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+*** START OF THE PROJECT GUTENBERG EBOOK 77004 ***
+
+
+
+
+
+     [Illustration: HIPPARCHUS IN THE OBSERVATORY OF ALEXANDRIA.]
+
+
+
+
+                               THE STORY
+
+                                OF THE
+
+                         SUN, MOON, AND STARS
+
+                                  BY
+
+                             AGNES GIBERNE
+
+       AUTHOR OF “THE STARRY SKIES,” “THE WORLD’S FOUNDATIONS,”
+                         “RADIANT SUNS,” ETC.
+
+                            [Illustration]
+
+                        WITH COPIOUS ADDITIONS
+
+                           Fully Illustrated
+
+                              CINCINNATI
+
+                         NATIONAL BOOK COMPANY
+
+
+
+
+                           COPYRIGHT, 1898,
+                            BY J. T. JONES.
+
+
+
+
+INTRODUCTION.
+
+BY CHARLES PRITCHARD, M. A., F. R. S.,
+
+PROFESSOR OF ASTRONOMY IN THE UNIVERSITY OF OXFORD.
+
+
+The pages of this volume on a great subject were submitted to my
+criticism while passing through the press, with a request from a friend
+that I would make any suggestions which might occur to me for its
+improvement. Naturally, such a request was entertained, in the first
+instance, with hesitation and misgiving. But after a rapid perusal
+of the first sheet, I found my interest awakened, and then gradually
+secured; for the book seemed to me to possess certain features of
+no ordinary character, and, in my judgment, held out the promise of
+supplying an undoubted want, thus enabling me to answer a question
+which I have been often asked, and which had as often puzzled me,
+to the effect, “Can you tell me of any book on astronomy suited to
+beginners?” I think just such a book is here presented to the reader;
+for the tale of the stellar universe is therein told with great
+simplicity, and perhaps with sufficient completeness, in an earnest and
+pleasant style, equally free, I think, from inaccuracy or unpardonable
+exaggeration. We have here the outlines of elementary astronomy,
+not merely detailed without mathematics, but to a very great extent
+expressed in untechnical language. Success in such an attempt I regard
+as a considerable feat, and one of much practical utility.
+
+For the science of astronomy is essentially a science of great
+magnitude and great difficulty. From the time of Hipparchus, some
+century and a half before the Christian era, down to the present
+day, the cultivation of astronomy has severely taxed the minds of a
+succession of men endowed with the rarest genius. The facts and the
+truths of the science thus secured have been of very slow accretion;
+but like all other truths, when once secured and thoroughly understood,
+they are found to admit of very simple verbal expression, and to lie
+well within the general comprehension, and, I may safely add, within
+the sympathies of all educated men and women.
+
+Thus the great astronomers, the original discoverers of the last
+twenty centuries, have labored, each in his separate field of the
+vast universe of nature, and other men, endowed with other gifts,
+have entered on their labors, and by systematizing, correlating, and
+simplifying the expression of their results, have brought the whole
+within the grasp of cultivated men engaged in other branches of the
+varied pursuits of our complicated life. It is in this sort of order
+that the amelioration and civilization of mankind have proceeded, and
+at the present moment are, I hope and believe, rapidly proceeding.
+
+It was, I suspect, under this point of view, though half unconsciously
+so, that my attention was arrested by the book now presented to the
+reader; for we have here many of the chief results of the laborious
+researches of such men as Ptolemy, Kepler, Newton, Herschel,
+Fraunhofer, Janssen, Lockyer, Schiaparelli, and others--no matter
+where accumulated or by whom recorded--filtered through the mind of
+a thoughtful and cultured lady, and here presented to other minds in
+the very forms wherein they have been assimilated and pictured in her
+own. And these forms and pictures are true. It is in this way that the
+intellectual “protoplasm” of the human mind is fostered and practically
+disseminated.
+
+And, then, there is still another point of view from which this general
+dissemination of great truths in a simple style assumes an aspect of
+practical importance. I allude to the influences of this process on the
+imaginative or poetic side of our complex nature.
+
+Wordsworth, in one of his prefaces, has stated so clearly the truth
+on this subject that I can not do better than give his words. “If the
+time should ever come,” he says, “when what is now science becomes
+familiarized to men, then the remotest discoveries of the chemist, the
+botanist, the mineralogist, will be as proper objects of the poet’s
+art as any upon which it can be employed. He will be ready to follow
+the steps of the man of science; he will be at his side, carrying
+sensation into the midst of the objects of science itself. The poet
+will lend his divine spirit to aid the transfiguration, and will
+welcome the being thus produced as a dear and genuine inmate of the
+household of man.”
+
+It is for reasons such as here stated that I heartily commend this
+book to the attention of those who take an interest in the advancement
+of the intellectual progress and culture of society. The story of the
+Kosmos is told by the authoress in her own language and after her own
+method. I believe, as I have said, the story is correct.
+
+OXFORD UNIVERSITY.
+
+
+
+
+CONTENTS.
+
+
+  CHAPTER.                                        PAGE.
+
+       I. THE EARTH ONE OF A FAMILY,                 13
+
+      II. THE HEAD OF OUR FAMILY,                    24
+
+     III. WHAT BINDS THE FAMILY TOGETHER,            34
+
+      IV. THE LEADING MEMBERS OF OUR FAMILY.--FIRST
+          GROUP,                                     46
+
+       V. THE LEADING MEMBERS OF OUR FAMILY.--SECOND
+          GROUP,                                     55
+
+      VI. THE MOON,                                  62
+
+     VII. VISITORS,                                  73
+
+    VIII. LITTLE SERVANTS,                           83
+
+      IX. NEIGHBORING FAMILIES,                      95
+
+       X. OUR NEIGHBORS’ MOVEMENTS,                 106
+
+      XI. MORE ABOUT THE SOLAR SYSTEM,              122
+
+     XII. MORE ABOUT THE SUN,                       133
+
+    XIII. YET MORE ABOUT THE SUN,                   148
+
+     XIV. MORE ABOUT THE MOON,                      157
+
+      XV. YET MORE ABOUT THE MOON,                  164
+
+     XVI. MERCURY, VENUS, AND MARS,                 180
+
+    XVII. JUPITER,                                  199
+
+   XVIII. SATURN,                                   214
+
+     XIX. URANUS AND NEPTUNE,                       225
+
+      XX. COMETS AND METEORITES,                    240
+
+     XXI. MORE ABOUT COMETS AND METEORITES,         246
+
+    XXII. MANY SUNS,                                267
+
+   XXIII. SOME PARTICULAR SUNS,                     278
+
+    XXIV. DIFFERENT KINDS OF SUNS,                  291
+
+     XXV. GROUPS AND CLUSTERS OF SUNS,              304
+
+    XXVI. THE PROBLEM OF SUN AND STAR DISTANCES,    310
+
+   XXVII. MEASUREMENT OF STAR DISTANCES,            320
+
+  XXVIII. THE MILKY WAY,                            329
+
+    XXIX. A WHIRLING UNIVERSE,                      337
+
+     XXX. READING THE LIGHT,                        344
+
+    XXXI. STELLAR PHOTOGRAPHY,                      355
+
+   XXXII. THE DAWN OF ASTRONOMY,                    363
+
+  XXXIII. MODERN ASTRONOMY,                         375
+
+   XXXIV. SIR ISAAC NEWTON,                         382
+
+    XXXV. LATER ASTRONOMY,                          393
+
+
+
+
+LIST OF ILLUSTRATIONS.
+
+
+                                                                 PAGE.
+
+  Hipparchus in the Observatory at Alexandria          _Frontispiece._
+
+  The Solar System                                                  15
+
+  The Pleiades                                                      19
+
+  Sun-spots                                                         29
+
+  Phases of Mercury before Inferior Conjunction--Evening Star       50
+
+  Appearance of the Full Moon                                       63
+
+  One Form of Lunar Crater                                          69
+
+  The Earth as Seen from the Moon                                   71
+
+  Passage of the Earth and the Moon through the Tail of a Comet     76
+
+  Passage of the Comet of 1843 Close to the Sun                     79
+
+  Meteor Emerging from Behind a Cloud                               84
+
+  The Great Shower of Shooting-stars, November 27, 1872             90
+
+  Constellation of the Great Bear                                  108
+
+  The Great Bear 50,000 Years Ago                                  109
+
+  The Great Bear 50,000 Years Hence                                109
+
+  Constellation of Orion as it Appears Now                         110
+
+  Constellation of Orion 50,000 Years Hence                        111
+
+  Position of Planets Inferior to Jupiter--Showing the Zone of the
+  Asteroids                                                        123
+
+  Comparative Size of the Planetary Worlds                         130
+
+  A Typical Sun-spot                                               135
+
+  A Solar Eruption                                                 138
+
+  Sun-flames, May 3, 1892                                          143
+
+  Solar Corona and Prominence                                      152
+
+  Comparative Size of the Earth and Sun                            155
+
+  The Moon--an Expired Planet                                      159
+
+  The Lunar Crater Copernicus                                      170
+
+  Lunar Eruption--Brisk Action                                     172
+
+  Lunar Eruption--Feeble Action                                    173
+
+  Nicolaus Copernicus                                              176
+
+  Phases of Venus                                                  186
+
+  Mars and the Path of its Satellites                              191
+
+  General Aspect of Jupiter--Satellite and its Shadow              200
+
+  Satellites of Jupiter Compared with the Earth and Moon           206
+
+  The System of Jupiter                                            208
+
+  Orbits of Nine Comets Captured by Jupiter                        213
+
+  Saturn and the Earth--Comparative Size                           215
+
+  Ideal View of Saturn’s Rings and Satellites from the Planet      222
+
+  Great Astronomers of Earlier Times                               227
+
+  The Great Comet of 1811                                          247
+
+  Donati’s Comet, 1858                                             249
+
+  Great Comet of 1744                                              254
+
+  The First Comet of 1888--June 4                                  255
+
+  Great Comet of 1680                                              260
+
+  Great Comet of 1769                                              261
+
+  Baron Alexander Von Humboldt                                     264
+
+  A Telescopic Field in the Milky Way                              270
+
+  Cygnus, Constellation of                                         279
+
+  Stars whose Distances are Best Known                             281
+
+  Lyra, Constellation of                                           297
+
+  Constellations in the Northern Hemisphere                        300
+
+  A Cluster of Stars in Centaurus                                  305
+
+  The Great Nebula in Andromeda, Compared with Size of the Solar
+  System                                                           307
+
+  A Cluster of Stars in Perseus                                    332
+
+  Hercules, Constellation of                                       338
+
+  The Great Bear, Constellation of                                 341
+
+  The Prism and Spectrum                                           344
+
+  The Spectroscope                                                 345
+
+  Spectra, Showing the Dark Lines                                  347
+
+  Great Astronomers of Later Times                                 377
+
+  Sir Isaac Newton                                                 386
+
+  Eye-piece of Lick Telescope                                      407
+
+  Lick Observatory                                                 409
+
+  Professor E. E. Barnard                                          410
+
+
+
+
+THE STORY
+
+OF THE
+
+SUN, MOON, AND STARS.
+
+
+CHAPTER I.
+
+THE EARTH ONE OF A FAMILY.
+
+
+What is this earth of ours?
+
+Something very great--and yet something very little. Something very
+great, compared with the things upon the earth; something very little,
+compared with the things outside the earth.
+
+And as our journeyings together are for a while to be away from earth,
+we shall find ourselves obliged to count her as something quite small
+in the great universe, where so many larger and mightier things are
+to be found,--if indeed they are mightier. Not that we have to say
+good-bye altogether to our old home. We must linger about her for a
+while before starting, and afterwards it will be often needful to come
+back, with speed swifter than the flight of light, that we may compare
+notes on the sizes and conditions of other places visited by us.
+
+But first of all: what _is_ this earth of ours?
+
+It was rather a pleasant notion which men held in olden days, that
+we--that great and important “We” which loves to perch itself upon
+a height--stood firm and fixed at the very center of everything. The
+earth was supposed to be a vast flat plain, reaching nobody could tell
+how far. The sun rose and set for us alone; and the thousands of stars
+twinkled in the sky at night for nobody’s good except ours; and the
+blue sky overhead was a crystal covering for the men of our earth,
+and nothing more. In fact, people seem to have counted themselves not
+merely to have had a kind of kingship over the lower animals of our
+earth, but to have been kings over the whole universe. Sun, stars, and
+sky, as well as earth, were made for man, and for man only.
+
+This was the common belief, though even in those olden days there were
+_some_ who knew better. But the world in general knows better now.
+
+Earth the center of the universe! Why, she is not that of even the
+particular family in the heavens to which she belongs. For we do not
+stand alone. The earth is one of a family of worlds, and that family is
+called THE SOLAR SYSTEM. And so far is our earth from being the head of
+the family, that she is not even one of the more important members. She
+is merely one of the little sisters, as it were.
+
+Men not only believed the earth, in past days, to be at the center
+of the universe; but also they believed her to remain there without
+change. Sun, moon, stars, planets, sky, might move; but never the
+earth. The solid ground beneath their feet, _that_ at least was firm.
+Every day the sun rose and set, and every night the stars, in like
+manner, rose and set. But this was easily explained. We on our great
+earth stood firm and still, while sun, moon, stars, went circling
+round us once in every twenty-four hours, just for our sole and
+particular convenience. What an important personage man must have felt
+himself then in God’s great universe! Once again, we know better now!
+
+[Illustration: THE SOLAR SYSTEM.]
+
+For it is the earth that moves, and not the sun; it is the earth that
+moves, and not the stars. The daily movements of sun and stars, rising
+in the east, traveling over the sky, and setting in the west, are
+no more real movements on their part than, when we travel in a rail
+way-train, the seeming rush of hedges, telegraph posts, houses, and
+fields is real. They are fixed and we are moving; yet the movement
+appears to us to be not ours but theirs.
+
+Still more strongly would this appear to be the case if there were no
+noise, no shaking, no jarring and trembling, to make us feel that we
+are not at rest. Sometimes when a train begins to move gently out of
+a station, from among other trains, it is at the first moment quite
+impossible to say whether the movement belongs to the train in which we
+are seated or to a neighboring train. And in the motions of our earth
+there is no noise, no shaking, no jarring--all are rapid, silent, and
+even.
+
+If you were rising through the air in a balloon, you would at first
+only know your own movement by seeing the earth seem to drop away from
+beneath you. And just so we can only know the earth’s movements by
+seeing how worlds around us _seem_ to move in consequence.
+
+When I speak of the Universe, I mean the whole of God’s mighty creation
+as far as the stars reach. Sometimes the word is used in this sense,
+and sometimes it is used only for a particular part of creation nearer
+to us than other parts. At present, however, we will put aside all
+thought of the second narrower meaning.
+
+The wisest astronomer living can not tell us how far the stars reach.
+We know now that there is no firm crystal covering over our heads,
+dotted with bright points here and there; but only the wide open sky
+or heaven, containing millions of stars, some nearer, some farther,
+some bright enough to be seen by us all, some only visible through a
+telescope.
+
+People talk often of the stars being “set in space;” and the meaning of
+“space” is simply “room.” Where you are must be space, or you could not
+be there. But it is when we get away from earth, and travel in thought
+through the wide fields of space, where God has placed his stars, that
+we begin to feel how vast it is, and what specks we are ourselves--nay,
+what a speck our very earth is, in this great and boundless creation.
+
+For there is no getting to the borders of space. As one telescope after
+another is made, each one stronger in power and able to reach farther
+than the last, still more and more stars are seen, and yet more and
+more behind and beyond, in countless millions.
+
+It is the same all round the earth. The old notion about our world
+being a flat plain has been long since given up. We know her now to be
+a round globe, not fixed, but floating like the stars in space.
+
+When you look _up_ into the sky, you are looking exactly in the
+opposite direction from where you would be looking _up_ if you were
+in Australia. For Australia’s “up” is our “down,” and our “down” is
+Australia’s “up.” Or, to put it more truly, “up” is always in the
+direction straight away from this earth, on whatever part of it you may
+be standing; and “down” is always towards the center of the earth.
+
+All round the globe, in north, south, east, west, whether you are in
+Europe, Asia, Africa, or America, though you will see different stars
+in certain different quarters of the earth, still overhead you will
+find shining countless points of light.
+
+And now, what are these stars? This is a matter on which people are
+often confused, and on which it is well to be quite clear before going
+one step farther.
+
+Some of the stars you have most likely often noticed. The seven chief
+stars of the Great Bear are known to a large number of people; and
+there are few who have not admired the splendid constellation of Orion.
+Perhaps you also know the W-shape of Cassiopeia, and the brilliant
+shining of Sirius, and the soft glimmer of the Pleiades.
+
+The different constellations or groups of principal stars have been
+watched by men for long ages past. They are called the fixed stars, for
+they do not change. How many thousands of years ago they were first
+arranged by men into these groups, and who first gave them their names,
+we can not tell.
+
+True, night by night, through century after century, they rise, and
+cross the sky, and set. But those are only seeming movements. Precisely
+as the turning round of the earth upon her axis, once in every
+twenty-four hours, makes the sun appear to rise and cross the sky and
+set, in the day-time; so also the same turning of the earth makes the
+stars appear to do the same in the night-time.
+
+There is another seeming movement among the stars, which is only in
+seeming. Some come into view in summer which can not be seen in
+winter; and some come into view in winter which can not be seen in
+summer. For the sun, moving on his pathway through the sky, hides those
+stars which shine with him in the day-time. The zodiac is an imaginary
+belt in the heavens, sixteen or eighteen degrees wide, containing the
+twelve constellations through which the sun passes. And as he passes
+from point to point of his pathway, he constantly conceals from us
+fresh groups of stars by day, and allows fresh groups to appear by
+night. Speaking generally, however, the stars remain the same year
+after year, century after century. The groups may still be seen as of
+old, fixed and unchanging.
+
+[Illustration: THE PLEIADES.]
+
+What are these stars? Stars and planets have both been spoken about.
+There is a great difference between the two.
+
+Perhaps if you were asked whether the sun is most like to a star or a
+planet, you would be rather at a loss; and many who have admired the
+brilliant evening star, Venus, often to be seen after sunset, would be
+surprised to learn that the evening star is in reality no star at all.
+
+A star is a sun. Our sun is nothing more nor less than a star. Each one
+of the so-called “fixed stars,” that you see shining at night in the
+sky, is a sun like our sun; only some of the stars are larger suns and
+some are smaller suns than ours.
+
+The main reason why our sun looks so much larger and brighter than the
+stars is, that he is so very much nearer to us. The stars are one and
+all at enormous distances from the earth. By and by we will go more
+closely into the matter of their distance, compared with the distance
+of the sun.
+
+At present it is enough to say that if many of the stars were placed
+just as near to us as our sun is placed, they would look just as large
+and bright; while there are some that would look a great deal larger
+and brighter. And if our sun were to travel away from us, to the
+distance of the very nearest of the little twinkling stars, he would
+dwindle down and down in size and brilliancy, till at last we should
+not be able to tell him apart from the rest of the stars.
+
+I have told you that the stars are called “fixed” because they keep
+their places, and do not change from age to age. Though the movement
+of the earth makes them seem all to sweep past every night in company,
+yet they do not travel in and out among one another, or backwards
+and forwards, or from side to side. At all events, if there be such
+changes, they are so slow and so small as to be exceedingly difficult
+to find out. Each group of stars keeps its own old shape, as for
+hundreds of years back.
+
+But among these fixed stars there are certain stars which do go to and
+fro, and backwards and forwards. Now they are to be seen in the middle
+of one constellation, and now in the middle of another. These restless
+stars were long a great perplexity. Men named them Planets or Wanderers.
+
+We know now that the planets are in reality not stars at all, and also
+that they are not nearly so far away from us as the fixed stars. In
+fact, they are simply members of our own family--the Solar System. They
+are worlds, more or less like the world we live in; and they travel
+round and round the sun as we do, each more or less near to him; and
+they depend upon him for heat and light, in more or less the same
+manner as ourselves.
+
+Therefore, just as our sun is a star, and stars are suns, so our earth
+or world is a planet, and planets are worlds. EARTH is the name we
+give to that particular world or planet on which we live. Planets may
+generally be known from stars by the fact that they do not twinkle.
+But the great difference between the two lies in the fact that a star
+shines by its own radiant, burning light, whereas a planet shines
+merely by light reflected or borrowed from the sun.
+
+But how were the earth and the other worlds made? Let us imagine an
+immense gaseous mass placed in space. Attraction is a force inherent in
+every atom of matter. The denser portion of this mass will insensibly
+attract towards it the other parts, and in the slow fall of the more
+distant molecules towards this more attractive region, a general motion
+is produced, incompletely directed towards this center, and soon
+involving the whole mass in the same motion of rotation. The simplest
+form of all, even in virtue of this law of attraction, is the spherical
+form. It is that which a drop of water takes, and a drop of mercury if
+left to itself.
+
+The laws of mechanics show that, as this gaseous mass condenses and
+shrinks, the motion of rotation of the nebula is accelerated. In
+turning, it becomes flattened at the poles, and gradually takes the
+form of an immense lens-shaped mass of gas. It has begun to turn so
+quickly as to develop at its exterior circumference a centrifugal force
+superior to the general attraction of the mass, as when we whirl a
+sling. The inevitable consequence of this excess is a rupture of the
+equilibrium, which detaches an external ring. This gaseous ring will
+continue to rotate in the same time and with the same velocity; but
+the nebulous mother will be henceforth detached, and will continue to
+undergo progressive condensation and acceleration of motion. The same
+feat will be reproduced as often as the velocity of rotation surpasses
+that by which the centrifugal force remains inferior to the attraction.
+It may have happened also that secondary centers of condensation would
+be formed even in the interior of the nebula.
+
+In our system the rings of Saturn still subsist.
+
+The successive formation of the planets, their situation near the
+plane of the solar equator, and their motions of translation round the
+same center, are explained by the theory which we are discussing. The
+most distant known planet, Neptune, would be detached from the nebula
+at the epoch when this nebula extended as far as the planet, out to
+nearly three thousand millions of miles, and would turn in a slow
+revolution requiring a period of 165 years for its accomplishment. The
+original ring could not remain in the state of a ring unless it was
+perfectly homogeneous and regular; but such a condition is, so to say,
+unrealizable, and it did not delay in condensing itself into a sphere.
+Successively, Uranus, Saturn, Jupiter, the army of small planets, Mars,
+would thus be detached or formed in the interior of this same nebula.
+Afterwards came the earth, of which the birth goes back to the epoch
+when the sun had arrived at the earth’s present position. Venus and
+Mercury would be born later. Will the sun give birth to a new world?
+This is not probable.
+
+
+
+
+CHAPTER II
+
+THE HEAD OF OUR FAMILY.
+
+
+People began very early in the history of the world to pay close
+attention to the sun. And no wonder. We owe so much to his heat and
+light that the marvel would be if men had not thought much about him.
+
+Was the sun really any larger than he looked, and if so, how much
+larger was he? And what was his distance from the earth? These were two
+of the questions which puzzled our ancestors the longest. If once they
+could have settled exactly how far off the sun really was, they could
+easily have calculated his exact size; but this was just what they
+could not do.
+
+So one man supposed that the sun must be quite near, and very little
+larger than he looked. Another thought he might be seventy-five miles
+in diameter. A third ventured to believe that he was larger than the
+country of Greece. A fourth was so bold as to imagine that he might
+even outweigh the earth herself.
+
+After a while many attempts were made to measure the distance of the
+sun; and a great many different answers to this difficult question
+were given by different men, most of them very wide of the mark. It
+is only of late years that the matter has been clearly settled. And,
+indeed, it was found quite lately that a mistake of no less than three
+millions of miles had been made, notwithstanding all the care and all
+the attention given. But though three millions of miles sounds a great
+deal, yet it is really very little--only a tiny portion of the whole.
+
+For the distance of the sun from the earth is no less than about
+NINETY-THREE MILLIONS OF MILES. Ninety-three millions of miles! Can
+you picture that to yourself? Try to think what is meant by a thousand
+miles. Our earth is eight thousand miles in diameter. In other words,
+if you were to thrust a gigantic knitting-needle through her body,
+from the North Pole to the South Pole, it would have to be about eight
+thousand miles long.
+
+To reach the thought of one million, you must picture _one thousand
+times one thousand_. Our earth is about twenty-five thousand miles
+round. If you were to start from the mouth of the River Amazon, in
+South America, and journey straight round the whole earth on the
+equator, till you came back to the same point, you would have traveled
+about twenty-five thousand miles. But that would be a long way off from
+a million miles. You would have gone only once round the earth. Now a
+cord one million miles in length could be wrapped, not once only, but
+_forty times_, round and round the earth. And when you have managed
+to reach up to the thought of one million miles, you have then to
+remember that the sun’s distance is ninety-three times as much again.
+So, to picture clearly to ourselves the actual meaning of “ninety-three
+millions of miles” is not so easy.
+
+Suppose it were possible to lay a railroad from here to the sun. If
+you could journey thither in a perfectly straight line, at the rate
+of thirty miles an hour, never pausing for one single minute, night or
+day, you would reach the sun in about three hundred and forty-six years.
+
+Thirty miles an hour is a slow train. Suppose we double the speed, and
+make it an express train, rushing along at the pace of sixty miles
+an hour. Then you might hope to reach the end of your journey in one
+hundred and seventy-three years. If you had quitted this earth early in
+the eighteenth century, never stopping on your way, you would be, just
+about now, near the end of the nineteenth, arriving at the sun.
+
+So much for the sun’s distance from us. Now as to his size.
+
+I have already mentioned that our earth’s diameter--that is, her
+_through measure_, as, for instance, the line drawn straight from
+England through her center to New Zealand--is about eight thousand
+miles. This sounds a good deal. But what do you think of the diameter
+of the sun being no less than _eight hundred and fifty-eight thousand
+miles_? The one is eight thousand miles, the other over eight hundred
+thousand!
+
+Suppose you had a long slender pole which would pass through the middle
+of the earth, one end just showing at the North Pole and the other at
+the South Pole. You would need more than a hundred and eight of such
+poles, all joined together, to show the diameter of the sun.
+
+The sun seems not to be made of nearly such heavy materials as the
+earth. He is what astronomers call less “dense,” less close and compact
+in his make, just as wood is less dense and heavy than iron. Still,
+his size is so enormous, that if you could have a pair of gigantic
+scales, and put the sun into one scale and the earth with every one of
+her brother and sister planets into the other, the sun’s side would go
+down like lightning. He would be found to weigh seven hundred and fifty
+times as much as all the rest put together. And, it would take more
+than twelve hundred thousand little earths like ours, rolled into one
+huge ball, to make a globe as large as the sun.
+
+In the beginning of the seventeenth century a man named Fabricius was
+startled by the sight of a certain black spot upon the face of the
+sun. He watched till too dazzled to look any longer, supposing it to
+be a small cloud, yet anxious to learn more. Next day the spot was
+there still, but it seemed to have moved on a little way. Morning after
+morning this movement was found to continue, and soon a second spot,
+and then a third spot, were observed creeping in like manner across
+the sun. After a while they vanished, one at a time, round his edge,
+as it were; but after some days of patient waiting on the part of the
+lookers-on, they appeared again at the opposite edge, and once more
+began their journey across.
+
+Fabricius seems to have been the first, but he was not the last, to
+watch sun-spots. Many astronomers have given close attention to them.
+Modern telescopes, and the modern plan of looking at the sun through
+darkened glass, have made this possible in a way that was not possible
+two or three hundred years ago.
+
+The first important discovery made through the spots on the sun, was
+that the sun turns round upon his axis, just in the same manner that
+the earth turns round upon hers. Instead of doing so once in the course
+of each twenty-four hours, like the earth, he turns once in the course
+of about twenty-five days.
+
+It must not be supposed that the spots seen now upon the sun are the
+same spots that Fabricius saw so long ago. There is perpetual change
+going on; new spots forming, old spots vanishing; one spot breaking
+into two, two spots joining into one, and so on. Even in a single hour
+great alterations are sometimes seen to take place.
+
+Still, many of the spots do remain long enough and keep their shapes
+closely enough to be watched from day to day, and to be known again as
+old friends when they reappear, after being about twelve days hidden on
+the other side of the sun. So that the turning of the sun upon his axis
+has become, after long and careful examination, a certain known fact.
+
+For more than thirty years one astronomer kept close watch over the
+spots on every day that it was possible to see the sun. Much has been
+learned from his resolute perseverance.
+
+Now what are these spots?
+
+One thing seems pretty sure, and that is that they are caused by some
+kind of tremendous storms or cyclones taking place on the surface of
+that huge ball of fire.
+
+[Illustration: SUN SPOTS.]
+
+The first attentive observer of the sun, Scheiner, at first regarded
+the spots as satellites--an indefensible opinion, which, however,
+some have attempted to revive. Galileo attributed them to clouds or
+vapors floating in the solar atmosphere; this was the best conclusion
+which could be drawn from the observations of that epoch. This opinion
+met for a long time with general approval; it has even been renewed
+in our day. Some astronomers, and among them Lalande, believed, on
+the contrary, that they were mountains, of which the flanks, more
+or less steep, might produce the aspect of the penumbra--an opinion
+irreconcilable with the proper motion which the spots sometimes possess
+in a very marked manner. It is not usual, in fact, to see mountains
+traveling. Derham attributed them to the smoke issuing from the
+volcanic craters of the sun, an opinion revived and maintained in
+recent times by Chacornac. Several _savants_, regarding the sun as a
+liquid and incandescent mass, have also explained the spots by immense
+cinders floating on this ocean of fire. But a century had scarcely
+elapsed after the epoch when the spots were observed for the first
+time, when an English astronomer, Wilson, showed with certainty that
+the spots are hollow.
+
+We do not know with any certainty whether the sun is through and
+through one mass of glowing molten heat, or whether he may have a solid
+and even cool body within the blazing covering. Some have thought the
+one, and some the other. We only know that he is a mighty furnace of
+heat and flame, beyond anything that we can possibly imagine on our
+quiet little earth.
+
+It seems very sure that no such thing as “quietness” is to be found on
+the surface of the sun. The wildest and fiercest turmoil of rushing
+wind and roaring flame there prevails. The cyclones or hurricanes which
+take place are sometimes so rapid and so tremendous in extent, tearing
+open the blazing envelope of the sun, and showing glimpses of fiery
+though darker depths below, that we, on our far-distant earth, can
+actually watch their progress.
+
+Astronomers speak of the “quivering fringe of fire” all around the edge
+of the sun, visible through telescopes. But the sun is perpetually
+turning on his axis, so that each hour fresh portions of his surface
+thus pass the edge, showing the same appearance. What conclusion
+can we come to but that the whole enormous surface of the sun is one
+restless, billowy sea of fire and flame?
+
+It sounds to us both grand and startling to hear of the mighty
+outbreaks from Mount Vesuvius, or to read of glowing lava from a
+volcano in Hawaii pouring in one unbroken stream for miles.
+
+But what shall be thought of rosy flames mounting to a height of fifty
+or a hundred thousand miles above the edge of the sun? What shall be
+thought of a tongue of fire long enough to fold three or four times
+round our solid earth? What shall be thought of the awful rush of
+burning gases, sometimes seen, borne along at the rate of one or two or
+even three hundred miles in a single second across the sun’s surface?
+What shall be thought of the huge dark rents in this raging fiery
+ocean, rents commonly from fifty to one hundred thousand miles across,
+and not seldom more?
+
+Fifty thousand miles! A mere speck, scarcely visible without a
+telescope; yet large enough to hold seven earths like ours flung in
+together. The largest spot measured was so enormous that eighteen
+earths might have been arranged in a row across the breadth of it, like
+huge boulders of rock in a mountain cavern; and to have filled up the
+entire hole about one hundred earths would have been needed.
+
+It is well to grow familiar with certain names given by astronomers to
+certain parts of the sun.
+
+The round shining disk or flat surface, seen by all of us, is called
+the _photosphere_, or “light-sphere.” It has a tolerably well-defined
+edge or “limb,” and dazzles the eye with its intense brightness.
+
+Across the photosphere the spots move, sometimes many, sometimes
+few, in number. Besides the dark spots, there are spots of extreme
+brilliancy, standing out on even that dazzling surface, which causes
+a piece of white-hot iron to look black and cold by contrast. These
+extra-radiant spots which come and go, and at times change with great
+rapidity, are named _faculæ_--a Latin word meaning “torches.”
+
+At the edge of the photosphere astronomers see what has been already
+mentioned, that which is sometimes called the _chromotosphere_, which
+one has named “the _sierra_,” and which another has described as “a
+quivering fringe of fire.” The waves of the sea, on a stormy day, seen
+in the distance rising and breaking the horizon-line, may serve as an
+illustration; only in the sun the waves are of fire, not water. What
+must their height be, to be thus visible at a distance of ninety-three
+millions of miles?
+
+Outside the _sierra_ are seen, at certain seasons, bright,
+“rose-colored prominences” or flames of enormous height. During an
+eclipse, when the dark body of the moon comes between the sun and us,
+exactly covering the photosphere, these red tips stand out distinctly
+beyond the edge of sun and moon. Their changes have been watched, and
+their height repeatedly measured. Some are so lofty that ten little
+earths such as ours might be heaped up, one upon another, without
+reaching to their top. Whether they are in character at all like the
+outbursts from our own volcanoes it is hard to say. To compare the
+two would be rather like comparing a small kitchen fire with a mighty
+iron-smelting furnace. The faculæ, the sierra, and the prominences are
+visible only through a telescope.
+
+Outside these red flames or “prominences” is the corona, commonly
+divided into the inner and outer coronas.
+
+Many different explanations have been offered of this beautiful crown
+of light round the sun, plainly visible to the naked eye during an
+eclipse. But here again we know little, and must be content to watch
+and wait.
+
+
+
+
+CHAPTER III.
+
+WHAT BINDS THE FAMILY TOGETHER?
+
+
+What is it which binds together all the members of the Solar System?
+Ah, what? Why should not the sun at any moment rush away in one
+direction, the earth in a second, the planets in half a dozen others?
+What is there to hinder such a catastrophe? Nothing--except that
+they are all held together by a certain close family tie; or, more
+correctly, by the powerful influence of the head of the family.
+
+This mysterious power which the sun has, and which all the planets
+have also in their smaller degrees, is called Attraction. Sometimes
+it is named Gravitation or Gravity. When we speak, as we often do,
+of the _law_ of attraction or gravitation, we mean simply this--that
+throughout the universe, in things little and great, is found a certain
+wonderful _something_, in constant action, which we call a “law.” What
+the “something” may be, man can not tell; for he knows it only by its
+effects. But these effects are seen everywhere, on all sides, in the
+earth and in the universe. It is well named in being called a “law;”
+for we are compelled to obey it. None but the Divine Lawgiver who made
+this law can for a single moment suspend its working.
+
+What causes an apple to fall to the ground when it drops from the
+branch? Why should it not, instead, rise upwards? Because, of course,
+it is heavy, or has weight. But what _is_ weight? Simply this--that
+the earth draws or drags everything downwards towards herself by the
+power of attraction. Every substance, great or small, light or heavy,
+is made up of tiny atoms. Each one of these atoms attracts or draws all
+the other atoms towards itself; and the closer they are together, the
+more strongly they pull one another.
+
+The atoms in a piece of iron are much closer than the atoms in a piece
+of wood; therefore the iron is called the “more _dense_” of the two,
+and its weight or “mass” is greater. The more closely the atoms are
+pressed together, the greater the number of them in a small space, and
+the more strong the drawing towards the earth; for the earth draws each
+one of these atoms equally. That is only another way of saying that
+a thing is “heavier.” If you drop a stone from the top of a cliff,
+will it rise upwards or float in the air? No, indeed. The pull of the
+earth’s attraction, dragging and still dragging downward, makes it rush
+through the air, with speed quickening each instant, till it strikes
+the ground. Every single atom in every single body _pulls_ every other
+atom, whether far or near. The nearer it is, the stronger always the
+pulling.
+
+We do not always feel this, because the very much greater attraction of
+the earth hides--or smothers, as we may say--the lesser attraction of
+each small thing for another. But though you and I might stand side by
+side upon earth, and feel no mutual attraction, yet if we could mount
+up a few thousands of miles, far away from earth, and float in distant
+space, there we should find ourselves drawn together, and unable to
+remain apart.
+
+Now precisely as an apple falling from a tree and a stone dropping
+from a cliff are dragged downward to the earth, just so our earth and
+all the planets are dragged downwards towards the sun and towards each
+other. The law of the earth’s attraction of all objects on its surface
+to itself was indistinctly suspected a very long time ago; but it was
+the great Newton who first discovered that this same law was to be
+found working among the members of the whole Solar System. The sun
+attracts the earth, and the earth attracts the sun. But the enormous
+size of the sun compared with our earth--like a great nine-foot globe
+beside a tiny one-inch ball--makes our power of attraction to be quite
+lost sight of in his, which is so much greater.
+
+The principle of gravitation is of far wider scope than we have yet
+indicated. We have spoken merely of the attraction of the earth, and
+we have stated that its attraction extends throughout space. But the
+law of gravitation is not so limited. Not only does the earth attract
+every other body, and every other body attract the earth, but each of
+these bodies attracts each other; so that, in its more complete shape,
+the law of gravitation announces that “every body in the universe
+attracts every other body with a force which varies inversely as the
+square of the distance.” It is impossible for us to overestimate the
+importance of this law. It supplies the clue by which we can unravel
+the complicated movements of the planets. It has led to marvelous
+discoveries, in which the law of gravitation has enabled us to
+anticipate the telescope, and, indeed, actually to feel the existence
+of bodies before those bodies have even been seen.
+
+We come now to another question. If the sun is pulling with such power
+at the earth and all her sister planets, why do they not fall down upon
+him? What is to prevent their rolling some day into one of those deep
+rents in his fiery envelope? Did you ever tie a ball to a string, and
+swing it rapidly round and round your head? If you did, you must have
+noticed the steady outward pull of the ball. The heavier the ball, and
+the more rapid its whirl, the stronger the pull will be. Let the string
+slip, and the rush of the ball through the air to the side of the room
+will make this yet more plain. Did you ever carry a glass of water
+quickly along, and then, on suddenly turning a corner, find that the
+water has not turned with you? It has gone on in its former direction,
+leaving the glass, and spilling itself on the floor.
+
+The cause in both cases is the same. Here is another “law of nature,”
+so-called. Though we can neither explain nor understand why and how
+it is so, we see it to be one of the fixed rules of God’s working in
+every-day life throughout his universe. The law, as we see it, seems
+to be this: Everything which is at rest must remain at rest, until
+set moving by some cause outside of, or independent of itself; and
+everything which is once set moving, must continue moving in a straight
+line until checked.
+
+According to this a cannon-ball lying on the ground ought to remain
+there until it is set in motion; and, once set in motion by being fired
+from a cannon, it ought to go on forever. Exactly so--if nothing
+stops it. But the earth’s attraction draws the cannon-ball downward,
+and every time it strikes the ground it is partly checked. Also each
+particle of air that touches it helps to bring it to rest. If there
+were no earth and no air in the question, the cannon-ball might rush on
+in space for thousands of years.
+
+Why did the water get spilled? Because it necessarily continued moving
+in a straight line. Your sudden change of direction compelled the solid
+glass to make the same change, but the liquid water was free to go
+straight on in its former course; so it obeyed this law, and _did_ go
+on. Why did the ball pull hard at the string as you swung it round?
+Because at each instant it was striving to obey this same law, and to
+rush onward in a straight line. The pull of the string was every moment
+fighting against that inclination, and forcing the ball to move in a
+circle.
+
+Just such is the earth’s movement in her yearly journey round the sun.
+The string holding in the ball pictures the sun’s attraction holding
+in the earth. The pulling of the ball outward in order to continue
+its course in a straight line, pictures the pulling of our earth each
+moment to break loose from the sun’s attraction and to flee away into
+distant space.
+
+For the earth is not at rest. Each tick of the clock she has sped
+onward over more than eighteen miles of her pathway through the sky.
+Every instant the sun is dragging, with the tremendous force of his
+attraction, to make her fall nearer to him. Every instant the earth is
+dragging with the tremendous force of her rapid rush, to get away from
+him. These two pullings so far balance each other, or, more strictly,
+so far combine together, that between the two she journeys steadily
+round and round in her nearly circular orbit.
+
+If the sun pulled a little harder she would need to travel a little
+faster, or she would gradually go nearer to him. If the earth went
+faster, and the sun’s attraction remained the same as it is now, she
+would gradually widen her distance. Indeed, it would only be needful
+for the earth to quicken her pace to about five-and-twenty miles a
+second, the sun’s power to draw her being unchanged, and she would then
+wander away from him for ever. Day by day we on our earth should travel
+farther and farther away, leaving behind us all light, all heat, all
+life, and finding ourselves slowly lost in darkness, cold, and death.
+
+For what should we do without the sun? All our light, all our warmth,
+come from him. Without the sun, life could not exist on the earth.
+Plants, herbage, trees, would wither; the waters of rivers, lakes,
+oceans, would turn to masses of ice; animals and men would die. Our
+earth would soon be one vast, cold, forsaken tomb of darkness and
+desolation.
+
+We may not think so, but everything which moves, circulates, and lives
+on our planet is the child of the sun. The most nutritious foods come
+from the sun. The wood which warms us in winter is, again, the sun in
+fragments. Every cubic inch, every pound of wood, is formed by the
+power of the sun. The mill which turns under the impulse of wind or
+water, revolves only by the sun. And in the black night, under the rain
+or snow, the blind and noisy train, which darts like a flying serpent
+through the fields, rushes along above the valleys, is swallowed up
+under the mountains, goes hissing past the stations, of which the pale
+eyes strike silently through the mist,--in the midst of night and cold,
+this modern animal, produced by human industry, is still a child of the
+sun. The coal from the earth which feeds its stomach is solar work,
+stored up during millions of years in the geological strata of the
+globe.
+
+As it is certain that the force which sets the watch in motion is
+derived from the hand which has wound it, so it is certain that all
+terrestrial power proceeds from the sun. It is its heat which maintains
+the three states of bodies--solid, liquid, and gaseous. The last
+two would vanish, there would be nothing but solids; water and air
+itself would be in massive blocks,--if the solar heat did not maintain
+them in the fluid state. It is the sun which blows in the air, which
+flows in the water, which moans in the tempest, which sings in the
+unwearied throat of the nightingale. It attaches to the sides of the
+mountains the sources of the rivers and glaciers, and consequently the
+cataracts and the avalanches are precipitated with an energy which
+they draw directly from him. Thunder and lightning are in their turn
+a manifestation of his power. Every fire which burns and every flame
+which shines has received its life from the sun. And when two armies
+are hurled together with a crash, each charge of cavalry, each shock
+between two army corps, is nothing else but the misuse of mechanical
+force from the same star. The sun comes to us in the form of heat,
+he leaves us in the form of heat; but between his arrival and his
+departure, he has given birth to the varied powers of our globe.
+
+I have spoken before about the old-world notion that our earth was a
+fixed plain, with the sun circling round her. When the truth dawned
+slowly upon some great minds, anxious only to know what really was the
+truth, others made a hard struggle for the older and pleasanter mode
+of thinking. It went with many sorely against the grain to give up all
+idea of the earth being the chief place in the universe. Also there was
+something bewildering and dizzying in the notion that our solid world
+is never for one moment still. But truth won the victory at last. Men
+consented slowly to give up the past dream, and to learn the new lesson
+put before them.
+
+We still talk of the sun rising and setting, and of the stars doing the
+same. This is, however, merely a common form of speech, which means
+just the opposite. For instead of the sun and stars moving, it is the
+earth which moves.
+
+The earth has two distinct movements. Indeed, I ought to say that she
+has three; but we will leave all thought of the third for the present.
+First, she turns round upon her axis once in every twenty-four hours.
+Secondly, she travels round the sun once in about every three hundred
+and sixty-five days and a quarter. No wonder our ancestors were
+startled to learn that the world, which they had counted so immovable,
+was perpetually spinning like a humming-top, and rushing through space
+like an arrow.
+
+You may gain some clear notions as to the daily rising and setting of
+our sun, with the help of an orange. Pass a slender knitting-needle
+through the orange, from end to end, and hold it about a yard distant
+from a single candle in a room otherwise darkened. Let the needle or
+axis slant somewhat, and turn the orange slowly upon it.
+
+The candle does not move; but as the orange turns, the candle-light
+falls in succession upon each portion of the yellow rind. Half of the
+orange is always in shade, and half is always in light; while at either
+side, if a small fly were standing there, he would be passing round out
+of shade into candle-light, or out of candle-light into shade.
+
+Each spot on our earth moves round in turn into half-light, full-light,
+half-light, and darkness; or, in other words, has morning-dawn,
+midday-light, evening twilight, and night. Each spot on our earth would
+undergo regularly these changes every twenty-four hours throughout the
+year, were it not for another arrangement which so far affects this
+that the North and South Poles are, by turns, cut off from the light
+during many months together.
+
+Thus the sun is in the center of the Solar System, turning slowly on
+his axis; and the earth and the planets travel round him, each spinning
+like a teetotum, so as to make the most of his bright warm rays. But
+for this spinning movement of the earth, our day and night, instead of
+being each a few hours long, would each last six months.
+
+You may notice that, as you turn the orange steadily round, the outside
+surface of the skin has to move much more slowly in those parts close
+to the knitting-needle, than in those parts which bulge out farthest
+from it. Near the North and South Poles the surface of our earth
+travels slowly round a very small circle in the course of twenty-four
+hours. But at the equator every piece of ground has to travel about
+twenty-five thousand miles in the same time; so that it rushes along at
+the rate of more than one thousand miles an hour. A man standing on the
+earth at the equator is being carried along at this great speed, not
+_through_ the air, for the whole atmosphere partakes of the same rapid
+motion, but _with_ the air, round and round the earth’s axis.
+
+Now about the other movement of the earth--her yearly journey round the
+sun. While she moves, the sun, as seen from the earth, seems to change
+his place. First he is observed against a background of one group of
+stars, then against a second, then against a third. Not that the stars
+are visible in the daytime when the sun is shining, but their places
+are well known in the heavens; and also they can be noted very soon
+after he sets, or before he rises, so that the constellations nearest
+to him may each day be easily found out.
+
+Of course, in old times the sun was thought to be really taking this
+journey among the stars, and men talked of “the sun’s path” in the
+heavens. This path was named “the Ecliptic,” and we use the word still,
+though we know well that the movements are not really his, but ours.
+
+As the earth’s daily movement causes day and night, so the earth’s
+yearly movement causes spring, summer, autumn, and winter. A few pages
+back I mentioned, in passing, one slight yet important fact which lies
+at the root of this matter about the seasons. The earth, journeying
+round the sun, travels with her axis _slanting_. Put your candle in the
+middle of the table, and stand at one end, holding your orange. Now let
+the knitting-needle, with the orange upon it, so slant that one end
+shall point straight over the candle, towards the upper part of the
+wall at the farther end of the room. Call the upper end so pointing the
+North Pole of your orange. You will see that the candle-light falls
+chiefly upon the upper half of the orange; and as you turn it slowly,
+to picture day and night, you will find that the North Pole has no
+night, and the South Pole has no day. That is summer in the northern
+hemisphere, and winter in the southern.
+
+Walk round next to one side of the table, towards the right hand,
+taking care to let the knitting-needle point steadily still in exactly
+the same direction, not towards the same _spot_, for that would alter
+its direction as you move, but towards the same _wall_. Stop, and you
+will find the candle lighting up one-half of your orange, from the
+North to the South Poles. Turn it slowly, never altering the slope of
+the axis, and you will see that every part of the orange comes by turns
+under the light. This is the Autumnal Equinox, when days and nights all
+over the world are equal in length.
+
+Walk on to the other end of the table, still letting the needle slope
+and point steadily as before. Now the candle-light will shine upon the
+lower or South Pole, and the North Pole will be entirely in the shade.
+This is summer in the southern hemisphere, and winter in the northern.
+
+Pass on to the fourth side of the table, and once more you will find
+it, as at the second side, equal light from North Pole to South Pole.
+This will be the Spring Equinox.
+
+It is an illustration that may be easily practiced. But everything
+depends upon keeping the slant of the needle or axis unchanged
+throughout. If it be allowed to point first to right, and then to left,
+first towards the ceiling, and then towards the wall, the attempt will
+prove a failure.
+
+
+
+
+CHAPTER IV.
+
+THE LEADING MEMBERS OF OUR FAMILY--FIRST GROUP.
+
+
+The chief distinction between stars and planets is, as before said,
+that the stars shine entirely by their own light, while the planets
+shine chiefly, if not entirely, by reflected light. The stars are suns;
+mighty globes of glowing flame. The planets simply receive the light of
+the sun, and shine with a brightness not their own.
+
+A lamp shines by its own light; but a looking-glass, set in the sun’s
+rays and flashing beams in all directions, shines by reflected light.
+In a dark room it would be dark. If there were no sun to shine upon
+Mars or Venus, we should see no brightness in them. The moon is like
+the planets in this. She has only borrowed light to give, and none of
+her own.
+
+Any one of the planets removed to the distance of the nearest fixed
+star, would be invisible to us. Reflected light will not shine nearly
+so far as the direct light of a burning body. There may be thousands or
+millions of planets circling round the stars--those great and distant
+suns--just as our brother-planets circle round our sun. But it is
+impossible for us to see them. The planets which we can see are close
+neighbors, compared with the stars. I do not mean that they are near in
+the sense in which we speak of nearness upon earth. They are only near
+in comparison with what is so very much farther away.
+
+For a while we must now leave alone all thought of the distant stars,
+and try to gain a clear idea of the chief members of our own Family
+Circle--that family circle of which the sun is the head, the center,
+the source of life and warmth and light. There are two ways in which
+astronomers group the planets of the Solar System. One way is to divide
+them into the Inferior Planets, and the Superior Planets.
+
+As the earth travels in her pathway round the sun, two planets travel
+on their pathways round the sun nearer to him than ourselves. If the
+pathway or orbit of our earth were pictured by a hoop laid upon the
+table, with a ball in the center for the sun; then those two planets
+would have two smaller hoops of different sizes _within_ ours; and the
+rest would have larger hoops of different sizes _outside_ ours. The two
+within are called inferior planets, and the rest outside are called
+superior planets.
+
+A round hoop would not make a good picture of an orbit. For the yearly
+pathway of our earth is not in shape perfectly round, but slightly
+oval; and the sun is not exactly in the center, but a little to one
+side of the center. This is more or less the case with the orbits of
+all the planets.
+
+But the laying of the hoops upon the table would give no bad idea of
+the way in which the orbits really lie in the heavens. The orbits of
+all the chief planets do not slope and slant round the sun in all
+manner of directions. They are placed almost in the same _plane_ as it
+is called--or, as we might say, in the same _flat_. In these orbits
+the planets all travel round in the same direction. One may overtake a
+second on a neighboring orbit, and get ahead of him, but one planet
+never goes back to meet another.
+
+In speaking of the orbits, I do not mean that the planets have visible
+marked pathways through the heavens, any more than a swallow has a
+visible pathway through the sky, or a ship a marked pathway through the
+sea. Yet each planet has his own orbit, and each planet so distinctly
+keeps to his own, that astronomers can tell us precisely whereabouts in
+the heavens any particular planet will be, at any particular time, long
+years beforehand.
+
+There is also another mode of grouping the planets, besides dividing
+them into superior and inferior planets. By this other mode we find two
+principal groups or quartets of planets, separated by a zone or belt of
+a great many very small planets.
