. These are in the first place the +comets, then the shooting stars, the fire-balls, and meteorites. + +Glittering, swift-footed heralds of Immensity, these comets with golden +wings glide lightly through Space, shedding a momentary illumination by +their presence. Whence come they? Whither are they bound? + +What problems they propound to us, when, as in some beautiful display of +pyrotechnics, the arch of Heaven is illuminated with their fantastic +light! + +But first of all--what is a Comet? + +If instead of living in these days of the telescope, of spectrum +analysis, and of astral photography, we were anterior to Galileo, and to +the liberation of the human spirit by Astronomy, we should reply that +the comet is an object of terror, a dangerous menace that appears to +mortals in the purity of the immaculate Heavens, to announce the most +fatal misfortunes to the inhabitants of our planet. Is a comet visible +in the Heavens? The reigning prince may make his testament and prepare +to die. Another apparition in the firmament bodes war, famine, the +advent of grievous pestilence. The astrologers had an open field, and +their fertile imagination might hazard every possible conjecture, seeing +that misfortunes, great or small, are not altogether rare in this +sublunar world. + +How many intellects, and those not the most vulgar, from antiquity to +the middle of the last century cursed the apparition of these hirsute +stars, which brought desolation to the heart of man, and poured their +fatal effluvia upon the head of poor Humanity. The history of the +superstitions and fears that they inspired of old would furnish matter +for the most thrilling of romances. But, on the other hand, the volume +would be little flattering to the common-sense of our ancestors. Despite +the respect we owe our forefathers, let us recall for a moment the +prejudices attaching to the most famous comets whose passage, as +observed from the Earth, has been preserved to us in history. + +[Illustration: FIG. 49.--Great Comet of 1858.] + + * * * * * + +Without going back to the Deluge, we note that the Romans established a +relation between the Great Comet of 43 B.C. and the death of Cæsar, who +had been assassinated a few months previously. It was, they asserted, +the soul of their great Captain, transported to Heaven to reign in the +empyrean after ruling here below. Were not the Emperors Lords of both +Earth and Heaven? + +We must in justice recognize that certain more independent spirits +emancipated themselves from these superstitions, and we may cite the +reply of Vespasian to his friends, who were alarmed at the evil presage +of a flaming comet: "Fear nothing," he said, "this bearded star concerns +me not; rather should it threaten my neighbor the King of the Parthians, +since he is hairy and I am bald." + +In the year 837 one of these mysterious visitants appeared in the +Heavens. It was in the reign of Lewis the Debonair. Directly the King +perceived the comet, he sent for an astrologer, and asked what he was to +conclude from the apparition. As the answers were unsatisfactory he +tried to avert the augury by prayers to Heaven, by ordaining a general +fast to all his Court, and by building churches. Notwithstanding, he +died three years later, and the historians profited by this slender +coincidence to set up a correlation between the fatal star and the death +of the Sovereign. This comet, famous in history, is no other than that +of Halley, in one of its appearances. + +This comet returned to explore the realms near the Sun in 1066, at the +moment when William of Normandy was undertaking the Conquest of England, +and was misguided enough to go across and reign in London, instead of +staying at home and annexing England, thus by his action founding the +everlasting rivalry between France and this island. A beneficial +influence was attributed to the comet in the Battle of Hastings. + +A few centuries later it again came into sight from the Earth, in 1456, +three years after the capture of Constantinople by the Turks. Feeling +ran high in Europe, and this celestial omen was taken for a proof of the +anger of the Almighty. The moment was decisive; the Christians had to be +rescued from a struggle in which they were being worsted. At this +conjuncture, Pope Calixtus resuscitated a prayer that had fallen into +disuse, the _Angelus_; and ordered that the bells of the churches should +be rung each day at noon, that the Faithful might join at the same hour +in prayer against the Turks and the Comet. This custom has lasted down +to our own day. + +Again, to the comet of 1500 was attributed the tempest that caused the +death of Bartholomew Diaz, a celebrated Portuguese navigator, who +discovered the Cape of Good Hope. + +In 1528 a bearded star of terrific aspect alarmed the world, and the +more serious spirits were influenced by this menacing comet, which +burned in the Heavens like "a great and gory sword." In a chapter on +Celestial Monsters the celebrated surgeon Ambroise Paré describes this +awful phenomenon in terms anything but seductive, or reassuring, showing +us the menacing sword surrounded by the heads it had cut off (Fig. 50). + +[Illustration: FIG. 50.--What our Ancestors saw in a Comet. + +_After Ambroise Paré (1528)._] + +[Illustration: FIG. 51.--Prodigies seen in the Heavens by our +Forefathers.] + +Omens of battle, 1547. + +Deer and warriors, July 19, 1550. + +Cavalry, and a bloody branch crossing the sun, June 11, 1554.] + +Our fathers saw many other prodigies in the skies; their descendants, +less credulous, can study the facsimile reproduced in Fig. 51, of the +drawings published in the year 1557 by Conrad Lycosthenes in his curious +Book of Prodigies. + +So, too, it is asserted that Charles V renounced the jurisdiction of his +Estates, which were so vast that "the Sun never slept upon them," +because he was terrified by the comet of 1556 which burned in the skies +with an alarming brilliancy, into passing the rest of his days in prayer +and devotion. + +It is certain that comets often exhibit very strange characteristics, +but the imagination that sees in them such dramatic figures must indeed +be lively. In the Middle Ages and the Renaissance these were swords of +fire, bloody crosses, flaming daggers, etc., all horrible objects ready +to destroy our poor human race! + +At the time of the Romans, Pliny made some curious distinctions between +them: "The Bearded Ones let loose their hair like a majestic beard; the +Javelin darts forth like an arrow; if the tail is shorter and ends in a +point, it is called the Sword; this is the palest of all the Comets; it +shines like a sword, without rays; the Plate or Disk is named in +conformity with its figure; its color is amber, the Barrel is actually +shaped like a barrel, as it might be in smoke, with light streaming +through it; the Horn imitates the figure of a horn erected in the sky, +and the Lamp that of a burning flame; the Equine represents a horse's +mane, shaken violently with a circular motion. There are bristled +comets; these resemble the skins of beasts with the fur on them, and are +surrounded by a nebulosity. Lastly, the tails of certain comets have +been seen to menace the sky in the form of a lance." + +These hairy orbs that appear in all directions, and whose trajectories +are sometimes actually perpendicular to the plane of the ecliptic, +appear to obey no regular law. Even in the seventeenth century the +perspicacious Kepler had not divined their true character, seeing in +them, like most of his contemporaries, emanations from the earth, a sort +of vapor, losing itself in space. These erratic orbs could not be +assimilated with the other members of our grand solar family where, +generally speaking, everything goes on in regular order. + +And even in our own times, have we not seen the people terrified at the +sight of a flaming comet? Has not the end of the world by the agency of +comets been often enough predicted? These predictions are so to speak +periodic; they crop up each time that the return of these cosmical +formations is announced by the astronomers, and always meet with a +certain number of timid souls who are troubled as to our destinies. + + * * * * * + +To-day we know that these wanderers are subject to the general laws +that govern the universe. The great Newton announced that, like the +planets, they were obedient to universal attraction; that they must +follow an extremely elongated curve, and return periodically to the +focus of the ellipse. From the basis of these data Halley calculated the +progress of the comet of 1682, and ascertained that its motions +presented such similarity with the apparitions of 1531 and 1607, that he +believed himself justified in identifying them and in announcing its +return about the year 1759. Faithful to the call made upon it, +irresistibly attracted by the Orb of Day, the comet, at first pale, then +ardent and incandescent, returned at the date assigned to it by +calculation, three years after the death of the illustrious astronomer. +Shining upon his grave it bore witness to the might of human thought, +able to snatch the profoundest secrets from the Heavens! + +This fine comet returns every seventy-six years, to be visible from the +Earth, and has already been seen twenty-four times by the astonished +eyes of man. It appears, however, to be diminishing in magnitude. Its +last appearance was in 1835, and we shall see it again in 1910, a little +sooner than its average period, the attraction of Jupiter having this +time slightly accelerated its course, while in 1759 it retarded it. + +The comets thus follow a very elongated orbit, either elliptic, turning +round the Sun, or parabolic, dashing out into space. In the first case, +they are periodic (Fig. 52), and their return can be calculated. In the +second they surprise us unannounced, and return to the abysses of +eternity to reappear no more. + +[Illustration: FIG. 52.--The orbit of a Periodic Comet.] + +Their speed is even greater than that of the planets, it is equivalent +to this, multiplied by the square root of 2, that is to say by 1.414. +Thus at the distance of the Earth from the Sun this velocity = 29,500 +meters (18 miles) per second, multiplied by the above number, that is, +41,700 meters (over 25 miles). At the distance of Mercury it = 47 × +1.414 or 66,400 meters (over 40 miles) per second. + +Among the numerous comets observed, we do not as yet know more than some +twenty of which the orbit has been determined. Periodicity in these +bearded orbs is thus exceptional, if we think of the innumerable +multitude of comets that circle through the Heavens. Kepler did not +exaggerate when he said "there are as many comets in the skies as there +are fishes in the sea." These scouts of the sidereal world constitute a +regular army, and if we are only acquainted with the dazzling generals +clad in gold, it is because the more modest privates can only be +detected in the telescope. Long before the invention of the latter, +these wanderers in the firmament roamed through space as in our own day, +but they defied the human eye, too weak to detect them. Then they were +regarded as rare and terrible objects that no one dared to contemplate. +To-day they may be counted by hundreds. They have lost in prestige and +in originality; but science is the gainer, since she has thus endowed +the solar system with new members. No year passes without the +announcement of three or four new arrivals. But the fine apparitions +that attract general attention by their splendor are rare enough. + +These eccentric visitors do not resemble the planets, for they have no +opaque body like the Earth, Venus, Mars, or any of the rest. They are +transparent nebulosities, of extreme lightness, without mass nor +density. We have just photographed the comet of the moment, July, 1903: +the smallest stars are visible through its tail, and even through the +nucleus. + +They arrive in every direction from the depths of space, as though to +reanimate themselves in the burning, luminous, electric solar center. + +Attracted by some potent charm toward this dazzling focus, they come +inquisitive and ardent, to warm themselves at its furnace. At first pale +and feeble, they are born again when the Sun caresses them with his +fervid heat. Their motions accelerate, they haste to plunge wholly into +the radiant light. At length they burst out luminous and superb, when +the day-star penetrates them with his burning splendor, illuminates them +with a marvelous radiance, and crowns them with glory. But the Sun is +generous. Having showered benefits upon these gorgeous celestial +butterflies that flutter round him as round some altar of the gods, he +grants them liberty to visit other heavens, to seek fresh universes.... + +The original parabola is converted into an ellipse, if the imprudent +adventurer in returning to the Sun passes near some great planet, such +as Jupiter, Saturn, Uranus, or Neptune, and suffers its attraction. It +is then imprisoned by our system, and can no longer escape from it. +After reenforcement at the solar focus, it must return to the identical +point at which it felt the first pangs of a new destiny. Henceforward, +it belongs to our celestial family, and circles in a closed curve. +Otherwise, it is free to continue its rapid course toward other suns and +other systems. + + * * * * * + +As a rule, the telescope shows three distinct parts in a comet. There is +first the more brilliant central point, or _nucleus_, surrounded by a +nebulosity called the _hair_, or _brush_, and prolonged in a luminous +appendix stretching out into the _tail_. The _head_ of the comet is the +brush and the nucleus combined. + +[Illustration: FIG. 53.--The tails of Comets are opposed to the Sun.] + +It is usually supposed that the tail of a comet follows it throughout +the course of its peregrinations. Nothing of the kind. The appendix may +even precede the nucleus; it is always opposite the Sun,--that is to +say, it is situated on the prolongation of a straight line, starting +from the Sun, and passing through the nucleus (Fig. 53). The tail does +not exist, so long as the comet is at a distance from the orb of day; +but in approaching the Sun, the nebulosity is heated and dilates, giving +birth to those mysterious tails and fantastic streamers whose +dimensions vary considerably for each comet. The dilations and +transformations undergone by the tail suggest that they may be due to a +repulsive force emanating from the Sun, an electric charge transmitted +doubtless through the ether. It is as though Phoebus blew upon them +with unprecedented force. + +Telescopic comets are usually devoid of tail, even when they reach the +vicinity of the Sun. They appear as pale nebulosities, rounded or oval, +more condensed toward the center, without, however, showing any distinct +nucleus. These stars are only visible for a minute fraction of their +course, when they reach a point not far from the Sun and the terrestrial +orbit. + +The finest comets of the last century were those of 1811, 1843, 1858, +1861, 1874, 1880, 1881, and 1882. The Great Comet of 1811, after +spreading terror over certain peoples, notably in Russia, became the +providence of the vine-growers. As the wine was particularly good and +abundant that year, the peasants attributed this happy result to the +influence of the celestial visitant. + +In 1843 one of these strange messengers from the Infinite appeared in +our Heavens. It was so brilliant that it was visible in full daylight on +February 28th, alongside of the Sun. This splendid comet was +accompanied by a marvelous rectilinear tail measuring 300,000,000 +kilometers (186,000,000 miles) in length, and its flight was so rapid +that it turned the solar hemisphere at perihelion in two hours, +representing a speed of 550 kilometers (342 miles) a second. + +But the most curious fact is that this radiant apparition passed so near +the Sun that it must have traversed its flames, and yet emerged from +them safe and sound. + +Noteworthy also was the comet of 1858 (Fig. 49), discovered at Florence +by Donati. Its tail extended to a length of 90,000,000 kilometers +(55,900,000 miles), and its nucleus had a diameter of at least 900 +kilometers (559 miles). It is a curious coincidence that the wine was +remarkably excellent and abundant in that year also. + +The comet of 1861 almost rivaled the preceding. + +Coggia's Comet, in 1874, was also remarkable for its brilliancy, but was +very inferior to the last two. Finally, the latest worthy of mention +appeared in 1882. This magnificent comet also touched the Sun, traveling +at a speed of 480 kilometers (299 miles) per second. It crossed the +gaseous atmosphere of the orb of day, and then continued its course +through infinity. On the day of, and that following, its perihelion, it +could be detected with the unaided eye in full daylight, enthroned in +the Heavens beside the dazzling solar luminary. For the rest, it was +neither that of 1858 nor of 1861. + +Since 1882 we have not been favored with a visit from any fine comet; +but we are prepared to give any such a reception worthy of their +magnificence: first, because now that we have fathomed them we are no +longer awestruck; second, because we would gladly study them more +closely. + + * * * * * + +In short, these hirsute stars, whose fantastic appearance impressed the +imagination of our ancestors so vividly, are no longer formidable. Their +mass is inconsiderable; they seem to consist mainly of the lightest of +gases. Analysis of their incandescence reveals a spectrum closely +resembling that of many nebulæ; the presence of carbon is more +particularly obvious. Even the nucleus is not solid, and is often +transparent. + +It is fair to say that the action of a comet might be deleterious if one +of these orbs were to arrive directly upon us. The transformation of +motion into heat, and the combination of the cometary gases with the +oxygen of our atmosphere might produce a conflagration, or a general +poisoning of the atmosphere. + +But the collision of a comet with a planet is almost an impossibility. +This phenomenon could only occur if the comet crossed the planetary +orbit at the exact moment at which the planet was passing. When we +think of the immensity of space, of the extraordinary length of way +traversed by a world in its annual journey round the Sun, and the speed +of its rotation, we see why this coincidence is hardly likely to occur. +Thus, among the hundreds of comets catalogued, a few only cut the +terrestrial orbit. One of them, that of 1832, traversed the path of our +globe in the nights of October 29 and 30 in that year; but the Earth +only passed the same point thirty days later, and at the critical period +was more than 80,000,000 kilometers (50,000,000 miles) away from the +comet. + +On June 30, 1861, however, the Earth passed through the extremity of the +tail of the Great Comet of that year. No one even noticed it. The +effects were doubtless quite immaterial. + +In 1872 we were to collide with Biela's Comet, lost since 1852; now, as +we shall presently see, we came with flying colors out of that +disagreeable situation, because the comet had disintegrated, and was +reduced to powder. So we may sleep in peace as regards future danger +likely to come to us from comets. There is little fear of the +destruction of humanity by these windy bags. + +These ethereal beauties whose blond locks float carelessly upon the +azure night are not concerned with us; they seem to have no other +preoccupation than to race from sun to sun, visiting new Heavens, +indifferent to the astonishment they produce in us. They speed +restlessly and tirelessly through infinity; they are the Amazons of +space. + +What suns, what worlds must they have visited since the moment of their +birth! If these splendid fugitives could relate the story of their +wanderings, how gladly should we listen to the enchanting descriptions +of the various abodes they have journeyed to! But alas! these mysterious +explorers are dumb; they tell none of their secrets, and we must needs +respect their enigmatic silence. + +Yet, some of them have left us a modest token of remembrance, an almost +impalpable nothing, sufficient, however, to enable us to address our +thanks to the considerate messenger. + + * * * * * + +Can there be any one upon the Earth who has not been struck by the +phosphorescent lights that glide through the somber night, leaving a +brilliant silver or golden track--the luminous, ephemeral trail of a +meteor? + +Sometimes, when Night has silently spread the immensity of her wings +above the weary Earth, a shining speck is seen to detach itself in the +shades of evening from the starry vault, shooting lightly through the +constellations to lose itself in the infinitude of space. + +[Illustration: FIG. 54.--A Meteor.] + +These bewitching sparks attract our eyes and chain our senses. +Fascinating celestial fireflies, their dainty flames dart in every +direction through space, sowing the fine dust of their gilded wings upon +the fields of Heaven. They are born to die; their life is only a breath; +yet the impression which they make upon the imagination of mortals is of +the profoundest. + +The young girl dreaming in the delicious tranquillity of the transparent +night smiles at this charming sister in the Heavens (Fig. 54). What can +not this adorable star announce to the tender and loving heart? Is it +the shy messenger of the happiness so long desired? Its unpremeditated +appearance fills the soul with a ray of hope and makes it tremble. It is +a golden beam that glides into the heart, expanding it in the thrills of +a sudden and ephemeral pleasure.... The radiant meteor seems to quit the +velvet of the deep blue sky to respond to the appeal of the imploring +voice that seeks its succor. + +What secrets has it not surprised! And who bears malice against it? It +is the friend of the betrothed who invoke its passage to confide their +wishes, and associate it with their dreams. Tradition holds that if a +wish be formulated during the visible passage of a meteor it will +certainly be fulfilled before the year is out. Between ourselves, +however, this is but a surviving figment of the ancestral imagination, +for this celestial jewel takes no such active part in the doings of +Humanity.... Besides, try to express a wish distinctly in a second! + +It is a curious fact that while comets have so often spread terror on +the Earth, shooting stars should on the contrary have been regarded with +benevolent feelings at all times. And what is a shooting star? These +dainty excursionists from the celestial shores are not, as is supposed, +true stars. They are atoms, nothings, minute fragments deriving in +general from the disintegration of comets. They come to us from a vast +distance, from millions on millions of miles, and circle in swarms +around the Sun, following a very elongated ellipse which closely +resembles that of the cometary orbit. Their flight is extremely rapid, +reaching sometimes more than 40 kilometers (25 miles) per second, a +cometary speed that is, as we have seen, greatly above that of our +terrestrial vehicle, which amounts to 29 to 30 kilometers (about 19 +miles). + +These little corpuscles are not intrinsically luminous; but when the +orbit of a swarm of meteors crosses our planet, a violent shock arises, +the speed of which may be as great as 72 kilometers (45 miles) in the +first second if we meet the star shower directly; the average rate, +however, does not exceed 30 to 40 kilometers (19 to 25 miles), for these +meteors nearly always cross our path obliquely. The height at which they +arrive is usually 110 kilometers (68 miles), and 80 kilometers (50 +miles) at the moment of disappearance of the meteor; but shooting stars +have been observed at 300 kilometers (186 miles). + +The friction caused by this collision high up in the atmosphere +transforms the motion into heat. The molecules incandesce, and burn like +true stars with a brilliancy that is often magnificent. + +But their glory is of short duration. The excessive heat resulting from +the shock consumes the poor firefly; its remains evaporate, and drop +slowly to the Earth, where they are deposited on the surface of the soil +in a sort of ferruginous dust mixed with carbon and nickel. Some one +hundred and forty-six milliards of them reach us annually, as seen by +the unaided eye, and many more in the telescope; the effect of these +showers of meteoric matter is an insensible increase in the mass of our +globe, a slight lessening of its rotary motion, and the acceleration of +the lunar movements of revolution. + +Although the appearance of shooting stars is a common enough phenomenon, +visible every night of the year, there are certain times when they +arrive in swarms, from different quarters of the sky. The most +remarkable dates in this connection are the night of August 10th and the +morning of November 14th. Every one knows the shooting stars of August +10th, because they arrive in the fine warm summer evenings so favorable +to general contemplation of the Heavens. The phenomenon lasts till the +12th, and even beyond, but the maximum is on the 10th. When the sky is +very clear, and there is no moon, hundreds of shooting stars can be +counted on those three nights, sometimes thousands. They all seem to +come from the same quarter of the Heavens, which is called the +_radiant_, and is situated for the August swarm in the constellation of +Perseus, whence they have received the name of _Perseids_. Our +forefathers also called them the tears of St. Lawrence, because the +feast of that saint is on the same date. These shooting stars describe a +very elongated ellipse, and their orbit has been identified with that of +the Great Comet of 1862. + +The shower of incandescent asteroids on November 14th is often much more +abundant than the preceding. In 1799, 1833, and 1866, the meteors were +so numerous that they were described as showers of rain, especially on +the first two dates. For several hours the sky was furrowed with falling +stars. An English mariner, Andrew Ellicot, who made the drawing we +reproduce (Fig. 55), described the phenomenon as stupendous and alarming +(November 12, 1799, 3 A.M.). The same occurred on November 13, 1833. The +meteors that scarred the Heavens on that night were reckoned at 240,000. +These shooting stars received the name of _Leonids_, because their +radiant is situated in the constellation of the Lion. + +[Illustration: FIG. 55.--Shooting Stars of November 12, 1799. + +_From a contemporary drawing._] + +This swarm follows the same orbit as the comet of 1866, which travels as +far as Uranus, and comes back to the vicinity of the Sun every +thirty-three years. Hence we were entitled to expect another splendid +apparition in 1899, but the expectations of the astronomers were +disappointed. All the preparations for the appropriate reception of +these celestial visitors failed to bring about the desired result. The +notes made in observatories, or in balloons, admitted of the +registration of only a very small number of meteors. The maximum was +thirteen. During that night, some 200 shooting stars were counted. There +were more in 1900, 1901, and, above all, in 1902. This swarm has become +displaced. + +The night of November 27th again is visited by a number of shooting +stars that are the disaggregated remains of the Comet of Biela. This +comet, discovered by Biela in 1827, accomplished its revolution in six +and a half years, and down to 1846 it responded punctually to the +astronomers who expected its return as fixed by calculation. But on +January 13, 1846, the celestial wanderer broke in half: each fragment +went its own way, side by side, to return within sight from the Earth in +1852. It was their last appearance. That year the twin comets could +still be seen, though pale and insignificant. Soon they vanished into +the depths of night, and never appeared again. They were looked for in +vain, and were despaired of, when on November 27, 1872, instead of the +shattered comet, came a magnificent rain of shooting stars. They fell +through the Heavens, numerous as the flakes of a shower of snow. + +The same phenomenon recurred on November 27, 1885, and confirmed the +hypothesis of the demolition and disaggregation of Biela's Comet into +shooting stars. + + * * * * * + +There is an immense variety in the brilliancy of the shooting stars, +from the weak telescopic sparks that vanish like a flash of lightning, +to the incandescent _bolides_ or _fire-balls_ that explode in the +atmosphere. + +Fig. 56 shows an example of these, and it represents a fire-ball +observed at the Observatory of Juvisy on the night of August 10, 1899. +It arrived from Cassiopeia, and burst in Cepheus. + +This phenomenon may occur by day as well as by night. It is often +accompanied by one or several explosions, the report of which is +sometimes perceptible to a considerable distance, and by a shower of +meteorites. The globe of fire bursts, and splits up into luminous +fragments, scattered in all directions. The different parts of the +fire-ball fall to the surface of the Earth, under the name of aerolites, +or rather of uranoliths, since they arrive from the depths of space, and +not from our atmosphere. + +From the most ancient times we hear of showers of uranoliths to which +popular superstitions were attached; and the Greeks even gave the name +of _Sideros_ to iron, the first iron used having been sidereal. + +[Illustration: FIG. 56.--Fire-Ball seen from the Observatory at Juvisy, +August 10, 1899.] + +[Illustration: FIG. 57.--Explosion of a Fire-Ball above Madrid, +February 10, 1896.] + +No year passes without the announcement of several showers of +uranoliths, and the phenomenon sometimes causes great alarm to those who +witness it. One of the most remarkable explosions is that which occurred +above Madrid, February 10, 1896, a fragment from which, sent me by M. +Arcimis, Director of the Meteorological Institute, fell immediately in +front of the National Museum (Fig. 57). The phenomenon occurred at 9.30 +A.M., in brilliant sunshine. The flash of the explosion was so dazzling +that it even illuminated the interior of the houses; an alarming clap of +thunder was heard seventy seconds after, and it was believed that an +explosion of dynamite had occurred. The fire-ball burst at a height of +fourteen miles, and was seen as far as 435 miles from Madrid! + +In one of Raphael's finest pictures (_The Madonna of Foligno_) a +fire-ball may be seen beneath a rainbow (Fig. 58), the painter wishing +to preserve the remembrance of it, as it fell near Milan, on September +4, 1511. This picture dates from 1512. + +The dimensions of these meteorites vary considerably; they are of all +sizes, from the impalpable dust that floats in the air, to the enormous +blocks exposed in the Museum of Natural History in Paris. Many of them +weigh several million pounds. That represented below fell in Mexico +during the shower of meteors of November 27, 1885. It weighed about four +pounds. + +[Illustration: FIG. 58.--Raphael's Fire-Ball (_The Madonna of +Foligno_).] + +These bolides and uranoliths come to us from the depths of space; but +they do not appear to have the same origin as the shooting stars. They +may arise from worlds destroyed by explosion or shock, or even from +planetary volcanoes. The lightest of them may have been expelled from +the volcanoes of the Moon. Some of the most massive, in which iron +predominates, may even have issued from the bowels of the Earth, +projected into space by some volcanic explosion, at an epoch when our +globe was perpetually convulsed by cataclysms of extraordinary violence. +They return to us to-day after being removed from the Earth to distances +proportional to the initial speed imparted to them. This origin seems +the more admissible as the stones that fall from the skies exhibit a +mineral composition identical with that of the terrestrial materials. + +[Illustration: FIG. 59.--A Uranolith.] + +In any case, these uranoliths bring us back at least by their fall to +our Earth, and from henceforward we will remain upon it, to study its +position in space, and to take account of the place it fills in the +Universe, and of the astronomical laws that govern our destiny. + + + + +CHAPTER VIII + +THE EARTH + + +Our grand celestial journey lands us upon our own little planet, on this +globe that gravitates between Mars and Venus (between War and Love), +circulating like her brothers of the solar system, around the colossal +Sun. + +The Earth! The name evokes in us the image of Life, and calls up the +theater of our activities, our ambitions, our joys and sorrows. Does it +not, in fact, to ignorant eyes, represent the whole of the universe? + +And yet, what is the Earth? + +The Earth is a star in the Heavens. We learned this much in our first +lesson. It is a globe of opaque material, similar to the planets +Mercury, Venus, Mars, Jupiter, etc., as previously described. Isolated +on all sides in space, it revolves round the Sun, along a vast orbit +that it accomplishes in a year. And while it thus glides along the lines +of solar attraction, the terrestrial ball rotates rapidly upon itself in +twenty-four hours. + +These statements may appear dubious at first sight, and contradictory to +the evidence of our senses. + +Now that the surface of the Earth has been explored in all directions, +there is no longer room to doubt that it is a globe, a sort of ball that +we adhere to. A journey round the world is common enough to-day, and +always yields the most complete evidence of the spherical nature of the +Earth. On the other hand, the curvature of the seas is a no less certain +proof. When a ship reaches the dark-blue line that appears to separate +the sky from the ocean, it seems to be hanging on the horizon. Little by +little, however, as it recedes, it drops below the horizon line; the +tops of the masts being the last to disappear. The observer on board +ship witnesses the same phenomenon. The low shores are first to +disappear, while the high coasts and mountains are much longer visible. + +The aspect of the Heavens gives another proof of the Earth's rotundity. +As one travels North or South, new stars rise higher and higher above +the horizon in the one direction or the other, and those which shine in +the latitude one is leaving, gradually disappear. If the surface of the +Earth were flat, the ships on the sea would be visible as long as our +sight could pierce the distance, and all the stars of the Heavens would +be equally visible from the different quarters of the world. + +Lastly, during the eclipses of the Moon, the shadow projected by the +Earth upon our satellite is always round. This is another proof of the +spherical nature of the terrestrial globe. + +We described the Earth as an orb in the Heavens, similar to all the +other planets of the great solar family. We see these sister planets of +our world circulating under the starry vault, like luminous points whose +brilliancy is sometimes dazzling. For us they are marvelous celestial +birds hovering in the ether, upheld by invisible wings. The Earth is +just the same. It is supported by nothing. Like the soap-bubble that +assumes a lovely iridescence in the rays of the Sun, or, better, like +the balloon rapidly cleaving the air, it is isolated from every kind of +support. + +Some minds have difficulty in conceiving this isolation, because they +form a false notion of weight. + +The astronomers of antiquity, who divined it, knew not how to prevent +the Earth from falling. They asked anxiously what the strong bands +capable of holding up this block of no inconsiderable weight could be. +At first they thought it floated on the waters like an island. Then they +postulated solid pillars, or even supposed it might turn on pivots +placed at the poles. But on what would all these imaginary supports have +rested? All these fanciful foundations of the Earth had to be given up, +and it was recognized as a globe, isolated in every part. This illusion +of the ancients, which still obtains for a great many citizens of our +globule, arises, as we said, from a false conception of weight. + +Weight and attraction are one and the same force. + +A body can only fall when it is attracted, drawn by a more important +body. Now, in whatever direction we may wander upon the globe, our feet +are always downward. _Down_ is therefore the _center_ of the Earth. + +The terrestrial globe may be regarded as an immense ball of magnet, and +its attraction holds us at its surface. We weigh toward the center. We +may travel over this surface in all directions; our feet will always be +below, whatever the direction of our steps. For us, "below" is the +inside of our planet, and "above" is the immensity of the Heavens that +extend above our heads, right round the globe. + +This once understood, where could the Earth fall to? The question is an +absurdity. "Below" being toward the center, it would have to fall out of +itself. + +Let us then picture the Earth as a vast sphere, detached from all that +exists around it, in the infinity of the Heavens. A point diametrically +opposed to another is called its _antipodes_. New Zealand is +approximately the antipodes to France. Well, for the inhabitants of New +Zealand and of France the top is reciprocally opposed, and the bottom, +or the feet, are diametrically in opposition. And yet, for one as for +the other, the bottom is the soil they are held to, and the top is +space above their heads. + +The Earth turns on itself in twenty-four hours. Whatever is above us, +_e.g._, at midday, we call high; twelve hours later, at midnight, we +give the same qualification to the part of space that was under our feet +at noon. What is in the sky, and over our heads, at a given hour, is +under our feet, and yet always in the sky, twelve hours later. Our +position, in relation to the space that surrounds us, changes from hour +to hour, and "top" and "bottom" vary also, relatively to our position. + +Our planet is thus a ball, slightly flattened at the poles (by about +1/292). Its diameter, at the equator, is 12,742 kilometers (7,926 +miles); from one pole to the other is a little less, owing to the +flattening of the polar caps. The difference is some 43 kilometers +(about 27 miles). + +Its circumference is 40,000 kilometers (24,900 miles). This ball is +surrounded by an aerial envelope, the atmosphere, the height of which +can not be less than 300 kilometers (186 miles), according to the +observations made on certain shooting stars. + +We all know that this layer of air, at the bottom of which we live, is a +beautiful azure blue that seems to separate us from the sidereal abyss, +spreading over our heads in a kind of vault that is often filled with +clouds, and giving the illusion of resting far off on the circle of the +horizon. But this is only an illusion. In reality, there is neither +vault nor horizon; space is open in all directions. If the atmosphere +did not exist, or if it were completely transparent, we should see the +stars by day as by night, for they are continually round us, at noon as +at midnight, and we can see them in the full daylight, with the help of +astronomical instruments. In fact, certain stars (the radiant Venus and +the dazzling Jupiter) pierce the veil of the atmosphere, and are visible +with the unaided eye in full daylight. + +The terrestrial surface is 510,000,000 square kilometers (200,000,000 +square miles). The waters of the ocean cover three-quarters of this +surface, _i.e._, 383,200,000 square kilometers (150,000,000 square +miles), and the continents only occupy 136,600,000 square kilometers +(55,000 square miles). France represents about the thousandth part of +the total superficies of the globe. + +Despite the asperities of mountain ranges, and the abysses hollowed out +by the waters, the terrestrial globe is fairly regular, and in relation +to its volume its surface is smoother than that of an orange. The +highest summits of the Himalaya, the profoundest depths of the somber +ocean, do not attain to the millionth part of its diameter. + +In weight, the Earth is five and a half times heavier than would be a +globe of water of the same dimensions. That is to say: + + 6,957,930,000,000,000,000,000,000 kilograms + (6,833,000,000,000,000,000,000 tons). + +The atmospheric atmosphere with which it is surrounded represents. + + 6,263,000,000,000,000,000 kilograms + (6,151,000,000,000,000 tons). + +Each of us carries an average weight of some 17,000 kilograms (16 tons) +upon his shoulders. Perhaps some one will ask how it is that we are not +crushed by this weight, which is out of all proportion with our +strength, but to which, nevertheless, we appear insensible. It is +because the aerial fluid enclosed within our bodies exerts a pressure +equal and opposite to the external atmospheric pressure, and these +pressures are at equilibrium. + +The Earth is characterized by no essential or particular differences +relatively to the other worlds of our system. Like Venus of the limpid +rays, like the dazzling Jupiter, like all the planets, she courses +through space, carrying into Infinitude our hopes and destinies. Bigger +than Mercury, Venus, and Mars, she presents a very modest figure in +comparison with the enormous Jupiter, the strange system of Saturn, of +Uranus, and even of Neptune. For us her greatest interest is that she +serves as our residence, and if she were not our habitation we should +scarcely notice her. Dark in herself, she burns at a distance like a +star, returning to space the light she receives from the Sun. At the +distance of our satellite, she shines like an enormous moon, fourteen +times larger and more luminous than our gentle Phoebe. Observed from +Mercury or Venus, she embellishes the midnight sky with her sparkling +purity as Jupiter does for us. Seen from Mars, she is a brilliant +morning and evening star, presenting phases similar to those which Mars +and Venus show from here. From Jupiter, the terrestrial globe is little +more than an insignificant point, nearly always swallowed up in the +solar rays. As to the Saturnians, Uranians, and Neptunians, if such +people exist, they probably ignore our existence altogether. And in all +likelihood it is the same for the rest of the universe. + +We must cherish no illusions as to the importance of our natal world. It +is true that the Earth is not wanting in charm, with its verdant plains +enameled in the delicious tones of a robust and varied vegetation, its +plants and flowers, its spring-time and its birds, its limpid rivers +winding through the meadows, its mountains covered with forests, its +vast and profound seas animated with an infinite variety of living +creatures. The spectacle of Nature is magnificent, superb, admirable +and marvelous, and we imagine that this Earth fills the universe, and +suffices for it. The Sun, the Moon, the stars, the boundless Heavens, +seem to have been created for us, to charm our eyes and thoughts, to +illumine our days, and shed a gentle radiance upon our nights. This is +an agreeable illusion of our senses. If our Humanity were extinguished, +the other worlds of the Heavens, Venus, Mars, etc., would none the less +continue to gravitate in the Heavens along with our defunct planet, and +the close of human life (for which everything seems to us to have been +created) would not even be perceived by those other worlds, that +nevertheless are our neighbors. There would be no revolution, no +cataclysm. The stars would go on shining in the firmament, just as they +do to-day, shedding their divine light over the immensity of the +Heavens. Nothing would be changed in the general aspect of the Universe. +The Earth is only a modest atom, lost in the innumerable army of the +worlds and suns that people the universe. + + * * * * * + +Every morning the Sun rises in the East, setting fire with his ardent +rays to the sky, which is dazzling with his splendor. He ascends through +space, reaches a culminating point at noon, and then descends toward the +West, to sink at night into the purple of the sunset. + +And then the stars, grand lighthouses of the Heavens, in their turn +incandesce. They too rise in the East, ascend the vault of Heaven, and +then descend to the West, and vanish. All the orbs, Sun, Moon, planets, +stars, appear to revolve round us in twenty-four hours. + +This journey of the orbs around us is only an illusion of the senses. + +Whether the Earth be at rest, and the sky animated with a rotary +movement round her, or whether, on the contrary, the stars are fixed, +and the Earth in motion, in either case, for us appearances are the +same. If the Earth turns, carrying all that pertains to it in its +motion--the seas, the atmosphere, the clouds, and ourselves,--we are +unable to perceive it, because all the objects that surround us keep +their respective positions among themselves. Hence we must resort to +logic, and reason out the two hypotheses. + +For the accomplishment of this rapid journey of the Sun and stars around +the Earth, it would be necessary that all the orbs of the sky should be +in some way attached to a vault, or to circles, as was formerly +supposed. This conception is childish. The peoples of antiquity had no +notion of the size of the universe, and their error is almost excusable. +The distance separating Heaven from the Infernal Regions has been +measured, according to Hesiod, by Vulcan's anvil, which fell from the +skies to the Earth in nine days and nine nights, and it would have +taken as long again to continue its journey from the surface of the +Earth to the bowels of Hades. + +To-day we have a more exact notion of the grandeur of the Universe. We +know that millions and trillions of miles separate the stars from one +another. And by representing these distances, we can form some idea of +the difficulty there would be in admitting the rotation of the universe +round the Earth. + +The distance from here to the Sun is 149,000,000 kilometers (93,000,000 +miles). In order to turn in twenty-four hours round the Earth, that orb +would have to fly through Space at a velocity of more than 10,000 +kilometers (6,200 miles) a second. + +Yes! the Sun, splendid orb, source of our existence and of that of all +the planets, a colossal globe, over a million times more voluminous than +the Earth, and 324 thousand times heavier, would have to accomplish this +immense revolution in order to turn round the minute point that is our +lilliputian world! + +This in itself would suffice to convince us of the want of logic in such +an argument. But the Sun is not alone in the Heavens. We should have to +suppose that all the planets and all the stars were engaged in the same +fantastic motions. + +Jupiter is about five times as far off as the Sun; his velocity would +have to be 53,000 kilometers (32,860 miles) per second. + +Neptune, thirty times farther off, would have to execute 320,000 +kilometers (198,000 miles) per second. + +The nearest star, [alpha] of the Centaur, situated at a distance 275,000 +times that of the Sun, would have to run, to fly through space, at a +rate of 2,941,000,000 kilometers (1,823,420,000 miles) per second. + +All the other stars are incomparably farther off, at infinity. + +And this fantastic rotation would all be accomplished round a minute +point! + +To put the problem in this way is to solve it. Unless we deny the +astronomic measures, and the most convincing geometric operations, the +Earth's diurnal motion of rotation is a certainty. + +To suppose that the stars revolve round the Earth is to suppose, as one +author humorously suggests, that in order to roast a pheasant the +chimney, the kitchen, the house, and all the countryside must needs turn +round it. + +If the Earth turns in twenty-four hours upon itself, a point upon the +equator would simply travel at a rate of 465 meters (1,525 feet) per +second. This speed, while considerable in comparison with the movements +observed upon the surface of our planet, is as nothing compared with +the fantastic rapidity at which the Sun and stars would have to move, in +order to rotate round our globe. + +Thus we have to choose between these two hypotheses: either to make the +entire Heavens turn round us in twenty-four hours, or to suppose our +globe to be animated by a motion of rotation upon itself. For us, the +impression is the same, and as we are insensible to the motion of the +Earth, its immobility would seem almost natural to us. So that, in last +resort, here as in many other instances, the decision must be made by +simple common sense. Science long ago made its choice. Moreover, all the +progress of Astronomy has confirmed the rotary movement of the Earth in +twenty-four hours, and its movement of revolution round the Sun in a +year; while at the same time a great number of other motions have been +discovered for our wandering planet. + +The learned philosophers of antiquity divined the double movement of our +planet. The disciples of Pythagoras taught it more than two thousand +years ago, and the ancient authors quote among others Nicetas of +Syracuse, and Aristarchus of Samos, as being among the first to promote +the doctrine of the Earth's movement. But at that remote period no one +had any idea of the real distances of the stars, and the argument did +not seem to be based on any adequate evidence. Ptolemy, after a long +discussion of the diurnal motion of our planet, refutes it, giving as +his principal reason that if the Earth turned, the objects that were not +fixed to its surface would appear to move in a contrary direction, and +that a body shot into the air would fall back to the West of its +starting-point, the Earth having turned meantime from West to East. This +objection has no weight, because the Earth controls not only all the +objects fixed to the soil, but also the atmosphere, and the clouds that +surround it like a light veil, and all that exists upon its surface. The +atmosphere, the clouds, the waters of the ocean, things and beings, all +are adherent to it and make one body with it, participating in its +movement, as sometimes happens to ourselves in the compartment of a +train, or the car of an aerostat. When, for instance, we drop an object +out of such a car, this object, animated with the acquired velocity, +does not fall to a point below the aerostat, but follows the balloon, as +though it were gliding along a thread. The author has made this +experiment more than once in aerial journeys. + +Thus, the