+
+                      { Mercury.
+  First Group         { Venus.
+                      { Earth.
+                      { Mars.
+
+    The Asteroids or Planetoids.
+
+                      { Jupiter.
+  Second Group        { Saturn.
+                      { Uranus.
+                      { Neptune.
+
+The first four are small compared with the last four, though much
+larger than any in the belt of tiny Asteroids.
+
+It was believed at one time that a planet had been discovered nearer to
+the sun than Mercury, and the name Vulcan was given to it. But no more
+has been seen of Vulcan, and his existence is so doubtful that we must
+not count him as a member of the family without further information.
+
+Mercury is very much smaller than our Earth. The diameter of the earth
+is eight thousand miles, but the diameter of Mercury is only about
+three thousand miles--not even half that of the earth. Being so much
+nearer to the sun than ourselves, the pulling of his attraction is much
+greater, and this has to be balanced by greater speed, or Mercury would
+soon fall down upon the sun. Our distance from the sun is ninety-three
+millions of miles. Mercury’s distance is only about one-third of ours;
+and instead of traveling, like the earth, at the rate of eighteen miles
+each second, Mercury dashes headlong through space at the mad pace
+of twenty-nine miles each second. It is a good thing the earth does
+not follow his example, or she would soon break loose from the sun’s
+control altogether.
+
+The earth takes more than three hundred and sixty-five days, or twelve
+months, to journey round the sun in her orbit. That is what we call
+“the length of our year.” But Mercury’s year is only eighty-eight days,
+or not quite three of our months. No wonder!--when his pathway is so
+much shorter, and his speed so much greater than ours. So Mercury
+has four years to one year on earth; and a person who had lived on
+Mercury as long as five earthly years, would then be twenty years old.
+The increased number of birthdays would scarcely be welcome in large
+families, supposing we could pay a long visit there.
+
+The sun, as seen from Mercury, looks about four and a half times as
+large as from here; the heat and glare being increased in proportion.
+No moon has ever been found, belonging to Mercury.
+
+The planet Mercury is, like the earth and the moon, a globe of dark
+matter which only shines and is visible by the illumination of the
+solar light. Its motion round the central star, which brings it
+sometimes between the sun and us, sometimes in an oblique direction,
+sometimes at right angles, and shows us a part incessantly variable,
+of its illuminated hemisphere, produces in its aspect, as seen in a
+telescope, a succession of phases similar to those which the moon
+presents to us. The cut represent the apparent variations of size and
+the succession of phases, visible in the evening after sunset; when the
+planet attains its most slender crescent, it is in the region of its
+orbit nearest to the earth, and passes between the sun and us; then,
+some weeks afterwards, it emerges from the solar rays and passes again
+through the same series of phases in inverse order, as we see them by
+reversing the figure.
+
+[Illustration: PHASES OF MERCURY BEFORE INFERIOR CONJUNCTION--EVENING
+STAR.]
+
+Venus, the second inferior planet, is nearly the same size as our
+earth. Seen from the earth, she is one of the most brilliant and
+beautiful of all the planets. Her speed is three miles a second faster
+than ours, and her distance from the sun is about two-thirds that of
+our own; so that the orbit of Venus lies half-way between the orbit of
+Mercury and the orbit of the earth. The day of Venus is about half an
+hour shorter than ours. Her year is nearly two hundred and twenty-five
+days, or seven and a half of our months. One or two astronomers have
+fancied that they caught glimpses of a moon near Venus; but this is
+still quite doubtful, and indeed it is believed to have been a mistake.
+
+Venus and Mercury are only visible as morning and evening planets.
+Venus, being farther from the sun, does not go before and follow after
+him quite so closely as Mercury, and she is therefore the longer within
+sight.
+
+When Venus, traveling on her orbit, comes just between the sun and us,
+her dark side is turned towards the earth, and we can catch no glimpse
+of her. When she reaches that part of her orbit which is farthest from
+us, quite on the other side of the sun, her great distance from us
+makes her light seem less. But about half-way round on either side, she
+shows exceeding brilliancy, and that is the best view we can get of her.
+
+Seen through a telescope, Venus undergoes phases like those of Mercury,
+or of our moon. That is to say, we really have “new Venus,” “quarter
+Venus,” “half Venus,” “full Venus,” and so on.
+
+Of all the luminaries in the heavens, the sun and moon excepted, the
+planet Venus is the most conspicuous and splendid. She appears like
+a brilliant lamp amid the lesser orbs of night, and alternately
+anticipates the morning dawn, and ushers in the evening twilight.
+When she is to the westward of the sun, in winter, she cheers our
+mornings with her vivid light, and is a prelude to the near approach
+of the break of day and the rising sun. When she is eastward of that
+luminary, her light bursts upon us after sunset, before any of the
+other radiant orbs of heaven make their appearance; and she discharges,
+in some measure, the functions of the absent moon. The brilliancy of
+this planet has been noticed in all ages, and has been frequently
+the subject of description and admiration both by shepherds and by
+poets. The Greek poets distinguished it by the name of Phosphor,
+“light-bringer,” when it rose before the sun, and Hesperus, “the west,”
+when it appeared in the evening after the sun retired. It is now
+generally distinguished by the name of the Morning and Evening Star.
+
+Next to the orbit of Venus comes the orbit of our own Earth, the third
+planet of the first group.
+
+Mars, the fourth of the inner quartet, but the first of the superior
+planets, is a good deal smaller than Venus or the earth. The name Mars,
+from the heathen god of war, was given on account of his fiery reddish
+color. Mars is better placed than Venus for being observed from earth.
+When he is at the nearest point of his orbit to us, we see him full in
+the blaze of sunlight; whereas Venus, at her nearest point, turns her
+bright face away.
+
+The length of the day of Mars--or, in other words, the time he takes
+to turn upon his axis--is only forty minutes longer than that of
+earth. Mars’ journey round the sun is completed in the course of six
+hundred and eighty-seven days, not much less than two of our years.
+His distance from the sun is about one hundred and forty millions of
+miles, and his speed is fourteen miles a second. We shall find, with
+the increasing distance of each planet, that the slower pace balances
+the lessened amount of the sun’s attraction.
+
+Passing on from Mars, the last of the first group of planets, we reach
+the belt of Asteroids, sometimes called Planetoids, Minor Planets, or
+Telescopic Planets. They are so tiny that Mercury is a giant compared
+with the largest among them.
+
+The zone of space containing all these little planets is more than a
+hundred millions of miles broad. Their orbits do not lie flat in almost
+the same plane, but slant about variously in a very entangled fashion.
+If a neat model were made of this zone, with a slender piece of wire to
+represent each orbit, it would be found impossible to lift up one wire
+without pulling up all the rest with it. Those asteroids lying nearest
+to the sun take about three of our years to travel round him, and those
+lying farthest take about six of our years.
+
+New members of the group are very often found. The number of asteroids
+now known amounts to about three hundred and twenty. Ceres is estimated
+by Professor Barnard, of the Yerkes Observatory, Chicago University, to
+be six hundred miles in diameter. Vesta is about two hundred and fifty
+miles in diameter. Meta, on the other hand, is less than seventy-five
+miles. There are some smaller ones that do not measure twenty miles in
+diameter, and it is probable that there are many which are so small as
+to be absolutely invisible to the best telescopes, and which measure
+only a few hundred rods in diameter. Twenty thousand Vestas would be
+needed to make one globe equal to our earth in size.
+
+Are they _worlds_? Why not? Is not a drop of water, shown in the
+microscope, peopled with a multitude of various beings? Does not a
+stone in a meadow hide a world of swarming insects? Is not the leaf
+of a plant a world for the species which inhabit and prey upon it?
+Doubtless among the multitude of small planets there are those which
+must remain desert and sterile, because the conditions of life (of any
+kind) are not found united. But we can not doubt that on the majority
+the ever-active forces of nature have produced, as in our world,
+creations appropriate to these minute planets. Let us repeat, moreover,
+that for nature there is neither great nor little. And there is no
+necessity to flatter ourselves with a supreme disdain for these little
+worlds; for in reality the inhabitants of Jupiter would have more right
+to despise us than we have to despise Vesta, Ceres, Pallas, or Juno.
+The disparity is greater between Jupiter and the earth than between the
+earth and these planets. A world of two, three, or four hundred miles
+in diameter is still a continent worthy to satisfy the ambition of a
+Xerxes or a Tamerlane.
+
+
+
+
+CHAPTER V.
+
+THE LEADING MEMBERS OF OUR FAMILY--SECOND GROUP.
+
+
+Leaving behind us the busy zone of planetoids, hurrying round and round
+the sun in company, we cross a wide gap, and come upon a very different
+sight.
+
+The distance from the sun which we have now reached is little less than
+four hundred and fifty millions of miles, or about five times as much
+as the earth’s distance; and the sun in the heavens shows a diameter
+only one-fifth of that which we are accustomed to see. Slowly--yet not
+slowly--floating onwards through space, in his far-off orbit, we find
+the magnificent planet Jupiter.
+
+Is eight miles each second slow progress? Compared with the wild whirl
+of little Mercury, or even compared with the rate of our own earth’s
+advance, we may count it so; but certainly not, compared with our
+notions of speed upon earth. Eight miles each second is five hundred
+times as fast as the swiftest express-train ever made by man. No mean
+pace that for so enormous a body. For Jupiter is the very largest of
+all the members of the Solar System except the sun himself--quite
+the eldest brother of the family. His diameter is about eighty-five
+thousand miles, his axis being nearly eleven times as long as that of
+earth. Though in proportion to his great bulk not nearly so heavy as
+our earth, yet his bulk is so vast that more than twelve hundred earths
+would be needed to make one Jupiter.
+
+It must not, however, be forgotten that there is a certain amount of
+uncertainty about these measurements of Jupiter. He seems to be so
+covered with a dense atmosphere and heavy clouds that it is quite
+impossible for us to learn the exact size of the solid body within.
+
+Jupiter does not travel alone. Borne onwards with him, and circling
+steadily around him, are five moons; the smallest with a probable
+diameter of about one hundred miles; one about the same size as our
+own moon, and the others all larger. The nearest of the five, though
+distant from the center of the planet over one hundred and twelve
+thousand miles, revolves about him in twelve hours; the second, though
+farther from Jupiter than our moon from the earth, speeds round him
+in less than two of our days. The most distant, though over a million
+miles away, takes scarcely seventeen days to accomplish its long
+journey. Jupiter and his moons make a little system by themselves--a
+family circle within a family circle.
+
+Like the smaller planets, Jupiter spins upon his axis; and he does this
+so rapidly that, notwithstanding his great size, his day lasts only ten
+hours, instead of twenty-four hours like ours. But if Jupiter’s day
+is short, his year is not. Nearly twelve of our years pass by before
+Jupiter has traveled once completely round the sun. So a native of
+earth who had just reached his thirty-seventh year, would, on Jupiter,
+be only three years old.
+
+Passing onward from Jupiter, ever farther and farther from the sun,
+we leave behind us another vast and empty space--empty as we count
+emptiness, though it may be that there is in reality no such thing as
+emptiness throughout the length and breadth of the universe. The width
+of the gap which divides the pathway of Jupiter from the pathway of his
+giant brother-planet Saturn is nearly five times as much as the width
+of the gap separating the earth from the sun. The distance of Saturn
+from the sun is not much less than double the distance of Jupiter.
+
+With this great space in our rear, we come upon another large and
+radiant planet, the center, like Jupiter, of another little system;
+though it can only be called “little” in comparison with the much
+greater Solar System of which it forms a part.
+
+Saturn’s diameter is less than that of Jupiter, but the two come near
+enough to be naturally ranked together. Nearly seven hundred earths
+would be needed to make one globe as large as Saturn. But here again
+the dense and cloudy envelope makes us very uncertain about the
+planet’s actual size. Saturn is like Jupiter in being made of lighter
+materials than our earth; and also in his rapid whirl upon his axis,
+the length of his “day” being only ten and a half of our hours.
+
+From Jupiter’s speed of eight miles each second, we come down in the
+case of Saturn to only five miles each second. And Jupiter’s long
+annual journey looks almost short, seen beside Saturn’s long journey
+of thirty earthly years. A man aged sixty, according to our fashion of
+reckoning time, would on Saturn have just kept his second birthday.
+
+The system or family of Saturn is yet more wonderful than that of
+Jupiter. Not five only but eight moons travel ceaselessly round Saturn,
+each in its own orbit; and in addition to the eight moons, he has
+revolving round him three magnificent rings. These rings, as well as
+the moons, shine, not by their own brilliancy, for they have none, but
+by borrowed sunlight. The farthest of the moons wanders in his lonely
+pathway about two millions of miles away from Saturn. The largest of
+them is believed to be about the same size as the planet Mars. Of the
+three rings circling round Saturn, almost exactly over his equator, the
+inside one is dusky, purplish, and transparent; the one outside or over
+that is very brilliant; and the third, outside the second, is rather
+grayish in hue.
+
+Another vast gap--more enormous than the last. It is a wearisome
+journey. From the orbit of Jupiter to the orbit of Saturn at their
+nearest points, was five times as much as from the sun to the earth.
+But from the orbit of Saturn to the orbit of Uranus, the next member of
+the sun’s family, we have double even that great space to cross.
+
+Still, obedient to the pulling of the sun’s attractive power, Uranus
+wanders onward in his wide pathway round the sun, at the rate of four
+miles a second. Eighty-four of our years make one year of Uranus.
+This planet has four moons, and thus forms a third smaller system
+within the Solar System; but he may have other satellites also, as yet
+undiscovered. In size he is seventy-four times as large as our earth.
+
+One more mighty chasm of nine hundred millions of miles, for the same
+distance which separates the pathway of Saturn from the pathway of
+Uranus, separates also the pathway of Uranus from the pathway of
+Neptune. Cold, and dark, and dreary indeed seems to us the orbit on
+which this banished member of our family circle creeps round the sun,
+in the course of one hundred and sixty-five years, at the sluggish rate
+of three miles a second.
+
+On the planet Saturn, the quantity of light and heat received from
+the sun is not much more than a hundredth part of that which we are
+accustomed to receive on earth. But by the time we reach Neptune, the
+great sun has faded and shrunk in the distance until to our eyes he
+looks only like an exceedingly brilliant and dazzling star.
+
+We know little of this far-off brother, Neptune, except that he is
+rather larger than Uranus, being one hundred and five times as big as
+the earth; that he has at least one moon; and also that, like Uranus,
+he is made of materials lighter than those of earth, but heavier than
+those of Jupiter or Saturn.
+
+After all, it is no easy matter to gain clear ideas as to sizes and
+distances from mere statements of “so many miles in diameter,” and “so
+many millions of miles away.” A “million miles” carries to the mind a
+very dim notion of the actual reality.
+
+Now if we can in imagination bring down all the members of the Solar
+System to a small size, keeping always the same proportions, we may
+find it a help. “Keeping the same proportions” means that all must be
+lessened alike, all must be altered in the same degree. Whatever the
+supposed size of the earth may be, Venus must be still about the same
+size as the earth, Saturn seven hundred times as large, and so on.
+Also, whatever the distance of the earth from the sun, in miles, or
+yards, or inches, Mercury must still be one-third as far, Jupiter still
+five times as far, and thus with the rest.
+
+First, as to size alone. Suppose the earth is represented by a small
+globe, exactly three inches in diameter. It will be a very small globe.
+Not only men and houses, but mountains, valleys, seas, will all have to
+be reduced to so minute a size, as to be quite invisible to the naked
+eye.
+
+Fairly to picture the other members of the Solar System, in due
+proportion, you will have them as follows:
+
+Mercury and Mars will be balls smaller than the earth, and Venus nearly
+the same size of the earth. Uranus and Neptune will be each somewhere
+about a foot in diameter. Saturn will be twenty-eight inches and
+Jupiter thirty-two inches in diameter. The sun will be a huge dazzling
+globe, _twenty-six feet_ in diameter. No wonder he weighs seven hundred
+and fifty times as much as all his planets put together.
+
+Next let us picture the system more exactly on another and smaller
+scale. First, think of the sun as a brilliant globe, about nine feet,
+or three yards, in diameter, floating in space.
+
+About one hundred yards from the sun travels a tiny ball, not half
+an inch in diameter, passing slowly round the sun--slowly, because
+as sizes and distances are lessened, speed must in due proportion be
+lessened also. This is Mercury. About two hundred yards from the sun
+travels another tiny ball, one inch in diameter. This is Venus. Nearly
+a quarter of a mile from the sun travels a third tiny ball, one inch
+again in diameter; and at a distance of two feet and a half from it a
+still smaller ball, one quarter of an inch in diameter, journeys round
+it and with it. These are the earth and the moon. About half as far
+again as the last-named ball, travels another, over half an inch in
+diameter. This is Mars.
+
+Then comes a wide blank space, followed by a large number of minute
+objects, no bigger than grains of powder, floating round the sun in
+company. These are the Asteroids. Another wide blank space succeeds the
+outermost of them.
+
+About one mile distant from the sun journeys a globe, ten inches in
+diameter. Round him, as he journeys, there travel five smaller balls,
+the largest of which is about the third of an inch in diameter. Their
+distances from the bigger globe vary from one and a third to twelve and
+a half feet. These are Jupiter and his moons.
+
+Nearly two miles distant from the sun journeys another globe, about
+eight and a half inches in diameter. Eight tiny balls and three
+delicate rings circle round him as he moves. These are Saturn and his
+belongings. About four miles distant from the sun journeys another
+globe, four inches in diameter, with four tiny balls accompanying
+him--Uranus and his moons. Lastly, at a distance of six miles from
+the sun, one more globe, not much larger than the last, with one tiny
+companion, pursues his far-off pathway.
+
+These proportions as to size and distance will serve to give a clear
+idea of the Solar System.
+
+
+
+
+CHAPTER VI.
+
+THE MOON.
+
+
+Come, and let us pay a visit to the moon. We seem to feel a personal
+interest in her, just because she is, in so peculiar a sense, our own
+friend and close attendant. The sun shines for us; but, then, he shines
+for all the members of the Solar System. And the stars--so many as we
+can see of them--shine for us too; but no doubt they shine far more
+brilliantly for other and nearer worlds. The moon alone seems to belong
+especially to ourselves.
+
+Indeed, we are quite in the habit of speaking about her as “our moon.”
+Rather a cold and calm friend, some may think her, sailing always
+serenely past, whatever may be going on beneath her beams; yet she has
+certainly proved herself constant and faithful in her attachment.
+
+We have not very far to travel before reaching her,--merely about
+two hundred and forty thousand miles. That is nothing, compared with
+the weary millions of miles which we have had to cross to visit some
+members of our family. A rope two hundred and forty thousand miles
+long would fold nearly ten times round the earth at the equator. You
+know the earth’s diameter--about eight thousand miles. If you had
+thirty poles, each eight thousand miles long, and could fasten them all
+together, end to end, one beyond another, you would have a rod long
+enough to reach from the earth to the moon.
+
+Let us take a good look at her before starting. She is very beautiful.
+That soft silvery light, so unlike sunlight or gaslight, or any other
+kind of light seen upon earth, has made her the darling of poets and
+the delight of all who love nature. Little children like to watch
+her curious markings, and to make out the old man with his bundle of
+sticks, or the eyes, nose, and mouth of the moon--not dreaming what
+those markings really are. And in moods of sadness, how the pure calm
+moonlight seems to soothe the feelings! Who would suppose that the
+moon’s beauty is the beauty rather of death than of life?
+
+[Illustration: APPEARANCE OF THE FULL MOON.]
+
+The stars have not much chance of shining through her bright rays. It
+is well for astronomers that she is not always at the full. But when
+she is, how large she looks--quite as large as the sun, though in
+reality her size, compared with his, is only as a very small pin’s
+head compared with a school globe two feet in diameter. Her diameter is
+little more than two thousand miles, or one quarter that of our earth;
+and her whole surface, spread out flat, would scarcely equal North and
+South America, without any of the surrounding islands.
+
+The reason she looks the same size as the sun, is that she is so very
+much nearer. The sun’s distance from us is more than one-third as many
+_millions_ of miles as the moon’s distance is _thousands_ of miles.
+This makes an enormous difference.
+
+We call our friend a “moon,” and say that she journeys round the earth,
+while the earth journeys round the sun. This is true, but it is only
+part of the truth. Just as certainly as the earth travels round the
+sun, so the moon also travels round the sun. And just as surely as
+the earth is a planet, so the moon also is a planet. It is a common
+mode of expression to talk about “the earth and her satellite.” A no
+less correct, if not more correct, way would be to talk of ourselves
+as “a pair of planets,” journeying round the same sun, each pulled
+strongly towards him, and each pulling the other with a greater or less
+attraction, according to her size and weight. For the sun actually does
+draw the moon with more force than that with which the earth draws her.
+Only as he draws the earth with the same sort of force, and nearly in
+the same degree, he does not pull them apart.
+
+The moon, like the other planets, turns upon her axis. She does this
+very slowly, however; and most singularly she takes exactly the same
+time to turn once upon her axis that she does to travel once round
+the earth. The result of this is, that we only see one face of the
+moon. If she turned upon her axis, and journeyed round the earth in two
+different lengths of time, or if she journeyed round us and did not
+turn upon her axis at all, we should have views of her on all sides,
+as of other planets. But as her two movements so curiously agree, it
+happens that we always have one side of the moon towards us, and never
+catch a glimpse of the other side.
+
+And now we are ready to start on our journey of two hundred and forty
+thousand miles. An express train, moving ceaselessly onward night and
+day, at the rate of sixty miles an hour, would take us there in about
+five months and a half. But no line of rails has ever yet been laid
+from the earth to the moon, and no “Flying Dutchman” has ever yet plied
+its way to and fro on that path through the heavens. Not on the wings
+of steam, but on the wings of imagination, we must rise aloft. Come--it
+will not take us long. We shall pass no planets or stars on the road,
+for the moon lies nearer to us than any other of the larger heavenly
+bodies.
+
+Far, far behind us lies the earth, and beneath our feet, as we descend,
+stretch the broad tracts of moonland. For “downward” now means towards
+the moon, and away from the distant earth.
+
+What a strange place we have reached! The weird, ghastly stillness
+of all around, and the glaring, dazzling, cloudless heat, strike us
+first and most forcibly. Nothing like this heat have we ever felt on
+earth. For the close of the moon’s long day--on this side of its
+globe--is approaching, and during a whole fortnight past the sun’s
+fierce rays have been beating down on these shelterless plains. Talk
+of sweltering tropics on earth! What do you call _this_ heat? Look
+at the thermometer: how the quicksilver is rising! Well, that is not
+a common thermometer which we have brought with us. The mercury has
+stopped--three hundred degrees above boiling water!
+
+Not a cloud to be seen overhead; only a sky of inky blackness, with a
+blazing sun, and thousands of brilliant stars, and the dark body of
+our own earth, large and motionless, and rimmed with light. Seen from
+earth, sun and moon look much the same size; but seen from the moon,
+the earth looks thirteen times as large as our full moon. Not even a
+little mistiness in the air to soften this fearful glare! Air! why,
+there is no air; at least not enough for any human being to breathe
+or feel. If there were air, the sky would be blue, not black, and the
+stars would be invisible in the daytime. It looks strange to see them
+now shining beside the sun.
+
+And then, this deadly stillness! Not a sound, not a voice, not a murmur
+of breeze or water. How could there be? Sound can not be carried
+without air, and of air there is none. As for breeze--wind is moving
+air, and where we have no air we can have no wind. As for water--if
+there ever was any water on the moon, it has entirely disappeared. We
+shall walk to and fro vainly in search of it now. No rivers, no rills,
+no torrents in those stern mountain ramparts rising on every side. All
+is craggy, motionless, desolate.
+
+How very, very slowly the sun creeps over the black sky! And no
+marvel, since a fortnight of earth-time is here but one day, answering
+to twelve hours upon earth. Can not we find shelter somewhere from
+this blazing heat? Yonder tall rock will do, casting a sharp shadow
+of intense blackness. We never saw such shadows upon earth. There the
+atmosphere so breaks and bends and scatters about the light, that
+outlines of shadows are soft and hazy, even the clearest and darkest of
+them, compared with this.
+
+When will the sun go down? But he is well worth looking at meanwhile.
+How magnificent he appears, with his pure radiant photosphere, fringed
+by a sierra of dazzling pink and white, orange and gold, purple
+and blue. For here no atmosphere lies between to blend all into
+yellow-white brightness. And how plainly stand out those prominences
+or tongues of tinted flame, not merely rose-colored, as seen from
+earth, but matching the sierra in varying hues; while beyond spreads
+a gorgeous belt of pink and green, bounded by lines and streams of
+delicate white light, reaching far and dying slowly out against the jet
+background. The black spots on the face of the sun are very distinct,
+and so also are the brilliant faculæ.
+
+We must take a look around us now at moonland, and not only sit gazing
+at the sun, though such a sky may well enchain attention. How unlike
+our earthly landscapes! No sea, no rivers, no lakes, no streams, no
+brooks, no trees, bushes, plants, grass, or flowers; no wind or breeze;
+no cloud or mist or thought of possible rain; no sound of bird or
+insect, of rustling leaves or trickling water. Nothing but burning,
+steadfast, changeless glare, contrasting with inky shadows; sun and
+earth and stars in a black heaven above; silent, desolate mountains and
+plains below.
+
+For though we stand here upon a rough plain, this moon is a mountainous
+world. Ranges of rugged hills stretch away in the distance, with
+valleys lying between--not soft, green, sloping, earthly valleys, but
+steep gorges and precipitous hollows, all white dazzle and deep shade.
+
+But the mountains do not commonly lie in long ranges, as on earth. The
+surface of the moon seems to be dented with strange round pits, or
+craters, of every imaginable size. We had a bird’s-eye view of them as
+we descended at the end of our long journey moonward. In many parts
+the ground appears to be quite honeycombed with them. Here are small
+ones near at hand, and larger ones in the distance. The smaller craters
+are surrounded by steep ramparts of rock, the larger ones by circular
+mountain-ranges. We have nothing quite like them on earth.
+
+Are they volcanoes? So it would seem; only no life, no fire, no action,
+remain now. All is dead, motionless, still. Is this verily a blasted
+world? Has it fallen under the breath of Almighty wrath, coming out
+scorched and seared? Is it simply passing through a certain burnt-out,
+chilled phase of existence, through which other planets also pass, or
+will pass, at some stage of their career? Who can tell?
+
+We will move onward, and look more closely at that towering mass of
+rugged rocks, beyond which the sun will by and by go down. Long jetty
+shadows lie from them in this direction. No wonder astronomers on
+earth can through their telescopes plainly see these black shadows
+contrasting with the glaring brightness on the other side.
+
+A “mass of rocks” I have said; but as, with our powers of rapid
+movement, we draw near, we find a range of craggy mountains sweeping
+round in a vast circle. Such a height in Switzerland would demand many
+hours of hard climbing. But on this small globe attraction is a very
+different matter from what it is on earth; our weight is so lessened
+that we can leap the height of a tall house without the smallest
+difficulty. No chamois ever sprang from peak to peak in his native
+Switzerland with such amazing lightness as that with which we now
+ascend these mighty rocks.
+
+[Illustration: ONE FORM OF LUNAR CRATER.]
+
+Ha! what a depth on the other side! We stand looking down into one of
+the monster craters of the moon. A sheer descent of at least eleven
+thousand feet would land us at the bottom. Why, Mont Blanc itself
+is only about fifteen thousand feet in height. And what a crater!
+Fifty-six miles across in a straight line, from here to the other side,
+with these lofty rugged battlements circling round, while from the
+center of the rough plain below a sharp, cone-shaped mountain rises to
+about a quarter of the height of the surrounding range.
+
+It is a grand sight; peak piled upon peak, crag upon crag, sharp rifts
+or valleys breaking here and there the line of the narrow, uplifted
+ledge; all wrapped in silent and desolate calm. There are many such
+craters as this on the moon, and some much larger.
+
+The sun slowly nears his setting, and sinks behind the opposite range.
+How we shiver! The last ray of sunlight has gone and already the ground
+is pouring out its heat into space, unchecked by the presence of air
+or clouds. The change takes place with marvelous quickness. A deadly
+chill creeps over all around. A whole fortnight of earth-time must pass
+before the sun’s rays will again touch this spot. Verily the contrasts
+of climate in the moon, during the twelve long days and nights which
+make up her year, are startling to human notions.
+
+But though the sun is gone we are not in darkness. The stars shine with
+dazzling brightness, and the huge body of the earth, always seeming to
+hang motionless at one fixed point in the sky, gives brilliant light,
+though at present only half her face is lit up and half is in shadow.
+Still her shape is plainly to be seen, for she has ever round her a
+ring of light, caused by the gathered shining of stars as they pass
+behind her thick atmosphere. She covers a space on the sky more than a
+dozen times as large as that covered by the full moon in our sky.
+
+[Illustration: THE EARTH AS SEEN FROM THE MOON.]
+
+It would be worth while to stay here and watch the half-earth grow
+into magnificent full-earth. But the cold is becoming fearful--too
+intense for even the imagination to endure longer. What must be the
+state of things on the other side of the moon, where there is no bright
+earth-light to take the place of the sun’s shining, during the long two
+weeks’ night of awful chill and darkness?
+
+It seems probable that a building on the moon would remain for century
+after century just as it was left by the builders. There need be no
+glass in the windows, for there is no wind and no rain to keep out.
+There need not be fireplaces in the rooms, for fuel can not burn
+without air. Dwellers in a city in the moon would find that no dust
+can rise, no odors be perceived, no sounds be heard. Man is a creature
+adapted for life in circumstances which are very narrowly limited.
+A few degrees of temperature, more or less; a slight variation in
+the composition of air, the precise suitability of food, make all
+the difference between health and sickness, between life and death.
+Looking beyond the moon, into the length and breadth of the universe,
+we find countless celestial globes, with every conceivable variety of
+temperature and of constitution. Amid this vast number of worlds with
+which space teems, are there any inhabited by living beings? To this
+great question science can make no response save this: We can not tell.
+
+Time for us to wend our way homewards from this desolate hundred-fold
+arctic scene. We have more to learn by and by about our friend and
+companion. For the present--enough.
+
+
+
+
+CHAPTER VII.
+
+VISITORS.
+
+
+We come next to the very largest members of our Solar System.
+
+From time to time in past days--and days not very long past
+either--people were startled by the sight of a long-tailed star, moving
+quickly across the sky, called a comet. We see such long-tailed stars
+still, now and then; but their appearance no longer startles us.
+
+It is hardly surprising, however, that fears were once felt. The great
+size and brilliancy of some of these comets naturally caused large
+ideas to be held as to their weight, and the general uncertainty about
+their movements naturally added to the mysterious notions afloat with
+respect to their power of doing harm.
+
+A collision between the earth and a comet seemed no unlikely event; and
+if it happened--what then? Why, then, of course, the earth would be
+overpowered, crushed, burnt up, destroyed. So convinced were many on
+this point that the sight of a comet and the dread of the coming “end
+of the world” were fast bound together in their minds.
+
+Even when astronomers began to understand the paths of some of the
+comets, and to foretell their return at certain dates, the old fear
+was not quickly laid to rest. So late as the beginning of the present
+century, astronomers having told of an approaching comet, other people
+added the tidings of an approaching collision. “If a collision, then
+the end of the world,” was the cry; and one worthy family, living and
+keeping a shop in a well-known town on the south coast of England,
+packed up and fled to America--doubtless under full belief that the
+destruction of the Old World would not include the destruction of the
+New.
+
+The nature of these singular bodies is somewhat better known in the
+present day; yet even now, among all the members of the Solar System,
+they are perhaps the ones about which we have most to learn. The
+nucleus, or bright and star-like spot, which, with the surrounding
+coma or “hair,” we sometimes call the “head” of the comet, is the
+densest and heaviest part of the whole. The comets are of immense size,
+sometimes actually filling more space than the sun himself, and their
+tails stream often for millions of miles behind them; nevertheless,
+they appear to be among the lightest of the members of the Solar System.
+
+This excessive lightness greatly lessens the comet’s power of
+harm-doing. In the rebound from all the old exaggerated fears, men
+laughed at the notion of so light and delicate a substance working any
+injury whatever, and even declared that a collision might take place
+without people on earth being aware of the fact. It is now felt that
+we really know too little about the nature of the said substance to
+be able to say what might or might not be the result of a collision.
+A certain amount of injury to the surface of the earth might possibly
+take place. But of the “end of the world,” as likely to be brought
+about by any comet in existence, we may safely banish all idea.
+
+The word “comet” means “a hairy body,” the name having been given from
+the hairy appearance of the light around the nucleus. About seventeen
+hundred different comets have been seen at different times by men--some
+large, some small; some visible to the naked eye, but most of them only
+visible through telescopes. These hundreds are, there is no doubt, but
+a very small number out of the myriads ranging through the heavens.
+
+If you were seated in a little boat in mid-ocean, counting the number
+of fishes which in one hour passed near enough in the clear water for
+your sight to reach them, you might fairly conclude, even if you did
+not know the fact, that for every single fish which you could see,
+there were tens of thousands which you could not see.
+
+Reasoning thus about the comets, as we watch them from our earth-boat
+in the ocean of space, we feel little doubt that for each one which we
+can see, millions pass to and fro beyond reach of our vision. Indeed,
+so long ago as the days of Kepler, that great astronomer gave it as his
+belief that the comets in the Solar System, large and small, were as
+plentiful as the fishes in the sea. And all that modern astronomers can
+discover only tends to strengthen this view.
+
+Why should the comets be called “visitors?” I call them so simply
+because many of them _are_ visitors. Some, it is true, belong to the
+Solar System. But even in their case, strong doubts are felt whether
+they were not once visitors from a distance, caught in the first
+instance by the attraction of one of the larger planets, and retained
+thenceforward, for a time at least, by the strong attraction of the sun.
+
+[Illustration: PASSAGE OF THE EARTH AND THE MOON THROUGH THE TAIL OF A
+COMET.]
+
+Every comet, like every planet, has his own orbit or pathway in the
+heavens, though the kind of orbit varies with different comets. There
+are, first, those comets which travel round and round the sun in
+“closed orbits”--that is, in a ring with joined ends. Only the ring is
+always oval, not round. There are, secondly, those which travel in an
+orbit which _may_ be closed; but if so, the oval is so long and narrow,
+and the farther closed end is at so great a distance, that we can not
+speak certainly. There are, thirdly, those which decidedly are mere
+visitors. They come from the far-off star-depths, flash once with their
+brilliant trains of light through our busy Solar System, causing some
+little excitement by the way, and go off in another direction, never to
+return.
+
+Only a small part of the orbits of these comets can be seen from
+earth; but by careful attention astronomers learn something of the
+shape of the curve in which they travel. It is in that way possible to
+calculate, sometimes certainly, and sometimes uncertainly, whether a
+comet may be expected to return, or whether we have seen him for the
+first and the last time. By looking at _part_ of a curve, the rest of
+which is hidden from us, we are able to judge whether that part belongs
+to a circle or an oval, or whether the two ends pass away in different
+directions, and do not join.
+
+The comets, whether members of our family circle or visitors from a
+distance, are altogether very perplexing. They are often extremely
+large, yet they are always extremely light. They reflect the sun’s
+brightness like a planet, yet in some measure they seem to shine by
+their own light, like a star. They obey the attraction of the sun, yet
+he appears to have a singular power of driving the comets’ tails away
+from himself.
+
+For, however rapidly the comet may be rushing round the sun, and
+however long the tail may be, it is almost always found to stream in an
+opposite direction from the sun. An exception to this rule was seen in
+the case of a certain comet with two tails, one of which did actually
+point towards the sun; but the inner tail may have been only a “jet” of
+unusual length, like in kind to the smaller jets often thus poured out
+from the nucleus.
+
+Very curious changes take place in comets as they journey, especially
+as they come near the sun. One was seen in the course of a few days to
+lose all his hair, and also his tail. Another was seen to break into
+two pieces, both of which pieces at last disappeared. Sometimes the one
+tail divides into two tails.
+
+Traveling, as the comets do, from intense cold into burning heat,
+they are very much affected by the violent change of climate. For the
+paths of the comets are such long ovals, or ellipses, that, while they
+approach the sun very closely in one part of their “year,” they travel
+to enormous distances in the other part.
+
+“Halley’s Comet,” which takes seventy-six of our years to journey round
+the sun, comes nearer to him than Venus, and goes farther away from him
+than Neptune. As this comet draws gradually closer, he has to make up
+for the added pull of the sun’s increasing attraction by rushing onward
+with greater and greater rapidity, till he whirls madly past the sun,
+and then, with slowly slackening speed, journeys farther and farther
+away, creeps at length lazily round the farther end of his orbit in the
+chill, dark, neighborhood of Neptune, and once more travels towards the
+sun with growing haste.
+
+“Encke’s Comet” has a year of only three and a half of our years, so
+he may be said to live quite in our midst. But many comets travel much
+farther away than the one named after Halley. It is calculated of some
+that, if they ever return at all, it can not be for many hundreds of
+years.
+
+[Illustration: PASSAGE OF THE COMET OF 1843 CLOSE TO THE SUN (FEBRUARY
+27TH, 10 HOURS, 29 MINUTES.)]
+
+“Newton’s Comet,” seen about two centuries ago, has a journey to
+perform of such length that he is not expected again to appear for
+several thousand years. Yet, at the nearest point in his orbit, he
+approached the sun so closely, that the heat which he endured was
+about two thousand times that of red-hot iron. Changes were seen to be
+taking place in his shape, as he drew near to the sun, and disappeared.
+Four days he was hidden in the sun’s rays. He vanished, with a tail
+streaming millions of miles behind him. He made his appearance again
+with a tail streaming millions of miles in front of him. But how this
+wonderful movement took place is beyond man’s power to explain.
+
+The comet of 1843 was one of the most attractive seen during the
+present century. It was first observed in March, and it appeared with
+a suddenness which had quite a startling effect. It was an imposing
+object in the southern regions. The comet was seen in Italy on the 28th
+of February; at Washington, on the 6th of March; at Oporto, on the
+14th; but owing to unfavorable weather, it was not visible in England,
+or any of the northern countries of Europe, previous to the 17th. A
+little after sunset on that day the tail was observed in the western
+sky, but the head had already sunk below the horizon. The whole of the
+comet appeared on the following evenings for a short time, for it was
+traveling away from the sun with great velocity, having doubled the
+solar orb before it became visible; and about the beginning of April it
+finally disappeared.
+
+The appearance of this startling stranger, as observed at Washington,
+is thus described by Lieutenant Maury, of the Hydrographical Office in
+that city: “On Monday morning, March 6th, our attention was called to
+a paragraph in the newspapers, stating that a comet was visible near
+the sun at midday with the naked eye. The sky was clear; but not being
+able to discover any thing with the unassisted eye, recourse was had to
+the telescope, but with no better success. About sunset in the evening,
+the examination was renewed with great diligence, but to no purpose.
+The last faint streak of day gilded the west; beautiful and delicate
+fleeces of cloud curtained the bed of the sun; the upper sky was
+studded with stars, and all hopes of seeing the comet that evening had
+vanished. Soon after we had retired, the officer of the watch announced
+its appearance in the west. The phenomenon was sublime and beautiful.
+The needle was greatly agitated, and a strongly marked pencil of light
+was streaming up from the path of the sun in an oblique direction to
+the southward and eastward; its edges were parallel. It was 30° long.
+Stars could be seen twinkling through it, and no doubt was at first
+entertained that this was the tail of the comet.”
+
+The tail, as seen in northerly countries, spread over an arc of the
+heavens of about 40°; but in southern latitudes it extended to from 60°
+to 70°. It had an absolute length of two hundred millions of miles; so
+that, had it been coiled around the earth like a serpent, it would have
+girdled it eight thousand times at the equator. This comet approached
+still nearer the sun than that of Newton, and must therefore have been
+exposed to a heat of greater intensity. Its center is computed to
+have been within a hundred thousand miles of the solar surface; and
+according to Sir John Herschel’s calculations, it was then exposed to a
+heat equal to that which would be received by an equal portion of the
+earth’s surface, if it were subject to the influence of forty-seven
+thousand suns, placed at the common distance of the actual sun. It is
+difficult to conceive how a flimsy substance in such circumstances
+could escape being entirely dissipated. But such was its velocity that
+it wheeled round the sun in less than two hours.
+
+The general question of the probability and the consequences of a
+collision with a comet may be legitimately entertained. With reference
+to the first point, it can not be denied that collision is possible;
+but, at the same time, it is so extremely improbable that it may be
+safely dismissed from apprehension. The fact of such an event not
+having been experienced in the known course of terrestrial history is
+surely some guarantee against its occurrence. Another may be found in
+the small volume of the earth and of comets when compared with the
+immensity of space in which they move. According to the well-understood
+principles of probabilities, Arago has calculated that, upon the
+appearance of a new comet, the odds are as 281,000,000 to 1, that it
+will not strike against our globe. But even supposing collision to
+occur, all that we know of the constitution of comets justifies the
+conclusion that the encounter would involve no terrestrial convulsion,
+nor any result incompatible with full security to life and happiness.
+
+So much for the largest members of our circle--largest, though
+lightest; members some, visitors others. Now we turn to the smallest.
+
+
+
+
+CHAPTER VIII.
+
+LITTLE SERVANTS.
+
+
+If you walk out any night after dark, and watch the bright stars
+shining in a clear sky--shining as they have done for ages past--you
+will probably see, now and then, a bright point of light suddenly
+appear, dart along a little distance, and as suddenly vanish.
+That which you have seen was not the beginning of a story, but in
+ninety-nine cases out of a hundred it was the end of a story. The
+little shooting-star was in existence long before you saw him, whirling
+through space with millions of little companions. But he has left them
+all, and dropped to earth. He is a shooting-star no longer.
+
+If such a journey to the moon as the one described two chapters back
+were indeed possible, the voyage aloft would hardly be so easily and
+safely performed as is there taken for granted. Putting aside the
+thought of other difficulties, such as lack of conveyance and lack of
+air, there would be the danger of passing through a very considerable
+storm of missiles--a kind of “celestial cannonade”--which, to say the
+least, would prove very far from agreeable.
+
+These “starlets” and “meteor planets,” as they have been called, are
+not visible in a normal condition, because of their minuteness. But on
+entering our atmosphere they are rendered luminous, owing to the heat
+evolved by the sudden and violent compression of the air in front of
+the moving body. According to this view, shooting-stars, which simply
+dart across the heavens, may be regarded as coming within the limits of
+the atmosphere, and carried out of it again, by their immense velocity,
+passing on in space. Meteoric showers may result from an encounter with
+a group of these bodies, while aërolites are those which come so far
+within the sphere of the earth’s attraction as to fall to its surface.
+More than two thousand years ago the Greeks venerated a famous stone
+which fell from the heavens on the river Ægos.
+
+[Illustration: METEOR EMERGING FROM BEHIND A CLOUD (NOV. 23, 1877).]
+
+It will scarcely be believed what numbers of these shooting-stars or
+meteorites constantly fall to the earth. As she travels on her orbit,
+hurrying along at the rate of nineteen miles each second, she meets
+them by tens of thousands. They too, like the earth, are journeying
+round the great center of our family. But they are so tiny, and
+the earth by comparison is so immense, that her strong attraction
+overpowers one after another, drags it from its pathway, and draws it
+to herself.
+
+And then it falls, flashing like a bright star across the sky, and
+the little meteorite has come to his end. His myriads of companions,
+hastening still along their heavenly track--for the meteorites seem to
+travel commonly in vast flocks or companies--might, had they sense,
+mourn in vain for the lost members of their family.
+
+Any one taking the trouble to watch carefully some portion of the sky
+after dark, may expect to see each hour about four to eight of these
+shooting-stars--except in the months of August and November, when the
+number is much larger. About six in an hour does not sound a great
+deal. But that merely means that there have been six in one direction,
+and near enough for you to see. Somebody else, watching, may have
+seen six in another direction; and somebody else, a few miles away,
+may have seen six more. It is calculated that, in the course of every
+twenty-four hours, about four hundred millions of meteorites fall to
+earth, including those visible only through telescopes.
+
+This is rather startling. What if you or I should some day be struck
+by one of these solid, hard little bodies, darting as they do towards
+earth with speed swifter than that of a cannon-ball? True, they are not
+really stars, neither are they really planets. But they are, to say
+the least, often much larger than a cannon-ball, and a cannon-ball can
+destroy life.
+
+Four hundred millions every twenty-four hours! Does it not seem
+singular that we do not see them constantly dropping to the ground?
+The truth is, we _should_ see them, and feel them too, and dire would
+be the danger to human life, but for a certain protecting something
+folded round this earth of ours to ward off the peril. That “something”
+is the earth’s atmosphere. But for the thick, soft, strong, elastic
+air through which the meteorites have to pass, they would fall with
+fearful violence, often doing terrible mischief. As it is, we are
+guarded. The shooting-star, drawn by the earth’s attraction, drops into
+her atmosphere, darting with tremendous speed. In consequence of this
+speed and the resistance of the air, it catches fire. That is when we
+first see it. The meteorites are believed to appear at a height of
+about seventy miles, and to disappear at a height of about fifty miles.
+So that, in one instant’s flash, the shooting-star has traveled some
+twenty miles toward us. Then the light goes out. The little meteorite
+is burnt. It falls to earth still; but only as fine dust, sinking
+harmlessly downward.
+
+The meteorites do not always vanish so quickly. Now and then a larger
+one--too large to be rapidly burnt--does actually reach the ground. If
+any man were struck by such a stone he would undoubtedly be killed.
+
+When meteorites thus fall to earth they are usually called _aërolites_.
+Some are found no bigger than a man’s fist, while others much exceed
+this size. There is one, kept carefully in the British Museum, which
+weighs three tons and a half; and we hear of another, lying in South
+America, between seven and eight feet in length. Such a sky-visitant
+would be very unwelcome in any of our towns.
+
+We must remember that, whatever size an aërolite may be when it reaches
+the earth, it must have been far greater when journeying round the sun,
+since a good part of it has been burnt away during its rush downward
+through the earth’s atmosphere.
+
+Meteors, or bolides, or fireballs, are of much the same nature as
+meteorites; but they are larger, longer to be seen, and slower in
+movement. Also, it is not uncommon for them to burst with a loud
+explosion. Early in the present century such a meteor visited Normandy.
+It exploded with a noise like the roll of musketry, scattering
+thousands of hot stones over a distance of several miles. A great
+number of them were collected, still smoking. The largest of these
+stones weighed no less than twenty pounds. Happily no one seems to have
+been injured. Other such falls have taken place from time to time.
+Sometimes bright, slowly-moving meteors have been seen, looking as
+large as the moon.
+
+A remarkable fireball appeared in England on November 6, 1869. This
+fireball was extensively seen from different parts of the island, and
+by combining and comparing these observations, we obtain accurate
+information as to the height of the object and the velocity with which
+it traveled. It appears that this meteor commenced to be visible at
+a point ninety miles above Frome, in Somersetshire, and that it
+disappeared at a point twenty-seven miles over the sea, near St. Ives,
+in Cornwall. The whole length of its course was about 170 miles, which
+was performed in a period of five seconds, thus giving an average
+velocity of thirty-four miles a second. A remarkable feature in the
+appearance which this fireball presented was the long, persistent
+streak of luminous cloud, about fifty miles long and four miles wide,
+which remained in sight for fully fifty minutes. We have in this
+example an illustration of the chief features of the phenomena of a
+shooting-star presented on a very grand scale. It is, however, to be
+observed that the persistent luminous streak is not a universal, nor,
+indeed, a very common characteristic of a shooting-star.
+
+If we may liken comets to the _fishes_ of the Solar System--and in
+their number, their speed, their varying sizes, their diverse motions,
+they may be fairly so likened--we may perhaps speak of the meteorites
+as the _animalcula_ of the Solar System. For, in comparison with the
+planets, they are, in the matter of size, as the animalcula of our
+ponds in comparison with human beings. In point of numbers they are
+countless.
+
+Take a single drop of water from some long-stagnant pond, and place
+it under a powerful microscope. You will find it to be full of life,
+teeming with tiny animals, darting briskly to and fro. The drop of
+water is in itself a world of living creatures, though the naked eye
+of man could never discover their existence. So with the meteorites.
+There is good reason to believe that the Solar System fairly teems with
+them. We talk of “wide gaps of empty space,” between the planets; but
+how do we know that there is any such thing as empty space to be found
+throughout all the sun’s domain?
+
+Not only are the meteorites themselves countless, a matter easily
+realized, but the families or systems of meteorites appear to be
+countless also. They, like the systems of Jupiter and Saturn, are
+each a family within a family--a part of the Solar System, and yet a
+complete system by themselves. Each circles round the sun, and each
+consists of millions of tiny meteorites. When I say “tiny,” I mean it
+of course only by comparison with other heavenly bodies. Many among
+them may possibly be hundreds of feet and even more in diameter, but
+the greater proportion appear to be much smaller. It is not impossible
+that multitudes beyond imagination exist, so small in size that it is
+impossible we should ever see them, since their dying flash in the
+upper regions of our atmosphere would be too faint to reach our sight.
+
+The earth, traveling on her narrow orbit round the sun, crosses the
+track of about one hundred of these systems, or rings. Sometimes she
+merely touches the edge of a ring, and sometimes she goes into the very
+thick of a dense shower of meteorites. Twice every year, for instance,
+on the 10th of August and the 11th of November, the earth passes
+through such a ring, and very many falling stars may be seen on those
+nights. Numbers of little meteorites, dragged from their orbits and
+entangled in the earth’s atmosphere, like a fly caught in a spider’s
+web, give their dying flash, and vanish. It used to be supposed that
+the August and November meteorites belonged to one single system; but
+now they are believed to be two entirely distinct systems.
+
+[Illustration: THE GREAT SHOWER OF SHOOTING-STARS, NOVEMBER 27, 1872.]
+
+The comet discovered on February 27, 1827, by Biela, and ten days later
+at Marseilles by Gambart, who recognized that it was the same as that
+of 1772 and 1805, returned six and a half years later, in 1832. In
+fact it crossed, as we have seen, the plane of the terrestrial orbit
+at the respectable distance of fifty millions of miles from the earth;
+but if there was any danger in this meeting, it was rather for it
+than for us; for it was certainly strongly disturbed in its course.
+It returned in 1839, but under conditions too unfavorable to enable
+it to be observed--in the month of July, in the long days, and too
+near the sun. It was seen again in 1845, on November 25th, near the
+place assigned to it by calculation, and its course was duly followed.
+Everything went on to the general satisfaction, when--unexpected
+spectacle!--on January 13, 1846, _the comet split into two_! What had
+passed in its bosom? Why this separation? What was the cause of such a
+celestial cataclysm? We do not know; but the fact is, that instead of
+one comet, two were henceforth seen, which continued to move in space
+like two twin-sisters--two veritable comets, each having its nucleus,
+its head, its coma, and its tail, slowly separating from each other. On
+February 10th there was already a hundred and fifty thousand miles of
+space between the two. They would seem, however, to have parted with
+regret, and during several days a sort of bridge was seen thrown from
+one to the other. The cometary couple, departing from the earth, soon
+disappeared in the infinite night.
+
+They returned within view of the earth in the month of September, 1852.
+On the 26th of this month the twins reappeared, but much farther apart,
+separated by an interval of twelve hundred and fifty thousand miles.