hypothesis of the Earth's motion has become a certainty. But +in addition to reasoning, direct proof is not wanting. + +1. The spheroidal shape of the Earth, slightly flattened at the poles +and swollen at the equator, has been produced by the rotary motion, by +the centrifugal force that it engenders. + +2. In virtue of this centrifugal force, which is at its maximum at the +equator, objects lose a little of their weight in proportion as they are +farther removed from the polar regions where centrifugal force is almost +_nil_. + +3. In virtue of this same centrifugal force, the length of the pendulum +in seconds is shorter at the equator than in Paris, and the difference +is one of 3 millimeters. + +4. A weight abandoned to itself and falling from a certain height, +should follow the vertical if the Earth were motionless. Experiment, +frequently repeated, shows a slight deviation to the East, of the +plumb-line that marks the vertical. We more especially observed this at +the Pantheon during the recent experiments. + +5. The magnificent experiment of Foucault at the Pantheon, just renewed +under the auspices of the Astronomical Society of France, demonstrates +the rotary motion of the Earth to all beholders. A sufficiently heavy +ball (28 kilograms, about 60 pounds) is suspended from the dome of the +edifice by an excessively fine steel thread. When the pendulum is in +motion, a point attached to the bottom of the ball marks its passage +upon two little heaps of sand arranged some yards away from the center. +At each oscillation this point cuts the sand, and the furrow gets +gradually longer to the right hand of an observer placed at the center +of the pendulum. The plane of the oscillations remains fixed, but the +Earth revolves beneath, from West to East. The fundamental principle of +this experiment is that the plane in which any pendulum is made to +oscillate remains invariable even when the point of suspension is +turned. This demonstration enables us in some measure to see the Earth +turning under our feet. + +The annual displacements of the stars are again confirmatory of the +Earth's motion round the Sun. During the course of the year, the stars +that are least remote from our solar province appear to describe minute +ellipses, in perspective, in the Heavens. These small apparent +variations in the position of the nearest stars reproduce the annual +rotation of the Earth round the Sun, in perspective. + +We could adduce further observations in favor of this double movement, +but the proofs just given are sufficiently convincing to leave no doubt +in the mind of the reader. + +Nor are these two the only motions by which our globe is rocked in +space. To its diurnal rotation and its annual rotation we may add +another series of _ten more motions_: some very slow, fulfilling +themselves in thousands of years, others, more rapid, being constantly +renewed. It is, however, impossible in these restricted pages to enter +into the detail reserved for more complete works. We must not forget +that our present aim is to sum up the essentials of astronomical +knowledge as simply as possible, and to offer our readers only the "best +of the picking." + + * * * * * + +The two principal motions of which we have just spoken give us the +measure of time, the day of twenty-four hours, and the year of 365-1/4 +days. + +The Earth turning upon itself in twenty-four hours from West to East, +presents all its parts in succession to the Sun fixed in space. +Illuminated countries have the day, those opposite, in the shadow of the +Earth, are plunged into night. The countries carried by the Earth toward +the Sun have morning, those borne toward his shadow, evening. Those +which receive the rays of the day-star directly have noon; those which +are just opposite have midnight. + +The rotation of our planet in this way gives us the measure of time; it +has been divided arbitrarily into twenty-four periods called hours; each +hour into sixty minutes; each minute into sixty seconds. + +In consequence, each country turns in twenty-four hours round the axis +of the Earth. The difference in hours between the different regions of +the globe is therefore regulated by the difference of geographical +position. The countries situated to the West are behind us; the Sun only +gets there after it has shone upon our meridian. When it is midday in +Paris, it is only 11.51 A.M. in London; 11.36 A.M. in Madrid; 11.14 A.M. +at Lisbon; 11.12 A.M. at Mogador; 7.06 A.M. at Quebec; 6.55 A.M. at New +York; 5.14 A.M. in Mexico; and so on. The countries situated to the East +are, on the contrary, ahead of us. When it is noon in Paris, it is +already 56 minutes after midday at Vienna; 1.25 P.M. at Athens; 2.21 +P.M. at Moscow; 3.16 P.M. at Teheran; 4.42 P.M. at Bombay; and so on. We +are here speaking of real times, and not of the conventional times. + +[Illustration: FIG. 60.--Motion of the Earth round the Sun.] + +If we could make the tour of the world in twenty-four hours, starting +at midday from some place to go round the globe, and traveling westward +with the Sun, we should have him always over our heads. In traveling +round the world from West to East, one goes in front of the Sun, and +gains by one day; in taking the opposite direction, from East to West, +one loses a day. + +In reality, the exact duration of the Earth's diurnal rotation is +twenty-three hours, fifty-six minutes, four seconds. That is the +sidereal day. But, while turning upon itself, the Earth circulates upon +its orbit, and at the end of a diurnal rotation it is still obliged to +turn during three minutes, fifty-six seconds in order to present exactly +the same meridian to the fixed Sun which, in consequence of the rotary +period of our planet, is a little behind. The solar day is thus one of +twenty-four hours. There are 366 rotations in the year. + +And now let us come back to the consequences of the Earth's motion. In +the first place our planet does not turn vertically nor on its side, but +is tipped or inclined a certain quantity: 23° 27'. + +Now, throughout its annual journey round the Sun, the inclination +remains the same. That is what produces the seasons and climates. The +countries which have a larger circle to travel over in the hemisphere of +the solar illumination have the longer days, those which have a smaller +circle, shorter days. At the equator there is constantly, and all +through the year, a twelve-hour day, and a night of twelve hours. + +[Illustration: FIG. 61.--Inclination of the Earth.] + +In summer, the pole dips toward the Sun, and the rays of the orb of day +cover the corresponding hemisphere with their light. Six months later +this same hemisphere is in winter, and the opposite hemisphere is in its +turn presented to the Sun. June 21 is the summer solstice for the +northern hemisphere, and is at the same time winter for the southern +pole. Six months later, on December 21, we have winter, while the +southern hemisphere is completely exposed to the Sun. Between these two +epochs, when the radiant orb shines exactly upon the equator, that is on +March 21, we have the spring equinox, that delicious flowering season +when all nature is enchanting and enchanted; on September 21 we have the +autumn equinox, melancholy, but not devoid of charm. + +The terrestrial sphere has been divided into different zones, with which +the different climates are in relation: + +1. The tropical zone, which extends 23° 27' from one part to the other +of the equator. This is the hottest region. It is limited by the circle +of the tropics. + +2. The temperate zones, which extend from 23° 27' to 66° 23' of +latitude, and where the Sun sets every day. + +3. The glacial zones, drawn round the poles, at 66° 33' latitude, where +the Sun remains constantly above or below the horizon for several days, +or even several months. These glacial zones are limited by the polar +circles. + +We must add that the _axis_ of the Earth is a straight line that is +supposed to pass through the center of the globe and come out at two +diametrically opposite points called the _poles_. The diurnal rotation +of the Earth is effected round this axis. + +The name _equator_ is given to a great circle situated between the two +poles, at equal distance, which divides the globe into two hemispheres. +The equator is divided into 360 parts or degrees, by other circles that +go from one pole to the other. These are the _longitudes_ or meridians +(see Fig. 62). The distance between the equator and the pole is divided +into larger or smaller circles, which have received the name of +_latitudes_, 90 degrees are reckoned on the one side and the other of +the equator, in the direction of the North and South poles, +respectively. The longitudes are reckoned from some point either to East +or West: the latitudes are reckoned North and South, from the equator. +In going from East to West, or inversely, the longitude changes, but in +passing from North to South of any spot, it is the latitude that alters. + +[Illustration: FIG. 62.--The divisions of the globe. Longitudes and +latitudes.] + +The circles of latitude are smaller in proportion as one approaches the +poles. The circumference of the world is 40,076,600 meters at the +equator. At the latitude of Paris (48° 50') it is only 26,431,900 +meters. A point situated at the equator has more ground to travel over +in order to accomplish its rotation in twenty-four hours than a point +nearer the pole. + +We have already stated that this velocity of rotation is 465 meters per +second at the equator. At the latitude of Paris it is not more than 305 +meters. At the poles it is _nil_. + +The longitudes, or meridians, are great circles of equal length, +dividing the Earth into quarters, like the parts of an orange or a +melon. These circumvent the globe, and measure some 40,000,000 +(40,008,032) meters. We may remember in passing that the length of the +meter has been determined as, by definition, the ten-millionth part of +the quarter of a celestial meridian. + +Thus, while rotating upon itself, the Earth spins round the Sun, along a +vast orbit traced at 149,000,000 kilometers (93,000,000 miles) from the +central focus, a sensibly elliptical orbit, as we have already pointed +out. It is a little nearer the Sun on January 1st than on July 1st, at +its perihelion (_peri_, near, _helios_, Sun), than at its aphelion +(_apo_, far, _helios_, Sun). The difference = 6,000,000 kilometers +(3,720,000 miles), and its velocity is a little greater at perihelion +than at aphelion. + +This second motion produces the _year_. It is accomplished in three +hundred and sixty-five days, six hours, nine minutes, nine seconds. +Such is the complete revolution of our planet round the orb of day. It +has received the name of sidereal year. But this is not how we calculate +the year in practical life. The civil year, known also as the tropical +year, is not equivalent to the Earth's revolution, because a very slow +gyratory motion, called "the precession of the equinoxes," the cycle of +which occupies 25,765 years, drags the spring equinox back some twenty +minutes in each year. + +The civil year is, accordingly, three hundred and sixty-five days, five +hours, forty-eight minutes, forty-six seconds. + +In order to simplify the calendar, this accumulating fraction of five +hours, forty-eight minutes, forty-six seconds (about a quarter day) is +added every four years to a bissextile year (leap-year), and thus we +have uneven years of three hundred and sixty-five, and three hundred and +sixty-six days. Every year of which the figure is divisible by four is a +leap-year. By adding a quarter day to each year, there is a surplus of +eleven minutes, fourteen seconds. These are subtracted every hundred +years by not taking as bissextile those secular years of which the +radical is not divisible by four. The year 1600 was leap-year: 1700, +1800, and 1900 were not; 2000 will be. The agreement between the +calendar and nature has thus been fairly perfect, since the +establishment of the Gregorian Calendar in 1582. + +Since the terrestrial orbit measures not less than 930,000,000 +kilometers (576,600,000 miles), which must be traversed in a year, the +Earth flies through Space at 2,544,000 kilometers (1,577,280 miles) a +day, or 106,000 kilometers (65,720 miles) an hour, or 29,500 meters (18 +miles) per second on an average, a little faster at perihelion, a little +slower at aphelion. This giddy course, a thousand times more rapid than +the speed of an express-train, is effected without commotion, shock, or +noise. Reasoning alone enables us to divine the prodigious movement that +carries us along in the vast fields of the Infinite, in mid-heaven. + +Returning to the calendar, it must be remarked in conclusion, that the +human race has not exhibited great sense in fixing the New Year on +January 1. No more disagreeable season could have been selected. And +further, as the ancient Roman names of the months have been preserved, +which in the time of Romulus began with March, the "seventh" month, +"September," is our ninth month; October (the eighth) is the tenth; +November (the ninth) has become the eleventh; and December (the tenth) +has taken the place of the twelfth. Verily, we are not hard to please! + +These months, again, are unequal, as every one knows. Witness the +simple expedient of remembering the long and short months, by closing +the left hand and counting the knobs and hollows of the fist, the former +corresponding to the long months, the latter to the short: first knob = +January; first hollow, February; second knob, March; and so on.[12] + +[Illustration: FIG. 63.--To find the long and short months.] + +Should not the real renewal of the year coincide with the awakening of +Nature, with the spring on the terrestrial hemisphere occupied by the +greater portion of Humanity, with the date of March 21st? Should not the +months be equalized, and their names modified? Why should we not follow +the beautiful evolution dictated by the Sun and by the movement of our +planet? But our poor Earth may roll on a long time yet before its +inhabitants will become reasonable. + + + + +CHAPTER IX + +THE MOON + + +It is the delightful hour when all Nature pauses in the tranquil calm of +the silent night. + +The Sun has cast his farewell gleams upon the weary Earth. All sound is +hushed. And soon the stars will shine out one by one in the bosom of the +somber firmament. Opposite to the sunset, in the east, the Full Moon +rises slowly, as it were calling our thoughts toward the mysteries of +eternity, while her limpid night spreads over space like a dew from +Heaven. + +In the odorous woods, the trees are silhouetted strangely upon the sky, +seeming to stretch their knotted arms toward this celestial beauty. On +the river, smooth as a mirror, wherein the pale Phoebe reflects her +splendor, the maidens go to seek the floating image of their future +spouse. And in response to their prayers, she rends the veil of cloud +that hides her from their eyes, and pours the reflection of her gentle +beams upon the sleeping waters. + +From all time the Moon has had the privilege of charming the gaze, and +attracting the particular attention of mortals. What thoughts have not +been wafted to her pale, yet luminous disk? Orb of mystery and of +solitude, brooding over our silent nights, this celestial luminary is at +once sad and splendid in her glacial purity, and her limpid rays provoke +a reverie full of charm and melancholy. Mute witness of terrestrial +destinies, her nocturnal flame watches over our planet, following it in +its course as a faithful satellite. + +The human eye first uplifted to the Heavens was struck, above all, with +the brilliancy of this solitary globe, straying among the stars. The +Moon first suggested an easy division of time into months and weeks, and +the first astronomical observations were limited to the study of her +phases. + +Daughter of the Earth, the Moon was born at the limits of the +terrestrial nebula, when our world was still no more than a vast gaseous +sphere, and was detached from her at some critical period of colossal +solar tide. Separating with regret from her cradle, but attached to the +Earth by indissoluble ties of attraction, she rotates round us in a +month, from west to east, and this movement keeps her back a little each +day in relation to the stars. If we watch, evening by evening, beginning +from the new moon, we shall observe that she is each night a little +farther to the left, or east, than on the preceding evening. This +revolution of the Moon around our planet produces the phases, and gives +the measure of our months. + +[Illustration: FIG. 64.--The Full Moon slowly rises.] + +During her monthly journey she always presents the same face to us. One +might think that the fear of losing us had immobilized her globe, and +prevented her from turning. And so we only know of her the vague sketch +of a human face that has been observed through all the ages. + +It seems, in fact, as though she were looking down upon us from the +Heavens, the more so as the principal spots of her disk vaguely recall +the aspect of a face. If we try to draw it without the aid of +instruments we observe dark regions and clear regions that each +interprets in his own fashion. To the author, for instance, the full +Moon has the appearance represented in the following figure. The spots +resemble two eyes and the sketch of a nose; resulting in a vague human +figure, as indicated on the lower disk. Others see a man carrying a +bundle of wood, a hare, a lion, a dog, a kangaroo, a sickle, two heads +embracing, etc.[13] But generally speaking, there is a tendency to see a +human figure in it. + +If this appearance is helped a little by drawing, it gives the profile +of a man's head fairly well sketched, and furnished with an abundant +crop of hair (Fig. 66). Others go much more into detail, and draw a +woman's head that is certainly too definite, like this of M. Jean Sardou +(Fig. 67). Others, again, like M. Zamboni, see behind the man's profile +the likeness of a young girl being embraced by him (Fig. 68). There is +certainly some imagination about these. And yet, on the first suitable +occasion, look at the Moon through an opera-glass, a few days after the +first quarter, and you will not fail to see the masculine profile just +described, and even to imagine the "kiss in the Moon." + +[Illustration: FIG. 65.--The Moon viewed with the unaided eye.] + +[Illustration: FIG. 66.--The Man's head in the Moon.] + +These vague aspects disappear as soon as the Moon is examined with even +the least powerful instruments: the spots are better defined, and the +illusions of indistinct vision vanish. Compare this direct photograph of +the Moon, taken by the author some years ago (Fig. 69): here is neither +a human figure, man, dog, hare, nor faggot; simply deep geographical +configurations, and in the lower region, a luminous point whence certain +light bands spread out, some being prolonged to a considerable distance. +And yet, from a little way off, does it not form the man's face above +indicated? + +[Illustration: FIG. 67.--Woman's head in the Moon.] + +From the earliest astronomical observations made with the aid of +instruments by Galileo, in 1609, people tried to find out what the dark +spots could represent, and they were called seas, because water absorbs +light, and reflects it less than _terra firma_. The Moon of itself +possesses no intrinsic light, any more than our planet, and only shines +by the light of the Sun that illuminates it. As it rotates round the +Earth, and constantly changes its position with respect to the Sun, we +see more or less of its illuminated hemisphere, and the result is the +phases that every one knows so well. + +[Illustration: FIG. 68.--The kiss in the Moon.] + +[Illustration: FIG. 69.--Photograph of the Moon.] + +At the commencement of each lunation, the Moon is between the Sun and +the Earth, and its non-illuminated hemisphere is turned toward us. This +is the New Moon, invisible to us; but two days later, the slim crescent +of Diana sheds a gentle radiance upon the Earth. Gradually the crescent +enlarges. When the Moon arrives at right angles with ourselves and with +the Sun, half the illuminated hemisphere is presented to us. This is the +first quarter. At the time of Full Moon, it is opposite the Sun, and we +see the whole of the hemisphere illuminated. Then comes the decline: the +brilliant disk is slightly corroded at first; it diminishes from day to +day, and about a week before the New Moon our fair friend only shows her +profile before she once more passes in front of the Sun: this is the +last quarter. + +[Illustration: FIG. 70.--The Moon's Phases.] + +When the Moon is crescent, in the first evenings of the lunation, and +after the last quarter, the rest of the disk is visible, illuminated +feebly by a pale luminosity. This is known as the ashy light. It is due +to the shine of the Earth, reflecting the light received from the Sun +into space. Accordingly the ashy light is the reflection of our own sent +back to us by the Moon. It is the reflection of a reflection. + +This rotation of the Moon round the Earth is accomplished in +twenty-seven days, seven hours, forty-three minutes, eleven seconds; but +as the Earth is simultaneously revolving round the Sun, when the Moon +returns to the same point (the Earth having become displaced relatively +to the Sun), the Moon has to travel two days longer to recover its +position between the Sun and the Earth, so that the lunar month is +longer than the sidereal revolution of the Moon, and takes twenty-nine +days, twelve hours, forty-four minutes, three seconds. This is the +duration of the sequence of phases. + +This revolution is accomplished at a distance of 384,000 kilometers +(238,000 miles). The velocity of the Moon in its orbit is more than 1 +kilometer (0.6214 mile) per second. But our planet sweeps it through +space at a velocity almost thirty times greater. + +The diameter of the Moon represents 273/1000 that of the Earth, _i.e._, +3,480 kilometers (2,157 miles). + +Its surface = 38,000,000 square kilometers (15,000,000 square miles), a +little more than the thirteenth part of the terrestrial surface, which += 510,000,000 (200,000,000 square miles). + +In volume, the Moon is fifty times less than the Earth. Its mass or +weight is only 1/81 that of the terrestrial globe. Its density = 0.615, +relatively to that of the Earth, _i.e._, a little more than three times +that of water. Weight at its surface is very little: 0.174. A kilogram +transported thither would only weigh 174 grams. + + * * * * * + +At the meager distance of 384,000 kilometers (238,000 miles) that +separates us from it (about thirty times the diameter of the Earth), the +Moon is a suburb of our terrestrial habitation. What does this small +distance amount to? It is a mere step in the universe. + +A telegraphic message would get there in one and a half second; a +projectile fired from a gun would arrive in eight days, five hours; an +express-train would be due in eight months, twenty-two days. It is only +the 1/388 part of the distance that separates us from the Sun, and only +the 100/1,000,000 part of the distance of the stars nearest to us. Many +men have tramped the distance that separates us from the Moon. A bridge +of thirty terrestrial globes would suffice to unite the two worlds. + +Owing to this great proximity, the Moon is the best known of all the +celestial spheres. Its geographical (or more correctly, +selenographical, _Selene_, moon) map was drawn out more than two +centuries ago, at first in a vague sketch, and afterward with more +details, until to-day it is as precise and accurate as any of our +terrestrial maps of geography. + +Before the invention of the telescope, from antiquity to the seventeenth +century, people lost themselves in conjectures as to the nature of this +strange lunar figure. It was held to be a mysterious world, the more +extraordinary in that it always presented the same face to us. Some +compared it to an immense mirror reflecting the image of the Earth. +Others pictured it as a silver star, an enchanted abode where all was +wealth and happiness. For many a long day it was the fashion to think, +quite irrationally, that the inhabitants of the Moon were fifteen times +bigger than ourselves. + +The invention of telescopes, however, brought a little order and a grain +of truth into these fantastic assumptions. The first observations of +Galileo revolutionized science, and his discoveries filled the +best-ordered minds with enthusiasm. Thenceforward, the Moon became our +property, a terrestrial suburb, where the whole world would gladly have +installed itself, had the means of getting there been as swift as the +wings of the imagination. It became easy enough to invent a thousand +enchanting descriptions of the charms of our fair sister, and no one +scrupled to do so. Soon, it was observed that the Moon closely resembled +the Earth in its geological features; its surface bristles with sharp +mountain peaks that light up in so many luminous points beneath the rays +of the Sun. Alongside, dark and shaded parts indicate the plains; +moreover, there are large gray patches that were supposed to be seas +because they reflect the solar light less perfectly than the adjacent +countries. At that epoch hardly anything was known of the physical +constitution of the Moon, and it was figured as enveloped with an +atmospheric layer, analogous to that at the bottom of which we carry on +our respiration. + +To-day we know that these "seas" are destitute of water, and that if the +lunar globe possesses an atmosphere, it must be excessively light. + +The Moon became the favorite object of astronomers, and the numerous +observations made of it authorized the delineation of very interesting +selenographic charts. In order to find one's way among the seas, plains, +and mountains that make up the lunar territory, it was necessary to name +them. The seas were the first to be baptized, in accordance with their +reputed astrological influences. Accordingly, we find on the Moon, the +Sea of Fecundity, the Lake of Death, the Sea of Humors, the Ocean of +Tempests, the Sea of Tranquillity, the Marsh of Mists, the Lake of +Dreams, the Sea of Putrefaction, the Peninsula of Reverie, the Sea of +Rains, etc. + +With regard to the luminous parts and the mountains, it was at first +proposed to call them after the most illustrious astronomers, but the +fear of giving offense acted as a check on Hevelius and Riccioli, +authors of the first lunar maps (1647, 1651), and they judged it more +prudent to transfer the names of the terrestrial mountains to the Moon. +The Alps, the Apennines, the Pyrenees, the Carpathians, are all to be +found up there; then, as the vocabulary of the mountains was not +adequate, the scientists reasserted their rights, and we meet in the +Moon, Aristotle, Plato, Hipparchus, Ptolemy, Copernicus, Kepler, Newton, +as well as other more modern and even contemporaneous celebrities. + +We have not space to reproduce the general chart of the Moon (that +published by the author measures not less than a meter, with the +nomenclature); but the figure subjoined gives a summary sufficient for +the limits of this little book. Here are the names of the principal +lunar mountains, with the numbers corresponding to them upon the map. + +[Illustration: FIG. 71.