+
+But this is not the strangest peculiarity which this curious body
+presented to the attention of astronomers. The catastrophe which was
+observed in 1846 was only a presage of the fate which awaited it; for
+now its existence is merely imagined, the truth being that _this comet
+is lost_. Since 1852 all attempts to find it again have been unavailing.
+
+To be lost is interesting, especially for a comet. But this, doubtless,
+was not enough; for it reserved for us a still more complete surprise.
+Its orbit intersects the terrestrial orbit at a point which the earth
+passes on November 27th. Well, nothing more was thought about it--it
+was given up as hopeless, when, on the evening of November 27, 1872,
+there fell from the sky a veritable _rain of shooting stars_. The
+expression is not exaggerated. They fell in great flakes. Lines of fire
+glided almost vertically in swarms and showers--here, with dazzling
+globes of light; there, with silent explosions, recalling to mind those
+of rockets; and this rain lasted from seven o’clock in the evening
+till one o’clock next morning, the maximum being attained about nine
+o’clock. At the observatory of the Roman College, 13,892 were counted;
+at Montcalieri, 33,400; in England a single observer counted 10,579,
+etc. The total number seen was estimated at _a hundred and sixty
+thousand_. They all came from the same point of the sky, situated near
+the beautiful star Gamma of Andromeda.
+
+On that evening I happened to be at Rome, in the quarter of the Villa
+Medicis, and was favored with a balcony looking towards the south. This
+wonderful rain of stars fell almost before my eyes, so to say, and I
+shall never cease regretting not having seen it. Convalescent from
+a fever caught in the Pontine Marshes, I was obliged to go into the
+house immediately after the setting of the sun, which on that evening
+appeared from the top of the Coliseum to sleep in a bed of purple
+and gold. My readers will understand what disappointment I felt next
+morning when, on going to the observatory, Father Secchi informed me
+of that event! How had he observed it himself? By the most fortunate
+chance: A friend of his, seeing the stars fall, went to him to ask
+an explanation of such a phenomenon. It was then half-past seven. The
+spectacle had commenced; but it was far from being finished, and the
+illustrious astronomer was enabled to view the marvelous shower of
+nearly _fourteen thousand_ meteors.
+
+This event made a considerable stir in Rome, and the pope himself did
+not remain indifferent; for, some days afterwards, having had the
+honor of being received at the Vatican, the first words that Pius IX
+addressed to me were these: “Have you seen the shower of Danaë?” I had
+admired, some days before in Rome, some admirable “Danaës,” painted by
+the great masters of the Italian school in a manner which left nothing
+to be desired; but I had not had the privilege of finding myself under
+the cupola of the sky during this new celestial shower, more beautiful
+even than that of Jupiter.
+
+What was this shower of stars? Evidently--and this is not doubtful--the
+encounter with the earth of myriads of small particles of matter moving
+in space along the orbit of Biela’s comet. The comet itself, if it
+still existed, would have passed twelve weeks before. It was not, then,
+to speak correctly, the comet itself which we encountered, but perhaps
+a fraction of its decomposed parts, which, since the breaking-up of the
+comet in 1846, would be dispersed along its orbit behind the head of
+the comet.[1]
+
+[1] No doubt can remain of the identity of this swarm of shooting-stars
+with the comet of Biela. On November 27, 1885, the same encounter
+occurred. A magnificent shower of stars was observed all over Europe
+just at the moment when the earth crossed the comet’s orbit.
+
+Once in every thirty-three years we have a grand display of meteorites
+in November; tens of thousands being visible in one single night. The
+meteorites in that ring have their “year” of thirty-three earthly
+years, and once in the course of that long year our earth’s orbit
+carries her deep into their midst. In this single November ring there
+are myriads upon myriads of meteorites, spreading through millions of
+miles of space.
+
+Yet this system is but one among many. There is no reason whatever
+to suppose that the streams of meteorites cluster more thickly about
+the orbit of the earth, than in other parts of the Solar System. No
+doubt the rest of the planets come across quite as many. Indeed,
+the wonderful rings of Saturn are probably formed entirely of
+meteorites--millions upon millions of them whirling round the planet
+in a regular orbit-belt, lit up by the rays of the sun. Also it is
+believed that the meteorite families cluster more and more closely in
+the near neighborhood of the sun, rushing wildly round him, and falling
+by millions into the ocean of flame upon his surface. It has even been
+guessed that they may serve in part as fuel to keep up his mighty
+furnace heat.
+
+There is a curious cone-shaped light seen sometimes in the west after
+sunset. It is called the “Zodiacal Light,” and men have often been much
+puzzled to account for it. The shining is soft and dim, only to be
+seen when the sky is clear, and only to be seen in the neighborhood of
+the sun. This, too, _may_ be caused by reflected light from countless
+myriads of meteorites gathering thickly round the sun.
+
+
+
+
+CHAPTER IX.
+
+NEIGHBORING FAMILIES.
+
+
+We have now to take flight in thought far, far beyond the outskirts of
+our little Solar System. Yes, our _great_ Solar System, with its mighty
+sun, its planets, its moons, its comets and meteorites, its ceaseless
+motions, its vast distances,--even all this sinks to littleness beside
+the wider reaches of space which now have to be pictured to our minds.
+For our sun, in all his greatness, is only a single star--only one star
+among other stars--and not by any means one of the largest of the stars.
+
+How many stars are there in the sky? Look overhead some cloudless
+night, and try to count the brilliant points of light. “Millions,” you
+would most likely give as your idea of their number. Yet you would be
+wrong; for you do not really perceive so many. The stars visible to
+man’s naked eye have been mapped and numbered. It is found that from
+two to three thousand are, as a rule, the utmost ever seen at once,
+even on a favorable night, and with particularly good sight.
+
+But what is actually the full number of the stars? Two or three
+thousand overhead. Five or six thousand round the whole world. So
+much visible to man’s unaided eyes. Ah, but take a telescope, and see
+through it the opening fields of stars beyond stars. Take a stronger
+telescope, and note how, as you pierce deeper into space, fresh stars
+beyond fresh stars shine faintly in the measureless distance. Take the
+most powerful telescope ever made, and again it will be the same story.
+
+There has been a chart or map drawn of known stars in the northern
+hemisphere--including those visible in telescopes down to a certain
+magnitude--containing over three hundred thousand. But that is only a
+part of even what man can see. Sir William Herschel calculated roughly
+that the number of stars within reach of his powerful telescope, round
+the whole earth, amounted probably to something like twenty millions.
+
+Twenty millions of suns! For that is what it really means. Twenty
+millions of radiant, burning, heavenly bodies--some the same size as
+our sun; some larger, perhaps very much larger; some smaller, perhaps
+very much smaller; but all SUNS. And any number of these suns may have,
+just like our own, families of planets traveling round them, enjoying
+their light and their heat.
+
+We talk about stars of the first, second, and other magnitudes. Stars
+can be seen without a telescope as low down as the sixth magnitude;
+after that they become invisible to the naked eye. This word
+“magnitude” is rather misleading. “Magnitude” means size, and whatever
+the real size of the stars may be, they have to our sight no seeming
+size at all. So when we speak of different _magnitudes_, we really mean
+different _brightnesses_. The brightest stars are those of the first
+magnitude, the next brightest those of the second magnitude, and so on.
+No doubt many a star of the third or fourth magnitude is really much
+larger than many a star of the first or second magnitude, only being
+farther away it shines more dimly, or the higher-magnitude star may in
+itself possess greater natural brilliancy.
+
+Of first-magnitude stars there are altogether about twenty; of
+second-magnitude stars about sixty-five; of third-magnitude stars about
+two hundred; and so the numbers increase till of the sixth-magnitude
+stars we find more than three thousand. These are all that can be
+commonly seen with the naked eye, amounting to five or six thousand.
+With telescopes the numbers rise rapidly to tens of thousands, hundreds
+of thousands, and even millions.
+
+For a long while it was found quite impossible to measure the distances
+of the stars. To this day the distances of not over two dozen, among
+all those tens of thousands, have been discovered. The difficulty of
+finding out the distance of the sun was as nothing compared with the
+difficulty of finding out the distances of the stars.
+
+No base-line sufficient for the purpose could for years be obtained.
+I must explain slightly what is meant by a “base-line.” Suppose you
+were on the brink of a wide river, which you had no means of crossing,
+though you wished to discover its breadth. Suppose there were on the
+opposite brink a small tree, standing alone. As you stood, you would
+see the tree seeming to lie against a certain part of the country
+beyond. Then, if you moved along your bank some fifty paces, the tree
+would seem to lie against quite a different part of the country beyond.
+
+Now if you had a long piece of string to lay down along the fifty paces
+you walked, and if two more pieces of string were tied, one from each
+_end_ of the fifty paces, both meeting at the tree, then the three
+pieces of string would make one large triangle, and the “fifty paces”
+would be the “base” of your triangle.
+
+If you could not cross the river, you could not of course tie strings
+to the tree. But having found your _base-line_, and measured its exact
+length, and having also found the shape of the two angles at its two
+ends, by noting the seeming change of the tree’s position, it would
+then be quite easy to find out the distance of the tree. The exact
+manner in which this calculation is made can hardly be understood
+without some slight knowledge of a science called trigonometry. The
+tree’s distance being found, the breadth of the river would be known.
+
+This mode of measuring distance was found comparatively easy in the
+case of the moon. But in the case of the sun there was more difficulty,
+on account of the sun’s greater distance. No base-line of ordinary
+length would make the sun seem to change his position in the sky in the
+slightest degree. Nor till the very longest base-line on the earth was
+tried could the difficulty be overcome. That base-line is no less than
+eight thousand miles long. One man standing in England looking at the
+sun, and another man standing in Australia looking at the sun, have
+such a base-line lying between them, straight through the center of the
+earth.
+
+In the case of the stars this plan was found useless. So closely has
+the sky been mapped out, and so exactly is the place of each star
+known, that the tiniest change would have been at once noticed. Not
+a star showed the smallest movement. The eight thousand miles of the
+earth’s diameter was a mere point with regard to them.
+
+A bright idea came up. Here was our earth traveling round the sun, in
+an orbit so wide that in the middle of summer she is over one hundred
+and eighty millions of miles away from where she is in the middle of
+winter. Would not that make a magnificent base-line? Why not observe
+a star in summer and observe the same star again in winter, and then
+calculate its distance.
+
+This, too, was done. For a long while in vain! The stars showed no
+signs of change, beyond those due to causes already known. Astronomers
+persevered, however, and with close and earnest care and improved
+instruments, success at last rewarded their efforts. A few--only a few,
+but still a few--of those distant suns have submitted to the little
+measuring-line of earth, and their distance has been roughly calculated.
+
+Now, what is their distance? Alpha Centauri, the second star which was
+attempted with success, is the nearest of all whose distance we know.
+You have heard how far the sun is from the earth. The distance of Alpha
+Centauri is _two hundred and seventy-five thousand times as much_. Can
+you picture to yourself that vast reach of space--a line ninety-three
+millions of miles long, repeated over and over again two hundred and
+seventy-five thousand times?
+
+But Alpha Centauri is one of the very nearest. The brilliant Sirius is
+at least twice as far away. Others utterly refuse to show the smallest
+change of position. It is with them, as had been said, much the same as
+if a man were to look at a church-steeple, twenty miles distant, out
+of one pane in a window, and then were to look at it out of the next
+pane. With the utmost attention he would find no change of position in
+the steeple. And like the base-line of two glass panes to that steeple,
+so is the base-line formed by our whole yearly journey to thousands
+of distant stars. We _might_ measure how far away they are, only the
+longest base-line within our reach is too short for our purpose.
+
+The planet Neptune has a wider orbit than ours. But even his orbit,
+seen from the greater number of the stars, would shrink to a single
+point. After all, how useless to talk of two hundred and seventy-five
+thousand times ninety-three millions of miles! What does it mean? We
+can not grasp the thought.
+
+Let us look at the matter from another view. Do you know how fast light
+travels--this bright light shining round us all day long? Light, so far
+as we know, does not exist everywhere. It travels to and fro, from the
+sun to his planets, from the planets to one another; from the sun to
+the moon, from the moon to the earth, and from the earth to the moon
+again.
+
+Light takes time to travel. This sounds singular, but it is true. Light
+can not pass from place to place in no time. Light, journeying through
+space, is invisible. Only when it strikes upon something, whether a
+solid body or water or air, does it become visible to our eyes. The
+shining all round us in the day-time is caused by the sunlight being
+reflected, not only from the ground, but from each separate particle
+of air. If we had no atmosphere, we should see still the bright rays
+falling on the ground, but the sky above would be black. Yet that black
+sky would be full of millions of light-rays, journeying hither and
+thither from sun and stars, invisible except where they alight upon
+something.
+
+The speed of light is far beyond that of an express train, far beyond
+that of the swiftest planet. In one tick of the clock, Mercury has
+rushed onward twenty-nine miles. In one tick of the clock, storm-flames
+upon the surface of the sun will sweep over two or three hundred miles.
+But in one tick of the clock a ray of light flashes through one hundred
+and eighty-six thousand three hundred and thirty-seven miles.
+
+One hundred and eighty-six thousand miles! That is the same as to say
+that, during one single instant, a ray of light can journey a distance
+equal to about eight times round and round our whole earth at the
+Equator.
+
+By using this wonderful light-speed as a measurement, we gain clearer
+ideas about the distances of the stars. A ray of light takes more
+than eight minutes to pass from the sun to the earth. Look at your
+watch, and note the exact time. See the hand moving slowly through the
+minutes, and imagine one single ray of light, which has left the sun
+when first you looked, flashing onward and onward through space, one
+hundred and eighty-six thousand miles each second. Eight minutes and a
+half are over. The ray falls upon your hand. In those few minutes it
+has journeyed ninety-three millions of miles.
+
+So much for the sun’s distance. How about the stars? Alpha Centauri,
+a bright star seen in the southern hemisphere, is one of our nearest
+neighbors. Yet each light-gleam which reaches the eye of man from that
+star, left Alpha Centauri four years and a third before. During four
+years and a third, from the moment when first it quitted the surface
+of the blazing sun, it has flashed ceaselessly onward, one hundred and
+eighty-six thousand miles each second, dwindling down with its bright
+companion-rays from a glare of brilliancy to a slender glimmer of light
+till it reaches the eye of man. Four years and a third sounds much,
+side by side with the eight minutes’ journey from the sun. Sound would
+take more than three millions of years to cross the same abyss. At
+the constant velocity of thirty-seven miles an hour, an express-train
+starting from the sun Alpha Centauri would not reach the earth until
+after an uninterrupted course of nearly seventy-five millions of years.
+
+This is our _neighbor_ star. The second, the nearest after it, is
+nearly double as far, and is found in quite another region of space, in
+the constellation of Cygnus, the Swan, always visible in our northern
+hemisphere. If we wish to understand the relative situation of our sun
+and the nearest two, let us take a celestial globe, and draw a plane
+through the center of the globe and through Alpha Centauri and 61
+Cygni. We shall thus have before us the relation which exists between
+our position in infinitude and those of these two suns. The angular
+distance which separates them on the celestial sphere is 125°. Let
+us make this drawing, and we shall discover certain rather curious
+particulars. In the first place, these two nearest stars are in the
+plane of the Milky Way, so that we can also represent the Milky Way on
+our drawing; again, this celestial river is divided into two branches,
+precisely in the positions occupied by these two nearest stars, the
+division remaining marked along the whole interval which separates
+them. This drawing shows us, further, that if we wish to trace the
+curve of the Milky Way with reference to the distance of our two stars,
+it will be nearer to us in the constellation of the Centaur than in
+that of the Swan; and, in fact, it is probable that the stars of that
+region of the sky are nearer than those of the opposite region. Another
+very curious fact is, that both the nearest stars are double.
+
+But look at Sirius, that beautiful star so familiar to us all. The
+light which reaches you to-night, left his surface from nine to ten
+years ago. Look at the Little Bear, with the Pole-star shining at the
+end of his tail. That ray of soft light quitted the Pole-star some
+forty years ago. Almost half a century it has been speeding onward and
+ever onward, with ceaseless rapidity, till its vast journey is so far
+accomplished that it has reached the earth. Look at Capella, another
+fair star of the first magnitude. The light which reaches you from her
+has taken over thirty years to perform its voyage. Ten, thirty, forty
+years--at the rate of 186,000 miles per second!
+
+These stars are among the few whose distance can be roughly measured.
+Others lie at incalculable distances beyond. There are stars whose
+light must, it is believed, have started hundreds or even thousands of
+years before the soft, faint ray at length reaches the astronomer’s
+upturned eye through the telescope.
+
+Look at Capella, how gently and steadily she shines! You see Capella,
+not as she is _now_, but as she _was_ thirty years ago. Capella may
+have ceased to exist meantime. The fires of that mighty sun may have
+gone out. If so, we shall by and by learn the fact--more than thirty
+years after it happened. Look at the Pole-star. Is there any Pole-star
+now? I can not tell you. I only know there _was_ one, forty years ago,
+when that ray of light started on its long journey. Stars have ceased
+to shine before now. What may have happened in those forty years, who
+can say? Look at that dim star, shining through a powerful telescope
+with faint and glimmering light. We are told that in all probability
+the tiny ray left its home long before the time of Adam.
+
+There is a strange solemnity in the thought. Hundreds of years
+ago--thousands of years ago--some say, even tens or hundreds of
+thousands of years ago! It carries us out of the little present into
+the unknown ages of a past eternity.
+
+If the neighboring stars are placed at tens and hundreds of trillions
+of miles from us, it is at quadrillions, at quintillions of miles
+that most of the stars lie which are visible in the sky in telescopic
+fields. What suns! what splendors! Their light comes from such
+distances! And it is these distant suns which human pride would like
+to make revolve round our atom; and it was for our eyes that ancient
+theology declared these lights, invisible without a telescope, were
+created! No contemplation expands the thought, elevates the mind, and
+spreads the wings of the soul like that of the sidereal immensities
+illuminated by the suns of infinitude. We are already learning that
+there is in the stellar world a diversity no less great than that
+which we noticed in the planetary world. As in our own Solar System
+the globes already studied range from 6 miles in diameter (satellites
+of Mars) up to 88,000 miles (Jupiter)--that is to say, in the
+proportion of 1 to 14,000--so in the sidereal system the suns present
+the most enormous differences of volume and brightness: 61 Cygni, the
+stars numbered 2,398 in the catalogue of Lalande, and 9,352 in the
+catalogue of Lacaille, and others of the eighth or ninth magnitude, are
+incomparably smaller or less luminous than Sirius, Arcturus, Capella,
+Canopus, Rigel, and the other brilliants of the firmament.
+
+
+
+
+CHAPTER X.
+
+OUR NEIGHBORS’ MOVEMENTS.
+
+
+How high! how distant! how mighty! How little we know about them, yet
+how overwhelming the little we know, and how wonderful that we do know
+it!
+
+We have now to consider the movements of these distant
+neighbors--first, their seeming movements; secondly, their real
+movements.
+
+I have already spoken about the seeming motions of the stars as a
+whole, once believed to be real, and now known to be only caused by the
+motions of our earth. For just as the turning of the earth upon her
+axis makes the sun seem to rise every morning in the east, and to set
+every evening in the west, so that same continued turning makes the
+stars seem to rise every evening in the east and to set every morning
+in the west.
+
+When we speak of the stars as rising in the east, we do not mean that
+they all rise at one point in the east, but that all rise, more or
+less, in an easterly direction--northeast, east, and southeast. So also
+with respect to the west. It is to the east and west of the earth as a
+whole that they rise and set--not merely to the east and west of that
+particular spot on earth where one man may be standing. All night long
+fresh stars are rising, and others are setting, and if it were not for
+the veil of light made by the sunshine in our atmosphere, we should see
+the same going on all day long as well.
+
+There are some constellations, or groups of stars, always visible at
+night in our northern hemisphere; and there are some constellations
+never visible to us, but only seen by people living in the southern
+hemisphere--in Australia, for instance. There are other constellations
+which appear in summer and disappear in winter, or which appear in
+winter and disappear in summer. This change is caused by our earth’s
+journey round the sun. It is not that the constellations have altered
+their place in the heavens with respect to the other constellations,
+it is merely that the earth has so altered its position in the heavens
+that the groups of stars which a short time ago were above the horizon
+with the sun by day are now above the horizon without him by night.
+
+Mention has been a good many times made of the axis of the earth ending
+in the North and South Poles. If this axis were carried straight onward
+through space, a long, slender pole passing upwards into the sky
+without any bend, from the North Pole in one direction and from the
+South Pole in the other,--this would be the pole of the heavens. The
+places of the stars in the sky are counted as “so many degrees” from
+the North and South Celestial Poles, just as the places of towns on
+earth are counted as “so many degrees” from the North and South Poles
+of earth. There are atlases of the sky made as well as atlases of the
+earth.
+
+The constellation of the Great Bear is known to all who have ever used
+their eyes at all to watch the heavens. Almost equally well known
+are the two bright stars in this constellation named the Pointers,
+because, taken together, they point in nearly a straight line to a
+certain important star in the end of the Little Bear’s tail, not very
+distant.
+
+This star, important less from its brightness than from its position,
+lies close to that very spot in the heavens where the celestial North
+Pole passes. It is called the Pole-star. Night after night, through
+the year, it there remains, all but motionless, never going below
+the horizon for us in the northern hemisphere, or northern half of
+the earth; never rising above the horizon for those in the southern
+hemisphere. It shines ever softly and steadily in its fixed position.
+If you travel further south, the Pole-star sinks downward towards the
+horizon. If you travel further north, the Pole-star rises higher above
+the horizon. If you were at the North Pole, you would see the Pole-star
+exactly overhead.
+
+[Illustration: CONSTELLATION OF THE GREAT BEAR.]
+
+Very near the Pole-star is the constellation of the Great Bear,
+with Cassiopeia nearly opposite on the other side of the Little
+Bear, and other groups between the two, completing the circle. These
+constellations do not, to us who live in the northern hemisphere,
+rise or set; for they simply move in a circle round and round the
+Pole-star, never going below the horizon. All day and all night long
+this circling movement continues, though only visible at night. It is
+caused entirely by the earth’s own motion on her axis.
+
+[Illustration: THE GREAT BEAR 50,000 YEARS AGO.]
+
+[Illustration: THE GREAT BEAR 50,000 YEARS HENCE.]
+
+Lower down, or rather further off from the Pole-star, comes another
+ring of constellations. These in just the same manner appear to
+travel round and round the Pole-star. But being further away, each
+dips in turn below the horizon--or, as we call it, each sets and
+rises again. And by the time we come to yet another circle of leading
+constellations, we reach those which are so far affected by the
+earth’s yearly journey as to be only visible through certain months,
+and to be hidden during other months.
+
+[Illustration: CONSTELLATION OF ORION, AS IT APPEARS NOW.]
+
+If we could stand exactly at the North Pole, during part of its six
+months’ night, we should see the Pole-star just overhead, and all the
+constellations circling round it once in every twenty-four hours. Those
+nearest would move slowly, in a small ring. Those furthest, and lowest
+down, would in the same length of time sweep round the whole horizon.
+But the stars would not there seem to rise or set. If we were standing
+at the South Pole, we should see exactly the same kind of seeming
+movement, only with altogether a different set of stars. If we were
+standing on the Equator at night, we should see the rising and setting
+very plainly. The whole mass of stars would appear to rise regularly
+and evenly in an easterly direction, to pass steadily across the sky,
+each taking its own straightforward path, and to set in a westerly
+direction.
+
+We who are placed midway between the Pole and the Equator, see a
+mixture of these two motions. Some stars seem to circle round and
+round, as all would do if we stood at the North Pole. Some stars seem
+to rise and set, as all would do if we stood at the Equator. So much
+for the seeming movements of the stars.
+
+But now, about their real movements. Are the stars fixed, or are they
+not? These seeming daily and yearly motions do not affect the question,
+being merely caused by our own motions. Trees and hedges may appear to
+move as we rush past them in a train, yet they are really fixed.
+
+[Illustration: CONSTELLATION OF ORION 50,000 YEARS FROM NOW.]
+
+During a long while, after it was found out that the quick, daily
+movements of all the stars in company were merely apparent, men
+believed that they really had no “proper motions”--that is, no
+movements of their own. For century after century the constellations
+remain the same. Hundreds of years ago the seven chief stars of the
+Great Bear shone in company as they shine now. Who could suppose that
+each one of those seven stars is hurrying on its path through space
+with a speed exceeding far that of the swiftest express-train? Yet so
+it is. Hundreds of years ago the grand group of Orion, with belt and
+sword, gleamed brilliantly night by night as it gleams in these days;
+and Cassiopeia had her W form, and Hercules and Draco and Andromeda
+were shaped as they are shaped still. Who would imagine that through
+those hundreds of years each star of these different constellations was
+hastening with more or less of speed along its heavenly road? Yet so it
+is.
+
+Cases have been decisively ascertained of stars changing their places
+among the other stars by a slow and gradual motion. Three of the most
+conspicuous of them--Sirius, Arcturus, and Aldebaran--have been proved,
+by the comparison of modern with some ancient observations, to have
+experienced a change of place to the southward, to the extent of more
+than the breadth of the moon in all the three. And during the period of
+accurate modern measurement, other instances have been ascertained of
+steady change of place by the effect of proper motion.
+
+But if the stars are thus rapidly moving in all directions, how is it
+that we do not _see_ them move? How is it that, night after night, year
+after year, century after century, even thousand years after thousand
+years, the shapes of the constellations remain unaltered?
+
+Suppose you and I were standing on the seashore together, watching
+the movements of scores of sea-craft, little boats and large boats,
+steamers, yachts, and ships. Suppose we stood through a full quarter
+of an hour looking on. Some might move, it is true, very slowly; yet
+their movements in every case would plainly be seen. There could be no
+possibility of mistaking the fact, or of supposing them to be “fixed.”
+Just so we see the nearer planets move. Little danger of our supposing
+them to be “fixed stars.”
+
+In the matter of the stars themselves, we must carry our illustration
+further. Come with me up to the top of that lofty hill on the border
+of the sea, and let us look from the cliff. We see still the movements
+among boats and smacks, yachts and steamers, only the increased
+distance makes the movements seem slower. But our view is widened. Look
+on the far horizon and see three distant dots, which we know to be
+ships--one and two close together, and a third a little way off, making
+a small constellation of vessels. Watch them steadily for a quarter of
+an hour. You will detect no movement, no increased distance or nearness
+between any two of the three. The group remains unchanged.
+
+Are they really moving? Of course they are, more or less rapidly,
+probably with differing speed and in different directions. But at
+so great a distance, one quarter of an hour is not long enough for
+their motions to become visible to the naked eye. If we could watch
+longer--say, for two or three hours--ah, that would make all the
+difference! If only we could watch longer! But the hundreds, and even
+thousands of years during which men have watched the stars, sink, at
+our vast distance, into no more than one quarter of an hour spent in
+watching the far-off ships from the high hilltop. The motions can not
+be detected. In ten thousand years you might see something. In fifty
+thousand years you might see much. But four or five thousand years are
+not sufficient.
+
+One other mode there is, by means of which the movements of the ships
+on the horizon might be made plain. Suppose you had no more than the
+quarter of an hour to spare, but suppose you had at your command a
+powerful telescope. Then you may practically bring the ships nearer,
+and by magnifying the small, slow, distant motions, you may make them,
+as it were, larger, quicker, more easy to see.
+
+Telescopes will do this for us, likewise, in the matter of the stars.
+By means of telescopes, with the assistance of careful watching and of
+close calculation it has been found that the stars are really moving
+quickly, each one in his own pathway. The very speed of some of them
+has been measured.
+
+Arcturus is one of those stars, the motions of which are most plainly
+to be seen. In the course of about one thousand years he changes
+visibly his place in the sky by a space equal to the apparent diameter
+of the moon. The seeming movement of Arcturus in one thousand years is
+the same as the seeming width of the round moon that we see.
+
+But the actual speed with which Arcturus rushes through space is said
+to be no less than fifty-four miles each second, or not far from two
+hundred thousand miles an hour. That is nearly three times as fast as
+our own earth’s motion round the sun. How enormous the distance must be
+which can shrink such speed to such seeming slowness!
+
+Another beautiful star, Capella, is believed to travel at the rate of
+thirty miles each second. The speed of Sirius is slower, being only
+fourteen miles a second. The Pole-star creeps along at the rate of only
+one mile and a half each second.
+
+So also with the rest of the stars. There seems good reason to believe
+that every star we see shining in the heavens, every star visible in
+powerful telescopes, is perpetually hastening onward. But hastening
+whither? God knows! We do not.
+
+In all probability not one of the tens of millions of stars which
+may be seen through telescopes is in repose. This is a matter of
+conjecture, of reasoning from analogy, and of reasoning also from
+the working of known laws. We _know_, as a consequence of direct
+observation, apart from the new spectroscopic method, that at least
+hundreds are upon the wing. We _assume_, as a matter of the greatest
+possible likelihood, that all the millions besides, which can not be
+actually seen to stir, are equally on the move. Knowing what we do know
+of the laws by which the universe of stars is governed, it seems to us
+an absolute impossibility that any single star, amid the whole vast
+host, can be or could be permanently at rest.
+
+If by any means a star were brought to repose--what then would happen?
+It would inevitably start off again, drawn by the attraction of other
+stars. From whatever direction the strongest pull came, the impulse
+would be given. Lengthened repose would be out of the question. And
+this, it seems to us, must be true, not of one star only, here or
+there, but of every star in the enormous host of radiant suns which
+make up the mighty Stellar System.
+
+Our forefathers, one thousand years ago, could not measure the precise
+positions of individual stars, as astronomers now are able to do.
+They had no modern observatories, no telescopes, no spectroscopes, no
+photographic appliances. These methods of observation we shall explain
+in another chapter. Their measurements at best were rough, their
+scientific knowledge was crude. Had we any such accurate observations
+handed down from one thousand years ago as are made in these days, we
+should no doubt see clearly many slight differences in the positions
+of many stars which are not now apparent. But even then we should see
+no changes sufficient in amount to affect the general outlines of the
+leading constellations.
+
+A star, which in the course of a century makes visible advance over a
+space in the sky equal to only a small portion of the breadth of the
+full moon, is looked upon as a fast voyager. One hundred times this
+degree of movement, if it took place in a considerable number of stars
+in our sky, would not in centuries very materially change the face of
+our midnight heavens.
+
+And all motions which would in the remotest degree affect the shapes of
+constellations, must be sideway motions. Those line-of-sight motions,
+of which the spectroscope alone tells us, could never have been
+discovered by simple observation of the sky. Until the new method came
+to light we had no means whatever of perceiving such movements among
+the stars.
+
+Suppose you are looking at two men in the distance, upon a wide, flat
+plain. One of the two is walking very slowly _across_ your line of
+vision. The second man is moving very slowly straight _towards_ you.
+If you watch with care you may find out both the movements. The sideway
+walking will be apparent first and most easily, because, as the man
+moves, he has constantly a fresh part of the horizon behind him. But
+in time the advance of the second man towards you will also become
+apparent; for although he is seen still against precisely the same spot
+on the horizon, he slowly occupies a larger spot on the retina of your
+eye,--in other words, he seems to grow bigger. And that, as you know
+from long experience, can only mean increasing nearness.
+
+If a star seemed to grow larger as it drew nearer, we should then be
+able to perceive that movement also. But no star in the sky ever does
+seem to grow any larger. Every star is to us but one point of light.
+It may be rushing towards us at an enormous rate of speed, yet still
+as a single point it remains, always at the same point in our sky.
+Therefore we have no chance of perceiving its movement; or rather, we
+_had_ no chance until the discovery of this new method. In fact, the
+very nearest known star is at so enormous a distance that, supposing it
+to be coming towards us at the rate of one hundred miles each second,
+it would still gain, in the course of a century, only one-fortieth part
+more of brightness than it has now. It would not increase at all in
+apparent size.
+
+When we leave behind us the thought of starry motions, as we faintly
+detect them at this great distance, and picture to ourselves the actual
+far-off whirl of all those glorious suns, the effect upon the mind is
+overwhelming. Stars are found to be rushing hither and thither, at
+every degree of speed, in every imaginable direction: stars to right,
+and stars to left; stars towards us, and stars away from us; stars
+alone, and stars in company,--all this, and more, deciphered out of
+the tiny gleam of quivering light, which streams through the vast
+abyss of space from each distant orb to earth. So real star-motions
+were known--first, through telescopic observation; secondly, through
+spectroscopic observation; and now, lastly, photography has stepped in,
+bringing with it much increase of exactitude.
+
+But if all the stars are moving, what of our sun? Our sun is a star.
+And our sun also is moving. He is pressing onward, in a wide sweep
+through space, bearing along with him his whole vast family--planets,
+satellites, comets, meteorites--round or towards some far distant
+center. For aught we know, every star in the heavens may have a like
+family traveling with him.
+
+In infinite space the stars are strewn in immense clusters, like
+archipelagoes of islands in the ocean of the heavens. To go from one
+star to another in the same archipelago light takes years; to pass
+from one archipelago to another it takes thousands of years. Each of
+these stars is a sun similar to ours, surrounded, doubtless, at least
+for the most part, by worlds gravitating in its light; each of these
+planets possesses, sooner or later, a natural history adapted to its
+constitution, and serves for many ages as the abode of a multitude of
+living beings of different species. Attempt to count the number of
+stars which people the universe, the number of living beings who are
+born and die in all these worlds, the pleasures and pains, the smiles
+and tears, the virtues and vices! Imagination, stop thy flight!
+
+The sun is not one of the most quickly-moving stars. His rate of speed
+has not been found out with any certainty, but it is believed to be
+about four or five miles a second.
+
+And where are we going? This has been in part discovered. If you and
+I were driving through a forest of trees, we should see the trees on
+each side of us seeming to move backward, while behind they would close
+together, and in front they would open out.
+
+Astronomers--and first among them, William Herschel--reasoned that
+if our Solar System were really in motion, we ought to be able to
+see these changes among the stars. And some such changes have become
+visible through careful watching--not so much those ahead and behind as
+those at the sides.
+
+It is not actually so simple a matter as looking at the trees in a
+forest, because the trees would be at rest, whereas each star has his
+own particular real motion, as well as his seeming change of place
+caused by our sun’s motion. It is more like moving in a small steamer
+at sea, among hundreds of other craft, each of which is going on its
+own way, at the same time that all on either side seem to move backward
+because we are moving forward.
+
+So each movement had to be noted, and the real motions had to be
+separated from the seeming backward drift of stars to the right and
+left of the sun’s pathway. The result of all this is that the sun,
+with his planets, is found to be hastening towards a certain far-off
+constellation named Hercules.
+
+It is a strange and unexpected fact, but absolutely true, that each sun
+of space is carried along with a velocity so rapid that a cannon-ball
+represents rest in comparison; it is at neither a hundred, nor three
+hundred, nor five hundred yards per second that the earth, the sun,
+Sirius, Vega, Arcturus, and all the systems of infinitude travel: it
+is at ten, twenty, thirty, a hundred thousand yards a second; all run,
+fly, fall, roll, rush through the void--and still, seen as a whole, all
+seems in repose.
+
+The immense distance which isolates us from all the stars reduces
+them to the state of motionless lights apparently fixed on the vault
+of the firmament. All human eyes, since humanity freed its wings
+from the animal chrysalis, all minds since minds have been, have
+contemplated these distant stars lost in the ethereal depths; our
+ancestors of Central Asia, the Chaldeans of Babylon, the Egyptians of
+the Pyramids, the Argonauts of the Golden Fleece, the Hebrews sung by
+Job, the Greeks sung by Homer, the Romans sung by Virgil,--all these
+earthly eyes, for so long dull and closed, have been fixed, from age
+to age, on these eyes of the sky, always open, animated, and living.
+Terrestrial generations, nations and their glories, thrones and altars
+have vanished: the sky of Homer is always there. Is it astonishing
+that the heavens were contemplated, loved, venerated, questioned, and
+admired, even before anything was known of their true beauties and
+their unfathomable grandeur?
+
+Better than the spectacle of the sea, calm or agitated, grander than
+the spectacle of mountains adorned with forests or crowned with
+perpetual snow, the spectacle of the sky attracts us, envelops us,
+speaks to us of the Infinite. “I have ascended into the heavens, which
+receive most of His light, and I have seen things which he who descends
+from on high knows not, neither can repeat,” wrote Dante in the first
+canto of his poem on “Paradise.” Let us, like him, rise towards the
+celestial heights, no longer on the trembling wings of faith, but
+on the stronger wings of science. What the stars would teach us is
+incomparably more beautiful, more marvelous, and more splendid than
+anything we can dream of.
+
+How do such contemplations enlarge and transfigure the vulgar idea
+which is generally entertained of the world! Should not the knowledge
+of these truths form the first basis of all instruction which aims
+at being serious? Is it not strange to see the immense majority of
+human beings living and dying without suspecting these grandeurs,
+without thinking of learning something of the magnificent reality which
+surrounds them?
+
+Where the sun and his planets will journey in future ages no living man
+can say. Indeed, though it is a question which does not lack interest
+to a thoughtful mind, yet there are numberless other questions about
+centuries near at hand which concern man far more nearly. The history
+of the Universe, and the history of this Earth of ours, must have
+advanced many broad stages before our sun and his attendant planets can
+have traveled so far that any change will be apparent in the shape of
+the star-constellations which spangle our sky.
+
+
+
+
+CHAPTER XI.
+
+MORE ABOUT THE SOLAR SYSTEM.
+
+
+We have now reached a point where it ought not to be difficult for
+us to picture to ourselves, with something of vividness, the general
+outlines of the Solar System. Awhile ago this Solar System was a very
+simple matter in the eyes of astronomers. There was the great sun
+fixed in the center, with seven planets circling round him--seven of
+course, it was said, since seven was the perfect number--and a few
+moons keeping pace with some of the planets, and an occasional comet,
+and a vast amount of black, empty space. But astronomers now begin to
+understand better the wonderful richness of the system as a whole; the
+immense variety of the bodies contained in it; the perpetual rush and
+stir and whirl of life in every part. Certainly there is no such thing
+as dull stagnation throughout the family.
+
+First, we have the great, blazing, central sun; not a sun at rest, as
+regards the stars, but practically at rest as regards his own system,
+of which he is always head and center. Then come the four smaller
+planets, rapidly whirling round him, all journeying in the same
+direction, and all having their oval pathways lying on nearly the same
+flat plane in space. Then the broad belt of busy little planetoids.
+Then the four giant planets,--Jupiter nearly five times as far as our
+earth from the sun; Saturn nearly twice as far as Jupiter; Uranus
+nearly twice as far as Saturn; Neptune as far from Uranus as Uranus
+from Saturn,--all keeping on very nearly the same level as the four
+inner planets.
+
+[Illustration: POSITION OF PLANETS INFERIOR TO JUPITER--SHOWING THE
+ZONE OF THE ASTEROIDS.]
+
+And between and about these principal members of the system, with their
+accompanying moons, we have thousands of comets flashing hither and
+thither, with long, radiant trains; and myriads of meteorites, gathered
+often into dense, vast herds or families, but also scattered thickly
+throughout every part of the system, each tiny ball reflecting the
+sun’s rays with its little glimmer of light.
+
+Broad reaches of black and empty space! Where are they? Perhaps
+nowhere. We are very apt, in our ignorance, to imagine that where we
+see nothing, there must of necessity be nothing. But, for aught we
+know, the whole Solar System, not to speak of sky-depths lying beyond,
+may be bright with reflecting bodies great and small, from the mighty
+Jupiter down to the fine diamond-dust of countless meteorites. In this
+earth of ours we find no emptiness. Closer and closer examination with
+the microscope only shows tinier and yet tinier wonders of form and
+life, each perfect in finish. Not of form only, but of _life_. How
+about that matter as regards the Solar System? Is our little world
+the one only spot in God’s great universe which teems with life? Are
+all other worlds mere barren, empty wastes? Surely not. We may safely
+conclude that life of one kind or another has been, is, or will be,
+upon our brother and sister worlds.
+
+The same reasoning may be used for the distant stars--those millions
+of suns lying beyond reach of man’s unassisted eyes. Are they formed
+in vain? Do their beams pour uselessly into space, carrying light,
+warmth, and life-giving power to nothing? Surely around many of them,
+as around our sun, must journey worlds; and not only worlds, but worlds
+containing life.
+
+We shall have to speak of this matter again as we go on. Whether men
+and women like ourselves could live on the other planets is another
+question. In some cases it looks doubtful, in some it would seem to
+be impossible. But the endless variety of life on this earth--life
+on land, life in the air, life in water, life underground, life in
+tropical heat, life in arctic cold--forbids us in anywise to be
+positive as to what may or may not be.
+
+If no animals that we know could exist there, animals that we do not
+know might be found instead. Any one of the planets may, and very
+likely does, abound with life. Nay, the very meteorites themselves,
+before they catch fire and burn in our air, _may_ be the homes of tiny
+animalcula, altogether different from anything we see on earth. We can
+not fancy life without air, but neither could we fancy life in water,
+if we had not seen and known it to be possible.
+
+I have spoken of the probable _brightness_ of the Solar System as a
+whole. We are so apt to think of things merely as we see them with our
+short sight, that it is well sometimes to try to realize them as they
+actually are. Picture to yourself the great central sun pouring out in
+every direction his burning rays of light. A goodly abundance of them
+fall on our earth, yet the whole amount of light and heat received over
+the whole surface of this world is only the two-thousand-millionth
+part of the enormous amount which he lavishly pours into space. How
+much of that whole is wasted? None, though God gives his gifts with a
+kingly profusion which knows no bounds. Each ray has its own work to
+do. Millions of rays are needed for the lighting and nourishing and
+warming of our companion-planets, while others are caught up by passing
+comets, and myriads flash upon swift, tiny meteorites. Of the rays not
+so used, many pass onwards into the vast depths beyond our system, and
+dwindle down into dim, starlike shining till they reach the far-off
+brother-stars of our sun.
+
+Have they work to do there? We can not tell. We do not know how far the
+sun’s influence reaches. As head and center, he reigns only in his own
+system. As a star among stars, a peer among his equals, he may, for
+aught we can tell, have other work to do.
+
+In an early chapter, mention was made of the earth’s three motions, two
+only being explained. First, she spins ceaselessly upon her axis. So
+does the sun, and so do the planets. Secondly, she travels ceaselessly
+round and round the sun in her fixed orbit. So does each one of the
+planets. Thirdly, she journeys ceaselessly onward through space with
+the sun. So also do the rest of the planets. These last two movements,
+thought of together, make the earth’s pathway rather perplexing at
+first sight. We talk of her orbit being an ellipse or oval; but how can
+it be an ellipse, if she is always advancing in one direction?
+
+The truth is, the earth’s orbit is and is not an ellipse. As regards
+her yearly journey round the sun, roughly speaking, we may call it
+an ellipse. As regards her movement in space, it certainly is not an
+ellipse.
+
+Think of the Solar System, with the orbits of all the planets, as lying
+_nearly flat_--in the manner that hoops might be laid upon a table,
+one within another. The asteroids, comets, and meteorites do not keep
+to the same level; but their light weight makes the matter of small
+importance.
+
+Having imagined the sun thus in the center of a large table--a small
+ball, with several tiny balls traveling round him on the table at
+different distances--suppose the sun to rise slowly upwards, not
+directly up, but in a sharp slant, the whole body of planets continuing
+to travel round, and at the same time rising steadily with him.
+
+By carefully considering this double movement, you will see that the
+real motion of the earth--as also of each of the planets--is not a
+going round on a flat surface to the same point from which she started,
+but is a corkscrew-like winding round and round upwards through space.
+Yet as regards the central sun, the shape of the orbit comes very near
+being an ellipse, if calculated simply by the earth’s distance from him
+at each point in turn of her pathway through the year.
+
+An illustration may help to explain this. On the deck of a moving
+vessel, you see a little boy walking steadily round and round the mast.
+Now is that child moving in a circle, or is he not? Yes, he is. No, he
+is not. He walks in a circle as regards the position of the mast, which
+remains always the center of his pathway. But his movement _in space_
+is never a circle, since he constantly advances, and does not once
+return to his starting-point. You see how the two facts are possible
+side by side. Being carried forward by the ship, with no effort of his
+own, the forward motion does not interfere with the circling motion.
+Each is performed independently of the other.
+
+It is the same with the earth and the planets. The sun, by force of
+his mighty attraction, bears them along wherever he goes--no exertion
+on their part, so to speak, being needed. That motion does not in the
+least interfere with their steady circling round the sun.
+
+Just as--to use another illustration--the earth, turning on her axis,
+bears through space a man standing on the Equator at the rate of one
+thousand miles an hour. But this uniform movement, unfelt by himself,
+does not prevent his walking backwards, or forwards, or in circles, as
+much as he will.
+
+So, also, a bird in the air is unconsciously borne along with the
+atmosphere, yet his freedom to wheel in circles for any length of time
+is untouched.
+
+A few words about the orbits of the planets. I have more than once
+remarked that these pathways are, in shape, not circles, but ellipses.
+A circle is a line drawn in the shape of a ring, every part of which
+is at exactly the same distance from the center-point or focus. But an
+ellipse, instead of being, like a circle, perfectly round, is oval in
+shape; and instead of having only one focus, it has two foci, neither
+being exactly in the center. Foci is the plural word for focus. If
+an ellipse is only slightly oval--or slightly _elliptical_--the two
+foci are near together. The more oval or _eccentric_ the ellipse, the
+farther apart are the two foci.
+
+You may draw a circle in this manner. Lay a sheet of white paper on a
+board, and fix a nail through the paper into the board. Then pass a
+loop of thread--say an inch or an inch and a half in length--round the
+nail, and also round a pencil, which you hold. Trace a line with the
+pencil, keeping the loop tight, so that the distance of your line from
+the nail will be always equal, and when it joins you have a circle. The
+nail in the center is the focus of the circle.
+
+To draw an ellipse, you must fix _two_ nails. Let them be about half an
+inch apart; pass a loop over both of them, and again placing a pencil
+point within the loop, again trace a line carefully all round, keeping
+the thread drawn tight. This time an oval instead of a circle will
+appear. By putting the nails nearer together or farther apart, you may
+vary as you will the shape of the ellipse.
+
+In the orbits of the earth and the planets, all of which are ellipses
+in shape, the sun is not placed in the exact center, but in one of
+the two foci, the second being empty. So at one time of the year the
+planet is nearer to the sun than at another time. Our earth is no
+less than three millions of miles nearer in winter than she is in
+summer--speaking of the winter and summer of the northern hemisphere.
+Three millions of miles is so tiny a piece out of ninety-three millions
+of miles, that it makes little or no difference in our feelings of heat
+or cold.
+
+The orbits of the comets are ellipses also, but ellipses often so
+enormously lengthened out, that the two foci are almost--if one may so
+speak--at the two _ends_ of the oval. To draw a good comet orbit, you
+must fix the two nails on your paper some five or six inches apart,
+with a loop of thread just large enough to slip over them both, and to
+allow the pencil to pass round them. When your ellipse is drawn, you
+must picture the sun in the place of one of the two nails, and you will
+see how, in their pathways, the comets at one time pass very near the
+sun, and at another time travel very far away from him.
+
+[Illustration: COMPARATIVE SIZE OF THE PLANETARY WORLDS.]
+
+It is generally found in families, not only that the parent or head
+of the family has great influence over all the members, but that each
+member has influence over each other member. Brother influences
+brother, and sister influences sister.
+
+This, too, we find in the Solar System. Not only does the sun, by his
+powerful attraction, bind the whole family together, but each member
+of the family attracts each other member. True, the force of the sun’s
+attraction is overpowering in amount compared with others. The sun
+attracts the planets, and the planets attract the sun; but their feeble
+pulling is quite lost in the display of his tremendous strength.
+
+Among themselves we see the power more plainly. The earth attracts the
+moon, keeping her in constant close attendance; and the moon attracts
+the earth, causing a slight movement on her part, and also causing the
+tides of the sea. Each planet has more or less power to hinder or help
+forward his nearest brother-planet. For instance, when Jupiter on his
+orbit draws near the slower Saturn on his orbit, Saturn’s attraction
+pulls him on, and makes him move faster than usual; but as soon as he
+gets ahead of Saturn then the same attraction pulls him back, and makes
+him go more slowly than usual. Jupiter has the same influence over
+Saturn; and so also have Saturn and Uranus over one another, or Uranus
+and Neptune.
+
+In early days astronomers were often greatly puzzled by these quickened
+and slackened movements, which could not be explained. Now the
+“perturbations” of the planets, as they are called, are understood and
+allowed for in all calculations. Indeed, it is by means of this very
+attraction that Neptune was discovered, and the planets have actually
+been weighed. What a wonderful difference we find in this picture of
+the Solar System, as we now know it to be, from the old-world notion of
+our earth as the center of the universe!
+
+When we think of all the planets, and of the magnificent sun; when we
+pass onward in imagination through space, and find our sun himself
+merely one twinkling star amid the myriads of twinkling stars scattered
+broadcast through the heavens, while planets and comets have sunk to
+nothing in the far distance,--then indeed we begin to realize the
+unutterable might of God’s power! Why, our earth and all that it
+contains may be regarded as but one grain of dust in the wide universe.
+
+
+
+
+CHAPTER XII.
+
+MORE ABOUT THE SUN.
+
+
+Not among the least of the wondrous things of creation are the
+tremendous disturbances taking place upon the surface of the sun--that
+raging, roaring sea of flame.
+
+A good many explanations have been from time to time offered as to the
+dark spots seen to move across the face of the sun. Some one or more of
+these explanations may be true; but we know little about the matter.
+A sun-spot does not commonly consist of merely one black patch. There
+is the dark center, called the _umbra_--plural, _umbræ_. There is the
+grayish part surrounding the umbra, called the _penumbra_. Also, in
+the center of the umbra there is sometimes observable an intensely
+black spot, called the _nucleus_. Sometimes a spot is made up of
+nucleus and umbra alone, without any penumbra. Sometimes it is made
+of penumbra alone, without any umbra. Sometimes in one spot there are
+several umbræ, with the gray penumbra round the whole, and gray bridges
+dividing the umbræ.
+
+The enormous size of these spots has been already described in an
+earlier chapter. Fifty thousand to one hundred thousand miles across
+is nothing unusual. In the year 1839 a spot was seen which measured no
+less than one hundred and eighty-six thousand miles in diameter.
+
+One explanation proposed was, that the sun might be a cool body,
+covered over with different envelopes or dense layers of cloudy form,
+one above another. The inside envelope--or, as some say, the inside
+atmosphere--would then be thick and dull-colored, protecting the solid
+globe within and reflecting light, but having none of its own. The next
+envelope would be one mass of raging, burning gases--the _photosphere_,
+in fact. The outer envelope would be a transparent, surrounding
+atmosphere, lighted up by the sea of fire within. A sun-spot would then
+consist of the tearing open of one or more of these envelopes, so as to
+give glimpses of the gray, inner atmosphere, or even of the dark, cool
+globe at the center.
+
+There may be some truth in this explanation; but the notion of a
+cool and dark body within is now pretty well given up. The apparent
+blackness of a spot-nucleus does not prove actual blackness or absence
+of heat. A piece of white-hot iron, held up against the sun, looks
+black; and it may be merely the contrast of the glowing photosphere
+which makes the nucleus seem so dark. It is even believed that the
+blackest parts may be the most intensely hot of all.