--Map of the Moon. + +(From Fowler's "Telescopic Astronomy.") + + 1 Furnerius + 2 Petavius + 3 Langrenus + 4 Macrobius + 5 Cleomedes + 6 Endymion + 7 Altas + 8 Hercules + 9 Romer + 10 Posidonius + 11 Fracastorius + 12 Theophilus + 13 Piccolomini + 14 Albategnius + 15 Hipparchus + 16 Manilius + 17 Eudoxus + 18 Aristotle + 19 Cassini + 20 Aristillus + 21 Plato + 22 Archimedes + 23 Eratosthenes + 24 Copernicus + 25 Ptolemy + 26 Alphonsus + 27 Arzachel + 28 Walter + 29 Clavius + 30 Tycho + 31 Bullialdus + 32 Schiller + 33 Schickard + 34 Gassendi + 35 Kepler + 36 Grimaldi + 37 Aristarchus + + A Mare Crisum + B Mare Fercunditatis + C Mare Nectaris + D Mare Tranquilitatis + E Mare Serenitatis + F Mare Imbrium + G Sinus Iridum + H Oceanus Procellarum + I Mare Humorum + K Mare Nubium + V Altai Mountains + W Mare Vaporum + X Apennine Mountains + Y Caucasus Mountains + Z Alps] + +The constantly growing progress of optics leads to perpetual new +discoveries in science, and at the present time we can say that we know +the geography of the Moon as well as, and even better than, that of our +own planet. The heights of all the mountains of the Moon are measured to +within a few feet. (One cannot say as much for the mountains of the +Earth.) The highest are over 7,000 meters (nearly 25,000 feet). +Relatively to its proportions, the satellite is much more mountainous +than the planet, and the plutonian giants are much more numerous there +than here. If we have peaks, like the Gaorisankar, the highest of the +Himalayas and of the whole Earth, whose elevation of 8,840 meters +(29,000 feet) is equivalent to 1/1140 the diameter of our globe, there +are peaks on the Moon of 7,700 meters (25,264 feet), _e.g._, those of +Doerfel and Leibniz, the height of which is equivalent to 1/470 the +lunar diameter. + +Tycho's Mountain is one of the finest upon our satellite. It is visible +with the naked eye (and perfectly with opera-glasses) as a white point +shining like a kind of star upon the lower portion of the disk. At the +time of full moon it is dazzling, and projects long rays from afar upon +the lunar globe. So, too, Mount Copernicus, whose brilliant whiteness +sparkles in space. But the strangest thing about these lunar mountains +is that they are all hollow, and can be measured as well in depth as in +height. A type of mountain as strange to us as are the seas without +water! In effect, these mountains of the moon are ancient volcanic +craters, with no summits, nor covers. + +At the top of the highest peaks, there is a large circular depression, +prolonged into the heart of the mountain, sometimes far below the level +of the surrounding plains, and as these craters often measure several +hundred kilometers, one is obliged, if one does not want to go all round +them in crossing the mountain, to descend almost perpendicularly into +the depths and cross there, to reascend the opposite side, and return to +the plain. These alpine excursions incontestably deserve the name of +perilous ascents! + +No country on the Earth can give us any notion of the state of the lunar +soil: never was ground so tormented; never globe so profoundly shattered +to its very bowels. The mountains are accumulations of enormous rocks +tumbled one upon the other, and round the awful labyrinth of craters one +sees nothing but dismantled ramparts, or columns of pointed rocks like +cathedral spires issuing from the chaos. + +As we said, there is no atmosphere, or at least so little at the bottom +of the valleys that it is imperceptible. No clouds, no fog, no rain nor +snow. The sky is an eternally black space, vaultless, jeweled with stars +by day as by night. + +Let us suppose that we arrive among these savage steppes at daybreak: +the lunar day is fifteen times longer than our own, because the Sun +takes a month to illuminate the entire circuit of the Moon; there are no +less than 354 hours from the rising to the setting of the Sun. If we +arrive before the sunrise, there is no aurora to herald it, for in the +absence of atmosphere there can be no sort of twilight. Of a sudden on +the dark horizon come flashes of the solar light, striking the summits +of the mountains, while the plains and valleys are still in darkness. +The light spreads slowly, for while on the Earth in central latitudes +the Sun takes only two minutes and a quarter to rise, on the Moon it +takes nearly an hour, and in consequence the light it sends out is very +weak for some minutes, and increases excessively slowly. It is a kind of +aurora, but lasts a very short time, for when at the end of half an +hour, the solar disk has half risen, the light appears as intense to the +eye as when it is entirely above the horizon; the radiant orb is seen +with its protuberances and its burning atmosphere. It rises slowly, like +a luminous god, in the depths of the black sky, a profound and formless +sky in which the stars shine all day, since they are not hidden by any +atmospheric veil such as conceals them from us during the daylight. + +[Illustration: FIG. 72.--The Lunar Apennines.] + +The absence of sensible atmosphere must produce an effect on the +temperature of the Moon analogous to that perceived on the high +mountains of our globe, where the rarefaction of the air does not permit +the solar heat to concentrate itself upon the surface of the soil, as it +does below the atmosphere, which acts as a forcing-house: the Sun's heat +is not kept in by anything, and incessantly radiates out toward space. +In all probability the cold is extremely and constantly rigorous, not +only during the nights, which are fifteen times longer than our own, but +even during the long days of sunshine. + +We give two different drawings to represent these curious aspects of +lunar topography. The first (Fig. 72) is taken in the neighborhood of +the Apennines, and shows a long chain of mountains beneath which are +three deep rings, Archimedes, Aristillus, and Autolycus: the second +(Fig. 73) depicts the lunar ring of Flammarion,[14] whose outline is +constructed of dismantled ramparts, and whose depths are sprinkled with +little craters. The first of these two drawings was made in England by +Nasmyth, the second in Germany by Krieger: they both give an exact idea +of what one sees in the telescope with different modes of solar +illumination. + +In the Moon's always black and starry sky a majestic star that is not +visible from the Earth, and exhibits this peculiarity that it is +stationary in the Heavens, while all the others pass behind it, may +constantly be admired, by day as well as by night; and it is also of +considerable apparent magnitude. This orb, some four times as large as +the Moon in diameter, and thirteen to fourteen times more extensive in +surface, is our Earth, which presents to the Moon a sequence of phases +similar to those which our satellite presents to us, but in the inverse +direction. At the moment of New Moon, the Sun fully illuminates the +terrestrial hemisphere turned toward our satellite, and we get "Full +Earth"; at the time of Full Moon, on the contrary, the non-illuminated +hemisphere of the Earth is turned toward the satellite, and we get "New +Earth": when the Moon shows us first quarter, the Earth is in last +quarter, and so on. The drawing subjoined gives an idea of these +aspects. + +[Illustration: FIG. 73.--Flammarion's Lunar Ring.] + +What a curious sight our globe must be during this long night of +fourteen times twenty-four hours! Independent of its phases, which bring +it from first quarter to full earth for the middle of the night, and +from full earth to last quarter for sunrise, how interested we should be +to see it thus stationary in the sky, and turning on itself in +twenty-four hours. + +[Illustration: FIG. 74.--Lunar landscape with the Earth in the sky.] + +Yes, thanks to us, the inhabitants of the lunar hemisphere turned toward +us are gratified by the sight of a splendid nocturnal torch, doubtless +less white than our own despite the clouds with which the terrestrial +globe is studded, and shaded in a tender tone of bluish emerald-green. +The royal orb of their long nights, the Earth, gives them moonlight of +unparalleled beauty, and we may say without false modesty that our +presence in the lunar sky must produce marvelous and absolutely +fairy-like effects. + +Maybe, they envy us our globe, a dazzling dwelling-place whose splendor +radiates through space; they see its greenish clarity varying with the +extent of cloud that veils its seas and continents, and they observe its +motion of rotation, by which all the countries of our planet are +revealed in succession to its admirers. + +We are talking of these pageants seen from the Moon, and of the +inhabitants of our satellite as if they really existed. The sterile and +desolate aspect of the lunar world, however, rather brings us to the +conclusion that such inhabitants are non-existent, although we have no +authorization for affirming this. That they have existed seems to me +beyond doubt. The lunar volcanoes had a considerable activity, in an +atmosphere that allowed the white volcanic ashes to be carried a long +way by the winds, figuring round the craters the stellar rays that are +still so striking. These cinders were spread over the soil, preserving +all its asperities of outline, a little heaped up on the side to which +they were impelled. The magnificent photographs recently made at the +Paris Observatory by MM. Loewy and Puiseux are splendid evidence of +these projections. In this era of planetary activity there were liquids +and gases on the surface of the lunar globe, which appear subsequently +to have been entirely absorbed. Now the teaching of our own planet is +that Nature nowhere remains infertile, and that the production of Life +is a law so general and so imperious that life develops at its own +expense, sooner than abstain from developing. Accordingly, it is +difficult to suppose that the lunar elements can have remained inactive, +when only next door they exhibited such fecundity upon our globe. Yes, +the Moon has been inhabited by beings doubtless very different from +ourselves, and perhaps may still be, although this globe has run through +the phases of its astral life more rapidly than our own, and the +daughter is relatively older than the mother. + +The duration of the life of the worlds appears to have been in +proportion with their masses. The Moon cooled and mineralized more +quickly than the Earth. Jupiter is still fluid. + +The progress of optics brings us already very close to this neighboring +province. 'Tis a pity we can not get a little nearer! + +A telescopic magnification of 2,000 puts the Moon at 384,000/2000 or 192 +kilometers (some 120 miles) from our eye. Practically we can obtain no +more, either from the most powerful instruments, or from photographic +enlargements. Sometimes, exceptionally, enlargements of 3,000 can be +used. This = 384000/3000 or 128 kilometers (some 80 miles). Undoubtedly, +this is an admirable result, which does the greatest honor to human +intelligence. But it is still too far to enable us to determine anything +in regard to lunar life. + +Any one who likes to be impressed by grand and magnificent sights may +turn even a modest field-glass upon our luminous satellite, at about +first quarter, when the relief of its surface, illuminated obliquely by +the Sun, is at its greatest value. If you examine our neighbor world at +this period, for choice at the hour of sunset, you will be astonished at +its brilliancy and beauty. Its outlines, its laces, and embroideries, +give the image of a jewel of shining silver, translucent, fluid, +palpitating in the ether. Nothing could be more beautiful, nothing +purer, and more celestial, than this lunar globe floating in the silence +of space, and sending back to us as in some fairy dream the solar +illumination that floods it. But yesterday I received the same +impression, watching a great ring half standing out, and following the +progress of the Sun as it mounted the lunar horizon to touch these +silvered peaks. And I reflected that it is indeed inconceivable that +999,999/1,000,000 of the inhabitants of our planet should pass their +lives without ever having attended to this pageant, nor to any of those +others which the divine Urania scatters so profusely beneath the +wondering gaze of the observers of the Heavens. + + + + +CHAPTER X + +THE ECLIPSES + + +Among all the celestial phenomena at which it may be our lot to assist +during our contemplation of the universe, one of the most magnificent +and imposing is undoubtedly that which we are now going to consider. + +The hirsute comets, and shooting stars with their graceful flight, +captivate us with a mysterious and sometimes fantastic attraction. We +gladly allow our thoughts, mute questioners of the mysteries of the +firmament, to rest upon the brilliant, golden trail they leave behind +them. These unknown travelers bring a message from eternity; they tell +us the tale of their distant journeys. Children of space, their ethereal +beauty speaks of the immensity of the universe. + +The eclipses, on the other hand, are phenomena that touch us more +nearly, and take place in our vicinity. + +In treating of them, we remain between the Earth and the Moon, in our +little province, and witness the picturesque effects of the combined +movements of our satellite around us. + +Have you ever seen a total eclipse of the Sun? + +The sky is absolutely clear: no fraction of cloud shadows the solar +rays. The azure vault of the firmament crowns the Earth with a dome of +dazzling light. The fires of the orb of day shed their beneficent +influence generally upon the world. + +Yet, see! The radiance diminishes. The luminous disk of the Sun is +gradually corroded. Another disk, as black as ink, creeps in front of +it, and little by little invades it entirely. The atmosphere takes on a +wan, sepulchral hue; astonished nature is hushed in profound silence; an +immense veil of sadness spreads over the world. Night comes on suddenly, +and the stars shine out in the Heavens. It seems as though by some +mysterious cataclysm the Sun had disappeared forever. But this +tribulation is soon over. The divine orb is not extinct. A flaming jet +emerges from the shadow, announcing his return, and when he reappears we +see that he has lost nothing in splendor or beauty. He is still the +radiant Apollo, King of Day, watching over the life of the planetary +worlds. + +This sudden night, darkening the Heavens in the midst of a fine day, can +not fail to produce a vivid impression upon the spectators of the superb +phenomenon. + +The eclipse lasts only for a few moments, but long enough to make a deep +impression upon our minds, and indeed to inspire anxious spirits with +terror and agitation--even at this epoch, when we know that there is +nothing supernatural or formidable about it. + +In former days, Humanity would have trembled, in uneasy consternation. +Was it a judgment from Heaven? Must it not be the work of some invisible +hand throwing the somber veil of night over the celestial torch? + +Had not the Earth strayed off her appointed path, and were we not all to +be deprived eternally of the light of our good Sun? Was some monstrous +dragon perhaps preparing to devour the orb of day? + +The fable of the dragon devouring the Sun or Moon during the eclipses is +universal in Asia as in Africa, and still finds acceptance under more +than one latitude. But our readers already know that we may identify the +terrible celestial dragon with our gentle friend the Moon, who would not +be greatly flattered by the comparison. + +We saw in the preceding lesson that the Moon revolves round us, +describing an almost circular orbit that she travels over in about a +month. In consequence of this motion, the nocturnal orb is sometimes +between the Sun and the Earth, sometimes behind us, sometimes at a right +angle in relation to the Sun and the Earth. Now, the eclipses of the Sun +occur invariably at the time of New Moon, when our satellite passes +between the Sun and ourselves, and the eclipses of the Moon, at the +moment of Full Moon, when the latter is opposite to the Sun, and behind +us. + +This fact soon enabled the astronomers of antiquity to discover the +causes to which eclipses are due. + +The Moon, passing at the beginning of its revolution between the Sun and +the Earth, may conceal a greater or lesser portion of the orb of day. In +this case there is an eclipse of the Sun. On the other hand, when it is +on the other side of the Earth in relation to the Sun, at the moment of +Full Moon, our planet may intercept the solar rays, and prevent them +from reaching our satellite. The Moon is plunged into _the shadow of the +Earth_, and is then eclipsed. Such is the very simple explanation of the +phenomenon. But why is there not an eclipse of the Sun at each New Moon, +and an eclipse of the Moon at each Full Moon? + +If the Moon revolved round us in the same plane as the Earth round the +Sun, it would eclipse the Sun at each New Moon, and would be itself +eclipsed in our shadow at each Full Moon. But the plane of the lunar +orbit dips a little upon the plane of the terrestrial orbit, and the +eclipses can only be produced when the New Moon or the Full Moon occur +at the line of intersection of these two planes, _i.e._, when the Sun, +the Moon, and the Earth are upon the same straight line. In the majority +of cases, instead of interposing itself directly in front of the +sovereign of our system, our satellite passes a little above or a little +below him, just as its passage behind us is nearly always effected a +little above or below the cone of shadow that accompanies our planet, +opposite the Sun. + +When the Moon intervenes directly in front of the Sun, she arrests the +light of the radiant orb, and conceals a greater or less portion of the +solar disk. The eclipse is partial if the Moon covers only a portion of +the Sun; total if she covers it entirely; annular, if the solar disk is +visible all round the lunar disk, as appears when the Moon, in her +elliptical orbit, is beyond medium distance, toward the apogee. + +On the other hand, when the Moon arrives immediately within the cone of +shadow that the Earth projects behind it, it is her turn to be eclipsed. +She no longer receives the rays of the Sun, and this deprivation is the +more marked in that she owes all her brilliancy to the light of the orb +of day. The Moon's obscurity is complete if she is entirely plunged into +the cone of shadow. In this case, the eclipse is total. But if a portion +of her disk emerges from the cone, that part remains illuminated while +the light of the other dies out. In that case there is a partial +eclipse, and the rounded form of the Earth's shadow can be seen +projected upon our satellite, a celestial witness to the spherical +nature of our globe. + +Under certain conditions, then, the Moon can deprive us of the luminous +rays of the Sun, by concealing the orb of day, and in other cases is +herself effaced in crossing our shadow. Despite the fables, fears, and +anxieties it has engendered, this phenomenon is perfectly natural: the +Moon is only playing hide-and-seek with us--a very harmless amusement, +as regards the safety of our planet. + +But as we said just now, these phenomena formerly had the power of +terrifying ignorant mortals, either when the orb of light and life +seemed on the verge of extinction, or when the beautiful Phoebus was +covered with a veil of crape and woe, or took on a deep coppery hue. + +It would take a volume to describe all the notable events which have +been influenced by eclipses, sometimes for good, more often with +disastrous consequences. The recital of these tragic stories would not +be devoid of interest; it would illustrate the possibilities of +ignorance and superstition, and the power man gains from intellectual +culture and scientific study. + +Herodotus records that the Scythians, having some grievance against +Cyaxarus, King of the Medes, revenged themselves by serving up the limbs +of one of his children, whom they had murdered, at a banquet as rare +game. The scoundrels who committed this atrocious crime took refuge at +the Court of the King of Lydia, who was ill judged enough to protect +them. War was accordingly declared between the Medes and Lydians, but a +total eclipse of the Sun occurring just when the battle was imminent, +had the happy effect of disarming the combatants, who prudently retired +each to their own country. This eclipse, which seems to have occurred on +May 28, 584 B.C., had been predicted by Thales. The French painter +Rochegrosse has painted a striking picture of the scene (Fig. 75). + +In the year 413 B.C. the Athenian General Nicias prepared to return to +Greece after an expedition to Sicily. But, terrified by an eclipse of +the Moon, and fearing the malign influence of the phenomenon, he put off +his departure, and lost the chance of retreat. This superstition cost +him his life. The Greek army was destroyed, and this event marks the +commencement of the decadence of Athens. + +In 331 B.C. an eclipse of the Moon disorganized the troops of Alexander, +near Arbela, and the great Macedonian Captain had need of all his +address to reassure his panic-stricken soldiers. + +Agathocles, King of Syracuse, blocked by the Carthaginians in the port +of this city, had the good fortune to escape, but was disturbed on the +second day of his flight by the arrival of a total eclipse of the Sun +which alarmed his companions. "What are you afraid of?" said he, +spreading his cloak in front of the Sun. "Are you alarmed at a shadow?" +(This eclipse seems to be that of August 15, 309, rather than that of +March 2, 310.) + +[Illustration: FIG. 75.--Battle between the Medes and Lydians arrested +by an Eclipse of the Sun.] + +On June 29, 1033, an epoch at which the approaching end of the world +struck terror into all hearts, an annular eclipse of the Sun occurring +about midday frustrated the designs of a band of conspirators who +intended to strangle the Pope at the altar. This Pope was Benedict IX, a +youth of less than twenty, whose conduct is said to have been anything +but exemplary. The assassins, terrified at the darkening of the Sun, +dared not touch the Pontiff, and he reigned till 1044.