+
+Another proposed explanation was of dark clouds floating in the sun’s
+atmosphere. There, again, are found difficulties, particularly in
+the fact that, as the spots move across the sun, the changes which
+regularly take place in their appearance make it pretty clear that
+their shape is not flat, but hollow and cave-like. The changes here
+spoken of are seeming changes of shape, caused by change of position.
+There are also real changes constantly taking place. Although the spots
+often keep their general outlines long enough to be watched across the
+face of the sun, and even to be known again after spending nearly a
+fortnight hidden on the other side, still they are far from being fixed
+in form.
+
+[Illustration: A TYPICAL SUN-SPOT.]
+
+The alterations are at times not only very great, but very rapid.
+Sometimes in a single hour of watching, an astronomer can see marked
+movement going on--as you or I might in an hour observe movements
+slowly taking place in a high layer of clouds. For movement to show at
+all in one hour, at so immense a distance, proves that the actual rate
+of motion must be very great.
+
+The first great fact which was got from the study of these spots was
+this, that this great sun is very much like our own earth, in so far
+as it rotates on an axis in exactly the same way that our earth does.
+Not only do the spots change their position on the face of the sun, in
+consequence of the sun’s rotation on its axis, but they change very
+much from day to day, and even from hour to hour; so that we have
+evidence not only that the sun is rotating like our earth, but that the
+atmosphere of the sun is subjected to most tremendous storms--storms
+so tremendous, in fact, that the fiercest cyclones on our own earth
+are not for one moment to be compared with them. The fact that the
+spots do really move with the sun, and are really indentations,
+saucer-like hollows, in the photosphere, is shown by the appearance,
+which is always presented by a spot when it is near the edge of the
+sun. You know if you take a dinner-plate, and look it full in the face,
+it is round; but if you look at it edgeways, it is not round. Take
+two different views of the same spot: In one, you look the sun-spot
+straight in the face, and you see into it and can learn all about it;
+but in the other, when it has nearly gone round the corner, and is
+disappearing on the sun’s edge, you see it in the same way that you
+would see a plate looked at edgeways.
+
+These sun-cyclones must indeed be of terrific force and extent,
+compared with anything we see on earth. It was calculated that the
+speed of movement perceived in one spot was about three hundred and
+sixty-three miles each second.
+
+And still all this is nothing, or almost nothing, in comparison with
+the real power of the sun! The liquid state of the ocean; the gaseous
+state of the atmosphere; the currents of the sea; the raising of the
+clouds, the rains, storms, streams, rivers; the calorific value of
+all the forests of the globe and all the coal-mines of the earth; the
+motion of all living beings; the heat of all humanity; the stored-up
+power in all human muscles, in all the manufactories, in all the
+guns,--all that is almost nothing compared with that of which the
+sun is capable. Do we think that we have measured the solar power
+by enumerating the effects which it produces on the earth? Error!
+profound, tremendous, foolish error! This would be to believe still
+that this star has been created on purpose to illuminate terrestrial
+humanity. In reality, what an infinitesimal fraction of the sun’s total
+radiation the earth receives and utilizes! In order to appreciate
+it, let us consider the distance of ninety-three millions of miles
+which separates us from the central star, and at this distance let us
+see what effect our little globe produces, what heat it intercepts.
+Let us imagine an immense sphere _traced at this distance from the
+sun_, and entirely surrounding it. Well, on this gigantic sphere,
+the spot intercepted by our little earth is only equivalent to the
+fraction 1/2,138,000,000; that is to say, that the dazzling solar
+hearth radiates all round it through immensity a quantity of light
+and heat two thousand one hundred and thirty-eight million times more
+than that which we receive, and of which we have just now estimated
+the stupendous effects. The earth only stops in its passage the _two
+thousand millionth part of the total radiation_.
+
+Sometimes the storms or outbursts come in the shape of a bright spot
+instead of a dark one.
+
+[Illustration: A SOLAR ERUPTION.]
+
+Two astronomers were one day watching the sun from two different
+observatories, when they saw such an event take place. An intense
+and dazzling spot of light burst out upon the surface of the sun--so
+intense, so dazzling, as to stand quite apart from the radiant
+photosphere. To one astronomer it looked like a single spot, while the
+other saw two spots close together. In about a minute the light grew
+more dim, and in five minutes all was over. But in those five minutes
+the spot or spots had traveled a distance of thirty-five thousand
+miles.
+
+It was a very remarkable thing that the _magnets_ on earth--those
+delicate little needles which point so steadily yet perseveringly
+towards the North Pole--seemed to be strongly agitated by the distant
+solar outburst. This brings us to another interesting fact.
+
+The spots on the sun are not always the same in number. Sometimes they
+are many, sometimes they are few. Long and close watching has made it
+clear that they pass through a regular _order_ of changes: some years
+of many spots being followed by other years of less and less spots;
+then some years of very few spots being followed by other years of more
+and more spots,--decrease and increase being seemingly regular and
+alternate.
+
+This turn or _cycle_ of changes--from more to less, and then from less
+to more again--is found to run its course about once in every eleven
+years, with some variations.
+
+Now, it has long been known that the magnetic-needle goes through
+curious variations. Though we speak of it as pointing always north,
+yet it does not always so point exactly. Every day the needle is found
+to make certain tiny, delicate motions, as if faintly struggling to
+follow the daily movements of the sun--just a little towards the east,
+or just a little towards the west. These tiny motions, having been
+long watched and measured, were found to go through a regular course
+of changes--some years more, and some years less, waxing and waning by
+turns. It was discovered that the course of changes from more to less,
+and from less to more again, took place in about eleven years.
+
+These two things, you see, were quite independent of one another.
+Those who watched the sun-spots were not thinking of the magnets, and
+those who watched the magnets were not thinking of the sun-spots. But
+somebody did at last happen to think of both together. He was laughed
+at, yet he took the trouble carefully to compare the two. And, strange
+to say, he found that these two periods in the main agreed--the eleven
+years of alternate changes in the number of sun-spots, and the eleven
+years of alternate changes in the movements of the magnetic-needle.
+When the spots are most, the needle moves most. When the spots are
+least, the needle moves least. So much we know. But to explain the why
+and the wherefore is beyond our power.
+
+This study of the magnetism of our wandering planet is very
+interesting, and one which is still very little known. Here is a weak
+needle, a slip of magnetic iron, which, with its restless and agitated
+finger, incessantly seeks a region near the north. Carry this needle
+in a balloon up to the higher aerial regions, where human life begins
+to be extinguished; shut it up in a tomb closely separated from the
+light of day; take it down into the pit of a mine, to more than a
+thousand yards in depth,--and incessantly, day and night, without
+fatigue and without rest, it watches, trembles, throbs, seeks the
+point which attracts it across the sky, through the earth, and through
+the night. Now--and here is a coincidence truly filled with notes of
+interrogation--the years when the oscillation of this innocent little
+steel wire is strongest are the years when there are more spots, more
+eruptions, more tempests in the sun; and the years when its daily
+fluctuations are weakest are those when we see in the day-star neither
+spots, eruptions, nor storms. Does there exist, then, a magnetic bond
+between the immense solar globe and our wandering abode? Is the sun
+magnetic? But the magnetic currents disappear at the temperature of
+red-hot iron, and the incandescent focus of light is at a temperature
+incomparably higher still. Is it an electrical influx which is
+transmitted from the sun to the earth across a space of ninety-three
+millions of miles? On September 1, 1859, two astronomers--Carrington
+and Hodgson--were observing the sun, independently of each other;
+the first on a screen which received the image; the second directly
+through a telescope,--when, in a moment, a dazzling flash blazed
+out in the midst of a group of spots. This light sparkled for five
+minutes above the spots without modifying their form, as if it were
+completely independent, and yet it must have been the effect of a
+terrible conflagration occurring in the solar atmosphere. Each observer
+ascertained the fact separately, and was for an instant dazzled. Now,
+here is a surprising coincidence: at the very moment when the sun
+appeared inflamed in this region the magnetic instruments of the Kew
+Observatory, near London, where they were observing, manifested a
+strange agitation; the magnetic needle jumped for more than an hour
+as if infatuated. Moreover, a part of the world was on that day and
+the following one enveloped in the fires of an aurora borealis, in
+Europe as well as in America. It was seen almost everywhere,--at Rome,
+at Calcutta, in Cuba, in Australia, and in South America. Violent
+magnetic perturbations were manifested, and at several points the
+telegraph-lines ceased to act. Why should these two curious events not
+be associated with each other? A similar coincidence was observed on
+August 3, 1872, by Professor Charles A. Young, of Princeton, N. J.: a
+paroxysm in the solar chromosphere, magnetic disturbances everywhere.
+
+There is a very singular appearance seen upon the sun which must not
+be passed over without mention. Some astronomers speak of the whole
+surface as being _mottled_ all over with a curious rough look when
+examined through a powerful telescope. This “mottling” is described by
+various observers in various ways. One speaks of “luminous spots shaped
+like rice-grains.” Another, of “luminous spots resembling strokes
+made with a camel’s-hair pencil.” Another, of “luminous objects or
+granules.” Others, of “multitudes of leaves,” “nodules,” “crystalline
+shapes,” “leaves or scales, crossing one another in all directions,
+like what are called spills in the game of spillikens.” They have also
+been pictured as “certain luminous objects of an exceedingly definite
+shape and general uniformity of size, whose form is that of the oblong
+leaves of a willow-tree.” These cover the whole disk of the sun,
+excepting the space occupied by the spots, in countless millions, and
+lie crossing each other in every imaginable direction.
+
+In size they are said to be about one thousand miles long, by two
+or three hundred broad, but they vary a good deal. Where there is a
+spot, the willow-leaves at its edge are said to point pretty regularly
+towards the center. Whether they are, as they seem to be, solid in
+form; whether they are, as some suppose, the chief source of the
+sun’s light and heat; whether they lie on his surface or float in
+his atmosphere; what is their real nature, and what is their real
+use,--about these questions we are at present quite in the dark.
+
+We have next to think a little more about the edge or limb of the sun,
+and the stormy flames and outburst there seen. Until quite lately
+the only time for observing such appearances was during a total
+eclipse of the sun. Lately, by means of the new instrument called the
+“spectroscope,” it has been found possible to take observations when no
+eclipse is going on.
+
+[Illustration: SUN-FLAMES, MAY 3, 1892.]
+
+A few words of explanation as to eclipses of the sun seem needful,
+before going further. An eclipse of the sun is caused simply by the
+round body of the moon passing exactly between the sun and the earth,
+so as to hide the sun from us.
+
+Let there be a candle on the table, while you stand near. The rays of
+light from the candle fall upon your face. Now move slowly, to and
+fro, a round ball between you and the candle. So long as it is not
+precisely in the line between--so long as it is a little higher, or
+a little lower, or a little to one side--then you can still see the
+flame. Once you let the ball come just between the light and your
+eyes, and you see it no more. In other words the candle-flame is
+eclipsed--hidden, veiled, cut off--by the ball.
+
+It may seem curious at first sight that the moon, which is very small
+compared with the sun, should have power to cover the sun. But remember
+the difference of the distance. The sun is very far, and the moon
+is very near. Any small object very near will easily hide from your
+sight a large object at a considerable distance. You may hold up a
+shilling-piece at arm’s length, and make it cover from sight a man, or
+even a house, if the latter be far enough away. The sun at a distance
+of ninety-three millions of miles, and the moon at a distance of two
+hundred and forty thousand miles, have to our vision the same seeming
+size. So, when the moon glides between, her round face just about
+covers the sun’s round face.
+
+If the moon were traveling exactly in the same plane as the plane of
+the earth’s orbit, an eclipse would be a very common affair indeed. But
+the plane of the moon’s orbit being not quite the same as the plane of
+the earth’s orbit, she passes sometimes a little above, and sometimes a
+little below, the exact spot where she would hide the sun’s rays from
+us. Now and then, at certain intervals, she goes just between. And so
+well is the moon’s path in the heavens understood that astronomers can
+tell us, long years beforehand, the day and the hour an eclipse will
+take place.
+
+An eclipse of the sun is sometimes partial, sometimes total, sometimes
+annular. In a partial eclipse, the moon does indeed pass between, but
+only so as to hide from us _part_ of the sun. She is a little too
+low, or a little too high, to cover his face. In a total eclipse, the
+moon covers the sun completely, so that for a few minutes the bright
+photosphere seems blotted out from the heavens, a black round body,
+surrounded by light, taking its place. In an annular eclipse, the moon
+in like manner crosses the sun, but does not succeed in covering him
+entirely, a rim of bright photosphere showing round the black moon. For
+in an annular eclipse, the moon, being a little farther away from the
+earth than at the time of a total eclipse, has too small a disk quite
+to hide the sun’s disk.
+
+The blackness of the moon during an eclipse is caused by the fact that
+her bright side is turned towards the sun, and her dark side toward us.
+An eclipse of the sun can take place only at new moon, never at full
+moon. At her full, the moon is outside the earth’s orbit, away from the
+sun, and can not by any possibility pass between.
+
+Eclipses, like comets, have always been interpreted as the indication
+of inevitable calamities. Human vanity sees the finger of God making
+signs to us on the least pretext, as if we were the end and aim of
+universal creation. Let us mention, for example, what passed even in
+France, with reference to the announcement of an eclipse of the sun, on
+August 21, 1560. For one, it presaged a great overthrow of States and
+the ruin of Rome; for another, it implied another universal deluge;
+for a third, nothing less would result than a conflagration of the
+globe; finally, for the less excited, it would infect the air. The
+belief in these terrible effects was so general that, by the express
+order of the doctors, a multitude of frightened people shut themselves
+up in very close cellars, well heated and perfumed, in order to shelter
+themselves from these evil influences. Petit relates that the decisive
+moment approached, that the consternation was at its height, and that
+a parish priest of the country, being no longer able to confess his
+parishioners, who believed their last hour had come, was obliged to
+tell them in a sermon “not to be so much hurried, seeing that, on
+account of the wealth of the penitents, the eclipse had been postponed
+for a fortnight.” These good parishioners found no more difficulty in
+believing in the postponement of the eclipse than they had in believing
+in its unlucky influence.
+
+History relates a crowd of memorable acts on which eclipses have
+had the greatest influence. Alexander, before the battle of Arbela,
+expected to see his army routed by the appearance of a phenomenon of
+this kind. The death of the Athenian general Nicias and the ruin of
+his army in Sicily, with which the decline of the Athenians commenced,
+had for their cause an eclipse of the moon. We know how Christopher
+Columbus, with his little army, threatened with death by famine at
+Jamaica, found means of procuring provisions from the natives by
+depriving them in the evening of the light of the moon. The eclipse
+had scarcely commenced when they supplied him with food. This was the
+eclipse of March 1, 1504. We need not relate other facts of this
+nature, in which history abounds, and which are known to every one.
+
+Eclipses no longer cause terror to any one, since we know that they
+are a natural and inevitable consequence of the combined motions of
+the three great celestial bodies--the sun, the earth, and the moon;
+especially since we know that these motions are regular and permanent,
+and that we can predict, by means of calculation, the eclipses which
+will be produced in the future as well as recognize those which have
+occurred in the past.
+
+The following description of the total eclipse of 1860 will be found
+interesting. Mr. Lowe, who observed it at Santander, Spain, thus writes:
+
+“Before totality commenced, the colors in the sky and on the hills were
+magnificent beyond all description. The clear sky in the north assumed
+a deep indigo color, while in the west the horizon was first black
+like night. In the east the clear sky was very pale blue, with orange
+and red, like sunrise. On the shadow creeping across, the deep blue in
+the north changed, like magic, to pale, sunrise tints of orange and
+red, while the sunrise appearance in the east had changed to indigo.
+The darkness was great; the countenances of men were of a livid pink.
+The Spaniards lay down, and their children screamed with fear; fowls
+hastened to roost, ducks clustered together, pigeons dashed against the
+houses; flowers closed; many butterflies flew as if drunk, and at last
+disappeared. The air became very humid, so much so that the grass felt
+to one of the observers as if recently rained upon.”
+
+
+
+
+CHAPTER XIII.
+
+YET MORE ABOUT THE SUN.
+
+
+Having seen something of storms taking place on the sun’s photosphere,
+we must next give our attention to storms taking place at his edge. But
+it should be remembered that the said edge, far from being a mere rim
+to a flat surface, is a kind of horizon-line--is, in fact, just that
+part of the photosphere which is passing out of or coming under our
+sight. The surface there is, in kind, the same as the surface of the
+broad disk facing us. In watching outbursts at the edge of the sun, we
+have a side view instead of a bird’s-eye view.
+
+In the year 1871, Professor Charles A. Young, of Princeton, was looking
+at a large hydrogen cloud on the edge of the sun. When I speak of a
+“cloud,” it must not be supposed that anything like a damp, foggy,
+earthly cloud is meant. This solar cloud was a huge mass of red-hot
+gas, about one hundred thousand miles long, rising to a height of fifty
+thousand miles from the sun’s surface, and appearing to rest on glowing
+pillars of fire.
+
+The professor, while watching, was called away for half an hour. He
+came back, expecting to find things much as he had left them. Instead
+of this, a startling change had taken place. The whole mass of glowing
+fire seemed to have been actually “blown to shreds” by some tremendous
+outburst from below. In place of the motionless cloud were masses of
+scattered fire, each from about four thousand to fourteen thousand
+miles long, and a thousand miles wide.
+
+As the professor gazed, these “bits” of broken cloud rose rapidly
+upwards, away from the surface of the sun. When I say “rapidly,” I mean
+that the real movement, which the professor could calculate, was rapid.
+The seeming movements were of course slow, and over a small space. The
+actual motions were not tardy, for in ten minutes these huge, fiery
+cloud-pieces rushed upwards to a height of two hundred thousand miles
+from the edge of the sun, moving at a rate of at least one hundred and
+sixty-seven miles each second. Gradually they faded away.
+
+But what caused this sudden change? Just before the professor was
+interrupted, he had noticed a curious little brilliant lump--a sort of
+suspicious thunder-cloud appearance--below the quiet, bright cloud. And
+after this tremendous shattering, the little bright lump rose upwards
+into a huge mass of rolling flame, reaching like a pyramid to a height
+of fifty thousand miles. In the course of a few minutes these enormous
+flames could be seen to move and bend, and to curl over their gigantic
+tips. But they did not last long. At half-past twelve the professor
+had been called away; by half-past two the rolling flames completely
+vanished.
+
+Now, whatever may be the full explanation of this sight, there is no
+doubt that on that day was observed from earth a tremendous outburst,
+compared with which our mightiest volcanoes are like the sputtering of
+a farthing dip beside a roaring furnace. The awful force and greatness
+of such a solar eruption are more than we can possibly picture to
+ourselves. At our distance we may catch a faint glimpse of what is
+going on, and calculate speed of movement. But vividly to realize the
+actual terrific grandeur of what took place is past our power.
+
+Possibly this was much the same kind of outburst as that seen by the
+two English astronomers; only theirs was a bird’s-eye view, as it
+were, looking down on the top of the sight, while the professor had a
+side-view, certainly much the best for observation.
+
+It does not follow from what he saw that the eruption must have taken
+place exactly at the “edge” of the sun. Probably it happened near
+the edge. All he could say, was that the flames rose fifty thousand
+miles, and the pieces of cloud were carried two hundred thousand miles,
+away from the edge. The eruption may have begun on the other side of
+the sun, at any distance from the horizon-edge where it first became
+visible to earthly eyes.
+
+Also, while the professor found that the shattered cloudlets moved at
+a rate of about one hundred and sixty-seven miles each second, it is
+calculated that the first fearful outburst must have caused movement,
+near the surface of the sun, at a rate of at least three hundred miles
+each second. Probably the hydrogen cloud was borne upwards along with
+a vast mass of fragments flung out from the sun. We are here upon
+doubtful ground; but this tremendous power of eruption in the sun,
+and of driving matter out of and away from his surface, should not be
+forgotten.
+
+Though such a sun-storm as that just described is not often to be seen,
+yet there are at all times certain strange red prominences, or glowing
+flames, rising up here and there from the sun’s “limb.” Doubtless they
+rise also from other parts of the photosphere, though they are only
+visible to us when near enough to the edge to stand out beyond it.
+
+Seen during an eclipse, these prominences have clear, sharp outlines,
+and are usually bright rose-red in color. They are described as
+sometimes wide and low, sometimes tall and slender; sometimes jagged,
+sometimes regular; sometimes keeping long the same shape, sometimes
+changing quickly in a few minutes. They are said to be like flames,
+like mountains, like the teeth of a saw, like icebergs, like floating
+cloudlets.
+
+As to their height, from fifty to eighty thousand miles is nothing
+unusual. We must not speak of Mont Blanc or Mount Everest here. Jupiter
+placed bodily on the surface of the sun, beside such a fire-mountain,
+would not far overtop it. The earth, Venus, Mars, and Mercury, would
+lie like little toy-balls at its foot. And these are common-sized
+sun-flames. One was measured which reached to the enormous height
+of two hundred thousand miles. The spectroscope shows these solar
+prominences or jets to be made--at least in part--of burning hydrogen
+gas.
+
+Beyond the sierra or chromatosphere--that border of rippling, crimson
+flame-billows round the edge of the sun, with red flame-mountains
+rising out of it here and there--beyond these, stretches the corona.
+The corona, as seen from earth, is a bright, far-reaching glory of
+light, shining round the sun in a total eclipse. The moon then comes
+between the sun and the earth, her dark, round body creeping over the
+face of the sun till the bright photosphere is completely covered. But
+the sierra and the tall, red flames stand out from behind the black
+moon, and the beautiful, soft corona-light stretches far beyond.
+
+[Illustration: SOLAR CORONA AND PROMINENCE.]
+
+It was long doubted whether the corona really belonged to the sun or to
+the moon. There seems now no doubt that it is a part of the sun.
+
+Various descriptions of the corona have been given at different
+times, as observed during different eclipses. It has been seen as a
+steady, beamy, white cloud behind the moon, showing no flickering.
+It has been seen marked with bright lines of light, and seeming to
+move rapidly round and round. It has been seen silvery white, sending
+off long streams of brightness. It has been seen in the form of
+white light, with bluish rays running over it. It has been seen with
+entangled jets of light, like “a hank of thread in disorder.” It has
+been seen silvery-white again, with a faint tinge of greenish-violet
+about the outer edge. It has been seen from a high mountain-top as a
+mass of soft, bright light, “through which shot out, as if from the
+circumference of the moon, straight, massive, silvery rays, seeming
+distinct and separate from each other, to a distance of two or three
+diameters of the lunar disk, the whole spectacle showing as upon a
+background of diffused, rose-colored light.”
+
+Majestic, indeed, are the proportions of some of those mighty flames
+which leap from the surface of the sun, yet these flames flicker, as
+do our terrestrial flames, when we allow them time comparable to their
+gigantic dimensions. Drawings of the same prominence often show great
+changes in a few hours, or even less. The magnitude of the changes
+could not be less than many thousands of miles, and the actual velocity
+with which such masses move is often not less than one hundred miles
+a second. Still more violent are the solar convulsions, which some
+observers have been so fortunate as to behold, when from the sun’s
+surface, as from a mighty furnace, vast incandescent masses are
+projected upwards. All indications point to the surface of the sun as
+the seat of the most frightful storms and tempests, in which the winds
+sweep along incandescent vapors.
+
+The corona consists of two parts--the inner and brighter corona, the
+outer and fainter corona. The shape of the whole seems to change much
+at different times. The outer edge is usually blurred and indistinct,
+fading gently away.
+
+Many explanations have been suggested. At one time the corona was
+supposed to be a solar atmosphere, reflecting light like our own
+atmosphere. Some have thought the light might be caused by countless
+myriads of meteorite systems, revolving in the close neighborhood of
+the sun. Some suppose it may be owing, in part at least, to solar
+eruptions, and the pouring outward of burning gas and matter. But our
+knowledge of the true nature of the corona is yet in its infancy.
+
+A few closing words as to the size and weight of the sun. In diameter,
+eight hundred and fifty-eight thousand miles, and in bulk equal to
+one million two hundred and eighty thousand earths, his weight is in
+proportion less. Our earth is about four times as dense as the sun. If
+her size were increased to the sun’s size, her density being the same
+as now, she would be very much heavier than the sun, and would attract
+much more strongly. Still, though the sun is of lighter materials than
+the earth, his immense size gives him weight equal to seven hundred and
+fifty times as much as all the planets put together.
+
+The attraction on the surface of the sun is also very great--so great
+that we can hardly picture it to ourselves. If life exists there at
+all--supposing it possible that any kind of life can be in such a
+fiery atmosphere--it must be life very different from any known in
+this world. A man who on earth weighs one hundred and sixty pounds,
+and walks lightly erect, would, on the sun, lie helplessly bound to
+the ground, crushed by his own overpowering weight. It is said that a
+cannon-ball, reposing on the sun, if lifted one inch and allowed to
+fall, would dash against the ground with a speed three times greater
+than that of our fastest express-trains. For weight on earth is merely
+caused by the amount of force with which the earth draws downward a
+body towards herself--a force greater or less according to the density
+of that body. So weight on the sun would be immensely increased by his
+immensely greater power of attraction.
+
+[Illustration: COMPARATIVE SIZE OF THE EARTH AND SUN.]
+
+It is an interesting question how far the sun’s attractive influence
+reaches effectually through space. The nearer a body is to the sun,
+the greater the attraction which he exercises over it. At the distance
+of the planet Mercury, a speed of twenty-nine miles each second is
+needful to overcome or balance it sufficiently for the planet to remain
+in his orbit. At the distance of the planet Neptune, about three miles
+each second is enough. If a planet were journeying at four times the
+distance of Neptune, the speed would need to be not over two miles each
+second, lest the planet should break loose and wander away. But even
+two miles a second is no mean speed--more than seven thousand miles an
+hour. If we come to speak of that which we on earth call rapid motion,
+we shall gain a clearer idea as to the extent of the sun’s power.
+
+Suppose a planet were traveling through space at the rate of one of our
+fastest express-trains--sixty miles an hour. It has been calculated
+that, unless the sun’s attraction were interfered with and overpowered
+by some nearer sun, the said planet, though placed at a distance ten
+or twelve times as great as that of the far-off star Alpha Centauri,
+would still be forced by the sun’s attraction to journey round him in a
+closed orbit. At such a speed it would not be free to wander off into
+the depths of space.
+
+
+
+
+CHAPTER XIV.
+
+MORE ABOUT THE MOON.
+
+
+From a globe all fire, all energy, all action, we come to a globe
+silent, voiceless, changeless, lifeless. So, at least, the moon seems
+to us. But it will not do to speak too confidently.
+
+True, we can find no trace of an atmosphere in the moon. If there is
+any atmosphere at all, it must be so thin as to be less than that which
+we on earth count as actually none. We pump away the air from a glass
+inclosure in an air-pump, and say the glass is empty. Only it is not
+quite empty. There is always just a very little air remaining, though
+so little that fire would not burn and animals could not live in it.
+Some believe that air, up to that amount, may be found in the moon. But
+this is much the same as to say there is none at all. For, of course,
+with either no air or so very little air, life can not possibly exist
+on the moon. We can not imagine such a thing for a moment. That is
+just how the matter stands. We “can not imagine,” and therefore we
+conclude it to be an impossibility. As if we knew a hundredth part of
+the possibilities in any one corner of God’s great universe! As if our
+being unable to picture a thing proves that thing not to exist!
+
+Suppose we had always lived in tropical heat, and had never seen,
+known, or heard of such a fact as life in Arctic snows. Should we
+consider it a thing possible? Suppose we had always lived on dry land,
+with never a sight of sea or river or pond, and never a proof that
+animal life could exist under water--aye, and that some living animals
+may be suffocated by air, just as other living animals are suffocated
+by water. Should we not, in our wisdom, reason out such a state of
+affairs to be utterly impossible?
+
+There _may_ be no life on the moon. It _may_ be that she is now passing
+through a dead, cold, blasted stage, either at the close of some past
+history, or in preparation for some future history--or both. But, on
+the other hand, it _may_ be that the moon is no less full of life than
+the earth; only the life must be different in kind, must be something
+which we do not know any thing at all about.
+
+The moon is very much smaller than the earth. Her diameter is about
+two-sevenths of the earth’s diameter; her entire surface is about
+two twenty-sevenths of the earth’s surface; her size is about two
+ninety-ninths of the earth’s size; and her whole weight is about
+one-eightieth of the earth’s weight. Attraction or gravitation on the
+surface of the moon is very different from what it is on the earth. Her
+much smaller bulk greatly lessens her power of attraction. While a man
+from earth would, on the surface of the sun--supposing he could exist
+there at all--lie helpless, motionless, and crushed by his own weight,
+he would on the moon find himself astonishingly light and active. A
+leap over a tall house would be nothing to him.
+
+[Illustration: THE MOON--AN EXPIRED PLANET.]
+
+The moon, unlike the sun, has no light or heat of her own to give out.
+She shines merely by reflected light. Rays of sunlight falling upon
+her, rebound thence, and find their way earthward. This giving of
+reflected light is not a matter all on one side. We yield to the moon a
+great deal more than she yields to us. Full earth, seen from the moon,
+covers a space thirteen times as large as full moon seen from earth.
+
+Perhaps you may have noticed, soon after new moon, when a delicate
+crescent of silver light shows in the sky, that within the said
+crescent seems to lie the body of a round, dark moon, only not
+perfectly dark. It shows a faint glimmer. That glimmer is called
+earth-shine. The bright crescent shines with reflected sunlight. The
+dim portion shines with reflected earth-light. What a journey those
+rays have had! First, leaving the sun, flashing through ninety-three
+millions of miles to earth, rebounding from earth and flashing over two
+hundred and forty thousand miles to the dark shaded part of the moon,
+then once more rebounding and coming back, much wasted and enfeebled,
+across the same two hundred and forty thousand miles, to shine dimly in
+your eyes and mine. The popular description of this particular view of
+the moon is “the old moon in the arms of the new.”
+
+Now about the _phases_ of the moon; that is, her changes from “new”
+to “full,” and back again to “new.” If the moon were a starlike body,
+shining by her own light, she would always appear to be round. But as
+she shines by reflected sunlight, and as part of her bright side is
+often turned away from us, the size and shape of the bright part seem
+to vary. For, of course, only that half of the moon which is turned
+directly towards the sun is bright. The other half turned away is dark,
+and can give out no light at all, unless it has a little earth-shine to
+reflect.
+
+As the moon travels round the earth, she changes gradually from new to
+full moon, and then back to new again. “New moon” is when the moon, in
+her orbit, comes between the sun and the earth. The half of her upon
+which the sun shines is turned away from us, and only her dark side is
+towards us. So at new moon she is quite invisible. It is at new moon
+that an eclipse of the sun takes place, when the moon’s orbit carries
+her in a line precisely between sun and earth.
+
+Passing onwards round the earth, the moon, as we get a little glimpse
+of her shining side, first shows a slender sickle of light, which
+widens more and more till she reaches her first quarter. She is then
+neither between earth and sun, nor outside the earth away from the sun,
+but just at one side of us, passing over the earth’s own orbit. Still,
+as before, half her body is lighted up by the sun. By this time _half_
+the bright part and _half_ the dark part are turned towards us; so
+that, seeing the bright quarter, we name it the “first quarter.”
+
+On and on round us moves the moon, showing more light at every step.
+Now she passes quite outside the earth’s orbit, away from the sun. Not
+the slightest chance here of an eclipse of the sun, though an eclipse
+of the moon herself is quite possible. But more of that presently. As
+she reaches a point in a line with earth and sun--only generally a
+little higher or lower than the plane of the earth’s orbit--her round,
+bright face, shining in the sun’s rays, is turned exactly towards us.
+Then we have “full moon.”
+
+Still she goes on. Once more her light narrows and wanes, as part of
+her bright half turns away. Again at the “last quarter,” as at the
+first, she occupies a “sideways” position, turning towards us half
+her bright side and half her dark side. Then she journeys on, with
+lessening rim of light, till it vanishes, and once more we have the
+dark, invisible “new moon.”
+
+It was these phases and aspects of the moon which formerly gave birth
+to the custom of measuring time by months, and by weeks of seven days,
+on account of the return of the moon’s phases in a month, and because
+the moon appears about every seven days, so to say, under a new form.
+Such was the first measure of time; there was not in the sky any signal
+of which the differences, the alternations, and the epochs were more
+remarkable. Families met together at a time fixed by some lunar phase.
+
+The new moons served to regulate assemblies, sacrifices, and public
+functions. The ancients counted the moon from the day they first
+perceived it. In order to discover it easily, they assembled at evening
+upon the heights. The first appearance of the lunar crescent was
+watched with care, reported by the high priest, and announced to the
+people by the sound of trumpets. The new moons which correspond with
+the renewal of the four seasons were the most solemn; we find here the
+origin of the “ember weeks” of the Church, as we find that of most of
+our festivals in the ceremonies of the ancients. The Orientals, the
+Chaldeans, Egyptians, and Jews religiously observed this custom.
+
+An eclipse of the sun has already been described. An eclipse of the
+moon is an equally simple matter. An eclipse of the sun is caused by
+the dark, solid body of the moon passing just between earth and sun,
+hiding the sun from us, and casting its shadow upon the earth. An
+eclipse of the moon is also caused by a shadow--the shadow of our own
+earth--falling upon the moon.
+
+Here again, if the plane of the moon’s orbit were the same as ours,
+eclipses of the moon would be very common. As it is, her orbit carries
+her often just a little too high or too low to be eclipsed, and it is
+only now and then, at regular intervals, that she passes through the
+shadow of the earth.
+
+If a large, solid ball is hung up in the air, with bright sunlight
+shining on it, the sunlight will cast a _cone of shadow_ behind the
+ball. It will throw, in a direction just away from the sun, a long,
+round shadow, the same as the ball at first, but tapering gradually off
+to a point. If the ball is near the ground, a round shadow will rest
+there, almost as large as the ball. The higher the ball is placed, the
+smaller will be the round shadow, till at length, if the ball be taken
+far enough upwards, the shadow will not reach the ground at all. Our
+earth and all the planets cast just such tapering cones of dark shadow
+behind them into space. The cone always lies in a direction away from
+the sun.
+
+It is when the moon comes into this shadow that an “eclipse of the
+moon” takes place. Sometimes she only dips half-way into it, or just
+grazes along the edge of it, and that is called a “partial eclipse.”
+Sometimes she goes in altogether, straight through the midst of the
+shadow, so that the whole of her bright face for a short time grows
+quite dark. Then we have a “total lunar eclipse.”
+
+
+
+
+CHAPTER XV.
+
+YET MORE ABOUT THE MOON.
+
+
+There are two ways of thinking about the moon. One way is to consider
+her as merely the earth’s attendant satellite. The other way is to
+consider her as our sister-planet, traveling with us round the central
+sun.
+
+The first is the more common view; but the second is just as true as
+the first.
+
+For the sun does actually pull the moon towards himself, with a very
+much stronger pulling than that of the earth. The attraction of the sun
+for the moon is more than double the attraction of the earth for the
+moon. If it were not that he pulls the earth quite as hard as he pulls
+the moon, he would soon overpower the earth’s attraction, and drag the
+moon away from us altogether.
+
+People are often puzzled about the orbit or pathway of the moon through
+the heavens. For in one sense they have to think of her as traveling
+round and round in a fixed orbit, with the earth in the center. In
+another sense they have to think of her as always journeying onwards
+with the earth in her journey round the sun, and thus never returning
+to the same point.
+
+There are two ways of meeting this difficulty. First of all, remember
+that the one movement does not interfere with the other. Just as in the
+case of the earth traveling round the sun, and also traveling onward
+with him through space; just as in the case of a boy walking round and
+round a mast, and also being borne onwards by the moving vessel,--so it
+is here. The two movements are quite separate and independent of each
+other. As regards the earth alone, the moon journeys round and round
+perpetually, not in a circle, but in a pathway which comes near being
+an ellipse. As regards the actual _line_ which the moon’s movements may
+be supposed to draw in space, it has nothing elliptical about it, since
+no one point of it is ever reached a second time by the moon.
+
+But according to this last view of the question, nobody ever can or
+will walk in a circle or an oval. Take a walk round your grass-plot,
+measuring your distance carefully at all points from the center. Is
+that a circle? All the while you moved, the surface of the earth was
+rushing along and bearing you with it, and the whole earth was hurrying
+round the sun, and was being also carried by him in a third direction.
+Whatever point in space you occupied when you started, you can _never
+fill that particular part of space again_. The two ends of your
+so-called circle can never be joined.
+
+But then you may come back to the same point _on the grass_, as
+that from which you started. And this is all that really signifies.
+Practically you have walked in a circle. Though not a circle as regards
+space generally, it is a circle as regards the earth. So also the moon
+comes back to the same point _in her orbit round the earth_. Letting
+alone the question of space, and considering only the earth, the moon
+has--roughly speaking--journeyed in an ellipse. You may, however, look
+at this matter in quite another light. Forget about the moon being the
+earth’s satellite, and think of earth and moon as two sister-planets
+going round the sun in company.
+
+The earth, it is true, attracts the moon. So, also, the moon attracts
+the earth; though the far greater weight of the earth makes her
+attraction to be far greater. If earth and moon were of the same size,
+they would pull each other with equal force.
+
+But though the pull of the earth upon the moon is strong, the pull of
+the sun upon the moon is more than twice as strong. And greatly as the
+earth influences the moon, yet the actual center of the moon’s orbit is
+the sun, and not the earth. Just as the earth travels round the sun, so
+also the moon travels round the sun.
+
+The earth travels steadily in her path, being only a little swayed and
+disturbed by the attraction of the moon. The moon on the contrary,
+while traveling in her orbit, is very much swayed and disturbed indeed
+by the earth’s attraction. In fact, instead of being able to journey
+straight onwards like the earth, her orbit is made up of a succession
+of delicate curves or scallops, passing alternately backwards and
+forwards over the orbit of the earth. Now she is behind the earth; now
+in front of the earth; now between earth and sun; now outside the earth
+away from the sun. The order of positions is not as here given, but
+each is occupied by her in turn. Sometimes she moves quickly, sometimes
+she moves slowly, just according to whether the earth is pulling her
+on or holding her back. Two hundred and forty thousand miles sounds
+a good deal. That is the distance between earth and moon. But it is,
+after all, a mere nothing, compared with the ninety-three millions of
+miles which separate the sun from the earth and moon.
+
+If we made a small model, with the sun in the center, and the earth and
+moon traveling a few inches off, only one slender piece of wire would
+be needed to represent the path of earth and moon together. For not
+only would the earth and the moon be so small as to be quite invisible,
+but the whole of the moon’s orbit would have disappeared into the
+thickness of the single wire. This question of the moon’s motions is
+in its nature intricate, and in its details quite beyond the grasp of
+any beginner in astronomy. But so much at least may be understood,
+that though the earth’s attraction powerfully affects the moon, and
+causes in her motions _perturbations_, such as have been already spoken
+about as taking place among the planets, yet that in reality the great
+controlling power over the moon is the attraction of the sun.
+
+The tides of the ocean are chiefly brought about by the moon’s
+attraction. The sun has something to do with the matter, but the moon
+is the chief agent. This action of the moon can best be seen in the
+southern hemisphere, where there is less land. As the moon travels
+slowly round the earth, her attraction draws up the yielding waters
+of the ocean in a vast wave which travels slowly along with her. The
+same pulling which thus lifts a wave on the side of the earth towards
+the moon, also pulls the earth gently _away from_ the water on the
+opposite side, and causes a second wave there. The parts of the ocean
+between these two huge waves are depressed, or lower in level. These
+two waves on the opposite sides of the earth sweep steadily onwards,
+following the moon’s movements,--not real, but seeming movements,
+caused by the turning of the earth upon her axis.
+
+Once in every twenty-four hours these wide waves sweep round the whole
+earth in the southern ocean. They can not do the same in the north, on
+account of the large continents, but offshoots from the south waves
+travel northwards, bringing high-tide into every sea and ocean inlet.
+If there were only one wave, there would be only one tide in each
+twenty-four hours. As there are two waves, there are two tides, one
+twelve hours after the other. In the space between these two high-tides
+we have low-tide.
+
+Twice every month we have very high and very low tides. Twice every
+month we have tides not so high or so low. The highest are called
+“spring-tides,” and the lowest “neap-tides.” When the moon is between
+us and the sun, or when she is “new moon,” there are spring-tides;
+for the pull or attraction of sun and moon upon the ocean act exactly
+together. It is the same at full moon, when once more the moon is in a
+straight line with earth and sun. But at the first and last quarters,
+when the moon has her _sideways_ position, and when the sun pulls in
+one direction and the moon pulls in another, each undoes a little of
+the other’s work. Then we only have neap-tides; for the wave raised is
+smaller, and the water does not flow so high upon our shores.
+
+In speaking of the surface of the moon, we are able only to speak
+about one side. The other is entirely hidden from us. This is caused
+by the curious fact that the moon turns on her axis and travels round
+the earth in exactly the same length of time. One-half of the moon is
+thus always turned towards us, though of that half we can only see so
+much as is receiving the light of the sun. But the half turned in our
+direction is always the same half. One part of the moon--not quite so
+much as half, though always the same portion--is turned away from us. A
+small border on each side of that part becomes now and then visible to
+us, owing to certain movements of the earth and the moon.
+
+What sort of a landscape may lie in the unknown district, it is idle to
+imagine. Many guesses have been made. Some have supposed it possible
+that air _might_ be found there; that water _might_ exist there; that
+something like earthly animals _might_ live there. It is difficult to
+say what may not be, in a place about which we know nothing whatever.
+But judging from our earthly experience, nothing seems more unlikely
+than that air, water, clouds, should be entirely banished from over
+one-half of a globe, and collected together in the space remaining.
+
+We are on safer ground when we speak about that part of the moon
+which is turned towards us. For we can say with confidence that if
+any atmosphere exist there, it must be in thickness less than the
+two-thousandth part of our earthly atmosphere. It seems equally clear
+that water also must be entirely wanting. The tremendous heat of the
+long lunar day would raise clouds of vapor, which could not fail to
+be visible. But no such mistiness ever disturbs the sharply-defined
+outline of the moon, and no signs of water action are seen in the
+craggy mountains and deep craters.
+
+[Illustration: THE LUNAR CRATER COPERNICUS.]
+
+The craters which honeycomb the surface of the moon are various in
+size. Many of the larger ones are from fifty to a hundred miles in
+diameter. These huge craters--or, as we may call them, deep circular
+plains--are surrounded by mighty mountain ramparts, rising to the
+height of thousands of feet. Usually they have in their center a
+sugar-loaf or cone-shape mountain, or even two or more such mountains,
+somewhat lower in height than the surrounding range. The sunset-lights
+upon certain of these distant mountain-peaks were first watched by
+Galileo through his telescope, and have since been seen by many an
+observer--intense brightness contrasting with intense blackness of
+shadow.
+
+In addition to her great craters, the moon seems to be thickly covered
+with little ones, many of them being as small as can be seen at all
+through a telescope. Whether these are all volcano-craters remains to
+be discovered. It is not supposed that any of them are now active. From
+time to time, signs of faint changes on the moon’s surface have been
+noticed, which it was thought might be owing to volcanic outbursts.
+Such an outburst as the worst eruptions of Mount Vesuvius would be
+invisible at this distance. But the said changes may be quite as well
+accounted for by the startling fortnightly variations of climate which
+the moon has to endure. The general belief now inclines to the idea
+that the moon-volcanoes are extinct, though no doubt there was in the
+past great volcanic activity there.
+
+A description has been given earlier of the rain of meteorites
+constantly falling to our earth, and only prevented by the atmosphere
+from becoming serious. But the moon has no such protecting atmosphere,
+and the amount of cannonading which she has to endure must be by no
+means small. Perhaps in past times, when her slowly-cooling crust
+was yet soft, these celestial missiles showering upon her may have
+occasionally made deep round holes in her surface.
+
+This is another guess, which time may prove to be true. Guesses at
+possible explanations of mysteries do no harm, so long as we do not
+accept them for truth without ample reason.
+
+[Illustration: LUNAR ERUPTION--BRISK ACTION.]
+
+The origin of the lunar craters must be referred to some ancient epoch
+in the moon’s history. How ancient that epoch is we have no means of
+knowing; but in all probability the antiquity of the lunar craters is
+enormously great. At the time when the moon was sufficiently heated
+to have these vast volcanic eruptions, of which the mighty craters
+are the survivals, the earth must have been very much hotter than it
+is at present. It is not, indeed, at all unreasonable to believe that
+when the moon was hot enough for its volcanoes to be active, the earth
+was so hot that life was impossible on its surface. This supposition
+would point to an antiquity for the moon’s craters far too great to
+be estimated by the centuries and the thousands of years which are
+adequate for the lapse of time as recognized by the history of human
+events. It seems not unlikely that millions of years may have elapsed
+since the mighty craters of Plato or of Copernicus consolidated into
+their present form.
+
+[Illustration: LUNAR ERUPTION--FEEBLE ACTION.]
+
+It will now be possible for us to attempt to account for the formation
+of the lunar craters. The most probable views on the subject are
+certainly those adopted by Mr. Nasmyth, as represented in the cuts,
+though it must be admitted that they are by no means free from
+difficulty. We can explain the way in which the rampart around the
+lunar crater is formed, and the great mountain which so often adorns
+the center of the plain. The first of these cuts contains an imaginary
+sketch of a volcanic vent on the moon in the days when the craters were
+active. The eruption is here in the full flush of its energy, when the
+internal forces are hurling forth a fountain of ashes or stones, which
+fall at a considerable distance from the vent; and these accumulations
+constitute the rampart surrounding the crater. The second cut depicts
+the crater in a later stage of its history. The prodigious explosive
+power has now been exhausted, and perhaps has been intermitted for some
+time. A feeble jet issues from the vent, and deposits the materials
+close around the orifice, and thus gradually raises a mountain in the
+center.
+
+Besides the craters and their surrounding barriers, there are ranges of
+mountains on the moon, and flat plains which were once named “seas,”
+before it was found that water did not exist there. Astronomers also
+see bright ridges, or lines, or cracks of light, hard to explain.
+
+One of the chief craters is called “Ptolemy,” and in size it is roughly
+calculated to be no less than one hundred and fourteen miles across.
+Another, “Copernicus,” is about fifty-six miles; and another, “Tycho,”
+about fifty-four miles. The central cone-mountain of Tycho is five
+thousand feet high. The crater of “Schickard” is supposed to be as much
+as one hundred and thirty-three miles in diameter.
+
+Astronomers have agreed to name these craters after the great
+discoverers who enlarged our knowledge of the solar and sidereal
+systems. It is fitting that these great names are suggested every time
+the moon is seen through a telescope. To Ptolemy we are indebted for
+what is known as “The Ptolemaic System of the Universe,” which makes
+the earth the center around which the sun, moon, planets, and stars all
+revolve, and explains the apparently erratic movements of the planets
+by supposing their orbits to be epicycles; that is, curves returning
+upon themselves and forming loops. Tycho Brahe was willing to allow,
+with Copernicus, that the planets all revolved around the sun; but he
+taught that both sun and planets turned around the earth.
+
+The system known as “The Copernican” is now known to be the only true
+one, and it is universally accepted. It is so called after Nicolaus
+Copernicus, who was born in Thorn, Prussia, February 19, 1473. He was
+educated for the Church, and studied medicine, but devoted himself
+especially to astronomy.
+
+Without being precisely a great genius, this quiet and thoughtful monk
+seems to have been wise far beyond the age in which he lived, and
+remarkable for his independence of mind. He had a “profound sagacity,”
+and a wide general grasp of scientific subjects.
+
+The extremely complicated and cumbrous nature of the Ptolemaic
+system appeared to his judgment hardly compatible with the harmony
+and simplicity elsewhere characteristic of nature. Moreover, he was
+impressed and perplexed by the very marked changes in the brilliancy
+of the planets at different seasons. These changes _now_ are no
+difficulty at all. Venus, Mars, Jupiter, when on the same side of the
+sun as ourselves, are comparatively near to us, and naturally look much
+more bright in consequence of that nearness than when they are on
+the opposite side of the sun from ourselves. But under the Ptolemaic
+system, each planet was supposed to revolve round our earth, and to
+be always at about the same distance from us; therefore, why such
+variations in their brilliancy?
+
+[Illustration: NICOLAUS COPERNICUS.]
+
+During thirty-six long years he patiently worked out this theory, and
+during part of those thirty-six years he wrote the one great book of
+his lifetime, explaining the newer view of the Solar System which
+had taken hold of his reason and imagination. This book, named _De
+Revolutionibus Orbium Cœlestium_, or, “Concerning the Revolutions of
+the Celestial Spheres,” which came out only a few hours before his
+death, was dedicated to the Bishop of Rome--a little touch of worldly
+wisdom which doubtless staved off for a while the opposition of the
+Vatican.
+
+Copernicus was not the first who thought of interpreting the
+celestial motions by the theory of the earth’s motion. That immortal
+astronomer has taken care to give, with rare sincerity, the passages
+in the ancient writers from which he derived the first idea of the
+probability of this motion--especially Cicero, who attributed this
+opinion to Nicetas of Syracuse; Plutarch, who puts forward the names
+of Philolaus, Heraclides of Pontus, and Ecphantus the Pythagorean;
+Martianus Capella, who adopted, with the Egyptians, the motion of
+Mercury and Venus around the sun, etc. Even a hundred years before the
+publication of the work of Copernicus, Cardinal Nicolas of Cusa, in
+1444, in his great theological and scientific encyclopedia, had also
+spoken in favor of the idea of the earth’s motion and the plurality
+of worlds. From ancient times to the age of Copernicus, the system of
+the earth’s immobility had been doubted by clear-sighted minds, and
+that of the earth’s motion was proposed under different forms. But all
+these attempts still leave to Copernicus the glory of establishing it
+definitely.
+
+Not content with merely admitting the idea of the earth’s motion as a
+simple arbitrary hypothesis, which several astronomers had done before
+him, he wished--and this is his glory--to demonstrate it to himself
+by acquiring the conviction by study, and wrote his book to prove it.
+The true prophet of a creed, the apostle of a doctrine, the author of
+a theory, is the man who, by his works, demonstrates the theory, makes
+the creed believed in, and spreads the doctrine. He is not the creator.
+“There is nothing new under the sun,” says an ancient proverb. We may
+rather say, Nothing which succeeds is entirely new. The newborn is
+unformed and incapable. The greatest things are born from a state of
+germ, so to say, and increase unperceived. Ideas fertilize each other.
+The sciences help each other; progress marches. Men often feel a truth,
+sympathize with an opinion, touch a discovery, without knowing it. The
+day arrives when a synthetical mind feels in some way an idea, almost
+ripe, becoming incarnate in his brain. He becomes enamored of it, he
+fondles it, he contemplates it. It grows as he regards it. He sees,
+grouping round it, a multitude of elements which help to support it.
+To him the idea becomes a doctrine. Then, like the apostles of good
+tidings, he becomes an evangelist, announces the truth, proves it by
+his works, and all recognize in him the author of the new contemplation
+of nature, although all know perfectly well that he has not invented
+the idea, and that many others before him have foreseen its grandeur.
+
+Such is the position of Copernicus in the history of astronomy. The
+hypothesis of the earth’s motion had been suggested long before his
+birth on this planet. This theory counted partisans in his time.