[15] + +On March 1, 1504, a lunar eclipse saved the life of Christopher +Columbus. He was threatened with death by starvation in Jamaica, where +the contumacious savages refused to give him provisions. Forewarned of +the arrival of this eclipse by the astronomical almanacs, he threatened +to deprive the Caribs of the light of the Moon--and kept his word. The +eclipse had hardly begun when the terrified Indians flung themselves at +his feet, and brought him all that he required. + +In all times and among all people we find traces of popular +superstitions connected with eclipses. Here, the abnormal absence of the +Moon's light is regarded as a sign of divine anger: the humble penitents +betake themselves to prayer to ward off the divine anger. There, the +cruelty of the dread dragon is to be averted: he must be chased away by +cries and threats, and the sky is bombarded with shots to deliver the +victim from his monstrous oppressor. + +In France the announcement of a solar eclipse for August 21, 1560, so +greatly disturbed our ancestors' peace of mind as to make them idiotic. +Preparations were made for assisting at an alarming phenomenon that +threatened Humanity with deadly consequences! The unhappy eclipse had +been preceded by a multitude of ill omens! Some expected a great +revolution in the provinces and in Rome, others predicted a new +universal deluge, or, on the other hand, the conflagration of the world; +the most optimistic thought the air would be contaminated. To preserve +themselves from so many dangers, and in accordance with the physicians' +orders, numbers of frightened people shut themselves up in tightly +closed and perfumed cellars, where they awaited the decrees of Fate. The +approach of the phenomenon increased the panic, and it is said that one +village _curé_, being unable to hear the confessions of all his flock, +who wanted to discharge their souls of sin before taking flight for a +better world, was fain to tell them "there was no hurry, because the +eclipse had been put off a fortnight on account of the number of +penitents"! + +[Illustration: FIG. 76.--Eclipse of the Moon at Laos (February 27, +1877).] + +These fears and terrors are still extant among ignorant peoples. In the +night of February 27, 1877, an eclipse of the Moon produced an +indescribable panic among the inhabitants of Laos (Indo-China). In order +to frighten off the Black Dragon, the natives fired shots at the +half-devoured orb, accompanying their volley with the most appalling +yells. Dr. Harmand has memorialized the scene in the lively sketch given +on p. 269. + +During the solar eclipse of March 15, 1877, an analogous scene occurred +among the Turks, who for the moment forgot their preparations for war +with Russia, in order to shoot at the Sun, and deliver him from the +toils of the Dragon. + +The lunar eclipse of December 16, 1880, was not unnoticed at Tackhent +(Russian Turkestan), where it was received with a terrific din of +saucepans, samovars and various implements struck together again and +again by willing hands that sought to deliver the Moon from the demon +Tchaitan who was devouring her. + +In China, eclipses are the object of imposing ceremonies, whose object +is to reestablish the regularity of the celestial motions. Since the +Emperor is regarded as the Son of Heaven, his government must in some +sort be a reflection of the immutable order of the sidereal harmonies. +As eclipses were regarded by astrologers as disturbances of the divine +order, their appearance indicates some irregularity in the government of +the Celestial Empire. Accordingly, they are received with all kinds of +expiatory ceremonies prescribed thousands of years ago, and still in +force to-day. + +In the twentieth century, as in the nineteenth, the eighteenth, or in +ancient epochs, the same awe and terror operates upon the ignorant +populations who abound upon the surface of our planet. + +To return to astronomical realities. + +We said above that these phenomena were produced when the Full Moon and +the New Moon reached the line of intersection, known as the line of +nodes, when the plane of the lunar orbit cuts the plane of the ecliptic. +As this line turns and comes back in the same direction relatively to +the Sun at the end of eighteen years, eleven days, we have only to +register the eclipses observed during this period in order to know all +that will occur in the future, and to find such as happened in the past. +This period was known to the Greeks under the name of the Metonic Cycle, +and the Chaldeans employed it three thousand years ago under the name of +Saros. + +On examining this cycle, composed of 223 lunations, we see that there +can not be more than seven eclipses in one year, nor less than two. When +there are only two, they are eclipses of the Sun. + +The totality of a solar eclipse can not last more than seven minutes, +fifty-eight seconds at the equator, and six minutes, ten seconds in the +latitude of Paris. The Moon, on the contrary, may be entirely eclipsed +for nearly two hours. + +Eclipses of the Sun are very rare for a definite spot. Thus not one +occurred for Paris during the whole of the nineteenth century, the last +which happened exactly above the capital of France having been on May +22, 1724. I have calculated all those for the twentieth century, and +find that two will take place close to Paris, on April 17, 1912, at +eighteen minutes past noon (total for Choisy-le-Roi, Longjumeau, and +Dourdan, but very brief: seven seconds), and August 11, 1999, at 10.28 +A.M. (total for Beauvais, Compiègne, Amiens, St. Quentin, fairly long: +two minutes, seventeen seconds). Paris itself will not be favored before +August 12, 2026. In order to witness the phenomenon, one must go and +look for it. This the author did on May 28, 1900, in Spain. + +The progress of the lunar shadow upon the surface of the Earth is traced +beforehand on maps that serve to show the favored countries for which +our satellite will dispense her ephemeral night. The above figure shows +the trajectory of the total phase of the 1900 eclipse in Portugal, +Spain, Algeria, and Tunis. + +[Illustration: FIG. 77.--The path of the Eclipse of May 28, 1900.] + +The immutable splendor of the celestial motions had never struck the +author so impressively as during the observation of this grandiose +phenomenon. With the absolute precision of astronomical calculations, +our satellite, gravitating round the Earth, arrived upon the theoretical +line drawn from the orb of day to our planet, and interposed itself +gradually, slowly, and exactly, in front of it. The eclipse was total, +and occurred at the moment predicted by calculation. Then the obscure +globe of the Moon pursued its regular course, discovered the radiant orb +behind, and gradually and slowly completed its transit in front of him. +Here, to all observers, was a double philosophical lesson, a twofold +impression: that of the greatness, the omnipotence of the inexorable +forces that govern the universe, and that of the inexorable valor of +man, of this thinking atom straying upon another atom, who by the +travail of his feeble intelligence has arrived at the knowledge of the +laws by which he, like the rest of the world, is borne away through +space, through time, and through eternity. + +The line of centrality passed through Elche, a picturesque city of +30,000 inhabitants, not far from Alicante, and we had chosen this for +our station on account of the probability of fine weather. + +From the terrace of the country house of the hospitable Mayor, a farm +transformed into an observatory by our learned friend, Count de la Baume +Pluvinel, there were no obstacles between ourselves and any part of the +sky or landscape. The whole horizon lay before us. In front was a town +of Arab aspect framed in a lovely oasis of palm-trees; a little farther +off, the blue sea beyond the shores of Alicante and Murcia: on the +other side a belt of low mountains, and near us fields and gardens. A +Company of the Civic Guard kept order, and prevented the entrance of too +many curious visitors, of whom over ten thousand had arrived. + +At the moment when the first contact of the lunar disk with the solar +disk was observed in the telescope, we fired a gun, in order to announce +the precise commencement of the occultation to the 40,000 persons who +were awaiting the phenomenon, and to discover what difference would +exist between this telescopic observation and those made with the +unaided eyes (protected simply by a bit of smoked glass) of so many +improvised spectators. This had already been done by Arago at Perpignan +in 1842. The verification was almost immediate for the majority of eyes, +and may be estimated at eight or ten seconds. So that the commencement +of the eclipse was confirmed almost as promptly for the eye as with the +astronomical instruments. + +The sky was splendidly clear; no cloud, no mist, deep blue; blazing Sun. +The first period of the eclipse showed nothing particular. It is only +from the moment when more than half the solar disk is covered by the +lunar disk that the phenomenon is imposing in its grandeur. At this +phase, I called the attention of the people standing in the court to the +visibility of the stars, and indicating the place of Venus in the sky +asked if any with long sight could perceive her. Eight at once +responded in the affirmative. It should be said that the planet was at +that time at its period of maximum brilliancy, when for observers +blessed with good sight, it is always visible to the unaided eye. + +When some three-quarters of the Sun were eclipsed, the pigeons which had +flown back to the farm huddled into a corner, and made no further +movement. They told me that evening that the fowls had done the same a +little later, returning to the hen-house as though it had been night, +and that the small children (who were very numerous at Elche, where the +population is certainly not diminishing) left off their games, and came +back to their mothers' skirts. The birds flew anxiously to their nests. +The ants in one garden were excessively agitated, no doubt disconcerted +in their strategics. The bats came out. + +A few days before the eclipse I had prepared the inhabitants of this +part of Spain for the observation of the phenomenon by the following +description, which sums up the previous accounts of the astronomers: + +"The spectacle of a total eclipse of the Sun is one of the most +magnificent and imposing that it is possible to see in nature. At the +exact moment indicated by calculation, the Moon arrives in front of the +Sun, eats into it gradually, and at last entirely covers it. The light +of the day lessens and is transformed. A sense of oppression is felt by +all nature, the birds are hushed, the dog takes refuge with his master, +the chickens hide beneath their mother's wing, the wind drops, the +temperature falls, an appalling stillness is everywhere perceptible, as +though the universe were on the verge of some imminent catastrophe. +Men's faces assume a cadaverous hue similar to that given at night by +the flame of spirits of wine and salt, a livid funereal light, the +sinister illumination of the world's last hour. + +"At the moment when the last line of the solar crescent disappears, we +see, instead of the Sun, a black disk surrounded with a splendid +luminous aureole shooting immense jets into space, with roseate flames +burning at the base. + +"A sudden night has fallen on us, a weird, wan night in which the +brightest of the stars are visible in the Heavens. The spectacle is +splendid, grandiose, solemn, and sublime." + +This impression was actually felt by us all, as may be seen from the +following notes, written in my schedule of observation during the event, +or immediately after: + +"3.50 P.M. Light very weak, sky leaden gray, mountains standing out with +remarkable clearness from the horizon, and seeming to approach us. + +"3.55 P.M. Fall of temperature very apparent. Cold wind blowing through +the atmosphere. + +"3.56 P.M. Profound silence through nature, which seems to participate +in the celestial phenomenon. Silence in all the groups. + +"3.57 P.M. Light considerably diminished, becoming wan, strange, and +sinister. Landscape leaden gray, sea looks black. This diminution of +light is not that of every day after the sunset. There is, as it were, a +tint of sadness spread over the whole of nature. One becomes accustomed +to it, and yet while we know that the occultation of the Sun by the Moon +is a natural phenomenon, we can not escape a certain sense of +uneasiness. The approach of some extraordinary spectacle is imminent." + +At this point we examined the effects of the solar light upon the seven +colors of the spectrum. In order to determine as accurately as possible +the tonality of the light of the eclipse, I had prepared seven great +sheets, each painted boldly in the colors of the spectrum, violet, +indigo, blue, green, yellow, orange, red; and a similar series in pieces +of silk. These colors were laid at our feet upon the terrace where my +wife, as well as Countess de la Baume, were watching with me. We then +saw the first four disappear successively and entirely and turn black in +a few seconds, in the following order: violet, indigo, blue, green. The +three other colors were considerably attenuated by the darkness, but +remained visible. + +It should be noted that in the normal order of things--that is, every +evening--the contrary appears; violet remains visible after the red. + +This experiment shows that the last light emitted by the eclipsed Sun +belongs to the least refrangible rays, to the greatest wave-lengths, to +the slowest vibrations, to the yellow and red rays. Such therefore is +the predominating color of the solar atmosphere. + +This experiment completed, we turn back to the Sun. Magical and splendid +spectacle! Totality has commenced, the Sun has disappeared, the black +disk of the Moon covers it entirely, leaving all round it a magnificent +corona of dazzling light. One would suppose it to be an annular eclipse, +with the difference that this can be observed with the naked eye, +without fatigue to the retina, and drawn quietly. + +This luminous coronal atmosphere entirely surrounds the solar disk, at a +pretty equal depth, equivalent to about the third of half the solar +diameter. It may be regarded as the Sun's atmosphere. + +Beyond this corona is an aureole, of vaster glory but less luminous, +which sends out long plumes, principally in the direction of the +equatorial zone of the Sun, and of the belt of activity of the spots and +prominences. + +At the summit of the disk it is conical in shape. Below it is double, +and its right-hand portion ends in a point, not far from Mercury, which +shines like a dazzling star of first magnitude, and seems placed there +expressly to give us the extent and direction of the solar aureole. + +I draw these various aspects (which, moreover, change with the movement +of the Moon), and what strikes me most is the distinction in light +between this aureole and the coronal atmosphere; the latter appears to +be a brilliant silvery white, the former is grayer and certainly less +dense. + +My impression is that there are _two solar envelopes of entirely +different nature_, the corona belonging to the globe of the Sun, and +forming its atmosphere properly so-called, very luminous; the aureole +formed of particles that circulate independently round it, probably +arising from eruptions, their form as a whole being possibly due to +electric or magnetic forces, counterbalanced by resistances of various +natures. In our own atmosphere the volcanic eruptions are distinct from +the aerial envelope. + +The general configuration of this external halo, spreading more +particularly in the equatorial zone, is sufficiently like that of the +eclipse of 1889, published in my _Popular Astronomy_, which also +corresponded with a minimum of solar energy. The year 1900 is in fact +close upon the minimum of the eleven-year period. This equatorial form +is, moreover, what all the astronomers were expecting. + +[Illustration: FIG. 78.--Total eclipse of the Sun, May 28, 1900, as +observed from Elche (Spain).] + +There can no longer be the slightest doubt that the solar envelope +varies with the activity of the Sun.... + +"But the total eclipse lasted a much shorter time than I have taken to +write these lines. The seventy-nine seconds of totality are over. A +dazzling light bursts from the Sun, and tells that the Moon pursuing its +orbit has left it. The splendid sight is over. It has gone like a +shadow. + +"Already over! It is almost a disillusion. Nothing beautiful lasts in +this world. Too sad! If only the celestial spectacle could have lasted +two, three, or four minutes! It was too short.... + +"Alas! we are forced to take things as they are. + +"The surprise, the oppression, the terror of some, the universal silence +are over. The Sun reappears in his splendor, and the life of nature +resumes its momentarily suspended course. + +"While I was making my drawing, M. l'Abbé Moreux, my colleague from the +Astronomical Society of France, who accompanied me to Spain for this +observation, was taking one of his own, without any reciprocal +communication. These two sketches are alike, and confirmatory. + +"The differential thermometers that I exposed to the Sun, hanging +freely, and protected from reflection from the ground, were read every +five minutes. The black thermometer went down from 33.1° to 20.7°, that +is 12.4°; the white from 29° to 20.2°--that is, 8.8°. The temperature in +the shade only varied three degrees. + +"The light received during totality was due: first, to the luminous +envelope of the Sun; second, to that of the terrestrial atmosphere, +illuminated at forty kilometers (twenty-five miles) on the one side and +the other of the line of centrality. It appeared to be inferior to that +of the Full Moon, on account of the almost sudden transition. But, in +reality, it was more intense, for only first-magnitude stars were +visible in the sky, whereas on a night of full moon, stars of second, +and even of third magnitude are visible. We recognized, among others, +Venus, Mercury, Sirius, Procyon, Capella, Rigel, Betelgeuse." + + * * * * * + +From these notes, taken on the spot, it is evident that the +contemplation of a total eclipse of the Sun is one of the most marvelous +spectacles that can be admired upon our planet. + +Some persons assured me that they saw the shadow of the Moon flying +rapidly over the landscape. My attention was otherwise occupied, and I +was unable to verify this interesting observation. The shadow of the +Moon in effect took only eleven minutes (3.47 P.M. to 3.58 P.M.) to +traverse the Iberian Peninsula from Porto to Alicante, _i.e._, a +distance of 766 kilometers (475 miles). It must therefore have passed +over the ground at a velocity of sixty-nine kilometers per minute, or +1,150 meters per second, a speed higher than that of a bullet. It can +easily be watched from afar, on the mountains. + +Some weeks previous to this fine eclipse, when I informed the Spaniards +of the belt along which it could be observed, I had invited them to note +all the interesting phenomena they might witness, including the effects +produced by the eclipse upon animals. Birds returned hurriedly to their +nests, swallows lost themselves, sheep huddled into compact packs, +partridges were hypnotized, frogs croaked as if it were night, fowls +took refuge in the hen-house, and cocks crowed, bats came out, and were +surprised by the sun, chicks gathered under their mothers' wing, +cage-birds ceased their songs, some dogs howled, others crept shivering +to their masters' feet, ants returned to the antheap, grasshoppers +chirped as at sunset, pigeons sank to the ground, a swarm of bees went +silently back to their hive, and so on. + +These creatures behaved as though the night had come, but there were +also signs of fear, surprise, even of terror, differing only "in degree" +from those manifested during the grandiose phenomenon of a total +eclipse by human beings unenlightened by a scientific education. + +At Madrid the eclipse was only partial. The young King of Spain, Alfonso +XIII, took care to photograph it, and I offer the photograph to my +readers (Fig. 79), as this amiable sovereign did me the honor to give it +me a few days after the eclipse. + +[Illustration: FIG. 79.--The Eclipse of May 28, 1900, as photographed by +King Alfonso XIII, at Madrid.] + +The technical results of these observations of solar eclipses relate +more especially to the elucidation of the grand problem of the physical +constitution of the Sun. We alluded to them in the chapter devoted to +this orb. The last great total eclipses have been of immense value to +science. + +The eclipses of the Moon are less important, less interesting, than the +eclipses of the Sun. Yet their aspect must not be neglected on this +account, and it may be said to vary for each eclipse. + +Generally speaking, our satellite does not disappear entirely in the +Earth's cone of shadow; the solar rays are refracted round our globe by +our atmosphere, and curving inward, illumine the lunar globe with a rosy +tint that reminds one of the sunset. Sometimes, indeed, this refraction +does not occur, owing doubtless to lack of transparency in the +atmosphere, and the Moon becomes invisible. This happened recently, on +April 11, 1903. + +For any spot, eclipses of the Moon are incomparably more frequent than +eclipses of the Sun, because the cone of lunar shadow that produces the +solar eclipses is not very broad at its contact with the surface of the +globe (10, 20, 30, 50, 100 kilometers, according to the distance of the +Moon), whereas all the countries of the Earth for which the Moon is +above the horizon at the hour of the lunar eclipse are able to see it. +It is at all times a remarkable spectacle that uplifts our thoughts to +the Heavens, and I strongly advise my readers on no account to forego +it. + + + + +CHAPTER XI + +ON METHODS + +HOW CELESTIAL DISTANCES ARE DETERMINED, AND HOW THE SUN IS WEIGHED + + +I will not do my readers the injustice to suppose that they will be +alarmed at the title of this Lesson, and that they do not employ some +"method" in their own lives. I even assume that if they have been good +enough to take me on faith when I have spoken of the distances of the +Sun and Moon, and Stars, or of the weight of bodies at the surface of +Mars, they retain some curiosity as to how the astronomers solve these +problems. Hence it will be as interesting as it is useful to complete +the preceding statements by a brief summary of the methods employed for +acquiring these bold conclusions. + +The Sun seems to touch the Earth when it disappears in the purple mists +of twilight: an immense abyss separates us from it. The stars go hand in +hand down the constellated sky; and yet one can not think of their +inconceivable distance without a shiver. + +Our neighbor, Moon, floats in space, a stone's throw from us: but +without calculation we should never know the distance, which remains an +impassable desert to us. + +The best educated persons sometimes find it difficult to admit that +these distances of Sun and Moon are better determined and more precise +than those of certain points on our minute planet. Hence, it is of +particular moment for us to give an exact account of the means employed +in determining them. + +The calculation of these distances is made by "_triangulation_." This +process is the same that surveyors use in the measurement of terrestrial +distances. There is nothing very alarming about it. If the word repels +us a little at first, it is from its appearance only. + +When the distance of an object is unknown, the only means of expressing +its apparent size is by measurement of the angle which it subtends +before our eyes. + +We all know that an object appears smaller, in proposition with its +distance from us. This diminution is not a matter of chance. It is +geometric, and proportional to the distance. Every object removed to a +distance of 57 times its diameter measures an angle of 1 degree, +whatever its real dimensions. Thus a sphere 1 meter in diameter measures +exactly 1 degree, if we see it at a distance of 57 meters. A statue +measuring 1.80 meters (about 5 ft. 8 in.) will be equal to an angle of 1 +degree, if distant 57 times its height, that is to say, at 102.60 +meters. A sheet of paper, size 1 decimeter, seen at 5.70 meters, +represents the same magnitude. + +In length, a degree is the 57th part of the radius of a circle, _i.e._, +from the circumference to the center. + +The measurement of an angle is expressed in parts of the circumference. +Now, what is an angle of a degree? It is the 360th part of any +circumference. On a table 3.60 meters round, an angle of one degree is a +centimeter, seen from the center of the table. Trace on a sheet of paper +a circle 0.360 meters round--an angle of 1 degree is a millimeter. + +[Illustration: FIG. 80.--Measurement of Angles.] + +If the circumference of a circus measuring 180 meters be divided into +360 places, each measuring 0.50 meters in width, then when the circus is +full a person placed at the center will see each spectator occupying an +angle of 1 degree. The angle does not alter with the distance, and +whether it be measured at 1 meter, 10 meters, 100 kilometers, or in the +infinite spaces of Heaven, it is always the same angle. Whether a degree +be represented by a meter or a kilometer, it always remains a degree. As +angles measuring less than a degree often have to be calculated, this +angle has been subdivided into 60 parts, to which the name of _minutes_ +has been given, and each minute into 60 parts or _seconds_. Written +short, the degree is indicated by a little zero (°) placed above the +figure; the minute by an apostrophe ('), and the second by two ("). +These minutes and seconds of _arc_ have no relation with the same terms +as employed for the division of the duration of time. These latter ought +never to be written with the signs of abbreviation just indicated, +though journalists nowadays set a somewhat pedantic example, by writing, +_e.g._, for an automobile race, 4h. 18' 30", instead of 4h. 18m. 30s. + +This makes clear the distinction between the relative measure of an +angle and the absolute measures, such, for instance, as the meter. Thus, +a degree may be measured on this page, while a second (the 3,600th part +of a degree) measured in the sky may correspond to millions of +kilometers. + +Now the measure of the Moon's diameter gives us an angle of a little +more than half a degree. If it were exactly half a degree, we should +know by that that it was 114 times the breadth of its disk away from us. +But it is a little less, since we have more than half a degree (31'), +and the geometric ratio tells us that the distance of our satellite is +110 times its diameter. + +Hence we have very simply obtained a first idea of the distance of the +Moon by the measure of its diameter. Nothing could be simpler than this +method. The first step is made. Let us continue. + +This approximation tells us nothing as yet of the real distance of the +orb of night. In order to know this distance in miles, we need to know +the width in miles of the lunar disk. + +[Illustration: FIG. 81.--Division of the Circumference into 360 +degrees.] + +This problem has been solved, as follows: + +Two observers go as far as possible from each other, and observe the +Moon simultaneously, from two stations situated on the same meridian, +but having a wide difference of latitude. The distance that separates +the two points of observation forms the base of a triangle, of which the +two long sides come together on the Moon. + +[Illustration: FIG. 82.--Measurement of the distance of the Moon.] + +It is by this proceeding that the distance of our satellite was finally +established, in 1751 and 1752, by two French astronomers, Lalande and +Lacaille; the former observing at Berlin, the latter at the Cape of Good +Hope. The result of their combined observations showed that the angle +formed at the center of the lunar disk by the half-diameter of the Earth +is 57 minutes of arc (a little less than a degree). This is known as the +_parallax_ of the Moon. + +Here is a more or less alarming word; yet it is one that we can not +dispense with in discussing the distance of the stars. This astronomical +term will soon become familiar in the course of the present lesson, +where it will frequently recur, and always in connection with the +measurement of celestial distances. "Do not let us fear," wrote Lalande +in his _Astronomie des Dames_, "do not let us fear to use the term +parallax, despite its scientific aspect; it is convenient, and this term +explains a very simple and very familiar effect." + +"If one is at the play," he continues, "behind a woman whose hat is too +large, and prevents one from seeing the stage [written a hundred years +ago!], one leans to the left or right, one rises or stoops: all this is +a parallax, a diversity of aspect, in virtue of which the hat appears to +correspond with another part of the theater from that in which are the +actors." "It is thus," he adds, "that there may be an eclipse of the Sun +in Africa and none for us, and that we see the Sun perfectly, because we +are high enough to prevent the Moon's hiding it from us." + +See how simple it is. This parallax of 57 minutes proves that the Earth +is removed from the Moon at a distance of about 60 times its +half-diameter (precisely, 60.27). From this to the distance of the Moon +in kilometers is only a step, because it suffices to multiply the +half-diameter of the Earth, which is 6,371 kilometers (3,950 miles) by +this number. The distance of our satellite, accordingly, is 6,371 +kilometers, multiplied by 60.27--that is, 384,000 kilometers (238,000 +miles). The parallax of the Moon not only tells us definitely the +distance of our planet, but also permits us to calculate its real volume +by the measure of its apparent volume. As the diameter of the Moon seen +from the Earth subtends an angle of 31', while that of the Earth seen +from the Moon is 114', the real diameter of the orb of night must be to +that of the terrestrial globe in the relation of 273 to 1,000. That is a +little more than a quarter, or 3,480 kilometers (2,157 miles), the +diameter of our planet being 12,742 kilometers (7,900 miles). + +This distance, calculated thus by geometry, is positively determined +with greater precision than that employed in the ordinary measurements +of terrestrial distances, such as the length of a road, or of a railway. +This statement may seem to be a romance to many, but it is undeniable +that the distance separating the Earth from the Moon is measured with +greater care than, for instance, the length of the road from Paris to +Marseilles, or the weight of a pound of sugar at the grocer's. (And we +may add without comment, that the astronomers are incomparably more +conscientious in their measurements than the most scrupulous +shop-keepers.) + +Had we conveyed ourselves to the Moon in order to determine its distance +and its diameter directly, we should have arrived at no greater +precision, and we should, moreover, have had to plan out a journey +which in itself is the most insurmountable of all the problems. + +The Moon is at the frontier of our little terrestrial province: one +might say that it traces the limits of our domain in space. And yet, a +distance of 384,000 kilometers (238,000 miles) separates the planet from +the satellite. This space is insignificant in the immeasurable distances +of Heaven: for the Saturnians (if such exist!) the Earth and the Moon +are confounded in one tiny star; but for the inhabitants of our globe, +the distance is beyond all to which we are accustomed. Let us try, +however, to span it in thought. + +A cannon-ball at constant speed of 500 meters (547 yards) per second +would travel 8 days, 5 hours to reach the Moon. A train started at a +speed of one kilometer per minute, would arrive at the end of an +uninterrupted journey in 384,000 minutes, or 6,400 hours, or 266 days, +16 hours. And in less than the time it takes to write the name of the +Queen of Night, a telegraphic message would convey our news to the Moon +in one and a quarter seconds. + +Long-distance travelers who have been round the world some dozen times +have journeyed a greater distance. + +The other stars (beginning with the Sun) are incomparably farther from +us. Yet it has been found possible to determine their distances, and +the same method has been employed. + +But it will at once be seen that different measures are required in +calculating the distance of the Sun, 388 times farther from us than the +Moon, for from here to the orb of day is 12,000 times the breadth of our +planet. Here we must not think of erecting a triangle with the diameter +of the Earth for its base: the two ideal lines drawn from the +extremities of this diameter would come together between the Earth and +the Sun; there would be no triangle, and the measurement would be +absurd. + +In order to measure the distance which separates the Earth from the Sun, +we have recourse to the fine planet Venus, whose orbit is situated +inside the terrestrial orbit. Owing to the combination of the Earth's +motion with that of the Star of the Morning and Evening, the capricious +Venus passes in front of the Sun at the curious intervals of 8 years, +113-1/2 years less 8 years, 8 years, 113-1/2 years plus 8 years. + +Thus there was a transit in June, 1761, then another 8 years after, in +June, 1769. The next occurred 113-1/2 years less 8 years, _i.e._, +105-1/2 years after the preceding, in December, 1874; the next in +December, 1882. The next will be in June, 2004, and June, 2012. At these +eagerly anticipated epochs, astronomers watch the transit of Venus +across the Sun at two terrestrial stations as far as possible removed +from each other, marking the two points at which the planet, seen from +their respective stations, appears to be projected at the same moment on +the solar disk. This measure gives the width of an angle formed by two +lines, which starting from two diametrically opposite points of the +Earth, cross upon Venus, and form an identical angle upon the Sun. Venus +is thus at the apex of two equal triangles, the bases of which rest, +respectively, upon the Earth and on the Sun. The measurement of this +angle gives what is called the parallax of the Sun--that is, the angular +dimension at which the Earth would be seen at the distance of the Sun. + +[Illustration: FIG. 83.--Measurement of the distance of the Sun.] + +Thus, it has been found that the half-diameter of the Earth viewed from +the Sun measures 8.82". Now, we know that an object presenting an angle +of one degree is at a distance of 57 times its length. + +The same object, if it subtends an angle of a minute, or the sixtieth +part of a degree, indicates by the measurement of its angle that it is +60 times more distant, _i.e._, 3,438 times. + +Finally, an object that measures one second, or the sixtieth part of a +minute, is at a distance of 206,265 times its length. + +Hence we find that the Earth is at a distance from the Sun of +206,265/8.82--that is, 23,386 times its half-diameter, that is, +149,000,000 kilometers (93,000,000 miles). This measurement again is as +precise and certain as that of the Moon. + +I hope my readers will easily grasp this simple method of triangulation, +the result of which indicates to us with absolute certainty the distance +of the two great celestial torches to which we owe the radiant light of +day and the gentle illumination of our nights. + +The distance of the Sun has, moreover, been confirmed by other means, +whose results agree perfectly with the preceding. The two principal are +based on the velocity of light. The propagation of light is not +instantaneous, and notwithstanding the extreme rapidity of its +movements, a certain time is required for its transmission from one +point to another. On the Earth, this velocity has been measured as +300,000 kilometers (186,000 miles) per second. To come from Jupiter to +the Earth, it requires thirty to forty minutes, according to the +distance of the planet. Now, in examining the eclipses of Jupiter's +satellites, it has been discovered that there is a difference of 16 +minutes, 34 seconds in the moment of their occurrence, according as +Jupiter is on one side or on the other of the Sun, relatively to the +Earth, at the minimum and maximum distance. If the light takes 16 +minutes, 34 seconds to traverse the terrestrial orbit, it must take less +than that time, or 8 minutes, 17 seconds, to come to us from the Sun, +which is situated at the center. Knowing the velocity of light, the +distance of the Sun is easily found by multiplying 300,000 by 8 minutes, +17 seconds, or 497 seconds, which gives about 149,000,000 kilometers +(93,000,000 miles). + +Another method founded upon the velocity of light again gives a +confirmatory result. A familiar example will explain it: Let us imagine +ourselves exposed to a vertical rain; the degree of inclination of our +umbrella will depend on the relation between our speed and that of the +drops of rain. The more quickly we run, the more we need to dip our +umbrella in order not to meet the drops of water. Now the same thing +occurs for light. The stars, disseminated in space, shed floods of light +upon the Heavens. If the Earth were motionless, the luminous rays would +reach us directly. But our planet is spinning, racing, with the utmost +speed, and in our astronomical observations we are forced to follow its +movements, and to incline our telescopes in the direction of its +advance. This phenomenon, known under the name of _aberration_ of light, +is the result of the combined effects of the velocity of light and of +the Earth's motion. It shows that the speed of our globe is equivalent +to 1/10000 that of light, _i.e._, = about 30 kilometers (19 miles) per +second. Our planet accordingly accomplishes her revolution round the Sun +along an orbit which she traverses at a speed of 30 kilometers (better +29-1/2) per second, or 1,770 kilometers per minute, or 106,000 +kilometers per hour, or 2,592,000 kilometers per day, or 946,080,000 +kilometers (586,569,600 miles) in the year. This is the length of the +elliptical path described by the Earth in her annual translation. + +The length of orbit being thus discovered, one can calculate its +diameter, the half of which is exactly the distance of the Sun. + +We may cite one last method, whose data, based upon attraction, are +provided by the motions of our satellite. The Moon is a little disturbed +in the regularity of her course round the Earth by the influence of the +powerful Sun. As the attraction varies inversely with the square of the +distance, the distance may be determined by analyzing the effect it has +upon the Moon. + +Other means, on which we will not enlarge in this summary of the methods +employed for determinations, confirm the precisions of these +measurements with certainty. Our readers must forgive us for dwelling +at some length upon the distance of the orb of day, since this +measurement is of the highest importance; it serves as the base for the +valuation of all stellar distances, and may be considered as the meter +of the universe. + +This radiant Sun to which we owe so much is therefore enthroned in space +at a distance of 149,000,000 kilometers (93,000,000 miles) from here. +Its vast brazier must indeed be powerful for its influence to be exerted +upon us to such a manifest extent, it being the very condition of our +existence, and reaching out as far as Neptune, thirty times more remote +than ourselves from the solar focus. + +It is on account of its great distance that the Sun appears to us no +larger than the Moon, which is only 384,000 kilometers (238,000 miles) +from here, and is itself illuminated by the brilliancy of this splendid +orb. + +No terrestrial distance admits of our conceiving of this distance. Yet, +if we associate the idea of space with the idea of time, as we have +already done for the Moon, we may attempt to picture this abyss. The +train cited just now would, if started at a speed of a kilometer a +minute, arrive at the Sun after an uninterrupted course of 283 years, +and taking as long to return to the Earth the total would be 566 years. +Fourteen generations of stokers would be employed on this celestial +excursion before the bold travelers could bring back news of the +expedition to us. + +Sound is transmitted through the air at a velocity of 340 meters (1,115 +feet) per second. If our atmosphere reached to the Sun, the noise of an +explosion sufficiently formidable to be heard here would only reach us +at the end of 13 years, 9 months. But the more rapid carriers, such as +the telegraph, would leap across to the orb of day in 8 minutes, 17 +seconds. + +Our imagination is confounded before this gulf of 93,000,000 miles, +across which we see our dazzling Sun, whose burning rays fly rapidly +through space in order to reach us. + + * * * * * + +And now let us see how the distances of the planets were determined. + +We will leave aside the method of which we have been speaking; that now +to be employed is quite different, but equally precise in its results. + +It is obvious that the revolution of a planet round the Sun will be +longer in proportion as the distance is greater, and the orbit that has +to be traveled vaster. This is simple. But the most curious thing is +that there is a geometric proportion in the relations between the +duration of the revolutions of the planets and their distances. This +proportion was discovered by Kepler, after thirty years of research, +and embodied in the following formula: + +"The squares of the times of revolution of the planets round the Sun +(the periodic times) are proportional to the cubes of their mean +distances from the Sun." + +This is enough to alarm the boldest reader. And yet, if we unravel this +somewhat incomprehensible phrase, we are struck with its simplicity. + +What is a square? We all know this much; it is taught to children of ten +years old. But lest it has slipped your memory: a square is simply a +number multiplied by itself. + +Thus: 2 × 2 = 4; 4 is the square of 2. + +Four times 4 is 16; 16 is the square of 4. + +And so on, indefinitely. + +Now, what is a cube? It is no more difficult. It is a number multiplied +twice by itself. + +For instance: 2 multiplied by 2 and again by 2 equals 8. So 8 is the +cube of 2. 3 × 3 × 3 = 27; 27 is the cube of 3, and so on. + +Now let us take an example that will show the simplicity and precision +of the formula enunciated above. Let us choose a planet, no matter +which. Say, Jupiter, the giant of the worlds. He is the Lord of our +planetary group. This colossal star is five times (precisely, 5.2) as +far from us as the Sun. + +Multiply this number twice by itself 5.2 × 5.2 × 5.2 = 140. + +On the other hand, the revolution of Jupiter takes almost twelve years +(11.85). This number multiplied by itself also equals 140. The square of +the number 11.85 is equal to the cube of the number 5.2. This very +simple law regulates all the heavenly bodies. + +Thus, to find the distance of a planet, it is sufficient to observe the +time of its revolution, then to discover the square of the given number +by multiplying it into itself. The result of the operation gives +simultaneously the cube of the number that represents the distance. + +To express this distance in kilometers (or miles), it is sufficient to +multiply it by 149,000,000 (in miles 93,000,000), the key to the system +of the world. + +Nothing, then, could be less complicated than the definition of these +methods. A few moments of attention reveal to us in their majestic +simplicity the immutable laws that preside over the immense harmony of +the Heavens. + + * * * * * + +But we must not confine ourselves to our own solar province. We have yet +to speak of the stars that reign in infinite space far beyond our +radiant Sun. + +Strange and audacious as it may appear, the human mind is able to cross +these heights, to rise on the wings of genius to these distant suns, +and to plumb the depths of the abyss that separates us from these +celestial kingdoms. + +Here, we return to our first method, that of triangulation. And the +distance that separates us from the Sun must serve in calculating the +distances of the stars. + +The Earth, spinning round the Sun at a distance of 149,000,000 +kilometers (93,000,000 miles), describes a circumference, or rather an +ellipse, of 936,000,000 kilometers (580,320,000 miles), which it travels +over in a year. The distance of any point of the terrestrial orbit from +the diametrically opposite point which it passes six months later is +298,000,000 kilometers (184,760,000 miles), _i.e._, the diameter of this +orbit. This immense distance (in comparison with those with which we are +familiar) serves as the base of a triangle of which the apex is a star. + +The difficulty in exact measurements of the distance of a star consists +in observing the little luminous point persistently for a whole year, to +see if this star is stationary, or if it describes a minute ellipse +reproducing in perspective the annual revolution of the Earth. + +If it remains fixed, it is lost in such depths of space that it is +impossible to gage the distance, and our 298,000,000 kilometers have no +meaning in view of such an abyss. If, on the contrary, it is displaced, +it will in the year describe a minute ellipse, which is only the +reflection, the perspective in miniature, of the revolution of our +planet round the Sun. + +The annual parallax of a star is the angle under which one would see the +radius, or half-diameter, of the terrestrial orbit from it. This radius +of 149,000,000 kilometers (93,000,000 miles) is indeed, as previously +observed, the unit, the meter of celestial measures. The angle is of +course smaller in proportion as the star is more distant, and the +apparent motion of the star diminishes in the same proportion. But the +stars are all so distant that their annual displacement of perspective +is almost imperceptible, and very exact instruments are required for its +detection. + +[Illustration: FIG. 84.--Small apparent ellipses described by the stars +as a result of the annual displacement of the Earth.] + +The researches of the astronomers have proved that there is not one star +for which the parallax is equal to that of another. The minuteness of +this angle, and the extraordinary difficulties experienced in measuring +the distance of the stars, will be appreciated from the fact that the +value of a second is so small that the displacement of any star +corresponding with it could be covered by a spider's thread. + +A second of arc corresponds to the size of an object at a distance of +206,265 times its diameter; to a millimeter seen at 206 meters' +distance; to a hair, 1/10 of a millimeter in thickness, at 20 meters' +distance (more invisible to the naked eye). And yet this value is in +excess of those actually obtained. In fact:--the apparent displacement +of the nearest star is calculated at 75/100 of a second (0.75"), _i.e._, +from this star, [alpha] of Centaur, the half-diameter of the terrestrial +orbit is reduced to this infinitesimal dimension. Now in order that the +length of any straight line seen from the front be reduced until it +appear to subtend no more than an angle of 0.75", it must be removed to +a distance 275,000 times its length. As the radius of the terrestrial +orbit is 149,000,000 kilometers (93,000,000 miles), the distance which +separates [alpha] of Centaur from our world must therefore = +41,000,000,000,000 kilometers (25,000,000,000,000 miles). And that is +the nearest star. We saw in Chapter II that it shines in the southern +hemisphere. The next, and one that can be seen in our latitudes, is 61 +of Cygnus, which floats in the Heavens 68,000,000,000,000 kilometers +(42,000,000,000,000 miles) from here. This little star, of fifth +magnitude, was the first of which the distance was determined (by +Bessel, 1837-1840). + +All the rest are much more remote, and the procession is extended to +infinity. + +We can not conceive directly of such distances, and in order to imagine +them we must again measure space by time. + +In order to cover the distance that separates us from our neighbor, +[alpha] of Centaur, _light_, the most rapid of all couriers, takes 4 +years, 128 days. If we would follow it, we must not jump from start to +finish, for that would not give us the faintest idea of the distance: we +must take the trouble to think out the direct advance of the ray of +light, and associate ourselves with its progress. We must see it +traverse 300,000 kilometers (186,000 miles) during the first second of +the journey; then 300,000 more in the second, which makes 600,000 +kilometers; then once more 300,000 kilometers during the third, and so +on without stopping for four years and four months. If we take this +trouble we may realize the value of the figure; otherwise, as this +number surpasses all that we are in the habit of realizing, it will have +no significance for us, and will be a dead letter. + +If some appalling explosion occurred in this star, and the sound in its +flight of 340 meters (1,115 feet) per second were able to cross the +void that separates us from it, the noise of this explosion would only +reach us in 3,000,000 years. + +A train started at a speed of 106 kilometers (65 miles) per hour would +have to run for 46,000,000 years, in order to reach this star, our +neighbor in the celestial kingdom. + +The distance of some thirty of the stars has been determined, but the +results are dubious. + +The dazzling Sirius reigns 92,000,000,000,000 kilometers +(57,000,000,000,000 miles), the pale Vega at 204,000,000,000,000. Each +of these magnificent stars must be a huge sun to burn at such a distance +with such luminosity. Some are millions of times larger than the Earth. +Most of them are more voluminous than our Sun. On all sides they +scintillate at inaccessible distances, and their light strays a long +while in space before it encounters the Earth. The luminous ray that we +receive to-day from some pale star hardly perceptible to our eyes--so +enormous is its distance--may perhaps bring us the last emanation of a +sun that expired thousands of years ago. + + * * * * * + +If these methods have been clear to my readers, they may also be +interested perhaps in knowing the means employed in weighing the worlds. +The process is as simple and as clear as those of which we have been +speaking. + +_Weighing the stars!