+But he--he did his work. He examined it with the patience of an
+astronomer, the rigor of a mathematician, the sincerity of a sage, and
+the mind of a philosopher. He demonstrated it in his works. Then he
+died without seeing it understood, and it was not till a century after
+his death that astronomy adopted it, and popularized it by teaching
+it. However, Copernicus is really the author of the true system of the
+world, and his name will remain respected to the end of time.
+
+The so-called “seas” on the moon are those large dark spots to be seen
+on its surface, in the shape of “eyes, nose, and mouth,” or of the
+famous old man with his bundle of sticks. The brighter parts are the
+more mountainous parts.
+
+The chief ranges of lunar mountains have been named by astronomers
+after mountains on earth, such as the Apennines, the Alps, the
+Caucasian range, the Carpathian and the Altai Mountains.
+
+
+
+
+CHAPTER XVI.
+
+MERCURY, VENUS, AND MARS.
+
+
+Once again we have to journey through the high-roads of the Solar
+System, paying a brief visit to each in turn of our seven chief
+brother-and-sister planets, and learning a few more leading facts about
+them. Having gone the same way before, it will not now seem quite so
+far.
+
+Busy, hurrying Mercury! we must meet him first in his wild rush through
+space. If he were to slacken speed for a single instant, he would begin
+to fall with fearful rapidity towards the sun. And if Mercury were to
+drop into one of those huge black chasms of rent furnace-flame on the
+sun’s surface, there would be a speedy end to his life as a planet.
+
+Mercury’s day is about the same length as our day, and his year is
+about one quarter the length of our year. If Mercury has spring,
+summer, autumn, and winter, each season must be extremely short; but
+this depends upon whether Mercury’s axis slopes like the earth’s
+axis--a matter difficult to find out. Mercury is always so near to the
+sun, that it is by no means easy to observe him well.
+
+We know more about his orbit than his axis. The earth’s orbit, as
+before explained, is not a circle, but an ellipse or oval. Mercury’s
+orbit is an ellipse also, and a much longer--or, as it is called, a
+more eccentric--ellipse. The earth is three millions of miles nearer
+to the sun at one time of the year, than six months before or after.
+Mercury is no less than fifteen millions of miles nearer at one time
+than another, which must make a marked difference in the amount of heat
+received.
+
+Even when the distance is greatest, the sun as seen from Mercury looks
+four and a half times as large as the sun we see. What a blazing
+splendor of light! It is not easy to imagine human beings living there,
+in such heat and glare, and with either no changes of season at all, or
+such very short seasons rapidly following one another. Mercury may, and
+very likely does, abound with living creatures, as much as the earth
+abounds with them; only one fancies they must be altogether a different
+kind of living creatures from any ever seen on earth. And yet we do not
+know. Man can so wonderfully adapt himself or be adapted to different
+climates on earth, from extreme heat to extreme cold, that we can not
+tell how far this adapting power may reach.
+
+Both Mercury and Venus seem to be enfolded in dense, cloud-laden
+atmospheres, rarely parting so as to allow us to get even a glimpse
+of the real planets within the thick, light-reflecting covering. Some
+have thought that a heavy, moist, protecting atmosphere may help to
+ward off the intense heat, and to make Mercury a more habitable place.
+Our earthly atmosphere is rather of a kind to store up heat, and to
+make us warmer than we should be without it; but there might be vapors
+differently constituted which might act in some other way. At all
+events, we know how easily God can have adapted either the planet to
+the creatures he meant to place there, or the creatures to the climate.
+“All things are possible” to him. The how and the what are interesting
+questions for us, but we must often be content to wait for an answer.
+
+A thick, gray ring or belt has been noticed round the small, black disk
+of Mercury, while it has passed between us and the sun. The edge of
+Mercury, seen against the bright photosphere beyond, would, if there
+were no atmosphere, be sharp and clear as the edge of the airless moon.
+This surrounding haze seems to show that Mercury has an atmosphere. The
+sunlight reflected from Mercury’s envelope of clouds shines at least as
+brightly as if it were reflected from his solid body.
+
+The small size of Mercury makes attraction on his surface much less
+than on earth. A lump of iron weighing on earth one pound, would weigh
+on Mercury only about seven ounces, or less than half as much. So a
+man would be a very light leaper indeed there, and an elephant might
+be quite a frolicsome animal. If there are star-gazers in Mercury, and
+if the cloud-laden atmosphere allows many clear views of the sky, the
+earth and Venus must both be beautiful to look upon. Each of the two
+would shine far more brightly than Jupiter, as seen at his best from
+earth.
+
+Like Mercury, Venus, the next planet, has an orbit lying inside our
+orbit. Mercury and Venus are always nearer to the sun than we are;
+and if Mercury and Venus traveled round the sun in orbits, the planes
+of which were exactly the same as the plane of the earth’s orbit, we
+should very often see them creeping over the surface of the sun. Not
+that they really “creep over” it; only, as they journey between the sun
+and us, we can see them pass like little black dots across the sun’s
+disk. This is the same thing as when the moon passes across the sun’s
+disk and eclipses it. But Mercury and Venus are too far away from us to
+cause any eclipse of the sun’s light.
+
+Mercury has given more trouble to astronomers than any other member of
+the system; for, owing to his proximity to the sun, he is usually lost
+in the solar glory, and is never seen in a dark part of the heavens,
+even at the time of his greatest distance. This circumstance, together
+with a small mass and an immense velocity, renders it difficult to
+catch and watch him. In high latitudes, where the twilight is strong
+and lengthened, while mists often overhang the horizon, the planet can
+seldom be seen with the naked eye. Hence an old astro-meteorologist
+contemptuously describes him as “a squirting lacquey of the sun, who
+seldom shows his head in these parts, as if he was in debt.” Copernicus
+lamented that he had never been able to obtain a sight of Mercury; and
+the French astronomer Delambre saw him not more than twice with the
+naked eye.
+
+The most favorable times for making observations are about an hour and
+three-quarters before sunrise in autumn, and after sunset in spring;
+but very clear weather and a good eye are required. At certain periods,
+when between the earth and the sun, on a line joining the centers of
+the two bodies, Mercury appears projected on the solar disk as a small,
+round, dark spot. This is called a _transit_, and would occur during
+every revolution if the plane of his orbit coincided with that of the
+orbit of the earth. But as one-half of his orbit is a little above
+that of the earth, and the other half a little below it, he passes
+above or below the sun to the terrestrial spectator, except at those
+intervals, when, being between us and the sun, he is also at one of the
+two opposite points where the planes of the respective orbits intersect
+each other. Then, stripped of all luster, the planet passes over
+the face of the great luminary as a black circular speck, affording
+evidence of his shining by reflected light, and of his spherical form.
+
+The first transit of Mercury recorded in history was predicted by
+Kepler, and witnessed by Gassendi, at Paris, on the morning of a
+cloudy day, the 7th of November, 1631. It was toward nine o’clock
+when he saw the planet; but owing to its extreme smallness, he was
+at first inclined to think it was a minute solar spot. It was then
+going off the sun; and made its final egress toward half-past ten. The
+observed time of the transit was nearly five hours in advance of the
+computed time. This was a very satisfactory accordance for that age
+between theory and observation; but it was the effect of a fortuitous
+combination of circumstances, rather than of computations founded
+upon well-established data. “The crafty god,” wrote Gassendi, in the
+peculiar style of his day, “had sought to deceive astronomers by
+passing over the sun a little earlier than was expected, and had drawn
+a veil of dark clouds over the earth in order to make his escape more
+effectual. But Apollo, knowing his knavish tricks from his infancy,
+would not allow him to pass altogether unnoticed. To be brief, I have
+been more fortunate than those hunters after Mercury who have sought
+the cunning god in the sun. I found him out, and saw him where no one
+else had hitherto seen him.” Since Gassendi’s time a number of transits
+have been observed.
+
+These crossings of the sun’s face, or “transits,” as they are called,
+have been important matters. The transit of Venus especially was once
+eagerly looked for by astronomers, since, by close observations of
+Venus’s movements and positions, the distance of the sun could at that
+time be better calculated than in any other way. Other methods are now
+coming into vogue.
+
+The transits of Venus are rare. Two come near together, separated by
+only eight years, and then for more than one hundred years the little
+dark body of Venus is never seen from earth to glide over the sun’s
+photosphere. There was a transit of Venus in the year 1761, and another
+in the year 1769. There was a transit of Venus in 1874, and another in
+1882. At the last transits it was found that the sun, instead of being
+ninety-five millions of miles away, as astronomers thought, was only
+ninety-three millions of miles away. The reason why these transits
+happen so seldom, is that the orbits of Mercury and Venus lie in rather
+a different plane or level from the earth’s orbit. So, like the moon,
+though often passing between us and the sun, they generally go just a
+little higher or just a little lower than his bright face.
+
+Mercury and Venus show phases like the moon, although they do not
+circle round the earth as the moon does. These “phases,” or changes of
+shape, are probably never visible except through a telescope. It will
+be easier to think about the phases of Venus alone, than to consider
+both together. Her orbit lies within the earth’s orbit, and the earth
+and Venus travel round the sun--as do all the planets--in the same
+direction. But as Venus’s pathway is shorter than ours, and as her
+speed is greater, she is much the quickest about her yearly journey,
+and she overtakes us again and again at different points of our orbit
+in turn.
+
+[Illustration: PHASES OF VENUS.]
+
+At one time she comes between us and the sun. That is her nearest
+position to us, and she is then only about twenty-five millions of
+miles distant. A beautiful sight she would be, but unfortunately her
+bright side is entirely turned away, and only her dark side is turned
+towards us. So then she is “new Venus,” and is invisible.
+
+At another time she is completely beyond the sun, and at her farthest
+position away from us. Her shining is quite lost in the sun’s rays
+coming between. And though we get a good view of her as “full Venus,”
+at a little to one side or the other, yet so great is her distance--as
+much as one hundred and fifty-seven millions of miles--that her size
+and brightness are very much lessened.
+
+Between these two nearest and farthest points, she occupies two middle
+distances, one on each side of the sun. Then, like the moon at her
+“quarters,” she turns to us only half of her bright side. But this
+is the best view of Venus that we have, as a brilliant, untwinkling,
+starlike form,--the Evening Star of ancients and of poets. Between
+these four leading positions Venus is always traveling gradually
+from one to another--always either waxing or waning in size and in
+brightness. Mercury passes through the same seeming changes.
+
+Inhabitants of Venus must have a glorious view of the earth, with her
+attendant moon. For just at the time when the two planets are nearest
+together, and when she is only “new Venus” to us, a dark and invisible
+body, the earth is “full earth” to Venus. The very best sight we ever
+have of Venus can not come near that sight. But if Mercury and Venus
+really are so often covered with heavy clouds as astronomers believe,
+this must greatly interfere with any habits of star-gazing.
+
+Venus and the earth have often been called twin-sister planets. There
+are many points of likeness between them. In size they differ little,
+and in length of day they are within an hour of being the same. Earth
+certainly has a companion-moon, and Venus, it is believed, has not. At
+one time several astronomers were pretty certain that they had caught
+glimpses of a moon; but the supposed moon has of late quite vanished,
+and nobody can say whether it ever really existed. Venus travels in
+an ellipse which comes nearer to being a circle than the orbit of any
+other planet.
+
+Mountain-shadows have been watched through the telescope, in Venus,
+as in the moon. Some astronomers have believed that they saw signs of
+very lofty mountains--as much as twenty-eight miles, or four times the
+height of our highest earthly mountains, but this requires confirmation.
+
+There is a good deal of uncertainty about the climate of Venus. The
+heat there must greatly surpass heat ever felt on earth--the sun being
+about double the apparent size of our sun, and pouring out nearly
+double the amount of light and heat that we receive.
+
+This difference may be met, as already stated, by a sheltering, cloudy
+atmosphere, or the inhabitants may have frames and eyesight suited to
+the increased glare and warmth.
+
+An atmosphere and water exist there as here. From what we have seen
+above of the rapid and violent seasons of this planet, we might think
+that the agitations of the winds, the rains, and the storms would
+surpass everything which we see and experience here, and that its
+atmosphere and its seas would be subject to a continual evaporation
+and precipitation in torrential rains--an hypothesis confirmed by its
+light, due, doubtless, to reflection from its upper clouds, and to the
+multiplicity of the clouds themselves. To judge by our own impressions,
+we should be much less pleased with this country than with our own, and
+it is even very probable that our physical organization, accommodating
+and complaisant as it is, could not become acclimatized to such
+variations of temperature. But it is not necessary to conclude from
+this that Venus is uninhabitable and uninhabited. We may even suppose,
+without exaggeration, that its inhabitants, organized to live in the
+midst of these conditions, find themselves at their ease, like a fish
+in water, and think that our earth is too monotonous and too cold to
+serve as an abode for active and intelligent beings.
+
+Of what nature are the inhabitants of Venus? Do they resemble us in
+physical form? Are they endowed with an intelligence analogous to
+ours? Do they pass their life in pleasure, as Bernardin de St. Pierre
+said; or, rather, are they so tormented by the inclemency of their
+seasons that they have no delicate perception, and are incapable of
+any scientific or artistic attention? These are interesting questions,
+to which we have no reply. All that we can say is, that organized
+life on Venus must be little different from terrestrial life, and
+that this world is one of those which resemble ours most. It should,
+then, be inhabited by vegetable, animal, and human races but little
+different from those which people our planet. As to imagining it desert
+or sterile--this is an hypothesis which could not arise in the brain
+of any naturalist. The action of the divine sun must be there, as in
+Mercury, still more fertile than his terrestrial work, already so
+wonderful. We may add that Venus and Mercury, having been formed after
+the earth, are relatively younger than our planet.
+
+It is believed also that the axis of Venus, instead of being slanted
+only as much as the earth’s axis, is tilted much more. Even if
+the tilting is less than some have supposed, it is probably very
+considerable. If Venus really does “lie over” in such a manner,
+certain startling changes of climate on its surface--unpleasant
+changes, according to our ideas--would take place.
+
+Like earth, Venus would have her two arctic regions, where a burning
+summer’s day would succeed a bitter winter’s night, each half a year in
+length. She would have also her tropical region--only in that region
+intense cold would alternate with intense heat, brief seasons of each
+in turn. And between the tropics and the arctic regions would lie wide
+belts, by turns entirely tropical and entirely arctic. The rapidity and
+severity of these changes, following one another in a year about as
+long as eight of our months, would seem to be too much for any human
+frame to endure. But it all rests upon an _if_. And we may be quite
+sure that _if_ there are any manner of human beings in Venus, their
+frames are well suited to the climate of their world.
+
+Though Mars is one of the inner group of four small planets, divided by
+the zone of asteroids from the outer group of four great planets, yet
+he belongs to the outside set of Superior Planets. His orbit surrounds
+ours, being at all points farther off from the sun. Very slight
+“phases” have been seen in Mars. He turns to us, from time to time,
+just enough of his dark side to prove that he _has_ a dark side, and
+that he does not shine like a star by his own light. But the phases on
+that planet are by no means marked as they are with Venus.
+
+Until lately it was believed that Mars possessed no moons. Two very
+small ones have, however, been lately found circling round him.[2]
+They have been named Deimos and Phobos, after the “sons of Mars” in
+Greek mythology. Deimos travels round Mars in thirty-nine hours, while
+Phobos performs the same journey in the astonishingly short period of
+seven hours and a half!
+
+[2] The discovery of the two moons is due to the agency of a woman.
+Professor Asaph Hall, of Washington City, was searching by the aid of
+the most powerful telescope which had yet been directed to Mars, and at
+the very moment when the planet was in the most favorable condition for
+observation. Having searched in vain during several evenings in August,
+1877, he was about to give up, when Mrs. Hall begged him to search a
+little more. He did so, and on the night of the 11th he discovered the
+first of the satellites, and then on the 17th the second.
+
+[Illustration: MARS AND THE PATH OF ITS SATELLITES.]
+
+We have here, then, a system very different from that of the earth
+and moon. But the most curious point is the rapidity with which the
+inner satellite of Mars revolves round its planet. This revolution
+is performed in seven hours, thirty-nine minutes, fifteen seconds,
+although the world of Mars rotates on itself in twenty-four hours,
+thirty-seven minutes--that is to say, this moon turns much more
+quickly than the planet itself. This fact is inconsistent with all the
+ideas we have had up to the present on the law of formation of the
+celestial bodies. Thus, while the sun appears to revolve in the Martian
+sky in a slow journey of more than twenty-four hours, the inner moon
+performs its entire revolution in a third of a day. It follows that
+_it rises in the west_ and _it sets in the east_! It passes the second
+moon, eclipses it from time to time, and goes through all its phases
+in eleven hours, each quarter not lasting even three hours. What a
+singular world!
+
+These satellites are quite small--they are the smallest celestial
+bodies we know. The brightness of the planet prevents us from measuring
+them exactly. It seems, however, that the nearer is the larger, and
+shows the brightness of a star of the tenth magnitude, and that the
+second shines as a star of the twelfth magnitude. According to the
+most trustworthy photometric measures, the first satellite may have a
+diameter of 7.45 miles, and the second a diameter of 6.2 miles. _The
+larger of these two worlds is scarcely larger than Paris._ Should we
+honor them with the title of worlds? They are not even terrestrial
+continents, nor empires, nor kingdoms, nor provinces, nor departments.
+Alexander, Cæsar, Charlemagne, or Napoleon, might care but little to
+receive the scepter of such worlds. Gulliver might juggle with them.
+Who knows, however? The vanity of men being generally in the direct
+ratio of their mediocrity, the microscopical reasoning mites which
+doubtless swarm on their surface have also, perhaps, permanent armies,
+which mutilate each other for the possession of a grain of sand.
+
+These two little moons received from their discoverer the names of
+_Deimos_ (Terror) and _Phobos_ (Flight), suggested by the two verses of
+Homer’s “Iliad” which represent Mars descending on the earth to avenge
+the death of his son Ascalaphus:
+
+  “He ordered Terror and Flight to yoke his steeds,
+  And he himself put on his glittering arms.”
+
+_Phobos_ is the name of the nearer satellite; _Deimos_, that of the
+more distant.
+
+The existence of these little globes had already been suspected from
+analogy, and thinkers had frequently suggested that, since the earth
+has one satellite, Mars should have two, Jupiter four, Saturn eight;
+and this is indeed the fact--though as Jupiter is now found to have
+_five_ satellites, this arithmetical progression is upset. But as we
+experience too often in practice the insufficiency of these reasonings
+of purely human logic, we can not give them more value than they
+really possess. We might suppose in the same way now that Uranus has
+sixteen satellites, and Neptune thirty-two. This is possible; but
+we know nothing of them, and have not even the right to consider
+this proportion as probable. It is not the less curious to read the
+following passage, written by Voltaire in 1750 in his masterpiece, the
+“Micromégas:”
+
+“On leaving Jupiter, our travelers crossed a space of about a hundred
+millions of leagues, and reached the planet Mars. They saw _two
+moons_, which wait on this planet, and which have escaped the gaze
+of astronomers. I know well that Father Castel wrote against the
+existence of these two moons; but I agree with those who reason from
+analogy. These good philosophers know how difficult it would be for
+Mars, which is so far from the sun, to get on with less than two moons.
+However this may be, our people found it so small that they feared they
+might not find anything to lie upon, and went on their way.”
+
+Here we have unquestionably a very clear prophecy, a rare quality
+in this kind of writing. The astronomico-philosophical romance of
+“Micromégas” has been considered as an imitation of Gulliver. Let us
+open the masterpiece of Swift himself, composed about 1720, and we
+read, word for word, in Chapter III of the “Voyage to Laputa:”
+
+“Certain astronomers ... spend the greatest part of their lives in
+observing the celestial bodies, which they do by the assistance of
+glasses far excelling ours in goodness. For this advantage hath enabled
+them to extend the discoveries much farther than our astronomers in
+Europe; for they have made a catalogue of ten thousand fixed stars,
+whereas the largest of ours do not contain above one-third part of that
+number. They have likewise discovered two lesser stars, or satellites,
+which revolve about Mars, whereof the innermost is distant from the
+center of the primary planet exactly three of his diameters, and the
+outermost five. The former revolves in the space of ten hours, and
+the latter in twenty-one and a half; so that the squares of their
+periodical times are very near in the same proportion with the cubes of
+their distance from the center of Mars, which evidently shows them to
+be governed by the same law of gravitation that influences the other
+heavenly bodies.”
+
+What are we to think of this double prediction of the two satellites of
+Mars? Indeed, the prophecies which have been made so much of in certain
+doctrinal arguments have not always been as clear, nor the coincidences
+so striking. However, it is evident that no one had ever seen these
+satellites before 1877, and that there was in this hit merely the
+capricious work of chance. We may even remark that both the English and
+French authors have only spoken ironically against the mathematicians,
+and that in 1610, Kepler, on receiving the news of the discovery of the
+satellites of Jupiter, wrote to his friend Wachenfals that “not only
+the existence of these satellites appeared to him probable, but that
+doubtless there might yet be found two to Mars, six or eight to Saturn,
+and perhaps one to Venus and Mercury.” We can not, assuredly, help
+noticing that reasoning from analogy is here found on the right road.
+However this may be, this discovery truly constitutes one of the most
+interesting facts of contemporary astronomy.
+
+Mars is not only much smaller than the earth, but a good deal less
+dense in his “make.” His material is only about three-quarters as heavy
+as an equal amount of the earth’s material. A very heavy man on earth
+would be a most light and active individual on Mars. Gold taken from
+earth to Mars would weigh there no more than tin weighs upon earth.
+
+Mars has, it seems, an atmosphere, even as earth has. Of all the
+planets Mars, is the only one whose actual surface is discernible in
+the telescope. Mercury and Venus are so hidden by dense envelopes of
+clouds that the real planets within are only now and then to be dimly
+caught sight of. Jupiter and Saturn are so completely enwrapped in
+mighty masses of vapor, that we can not even be certain whether there
+are any solid bodies at all inside.
+
+But Mars can be studied. Here and there, it is true, clouds sweep over
+the landscape, hiding from view for a little while one continent or
+another, one sea or another, growing, changing, melting away, as do
+the clouds of earth. Still, though these clouds come and go, there are
+other markings on the surface of Mars which do not change. Or, rather,
+they only change so much as the continents and oceans of earth would
+seem to vary, if watched from another planet, as the daily movement of
+earth carried them from west to east, or as they might be hidden for
+a while by cloud-layers coming between. It has been curiously noted
+that these clouds over Mars form often in the morning and evening, and
+are afterwards dispersed by the heat of midday. Also there seems every
+reason to believe that rainfalls take place in Mars as upon earth.
+
+The red color of Mars is well known. This does not vanish in the
+telescope, but it is found that parts only have the red or orange
+hue, while other parts are dark and greenish. These are the markings
+which remain always the same, and they have been so closely examined
+that more is known about the geography of Mars than of any other world
+outside our own.
+
+Mars, at his nearest point, does not draw closer to us than forty
+millions of miles. At such a distance one must not speak too
+confidently. There are, however, many reasons for believing that the
+red portions are continents and that the green portions are oceans.
+
+The spectroscope has lately shown us that water does really exist in
+the atmosphere of Mars--unlike the dreary, waterless moon. So we no
+longer doubt that the cloudlike appearances are clouds, and that rain
+sometimes falls on Mars. If there is rain, and if there are clouds and
+vapor, there are probably oceans also.
+
+Two singular white spots are to be seen at the north and south poles,
+which we believe to be polar ice and snow. Somebody looking at our
+earth in like manner from a distance, would doubtless perceive two
+such white snow-spots. These two polar caps are seen to vary with the
+seasons. When the north pole of Mars is turned towards the sun, the
+white spot there grows smaller; and at the same time, the south pole of
+Mars being turned away from the sun, the white spot there grows larger.
+Again, when the south pole is towards the sun, and the north pole away
+from the sun, the white spot at the south is seen to be the smallest,
+and the white spot at the north is seen to be the largest. This is
+exactly what takes place in the summers and winters of our north and
+south poles.
+
+The markings of Mars have been so carefully studied, that at last a map
+has been made of the planet--a map of a world, never less than forty
+millions of miles away! Names have been given to the continents and
+oceans--such as Dawes Continent, Herschel Continent, De La Rue Ocean,
+Airy Sea, Huggins Inlet, and so on.
+
+Land and water seem to be very differently arranged on Mars from what
+they are on earth. Here we have about three times as much water as
+land, and to get from one continent to another without crossing the
+sea is in some cases impossible. But a traveler there might go most
+conveniently to and fro, hither and thither, to all parts of his world,
+either on land or on water, without any change. If he preferred water,
+he would never need to set foot on land; and if he preferred land, he
+would never need to enter a boat. The two are so curiously mingled
+together, narrow necks of land running side by side with long, narrow
+sea-inlets, that Atlantic and Pacific Oceans are unknown.
+
+Some have wondered whether the reddish color of the land may be caused
+by grass and trees being red instead of green. Very strange if so it
+were. But in that case, no doubt the inhabitants of Mars would find
+green just as trying to their eyesight, as we should find red trying to
+ours.
+
+
+
+
+CHAPTER XVII.
+
+JUPITER.
+
+
+Passing at one leap over the belt of tiny asteroids, about which we
+know little beyond their general movement, and the size and weight of
+a few among them, we reach at once the giant planet Jupiter: Mighty
+Jupiter, hurrying ever onward, with a speed, not indeed equal to that
+of Mercury or of our earth, yet eighty times as rapid as the speed of
+a cannon-ball! Think of a huge body, equal in bulk to twelve hundred
+earths, equal in weight to three hundred earths, rushing ceaselessly
+through space, at the rate of seven hundred thousand miles a day!
+
+Jupiter’s shape is greatly flattened at the poles. He spins rapidly on
+his axis, once in nearly ten hours, and has therefore a five hours’
+day and a five hours’ night. As the slope of his axis is exceedingly
+slight, he can boast little or no changes of season. The climate near
+the poles has never much of the sun’s heat. In fact, all the year round
+the sun must shine upon Jupiter much as he shines on the earth at the
+equinoxes.
+
+But the amount of light and heat received by Jupiter from the sun is
+only about one twenty-fifth part of that which we receive on earth; and
+the sun, as seen from Jupiter, can have but a small, round surface, not
+even one-quarter the diameter of the sun we see in the sky.
+
+When looked at with magnifying power, the bright, starlike Jupiter
+grows into a broad, softly-shining disk or plate, with flattened top
+and bottom, and five tiny, bright moons close at hand. Sometimes one
+moon is on one side, and four are on the other; sometimes two are one
+side and three on the other; sometimes one or more are either hidden
+behind Jupiter or passing in front of him. Jupiter has also curious
+markings on his surface, visible through a telescope. These markings
+often undergo changes; for Jupiter is no chill, fixed, dead world, such
+as the moon seems to be.
+
+[Illustration: GENERAL ASPECT OF JUPITER--SATELLITE AND ITS SHADOW.]
+
+There are dark belts and bright belts, usually running in a line with
+the equator, from east to west. Across the regions of the equator lies
+commonly a band of pearly white, with a dark band on either side of
+“coppery, ruddy, or even purplish” hue. Light and dark belts follow one
+after another, up to the north pole and down to the south pole.
+
+When we talk of “north and south poles” in the other planets, we merely
+mean those poles which point towards those portions of the starry
+heavens which we have chosen to call “northern” and “southern.” You
+know that all the chief planets travel round the sun in very nearly the
+same _plane_ or flat surface that we do ourselves. That plane is called
+the “plane of the ecliptic.” Suppose that you had an enormous sheet of
+cardboard, and that in the middle of this cardboard the sun were fixed,
+half his body being above and half below. At a little distance, fixed
+in like manner in the card, would be the small body of the earth, half
+above and half below, her axis being in a slanting position. The piece
+of cardboard represents what is called in the heavens the _plane of
+the ecliptic_--an imaginary flat surface, cutting exactly through the
+middle of the sun and of the earth.
+
+If the planets all traveled in the same precise plane, they would
+all be fixed in the cardboard just like the earth, half the body of
+each above and half below. As they do not so travel, some would have
+to be placed a little higher, some a little lower, according to what
+part of their orbits they were on. This supposed cardboard “plane of
+the ecliptic” would divide the heavens into two halves. One half,
+containing the constellations of the Great Bear, the Little Bear,
+Cepheus, Draco, and others, would be called the Northern Heavens. One
+end of the earth’s axis, pointing just now nearly to the Polar Star,
+we name the North Pole; and all poles of planets pointing towards this
+northern half of the heavens, are in like manner named by us their
+north poles.
+
+With regard to west and east, lay in imagination upon this cardboard
+plane a watch, with its face upwards; remembering that all the planets
+and nearly all the moons of the Solar System are said both to spin on
+their axes, and to travel in their orbits round the sun, _from west to
+east_. Note how the hands of your watch would move in such a position.
+The “west to east” motions of planets and moons would be in exactly the
+opposite direction from what the motions of the watch-hands would be.
+
+To return to Jupiter. It is believed that these bands of color are
+owing to a heavy, dense atmosphere, loaded with vast masses of cloudy
+vapor. By the “size” of Jupiter, we really mean the size of this
+outside envelope of clouds. How large the solid body within may be,
+or whether there is any such solid body at all, we do not know. The
+extreme lightness of Jupiter, as compared with his great size, has
+caused strong doubts on this head.
+
+The white belts are supposed to be the outer side of cloud-masses
+shining in the sunlight. Travelers in the Alps have seen such
+cloud-masses, spreading over the whole country beneath their feet,
+white as driven snow, and shining in the sunbeams which they were
+hiding from villages below; or looking like soft masses of cotton-wool,
+from which the mountain-peaks rose sharply here and there.
+
+The dark spaces between seem to be rifts or breaks in the clouds.
+Whether, when we look at those dark spaces, we are looking at the
+body of Jupiter, or only at lower layers of clouds, is not known.
+But sometimes blacker spots show upon the dark cloud-belts, and this
+seems rather as if they were only lower layers of clouds, the black
+spots giving us peeps down into still lower and deeper layers, or else
+perhaps to the planet itself. These appearances remind one strongly of
+the sun-spots, each with its penumbra, umbra, and nucleus. Occasionally
+bright white spots show, instead of dark ones. It is thought that they
+may be caused by a violent upward rush of dense clouds of white vapor.
+The white spots again recall the sun and his _faculæ_.
+
+Jupiter’s bands are not fixed. Great changes go on constantly among
+them. Sometimes a white band will turn dark-colored, or a dark band
+will turn white. Sometimes few and sometimes many belts are to be seen.
+Sometimes a dark belt will lie slanting across the others, nearly from
+north to south. Once, in a single hour, an entirely new belt was seen
+to come into shape. Another time, two whole belts vanished in one day.
+The bands, in which such rapid movements are seen, are often thousands
+of miles in breadth. Sometimes these wide zones of clouds will remain
+for weeks the same. At another time a break or rift in them will be
+seen to journey swiftly over the surface of the planet.
+
+The winds on earth are often destructive. A hurricane, moving at the
+rate of ninety miles an hour, will carry away whole buildings and level
+entire plantations. Such hurricanes rarely, if ever, last more than
+a few hours. But winds in Jupiter, judging from the movements of the
+clouds, often travel at the rate of one hundred and fifty miles an
+hour; and that, not for hours only, but for many weeks together. What
+manner of living beings could stand such weather may well be questioned.
+
+Another difficulty which arises is as to the cause of these tremendous
+disturbances on Jupiter. Our earthly storms are brought about by the
+heat of the sun acting on our atmosphere. But the sun-heat which
+reaches Jupiter seems very far from enough to raise such vast clouds of
+vapor, and to bring about such prolonged and tremendous hurricanes of
+wind.
+
+What if there is another cause? What if Jupiter is _not_ a cooled
+body like our earth, but a liquid, seething, bubbling mass of fiery
+heat--just as we believe our earth was once upon a time, in long past
+ages, before her outside crust became cold enough for men and animals
+to live thereon? _Then_, indeed, we could understand how, instead
+of oceans lying on his surface, all the water of Jupiter would be
+driven aloft to hang in masses of steam or be condensed into vast
+cloud-layers. _Then_ we could understand why a perpetual stir of
+rushing winds should disturb the planet’s atmosphere.
+
+In that case would Jupiter be a planet at all? Certainly--in the sense
+of obeying the sun’s control. Our earth was once, we believe, a globe
+of melted matter, glowing with heat--and farther back still, possibly,
+a globe of gas. Some people are very positive about these past changes;
+but it is wise not to be over-positive where we can not know to a
+certainty what has taken place. However, Jupiter _may_ have cooled down
+only to the liquid state, and if he goes on cooling he may, by and by,
+gain a solid crust like the earth.
+
+This idea about Jupiter’s hot and molten state belongs quite to late
+years. Certain other matters seem to bear it out, though of actual
+proof we have none. It is thought, for instance, that the dull, coppery
+red light, showing often in the dark bands, may be a red glow from the
+heated body within. Also it has been calculated that Jupiter gives out
+much more light than our earth would do, if increased to his size and
+moved to his place--more, in fact, than we could reasonably expect him
+to give out. If so, whence does he obtain the extra brightness? If he
+does not shine by reflected light alone, he probably shines also in
+some additional degree by his own light.
+
+But what about Jupiter being inhabited? Would it in such a case be
+quite impossible? “Impossible” is not a word for us to use about
+matters where we are ignorant. We can only say that it is impossible
+for us to _imagine_ any kind of living creatures finding a home there,
+if our present notions about the present state of Jupiter are correct.
+Then is the chief planet of the Solar System a huge, useless monument
+of God’s power to create? Not so fast. Even as merely such a monument,
+he could not be useless. And even if he were put to no present use at
+all, it might be merely because this is a time of preparation for the
+future. God has his times of long and slow preparation, alike with
+worlds, with nations, and with individuals.
+
+But now as to the five moons circling round Jupiter. There used to be
+some very pretty ideas afloat about the wonderful beauty of the moons,
+as seen from Jupiter, their united brilliancy so far surpassing the
+shining of our one poor satellite, and making up for the dim light of
+Jupiter’s sun.
+
+A certain little difficulty was not quite enough considered. If
+anybody were living on the surface of Jupiter, he would have, one is
+inclined to think, small chance of often seeing the moons through the
+cloud-laden atmosphere.
+
+[Illustration: SATELLITES OF JUPITER COMPARED WITH THE EARTH AND MOON.]
+
+The nearest of the four larger moons to Jupiter would, it is true,
+appear--when visible at all--rather bigger than ours does to us; while
+the two next would be almost half as large, and the farthest about a
+quarter as large--supposing inhabitants of Jupiter to have our powers
+of vision.
+
+All taken together they would cover a considerably larger space in the
+sky than does our moon. But it must be remembered that Jupiter’s moons,
+like ours, shine merely by reflected sunlight. And so dim is the
+sunshine at that distance compared with what it is at our distance,
+that all the five moons together, even if full at the same time, could
+only give about one-sixteenth part of the light which we obtain from
+our one full moon.
+
+Besides, they never are full together, seen from any one part of
+Jupiter. The four inner moons are never to be seen “full” at all; for
+just when they might be so, they are eclipsed or shaded by Jupiter’s
+shadow. The fourth sometimes escapes this eclipse, from being so much
+farther away.
+
+A thought has been lately put forward, which may or may not have truth
+in it. What if--instead of Jupiter being a world, inhabited by animals
+and people, as is often supposed, with a small distant sun and five dim
+moons to give them light--what if Jupiter is himself in some sort a
+second sun to his moons, and what if those “moons” are really inhabited
+planets? It may be so. That is all we can say. The idea is not an
+impossible one.
+
+The so-called “moons” are certainly small. But they are by no means
+too small for such a purpose. Jupiter would in that case, with his
+five moons circling round him, enjoying his light and warmth, be a
+small picture of the sun, with his four inner planets and the asteroids
+circling round him, basking in a more lavish amount of the same.
+
+Picturing the moons as giving light to Jupiter, we find them seemingly
+dim and weak for such a purpose--though, of course, we may here make a
+grand mistake in supposing the eyesight of living creatures in Jupiter
+to be no better than our own eyesight. Even upon earth a cat can see
+plainly where a man has to grope his way in darkness.
+
+But by picturing the moons as inhabited, and Jupiter as giving out some
+measure of heat and light to make up for the lessened amount of light
+and heat received from the sun, the matter becomes more easy to our
+understanding.
+
+[Illustration: THE SYSTEM OF JUPITER.]
+
+The nearest moon has indeed a magnificent view of Jupiter as a huge
+bright disk in its sky, no less than three thousand times as large
+as our moon appears to us, shining brightly with reflected sunlight,
+and it may be glowing with a red light of his own in addition. Even
+the farthest off of the five sees him with a face sixty-five times
+the size of our moon. And the varying colors and stormy changes in
+the cloud-belts, viewed thus near at hand, must afford marvelously
+beautiful effects.
+
+Just as Mercury, Venus, Earth, and Mars travel round the sun, at
+different distances, nearly in the same plane, so Jupiter’s five moons
+travel round him, at different distances, nearly in the same plane.
+Jupiter’s moons are always to be seen in a line, not one high and
+another low, one near his pole and another near his equator.
+
+The moon nearest to Jupiter, discovered in September, 1892, by
+Professor Barnard, now of the Yerkes Observatory of the Chicago
+University, has a probable diameter of one hundred miles, and revolves
+round its primary in about twelve hours. The second satellite, named
+Io, is said to be over two thousand miles in diameter, travels round
+Jupiter in less than two of our days, and is eclipsed by Jupiter’s
+shadow once in every forty-two hours.
+
+The third moon, Europa, is rather smaller, takes over three days to its
+journey, and suffers eclipse once in every eighty-five hours.
+
+The fourth moon, Ganymede, is believed to be considerably larger than
+Mercury, journeys round Jupiter once a week, and is eclipsed once every
+hundred and seventy-one hours.
+
+The fifth moon, Callisto, is also said to be slightly larger than
+Mercury, performs its journey in something more than sixteen days, and
+from its greater distance suffers eclipse less often than the other
+four.
+
+The distance of the nearest is more than one hundred thousand miles
+from Jupiter; that of the farthest, more than one million miles.
+
+The following table presents more minutely the results of the latest
+discoveries concerning these satellites:
+
+  +-----------------------+----------------+------------+-----------+
+  |                       | DISTANCE FROM  |            | PERIOD OF |
+  |      SATELLITES.      |   CENTER OF    | DIAMETER.  |REVOLUTION.|
+  |                       |   JUPITER.     |            |           |
+  +-----------------------+----------------+------------+-----------+
+  |                       |                |            |D. H. M. S.|
+  |1. Barnard’s Satellite,|  112,500 miles.|  100 miles.|   11 57 23|
+  |2. Io,                 |  266,000   ”   |2,356   ”   | 1 18 27 33|
+  |3. Europa,             |  424,000   ”   |2,046   ”   | 3 13 13 42|
+  |4. Ganymede,           |  676,000   ”   |3,596   ”   | 7  3 42 33|
+  |5. Callisto,           |1,189,000   ”   |2,728   ”   |16 15 32 11|
+  +-----------------------+----------------+------------+-----------+
+
+The fact of these eclipses, and of the shadow thrown by Jupiter’s body,
+shows plainly that though he may give out some measure of light, as has
+been suggested, yet that light can not be strong, or it would prevent
+any shadow from being thrown by the sunlight. Also, the dense masses
+of cloud around him, though reflecting sunlight brightly, would shut
+in much of his own light. Possibly it is chiefly as heat-giver and as
+sunlight-reflector that Jupiter serves his five satellites.
+
+As with our own moon, so with Jupiter’s moons, the real center of
+their orbit is the sun, and not Jupiter. They accompany Jupiter in his
+journey, controlled by the sun, and immensely influenced by Jupiter.
+
+At night the spectacle of the sky seen from Jupiter is, with reference
+to the constellations, the same as that which we see from the earth.
+There, as here, shine Orion, the Great Bear, Pegasus, Andromeda,
+Gemini, and all the other constellations, as well as the diamonds of
+our sky: Sirius, Vega, Capella, Procyon, Rigel, and their rivals. The
+390,000,000 of miles which separate us from Jupiter _in no way_ alter
+the celestial perspectives. But the most curious character of this sky
+is unquestionably the spectacle of the five moons, each of which shows
+a different motion. The second moves in the firmament with an enormous
+velocity, and Barnard’s satellite still faster, and produce almost
+every day total eclipses of the sun in the equatorial regions. The four
+inner moons are eclipsed at each revolution, just at the hours when
+they are at their “full.” The fifth alone attains the full phase.
+
+Contrary to the generally received opinion, these bodies do not give to
+Jupiter all the light which is supposed. We might think, in fact, as
+has been so often stated, that these five moons illuminate the nights
+five times better relatively than our single moon does in this respect,
+and that they supplement in some measure the feebleness of the light
+received from the sun. This result would be, assuredly, very agreeable,
+but nature has not so arranged it. The five satellites cover, it is
+true, an area of the sky greater than our moon, but they reflect the
+light of a sun twenty-seven times smaller than ours; indeed, the total
+light reflected is only equal to a sixteenth of that of our full moon,
+even supposing the soil of these satellites to be as white as it
+appears to be, especially the fifth satellite.
+
+Jupiter appears to be a world still in process of formation, which
+lately--some thousands of centuries ago--served as a sun to his
+own system of five or perhaps more worlds. If the central body is
+not at present inhabited, his satellites may be. In this case, the
+magnificence of the spectacle presented by Jupiter himself to the
+inhabitants of the satellites is worthy of our attention. Seen from
+Barnard’s satellite, Jupiter’s disk has a diameter of 47°, or more than
+half the distance from the horizon to the zenith. Seen from the second
+satellite, the Jovian globe presents an immense disk of twenty degrees
+in diameter, or 1,400 times larger than the full moon! What a body!
+What a picture, with its belts, its cloud motions, and its glowing
+coloration, seen from so near! What a nocturnal sun!--still warm,
+perhaps. Add to this the aspect of the satellites themselves seen from
+each other, and you have a spectacle of which no terrestrial night can
+give an idea.
+
+Such is the world of Jupiter from the double point of view of its vital
+organization and of the spectacle of external nature, seen from this
+immense observatory.
+
+The attraction of the planets has always played an important part
+in the motion of comets and the form of their orbits. The enormous
+size of Jupiter gives it more influence than any other planet, and we
+are not surprised that it should have seriously interfered with some
+of the comets that belong to the Solar System. We have already seen
+that Biela’s comet was captured by Jupiter, and that it was probably
+dissolved into meteoric dust. We show in the cut the orbits of eight
+others that circle around the sun, but retreat no farther away than
+Jupiter. These are the orbits as now determined, but they vary from
+age to age on account of disturbances of other planets. But it is not
+likely that the comets themselves will ever escape from the control of
+Jupiter.
+
+[Illustration: ORBITS OF NINE COMETS CAPTURED BY JUPITER.]
+
+
+
+
+CHAPTER XVIII.
+
+SATURN.
+
+
+The system of Jupiter is a simple system compared with that of Saturn,
+next in order. For whereas Jupiter has only five moons, Saturn has
+eight, and, in addition to these, he has three wonderful rings. Neither
+rings nor moons can be seen without a telescope, on account of Saturn’s
+great distance from us--more than three thousand times the distance of
+the moon, or upwards of eight hundred millions of miles. Saturn’s mean
+distance from the sun is eight hundred and seventy-six million seven
+hundred and sixty-seven thousand miles.
+
+Saturn does not equal his mighty brother Jupiter in size, though he
+comes near enough in this respect to be called often his “twin”--just
+as that small pair of worlds, Venus and Earth, are called “twins.”
+While Jupiter is equal in size to over one thousand two hundred earths,
+Saturn is equal to about seven hundred earths. And while Jupiter is
+equal in weight to three hundred earths, Saturn is only equal in weight
+to ninety earths. He appears to be made of very light materials--not
+more than three-quarters as dense as water. This would show the present
+state of Saturn to be very different from the present state of the
+earth. We are under the same uncertainty in speaking of Saturn as in
+speaking of Jupiter. Like Jupiter, Saturn is covered with dense masses
+of varying clouds, occasionally opening and allowing the astronomer
+peeps into lower cloud-levels; but rarely or never permitting the
+actual body of the planet to be seen.
+
+The same perplexities also come in here, to be answered much in the
+same manner. We should certainly expect that in a vast globe like
+Saturn the strong force of attraction would bind the whole into a
+dense solid mass; instead of which, Saturn is about the least solid of
+all the planets. He seems to be made up of a light, watery substance,
+surrounded by vapor.
+
+[Illustration: SATURN AND THE EARTH--COMPARATIVE SIZE.]
+
+One explanation can be offered. What if the globe of Saturn be still
+in a red-hot, molten state, keeping such water as would otherwise lie
+in oceans on his surface, floating aloft in masses of steam, the outer
+parts of which condense into clouds?
+
+No one supposes that Jupiter and Saturn are in the same condition
+of fierce and tempestuous heat as the sun. They may have been so
+once, but they must now have cooled down very many stages from that
+condition. Though no longer, however, a mass of far-reaching flames and
+fiery cyclones, the body of each may have only so far cooled as to have
+reached a stage of glowing molten red-heat, keeping all water in the
+form of vapor, and sending up strong rushes of burning air to cause the
+hurricanes which sweep to and fro the vast cloud-masses overhead.
+
+And if this be the case, then, with Saturn as with Jupiter, comes the
+question, Can Saturn be inhabited? And if--though we may not say it is
+impossible, yet we feel it to be utterly unlikely--then again follows
+the question, What if Saturn’s _moons_ are inhabited?
+
+Telescopic observations tempt us to believe that there is on this
+planet a quantity of heat greater than that which results from its
+distance from the sun; for the day-star as seen from Saturn is, as we
+have said, ninety times smaller in surface, and its heat and light
+are reduced in the same proportion. Water could only exist in the
+solid state of ice, and the vapor of water could not be produced so
+as to form clouds similar to ours. Now, meteorological variations are
+observed similar to those which we have noticed on Jupiter, but less
+intense. Facts, then, combine with theory to show us that the world of
+Saturn is at a temperature at least as high as ours, if not higher.
+
+But the strangest feature of the Saturnian calendar is, unquestionably,
+its being complicated, not only with the fabulous number of 25,060
+days in a year, but, further, with eight different kinds of months, of
+which the length varies from 22 hours to 79 days--that is to say, from
+about two Saturnian days to 167. It is as if we had here _eight moons
+revolving in eight different periods_.
+
+The inhabitants of such a world must assuredly differ strangely
+from us from all points of view. The specific lightness of the
+Saturnian substances and the density of the atmosphere will have
+conducted the vital organization in an extra-terrestrial direction,
+and the manifestations of life will be produced and developed under
+unimaginable forms. To suppose that there is nothing fixed, that the
+planet itself is but a skeleton, that the surface is liquid, that the
+living beings are gelatinous--in a word, that all is unstable--would be
+to surpass the limits of scientific induction.
+
+The diameter of the largest moon is about half the diameter of the
+earth, or much larger than Mercury. The four inner satellites are
+all nearer to Saturn than our moon to us, though the most distant of
+the eight is ten times as far away. The inner moon takes less than
+twenty-three hours to travel round Saturn, and the outer one over
+seventy-nine days.
+
+A great many charming descriptions have been worked up, with Saturn
+as with Jupiter, respecting the magnificent appearance of the eight
+radiant moons, joined to the glorious shining of the rings, as quite
+making up for the diminished light and heat of the sun. But here again
+comes in the doubt, whether really it is the moons who make up to
+Saturn for lack of light, or whether it is Saturn who makes up to the
+moons for lack of light.
+
+Certainly, Saturn’s cloudy covering would a little interfere with
+observations of the moons by any inhabitants of the solid body
+within--supposing there be any solid body at all. And though it sounds
+very wonderful to have eight moons instead of one moon, yet all the
+eight together give Saturn only a very small part of the light which we
+receive from our one full moon--so much more dimly does the sun light
+them up at that enormous distance.
+
+The same thing has been noticed with Saturn as with Jupiter--that he
+seems to shine more brightly than is to be expected in his position,
+from mere reflection of the sun’s rays. A glowing body within, sending
+a certain amount of added light through or between the masses of
+clouds, would explain away this difficulty.
+
+One more possible proof of Saturn’s half-liquid state is to be found
+in his occasional very odd changes of shape. Astronomers have been
+startled by a peculiar bulging out on one side, taking off from his
+roundness, and giving a square-shouldered aspect. We may not say it
+is quite impossible that a solid globe should undergo such tremendous
+upheavals and outbursts as to raise a great portion of its surface five
+or six hundred miles above the usual level--the change being visible
+at a distance of eight hundred millions of miles. But it would be
+easier to understand the possibility of such an event, in the case of a
+liquid, seething mass, than in the case of a solid ball.
+
+On the other hand this alteration of outline may be caused simply by
+a great upheaval not of the planet’s surface, but of the overhanging
+layers of clouds. Some such changes, only much slighter, have been
+remarked in Jupiter.
+
+And now as to the rings. Nothing like them is to be seen elsewhere in
+the Solar System. They are believed to be three in number; though some
+would divide them into more than three. Passing completely round the
+whole body of Saturn, they rise, one beyond another, to a height of
+many thousands of miles.
+
+The inner edge of the inner ring--an edge perhaps one hundred miles in
+thickness--is more than ten thousand miles from the surface of Saturn
+or more strictly speaking, from the outer surface of Saturn’s cloudy
+envelope. A man standing exactly on the equator and looking up, even if
+no clouds came between, would scarcely be able to see such a slender
+dark line at such a height.
+
+This dark, transparent ring, described sometimes as dusky, sometimes as
+richly purple, rises upwards to a height or breadth of nine thousand
+miles. Closely following it is a ring more brilliant than Saturn
+himself, over eighteen thousand miles in breadth. When astronomers talk
+of the “breadth” of these rings, it must be understood that they mean
+the width of the band measured _upwards_, in a direction away from the
+planet.
+
+Beyond the broad, bright ring is a gap of about one thousand seven
+hundred miles. Then follows the third ring, ten thousand miles in
+breadth; its outermost edge being at a height of more than forty-eight
+thousand miles from Saturn. The color of the third ring is grayish,
+much like the gray markings often seen on Saturn.
+
+What would not be our admiration, our astonishment, our stupor perhaps,
+if it were granted us to be transported there alive, and, among all
+these extra-terrestrial spectacles, to contemplate the strange aspect
+of the rings, which stretch across the sky like a bridge suspended
+in the heights of the firmament! Suppose we lived on the Saturnian
+equator itself, these rings would appear to us as a thin line drawn
+across the sky above our heads, and passing exactly through the zenith,
+rising from the east and increasing in width, then descending to the
+west and diminishing according to perspective. Only there have we
+the rings precisely in the zenith. The traveler who journeys from
+the equator towards either pole leaves the plane of the rings, and
+these sink imperceptibly, at the same time that the two extremities
+cease to appear diametrically opposite, and by degrees approach each
+other. What an amazing effect would be produced by this gigantic
+arch, which springs from the horizon and spans the sky! The celestial
+arch diminishes in height as we approach the pole. When we reach the
+sixty-third degree of latitude the summit of the arch has descended to
+the level of our horizon and the marvelous system disappears from the
+sky; so that the inhabitants of those regions know nothing of it, and
+find themselves in a less favorable position to study their own world
+than we, who are nearly 800,000,000 miles distant.
+
+During one-half of the Saturnian year the rings afford an admirable
+moonlight on one hemisphere of the planet, and during the other half
+they illuminate the other hemisphere; but there is always a half-year
+without “ringlight,” since the sun illuminates but one face at a time.
+Notwithstanding their volume and number, the satellites do not give
+as much nocturnal light as might be supposed; for they receive, on an
+equal surface, only the ninetieth part of the solar light which our
+moon receives. All the Saturnian satellites which can be at the same
+time above the horizon and as near as possible to the full phase do not
+afford more than the hundredth part of our lunar light. But the result
+may be nearly the same, for the optic nerve of the Saturnians may be
+ninety times more sensitive than ours.
+
+But there are further strange features in this system. The rings are
+so wide that their shadow extends over the greater part of the mean
+latitudes. During fifteen years the sun is to the south of the rings,
+and for fifteen years it is to the north. The countries of Saturn’s
+world which have the latitude of Paris endure this shadow for more than
+five years. At the equator the eclipse is shorter, and is only renewed
+every fifteen years; but there are every night, so to say, eclipses of
+the Saturnian moons by the rings and by themselves. In the circumpolar
+regions the day-star is never eclipsed by the rings; but the satellites
+revolve in a spiral, describing fantastic rounds, and the sun himself
+disappears at the pole during a long night of fifteen years.
+
+At one time it was supposed that the rings were solid, but they are now
+believed to consist of countless myriads of meteorites, each whirling
+in its own appointed pathway round the monster planet.
+
+[Illustration: IDEAL VIEW OF SATURN’S RINGS AND SATELLITES FROM THE
+PLANET.]
+
+As already said--leaving out of the question the cloudy atmosphere--a
+man standing on the equator would see nothing of the rings. A man
+standing at the north pole or the south pole of Saturn could see
+nothing either, since the rings would all lie below his horizon. But
+if he traveled southward from the north pole, or northward from the
+south pole, towards the equator, he would in time see the ringed arch
+appearing above the horizon, rising higher and growing wider with every
+mile of his journey; and when he was in a position to view the whole
+broad expanse, the transparent half-dark belt below, the wide radiant
+band rising upwards over that, and the grayish border surmounting all,
+he would truly have a magnificent spectacle before him.
+
+This magnificent spectacle is, however, by no means always visible,
+even from those parts of Saturn where alone it ever can be seen. The
+rings shine merely by reflected sunlight. Necessarily, therefore, while
+the sunbeams make one side bright the other side is dark; and not only
+this, but the rings throw broad and heavy shadows upon Saturn in the
+direction away from the sunlight.
+
+In the daytime they probably give out a faint shining, something like
+our own moon when seen in sunlight. During the summer nights they
+shine, no doubt, very beautifully. During the winter nights it so
+happens that their bright side is turned away; and not only that, but
+during the winter days the rings, while giving no light themselves to
+the wintry hemisphere of Saturn, completely hide the sun.
+
+When it is remembered that Saturn’s winter--that is, the winter of each
+hemisphere in turn--lasts during fifteen of our years; and when we hear
+of total eclipses of the sun lasting unbroken through eight years of
+such a winter, with not even bright rings to make up for his absence,
+we can not think of Saturn as a tempting residence. The sun gives
+Saturn at his best only about one-ninetieth of the heat and light that
+he gives to our earth; but to be deprived of even that little for eight
+years at a time, does indeed sound somewhat melancholy.
+
+Looking now at the other side of the question, the possible inhabitants
+of the moons, especially those near at hand, would have splendid views
+of Saturn and his rings in all their varying phases. For Saturn is a
+beautiful globe, wrapped in his changeful envelope of clouds, which,
+seen through a telescope, are lit up often with rainbow tints of blue
+and gold; a creamy white belt lying usually on the equator; while
+around extend the purple and shining and gray rings, sometimes rivaling
+in bright colors Saturn himself.
+
+We are compelled to assume that the continuous appearance of the rings
+is not due to real continuity of substance, but that they are composed
+of flights of disconnected satellites, so small and so closely packed
+that, at the immense distance to which Saturn is removed, they appear
+to form a continuous mass. There are analogous instances in the Solar
+System. In the zone of asteroids we have an undoubted instance of a
+flight of disconnected bodies traveling in a ring about a central
+attracting mass. The existence of zones of meteorites traveling around
+the sun has long been accepted as the only probable explanation of the
+periodic returns of meteoric showers. Again, the singular phenomenon
+called the Zodiacal Light is, in all probability, caused by a ring of
+minute cosmical bodies surrounding the sun. In the Milky Way and in
+the ring-nebulæ we have other illustrations of similar arrangements
+in nature, belonging, however, to orders immeasurably vaster than any
+within the Solar System.
+
+The moons of Saturn do not, like those of Jupiter, travel in one plane.
+
+
+
+
+CHAPTER XIX.
+
+URANUS AND NEPTUNE.
+
+
+Till the year 1781, Saturn was believed to be the outermost planet
+of the Solar System, and nobody suspected the fact of two great,
+lonely brother-planets wandering around the same sun at vast distances
+beyond,--Uranus, nine hundred millions of miles from Saturn; Neptune,
+nine hundred millions of miles from Uranus. No wonder they remained
+long undiscovered.
+
+Uranus can sometimes be seen by the unaided eye as a dim star of the
+sixth magnitude. And when he was known for a planet, it was found that
+he _had_ been often so seen and noted. Again and again he had been
+taken for a fixed star, and as he moved on, disappearing from that
+particular spot, it was supposed that the star had vanished.
+
+One night, March 13, 1781, when William Herschel was busily exploring
+the heavens with a powerful telescope, he noticed something which
+he took for a comet without a tail. He saw it was no mere point of
+light like the stars, but had a tiny round disk or face, which could
+be magnified. So he watched it carefully, and found in the course of
+a few nights that it moved--very slowly, certainly; but still it did
+move. Further watching and calculation made it clear that, though the
+newly-found heavenly body was at a very great distance from the sun,
+yet it was moving slowly in an orbit _round_ the sun. Then it was
+known to be a planet, and another member of the Solar System.
+
+From that day the reputation of Herschel rapidly increased. King George
+III, who loved the sciences and patronized them, had the astronomer
+presented to him; charmed with the simple and modest account of his
+efforts and his labors, he secured him a life pension and a residence
+at Slough, in the neighborhood of Windsor Castle. His sister Caroline
+assisted him as secretary, copied all his observations, and made all
+his calculations; the king gave him the title and salary of assistant
+astronomer. Before long the observatory at Slough surpassed in
+celebrity the principal observatories of Europe; we may say that, in
+the whole world, this is the place where the most discoveries have been
+made.
+
+Astronomers soon applied themselves to the observation of the new body.
+They supposed that this “comet” would describe, as usually happens,
+a very elongated ellipse, and that it would approach considerably
+to the sun at its perihelion. But all the calculations made on this
+supposition had to be constantly recommenced. They could never succeed
+in representing all its positions, although the star moved very slowly:
+the observations of one month would utterly upset the calculations of
+the preceding month.
+
+Several months elapsed without a suspicion that a veritable planet
+was under observation, and it was not till after recognizing that all
+the imaginary orbits for the supposed comet were contradicted by the
+observations, and that it had probably a circular orbit much farther
+from the sun than Saturn, till then the frontier of the system, that
+astronomers came to consider it as a planet. Still, this was at first
+but a provisional consent.
+
+[Illustration: PROMINENT ASTRONOMERS OF FORMER TIMES. Tycho Brahe,
+Hipparchos, Galilei, Newton, Kepler, Kant, Kopernikus, Laplace.]
+
+It was, in fact, more difficult than we may think to increase without
+scruple the family of the sun. Indeed, for reasons of expediency this
+idea was opposed. Ancient ideas are tyrannical. Men had so long been
+accustomed to consider old Saturn as the guardian of the frontiers,
+that it required a rare boldness of spirit to decide on extending these
+frontiers and marking them by a new world.
+
+William Herschel proposed the name of _Georgium Sidus_ “the Star of
+George,” just as Galileo had given the name of “Medicean stars” to
+the satellites of Jupiter discovered by him, and as Horace had said
+_Julium Sidus_. Others proposed the name of _Neptune_, in order to
+maintain the mythological character, and to give to the new body the
+trident of the English maritime power; others, _Uranus_, the most
+ancient deity of all, and the father of Saturn, to whom reparation
+was due for so many centuries of neglect. Lalande proposed the name
+of _Herschel_, to immortalize the name of its discoverer. These last
+two denominations prevailed. For a long time the planet bore the
+name of Herschel; but custom has since declared for the mythological
+appellation, and Jupiter, Saturn, and Uranus succeed each other in
+order of descent--son, father, and grandfather.
+
+The discovery of Uranus extended the radius of the Solar System from
+885,000,000 to 1,765,000,000 of miles.
+
+The apparent brightness of this planet is that of a star of the
+sixth magnitude; observers whose sight is very piercing may succeed
+in recognizing it with the naked eye when they know where to look for
+it. Uranus moves slowly from west to east, and takes no less than
+eighty-four years to make the complete circuit of the sky. In its
+annual motion round the sun the earth passes between the sun and Uranus
+every 369 days--that is to say, once in a year and four days. It is at
+these times that this planet crosses the meridian at midnight. We can
+observe it in the evening sky for about six months of every year.
+
+Everybody supposed that now, at least, the outermost member of all was
+discovered. But a very strange and remarkable thing happened.
+
+Astronomers know with great exactness the paths of the planets in
+the heavens. They can tell, years beforehand, precisely what spot in
+space will be filled at any particular time by any particular planet.
+I am speaking now of their movements round the sun and in the Solar
+System--not of the movements of the whole family with the sun, about
+which little is yet known.
+
+Each planet has its own particular pathway; its own particular distance
+from the sun, varying at each part of its pathway; its own particular
+speed in traveling round the sun, changing constantly from faster to
+slower or slower to faster, according to its distance from the sun, and
+according to the pull backwards or forwards of our neighboring planets
+in front or in rear. For as the orbits of all the planets are ovals,
+with the sun not in the middle, but somewhat to one side of the middle,
+it follows that all the planets, in the course of their years, are
+sometimes nearer to and sometimes farther from the sun.
+
+The astronomers of the present day understand this well, and can
+describe with exactness the pathway of each planet. This knowledge
+does not come merely from watching one year how the planets travel,
+and remembering for another year, but is much more a matter of close
+and difficult calculation. Many things have to be considered, such as
+the planet’s distance from the sun, the sun’s power of attraction, the
+planet’s speed, the nearness and weight of other neighboring planets.
+
+All these questions were gone into, and astronomers sketched out the
+pathway in the heavens which they expected Uranus to follow. He would
+move in such and such an orbit, at such and such distances from the
+sun, and at such and such rates of speed.
+
+But Uranus would not keep to these rules. He quite discomfited the
+astronomers. Sometimes he went fast, when, according to their notions,
+he ought to have gone more slowly; and sometimes he went slowly, when
+they would have looked for him to go more fast, and the line of his
+orbit was quite outside the line of the orbit which they had laid
+down. He was altogether a perplexing acquaintance, and difficult to
+understand. However, astronomers felt sure of their rules and modes of
+calculation, often before tested, and not found to fail. They made a
+guess at an explanation. What if there were yet another planet beyond
+Uranus, disturbing his motions--now drawing him on, now dragging him
+back, now so far balancing the sun’s attraction by pulling in the
+opposite direction as to increase the distance of Uranus from the sun?
+
+It might be so. But who could prove it? Hundreds of years might pass
+before any astronomer, in his star-gazing, should happen to light upon
+such a dim and distant world. Nay, the supposed planet might be, like
+Uranus, actually seen, and only be mistaken for a “variable star,”
+shining but to disappear.
+
+There the matter seemed likely to rest. There the matter probably would
+have rested for a good while, had not two men set themselves to conquer
+the difficulty. One was a young Englishman, a student of Cambridge,
+John Couch Adams; the other, a young Frenchman, Urbain Jean Joseph
+Leverrier,--both being astronomers.
+
+Each worked independently of the other, neither knowing of the other’s
+toil. The task which they had undertaken was no light one--that of
+reaching out into the unknown depths of space to find an unknown planet.
+
+Each of these silent searchers into the sky-depths calculated what the
+orbit and speed of Uranus would be, without the presence of another
+disturbing planet beyond. Each examined what the amount of disturbance
+was, and considered the degree of attraction needful to produce that
+disturbance, together with the direction from which it had come. Each,
+in short, gradually worked his way through calculations far too deep
+and difficult for ordinary minds to grasp, till he had found just that
+spot in the heavens where a planet _ought_ to be, to cause, according
+to known laws, just such an effect upon Uranus as had been observed.
+
+Adams finished his calculation first, and sent the result to two
+different observatories. Unfortunately, his report was not eagerly
+taken up. It was, in fact, hardly believed. Leverrier finished his
+calculation also, and sent the result to the Berlin Observatory. The
+planet was actually seen in England first, but the discovery was
+actually made known from Berlin first. The young Englishman had been
+beforehand, but the young Frenchman gained foremost honor.
+
+It was on the 23d of September, 1846, that Leverrier’s letter reached
+the Berlin astronomers. The sky that night was clear, and we can easily
+understand with what anxiety Dr. Galle directed his telescope to the
+heavens. The instrument was pointed in accordance with Leverrier’s
+instructions. The field of view showed, as does every part of the
+heavens, a multitude of stars. One of these was really the planet. The
+new chart--prepared by the Berlin Academy of Sciences, upon which the
+place of every star, down even to those of the tenth magnitude, was
+engraved--was unrolled, and, star by star, the heavens were compared
+with the chart. As the process of identification went on, one object
+after another was found in the heavens as engraved on the chart, and
+was of course rejected. At length a star of the eighth magnitude--a
+brilliant object--was brought into review. The map was examined, but
+there was no star there. This object could not have been in its present
+place when the map was formed. The object was therefore a wanderer--a
+planet. Yet it is necessary to be excessively cautious in such a matter.
+
+Many possibilities had to be guarded against. It was, for instance,
+possible that the object was really a star which, by some mischance,
+eluded the careful eye of the astronomer who constructed the map.
+It was even possible that the star might be one of the large class
+of variables which alternate in brightness, and it might have been
+conceivable that it was too faint to be seen when the chart was made.
+Even if neither of these explanations would answer, it was still
+necessary to show that the object was now moving, and moving with that
+particular velocity and in that particular direction which the theory
+of Leverrier indicated. The lapse of a single day was sufficient to
+dissipate all doubts. The next night the object was again observed.
+It had moved, and when its motion was measured it was found to
+accord precisely with what Leverrier had foretold. Indeed, as if no
+circumstance in the confirmation should be wanting, it was ascertained
+that the diameter of the planet, as measured by the micrometers at
+Berlin, was practically coincident with that anticipated by Leverrier.
+
+The world speedily rang with the news of this splendid achievement.
+Instantly the name of Leverrier rose to a pinnacle hardly surpassed by
+that of any astronomer of any age or country. For a moment it seemed
+as if the French nation were to enjoy the undivided honor of this
+splendid triumph. But in the midst of the pæans of triumph with which
+the enthusiastic French nation hailed the discovery of Leverrier,
+there appeared a letter from Sir John Herschel in the _Athenæum_ for
+3d October, 1846, in which he announced the researches made by Adams,
+and claimed for him a participation in the glory of the discovery.
+Subsequent inquiry has shown that this claim was a just one, and it is
+now universally admitted by all independent authorities.
+
+This, however, was of slight comparative importance. The truly
+wonderful part of the matter was, that these two men could have so
+reasoned that, from the movements of one lately-discovered planet, they
+could point out the exact spot where a yet more distant planet ought to
+be, and that close to this very spot the planet was found. For when,
+both in England and in Germany, powerful telescopes were pointed in the
+direction named--_there the planet was_. No doubt about the matter. Not
+a star, but a real new planet in the far distance, wandering slowly
+round the sun.
+
+Here we have the discovery of Neptune in its simple grandeur. This
+discovery is splendid, and of the highest order from a philosophical
+point of view, for it proves the security and the precision of the data
+of modern astronomy. Considered from the point of view of practical
+astronomy, it was but a simple exercise of calculation, and the most
+eminent astronomers saw in it nothing else! It was only after its
+verification, its public demonstration--it was only after the visual
+discovery of Neptune--that they had their eyes opened, and felt for a
+moment the dizziness of the infinite in view of the horizon revealed by
+the Neptunian perspective. The author of the calculation himself, the
+transcendent mathematician, did not even give himself the trouble to
+take a telescope and look at the sky to see whether a planet was really
+there! I even believe that he never saw it. For him, however, then
+and always, to the end of his life, astronomy was entirely inclosed in
+formulæ--the stars were but centers of force.
+
+Very often I submitted to him the doubts of an anxious mind on the
+great problems of infinitude: I asked him if he thought that the other
+planets might be inhabited like ours, what might be especially the
+strange vital conditions of a world separated from the sun by the
+distance of Neptune, what might be the retinue of innumerable suns
+scattered in immensity, what astonishing colored lights the double
+stars should shed on the unknown planets which gravitate in these
+distant systems. His replies always showed me that these questions had
+no interest for him, and that, in his opinion, the essential knowledge
+of the universe consisted in equations, formulæ, and logarithmic series
+having for their object the mathematical theory of velocities and
+forces.
+
+But it is not the less surprising that he had not the _curiosity_ to
+verify the position of his planet, which would have been easy, since
+it shows a planetary disk; and, besides, he might have had the aid of
+a chart, because he had only to ask for these charts from the Berlin
+Observatory, where they had just been finished and _published_. It
+is not the less surprising that Arago, who was more of a physicist
+than a mathematician, more of a naturalist than a calculator, and
+whose mind had so remarkable a synthetical character, had not himself
+directed one of the telescopes of the observatory towards this point
+of the sky, and that no other French astronomer had this idea. But
+what surprises us still more is to know that _nearly a year before_,
+in October, 1845, a young student of the University of Cambridge, Mr.
+Adams, had sought the solution of the _same_ problem, obtained the
+same results, and communicated these results to the director of the
+Greenwich Observatory, and that the astronomer to whom these results
+were confided had said nothing, and had not himself searched in the sky
+for the optical verification of his compatriot’s solution!
+
+This was indeed a triumph of human intellect. Yet it is no matter
+for human pride, but rather of thankfulness to God, who gave to man
+this marvelous reasoning power. And the very delight we have in such
+a success may humble us in the recollection of the vast amount lying
+beyond of the utterly unknown. But while the rare mind of a Newton
+could meekly realize the littleness of all he knew, lesser minds are
+very apt to be puffed up with the thought of what the human intellect
+can accomplish.
+
+Perhaps the chief feeling of lawful satisfaction in this particular
+discovery arises from the fact that it gives marked and strong proof
+of the truth of our present astronomical system and beliefs. Many
+mistakes may be made, and much has often to be unlearned. Nevertheless,
+if the general principles of modern astronomy were wrong, if the
+commonly-received facts were a delusion, such complete success could
+not have attended so delicate and difficult a calculation.
+
+We do not know much about these two outer planets, owing to their
+enormous distance from us. Uranus is in size equal to seventy-four
+earths, and Neptune is in size equal to one hundred and five earths.
+Both these planets are formed of somewhat heavier materials than
+Saturn, being about as dense as water.
+
+The size of the sun as seen from Uranus is about one
+three-hundred-and-ninetieth part of the size of the sun we see. To
+Neptune he shows a disk only one nine-hundredth part of the size
+of that visible to us--no disk at all, in fact, but only starlike
+brilliancy.
+
+The Uranian year lasts about eighty-four of our years; and this, with
+a very sloping axis, must cause most long and dreary winters, the
+tiny sun being hidden from parts of the planet during half an earthly
+life-time.
+
+Uranus has at least four moons, traveling in very different planes from
+the plane of the ecliptic. Once it was thought that he had eight, but
+astronomers have since searched in vain for the other four, believed
+for a while to exist. Neptune has one moon, and may possess others not
+yet discovered.
+
+Sir Henry Holland, the celebrated physician, and a devoted student of
+astronomy, has left on record an incident of his life connected with
+the planet Neptune of singular interest. I give it here, and in his own
+words, because it is scarcely likely otherwise to fall under the notice
+of astronomical readers. After stating that his interest in astronomy
+had led him to take advantage of all opportunities of visiting foreign
+observatories, he says:
+
+“Some of these opportunities, indeed, arising out of my visits to
+observatories both in Europe and America, have been remarkable enough
+to warrant a more particular mention of them. That which most strongly
+clings to my memory is an evening I passed with Encke and Galle in the
+observatory at Berlin, some ten or twelve days after the discovery
+of the planet Neptune on this very spot; and when every night’s
+observations of its motions had still an especial value in denoting
+the elements of its orbit. I had casually heard of the discovery
+at Bremen, and lost no time in hurrying on to Berlin. The night in
+question was one of floating clouds, gradually growing into cumuli; and
+hour after hour passed away without sight of the planet which had just
+come to our knowledge by so wonderful a method of predictive research.
+Frustrated in this main point, it was some compensation to stay and
+converse with Encke in his own observatory, one signalized by so many
+discoveries, the stillness and darkness of the place broken only by
+the solemn ticking of the astronomical clock, which, as the unfailing
+interpreter of the celestial times and motions, has a sort of living
+existence to the astronomer. Among other things discussed, while thus
+sitting together in a sort of tremulous impatience, was the name to be
+given to the new planet. Encke told me he had thought of ‘Vulcan,’ but
+deemed it right to remit the choice to Leverrier, then supposed to be
+the sole indicator of the planet and its place in the heavens; adding
+that he expected Leverrier’s answer by the first post. Not an hour had
+elapsed before a knock at the door of the observatory announced the
+letter expected. Encke read it aloud; and, coming to the passage where
+Leverrier proposed the name of ‘Neptune,’ exclaimed, ‘_So lass den
+Namen Neptun sein._’
+
+It was a midnight scene not easily to be forgotten. A royal baptism,
+with its long array of titles, would ill compare with this simple
+naming of the remote and solitary planet thus wonderfully discovered.
+There is no place, indeed, where the grandeur and wild ambitions of the
+world are so thoroughly rebuked and dwarfed into littleness as in the
+astronomical observatory. As a practical illustration of this remark,
+I would add that my own knowledge of astronomers--those who have
+worked themselves with the telescope--has shown them to be generally
+men of tranquil temperament, and less disturbed than others by worldly
+affairs, or by the quarrels incident even to scientific research.”
+
+The same reasoning which has been used in reference to Jupiter and his
+moons, and to Saturn and his moons, might perhaps be applied also to
+Uranus and Neptune and their moons.
+
+We know too little yet of their condition to venture far in such
+speculations. Still, taking the matter as a whole, there seem many
+reasons to incline us to the idea that each of the four greater outside
+planets may be a kind of secondary half-cooled sun to his satellites,
+helping to make up to them for the small amount of light and heat which
+they can obtain from the far-off sun.
+
+
+
+
+CHAPTER XX.
+
+COMETS AND METEORITES.
+
+
+A curious discovery has been lately made. It is that some sort of
+mysterious tie seems to exist between comets and meteorites. For a long
+while this was never suspected. How should it be? The comets, so large,
+so airy, so light; the meteorites, so small, so solid, so heavy,--how
+could it possibly be supposed that the one had anything to do with
+the other? But supposings often have to give in to facts. Astronomers
+are gradually becoming convinced that there certainly is a connection
+between the two.
+
+Strange to say, comets and meteorites occupy--sometimes, at least--the
+very same pathways in the heavens, the very same orbits round the
+sun. A certain number of meteorite systems are now pretty well known
+to astronomers as regularly met by our earth at certain points in
+her yearly journey. Some of these systems or rings have each a comet
+belonging to it--not merely journeying near, but actually in its midst,
+on the same orbit.
+
+Perhaps it would be more correct to say that the meteorites belong to
+the comet, than that the comet belongs to the meteorites. We tread here
+on uncertain ground; for whether the meteorites spring from the comet,
+or whether the comet springs from the meteorites, or whether each has
+been brought into existence independently of the other, no one can at
+present say.
+
+Though it is out of our power to explain the kind of connection, yet a
+connection there plainly is. So many instances are now known of a comet
+and a meteorite ring traveling together that it is doubtful whether any
+such ring could be found without a comet in its midst. By and by the
+doubt may spring up whether there ever exists a comet without a train
+of meteorites following him.
+
+Among the many different meteorite rings which are known, two of the
+most important are the so-called August and November systems. Of these
+two, the November system must claim our chief attention. Not that we
+are at all sure of these being the most important meteorite rings in
+the Solar System. On the contrary, as regards the November ring, we
+have some reason to think that matters may lie just the other way.
+
+The comet belonging to the November system is a small one--quite an
+insignificant little comet--only visible through a telescope. We
+do not, of course, know positively that larger comets and greater
+meteorite systems generally go together, but, to say the least, it
+seems likely. And if the greatness of a ring can at all be judged of by
+the size of its comet, then the November system must be a third-rate
+specimen of its kind. It is of particular importance to us, merely
+because it happens to be the one into which our earth plunges most
+deeply, and which we therefore see and know the best. The August ring
+is, on the contrary, connected with a magnificent comet, and may be
+a far grander system. But our pathway does not lead us into the midst
+of the August meteors as into those of November. We pass, seemingly,
+through its outskirts.
+
+The meteorites of the November system are very small. They are believed
+to weigh commonly only a few grains each. If they were larger and
+heavier, some of them would fall to earth as aerolites, not more than
+half-burnt in their rush through the atmosphere. But this they are
+never found to do.
+
+There are known meteorite systems, which our earth merely touches
+or grazes in passing, from which drop aerolites of a very different
+description--large, heavy, solid masses. It is well for us that we do
+not plunge into the midst of any such ring, or we might find our air,
+after all, a poor protection.
+
+The last grand display of the November system of meteorites took place
+in the years 1866 to 1869, being continued more or less during three or
+four Novembers following. The next grand display will occur in the year
+1899.
+
+For this system--Leonides, as it is called, because the falling-stars
+in this display seem all to shoot towards us from a spot in the
+constellation Leo--seems to have a “time” or “year” of thirty-three and
+a quarter earthly years. The shape of its orbit is a very long ellipse,
+near one end of which is the sun, while the other end is believed to
+reach farther away than the orbit of Uranus.
+
+A great deal of curiosity has been felt about the actual length and
+breadth and depth of the stream of meteorites through which our
+solid earth has so often plowed her way. During many hours at a
+time, lookers-on have watched the magnificent display of heavenly
+fireworks,--not a mere shooting-star here and there, as on common
+nights, but radiant meteors, flashing and dying by thousands through
+the sky. In 1866 no less than eight thousand meteors, in two hours and
+a quarter, were counted from the Greenwich Observatory in England. A
+natural wonder sprang up in many minds as to the extent of the ring
+from which they fell.
+
+For not in one night only, but in several nights during three or four
+years, and that not once only but once in every thirty-three years,
+thousands and tens of thousands appear to have been stolen by our earth
+from the meteorite-ring, never again to be restored. Yet each time we
+touch the ring, we find the abundance of little meteorites in nowise
+seemingly lessened.
+
+When speaking of a “ring” of meteorites, it must not be supposed that
+necessarily the meteorites form a whole unbroken ring all round the
+long oval orbit. There may be no breaks. There may be a more or less
+thin scattering throughout the entire length of the pathway. But the
+meteorites certainly seem to cluster far more densely in some parts of
+the orbit than in other parts, and it was about the size of the densest
+cluster that so much curiosity was felt.
+
+Little can be positively known, though it is very certain that the
+cluster must be enormous in extent. Three or four years running, as our
+earth, after journeying the whole way round the sun, came again to that
+point in her orbit where she passes through the orbit of the Leonides,
+she found the thick stream of meteorites still pouring on, though each
+year lessening in amount. Taking into account this fact, and also the
+numbers that were seen to fall night after night, and also the speed of
+our earth, a “rough estimate” was formed.
+
+The length of this dense cluster is supposed to reach to many
+hundreds of millions of miles. The thickness or depth of the stream
+is calculated to be in parts over five hundred thousand miles, and
+the breadth about ten times as much as the depth. Each meteorite is
+probably at a considerable distance from his neighbor; but the whole
+mass of them, when in the near neighborhood of the sun, must form a
+magnificent sight.
+
+And if this be only a third-rate system, what must a first-rate system
+be like? And how many such systems are there throughout the sun’s wide
+domains? The most powerful telescope gives us no hint of the existence
+of these rings till we find ourselves in their midst.
+
+It may be that they are numbered by thousands, even by millions. The
+whole of the Solar System--nay, the very depths of space beyond--may,
+for aught we know, be crowded with meteorite systems. Every comet may
+have his stream of meteorites following him. But though the comet is
+visible to us, the meteorites are not. Billions upon billions of them
+may be ever rushing round our sun, entirely beyond our ken, till one
+or another straggler touches our atmosphere to flash and die as a
+“shooting star” in our sight.
+
+We have, and with our present powers we can have, no certainty as
+to all this. But I may quote here the illustration of a well-known
+astronomical writer on the subject.
+
+Suppose a blind man were walking out of doors along a high road, and
+during the course of a few miles were to feel rain falling constantly
+upon him. Would it be reasonable on his part, if he concluded that a
+small shower of rain had accompanied him along the road as he moved,
+but that fine weather certainly existed on either side of the road? On
+the contrary, he might be sure that the drops which he felt, were but a
+few among millions falling all together.
+
+Or, look at the raindrops on your window some dull day at home. Count
+how many there are? Could you, with any show of common sense, decide
+that those raindrops, and those alone, had fallen that day? So, when
+we find these showers of meteorites falling to earth, we may safely
+conclude that, for every one which touches our atmosphere, myriads rush
+elsewhere in space, never coming near us.
+
+
+
+
+CHAPTER XXI.
+
+MORE ABOUT COMETS AND METEORITES.
+
+
+The three prominent features of comets--a head, nucleus, and tail--are
+seen only in particular instances. The great majority appear as faint
+globular masses of vapor, with little or no central condensation, and
+without tails. On the other hand, some have a strongly-defined nucleus,
+which shines with a light as vivacious as that of the planets, so as to
+be even visible in the daytime. This was the case with one seen at Rome
+soon after the assassination of Julius Cæsar, believed by the populace
+to be the soul of the dictator translated to the skies. The first comet
+of the year 1442 was also so brilliant, that the light of the sun at
+noon, at the end of March, did not prevent it from being seen; and the
+second, which appeared in the summer, was visible for a considerable
+time before sunset. In 1532, the people of Milan were alarmed by the
+appearance of a star in the broad daylight; and as Venus was not then
+in a position to be visible, the object is inferred to have been a
+comet. Tycho Brahe discovered the comet of 1577, from his observatory
+in the isle of Huene, in the sound, before sunset; and Chizeaux saw the
+comet of 1744, at one o’clock in the afternoon, without a telescope.
+
+The comet of 1843, already referred to in a previous chapter, was
+distinctly seen at noon by many persons in the streets of Bologna
+without the aid of glasses. The nucleus is generally of small size,
+but the surrounding nebulosity, which forms the head, is often of
+immense extent; and the hazy envelope, the “horrid hair” of poetry, is
+sometimes seen separated from it by a dark space, encircling it like a
+ring. This was the aspect of the comet of 1811. The entire diameter of
+the head measured 1,250,000 miles, and hence its bulk was nearly three
+times that of the sun, and four million times that of the earth. But
+such extraordinary dimensions are quite exceptional.
+
+[Illustration: THE GREAT COMET OF 1811.]
+
+Popular impressions respecting the supposed terrestrial effects of
+the comet of 1811--a fine object in the autumn of that year, long
+remembered by many--are on record. It was gravely noted, that wasps
+were very few in number; that flies became blind, and disappeared
+early; and that twins were born more frequently than usual. The
+season was remarkable for its bountiful harvest and abundant vintage.
+Grapes, figs, melons, and other fruits, were not only produced in
+extraordinary quantity, but of delicious flavor, so that “comet wines”
+had distinct bins allotted to them in the cellars of merchants, and
+were sold at high prices. There is, however, no fact better attested,
+by a comparison of observations, than that comets have no influence
+whatever in heightening or depressing the temperature of the seasons.
+The fine fruits and ample harvest of the year in question were,
+therefore, coincidences merely with the celestial phenomenon, without
+the slightest physical connection with it.
+
+Though the advanced civilization of recent times has led to juster
+views of cometary apparitions than to regard them as divinely-appointed
+omens of terrestrial calamity, yet society is apt to be nervous
+respecting these bodies, as likely to cause some great natural
+convulsion by collision with our globe.
+
+The great comet, which in 1682 received first the name of Halley’s
+comet, appeared last in 1835, his return having been foretold within
+three days of its actually taking place. For Halley’s comet is a member
+of the Solar System, having a yearly journey of seventy-six earthly
+years. He journeys nearer the sun than Venus, and travels farther away
+than Neptune.
+
+In the years 1858, 1861, and 1862, three more comets appeared, all
+visible without the help of a telescope. Of these three, Donati’s
+comet, in 1858, was far superior to the rest. This fine object was
+first discovered on the 2d of June by Dr. Donati, at Florence. It
+appeared at first as a faint nebulous patch of light, without any
+remarkable condensation; and as its motion towards the sun at that
+time was slow, it was not till the beginning of September that it
+became visible to the naked eye. A short tail was then seen on the side
+opposite to the sun.
+
+[Illustration: DONATI’S COMET, 1858.]
+
+The development was afterwards rapid, and the comet became equally
+interesting to the professional astronomer and to the unlearned gazer.
+In the first week of October the tail attained its greatest length,
+36°. At this time the tail was sensibly curved, and had the appearance
+of a large ostrich-feather when waved gently in the hand. At the latter
+end of October the comet was lost in the evening twilight. Its nearest
+approach to the earth was about equal to half the distance of the earth
+from the sun, and the nearest approach to Venus was about one-ninth
+part of that distance. An elliptical orbit, with a periodic time of
+more than 2,000 years, has been assigned to our late visitor.
+
+It was a singular fact about this comet that at one time the star
+Arcturus could be seen shining through the densest portion of the tail,
+close to the nucleus. Now, although the faintest cloud-wreath of earth
+would dim, if not hide, this star, yet the tail of the great comet was
+of so transparent a nature that Arcturus shone undimmed, as if no veil
+had come between. The exceedingly slight and airy texture of a comet’s
+tail could hardly be more plainly shown. It was this gauzy appendage to
+a little nucleus which men once thought could destroy our solid earth
+at a single blow!
+
+These cometary trains generally appear straight, or at least, by the
+effect of perspective, they seem to be directed along the arcs of great
+circles of the celestial sphere. Some are recorded, however, which
+presented a different appearance. Thus, in 1689, a comet was seen whose
+tail, according to the historians, was curved like a Turkish saber.
+This tail had a total length of 68°. It was the same with the beautiful
+comet of Donati, which we admired in 1858, and of which the tail had a
+very decided curvature.
+
+A comet can only be observed in the sky for a limited time. We
+perceive it at first in a region where nothing was visible on preceding
+days. The next day, the third day, we see it again; but it has changed
+its place considerably among the constellations. We can thus follow it
+in the sky for a certain number of days, often during several months;
+then we cease to perceive it. Often the comet is lost to view because
+it approaches the sun, and the vivid light of that body hides it
+completely; but soon we observe it again on the other side of the sun,
+and it is not till some time afterwards that it definitely disappears.
+Some have been visible at noonday, quite near the sun, like that of
+1882, on September 17th.
+
+Yet, while taking care not to overrate, we must not underrate. True,
+the comets are delicate and slight in structure. One comet, in 1770,
+wandered into the very midst of Jupiter’s moons, and so small was its
+weight that it had no power whatever, so far as has been detected, to
+disturb the said moons in their orbits. Jupiter and his moons did very
+seriously disturb the comet, however; and when he came out from their
+midst, though none the worse for his adventure, he was forced to travel
+in an entirely new orbit, and never managed to get back to his old
+pathway again.
+
+But there are comets _and_ comets, some being heavier than others. The
+comet named after Donati, albeit too transparent to hide a star, was
+yet so immense in size that his weight was calculated by one astronomer
+to amount to as much as a mass of water forty thousand miles square and
+one hundred and nine yards deep.
+
+When first noticed, Donati’s comet had, like all large comets, a
+bright envelope of light round the nucleus. After a while the one
+envelope grew into three envelopes, and a new tail formed beside the
+principal tail, which for a time was seen to bend gracefully into a
+curve, like a splendid plume. A third, but much fainter tail, also
+made its appearance, and many angry-looking jets were poured out from
+the nucleus. These changes took place while the comet was passing
+through the great heat of near neighborhood to the sun. Afterwards, as
+he passed away, he seemed gradually to cool down and grow quiet. The
+singular changes in the appearance of Newton’s comet have been earlier
+noticed. No marvel that he did undergo some alterations. The tremendous
+glare and burning heat which that comet had to endure in his rush past
+the sun, were more than twenty-five thousand times as much as the glare
+and heat of the fiercest tropical noonday ever known upon earth. Can we
+wonder that he should have shown “signs of great excitement,” that his
+head should have grown larger and his tail longer?
+
+It certainly was amazing, and past comprehension, that the said tail,
+over ninety millions of miles in length, should in four days have
+seemingly swept round in a tremendous half-circle, so as first to point
+in one direction, and then to point in just the opposite direction.
+
+We are much in the habit of speaking about comets as traveling through
+the heavens with their tails streaming behind them. But though this is
+sometimes the case, it is by no means always.
+
+The tails of comets always stream _away from the sun_--whether before
+or behind the comet’s head seeming to be a matter of indifference. As
+the comet comes hurrying along his orbit, with ever-increasing speed,
+towards the sun, the head journeys first, and the long tail follows
+after. But as the comet rounds the loop of his orbit near the sun--the
+point nearest of all being called his _perihelion_--the head always
+remains towards the sun, while the tail swings, or seems to swing, in
+a magnificent sweep round, pointing always in the direction just away
+from the sun.
+
+Then, as the comet journeys with slackening speed, on the other side of
+his orbit, towards the distant _aphelion_, or farthest point from the
+sun, he still keeps his head towards the sun. So, at this part of his
+passage, in place of the head going first and the tail following after,
+the tail goes first and the head follows after. The comet thus appears
+to be moving backwards; or, like an engine pushing instead of drawing a
+train, the head seems to be driving the tail before it.
+
+[Illustration: GREAT COMET OF 1744.]
+
+[Illustration: THE FIRST COMET OF 1888--JUNE 4.]
+
+The sun, then, acts on these bodies when they approach him, produces
+in them important physical and chemical transformations, and exercises
+on their developed atmosphere a repulsive force, the nature of which
+is still unknown to us, but the effects of which coincide with the
+formation and development of the tails. The tails are thus, in the
+extension of the cometary atmosphere, driven back, either by the
+solar heat, by the light, by electricity, or by other forces; and
+this extension is rather a motion in the ether than a real transport
+of matter, at least in the great comets which approach very near the
+sun, and in their immense luminous appendages. The effects produced
+and observed are not the same in all comets, which proves that they
+differ from each other in several respects. The tails have sometimes
+been seen to diminish before the perihelion passage, as in 1835.
+Luminous envelopes have also been seen succeeding each other round the
+head, concentrating themselves on the side opposite to the sun, and
+leaving the central line of the tail darker than the two sides. This
+is what happened in the Donati comet and in that of 1861. Sometimes a
+secondary tail has been seen projected towards the sun, as in 1824,
+1850, 1851, and 1880. Comets have been seen with the head enveloped in
+phosphorescence, surrounding them with a sort of luminous atmosphere.
+Comets have also been seen with three, four, five, and _six tails_,
+like that of 1744, for example, which appeared like a splendid aurora
+borealis rising majestically in the sky, until, the celestial fan being
+raised to its full height, it was perceived that the six jets of light
+all proceeded from the same point, which was nothing else but the
+nucleus of a comet. On the other hand, the nuclei themselves show great
+variations--some appear simply nebulous, and permit the faintest stars
+to be visible through them; others seem to be formed of one or more
+solid masses surrounded by an enormous atmosphere; in others, again, a
+nucleus does not exist, as in the Southern comet of 1887. One of the
+comets of 1888 showed a triple nucleus and a bristling coma, as may
+be seen in the cut. We may, then, consider that the wandering bodies
+collected under the name of comets are of several origins and _several
+different species_.
+
+_Why_ the tails of comets should so persistently avoid the sun it is
+impossible to say. We do not even know whether the cause lies actually
+in the sun or in the comet. Astronomers speak of the “repulsive
+energy” with which the sun “sweeps away” from his neighborhood the
+light vapory matter of which the tails are made. But the how and the
+wherefore of this strange seeming repulsion they can not explain. For
+at the selfsame time the sun appears to be attracting the comet towards
+himself, and driving the comet’s tail away from himself.
+
+A few of the more well-known comets have been mentioned; but a year
+rarely passes in which at least one comet is not discovered, though
+often only a small specimen, sometimes even tailless and hairless. No
+doubt many others pass unseen. The large and grand ones only come to
+view now and then.
+
+What are comets and meteorites made of? Respecting comets, a good
+many ideas are put forth, and a good many guesses are made, as to
+“burning gas,” “luminous vapor,” “beams of light,” and so on. But in
+truth, little is known about the matter. Respecting meteorites, we can
+speak more certainly. A good many meteorites have fallen to earth as
+aerolites, and have been carefully examined. They are found to contain
+nickel, cobalt, iron, phosphorus, and sometimes at least, a large
+supply of hydrogen gas.
+
+Not only do solid aerolites fall half-burnt to the ground, but even
+when the meteorites are quite consumed in the air, the fine dust
+remaining still sinks earthward. This fine dust has been found upon
+mountain-tops, and has been proved by close examination to be precisely
+the same as the material of the solid aerolites.
+
+A luminous body of sensible dimensions rapidly traverses space,
+diffusing on all sides a vivid light--like a globe of fire of which
+the apparent size is often comparable with that of the moon. This
+body usually leaves behind it a perceptible luminous train. On or
+immediately after its appearance it often produces an explosion, and
+sometimes even several successive explosions, which are heard at great
+distances. These explosions are also often accompanied by the division
+of the globe of fire into luminous fragments, more or less numerous,
+which seem to be projected in different directions. This phenomenon
+constitutes what is called a _meteor_, properly speaking, or a
+_bolide_. It is produced during the day as well as the night. The light
+which it causes in the former case is greatly enfeebled by the presence
+of the solar light, and it is only when it is developed with sufficient
+intensity that it can be perceived.
+
+In the British Museum there is a superb collection of meteorites. They
+have been brought together from all parts of the earth, and vary in
+size from bodies not much larger than a pin’s-head up to vast masses
+weighing many hundred pounds. There are also many models of celebrated
+meteorites, of which the originals are dispersed through various other
+museums.
+
+Many of these objects have nothing very remarkable in their external
+appearance. If they were met with on the sea-beach, they would be
+passed by without more notice than would be given to any other stone.
+Yet what a history such a stone might tell us if we could only manage
+to obtain it! It fell; it was seen to fall from the sky; but what
+was its course anterior to that movement? Where was it one hundred
+years ago, one thousand years ago? Through what regions of space has
+it wandered? Why did it never fall before? Why has it actually now
+fallen? Such are some of the questions which crowd upon us as we
+ponder over these most interesting bodies. Some of these objects are
+composed of very characteristic materials. Take, for example, one of
+the more recent meteorites, known as the Rowton siderite. This body
+differs very much from the more ordinary kind of stony meteorite. It
+is an object which even a casual passer-by would hardly pass without
+notice. Its great weight would also attract attention, while if it be
+scratched or rubbed with a file, it would be found that it was not in
+any sense a stone, but that it was a mass of nearly pure iron. We know
+the circumstances under which that piece of iron fell to the earth.
+It was on the 20th of April, 1876, about 3.40 P. M., that a strange
+rumbling noise, followed by a startling explosion, was heard over an
+area of several miles in extent among the villages in Shropshire. About
+an hour after this occurrence, a farmer noticed the ground in one of
+his grass-fields to have been disturbed, and he probed the hole which
+the meteorite had made, and found it, still warm, about eighteen inches
+below the surface. Some men working at no great distance had actually
+heard the noise of its descent, but without being able to indicate
+the exact locality. This remarkable object weighs 7¾ pounds. It is an
+irregular angular mass of iron, though all its edges seem to have been
+rounded by fusion in its transit through the air, and it is covered
+with a thick black film of the magnetic oxide of iron, except at the
+point where it first struck the ground.
+
+This siderite is specially interesting on account of its distinctly
+metallic character. Falls of the siderites, as they are called, are not
+so common as those of the stony meteorites; in fact, there are only
+a few known instances of meteoric irons having been actually seen to
+fall, while the falls of stony meteorites are to be counted in scores
+or in hundreds. The inference is that the iron meteorites are much less
+frequent than the stony ones.
+
+It is a wonderful thought that we should really have these visitants
+from the sky, solid metal or showers of dust, coming to us from distant
+space.
+
+If the dust of thousands of meteorites is always thus falling
+earthward, one would imagine that it must in time add something to the
+weight of the earth. And this actually is the case. During the last
+three thousand years, no less than one million tons of meteorite-dust
+must, according to calculation, have fallen to earth out of the sky. A
+million tons is of course a mere nothing compared with the size of the
+world. Still, the fact is curious and interesting.
+
+It has been suggested that, _perhaps_ the flames of the sun are partly
+fed by vast showers of falling meteorites. It has even been suggested
+that _perhaps_, in long past ages, the earth and the planets grew to
+their present size under a tremendous downpour of meteorites; the
+numbers which now drop to earth being merely the thin remains of what
+once existed. But for this guess there is no real foundation.
+
+Whether suns and worlds full-grown, created as in an instant;
+whether tiny meteorites in countless myriads to be used as stones in
+“building;” whether vast masses of flaming gas, to be gradually cooled
+and “framed” into shape--which ever may have come first, and whichever
+may have been the order of God’s working--still that “first” was made
+by him; still he throughout was the Master-builder.
+
+[Illustration: GREAT COMET OF 1680.]
+
+A few words more about “comet-visitors.” Many comets, as already
+stated, belong to our Solar System, though whether they have always so
+belonged is another question. It is not impossible that they may once
+upon a time have wandered hence from a vast distance, and, being caught
+prisoner by the powerful attraction of Jupiter or one of his three
+great brother-planets, have been compelled thenceforth to travel in a
+closed pathway round the sun.
+
+[Illustration: GREAT COMET OF 1769.]
+
+There are also many comets which come once only to our system, flashing
+round past the sun, and rushing away in quite another direction, never
+to return. Where do these comets come from? And where do they go? From
+other suns--brother suns to ours? It may be. One is almost disposed to
+think that it must be so.
+
+Do we ever think what an immense voyage they must have made to come
+from there to here? Do we imagine for how many years they must have
+flown through the dark immensity to plunge themselves into the fires
+of our sun? If we take into account the directions from which certain
+comets come to us, and if we assign to the stars situated in that
+region the least distances consistent with known facts, we find that
+these comets certainly left their last star more than _twenty millions
+of years ago_.
+
+In thus putting to us from the height of their celestial apparitions
+so many notes of interrogation on the grandest problems of creation,
+comets assume to our eyes an interest incomparably greater than that
+with which superstition blindly surrounded them in past ages. When we
+reflect for a moment that a certain comet which shines before us in
+the sky came originally from the depths of the heavens, that it has
+traveled during millions of years to arrive here, and that consequently
+it is by millions of years that we must reckon its age if we wish to
+form any idea of it, we can not refrain from respecting this strange
+visitor as a witness of vanished eras, as an echo of the past, as
+the most ancient testimony which we have of the existence of matter.
+But what do we say? These bodies are neither old nor young. There
+is nothing old, nothing new--all is present. The ages of the past
+contemplate the ages of the future, which all work, all gravitate, all
+circulate, in the eternal plan. Musing, you look at the river which
+flows so gently at your feet, and you believe you see again the river
+of your childhood; but the water of to-day is not that of yesterday, it
+is not the same substance which you have before your eyes, and never,
+never shall this union of molecules, which you behold at this moment,
+come back there--never till the consummation of the ages!
+
+If the appearance of comets forebodes absolutely nothing as to the
+microscopical events of our ephemeral human history, it is not the same
+with the effects which might be produced by their encounter with our
+wandering planet. In such an encounter there is nothing impossible. No
+law of celestial mechanics forbids that two bodies should come into
+collision in their course, be broken up, pulverized, and mutually
+reduced to vapor.
+
+I have before described some of the tremendous outbursts seen on the
+surface of our sun. It is believed that in these outbursts matter is
+expelled, or driven forth, with such fearful violence as to send it
+whirling through space, never to fall back to the sun.
+
+Some meteorites may have their births thus. So also may some comets.
+And if all the stars are suns--huge fiery globes like our sun, and
+subject like him to tremendous eruptions--they too, probably, send out
+comets and meteorites to wander through space. Whether or no comets
+come into existence in any such manner, one thing seems pretty certain.
+Those comets which come to us from outside our system must come from
+some other system. And the nearest systems known are those of the stars.
+
+The nearest star of all, whose distance has been measured, is Alpha
+Centauri. It has been roughly calculated that a comet, passing direct
+from Alpha Centauri to our sun, would take about twenty millions of
+years for his journey. But here we tread upon very doubtful ground.
+Many matters, at present unknown to us, might greatly affect the result
+of such a calculation. Also it is by no means impossible that other
+stars lie really much nearer to us than Alpha Centauri, whose distance
+astronomers have not yet attempted to measure.
+
+[Illustration: BARON ALEXANDER VON HUMBOLDT.]
+
+“In order to complete our view,” says Alexander Von Humboldt, “of all
+that we have learned to consider as appertaining to our Solar System,
+which now, since the discovery of the small planets, of the interior
+comets of short revolutions, and of the meteoric asteroids, is so rich
+and complicated in its form, it remains for us to speak of the ring
+of zodiacal light. Those who have lived for many years in the zone of
+palms must retain a pleasing impression of the mild radiance with which
+the zodiacal light, shooting pyramidally upward, illumines a part of
+the uniform length of tropical nights. I have seen it shine with an
+intensity of light equal to the Milky Way in Saggitarius, and that not
+only in the rare and dry atmosphere of the summit of the Andes, at an
+elevation of from thirteen to fifteen thousand feet, but even on the
+boundless grassy plains of Venezuela, and on the seashore, beneath the
+ever-clear sky of Cumana. This phenomenon was often rendered especially
+beautiful by the passage of light, fleecy clouds, which stood out in
+picturesque and bold relief from the luminous background.
+
+“This phenomenon, whose primordial antiquity can scarcely be doubted,
+is not the luminous solar atmosphere itself, which can not be diffused
+beyond nine-tenths of the distance of Mercury. With much probability we
+may regard the existence of a very compressed ring of nebulous matter,
+revolving freely in space around the sun between the orbits of Venus
+and Mars, as the material cause of the zodiacal light. These nebulous
+particles may either be self-luminous or receive their light from the
+sun.
+
+“I have occasionally been astonished, in the tropical climates of
+South America, to observe the variable intensity of the zodiacal
+light. As I passed the nights, during many months, in the open air,
+on the shores of rivers and on plains, I enjoyed ample opportunities
+of carefully examining this phenomenon. When the zodiacal light had
+been most intense, I have observed that it would be weakened for a
+few minutes, until it again suddenly shone forth in full brilliancy.