_ Such a pretension seems Utopian, and one asks +oneself curiously what sort of balance the astronomers must have adopted +in order to calculate the weight of Sun, Moon, planets or stars. + +Here, figures replace weights. Ladies proverbially dislike figures: yet +it would be easier for some society dame to weigh the Sun at the point +of her pen, by writing down a few columns of figures with a little care, +than to weigh a 12 kilogram case of fruit, or a dress-basket of 35 +kilos, by direct methods. + +Weighing the Sun is an amusement like any other, and a change of +occupation. + +If the Moon were not attracted by the Earth, she would glide through the +Heavens along an indefinite straight line, escaping at the tangent. But +in virtue of the attraction that governs the movements of all the +Heavenly bodies, our satellite at a distance of 60 times the terrestrial +half-diameter revolves round us in 27 days, 7 hours, 43 minutes, 11-1/2 +seconds, continually leaving the straight line to approach the Earth, +and describing an almost circular orbit in space. If at any moment we +trace an arc of the lunar orbit, and if a tangent is taken to this arc, +the deviation from the straight line caused by the attraction of our +planet is found to be 1-1/3 millimeter per second. + +This is the quantity by which the Moon drops toward us in each second, +during which she accomplishes 1,017 meters of her orbit. + +On the other hand, no body can fall unless it be attracted, drawn by +another body of a more powerful mass. + +Beings, animals, objects, adhere to the soil, and weigh upon the Earth, +because they are constantly attracted to it by an irresistible force. + +Weight and universal attraction are one and the same force. + +On the other hand, it can be determined that if an object is left to +itself upon the surface of the Earth, it drops 4.90 meters during the +first second of its fall. + +We also know that attraction diminishes with the square of the distance, +and that if we could raise a stone to the height of the Moon, and then +abandon it to the attraction of our planet, it would in the first second +fall 4.90 meters divided by the square of 60, or 3,600--that is, of +1-1/3 millimeters, exactly the quantity by which the Moon deviates from +the straight line she would pursue if the Earth were not influencing +her. + +The reasoning just stated for the Moon is equally applicable to the Sun. + +The distance of the Sun is 23,386 times the radius of the Earth. In +order to know how much the intensity of terrestrial weight would be +diminished at such a distance, we should look, in the first place, for +the square of the number representing the distance--that is, 23,386 +multiplied by itself, = 546,905,000. If we divide 4.90 meters, which +represents the attractive force of our planet, by this number, we get +9/1000000 of a millimeter, and we see that at the distance of the Sun, +the Earth's attraction would really be almost _nil_. + +Now let us do for our planet what we did for its satellite. Let us trace +the annual orbit of the terrestrial globe round the central orb, and we +shall find that the Earth falls in each second 2.9 millimeters toward +the Sun. + +This proportion gives the attractive force of the Sun in relation to +that of the Earth, and proves that the Sun is 324,000 times more +powerful than our world, for 2.9 millimeters divided by 0.000,009 equals +324,000, if worked out into the ultimate fractions neglected here for +the sake of simplicity. + +A great number of stars have been weighed by the same method. + +Their mass is estimated by the movement of a satellite round them, and +it is by this method that we are able to affirm that Jupiter is 310 +times heavier than the Earth, Saturn 92 times, Neptune 16 times, Uranus +14 times, while Mars is much less heavy, its weight being only +two-thirds that of our own. + +The planets which have no satellites have been weighed by the +perturbations which they cause in other stars, or in the imprudent +comets that sometimes tarry in their vicinity. Mercury weighs very much +less than the Earth (only 6/100) and Venus about 8/10. So the beautiful +star of the evening and morning is not so light as her name might imply, +and there is no great difference between her weight and our own. + +As the Moon has no secondary body submitted to her influence, her weight +has been calculated by reckoning the amount of water she attracts at +each tide in the ocean, or by observing the effects of her attraction on +the terrestrial globe. When the Moon is before us, in the last quarter, +she makes us travel faster, whereas in the first quarter, when she is +behind, she delays us. + +All the calculations agree in showing us that the orb of night is 81 +times less heavy than our planet. There is nearly as much difference in +weight between the Earth and the Moon as between an orange and a grape. + + * * * * * + +Not content with weighing the planets of our system, astronomers have +investigated the weight of the stars. How have they been enabled to +ascertain the quantity of matter which constitutes these distant +Suns--incandescent globes of fire scattered in the depths of space? + +They have resorted to the same method, and it is by the study of the +attractive influence of a sun upon some other contiguous neighboring +star, that the weight of a few of these has been calculated. + +Of course this method can only be applied to those double stars of which +the distance is known. + +It has been discovered that some of the tiny stars that we can hardly +see twinkling in the depths of the azure sky are enormous suns, larger +and heavier than our own, and millions of times more voluminous than the +Earth. + +Our planet is only a grain of dust floating in the immensity of Heaven. +Yet this atom of infinity is the cradle of an immense creation +incessantly renewed, and perpetually transformed by the accumulated +centuries. + +And what diversity exists in this army of worlds and suns, whose regular +harmonious march obeys a mute order.... + +But we have as yet said nothing about weight on the surface of the +worlds, and I see signs of impatience in my readers, for after so much +simple if unpoetical demonstration, they will certainly ask me for the +explanation that will prove to them that a kilogram transported to +Jupiter or Mars would weigh more or less than here. + +Give me your attention five minutes longer, and I will restore your +faith in the astronomers. + +It must not be supposed that objects at the surface of a world like +Jupiter, 310 times heavier than our own, weigh 310 times more. That +would be a serious error. In that case we should have to assume that a +kilogram transported to the surface of the Sun would there weigh 324,000 +times more, or 324,000 kilograms. That would be correct if these orbs +were of the same dimensions as the Earth. But to speak, for instance, +only of the divine Sun, we know that he is 108 times larger than our +little planet. + +Now, weight at the surface of a celestial body depends not only on its +mass, but also on its diameter. + +In order to know the weight of any body upon the surface of the Sun, we +must argue as follows: + +Since a body placed upon the surface of the Sun is 108 times farther +from its center than it is upon a globe of the dimensions of the Earth, +and since, on the other hand, attraction diminishes with the square of +the distance, the intensity of the weight would there be 108 multiplied +by 108, or 11,700 times weaker. Now divide the number representing the +mass, _i.e._, 324,000, by this number 11,700, and it results that bodies +at the surface of the Sun are 28 times heavier than here. A woman whose +weight was 60 kilos would weigh 1,680 kilograms there if organized in +the same way as on the Earth, and would find walking very difficult, for +at each step she would lift up a shoe that weighed at least ten +kilograms. + +This reasoning as just stated for the Sun may be applied to the other +stars. We know that on the surface of Jupiter the intensity of weight is +twice and a third times as great as here, while on Mars it only equals +37/100. + +On the surface of Mercury, weight is nearly twice as small again as +here. On Neptune it is approximately equal to our own. + +With deference to the Selenites, everything is at its lightest on the +Moon: a man weighing 70 kilograms on the Earth would not weigh more than +12 kilos there. + +So all tastes can be provided for: the only thing to be regretted is +that one can not choose one's planet with the same facility as one's +residence upon the Earth. + + + + +CHAPTER XII + +LIFE, UNIVERSAL AND ETERNAL + + +And now, while thanking my readers for having followed me so far in this +descriptive account of the marvels of the Cosmos, I must inquire what +philosophical impression has been produced on their minds by these +celestial excursions to the other worlds? Are you left indifferent to +the pageant of the Heavens? When your imagination was borne away to +these distant stars, suns of the infinite, these innumerable stellar +systems disseminated through a boundless eternity, did you ask what +existed there, what purpose was served by those dazzling spheres, what +effects resulted from these forces, radiations, energies? Did you +reflect that the elements which upon our little Earth determined a vital +activity so prodigious and so varied must needs have spread the waves of +an incomparably vaster and more diversified existence throughout the +immensities of the Universe? Have you felt that all can not be dead and +deserted, as we are tempted by the illusions of our terrestrial senses +and of our isolation to believe in the silence of the night: that on the +contrary, the real aim of Astronomy, instead of ending with statements +of the positions and movements of the stars, is to enable us to +penetrate to them, to make us divine, and know, and appreciate their +physical constitution, their degree of life and intellectuality in the +universal order? + +On the Earth, it is Life and Thought that flourish; and it is Life and +Thought that we seek again in these starry constellations strewn to +Infinitude amid the immeasurable fields of Heaven. + +The humble little planet that we inhabit presents itself to us as a +brimming cup, overflowing at every outlet. Life is everywhere. From the +bottom of the seas, from the valleys to the mountains, from the +vegetation that carpets the soil, from the mold in the fields and woods, +from the air we breathe, arises an immense, prodigious, and perpetual +murmur. Listen! it is the great voice of Nature, the sum of all the +unknown and mysterious voices that are forever calling to us, from the +ocean waves, from the forest winds, from the 300,000 kinds of insects +that are redundant everywhere, and make a lively community on the +surface of our globe. A drop of water contains thousands of curious and +agile creatures. A grain of dust from the streets of Paris is the home +of 130,000 bacteria. If we turn over the soil of a garden, field, or +meadow, we find the earthworms working to produce assimilable slime. If +we lift a stone in the path, we discover a crawling population. If we +gather a flower, detach a leaf, we everywhere find little insects living +a parasitic existence. Swarms of midges fly in the sun, the trees of the +wood are peopled with nests, the birds sing, and chase each other at +play, the lizards dart away at our approach, we trample down the +antheaps and the molehills. Life enwraps us in an inexorable +encroachment of which we are at once the heroes and the victims, +perpetuating itself to its own detriment, as imposed upon it by an +eternal reproduction. And this from all time, for the very stones of +which we build our houses are full of fossils so prodigiously multiplied +that one gram of such stone will often contain millions of shells, +marvels of geometrical perfection. The infinitely little is equal to the +infinitely great. + +Life appears to us as a fatal law, an imperious force which all obey, as +the result and the aim of the association of atoms. This is illustrated +for us upon the Earth, our only field of direct observation. We must be +blind not to see this spectacle, deaf not to hear its reaching. On what +pretext could one suppose that our little globe which, as we have seen, +has received no privileges from Nature, is the exception; and that the +entire Universe, save for one insignificant isle, is devoted to vacancy, +solitude, and death? + +We have a tendency to imagine that Life can not exist under conditions +other than terrestrial, and that the other worlds can only be inhabited +on the condition of being similar to our own. But terrestrial nature +itself demonstrates to us the error of this way of thinking. We die in +the water: fishes die out of the water. Again, short-sighted naturalists +affirm categorically that Life is impossible at the bottom of the sea: +1, because it is in complete darkness; 2, because the terrible pressure +would burst any organism; 3, because all motion would be impossible +there, and so on. Some inquisitive person sends down a dredge, and +brings up lovely creatures, so delicate in structure that the daintiest +touch must proceed with circumspection. There is no light in these +depths: they make it with their own phosphorescence. Other inquirers +visit subterranean caverns, and discover animals and plants whose organs +have been transformed by adaptation to their gloomy environment. + +What right have we to say to the vital energy that radiates round every +Sun of the Universe: "Thus far shalt thou come, and no further"? In the +name of Science? An absolute mistake. The Known is an infinitesimal +island in the midst of the vast ocean of the Unknown. The deep seas +which seemed to be a barrier are, as we have seen, peopled with special +life. Some one objects: But after all, there is air there, there is +oxygen: oxygen is indispensable: a world without oxygen would be a +world of death, an eternally sterile desert. Why? Because we have not +yet come across beings that can breathe without air, and live without +oxygen? Another mistake. Even if we did not know of any, it would not +prove that they do not exist. But as it happens, we do know of such: the +_anærobia_. These beings live without air, without oxygen. Better still: +oxygen kills them! + +All the evidence goes to show that in interpreting as we ought the +spectacle of terrestrial life, and the positive facts acquired by +Science, we should enlarge the circle of our conceptions and our +judgments, and not limit extra-terrestrial existence to the servile +image of what is in existence here below. Terrestrial organic forms are +due to local causes upon our planet. The chemical constitution of water +and of the atmosphere, temperature, light, density, weight, are so many +elements that have gone to form our bodies. Our flesh is composed of +carbon, nitrogen, hydrogen, and oxygen combined in the state of water, +and of some other elements, among which we may instance sodium chloride +(salt). The flesh of animals is not chemically different from our own. +All this comes from the water and the air, and returns to them again. +The same elements, in very minute quantities, make up all living bodies. +The ox that browses on the grass is formed of the same flesh as the man +who eats the beef. All organized terrestrial matter is only carbon +combined in variable proportions with hydrogen, nitrogen, oxygen, etc. + +But we have no right to forbid Nature to act differently in worlds from +which carbon is absent. A world, for example, in which silica replaces +carbon, silicic acid carbonic acid, might be inhabited by organisms +absolutely different from those which exist on the Earth, different not +only in form, but also in substance. We already know stars and suns for +which spectral analysis reveals a predominance of silica, _e.g._, Rigel +and Deneb. In a world where chlorine predominated, we might expect to +find hydrochloric acid, and all the fecund family of chlorides, playing +an important part in the phenomena of life. Might not bromine be +associated in other formations? Why, indeed, should we draw the line at +terrestrial chemistry? What is to prove that these elements are really +simple? May not hydrogen, carbon, oxygen, nitrogen, and sulphur all be +compounds? Their equivalents are multiples of the first: 1, 6, 8, 14, +16. And is even hydrogen the most simple of the elements? Is not its +molecule composed of atoms, and may there not exist a single species of +primitive atom, whose geometric arrangement and various associations +might constitute the molecules of the so-called simple elements? + +In our own solar system we discover the essential differences between +certain planets. In the spectrum of Jupiter, for instance, we are aware +of the action of an unknown substance that manifests itself by a marked +absorption of certain red rays. This gas, which does not exist upon the +Earth, is seen still more obviously in the atmospheres of Saturn and +Uranus. Indeed, upon this last planet the atmosphere appears, apart from +its water vapor, to have no sort of analogy with our own. And in the +solar spectrum itself, many of the lines have not yet been identified +with terrestrial substances. + +The interrelation of the planets is of course incontrovertible, since +they are all children of the same parent. But they differ among +themselves, not merely in respect of situation, position, volume, mass, +density, temperature, atmosphere, but again in physical and chemical +constitution. And the point we would now accent is that this diversity +should not be regarded as an obstacle to the manifestations of life, +but, on the contrary, as a new field open to the infinite fecundity of +the universal mother. + +When our thoughts take wing, not only to our neighbors, Moon, Venus, +Mars, Jupiter, or Saturn, but still more toward the myriads of unknown +worlds that gravitate round the suns disseminated in space, we have no +plausible reason for imagining that the inhabitants of these other +worlds of Heaven resemble us in any way, whether in form, or even in +organic substance. + +The substance of the terrestrial human body is due to the elements of +our planet, and notably to carbon. The terrestrial human form derives +from the ancestral animal forms to which it has gradually raised itself +by the continuous progress of the transformation of species. To us it +seems obvious that we are man or woman, because we have a head, a heart, +lungs, two legs, two arms, and so on. Nothing is less a matter of +course. That we are constituted as we are, is simply the result of our +pro-simian ancestors having also had a head, a heart, lungs, legs, and +arms--less elegant than your own, it is true, Madam, but still of the +same anatomy. And more and more, by the progress of paleontology, we are +delving down to the origin of beings. As certain as it is that the bird +derives from the reptile by a process of organic evolution, so certain +is it that terrestrial Humanity represents the topmost branches of the +huge genealogical tree, whereof all the limbs are brothers, and the +roots of which are plunged into the very rudiments of the most +elementary and primitive organisms. + +The multitude of worlds is surely peopled by every imaginable and +unimaginable form. Terrestrial man is endowed with five senses, or +perhaps it is better to say six. Why should Nature stop at this point? +Why, for instance, may she not have given to certain beings an +electrical sense, a magnetic sense, a sense of orientation, an organ +able to perceive the ethereal vibrations of the infra-red or +ultra-violet, or permitted them to hear at a distance, or to see through +walls? We eat and digest like coarse animals, we are slaves to our +digestive tube: may there not be worlds in which a nutritive atmosphere +enables its fortunate inhabitants to dispense with this absurd process? +The least sparrow, even the dusky bat, has an advantage over us in that +it can fly through the air. Think how inferior are our conditions, since +the man of greatest genius, the most exquisite woman, are nailed to the +soil like any vulgar caterpillar before its metamorphosis! Would it be a +disadvantage to inhabit a world in which we might fly whither we would; +a world of scented luxury, full of animated flowers; a world where the +winds would be incapable of exciting a tempest, where several suns of +different colors--the diamond glowing with the ruby, or the emerald with +the sapphire--would burn night and day (azure nights and scarlet days) +in the glory of an eternal spring; with multi-colored moons sleeping in +the mirror of the waters, phosphorescent mountains, aerial +inhabitants,--men, women, or perhaps of other sexes,--perfect in their +forms, gifted with multiple sensibilities, luminous at will, +incombustible as asbestos, perhaps immortal, unless they commit suicide +out of curiosity? Lilliputian atoms as we are, let us once for all be +convinced that our imagination is but sterility, in the midst of an +infinitude hardly glimpsed by the telescope. + +One important point seems always to be ignored expressly by those who +blindly deny the doctrine of the plurality of worlds. It is that this +doctrine does not apply more particularly to the present epoch than to +any other. _Our_ time is of no importance, no absolute value. Eternity +is the field of the Eternal Sower. There is no reason why the other +worlds should be inhabited _now_ more than at any other epoch. + +What, indeed, is the Present Moment? It is an open trap through which +the Future falls incessantly into the gulf of the Past. + +The immensity of Heaven bears in its bosom cradles as well as tombs, +worlds to come and perished worlds. It abounds in extinct suns, and +cemeteries. In all probability Jupiter is not yet inhabited. What does +this prove? The Earth was not inhabited during its primordial period: +what did that prove to the inhabitants of Mars or of the Moon, who were +perhaps observing it at that epoch, a few million years ago? + +To pretend that our globe must be the only inhabited world because the +others do not resemble it, is to reason, not like a philosopher, but, as +we remarked before, like a fish. Every rational fish ought to assume +that it is impossible to live out of water, since its outlook and its +philosophy do not extend beyond its daily life. There is no answer to +this order of reasoning, except to advise a little wider perception, and +extension of the too narrow horizon of habitual ideas. + +For us the resources of Nature may be considered infinite, and +"positive" science, founded upon our senses only, is altogether +inadequate, although it is the only possible basis of our reasoning. We +must learn to see with the eyes of our spirit. + +As to the planetary systems other than our own, we are no longer reduced +to hypotheses. We already know with certainty that our Sun is no +exception, as was suggested, and is still maintained, by some theorists. +The discovery in itself is curious enough. + +It is surely an exceptional situation that, given a sidereal system +composed of a central sun, and of one or more stars gravitating round +him, the plane of such a system should fall just within our line of +vision, and that it should revolve in such a way that the globes of +which it is composed pass exactly between this sun and ourselves in +turning round him, eclipsing him more or less during this transit. As, +on the other hand, the eclipses would be our only means of determining +the existence of these unknown planets (save indeed from perturbation, +as in the case of Sirius and Procyon), it might have seemed quixotic to +hope for like conditions in order to discover solar systems other than +our own. But these exceptional circumstances have reproduced themselves +at different parts of the Heavens. + +Thus, for instance, we have seen that the variable star Algol owes its +variations in brilliancy, which reduce it from second to fourth +magnitude every sixty-nine hours, to the interposition of a body between +itself and the Earth, and celestial mechanics has already been able to +determine accurately the orbit of this body, its dimensions and its +mass, and even the flattening of the sun Algol. Here, then, is a system +in which we know the sun and an enormous planet, whose revolution is +effected in sixty-nine hours with extreme rapidity, as measured by the +spectroscope. + +The star [delta] of Cepheus is in the same case: it is an orb eclipsed +in a period of 129 hours, and its eclipsing planet also revolves in the +plane of our vision. The variable star in Ophiuchus has an analogous +system, and observation has already revealed a great number of others. + +Since, then, a certain number of solar systems differing from our own +have been revealed, as it were in section, to terrestrial observation, +this affords us sufficient evidence of the existence of an innumerable +quantity of solar systems scattered through the immensities of space, +and we are no longer reduced to conjecture. + +On the other hand, analysis of the motions of several stars, such as +Sirius, Procyon, Altaïr, proves that these distant orbs have +companions,--planets not yet discovered by the telescope, and that +perhaps never will be discovered, because they are obscure, and lost in +the radiation of the star. + + * * * * * + +Some _savants_ have asserted that Life can not germinate if the +conditions of the environment differ too much from terrestrial +conditions. + +This hypothesis is purely gratuitous, and we will now discuss it. + +In order to examine what is happening on the Earth, let us mount the +ladder of time for a moment, to follow the evolutions of Nature. + +There was an epoch when the Earth did not exist. Our planet, the future +world of our habitation, slept in the bosom of the solar nebula. + +At last it came to birth, this cherished Earth, a gaseous, luminous +ball, poor reflection of the King of Orbs, its parent. Millions of years +rolled by before the condensation and cooling of this new globe were +sufficiently transformed to permit life to manifest itself in its most +rudimentary aspects. + +The first organic forms of the protoplasm, the first aggregations of +cells, the protozoons, the zoophytes or plant-animals, the gelatinous +mussels of the still warm seas, were succeeded by the fishes, then by +the reptiles, the birds, the mammals, and lastly man, who at present +occupies the top of the genealogical tree, and crowns the animal +kingdom. + +Humanity is comparatively young upon the Earth. We may attribute some +thousands of centuries of existence to it ... and some five years of +reason! + +The terrestrial organisms, from the lowest up to man, are the resultant +of the forces in action at the surface of our planet. The earliest seem +to have been produced by the combinations of carbon with hydrogen and +nitrogen; they were, so to speak, without animation, save for some very +rudimentary sensibility; the sponges, corals, polyps, and medusæ, give +us a notion of these primitive beings. They were formed in the tepid +waters of the primary epoch. As long as there were no continents, no +islands emerging from the level of the universal ocean, there were no +beings breathing in the air. The first aquatic creatures were succeeded +by the amphibia, the reptiles. Later on were developed the mammals and +the birds. + +What, again, do we not owe to the plant-world of the primary epoch, of +the secondary epoch, of the tertiary epoch, which slowly prepared the +good nutritious soil of to-day, in which the roses flourish, and the +peach and strawberry ripen? + +Before it gave birth to a Helen or a Cleopatra, life manifested itself +under the roughest forms, and in the most varied conditions. A +long-period comet passing in sight of the Earth from time to time would +have seen modifications of existence in each of its transits, in +accordance with a slow evolution, corresponding to the variation of the +conditions of existence, and progressing incessantly, for if Life is the +goal of nature, Progress is the supreme law. + +The history of our planet is the history of life, with all its +metamorphoses. It is the same for all the worlds, with some exceptions +of orbs arrested in their development. + +The constitution of living beings is in absolute relation with the +substances of which they are composed, the environment in which they +move, temperature, light, weight, density, the length of day and night, +the seasons, etc.