+In a few instances I have thought I could perceive, not exactly a
+reddish coloration, nor the lower portion darkened in an arc-like
+form, nor even a scintillation, but a kind of flickering and wavering
+of the light. Must we suppose that changes are actually in progress
+in the nebulous ring? Or is it not more probable that processes of
+condensation may be going on in the uppermost strata of the air,
+by means of which the transparency--or, rather, the reflection of
+light--may be modified in some peculiar and unknown manner? An
+assumption of the existence of such meteorological causes on the
+confines of our atmosphere is strengthened by the sudden flash and
+pulsations of light which have been observed to vibrate for several
+seconds through the tail of a comet. During the continuation of these
+pulsations it has been noticed that the comet’s tail was lengthened by
+several degrees, and then again contracted.”
+
+
+
+
+CHAPTER XXII.
+
+MANY SUNS.
+
+
+Once more we have to wing our flight far, far away from the busy Solar
+System where we live; away from whirling planets, moons, meteorites,
+all shining with reflected sunlight; away from the great central
+sun himself, our own particular bright star. Once more we have, in
+imagination, to cross the vast, black, empty space--_is_ it black, and
+_is_ it empty, had we sight to see things as they are?--separating
+our sun from other suns, our star from other stars. For the sun is a
+star--only a star. And stars are suns--big, blazing suns. One is near,
+and the others are far away. That is the difference.
+
+We have no longer to do with bodies merely reflecting another’s
+light--always dark on one side and bright on the other--but with
+burning bodies, shining all round by their own light. We have no longer
+to picture just one single star with his surrounding worlds, but we
+have to fix our thoughts upon the great universe of stars or suns in
+countless millions.
+
+The earth is forgotten, with its small and ephemeral history. The
+sun himself, with all his immense system, has sunk in the infinite
+night. On the wings of inter-sidereal comets we have taken our flight
+towards the stars, the suns of space. Have we exactly measured, have
+we worthily realized the road passed over by our thoughts? The nearest
+star to us reigns at a distance of 275,000 times our distance from
+the sun; out to that star an immense desert surrounds us, the most
+profound, the darkest, and the most silent of solitudes.
+
+The solar system seems to us very vast; the abyss which separates our
+world from Mars, Jupiter, Saturn, and Neptune, appears to us immense;
+relatively to the fixed stars, however, our whole system represents but
+an isolated family immediately surrounding us: a sphere as vast as the
+whole solar system would be reduced to the size of a simple point if it
+were transported to the distance of the nearest star. The space which
+extends between the solar system and the stars, and which separates
+the stars from each other, appears to be entirely void of visible
+matter, with the exception of nebulous fragments, cometary or meteoric,
+which circulate here and there in the immense voids. Nine thousand
+two hundred and fifty systems like ours, bounded by Neptune, would be
+contained in the space which isolates us from the nearest star!
+
+It is marvelous that we can perceive the stars at such a distance.
+What an admirable transparency in these immense spaces to permit the
+light to pass, without being wasted, to thousands of billions of
+miles! Around us, in the thick air which envelops us, the mountains
+are already darkened and difficult to see at seventy miles; the least
+fog hides from us objects on the horizon. What must be the tenuity,
+the rarefaction, the extreme transparency of the ethereal medium which
+fills the celestial spaces!
+
+The sun is center and ruler and king in his own system. But as a star,
+he is only one among many stars, some greater, some less than himself.
+From the far siderial heavens he is hardly recognized even as a star
+among the constellations, so faint is his light.
+
+Do the suns which surround us form a system with that which illuminates
+us, as the planets form one round our solar focus, and does our sun
+revolve round an attractive center? Does this center, the point of the
+revolutions of many suns, itself revolve round a preponderating center?
+In a word, is the visible universe organized in one or several systems?
+No Divine revelation comes to instruct men on the mysteries which
+interest them most--their personal or collective destinies. We have
+now, as ever, but science and observation to answer us.
+
+A problem so vast as this is still far from receiving even an
+approximate solution. From whatever point of view we consider it,
+we find ourselves face to face with the infinite in space and time.
+The present aspect of the universe immediately brings into question
+its past and its future state, and then the whole of united human
+learning supplies us in this great research with but a pale light,
+scarcely illuminating the first steps of the dark and unknown road on
+which we are traveling. However, such a problem is worthy of engaging
+our attention, and positive science has already made sufficient
+discoveries in the knowledge of the laws of nature to permit us to
+attempt to penetrate these great mysteries. What is it that the general
+observation of the heavens--what is it that sidereal synthesis teaches
+us on our real situation in infinitude?
+
+[Illustration: A TELESCOPIC FIELD IN THE MILKY WAY.]
+
+In the calm and silent hours of beautiful evenings, what pensive gaze
+is not lost in the vague windings of the Milky Way, in the soft and
+celestial gleam of that cloudy arch, which seems supported on two
+opposite points of the horizon, and elevated more or less in the sky
+according to the place of the observer and the hour of the night? While
+one-half appears above the horizon, the other sinks below it, and if we
+removed the earth, or if it were rendered transparent, we should see
+the complete Milky Way, under the form of a great circle, making the
+whole circuit of the sky. The scientific study of this trail of light,
+and its comparison with the starry population of the heavens, begins
+for us the solution of the great problem.
+
+Let us point a telescope towards any point of this stupendous arch.
+Suddenly hundreds, thousands of stars show themselves in the telescopic
+field, like needle-points on the celestial vault. Let us wait for some
+moments, that our eye may become accustomed to the darkness of the
+background, and the little sparks shine out by thousands. Let us leave
+the instrument pointed motionless towards the same region, and there
+slowly passes before our dazzled vision the distant army of stars. In
+a quarter of an hour we see them appear by thousands and thousands.
+William Herschel counted three hundred and thirty-one thousand in a
+width of 5° in the constellation Cygnus, so nebulous to the naked eye.
+If we could see the whole of the Milky Way pass before us, we should
+see eighteen millions of stars.
+
+This seed-plot of stars is formed of objects individually invisible
+to the naked eye, below the sixth magnitude; but so crowded that they
+appear to touch each other, and form a nebulous gleam which all human
+eyes, directed to the sky for thousands of years, have contemplated and
+admired. Since it is developed like a girdle round the whole circuit of
+the sky, we ourselves must be in the Milky Way. The first fact which
+impresses our mind is, that _our sun is a star of the Milky Way_.
+
+Thought travels fast--faster than a comet, faster than light. A rushing
+comet would, it is believed, take twenty millions of years to cross the
+chasm between the nearest known fixed star and us. Light, flashing
+along at the rate of about one hundred and eighty-six thousand miles a
+second, will perform the same journey in four years and a third. But
+thought can overleap the boundary in less than a single moment.
+
+Each star that we see in the heavens is to our eyesight simply one
+point of light. The brighter stars are said to be of greater magnitude,
+and the fainter stars of lesser magnitude; yet, one and all, they have
+no apparent size. The most powerful telescope, though it can increase
+their brilliancy, can not add to their size. A planet, which to the
+naked eye may look like a star, will, under a telescope, show a disk,
+the breadth of which can be measured or divided; but no star has any
+real, visible disk in the most powerful telescope yet constructed. The
+reason of this is the enormous distance of the stars. Far off as many
+of the planets lie, yet the farthest of them is as a member of our
+household compared with the nearest star.
+
+I have already tried to make clear the fact of their vast distance.
+Light, which comes to us from the sun in eight minutes and a half,
+takes over four and a third years to reach us from Alpha Centauri. From
+this four-years-and-a-third length of journey between Alpha Centauri
+and earth, the numbers rise rapidly to twenty years, fifty years,
+seventy years, even hundreds of years. The distance of most of the
+stars is completely beyond our power to measure. The whole orbit of our
+earth, nay, the whole wide orbit of the far-off Neptune, would dwindle
+down to one single point, if seen from the greater number of the stars.
+
+It used to be believed that, taking the stars generally, there was
+probably no very marked difference in their size, their kind, their
+brightness. Some of course would be rather larger, and others rather
+smaller; still it was supposed that they might be roughly classed as
+formed much on the same scale and the same plan. But doubts are now
+felt about this notion. For a very similar idea used to be held with
+regard to the Solar System. The wonderful variety of form and richness
+in numbers, now known to abound within its limits, are discoveries of
+late years. May not the same variety in kind and size be found also
+among the stars? The more we look into the heavens, the more we find
+that dull, blank uniformity is not to be seen there.
+
+It is the same upon earth. Man builds his little rows of boxlike houses
+side by side, each one exactly like all the rest, or dresses his
+thousand soldiers in coats of the same cut and color, or repeats a neat
+leaf-design hundreds of times on carpets or wall-papers; but God never
+makes two leafs or two blades of grass alike. Wholesale turning out of
+things after one pattern is quite a human idea, not divine.
+
+We know so much about the stars as that some are at least considerably
+larger and some considerably smaller than others. When one star is
+seen to shine brightly, and another beside it shines dimly, we are
+apt to think that the brightest must be the nearest. Yet it is often
+impossible for us to say how much of the difference is owing to the
+greater distance of one or the other, to the greater size of one or
+the other, or to the greater brilliancy of one or the other. In many
+instances we do know enough to be quite sure that there is a great
+difference, not only in the distance of the stars, but in their size,
+their kind, their brightness.
+
+The stars have been lately classed by one or two astronomers into four
+distinct orders or degrees--partly depending on their color. The first
+class is that of the White Suns. These are said to be the grandest and
+mightiest of all. The star Sirius belongs to the order of White Suns.
+Secondly comes the class of Golden Suns. To these blazing furnaces of
+yellow light, second only to the white-light stars, belongs our own
+sun. Thirdly, there are numbers of stars called Variable Stars, the
+light of which is constantly changing, now becoming more, now becoming
+less. Fourthly, there is the class of small Red Suns, about which not
+much is known.
+
+These four orders or divisions do not by any means include all the
+stars, or even all the single stars. Roughly speaking, however, the
+greater number of single stars, and many also of the double stars,
+belong to one or another of the above classes.
+
+When we talk of the different sizes of the different stars, it should
+be plainly understood that we have no means of directly measuring them.
+A point of light showing no disk, no surface, no breadth, can not be
+measured, for there is nothing to measure.
+
+In certain cases we are not entirely without the power of judging. The
+distances of a few of the stars from us have been found out. Knowing
+how far off any particular star is, astronomers are able to calculate
+exactly how bright our own sun would look at that same distance. If
+they find that our sun would shine just as the star in question
+shines, there is some reason for supposing that our sun and the star
+may be of the same size. If our sun would shine more brightly than the
+star shines, there is some reason for supposing that the star may be
+smaller than our sun. If our sun would shine more dimly than the star
+shines, there is some reason for supposing that the star may be larger
+than our sun.
+
+Other matters, however, have to be considered. Suppose we find a star
+at a certain distance shining twice as brilliantly as our own sun would
+shine at that same distance. Naturally, then, we say, That star must be
+much larger than our sun.
+
+The reasoning may be mistaken. We do not know the fact. What if,
+instead of being a much _larger_ sun, it is only a much _brighter_
+sun? This possibly must be allowed for. It has, indeed, been strongly
+doubted by one astronomer, after close study of the sun, whether any
+surface of any star _could_ exceed the surface of our sun in its power
+of light and heat.
+
+But Sirius sheds actually forty-eight times as much light around
+it as does our sun; we are not exactly entitled to say that Sirius
+is forty-eight times as big as the sun, but we can say that Sirius
+is forty-eight times as brilliant or as splendid. In making this
+calculation we have taken a lower determination of the brightness of
+Sirius relatively to the sun than some other careful observations would
+have warranted. It will thus be seen that if there be any uncertainty
+in our result it must only be as to whether Sirius is not really more
+than forty-eight times as bright as the sun.
+
+When we picture to ourselves the star-depths, the boundless reaches of
+heavenly space, with these countless blazing suns scattered broadcast
+throughout, we have not to picture an universe in repose. On the
+contrary, all is life, stir, energy. Just as in the busy whirl of our
+Solar System no such thing as rest is to be found, so also it seems to
+be in the wide universe.
+
+Every star is in motion. “Fixed,” as we call them, they are not fixed.
+Invisible as their movements are to our eyes through immensity of
+distance, yet all are moving. Those silent, placid, twinkling specks of
+light are, in reality, huge, roaring, seething, tumultuous furnaces of
+fire and flame, heat and radiance.
+
+Each, too, is hurrying along his appointed pathway in space. Some move
+faster, some move more slowly. One mile per second; ten miles per
+second; twenty, thirty, forty, fifty miles per second,--thus varying
+are their rates of speed. But whether fast or whether slowly, still
+onward and ever onward they press. Some are rushing towards us, some
+are rushing away from us. Some are speeding to the right, some are
+speeding to the left.
+
+The fine star Arcturus, which any one may admire every evening on the
+prolongation of the tail of the Great Bear, is slowly withdrawing from
+the fixed point where the celestial charts placed it two thousand years
+ago, and is moving towards the southwest. It takes eight hundred years
+to describe a space in the sky equal to the apparent diameter of the
+moon; nevertheless, this displacement was sufficiently perceptible to
+attract attention more than a century and a half ago, for Halley had
+noticed it in 1718, as well as those of Sirius and Aldebaran. However
+slow it may appear at the distance we are from Arcturus, this motion
+is, at a minimum, 1,637 millions of miles a year. Sirius takes 1,338
+years to pass over the same angular space in the sky; at the distance
+of that star this is, at a minimum, 397 millions of miles per annum.
+The study of the proper motions of the stars has made the greatest
+progress in the last half-century, and especially in recent years. All
+the stars visible to the naked eye and a large number of telescopic
+stars show displacements of this kind.
+
+Where are they going? Does any single star ever return to his
+starting-point--wherever that starting-point may have been? Do they
+journey in vast circles or ellipses, round some far-distant center?
+What controls them all? Is it the mighty power of some such center, or
+does each star, by his faint and distant attraction, help to control
+all his brother-stars, to guide them on their appointed path, to
+preserve the delicate balance of a universe?
+
+How little we know about the matter! Only so much we can tell--that
+the controlling and restraining hand of God is over the whole. Whether
+by the attraction of one great center or by the united influences of
+a thousand fainter attractions, he steers each radiant sun upon its
+heavenly path, “upholding all things by the words of his power.” There
+is no blundering, no confusion, no entanglement. All is perfect order,
+calm arrangement, restrained energy.
+
+
+
+
+CHAPTER XXIII.
+
+SOME PARTICULAR SUNS.
+
+
+In the constellation of the Swan there is a little, dim,
+sixth-magnitude star, scarcely to be seen without a telescope. This
+star, 61 Cygni by name, is the first whose distance from us it was
+found possible to determine.
+
+We may think it strange that so faint a star was even attempted.
+Would not astronomers have naturally supposed it to be one of the
+farther-distant stars? No, they did not. For though 61 Cygni showed but
+a dim light, yet his motion--not the daily apparent motion, but the
+real motion as seen from earth--was found to be so much more rapid than
+the motion of most other stars that they rightly guessed 61 Cygni to be
+a rather near neighbor of ours.
+
+Do not misunderstand me, when I speak of a “more rapid motion,” and of
+“rather near neighborhood.” The real rate of 61 Cygni’s rush through
+space is believed to be about forty miles each second, or one thousand
+four hundred and fifty millions of miles each year. All we can perceive
+of this quick motion is that, in the course of three hundred and fifty
+years, 61 Cygni travels over a space in the sky about as long as the
+breadth of the full moon. Little enough, yet very far beyond what can
+be detected in the greater number of even the brightest stars.
+
+Then, again, as to the near neighborhood of this star, 61 Cygni is
+near enough to have his distance measured, and that is saying a good
+deal. Alpha Centauri, the nearest star of which we know in the southern
+heavens, is two hundred and seventy-five thousand times as far distant
+as the sun. But 61 Cygni, the nearest star of which we know in the
+northern heavens, is nearly twice as far away as Alpha Centauri.
+
+[Illustration: CYGNUS.]
+
+We call 61 Cygni a star, for so he appears to common observers. In
+reality, instead of being only one star, the speck of light which
+we call 61 Cygni consists of _two stars_. The two are separated by
+a gap about half as wide again as the wide gap between the sun and
+Neptune. Yet so great is their distance from us that to the naked eye
+the two seem to be one. These two suns would together make a sun only
+about one-third as large as our sun. They differ in size, the quicker
+movements of one showing it to be the smaller; and it is by means of
+their known distance from one another, and their known rate of motion,
+that their size, or rather their weight, can be roughly calculated. Of
+course neither of the two shows any actual measurable disk. So much and
+so little is with tolerable certainty known about this particular pair
+of suns.
+
+Next let us turn to Alpha Centauri--named _Alpha_, the first
+letter of the Greek alphabet, because it is the brightest star in
+the constellation of the Centaur. The second brightest star in a
+constellation is generally called Beta, the third Gamma, the fourth
+Delta, and so on; just as if we were to name them A, B, C, D, in order
+of brightness.
+
+The constellation Centaur lies in the southern heavens, close to the
+beautiful constellation called the Southern Cross, and is invisible in
+the northern hemisphere. Of all the stars shining in the heavens round
+our earth, two only--Sirius and Canopus--show greater brilliancy than
+Alpha Centauri.
+
+As in the case of 61 Cygni, astronomers were led to attempt the
+measurement of Alpha Centauri’s distance, by noticing how much more
+distinct were his movements than the movements of other stars, though
+less rapid both to the eye and in reality than those of 61 Cygni. Alpha
+Centauri’s rate of motion is some thirteen miles each second.
+
+And this, so far as we yet know, is our sun’s nearest neighbor in the
+heavens outside his own family circle.
+
+Strange to say, Alpha Centauri, like 61 Cygni, consists, not of a
+single star, but of a pair of stars. It is a two-sun system--whether or
+no surrounded by planets can not be told. We can only reason from what
+we see to what we do not see. And as God did not form our earth “in
+vain,” and did not form our sun “in vain,” so we firmly believe that he
+did not form “in vain” any one of his myriads of suns scattered through
+space. What is, has been, or will be the particular use of each one,
+it would be rash to attempt to say. But that many among them have,
+like our own sun, systems of worlds revolving round them, we may safely
+consider very probable.
+
+[Illustration: STARS WHOSE DISTANCES ARE BEST KNOWN. (See Table.)]
+
+The two suns of the Alpha Centauri double-star are separated by a
+distance about twenty-two times as great as the distance of the earth
+from the sun, yet to the naked eye they show as a single star. Here
+again one is much smaller than the other; and the smaller revolves
+round the larger in about eighty-five years.
+
+It is believed that the two together would form a sun about twice as
+large and heavy as our sun. This belief is strengthened by the great
+brilliancy of Alpha Centauri. Our own sun, placed at that distance from
+us, would shine only one-third as brightly as he does.
+
+
+STARS WHOSE DISTANCES ARE BEST KNOWN.
+
+  +--+--------------------+----------+------------------+
+  |  |   NAME OF STAR.    |MAGNITUDE.|DISTANCE IN MILES.|
+  +--+--------------------+----------+------------------+
+  | 1| Alpha Centauri,    |   1.0    |  25 trillions.   |
+  | 2| 61 Cygni,          |   5.1    |  43     ”        |
+  | 3| 2,398, Draco,      |   8.2    |  55     ”        |
+  | 4| Sirius,            |   1.0    |  58     ”        |
+  | 5| 9,352, Lacaille,   |   7.5    |  66     ”        |
+  | 6| Procyon,           |   1.3    |  71     ”        |
+  | 7| Lalande, 21,258,   |   8.5    |  74     ”        |
+  | 8| Œltzen, 11,677,    |   9.0    |  74     ”        |
+  | 9| Sigma Draconis,    |   4.7    |  78     ”        |
+  |10| Aldebaran,         |   1.5    |  81     ”        |
+  |11| Epsilon Indi,      |   5.2    |  87     ”        |
+  |12| Œltzen, 17,415,    |   9.0    |  94     ”        |
+  |13| 1,516, Draco,      |   7.0    | 101     ”        |
+  |14| Omicron Eridani,   |   4.4    | 101     ”        |
+  |15| Altair,            |   1.6    | 101     ”        |
+  |16| Bradley, 3,077,    |   5.5    | 101     ”        |
+  |17| Eta Cassiopeiæ,    |   3.6    | 118     ”        |
+  |18| Vega,              |   1.0    | 128     ”        |
+  |19| Capella,           |   1.2    | 174     ”        |
+  |20| Arcturus,          |   1.0    | 204     ”        |
+  |21| Pole Star,         |   2.1    | 215     ”        |
+  |22| Mu Cassiopeiæ,     |   5.2    | 320     ”        |
+  |23| 1,830, Groombridge,|   6.5    | 426     ”        |
+  +--+--------------------+----------+------------------+
+
+This table presents the most trustworthy data which we have yet
+obtained with reference to stellar distances. As a great number of
+attempts have been made on stars which, by their brightness or by the
+magnitude of their proper motion, would appear to be the nearest to us,
+we may believe that the star now considered as the nearest is really
+so, and that there is no other less distant. Thus our sun, a star
+in the immensity, is isolated in infinitude, and _the nearest_ sun
+reigns at twenty-five trillions of miles from our terrestrial abode.
+Notwithstanding its unimaginable velocity of 186,400 miles a second,
+light moves, flies, during four years and one hundred and twenty-eight
+days to come from this sun to us. Sound would take more than three
+millions of years to cross the same abyss. At the constant velocity of
+thirty-seven miles an hour, _an express train starting from the sun
+Alpha Centauri would not arrive here till after an uninterrupted course
+of nearly seventy-five millions of years_.
+
+Here, then, are the nearest suns to us. These stars, twenty-three
+in number, are almost the only ones which have shown a perceptible
+parallax; still the result is very doubtful for the last four, of which
+the parallax is less than a tenth of a second. Attempts have been made
+to ascertain the parallax of all the stars of the first magnitude,
+and the result has been negative for those which are not entered in
+this list. Canopus, Rigel, Betelgeuse, Achernar, Alpha of the Cross,
+Antares, Spica, and Fomalhaut, do not show a perceptible parallax. The
+fine star Alpha Cygni, which shines near 61 Cygni, does not present to
+the most accurate researches any trace of fluctuation: it is, then,
+incomparably more distant than its modest neighbor--at least five
+times, and perhaps twenty times, fifty times, one hundred times beyond
+that. What must be the colossal size and amazing light of these suns,
+of which the distance is greater than three hundred to four hundred
+trillions of miles, and which nevertheless still shine with so splendid
+a brightness!
+
+We did not know the distance of any stars till the year 1840. This
+shows how recent this discovery is; indeed, we have hardly now begun
+to form an approximate idea of the real distances which separate the
+stars from each other. The parallax of 61 Cygni, the first which was
+known, was determined by Bessel, and resulted from observations made at
+Königsberg from 1837 to 1840. Since then, the first figure obtained has
+been corrected by a series of more recent observations.
+
+Such distances are amazing and almost terrifying to the imagination.
+The mind is bewildered and almost overwhelmed when attempting to form a
+conception of such portions of immensity, and feels its own littleness,
+the limited nature of its powers, and its utter incapacity for grasping
+the amplitudes of creation. But though it were possible for us to wing
+our flight to such a distant orb as 61 Cygni, we should still find
+ourselves standing only on the verge of the starry firmament where ten
+thousands of other orbs a thousand times more distant would meet our
+view. We have reason to believe that a space equal to that which we are
+now considering intervenes between most of the stars which diversify
+our nocturnal sky. The stars appear of different magnitudes; but we
+have the strongest reason to conclude that in the majority of instances
+this is owing, not to the difference of their real magnitudes, but to
+the different distances at which they are placed from our globe.
+
+If, then, the distance of a star of the first or second magnitude, or
+those which are nearest to us, be so immensely great, what must be the
+distance of stars of the sixteenth or twentieth magnitude, which can
+be distinguished only by the most powerful telescopes? Some of these
+must be many millions of times more distant than the nearest star whose
+distance now appears to be determined. And what shall we think of the
+distance of those which lie beyond the reach of any telescope that has
+yet been constructed, stretching beyond the utmost limits of mortal
+vision, within the unexplored regions of immensity? Here even the most
+vigorous imagination drops its wing, and owns itself utterly unable to
+penetrate this mysterious and boundless unknown.
+
+Turning now from the sun, whose distance was first measured, and from
+the nearest star with which we are acquainted, let us think about the
+most radiant star in the heavens--Sirius, “the blazing Dog-star of the
+ancients;” named by one astronomer “the king of suns.”
+
+First, as to the color of Sirius. He belongs to the order of “White
+Suns,” and among all the white suns known to us, Sirius ranks as
+chief. There may be many at greater distances far surpassing him in
+size, and weight, and brilliancy; but we can only speak so far as we
+know. Strange to say, Sirius was not always a “white sun;” for ancient
+writers describe him as being, in their days, a _red_ star. This change
+is very singular, and difficult to understand. But Sirius is not the
+only example of the kind. Many alterations in color have been noticed
+as taking place, often in a much shorter space of time. For instance,
+one star, which was a white sun in the days of Herschel, is now a
+golden sun.
+
+Secondly, as to the distance of Sirius. Like a few other stars, Sirius
+lies not quite so far away as to be beyond reach of measurement.
+No base-line upon earth would cause the slightest seeming change of
+position in him; but as our earth journeys round the sun, the line from
+one side of her orbit to the other is found wide enough. A base-line
+of one hundred and eighty-six millions of miles does cause just a tiny
+seeming change.
+
+It is very little even with Alpha Centauri, and with Sirius it is much
+less. The “displacement” of Sirius is so slight that to measure his
+distance with exactness is impossible. Sirius lies more than twice as
+far away from earth as Alpha Centauri. To reach Sirius, the straight
+line between earth and sun must be repeated six hundred and twenty-six
+thousand times. Light, which reaches us from the sun in eight minutes
+and a half, and from Alpha Centauri in four years and a third, can not
+reach us from Sirius in less than nine years.
+
+Thirdly, as to the size of Sirius. Here, of course, we are in
+difficulties. Radiantly as Sirius shines on a clear night, and dazzling
+as he looks through a powerful telescope, he shows no real disk or
+round surface, but only appears as one point of brilliant light.
+Some believe him to be much the same size as our sun, while others
+believe him to be very much larger. But we have no certain ground to
+rest upon. The only safe method of calculating the probable size--or,
+rather, weight--of a star is through the discovery of a companion,
+and a knowledge of its distance from the chief star, and its time of
+revolution round the chief star.
+
+Fourthly, as to the motions of Sirius--not his nightly apparent
+movement, caused by the earth’s turning on her axis, but his real
+journey through space. For a long while it was only possible to observe
+the movements of a star when the star was traveling _sideways_ to us
+across the sky. A star coming straight towards us, or going straight
+away from us, would seem to be at rest. Lately, however, by means
+of that remarkable instrument, the spectroscope, it has been found
+possible to measure the motions of stars coming towards or going away
+from us. This is possible as yet only in a few scattered cases, but
+among those few is the brilliant Sirius.
+
+The sideways motion of Sirius had been known before. It now appears
+that he does not move exactly sideways to us, but is rushing away in a
+slanting direction at the rate of thirty miles each second, or about
+one thousand millions of miles a year.
+
+How many millions upon millions of miles Sirius must now be farther
+from us than in the days of the ancients! Yet he shines still, the most
+brilliant star in the sky. So small a matter are all those millions of
+miles, compared with the whole of his vast distance from us, that we do
+not perceive any lessening of light.
+
+It is an interesting fact that while Sirius is moving away from us,
+we are also moving away from him. Our “first station ahead,” in the
+constellation Hercules, lies exactly in the opposite direction from
+Sirius. But the sun does not move so fast as Sirius. He is believed
+to accomplish only about one hundred and fifty millions of miles each
+year, drawing all his planets with him.
+
+Fifthly, has Sirius a family, or system, like that of our sun?
+Why not? Common sense and reason alike answer with a “Probably,
+yes”--not only about Sirius, but about other stars also. No doubt
+the systems--the number, size, weight, speed, distance, and kind of
+planets--differ very greatly. No doubt there are boundless varieties of
+beauty and grandeur.
+
+But that our sun should be the head of so wonderful and complex a
+system, that his rays should be the source of life and heat to so many
+dependents, and that all the myriads of suns besides should be mere
+solitary lamps shining into empty space, warming, lighting, controlling
+_nothing_, is an idea scarcely to be looked in the face.
+
+Of course, there may be other and different uses for some of these
+suns, beyond our understanding. We must not be positive in the matter.
+It seems, however, pretty certain that Sirius at least is not a
+solitary, unattended sun.
+
+Astronomers, carefully watching his movements, were somewhat perplexed.
+As with Uranus, the attraction of a heavy body beyond was suspected
+from the nature of the planet’s motions, so it happened again with the
+far more distant Sirius. Astronomers could only explain his movements
+by supposing the attraction of some large and near satellite. No one
+knew anything about such a satellite, but it was felt that one must
+exist.
+
+Nearly twenty years had elapsed after Bessel had predicted the
+disturber of Sirius before the telescopic discovery which confirmed it
+was made. The circumstances under which that discovery was made are
+not, indeed, so dramatic as those which attended the discovery of
+Neptune, but yet they have an interest of their own. In February, 1862,
+Alvan Clark & Sons, the celebrated telescope-makers, of Cambridge,
+Massachusetts, were completing a superb eighteen-inch object-glass for
+the Chicago Observatory. Turning the instrument on Sirius, for the
+purpose of trying it, the practiced eye of Alvan Graham Clark, the
+son, soon detected something unusual, and he exclaimed, “Why, father,
+the star has a companion!” The father looked, and there was a faint
+companion due east from the bright star, and distant about ten seconds
+of a degree. This was exactly the predicted direction of the companion
+of Sirius, and yet the observers knew nothing of the prediction. As
+the news of this discovery spread, many great telescopes were pointed
+on Sirius; and it was found that when observers knew exactly where to
+look for the object, many instruments would show it. The new companion
+star to Sirius lay in the true direction, and it was now watched with
+the keenest interest, to see whether it also was moving in the way
+it should move,--if it were really the body whose existence had been
+foretold. Four years of observation showed that this was the case, so
+that hardly any doubt could remain that the telescopic discovery had
+been made of the star which had caused the inequality in the motion of
+Sirius.
+
+It is certainly a very remarkable fact that, out of the thousands of
+stars with which the heavens are adorned, no single star has yet been
+found which certainly shows an appreciable disk in the telescope. We
+are aware that some skillful observers have thought that certain small
+stars do show disks; but we may lay this aside, and appeal only to the
+ordinary fact that our best telescopes turned on the brightest stars
+show merely glittering points of light, so hopelessly small as to elude
+our most delicate micrometers. The ideal astronomical telescope is,
+indeed, one which will show Sirius, or any other bright star, as nearly
+identical as possible with Euclid’s definition of a point, being that
+which has no parts and no magnitude.
+
+Lastly, what is Sirius made of? The late discovery of spectrum
+analysis, or of the instrument called the spectroscope, helps us here.
+A little further explanation on this subject will be given later. It
+may be observed in passing that before the said discovery, astronomers
+can scarcely be asserted to have known with any certainty that stars
+were suns. They could, indeed, be sure that at the vast distances of
+the fixed stars no bodies, shining by merely reflected light, could
+possibly be visible to us. But there knowledge stopped.
+
+Now we can say more. Now the spectroscope, by breaking up and dividing
+for us the slender ray of light traveling from each star, has shown to
+us something of the nature of the stars. Now we know that the stars,
+like our sun, are burning bodies, surrounded by atmospheres full of
+burning gas.
+
+It has even been found out that in Sirius there are large quantities of
+sodium and magnesium, besides other metals, and an abundant supply of
+hydrogen gas.
+
+
+
+
+CHAPTER XXIV.
+
+DIFFERENT KINDS OF SUNS.
+
+
+Various in kind, various in size, various in color, various in
+position, various in motion, are the myriad suns scattered through
+space. So far are they from being formed on the same plan, turned out
+on the same model, that it may with reason be doubted whether any two
+stars could be found exactly alike. Why should we expect to find them
+so? No two oak-leaves, no two elm-leaves, precisely alike, are to be
+found upon earth.
+
+So some stars are large, some are small. Some are rapid in movement,
+some are slow. Some are yellow, some white, some red, green, blue,
+purple, or gray. Some are single stars; others are arranged in pairs,
+trios, quartets, or groups. Some appear only for a time, and then
+disappear altogether. Others are changeful, with a light that regularly
+waxes and wanes in brightness.
+
+We have now to give a little time and thought to variable stars and
+temporary stars; afterwards to double stars and colored stars. There
+are many stars which pass through gradual and steady changes--first
+brightening, then lessening in light, then brightening again. One such
+star is to be seen in the constellation of the Whale. It is named
+“Mira,” or “The Marvelous,” and the time in which its changes take
+place extends to eleven months. For about one fortnight it is a star
+of the second magnitude. Through three months it grows slowly more and
+more dim, till it becomes invisible, not only to the naked eye, but
+through ordinary telescopes. About five months it remains thus. Then
+again, during three months, it grows brighter and brighter, till it is
+once more a second-magnitude star, and after a fortnight’s pause begins
+anew to fade.
+
+At its maximum, this star is yellow; when it is faint, it is reddish.
+Spectrum analysis shows in it a striped spectrum of the third type,
+and when its light diminishes it preserves all the principal bright
+rays reduced to very fine threads. The most plausible explanation
+of this variability is to suppose that it periodically emits vapors
+similar to the eruptions observed in the solar photosphere. Instead
+of its periodicity being like that of the sun--eleven years and
+hardly perceptible--this variation of the sun of the Whale is three
+hundred and thirty-one days and very considerable. It is subject to
+oscillations and irregularities similar to those which we remark in our
+sun. Of all the variable stars, this is the easiest to observe, and it
+has been known for nearly three hundred years.
+
+The most celebrated of all the variable stars is that known as Algol,
+in the constellation of Perseus. This star is very conveniently placed
+for observation, being visible every night in the Northern Hemisphere,
+and its wondrous and regular changes can be observed without any
+telescopic aid. Every one who desires to become acquainted with the
+great truths of astronomy should be able to recognize this star, and
+should have also followed it during one of its periods of change.
+Algol is usually a star of the second magnitude; but in a period
+between two or three days--or, more accurately, in an interval of two
+days, twenty hours, forty-eight minutes, and fifty-five seconds--its
+brilliancy goes through a most remarkable cycle of variations. The
+series commences with a gradual decline of the star’s brightness,
+which, in the course of three or four hours, falls from the second
+magnitude down to the fourth. At this lowest stage of brightness, Algol
+remains for about twenty minutes, and then begins to increase, until
+in three or four hours it regains the second magnitude, at which it
+continues for about two days, thirteen hours, when the same series
+commences anew. It seems that the period required by Algol to go
+through its changes is itself subject to a slow, but certain variation.
+
+Another variable star, Betelgeuse in Orion, undergoes its variations in
+about two hundred days; while yet another, Delta Cephei, takes only six
+days. Our own sun is believed to be in some slight degree a variable
+star, passing through his changes in eleven years. When the sun-spots
+are most numerous, he would probably appear, if seen from a great
+distance, more dim than when there are few or none of them.
+
+Sometimes a star is not merely variable. Stars have appeared for a
+brief space, and then utterly vanished. They are then named Temporary
+Stars. Whether such a star really does go out of existence, or whether
+it merely becomes too dim to be seen; whether the furnace-fires are
+extinguished, and the glowing sun changes into a dark body, or whether
+it merely turns a dark side towards us for a very long period,--these
+are questions we can not answer.
+
+An extraordinary specimen of a temporary star was seen in 1572. It was
+not a comet, for it had no coma or tail, and it never moved from its
+place. The brightness of the star was so great as to surpass Sirius and
+Jupiter, and to equal Venus at her greatest brilliancy. Nay, it must
+have surpassed even Venus, for it was plainly visible at midday in a
+clear sky. Gradually the light faded and grew more dim, till at length
+it entirely disappeared. As it lessened in brilliancy, it also changed
+in color, passing from white to yellow, and from yellow to red. This
+curiously agrees with the three tints of the first, second, and fourth
+orders of suns, as lately classified.
+
+This star was observed by Tycho Brahe, who gives the following curious
+account:
+
+“One evening, when I was contemplating, as usual, the celestial
+vault, whose aspect was so familiar to me, I saw, with inexpressible
+astonishment, near the zenith, in Cassiopeia, a radiant star of
+extraordinary magnitude. Struck with surprise, I could hardly believe
+my eyes. To convince myself that it was not an illusion, and to obtain
+the testimony of other persons, I called out the workmen employed in my
+laboratory, and asked them, as well as all passers-by, if they could
+see, as I did, the star, which had appeared all at once. I learned
+later on that in Germany carriers and other people had anticipated the
+astronomers in regard to a great apparition in the sky, which gave
+occasion to renew the usual railleries against men of science (as with
+comets whose coming had not been predicted).
+
+“The new star was destitute of a tail; no nebulosity surrounded it;
+it resembled in every way other stars of the first magnitude. Its
+brightness exceeded that of Sirius, of Lyra, and of Jupiter. It could
+only be compared with that of Venus when it is at its nearest possible
+to the earth. Persons gifted with good sight could distinguish this
+star in daylight, even at noonday, when the sky was clear. At night,
+with a cloudy sky, when other stars were veiled, the new star often
+remained visible through tolerably thick clouds. The distance of
+this star from the other stars of Cassiopeia, which I measured the
+following year with the greatest care, has convinced me of its complete
+immobility. From the month of December, 1572, its brightness began to
+diminish; it was then equal to Jupiter. In January, 1573, it became
+less brilliant than Jupiter; in February and March, equal to stars of
+the first order; in April and May, of the brightness of stars of the
+second order. The passage from the fifth to the sixth magnitude took
+place between December, 1573, and February, 1574. The following month
+the new star disappeared without leaving a trace visible to the naked
+eye, having shone for seventeen months.”
+
+These circumstantial details permit us to imagine the influence
+which such a phenomenon must have exercised on the minds of men. Few
+historical events have caused so much excitement as this mysterious
+envoy of the sky. It first appeared on November 11, 1572. General
+uneasiness, popular superstition, the fear of comets, the dread of the
+end of the world, long since announced by the astrologers, were an
+excellent setting for such an apparition. It was soon announced that
+the new star was the same which had led the wise men to Bethlehem,
+and that its arrival foretold the return of the Messiah and the last
+judgment. For the hundredth time, perhaps, this sort of prognostication
+was recognized as absurd. It did not, however, prevent the astrologers
+from being believed, twelve years later, when they announced anew the
+end of the world for the year 1588; these predictions exercised the
+same influence on the public mind.
+
+After the star of 1572 the most celebrated is that which appeared
+in October, 1604, in Serpentarius, and which was observed by two
+illustrious astronomers, Kepler and Galileo. As happened with the
+preceding, its light imperceptibly faded. It remained visible for
+fifteen months, and disappeared without leaving any traces. In 1670
+another temporary star, blazing out in the head of the Fox (Vulpecula),
+showed the singular phenomenon of being extinguished and reviving
+several times before it completely vanished. We know of _twenty-four_
+stars which, during the last two thousand years, have presented a
+sudden increase of light; have been visible to the naked eye, often
+brilliant; and have then again become invisible. The last apparitions
+of this kind happened before our eyes in 1866, 1876, 1885, and 1892,
+and spectrum analysis enabled us to ascertain, as we have seen, that
+they were due to veritable combustion--a fire caused by a tremendous
+expansion of incandescent hydrogen, and to phenomena analogous to
+those which take place in the solar photosphere. A rather curious fact
+about these stars is, that they do not blaze out indifferently in any
+point of the sky, but in rather restricted regions, chiefly in the
+neighborhood of the Milky Way.
+
+Many other instances have been known, beside those referred to, of
+variable and temporary stars.
+
+There are two distinct kinds of double-stars. First, we have those
+which merely seem to be double, because one lies almost directly behind
+the other, though widely distant from it. Just as a church-tower,
+two miles off, may appear to stand close side by side with another
+church-tower two and a half miles off, though they are in fact
+separated. Secondly, we have the real systems of two suns belonging to
+one another; the smaller moving round the larger, or more correctly
+both traveling round one central point called the center of gravity,
+the smaller having the quicker rate of motion.
+
+[Illustration: LYRA]
+
+Alpha Centauri and 61 Cygni have been already described, as examples of
+true double-stars. In the constellation Lyra a marked instance is to be
+seen. The brightest star in the Lyre is Vega, and near Vega shines a
+tiny star, which to people with particularly clear sight has sometimes
+rather a longish look. If you examine this star through an opera-glass,
+you find it to consist of two separate stars. But if you get a more
+powerful telescope, and look again, you will find that _each star_ of
+the couple actually consists of _two_ stars. The four are not at equal
+distances. Two points of light seemingly close together are parted by
+a wide gap from two other points equally close together. These four
+stars are believed to have a double motion. Each of the separate pairs
+revolves by itself, the two suns traveling round one center; and in
+addition to this the two _couples_ of suns probably perform a long
+journey round another center common to them all.
+
+Many thousands of double stars have been discovered; and a large number
+of these are now known to be, not merely two distinct suns lying in the
+same line of sight, but two brother-suns, each probably the center of
+his own system of planets.
+
+We have not only to consider the number of suns, though of simple
+numbers more yet remains to be said. Attention must also be given to
+the varying colors of different stars; for all suns in the universe are
+not made after the model of our sun. All suns are not yellow.
+
+So far as single stars are concerned, colors seem rather limited. White
+stars, golden or orange stars, ruby-red stars, placed alone, are often
+seen; but blue stars, green stars, gray stars, silver stars, purple
+stars, are seldom if ever visible to the naked eye, or known to exist
+as single stars.
+
+Take a powerful telescope and examine star-couples, and a very
+different result you will find. Not white, yellow, and red alone, but
+blue, purple, gray, green, fawn, buff, silvery white, and coppery hues,
+will delight you in turn. As a rule, when the two stars of a couple
+are alike in color, they are either white, or yellow, or red. Also in
+the case of double-stars of different colors, the larger of the two is
+almost invariably white or some shade of yellow or red.
+
+There are, however, exceptions to all such rules. Blue stars are almost
+never seen alone, and as one of a pair the blue star is generally, if
+not invariably, the smaller. But instances are known of double-stars,
+both of which are blue; and one group in the southern heavens is
+entirely made up of a multitude of bluish suns.
+
+It is when we come to consider double-stars of two colors that the
+most striking effects are found. Now and then the two suns are nearly
+the same in size; but more commonly one is a good deal larger than the
+other. This is known by the brighter light of the largest, and the more
+rapid movements of the smallest. The lesser star is often only small by
+comparison, and may be in reality a very goodly and brilliant sun.
+
+Among nearly six hundred “doubles” examined by one astronomer, there
+were three hundred and seventy-five in which the two stars were of one
+color, generally white, yellow, orange, or red. The rest were different
+in tint, the difference between the two suns in about one hundred and
+twenty cases being very marked.
+
+For instance, a red “primary,” as the larger star is called, will
+be seen with a small green satellite; or a white primary will have
+a little brother-sun of purple, or of dark ruby, or of light red.
+Sometimes the larger sun is orange, the companion being purple or
+dark blue. Again, the chief star will be red with a blue satellite,
+or yellow with a green satellite, or orange with an emerald satellite,
+or golden with a reddish-green satellite. We hear of golden and lilac
+couples, of cream and violet pairs, of white and green companions. But,
+indeed, the variety is almost endless.
+
+[Illustration: CONSTELLATIONS IN THE NORTHERN HEMISPHERE.]
+
+There may be worlds circling around these suns--worlds, perhaps, with
+living creatures on them. We know little about how such systems of suns
+and worlds may be arranged. Probably each sun would have his own set
+of planets, and both suns with their planets would travel round one
+central point. Perhaps, where the second sun is much the smallest, it
+might occasionally be like a big blazing satellite among the planets--a
+kind of burning Jupiter-sun to the chief sun.
+
+Among colored stars, single and double, a few may be mentioned by name
+as examples. Sirius, as already observed, is a brilliant white sun; and
+brilliant white also are Vega, Altair, Regulus, Spica, and many others.
+Capella, Procyon, the Pole-star, and our own sun, are examples of
+yellow stars. Aldebaran, Betelgeuse, and Pollux, are ruby-red. Antares
+is a red star, with a greenish “scintillation” or change of hue in its
+twinkling. A tiny green sun belonging to this great and brilliant red
+sun has been discovered. Some have called Antares “the Sirius of Red
+Suns.”
+
+It is during the fine nights of winter that the constellation Taurus,
+or The Bull, with the star Aldebaran marking its eye, shines in
+the evening above our heads. No other season is so magnificently
+constellated as the months of winter. While nature deprives us of
+certain enjoyments in one way, it offers us in exchange others no less
+precious. The marvels of the heavens present themselves from Taurus and
+Orion in the east to Virgo and Boötes on the west. Of eighteen stars
+of the first magnitude, which are counted in the whole extent of the
+firmament, a dozen are visible from nine o’clock to midnight, not to
+mention some fine stars of the second magnitude, remarkable nebulæ,
+and celestial objects well worthy of the attention of mortals. It is
+thus that nature establishes an harmonious compensation, and while it
+darkens our short and frosty days of winter, it gives us long nights
+enriched with the most opulent creations of the sky. The constellation
+of Orion is not only the richest in brilliant stars, but it conceals
+for the initiated treasures which no other is known to afford. We might
+almost call it the California of the sky.
+
+To the southeast of Orion, on the line of the Three Kings, shines
+the most magnificent of all the stars, _Sirius_, or _Alpha_ of the
+constellation of the Great Dog. This constellation rises in the evening
+at the end of November, passes the meridian at midnight at the end of
+January, and sets at the end of March. It played the greatest part in
+Egyptian astronomy, for it regulated the ancient calendar. It was the
+famous Dog Star; it predicted the inundation of the Nile, the summer
+solstice, great heats and fevers; but the precession of the equinoxes
+has in three thousand years moved back the time of its appearance by
+a month and a half; and now this fine star announces nothing, either
+to the Egyptians who are dead or to their successors. But we shall see
+farther on what it teaches us of the grandeur of the sidereal universe.
+
+The _Little Dog_, or Procyon, is found above the Great Dog and below
+the Twins (Castor and Pollux), to the east of Orion. With the exception
+of Alpha Procyon, no brilliant star distinguishes it.
+
+The two double-stars, 61 Cygni and Alpha Centauri, are formed each of
+two orange suns.
+
+In the Southern Cross there is a wonderful group of stars, consisting
+of about one hundred and ten suns, nearly all invisible to the naked
+eye. Among the principal stars of this group, which Sir John Herschel
+described as being, when viewed through a powerful telescope, like “a
+casket of variously-colored precious stones,” are two red stars, two
+bright green, three pale green, and one of a greenish blue.
+
+The splendor of these natural illuminations can hardly be conceived
+by our terrestrial imagination. The tints which we admire in these
+stars from here can give but a distant idea of the real value of their
+colors. Already, in passing from our foggy latitudes to the limpid
+regions of the tropics, the colors of the stars are accentuated, and
+the sky becomes a veritable casket of brilliant gems. What would it be
+if we could transport ourselves beyond the limits of our atmosphere?
+Seen from the moon, these colors would be splendid. Antares, Alpha
+Herculis, Pollux, Aldebaran, Betelgeuse, Mars, shine like rubies; the
+Polar Star, Capella, Castor, Arcturus, Procyon, are veritable celestial
+topazes; while Sirius, Vega, and Altair are diamonds, eclipsing all
+by their dazzling whiteness. How would it be if we could approach the
+stars so as to perceive their luminous disks, instead of merely seeing
+brilliant points destitute of all diameter?
+
+Blue days, violet days, dazzling red days, livid green days! Could the
+imagination of poets, could the caprice of painters, picture on the
+palette of fancy a world of light more astounding than this? Could the
+mad hand of the chimera, throwing on the receptive canvas the strange
+lights of its fancy, erect by chance a more astonishing edifice?
+
+
+
+
+CHAPTER XXV.
+
+GROUPS AND CLUSTERS OF SUNS.
+
+
+We have been thinking a good deal about single stars and double stars,
+as seen from earth. Now we have to turn our attention to groups,
+clusters, _masses_ of stars, in the far regions of space.
+
+Have you ever noticed on a winter night, when the sky was clear and
+dotted with twinkling stars, a band of faintly-glimmering light
+stretching across the heavens from one horizon to the other? The band
+is irregular in shape, sometimes broader, sometimes narrower; here more
+bright, there more dim. If you were in the Southern Hemisphere you
+would see the same soft belt of light passing all across the southern
+heavens. This band or belt is called the Milky Way.
+
+But what is the Milky Way? It is made up of stars. So much we know.
+As the astronomer turns his telescope to the zone of faintly-gleaming
+light, he finds stars appearing behind stars in countless multitudes;
+and the stronger his telescope, the more the white light changes into
+distant stars.
+
+Our sun we believe to be one of the stars of the Milky Way; merely
+one star among millions of stars; merely one golden grain among the
+millions of sparkling gold-dust grains scattered lavishly through
+creation. Scattered, not recklessly, not by chance, but placed,
+arranged, and guided each by its Maker’s upholding hand.
+
+The Milky Way, or the Galaxy, as it has been called, has great interest
+for astronomers. Many have been the attempts made to discover its
+actual size, its real shape, how many stars it contains, how far
+it extends; but to all such questions the only safe answers to be
+returned are fenced around with “perhaps” and “may be.” There are many
+very remarkable clusters of stars to be seen in the heavens--some
+few visible as faint spots of light to the naked eye, though the
+greater number are only to be seen through a telescope. Either with
+the naked eye, or in telescopes of varying power, they show first as
+mere glimmers of light, which, viewed with a more powerful telescope,
+separate into clusters of distant stars.
+
+[Illustration: A CLUSTER OF STARS IN CENTAURUS.]
+
+The most common shape of these clusters is globular--to the eye
+appearing simply round. Stars gather densely near the center, and
+gradually open out to a thin scattering about the edge. Thousands of
+suns are often thus collected into one cluster.
+
+The clusters are to be seen in all parts of the sky; but the greater
+number seem to be gathered into the space covered by the Milky Way and
+by the famous south Magellanic Clouds.
+
+Some of them are beautifully colored; as, for instance, a cluster in
+Toucan, not visible from England, the center of which is rose-colored,
+bordered with white. No doubt it contains a large number of bright red
+suns, surrounded by a scattering of white suns.
+
+It used to be supposed that many of these clusters were other vast
+gatherings or galaxies of stars, like the Milky Way, lying at enormous
+distances from us. This now seems unlikely. The present idea rather is,
+that each cluster, in place of being another “Milky Way” of millions of
+widely-scattered suns, is one great _star-system_, consisting indeed
+of thousands of suns, but all moving round one center. Probably most
+of these clusters are themselves a part of the collection of stars to
+which our sun belongs.
+
+If this be so, and if worlds are traveling among the suns--as may well
+be, since they are doubtless quite far enough apart for each sun to
+have his own little or great system of planets--what sights must be
+seen by the inhabitants of such planets!
+
+We do not indeed know the distance between the separate suns of
+a cluster, which may be far greater than appears to us. But if
+astronomers calculate rightly, they are near enough together to shed
+bright light on all sides of a planet revolving in their midst. The
+said planet might perhaps not have within view a single sun equal in
+apparent size to our sun as seen from earth; yet thousands of lesser
+suns, shining brightly in the firmament night and day, would cause a
+radiance which we never enjoy.