--in a word, with all the cosmographic elements of a +world. + +If, for example, we compare between themselves two worlds such as the +Earth and Neptune, utterly different from the point of view of distance +from the Sun, we could not for an instant suppose that organic +structures could have followed a parallel development on these planets. +The average temperature must be much lower on Neptune than on the Earth, +and the same holds for intensity of light. The years and seasons there +are 165 times longer than with us, the density of matter is three times +as weak, and weight is, on the contrary, a little greater. Under +conditions so different from our own, the activities of Nature would +have to translate themselves under other forms. And doubtless the +elementary bodies would not be found there in the same proportions. +Consequently we have to conclude that organs and senses would not be the +same there as here. The optic nerve, for instance, which has formed and +developed here from the rudimentary organ of the trilobite to the +marvels of the human eye, must be incomparably more sensitive upon +Neptune than in our dazzling solar luminosity, in order to perceive +radiations that we do not perceive here. In all probability, it is +replaced there by some other organ. The lungs, functioning there in +another atmosphere, are different from our own. So, too, for the stomach +and digestive organs. Corporeal forms, animal and human, can not +resemble those which exist upon the Earth. + +Certain _savants_ contend that if the conditions differed too much from +terrestrial conditions, life could not be produced there at all. Yet we +have no right to limit the powers of Nature to the narrow bounds of our +sphere of observation, and to pretend that our planet and our Humanity +are the type of all the worlds. That is a hypothesis as ridiculous as it +is childish. + +Do not let us be "personal," like children, and old people who never see +beyond their room. Let us learn to live in the Infinite and the Eternal. + +From this larger point of view, the doctrine of the plurality of worlds +is the complement and the natural crown of Astronomy. What interests us +most in the study of the Universe is surely to know what goes on there. + + * * * * * + +These considerations show that, in all the ages, what really constitutes +a planet is not its skeleton but the life that vibrates upon its +surface. + +And again, if we analyze things, we see that for the Procession of +Nature, life is all, and matter nothing. + +What has become of our ancestors, the millions of human beings who +preceded us upon this globe? Where are their bodies? What is left of +them? Search everywhere. Nothing is left but the molecules of air, +water, dust, atoms of hydrogen, nitrogen, oxygen, carbon, etc., which +are incorporated in turn in the organism of every living being. + +The whole Earth is a vast cemetery, and its finest cities are rooted in +the catacombs. But now, in crossing Paris, I passed for at least the +thousandth time near the Church of St. Germain-l'Auxerrois, and was +obliged to turn out of the direct way, on account of excavations. I +looked down, and saw that immediately below the pavement, they had just +uncovered some stone coffins still containing the skeletons that had +reposed there for ten centuries. From time immemorial the passers-by had +trampled them unwittingly under foot. And I reflected that it is much +the same in every quarter of Paris. Only yesterday, some Roman tombs and +a coin with the effigy of Nero were found in a garden near the +Observatory. + +And from the most general standpoint of Life, the whole world is in the +same case, and even more so, seeing that all that exists, all that +lives, is formed of elements that have already been incorporated in +other beings, no longer living. The roses that adorn the bosom of the +fair ... but I will not enlarge upon this topic. + +And you, so strong and virile, of what elements is your splendid body +formed? Where have the elements you absorb to-day in respiration and +assimilation been drawn from, what lugubrious adventures have they been +subject to? Think away from it: do not insist on this point: on no +account consider it.... + +And yet, let us dwell on it, since this reality is the most evident +demonstration of the ideal; since what exists is you, is all of us, is +_Life_; and matter is only its substance, like the materials of a house, +and even less so, since its particles only pass rapidly through the +framework of our bodies. A heap of stones does not make a house. +Quintillions of tons of materials would not represent the Earth or any +other world. + +Yes, what really exists, what constitutes a complete orb, is the city of +Life. Let us recognize that the flower of life flourishes on the surface +of our planet, embellishing it with its perfume; that it is just this +life that we see and admire,--of which we form part,--and which is the +_raison d'être_ of things; that matter floats, and crosses, and crosses +back again, in the web of living beings,--and the reality, the goal, is +not matter--it is the life matter is employed upon. + +Yes, matter passes, and being also, after sharing in the concerted +symphony of life. + +And indeed everything passes rapidly! + +What irrepressible grief, what deep melancholy, what ineffaceable +regrets we feel, when as age comes on we look back, when we see our +friends fallen upon the road one after the other, above all when we +visit the beloved scenes of our childhood, those homes of other years, +that witnessed our first start in terrestrial existence, our first +games, our first affections--those affections of childhood that seemed +eternal--when we wander over those fields and valleys and hills, when +we see again the landscape whose aspect has hardly changed, and whose +image is so intimately linked with our first impressions. There near +this fireside the grandfather danced us on his knee, and told us +blood-curdling stories; here the kind grandmother came to see if we were +comfortably tucked in, and not likely to fall out of the big bed; in +this little wood, along these alleys that seemed endless, we spread our +nets for birds; in this stream we fished for crayfish; there on the path +we played at soldiers with our elders, who were always captains; on +these slopes we found rare stones and fossils, and mysterious +petrifactions; on this hill we admired the fine sunsets, the appearance +of the stars, the form of the constellations. There we began to live, to +think, to love, to form attachments, to dream, to question every +problem, to breathe intellectually and physically. And now, where is +this beloved grandfather? the good grandmother? where are all whom we +knew in infancy? where are our dreams of childhood? Winged thoughts +still seem to flutter in the air, and that is all. People, caresses, +voices, all have gone and vanished. The cemetery has closed over them +all. There is a silent void. Were all those fine and sunny hours an +illusion? Was it only to weep one day over this negation that our +childish hearts were so tenderly attached to these fleeting shadows? Is +there nothing, down the long length of human history, but eternal +delusion? + +It is here, above all, that we find ourselves in presence of the +greatest problems. Life is the goal, it is Life that produces the +conditions of Thought. Without Thought, where would be the Universe? + +We feel that without life and thought, the Universe would be an empty +theater, and Astronomy itself, sublime science, a vain research. We feel +that this is the truth, veiled as yet to actual science, and that human +races kindred with our own exist there in the immensities of space. Yes, +we _feel_ that this is truth. + +But we would fain go a little further in our knowledge of the universe, +and penetrate in some measure the secret of our destinies. We would know +if these distant and unknown Humanities are not attached to us by +mysterious cords, if our life, which will assuredly be extinguished at +some definite moment here below, will not be prolonged into the regions +of Eternity. + +A moment ago we said that nothing is left of the body. Millions of +organisms have lived, there are no remains of them. Air, water, smoke, +dust. _Memento, homo, quia pulvis es et in pulverem revertebis._ +Remember oh man! that dust thou art, and unto dust thou shalt return, +says the priest to the faithful, when he scatters the ashes on the day +after the carnival. + +The body disappears entirely. It goes where the corpse of Cæsar went an +hour after the extinction of his pyre. Nor will there be more remains of +any of us. And the whole of Humanity, and the Earth itself, will also +disappear one day. Let no one talk of the Progress of Humanity as an +end! That would be too gross a decoy. + +If the soul were also to disappear in smoke, what would be left of the +vital and intellectual organization of the world? Nothing. + +On this hypothesis, _all_ would be reduced to _nothing_. + +Our reason is not immense, our terrestrial faculties are sufficiently +limited, but this reason and these faculties suffice none the less to +make us feel the improbability, the absurdity, of this hypothesis, and +we reject it as incompatible with the sublime grandeur of the spectacle +of the universe. + +Undoubtedly, Creation does not seem to concern itself with us. It +proceeds on its inexorable course without consulting our sensations. +With the poet we regret the implacable serenity of Nature, opposing the +irony of its smiling splendor to our mourning, our revolts, and our +despair. + + Que peu de temps suffit pour changer toutes choses! + Nature au front serein, comme vous oubliez! + Et comme vous brisez dans vos métamorphoses + Les fils mystérieux où nos coeurs sont liés. + + D'autres vont maintenant passer où nous passâmes; + Nous y sommes venus, d'autres vont y venir, + Et le songe qu'avaient ébauché nos deux âmes, + Ils le continueront sans pouvoir le finir. + + Car personne ici-bas ne termine et n'acheve; + Les pires des humains sont comme les meilleurs; + Nous nous éveillons tous au même endroit du rêve: + Tout commence en ce monde et tout finit ailleurs. + + Répondez, vallon pur, répondez, solitude! + O Nature, abritée en ce désert si beau, + Quand nous serons couchés tous deux, dans l'attitude + Que donne aux morts pensifs la forme du tombeau, + + Est-ce que vous serez à ce point insensible, + De nous savoir perdus, morts avec nos amours, + Et de continuer votre fête paisible + Et de toujours sourire et de chanter toujours?[16] + +_Note.--Free Translation._ + + How brief a time suffices for all things to change! Serene-fronted + Nature, too soon you will forget!... in your metamorphoses + ruthlessly snapping the cords that bind our hearts together! + + Others will pass where we pass; we have arrived, and others will + arrive after us: the thought sketched out by our souls will be + pursued by theirs ... and they will not find the solution of it. + + For no one here begins or finishes: the worst are as the best of + humans; we all awake at the same moment of the dream: we all begin + in this world, and end otherwhere. + + Reply, sweet valley, reply, solitude; O Nature, sheltering in this + splendid desert, when we are both asleep, and cast by the tomb into + the attitude of pensive death. + + Will you to the last verge be so insensible, that, knowing us lost, + and dead with our loves, you will pursue your cheerful feast, and + smile, and sing always? + +Yes, mortals may say that when they are sleeping in the grave, spring +and summer will still smile and sing; husband and wife may ask +themselves if they will meet again some day, in another sphere; but do +we not _feel_ that our destinies can not be terminated here, and that +short of absolute and final nonentity for everything, they must be +renewed beyond, in that starry Heaven to which every dream has flown +instinctively since the first origins of Humanity? + +As our planet is only a province of the Infinite Heavens, so our actual +existence is only a stage in Eternal Life. Astronomy, by giving us +wings, conducts us to the sanctuary of truth. The specter of death has +departed from our Heaven. The beams of every star shed a ray of hope +into our hearts. On each sphere Nature chants the pæan of Life Eternal. + + THE END + + + + +INDEX + + + A + + Aberration, 300 + + Adams, 168 + + Agnesi, Marie, 5 + + Alcar, 34 + + Aldebaran, 44, 66 + + Alexandria, 3 + + Algol, 39 + + Ancients, views of, 30 + + Andrew Ellicot, 195 + + Andromeda, 37, 38 + + Angles, 289 + + Antares, 45, 66, 70 + + Antipodes, 208 + + Arago, 275 + + Arcturus, 39, 66 + + Asteroids, 146, 195 + + Astronomie des Dames, 9 + + Attraction, 208 + + Aureole, 279 + + Autumn Constellations, 54 + + Axis, 225 + + + B + + Babylonian Tables, 30 + + Bartholomew Diaz, 176 + + Bear, Little, 35 + Great, 32, 34, 35 + + Betelgeuse, 49, 66 + + Biela's Comet, 189, 198 + + Bode's law, 167 + + Bolides, 201 + + + C + + Cancer, 72 + + Capella, 38, 66 + + Cassiopeia, 36 + + Castor, 44, 68 + + Catalogue of Lalande, 65 + + Catharine of Alexandria, 3 + + Centaur, 52, 64, 65, 80 + + Ceres, 147 + + Chaldean pastors, 30 + + Chaldeans, 271 + + Chariot of David, 32 + + Charioteer, 38 + + Chart of Mars, 140 + + Châtelet, Marquise du, 4 + + Chiron, The Centaur, 30, 51 + + Chromosphere, 102 + + Clairaut, 3 + + Clerke, Agnes, 7 + + Cnidus, 31 + + Coggia's Comet, 187 + + Comet of Biela, 197 + of 1811, 186 + of 1858, 174 + + Comets, 111, 185 + + Constellations, 28 + figures of, 31 + Autumn, 54 + + Constellations, Spring, 52 + Summer, 53 + Winter, 51 + + Copernicus, 125 + + Corona Borealis, 40 + + Corona of the Sun, 104 + + Cygnus, 40 + + + D + + de Blocqueville, Madame, 5 + + de Breteuil, Gabrielle-Émilie, 4 + + de Charrière, Madame, 5 + + Deneb, 41 + + des Brosses, 5 + + Diaz, Bartholomew, 176 + + Dipper, 32, 34 + + Donati, 187 + + Double star, stellar dial of, 86 + + Double stars, 68, 70 + + Dragon, 36 + + du Châtelet, Marquise, 4 + + + E + + Eagle, 41 + + Earth, 205 + ancient notions of, 19 + distance from the sun, 215 + how sustained, 21 + inclination, 224 + in space, 20 + motion of, round the Sun, 222 + movement of, 217 + rotundity of, 206 + viewed from Mars, 144 + viewed from Mercury, 119 + viewed from Venus, 130 + weight, 210 + + Eclipse of Sun, May, 1900, 273 + + Eclipses, 259 + + Ellicot, Andrew, 195 + + Entretiens sur la Pluralité des mondes, 9 + + Equator, 225 + + Eudoxus, 31 + + Evening Star, 123 + + + F + + Faculæ, 98, 100 + + Fire-balls, 198 + + Flammarion's Lunar Ring, 253 + + Fleming, Mrs., 7 + + Fontenelle, 9 + + Foucault, 219 + + + G + + Galileo, 95, 98, 125, 244 + + Galle, 168 + + Globe, divisions of, 226 + + Great Bear, 32, 34, 35 + + Great Dog, 50 + + Grecian Calendar, 229 + + Greek alphabet, 33 + + + H + + Hall, Mr., 143 + + Halley, 181 + + Halley's Comet, 3, 175 + + Heavens, map of, 61 + + Hercules, 41, 66, 79 + + Herdsman, 39 + + Herschel, Caroline, 6 + + Hevelius, 246 + + Hipparchus, 31 + + Houses of the Sun, 43 + + Huggins, Lady, 8 + + Huyghens, 49 + + Hyades, 44 + + Hypatia, 3 + + + J + + Janssen, 102 + + Jupiter, 148 + satellites, 155 + telescopic aspect of, 150 + + + K + + Klumpke, Miss, 7 + + Kovalevsky, Sophie, 6 + + + L + + Lacaille, 292 + + Lalande, 3, 9, 65, 292 + + Latitudes, 226 + + Leonids, 195 + + Lepaute, Madame Hortense, 3, 4 + + Le Verrier, 167 + + Little Bear, 35 + + Little Dog, 50 + + Lockyer, 102 + + Longitudes, 226 + + Lucifer, 122 + + Lunar Apennines, 251 + landscape, 254 + topography, 252 + + Lyre, 40 + + + M + + Mars, 131 + chart of, 140 + + Measurement, 289 + + Medes and Lydians, 266 + + Mercury, 114 + + Meteorites, 201 + + Meteors, 190, 191 + + Metonic Cycle, 271 + + Milky Way, 78, 87 + + Mira Ceti, 77 + + Mitchell, Maria, 7 + + Mizar, 34, 69 + + Moon, 232 + diameter of, 242 + distance of, 292 + geological features of, 245 + map of, 247 + mountains of, 246 + phases of, 241 + photograph of, 240 + revolution of, 234 + rotation of, 242 + size of, 242 + temperature of, 250 + total eclipse of, 263 + + + N + + Nebula, in Andromeda, 81 + in Orion, 81 + in the Greyhounds, 82 + + Neptune, 65, 166 + revolution of, 169 + + Newton, 181 + + Nucleus, 95, 185 + + + O + + Orion, 48, 49, 81 + + + P + + Parallax, 292, 293 + annual, 306 + + Pearl, 40 + + Pegasus, 38 + + Penumbra, 96 + + Periodic Comet, orbit of, 182 + + Perseids, 195 + + Perseus, 38, 70, 78 + + Phenician navigators, 30 + + Phoebus, 67 + + Photosphere, 101 + + Piazzi, 147 + + Planets, 109, 113, 146 + distances, 110, 302 + orbits of, 115 + orbits of, 116 + + Pleiades, 38, 39, 44, 83 + occultation of, 85 + + Pleione, 84 + + Polaris, 63 + + Pole-star, 34, 63 + + Poles, 225 + + Pollux, 44 + + Pope Calixtus, 176 + + Prodigies in the heavens, 178 + + Ptolemy, 31, 217 + + + R + + Radiant, 195 + + Riccioli, 246 + + Rigel, 49, 70 + + Roberts, Mrs. Isaac, 7 + + + S + + Saidak, 34 + + Saros, 271 + + Satellites, 110 + + Saturn, 156 + revolution of, 157 + satellites, 162, 165 + volume, 158 + + Saturn's rings, 161 + + Scarpellini, Madame, 7 + + Scheiner, 95 + + Schiaparelli, 139 + + Secchi, Father, 7 + + Seven Oxen, 32 + + Sextuple star, 74 + + Shepherd's Star, 11 + + Shooting stars, 193, 194, 196 + + Sirius, 66, 309 + + _Solar storms_, 100 + flames, 105 + system, 65 + + Somerville, Mrs., 6 + + Spring constellations, 52 + + Stars, distances, 62 + double, 68, 70 + first magnitude, 57 + number of, 60 + quadruple, 73 + second magnitude, 58 + shooting, 193, 194 + temporary, 77 + + Stars, triple, 72 + variable, 75 + weight of, 313 + + Star cluster in Hercules, 79 + in the Centaur, 80 + + St. Catherine, 3 + + Summer constellations, 53 + + Sun, 88 + houses of the, 43 + measurement of distance, 297 + photograph of, 96 + rotation, 99 + temperature of, 105 + total eclipse of, 276 + weight, 106 + + Sun and Earth, comparative sizes of, 93 + + Sun-spots, 95, 101 + telescopic aspect of, 97 + + + T + + Temporary stars, 77, 78 + + Three Kings, 49 + + Total eclipse of the moon, 263 + of sun, 276 + + Triangulation, 288 + + Triple Star, 72 + + + U + + Umbra, 95 + + Universe, 22, 23, 90 + + Urania, 8, 9 + + Uranoliths, 201, 204 + + Uranus, 162 + + + V + + Variable stars, 75 + + Vega, 40 + + Venus, 121, 296 + phases of, 124 + + Vesper, 122 + + Victor Hugo, 24 + + + W + + Weighing worlds, 309 + + Winter constellations, 51 + + + Z + + Zodiac, constellations of, 46, 47 + + Zones, 225 + + + FOOTNOTES: + +[1] The French edition of this book is entitled Astronomy for +Women.--TRANSLATOR. + +[2] 1 kilometer = 0.6214 mile; 100 kilometers may be taken as 62 miles. +1 kilogram is about 2.2 lb.; 5 kilograms = 11 lb.--TRANSLATOR. + +[3] It is useful to know the letters of the Greek Alphabet. They are +easily learned, as follows: + + [alpha] Alpha + [beta] Beta + [gamma] Gamma + [delta] Delta + [epsilon] Epsilon + [zeta] Zeta + [eta] Eta + [theta] Theta + [iota] Iota + [kappa] Kappa + [lambda] Lambda + [mu] Mu + [nu] Nu + [xi] Xi + [omicron] Omicron + [pi] Pi + [rho] Rho + [sigma] or [sigma] Sigma + [tau] Tau + [upsilon] Upsilon + [phi] Phi + [chi] Chi + [psi] Psi + [omega] Omega + + + +[4] All the stars visible at any hour during the year can easily be +found with the help of the author's Planisphere mobile. + +[5] Let it be remarked in passing that the stars might be much farther +off than they are, and invisible to our eyes; the Heavens would then +assume the aspect of an absolutely empty space, the moon and planets +alone remaining. + +[6] 14" = 14 seconds of arc. One second of the circle is an exceedingly +minute quantity. It is 1 millimeter seen at a distance of 206 meters. +One millimeter seen at a distance of 20 m. 62 = 10 secs. These values +are invisible to the unaided eye. + +[7] These fine double stars can be observed with the help of the +smallest telescope. + +[8] For the explanation of the angular distances of degrees, minutes, +and seconds, see Chapter XI, on Methods of Measurement. + +[9] The author has endeavored on the plates to represent the aspect of +the Earth in the starry sky of Mercury, Venus, and Mars; but in all +representations of this kind the stars are necessarily made too large. +By calculation the diameters of the Earth and Moon as seen from the +planets, and their distances, are as follows: + + Diameter of Diameter of Distance + the Earth. the Moon. Earth-Moon. + + Of Mercury (opposition) 20" 8" 871" + Of Venus (opposition) 64" 17" 1,928" + Of Mars (quadrature) 15" 4" 464" + Of Jupiter (quadrature) 3.5" 0.1" 105" + +These aspects will be appreciated if we remember that the distance of +the components of [epsilon] Lyre = 207", that of Atlas in Pleione = +301", and that of the stars Mizar and Alcor = 708". + +[10] A few evenings ago, after observing Venus in the calm and silent +Heavens at the close of day, my eyes fell upon a drawing sent me by my +friend Gustave Dore, which is included in the illustrations of his +wonderful edition of Dante's Divina Commedia. This drawing seems to be +in place here, and I offer my readers a poor reproduction of it, taken +from the fine engraving in the book. Dante and Virgil, in the peaceful +evening, are contemplating _lo bel pianeta ch'ad amar conforta_ (the +beautiful planet that incites to love). + +[11] Strictly speaking, 1 kilometer = 0.6214 mile. Here, as throughout, +the equivalents are only given in round numbers.--TRANSLATOR. + +[12] Translator: Compare the well-known English rhyme: + + Thirty days hath September, + April, June, and November. + While all the rest have thirty-one, + Excepting February alone, + In which but twenty-eight appear + And twenty-nine when comes Leap Year. + + + +[13] Fifty-eight different pictures of the aspect of the Moon to the +unaided eye will be found in the Monthly Bulletins of the Astronomical +Society of France, for the year 1900, in pursuance of an investigation +made by the author among the different members of the Society. + +[14] My readers are charged not to speak of this property (which is +fairly extensive), lest the Budget Commission, at the end of its +resources, should be tempted to put on an unexpected tax. This ring, +which the astronomers presented to me in the year 1887, is almost in the +center of the lunar disk, to the north of Ptolemy and Herschel. + +[15] "La fin du Monde." Flammarion, p. 186. + +[16] Victor Hugo. _Tristesse d'Olympia._ + + + + + +End of Project Gutenberg's Astronomy for Amateurs, by Camille Flammarion + +*** END OF THIS PROJECT GUTENBERG EBOOK ASTRONOMY FOR AMATEURS *** + +***** This file should be named 25267-8.txt or 25267-8.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/2/5/2/6/25267/ + +Produced by Jason Isbell, Greg Bergquist and the Online +Distributed Proofreading Team at https://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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