+
+No, not _night_. In such a world there could be no night. Worlds in the
+midst of a star-cluster must be regions of perpetual day. No night, no
+starry heaven, no sunrise lights or sunset glories, no shadow mingling
+with sunshine, but one continual, ceaseless blaze of brightness. We can
+hardly picture, even in imagination, such a condition of things.
+
+[Illustration: THE GREAT NEBULA IN ANDROMEDA, COMPARED WITH SIZE OF THE
+SOLAR SYSTEM.]
+
+Besides star-clusters there are also nebulæ. The word _nebula_ comes
+from the Latin word for “cloud,” and the nebulæ are so named from their
+cloudlike appearance.
+
+It is not easy to draw a line of clear division between nebulæ and
+distant star-clusters; for both have at first sight the same dim,
+white, cloudy look. In past days the star-clusters were included
+by astronomers under the general class of nebulæ. And as with the
+star-clusters, so with many of the nebulæ, the more powerful telescopes
+of modern days have shown them to be great clusters, or systems, or
+galaxies of stars, at vast distances from us.
+
+It was supposed with the nebulæ, as with some of the star-clusters,
+that they were other “Milky Ways” of countless stars, far beyond the
+outside boundaries of our Milky Way. This may still be true of some or
+many nebulæ, but certainly not of all.
+
+For there are different kinds of nebulæ. Some may, as just said, be
+vast gatherings of stars lying at distances beyond calculation, almost
+beyond imagination. Others appear rather to be clusters of stars, like
+those already described, probably situated in our own galaxy of stars.
+There is also a third kind of nebula. Many nebulæ, once supposed to
+be clusters of stars, having been lately examined by means of the
+spectroscope, are found to be enormous masses of glowing gas, and not
+solid bodies at all.
+
+The number of nebulæ known amounts to many thousands. They are
+commonly divided into classes, according to their seeming shape. There
+are nebulæ of regular form, and nebulæ of irregular form. There are
+circular nebulæ, oval nebulæ, annular nebulæ, conical nebulæ, cometary
+nebulæ, spiral nebulæ, and nebulæ of every imaginable description.
+These shapes would no doubt entirely change, if we could see them
+nearer; and indeed, even in more powerful telescopes, they are often
+found to look quite different. While on the subject of clusters and
+nebulæ, mention should be made of the famous Magellanic Clouds in the
+southern heavens. Sometimes they are called the Cape Clouds. They
+differ from other nebulæ in many points, and more particularly in their
+apparent size. The Great Cloud is about two hundred times the size of
+the full moon, while the Small Cloud is about one-quarter as large. In
+appearance they are not unlike two patches of the Milky Way, separated
+and moved to a distance from the main stream.
+
+These clouds are surrounded by a very barren portion of the heavens,
+containing few stars; but in themselves they are peculiarly rich.
+Seen through a powerful telescope, they are found to abound with
+stars. The Greater Cloud alone contains over six hundred from the
+seventh to the tenth magnitudes, countless tiny star-points of lesser
+magnitudes, star-clusters of all descriptions, and nearly three hundred
+nebulæ,--all crowded into this seemingly limited space.
+
+Among many famous nebulæ, the one in Orion and the one in Andromeda may
+be particularly mentioned. The size of the latter, as compared with the
+size of our Solar System, is shown in the cut of this nebula. On the
+hypothesis of a complete resolvability into stars, the mind is lost in
+numbering the myriads of suns, the agglomerated individual lights of
+which produce these nebulous fringes of such different intensities.
+What must be the extent of this universe, of which each sun is no more
+than a grain of luminous dust!
+
+
+
+
+CHAPTER XXVI.
+
+THE PROBLEM OF SUN AND STAR DISTANCES.
+
+
+One question had long occupied the minds of scientific men without the
+finding of any satisfactory answer, and this was the distance of the
+sun from our earth.
+
+At length the sun had fully gained his rightful position in the minds
+of men as center and controller of the Solar System, and earth was
+fully dethroned from her old false position. In point of fact, the sun
+had gained _more_ than his rightful position; since he was now looked
+upon very much as the earth had been formerly looked upon; since he
+was regarded practically as the motionless Universe-Center. The earth
+might and did move--people had grown used to that idea--but the sun,
+at all events, was fixed. The sun, beyond turning upon his axis, was
+motionless.
+
+Still, as to the true distance of the sun from ourselves, ignorance
+reigned. Tycho Brahe had made a great advance on earlier notions by
+placing the light-giver 4,000,000 miles away in imagination. Kepler,
+a quarter of a century later, increased this to 14,000,000. Galileo
+afterwards reverted to the 4,000,000. All this, however, was sheer
+guesswork.
+
+Not till well on in the seventeenth century did Cassini make a
+definite attempt at actual measurement of the sun’s distance, and this
+attempt gave as a result some 82,000,000 miles--not far removed from
+the truth. But at the same period other observers gave results of
+41,000,000 and 136,000,000; so for years the question still remained
+swathed in mist. Better modes and better instruments were required
+before it could receive settlement.
+
+The measurement of the distance of objects a good way off is by means
+of their “parallax,” or the apparent change in their position when
+viewed from two different points at some distance from each other. To
+this method of calculating distance we have already referred.
+
+This kind of measurement of distances is not confined to our earth’s
+surface alone. The distances of bright bodies in the heavens may be
+calculated after just the same method, provided only that the heavenly
+body is not too far distant to be made to change its seeming position
+in the sky.
+
+Suppose you wished to find out how far off the moon is. You would have
+to make your observation of the moon’s exact position in the sky--of
+just that spot precisely where she is to be seen among heavenly scenery
+at a particular moment; and you would have to get somebody else to make
+a similar observation, at the same time, from some other part of earth,
+at a good distance from your post.
+
+There are no hills or woods in the sky for the moon to be seen against;
+but there are plenty of stars, bright points of light far beyond the
+moon. If you look at her from one place, and your friend looks at her
+from another place a good way off, there will be a difference in your
+two “views.” You will see her very close to certain stars; and your
+friend will see her not quite so close to those stars, but closer to
+others. This difference of view would give the moon’s parallax.
+
+If your observation were very careful, very exact, and if you had
+the precise distance between the spot where you stood, and the spot
+where your friend stood,--then, from that base-line, and from the two
+angles formed by its junction with the lines from the two ends of it
+straight to the moon, you might reckon how many miles away the moon is.
+The greater the distance between the two places of observation, the
+better,--as, for instance, at Greenwich and the Cape of Good Hope.
+
+Practically, this is not nearly so simple a matter as it may sound,
+because our earth is always on the move, and the moon herself is
+perpetually journeying onward. All such motions have to be most
+scrupulously allowed for. So the actual measurement of moon-distance
+requires a great deal of knowledge and of study. Many other
+difficulties and complications besides these enter into the question,
+and have to be overcome.
+
+Now, the sun is very much farther away than the moon, and the
+stumbling-blocks in the way of finding out his distance become
+proportionately greater and more numerous. To observe him from two
+parts of England, or from two parts of Europe, would give him no
+parallax. That is to say, there would be no change of position on his
+part apparent to us.
+
+I do not say that there would be no change at all; but only that it
+would be so minute as to be quite unseen by human eyes, even with the
+help of most careful and accurate measurement. A very long base-line
+is needed to make the sun distinctly appear to change his position
+ever so little. Only the very longest base-line which can be found
+on earth will do for this,--nothing less than the earth’s whole
+diameter of nearly eight thousand miles. And I think you will see that
+the success of the calculation would then depend, not alone on most
+careful observation from two posts at the opposite sides of earth; not
+alone on mathematical gifts and powers of close reckoning; but also,
+essentially, on a true knowledge of our earth’s diameter; that is, of
+_the exact length of the base-line_ from which the whole calculation
+would have to be made, and upon which the answer would largely depend.
+
+For a long while the earth’s diameter was not well known. As time
+went on, fresh measurements were again and again made of different
+portions of earth’s surface, fresh calculations following therefrom;
+and gradually clear conclusions were reached. A very important matter
+it was that they should be reached; for the semi-diameter of our earth
+has been adopted as a “standard measure” for the whole universe; and
+the slightest error in that standard measure would affect all after
+calculations.
+
+When actual observations of sun-distance came to be made, innumerable
+difficulties arose. Foremost stood the huge amount of that distance.
+This made precise observations more difficult; and at the same time it
+made every mistake in observation so much the worse. A little mistake
+in observing the moon might mean only a hundred miles or so wrong in
+the answer; but a mistake equally small in observing the sun would lead
+to an error of many millions of miles.
+
+Again, to observe the sun’s exact position among the stars, as with the
+moon, was not possible; because when the sun is visible, the stars are
+not visible. Then, too, the dazzling brightness of the sun balked the
+needed exactitude.
+
+Halley had a brilliant thought before he died. He could not carry
+it out himself, but he left it to others as a legacy; that was, by
+observing the transit of Venus from two different points on the earth’s
+surface. At his suggestion, on the first opportunity--which was not
+till after his death--the above mode was tried of measuring the sun’s
+distance.
+
+A certain observer, stationed on one part of earth, saw the tiny dark
+body of Venus take one particular line across the sun’s bright face.
+Another observer, standing on quite another and a far-off part of
+earth, saw the little dark body take quite another line across the
+sun’s bright face. Not that there were two little dark bodies, but that
+the one body was seen by different men in different places.
+
+From these separate views of the path of Venus across the face of the
+sun, in connection with what was already known of the earth’s diameter,
+and therefore of the length of base-line between the two places, the
+distance of the sun was reckoned to be about 95,000,000 miles.
+
+Since that date many fresh attempts have been made, and errors have
+been set right. Mercury as well as Venus has been used in this matter,
+and other newer modes of measurement have also been successfully tried.
+We know now, with tolerable accuracy, that the sun’s greater distance
+from earth is between 92,000,000 and 93,000,000 miles. A curious
+illustration of sun-distance has been offered by one writer. Sound and
+light, heat and sensation, all require _time_ for journeying. When a
+child puts his finger into a candle-flame, he immediately shrieks with
+pain. Yet, quickly as the cry follows the action, his brain is not
+really aware of the burn until a certain interval has elapsed. True,
+the interval is extremely minute; still it is a real interval. News of
+the burn has to be telegraphed from the finger, through the nerves of
+the arm, up to the brain; and it occupies time in transmission, though
+so small a fraction of a second that we can not be conscious of it.
+
+Now, try to imagine a child on earth with an arm long enough to reach
+the sun. His fingers might be scorched by the raging fires there, while
+yet his brain on earth would remain quite unaware of the fact for
+about one hundred and thirty years. All through those years, sensation
+would be darting along the arm exactly as fast as it darts from the
+finger-tips of an ordinary child on earth to that child’s brain.
+
+If the scorching began before he was one year old, he would have become
+a very aged man, one hundred and thirty years old, before he could know
+in his mind what was happening in the region of his hand. Moreover, if,
+on receiving the intimation, he should decide to withdraw his hand from
+that unpleasantly-hot neighborhood, another hundred and thirty years
+would elapse before the fingers could receive and act upon the message,
+telegraphed from the brain, through the nerves of the arm. So much for
+the distance of the sun from our earth!
+
+But the stars! How far off are the stars?
+
+The distance of the moon is a mere nothing. The distances of the
+planets have been found out. The distance of the sun has been measured.
+But the stars--those wondrous points of light, twinkling on, night
+after night, century after century, unchanged in position save by the
+seeming nightly pilgrimage of them all across the sky in company,
+caused only by our earth’s restless, continual whirl,--
+
+What about the distances of the stars? Can we measure their distance
+by means of their parallax? This mode of measurement was tried
+successfully on the moon, on the planets, and on the sun. But when it
+was tried upon the stars, from two stations as far apart as any two
+stations on earth could be, the attempt was a failure. Not a ghost of
+parallax could be detected with any one star. Not the faintest sign
+of displacement was seen in the position of a single star when most
+critically and carefully examined.
+
+Then arose a brilliant thought! What of earth’s yearly journey round
+the sun? If a base-line of 8,000 miles were not enough, compared with
+the great distance of the stars, this at least remained. Our earth at
+midsummer is somewhere about 185,000,000 miles away from where she
+is at midwinter, comparing her position with that of the sun, and
+reckoning him to be at rest.
+
+In reality, the sun is not at rest, but is in ceaseless motion,
+carrying with him, wherever he goes, the whole Solar System with as
+much ease as a train carries its passengers. Those passengers are truly
+in motion, yet, with regard merely to the train, they are at rest. So
+each member of the Solar System--attached to the sun, not by Ptolemaic
+bars, but by the bond of gravity--is borne along by him through space;
+yet, with respect to each member of that system, the central sun is
+always and absolutely at rest.
+
+At one time of the year, our earth is on one side of the sun, over
+92,000,000 miles distant. Six months later, the earth is on the other
+side of the sun, not quite 93,000,000 miles away from him in that
+opposite direction. Twice 93,000,000 comes to 186,000,000. This line,
+therefore--the diameter of the earth’s whole yearly orbit, may be
+roughly stated as about 185,000,000 of miles in length.
+
+Here surely was a base-line fit to give parallax to any star--or,
+rather, to make parallax visible in the case of any star. For it is,
+after all, a question, not of fact, but of visibility; not of whether
+the thing _is_, but of whether we are able to _see_ it.
+
+As the earth journeys on her annual tour round the sun, following a
+slightly elliptic pathway, the diameter of which is about 185,000,000
+miles, each star in the sky must of necessity undergo a change of
+position, however minute, performing a tiny apparent annual journey in
+exact correspondence with the earth’s great annual journey.
+
+The question is not, Does the star do this? but, Can we _see_ the star
+do this? Its apparent change of position may be so infinitesimal,
+through enormous distance, that no telescopes or instruments yet made
+by man can possibly show it to us.
+
+The star-motion of which I am now speaking is purely a seeming
+movement, not real. Be very clear on this point in your mind.
+_Real_ star-movements, though suspected earlier, were not definitely
+surmised--one may even say “discovered”--until the year 1718, by
+Halley. And though Cassini in 1728 referred to this discovery of
+Halley’s, yet very little was heard about the matter until the days of
+Herschel. Only _apparent_ star-motions were generally understood and
+accepted.
+
+The first and simplest of such seeming star-motions is one which we can
+all see--the nightly journey of the whole host of stars, caused by our
+earth’s whirl upon her axis.
+
+The second is also simple, but by no means also easily seen.
+Astronomers reasoned out the logical necessity for such an apparent
+motion long before it could be perceived. As far back as the days of
+Copernicus it was felt that if the Copernican System were true, if the
+earth in very deed traveled round the sun, then the stars ought to
+change their positions in the sky when viewed from different parts of
+earth’s annual journey. Observations were taken, divided by six months
+of time and by one hundred and eighty-five millions of miles of space.
+And the stars stirred not!
+
+Stupendous as was this base-line, it proved insufficient. So much
+_more_ stupendous was the distance of the stars that the base-line sank
+to nothing, and once again parallax could not be detected. Not that the
+seeming change of position in the star did not take place, but that
+human eyes were unable to see it, human instruments were unable to
+register it.
+
+There lies the gist of the matter. If the change of position can be
+observed, well and good! The length of the base-line being known, the
+distance of the star may be mathematically calculated. For the size of
+the tiny apparent path, followed in a year by the star, is and must be
+exactly proportioned to the distance of the star from that base-line.
+If the tiny oval be so much larger, then the star is known to be so
+much nearer. If the tiny oval be so much smaller, then the star is
+known to be so much farther away.
+
+But when not the minutest token could be discovered of a star’s
+position in the sky being in the least degree affected by the earth’s
+great annual change of position, astronomers were at a loss. There was
+absolutely nothing to calculate from. The star was a motionless point
+to earth. The whole yearly orbit of earth was a motionless point to the
+star. One slender beam of light united the two. Reckoners had nothing
+to stand upon.
+
+It is interesting to know that Copernicus had actually, long
+before, suggested this as a possible explanation of the absence of
+star-parallax. He thought that astronomers might fail altogether
+to find it, because the stars might be “at a practically infinite
+distance” from our earth.
+
+
+
+
+CHAPTER XXVII.
+
+MEASUREMENT OF STAR DISTANCES.
+
+
+Until the days of Sir William Herschel, little attention was bestowed
+upon the universe of distant stars. Before his advent the interest
+of astronomers had been mainly centered in the sun and his revolving
+worlds. The “fixed stars” were indeed studied, as such, with a certain
+amount of care, and numberless efforts were made to discover their
+distances from earth; but the thought of a vast Starry System, in which
+our little Solar System should sink to a mere point by comparison with
+its immensity, had not yet dawned.
+
+With larger and yet larger telescopes of his own making, Herschel
+studied the whole Solar System, and especially the nature of sun-spots,
+the rings of Saturn, the various motions of attendant moons, together
+with countless other details. He enlarged the system by the discovery
+of another planet outside Saturn--the planet Uranus, till then unknown.
+
+These were only first steps. The work which he did in respect of the
+Solar System was as nothing compared with the work which he did among
+the stars. His work in our system was supplementary to other men’s
+labors; his work among the stars was the beginning of a new era. Like
+many before him, he, too, sought eagerly to find star-parallax, and he,
+too, failed. Not yet had instruments reached a degree of finish which
+should permit measuring operations of so delicate a nature.
+
+Although he might not detect star-parallax, he sprang a mine upon the
+older notions of star-fixity. He shook to its very foundations the
+sidereal astronomy of the day,--the theory, long held, of a motionless
+universe, motionless stars, and a rotating but otherwise motionless
+sun. He did away with the mental picture, then widely believed in,
+of vast interminable fixity and stillness, extending through space,
+varied only by a few little wandering worlds. As he swept the skies,
+and endeavored to gauge the fathomless depths, and vainly pursued the
+search for the parallax of one star after another, he made a great and
+unlooked-for discovery. This was in connection with double-stars.
+
+Double-stars had long been known, and were generally recognized. But
+whether the doubleness were purely accidental, due merely to the fact
+of two stars happening to lie almost in the same line of sight, as
+viewed from earth, or whether any real connection existed between
+the two, no man living could say. Indeed, so long as all stars were
+regarded as utter fixtures, the question was of no very great interest.
+
+But light dawned as Herschel watched. He found the separate stars in a
+certain pair to be moving. Each from time to time had slightly, very
+slightly, changed its place. Then, at least, if all other stars in
+the universe were fixed, those two were not fixed. He watched on, and
+gradually he made out that their motions were steady, were systematic,
+and were connected the one with the other. That was one of the first
+steps towards breaking down the olden notion, so widely held, of a
+fixed and unchanging universe.
+
+Another double-star, and yet another, responded to Herschel’s intense
+and careful searching. These other couples, too, were revolving, not
+separately, but in company; journeying together round one center; bound
+together apparently by bonds of gravitation, even as our sun and his
+planets are bound together.
+
+Other stars besides binary stars are found to move with a real and
+not merely a seeming movement. Viewed carelessly, the stars do indeed
+appear to remain fixed in changeless groups; fixed even through
+centuries. But, to exceedingly close watching and accurate measurement,
+many among them are distinctly _not_ fixed; many among them can be
+actually seen to move.
+
+Of course the observed motions are very small and slow. One may be
+found to creep over a space as wide as the whole full moon in the
+course of three hundred or four hundred years; and this is rapid
+traveling for a star in earth’s sky! Another will perhaps cross a space
+one-tenth or one-twentieth or one-fiftieth of the moon’s width in one
+hundred years.
+
+Such motions had never been carefully noted or examined, until Herschel
+came to do away with the old received notions of star-fixity. Happily,
+Herschel was no slave to “received ideas.” Like Galileo in earlier
+times, he wished to “prove all things” personally, anxious only to find
+out what was the truth. And he found that the stars were _not_ fixed!
+He found that numbers of them were moving. He conjectured that probably
+all the rest were moving also; that in place of a fixed universe of
+changeless stars we have a whirling universe of rushing suns.
+
+Herschel could not, of course, watch any one star for a hundred years,
+much less for several centuries. But in a very few years he could, by
+exceedingly close measurement, detect sufficient motion to be able to
+calculate how long it would take a certain star to creep across a space
+as wide as the full moon.
+
+From step to step he passed on, never weary of his toil. He sought to
+gauge the Milky Way, and to form some notion of its shape. He noted
+a general drift of stars to right and to left, which seemed to speak
+of a possible journey of our sun through space, with all the planets
+of the Solar System. He flung himself with ardor into the study of
+star-clusters and of nebulæ. He saw, with an almost prophetic eye, the
+wondrous picture of a developing universe--of nebulæ growing slowly
+into suns, and of suns cooling gradually into worlds--so far as to
+liken the heavens to a piece of ground, containing trees and plants in
+every separate stage of growth.
+
+And still the search for star parallax went on, so long pursued in
+vain. No longer base-line than that of the diameter of earth’s yearly
+orbit lay within man’s reach. But again and yet again the attempt was
+made. Instruments were improved, and measurements became ever more
+delicate; and at length some small success crowned these persistent
+endeavors. The tiny sounding-line of earth, lowered so often into the
+mysterious depths of space, did at last “touch bottom.”
+
+Herschel died, full of years and honors, in 1822; and some ten years
+later three different attempts proved, all to some extent, and almost
+at the same date, successful. Bessel, however, was actually the first
+in point of time; and his attempt was upon the double-star, 61 Cygni;
+not at all a bright star, but only just visible to the naked eye.
+
+There are stars and stars, enough to choose from. The difficulty
+always was, which to select as a subject for trial with any reasonable
+prospect of a good result. Some astronomers held that the brightest
+stars were the most hopeful, since they were probably the nearest; and
+of course the nearer stars would show parallax more readily, because
+their parallax would be the greater. But certain very bright stars
+indeed are now known to be far more distant than certain very dim stars.
+
+Again, some astronomers thought that such stars as could be perceived
+to move most rapidly in the course of years would be the most hopeful
+objects to attack, since the more rapid movement might be supposed to
+mean greater nearness, and so greater ease of measurement. But some
+stars, seen to move rapidly, are now known to be more distant than
+others which are seen to move more sluggishly. So neither of these two
+rules could altogether be depended on; yet both were, on the whole, the
+best that could be followed, either separately or together.
+
+The star 61 Cygni is not one of the brighter stars, but it is one of
+those stars which can be seen to travel most quickly across the sky in
+the course of a century. Therefore it was selected for a trial; and
+that trial was the first to meet with success.
+
+For 61 Cygni was found to have an apparent parallax; in other words,
+its tiny seeming journey through the year, caused by our earth’s great
+journey round the sun, could be detected. Small as the star-motion
+was, it might, through careful measurement, be perceived. And, in
+consequence, the distance of the star from earth could be measured.
+Not measured with anything like such exactitude as the measurements
+of sun-distance, but with enough to give a fair general notion of
+star-distance.
+
+One success was speedily followed by others. By a few others,--not by
+many. Among the thousands of stars which can be seen by the naked eye,
+one here and one there responded faintly to the efforts made. One here
+and one there was found to stir slightly in the sky, when viewed from
+earth’s summer and winter positions, or from her spring and autumn
+positions, in her yearly pathway round the sun.
+
+It was a very, very delicate stir on the part of the star. Somewhat
+like the difference in position which you might see in a penny a
+few miles off, if you looked at it first out of one window and then
+out of another window in the same house. You may picture the penny
+as radiantly bright, shining through pitch darkness; and you may
+picture yourself as looking at it through a telescope. But even so,
+the apparent change of position in the penny, viewed thus, would be
+exceedingly minute, and exceedingly difficult to see.
+
+There are two ways of noting this little seeming movement on the part
+of a star in the sky.
+
+Either its precise place in the sky may be observed--its exact
+position, as in a map of the heavens--or else its place may be noted
+as compared with another more distant star, near to it in the sky,
+though really far beyond. Parallax, if visible, would make it alter its
+precise place in the sky. Parallax, if visible, would bring it nearer
+to or farther from any other star more distant than itself from earth.
+The more distant star would have a much smaller parallax--probably
+so small as to be invisible to us--and so it would do nicely for a
+“comparison star.”
+
+The first of these methods was the first tried; and the second was the
+first successful.
+
+To find star-distance through star-parallax sounds quite simple,
+when one thinks of the general principle of it. Just merely the
+question of a base-line, accurately measured; and of two angles,
+accurately observed; and of another angle, a good way off, accurately
+calculated,--all resting on the slight seeming change of position in
+a certain distant object, watched from two different positions, about
+185,000,000 miles apart.
+
+Quite simple, is it not? Only, when one comes to realize that the
+“change of position” is about equal to the change of position in a
+penny piece, miles away, looked at from two windows in one house,--then
+the difficulty grows.
+
+Besides this, one has to remember all the “corrections” necessary,
+before any true result can be reached.
+
+A penny piece, miles away, seen from two windows, would be difficult
+enough as a subject for measurement. But, at least, the penny would
+be at rest; and you yourself would be at rest; and light would pass
+instantaneously from it to you; and there would be no wobbling and
+nodding motions of everything around to add to your perplexities.
+
+In the measurement of star-parallax, all these things have to be
+considered and allowed for; all have to be put out of the question, as
+it were, before any correct answer is obtained.
+
+The refraction of light must be considered; because that displaces the
+star, and makes it seem to us to be where it is not. And the aberration
+of light must be considered; because, in a different way, that does the
+same thing, making the star seem to take a little journey in the course
+of the year. And the precession, or forward motion, of the equinoxes,
+and nutation, or vibratory motion, have both to be separately
+considered; because they, too, affect the apparent position of every
+star in the sky.
+
+To watch the star in comparison with another star is easier than
+merely to note its exact position in the sky; for the other star--the
+“companion-star”--is equally with itself affected by refraction of
+light and by aberration of light. But, then, another question comes in
+seriously: whether or no the companion-star shows any parallax also;
+since, if it does, that parallax must be carefully calculated and
+allowed for.
+
+So the measurement of star-distance, even when parallax can be
+detected, is by no means a light or easy matter. On the contrary, it
+bristles with difficulties. It is a most complicated operation, needing
+profound knowledge, accurate observation, trained powers of reasoning
+and calculation.
+
+Nothing short of what has been termed “the terrific accuracy” of the
+present day could grapple with the truly tremendous difficulties of
+this problem of star-distance. It has, however, been grappled with,
+and grappled with successfully. We now know, not indeed with anything
+like exactitude, yet with reasonable certainty, the distances of a good
+many stars, as expressed roughly in round number of “about” so many
+trillions of miles.[3] We have at least learned enough to gain some
+notion of the immeasurable distances of countless other stars, lying
+far beyond reach of earth’s longest measuring-line.
+
+[3] The diameter of the moon as seen from the earth is equal to
+one thousand eight hundred and sixty eight seconds of space. When
+the parallax of a star is ascertained, it is a simple matter to
+calculate the distance of the star by the use of the following table.
+If the star shows a displacement of one second in space, or one
+eighteen-hundred-and-sixty-eighth part of the width of the moon, that
+star is distant two hundred and six thousand two hundred and sixty-five
+times the distance of the earth from the sun.
+
+  An angle of 1″   is equivalent to   206,265 times 93,000,000 of miles.
+  “    “   “  0″.9 “      “      “    229,183   “       “      “    “
+  “    “   “  0″.8 “      “      “    257,830   “       “      “    “
+  “    “   “  0″.7 “      “      “    294,664   “       “      “    “
+  “    “   “  0″.6 “      “      “    343,750   “       “      “    “
+  “    “   “  0″.5 “      “      “    412,530   “       “      “    “
+  “    “   “  0″.4 “      “      “    515,660   “       “      “    “
+  “    “   “  0″.3 “      “      “    687,500   “       “      “    “
+  “    “   “  0″.2 “      “      “  1,031,320   “       “      “    “
+  “    “   “  0″.1 “      “      “  2,062,650   “       “      “    “
+  “    “   “  0″.0 “      “      “  Immeasurable.
+
+The nearest star, Alpha Centauri, shows a parallax of less than one
+second (0″.75). The farthest star, the distance of which has been
+ascertained, is 1830 Groombridge, which shows a parallax of only
+0″.045, and is distant 4,583,000 times earth’s distance from the sun,
+or 426 trillions of miles.
+
+The very thought of such unimaginable depths of space, of suns beyond
+suns “in endless range,” toned down by simple distance to mere
+quivering specks of light, is well-nigh overwhelming.
+
+
+
+
+CHAPTER XXVIII.
+
+THE MILKY WAY.
+
+
+The Milky Way forms a soft band of light round the whole heavens. In
+the Southern Hemisphere, as in the Northern Hemisphere, it is to be
+seen. In some parts the band narrows; in some parts it widens. Here
+it divides into two branches; there we find dark spaces in its midst.
+One such space in the south is so black and almost starless as to have
+been named the Coal-sack. All along, over the background of soft, dim
+light, lies a scattering of brighter stars shining on its surface.
+Much interest and curiosity have long been felt about this mysterious
+Milky Way. That it consists of innumerable suns, and that our sun is
+one among them, has been believed for a considerable time. But other
+questions arise. How many stars does the Milky Way contain? What is its
+shape? How far does it reach?
+
+No harm in asking the questions, only we have to be satisfied in
+astronomy to ask many questions which can not yet receive answers. No
+harm for man to learn that the utmost reach of his intellect must fall
+short in any attempt to sound the depths of God’s universe, even as the
+arm of a child would fall short in seeking to sound the depths of the
+ocean over the side of a little boat. For the attempt has been made to
+sound the depths of our star-galaxy out of this little earth-boat.
+
+The idea first occurred to the great Herschel, as we have already
+mentioned, and a grand idea it was--only a hopeless one. He turned
+his powerful telescope north, south, east, west. He counted the stars
+visible at one time in this, in that, in the other directions. He found
+a marked difference in the numbers. The portion of sky seen through
+his telescope was about one quarter the size of that covered by the
+moon. Sometimes he could merely perceive two or three bright points
+on a black background. At other times the field of his telescope was
+crowded. In the fuller portions of the Milky Way, he had four or five
+hundred stars under view at once. In one place he saw about one hundred
+and sixteen thousand stars pass before him in a single quarter of an
+hour.
+
+Herschel took it for granted that the stars of the Milky Way,
+uncountable in numbers, are, as a rule, much the same in size--so that
+brightest stars would, as a rule, be nearest, and dimmest stars would,
+as a rule, be farthest off. Where he found stars clustering thickly,
+beyond his power to penetrate, he believed that the Milky Way reached
+very far in that direction. Where he found black space, unlighted by
+stars or lighted by few stars, he decided that he had found the borders
+of our galaxy in that direction.
+
+Following these rules which he had laid down, he made a sort of rough
+sketch of what he supposed might be the shape of the Milky Way. He
+thought it was somewhat flat, extending to a good distance breadthways
+and a much greater distance lengthways, and he placed our sun not far
+from the middle. This imagined shape of the Milky Way is called “The
+Cloven-disk Theory.” To explain the appearance of the Milky Way in the
+sky, Herschel supposed it to be cloven or split through half of its
+length, with a black space between the two split parts.
+
+It seems that Herschel did not hold strongly to this idea in later
+years, and doubts are now felt whether the rules on which he formed it
+have sufficient foundation.
+
+For how do we know that the stars of the Milky Way are, as a rule,
+much the same in size? Certainly the planets of the Solar System are
+very far from being uniform, and the few stars whose weight can with
+any certainty be measured, seem to vary considerably. There is a
+great difference also between the large and small suns in many of the
+double-stars!
+
+Again, how do we know that the bright stars are, as a rule, the
+nearest, and the dim stars the farthest off? Here, also, late
+discoveries make us doubtful. Look at Sirius and 61 Cygni--Sirius the
+most radiant star in the heavens, and 61 Cygni almost invisible to the
+naked eye. According to this rule, 61 Cygni ought to lie at an enormous
+distance beyond Sirius. Yet in actual fact, Sirius is the farthest away
+of the two.
+
+The illustrious Herschel believed that he had penetrated, on one
+occasion, into the star-cluster on the sword-hand in the constellation
+of Perseus until he found himself among sidereal depths, from which the
+light could not have reached him in less than four thousand years.
+
+The distance of those stars had not, and has not, been mathematically
+measured. Herschel judged of it by their dimness, by the strong power
+needed to make them visible, and by the rules which he had adopted as
+most likely true.
+
+Again, when Herschel found black spaces in the heavens almost void of
+stars, and believed that he had reached the outside borders of the
+Milky Way, he may have been in the right, or he may have been mistaken.
+The limit might lie there, or thousands more of small stars might
+extend in that very direction, too far off for their little glimmer to
+be seen through the most powerful telescope.
+
+[Illustration: A CLUSTER OF STARS IN PERSEUS.]
+
+If this latter idea about the Milky Way being formed of a great many
+brilliant suns, and of vast numbers of lesser suns also, be true,
+astronomers will, in time, be able to prove its truth. For in that
+case, many faint telescopic stars being much nearer to us than bright
+stars of the greater magnitudes, it will be found possible to measure
+their distance. The journey of our earth round the sun must cause a
+seeming change in their position between summer and winter.
+
+The theory also that some of the nebulæ are other outlying Milky Ways,
+or galaxies of stars, separated by tremendous distances from our own,
+is interesting, and was long held as almost certain, yet we have no
+distinct proof either one way or the other. Many of the nebulæ may be
+such gatherings of countless stars outside our own, or every nebula
+visible may be actually part and parcel of our galaxy.
+
+Much attention has of late been paid to the arrangement of stars in the
+sky. The more the matter is looked into, the more plainly it is seen
+that stars are neither regular in size nor regular in distribution.
+They are not merely scattered carelessly, as it were, here, there, and
+anywhere, but certain laws and plans of arrangement seem to have been
+followed which astronomers are only now beginning dimly to perceive.
+
+Stars are not flung broadcast through the heavens, each one alone and
+independent of the rest. They are placed often, as we have already
+seen, in pairs, in triplets, in quartets, in clusters. Also, the great
+masses of them in the heavens seem to be more or less arranged in
+streams, and sprays, and spirals. So remarkable are the numbers and
+forms of many of these streams that the idea has been suggested, with
+regard to the Milky Way, whether it also may not be a vast stream of
+stars, like a mighty river, collecting into itself hundreds of lesser
+streams.
+
+The contemplation of the heavens affords no spectacle so grand and so
+eloquent as that of a cluster of stars. Most of them lie at such a
+distance that the most powerful telescopes still show them to us like
+star-dust. “Their distance from us is such that they are beyond, not
+only all our means of measurement,” says Newcomb, “but beyond all our
+powers of estimation. Minute as they appear, there is nothing that
+we know of to prevent our supposing each of them to be the center of
+a group of planets as extensive as our own, and each planet to be as
+full of inhabitants as this one. We may thus think of them as little
+colonies on the outskirts of creation itself, and as we see all the
+suns which give them light condensed into one little speck, we might
+be led to think of the inhabitants of the various systems as holding
+intercourse with each other. Yet, were we transported to one of these
+distant clusters, and stationed on a planet circling one of the suns
+which compose it, instead of finding the neighboring suns in close
+proximity, we should see a firmament of stars around us, such as we see
+from the earth. Probably it would be a brighter firmament, in which
+so many stars would glow, with more than the splendor of Sirius, as
+to make the night far brighter than ours; but the inhabitants of the
+neighboring worlds would as completely elude telescopic vision as the
+inhabitants of Mars do here. Consequently, to the inhabitants of every
+planet in the cluster, the question of the plurality of worlds might be
+as insolvable as it is to us.”
+
+These are clusters of stars of regular form in which attraction appears
+to mark its secular stamp. Our mind, accustomed to order in the cosmos,
+anxious for harmony in the organization of things, is satisfied with
+these agglomerations of suns, with these distant universes, which
+realize in their entirety an aspect approaching the spherical form.
+More extraordinary, more marvelous still, are the clusters of stars
+which appear organized in spirals.
+
+In considering stars of the first six magnitudes only--stars visible
+to the naked eye--a somewhat larger number is found in the Southern
+Hemisphere than in the Northern Hemisphere. In both hemispheres there
+are regions densely crowded with stars, and regions by comparison
+almost empty.
+
+It has been long questioned whether the number of bright stars is or is
+not greater in the Milky Way than in other parts of the sky. Careful
+calculations have at length been made. It appears that the whole of the
+Milky Way--that zone of soft light passing round the earth--covers, if
+we leave out the Coal-sack and other such gaps, between one-tenth and
+one-eleventh of the whole heavens.
+
+The entire number of naked-eye stars, or stars of the first six
+magnitudes, does not exceed six thousand; and of these, eleven hundred
+and fifteen lie scattered along the bed of the Milky Way stream. If the
+brighter stars were scattered over all the sky as thickly as throughout
+the Milky Way, their number would amount to twelve thousand instead of
+only six thousand. This shows us that the higher-magnitude stars really
+are collected along the Milky Way in greater numbers than elsewhere,
+and is an argument used by those who believe the Milky Way to be a
+mighty stream of streams of stars.
+
+In the dark spaces of the Milky Way, on the contrary, bright stars are
+so few that if they were scattered in the same manner over all the sky,
+their present number of six thousand would come down to twelve hundred
+and forty. This would be a serious loss.
+
+We know in the sky 1,034 clusters of stars and more than 11,000
+nebulæ. The former are composed of associated stars; the latter may
+be divided into two classes: First, nebulæ which the ever-increasing
+progress of optics will one day resolve into stars, or which in any
+case are composed of stars, although their distances may be too great
+to enable us to prove it; second, nebulæ properly so called, of which
+spectrum analysis demonstrates their gaseous constitution. Here is
+an instructive fact. The clusters of stars present the same general
+distribution as the telescopic stars--they are more numerous in the
+plane of the Milky Way, while it is the contrary which is presented
+by the nebulæ properly so called; they are rare, thinly spread in the
+Milky Way, and thickly scattered to the north as well as to the south
+of this zone up to its poles. The constitution of the Milky Way--not
+nebulous, but stellar--is a very significant fact. The nebulæ properly
+so called are distributed, in a sense, contrary to the stars, being
+more numerous towards the poles of the Milky Way and in regions poor
+in stars, as if they had absorbed the matter of which the stars are
+formed.
+
+
+
+
+CHAPTER XXIX.
+
+A WHIRLING UNIVERSE.
+
+
+No rest, no quiet, no repose, in that great universe, which to our dim
+eyesight looks so fixed and still, but one perpetual rush of moving
+suns and worlds. For every star has its own particular motion, every
+sun is pressing forward in its own appointed path. And among the
+myriads of stars--bright, blazing furnaces of white or golden, red,
+blue, or green flame--sweeping with steady rush through space, our sun
+also hastens onwards.
+
+The rate of his speed is not very certain, but it is generally believed
+to be about one hundred and fifty million miles each year. Possibly he
+moves in reality much faster.
+
+When I speak of the sun’s movement, it must of course be understood
+that the earth and planets all travel with him, much as a great steamer
+on the sea might drag in his wake a number of little boats. From one
+of the little boats you could judge of the steamer’s motion quite as
+well as if you were on the steamer itself. Astronomers can only judge
+of the sun’s motion by watching the seeming backward drift of stars to
+the right and left of him; and the watching can be as well accomplished
+from earth as from the sun himself.
+
+After all, this mode of judging is, and must be, very uncertain. Among
+the millions of stars visible, we only know the real distances of
+about twenty-five; and every star has its own real motion, which has to
+be separated from the apparent change of position caused by the sun’s
+advance.
+
+It seems now pretty clear that the sun’s course is directed towards a
+certain point in the constellation Hercules. If the sun’s path were
+straight, he might be expected by and by, after long ages, to enter
+that constellation. But if orbits of suns, like orbits of planets, are
+ellipses, he will curve away sideways long before he reaches Hercules.
+
+[Illustration: HERCULES]
+
+One German astronomer thought he had found the center of the sun’s
+orbit. He believed the sun and the stars of the Milky Way to be
+traveling round the chief star in the Pleiades, Alcyone. This is
+not impossible; but it is now felt that much stronger proof will be
+required before the idea can be accepted.
+
+In the last chapter mention was made of star-streams as a late
+discovery. Though a discovery still in its infancy, it is one of no
+small importance. Briefly stated, the old theory as to the plan of
+the Milky Way was as follows: Our sun was a single star among millions
+of stars forming the galaxy, some comparatively near, some lying at
+distances past human powers of calculation, and all formed upon much
+the same model as to size and brightness. Where the band of milky
+light showed, stars were believed to extend in countless thousands to
+measureless distances. Where dark spaces showed, it was believed that
+we looked beyond the limits of our universe into black space. Stars
+scattered in other parts of the sky were supposed generally to be
+outlying members of the same great Milky Way. Many of the nebulæ and
+star-clusters were believed to be vast and distant gatherings of stars,
+like the Milky Way itself, but separated by unutterably wide reaches of
+space. Some of these views may yet be found to contain truth, though at
+the present moment a different theory is afloat.
+
+It is still thought probable that our sun is one among many millions
+of suns, forming a vast system or collection of stars, called by
+some a universe. It is also thought possible that other such mighty
+collections of stars may exist outside and separate from our own at
+immense distances. It is thought not impossible or improbable that some
+among the nebulæ may be such far-off galaxies of stars; though, on the
+other hand, it is felt that every star-cluster and nebula within reach
+of man’s sight may form a part of our own “universe.”
+
+According to this view of the question, the Milky Way, instead of
+being an enormous universe of countless suns reaching to incalculable
+distances, may rather be a vast and mighty star-stream, consisting
+of hundreds of brilliant leading suns, intermixed with thousands or
+even millions of lesser shining orbs. If this be the true view, the
+lesser suns would often be nearer than the greater suns, although more
+dim; and the Milky Way would not be itself a universe, though a very
+wonderful and beautiful portion of our universe.
+
+Which of these two different theories or opinions contains the most
+truth remains to be found out. But respecting the arrangement of
+stars into streams, interesting facts have lately been discovered. We
+certainly see in the Solar System a tendency of heavenly bodies to
+travel in the same lines and in companies. Not to speak of Jupiter and
+his moons, or Saturn and his moons, we see it more remarkably in the
+hundreds of asteroids pursuing one path, the millions of meteorites
+whirling in herds. Would there be anything startling in the same
+tendency appearing on a mightier scale? Should we be greatly astonished
+to find streams of stars, as well as streams of planets?
+
+For such, indeed, appears to be the case. Separated by abysses of
+space, brother suns are plainly to be seen journeying side by side
+through the heavens, towards the same goal.
+
+The question of star-drift is too complex and difficult to be gone
+into closely in a book of this kind. One example, however, may be
+given. Almost everybody knows by sight the constellation of the Great
+Bear--the seven principal stars of which are called also Charles’s
+Wain, a corruption of the old Gothic _Karl Wagen_, the churl’s or
+peasant’s wagon. It is also called the Great Dipper. Four bright stars
+form a rough sort of oblong, and from one of the corners three more
+bright stars stretch away in a curve, representing the Bear’s tail.
+Many smaller stars are intermixed.
+
+[Illustration: THE GREAT BEAR.]
+
+These seven bright stars have always been bound together in men’s
+minds, as if they belonged to one another. But who, through the
+centuries past, since aught was known of the real distances of the
+stars from ourselves and from one another, ever supposed that any among
+the seven were _really_ connected together?
+
+One of these seven stars, the middle one in the tail, has a tiny
+companion-star, close to it, visible to the naked eye. For a good
+while it was uncertain whether the two were a “real double,” or only
+a seeming double. In time it became clear that the two did actually
+belong to one another.
+
+Mizar is the name of the chief star, and Alcor of the companion. Alcor
+is believed to be about three thousand times as far away from Mizar,
+as our earth from the sun. Now, if this be the width of space between
+those two bright points, lying seemingly so close together as almost to
+look to the naked eye like one, what must be the distance between the
+seven leading stars of the Great Bear, separated by broad sky-spaces?
+Who could imagine that one of these suns had aught to do with the rest?
+
+Yet among other amazing discoveries of late years it has been found by
+means of the new instrument, the spectroscope, that _five_ out of these
+seven suns are traveling the same journey, with the same speed. Two of
+the seven appear to be moving in another direction, but three of the
+body-stars and two of the tail-stars are hastening in the direction
+away from us, all in the same line of march, all rushing through space
+at the rate of twenty miles each second. Some smaller stars close to
+them are also moving in the same path. Is not this wonderful? We see
+here a vast system of suns, all moving towards one goal, and each
+probably bearing with him his own family of worlds.
+
+Many such streams have been noticed, and many more will doubtless be
+found. For aught we know, our own sun may be one among such a company
+of brother-suns, traveling in company.
+
+It is difficult to give any clear idea of the immensity of the
+universe--even of that portion of the universe which lies within reach
+of our most powerful telescopes. How far beyond such limits it may
+reach, we lose ourselves in imagining.
+
+Earlier in the book we have supposed possible models of the Solar
+System, bringing down the sun and worlds to a small size, yet keeping
+due proportions. What if we were to attempt to make a reduced model of
+the universe; that is of just so much of it as comes within our ken?
+
+Suppose a man were to set himself to form such a model, including
+every star which has ever been seen. Let him have one tiny ball for
+the sun, and another tiny ball for Alpha Centauri; and let him, as a
+beginning, set the two _one yard apart_. That single yard represents
+ninety-three millions of miles, two hundred and seventy-five thousand
+times repeated. Then let him arrange countless multitudes of other tiny
+balls, at due distances--some five times, ten times, twenty times,
+fifty times, as far away from the sun as Alpha Centauri.
+
+It is said that the known universe, made upon a model of these
+proportions, would be many miles in length and breadth. But the model
+would appear fixed as marble. The sizes and distances of the stars
+being so enormously reduced, their rates of motion would be lessened
+in proportion. Long intervals of time would need to pass before the
+faintest motion in one of the millions of tiny balls could become
+visible to a human eye.
+
+
+
+
+CHAPTER XXX.
+
+READING THE LIGHT.
+
+
+[Illustration: THE PRISM AND SPECTRUM.]
+
+Several times, in the course of this book, mention has been made of a
+wonderful new instrument called the spectroscope. We now proceed to
+give a brief account of the origin and achievements of this newest of
+scientific appliances. The first step towards its formation was made
+by Sir Isaac Newton, when he discovered the power of the prism to
+decompose light. This consists in the fact that a ray of light, after
+passing through a transparent prism, becomes expanded into an elongated
+spectrum, no longer white, but presenting an invariable succession of
+colors from red to violet. These are called the seven primary colors;
+namely, red, orange, yellow, green, blue, indigo, and violet. The
+rainbow is a familiar illustration of this spectrum with its various
+colors; and the raindrops are the prisms which reflect and decompose
+the light.
+
+[Illustration: THE SPECTROSCOPE.]
+
+Optical science was long satisfied with this glance into the interior
+constitution of light, occupying itself with the phenomena of the
+prismatic colors, and theorizing on the nature of white light. In
+1802, Dr. W. H. Wollaston, in closely examining a spectrum, found it
+to be crossed by at least four fine dark lines. It is only when an
+extremely narrow slit is employed in admitting the sunlight that they
+become visible. Dr. Wollaston, supposing them to be merely “natural
+boundaries” of the different color-bands, inquired no further; and
+there for a while the matter rested. Not many years later, in 1815,
+the matter was taken up by a German optician and scientist of Munich,
+Joseph von Fraunhofer. Applying more delicate means of observation, he
+was surprised to find very numerous dark lines crossing the spectrum.
+
+With patience he went into the question, using the telescope as well
+as a very narrow slit, and soon he discovered that the dark lines were
+to be numbered, not by units or by tens, but by hundreds--or, as we
+now know, by thousands. Some were in the red, some were in the violet,
+some were in the intermediate bands; but each one had, and has, its own
+invariable position on the solar spectrum. For, be it understood, these
+dark lines are constant, not variable. Where a line is seen, there it
+remains. Whenever a ray of sunlight is properly examined, with slit and
+with prism, that line will be found always occupying precisely the same
+spot in the spectrum.
+
+Some of the chief and more distinct lines were named by Fraunhofer
+after certain letters of the alphabet, and by those letter-names they
+are still known. He began with A in the red and went on to H in the
+violet. Fraunhofer made a great many experiments connected with these
+mysterious lines, anxious to discover, if possible, their meaning. For
+although he now saw the lines, which had scarcely so much as been seen
+before, he could not understand them--he could not read what they said.
+They spoke to him, indeed, about the sun; but they spoke in a foreign
+language, the key to which he did not possess. He tried making use of
+prisms of different materials, thinking that perhaps the lines might be
+due to something in the nature of the prism employed. But let the prism
+be what it might, he found the lines still there. Then he examined
+the light which shines from bright clouds, instead of capturing a ray
+direct from the sun. And he found the lines still there. For cloudlight
+is merely reflected sunlight.
+
+Then he examined the light of the moon, to see if perchance the
+spectrum might be clear of breaks. And he found the lines still
+there. For moonlight is only reflected sunlight. Next he set himself
+to examine the light which travels to us from some of the planets,
+imagining that a different result might follow. And he found the lines
+still there. For planet-light again is no more than reflected sunlight.
+
+[Illustration: SPECTRA, SHOWING THE DARK LINES.]
+
+Lastly, he turned his attention to some of the brighter stars,
+examining, one by one, the ray which came from each. And, behold! he
+found the lines _not_ there. For starlight is not reflected sunlight.
+That is to say, the identical lines which distinguish sunlight were
+not there. Each star had a spectrum as the sun has a spectrum, and
+each star-spectrum was crossed by faint dark lines, more or less in
+number. But the spectra of the stars differed from the spectrum of the
+sun. Each particular star had its own particular spectrum of light,
+different from that of the sun, and different from that of every other
+star. For now, Fraunhofer was examining, not sunlight, but starlight;
+not the light of our sun, either direct from himself or reflected from
+some other body, such as planet or moon or cloud, but the light of
+other suns very far distant, each one varying to some extent from the
+rest in its make. The fact of the stars showing numerous sets of black
+lines, all unlike those of our sun, showed conclusively that those
+lines could not possibly be due to anything in our earthly atmosphere.
+Sunlight and starlight travel equally through the air, and are equally
+affected by it. If our atmosphere were the cause of the black lines in
+sunlight, it would cause the _same_ lines in starlight. But the sun and
+each individual star has its own individual lines, quite irrespective
+of changeful states of the air.
+
+So, also, the light from any metal sufficiently heated will give
+a spectrum, just as sunlight gives a spectrum, under the needful
+conditions. That is to say, there must be slit and prism, or slit and
+diffraction-grating, for the light to pass through. But the kind of
+spectrum is by no means always the same.
+
+Putting aside for a few minutes the thought of sunlight and starlight,
+let us look at the kind of rays or beams which are given forth by
+heated earthly substances. Any very much heated substance sends forth
+its light in rays or beams, and any such rays or beams may be passed
+through a prism, and broken up or “analyzed,” just as easily as
+sunlight may be “analyzed.”
+
+Suppose that we have a solid substance first--a piece of iron or of
+steel wire. If it is heated so far as to give out, not only heat,
+but also light, and if that light is made to travel through the slit
+and prism of a spectroscope, the ray will then be broken up into its
+sub-rays. They, like the sub-rays of a sunbeam, will form a continuous
+row of soft color-bands, one melting into another. This is the
+characteristic spectrum of the light which is given forth by a burning
+or glowing _solid_.
+
+Next, suppose we take a liquid--some molten iron or some molten glass,
+for instance. If you have ever been to a great plate-glass manufactory,
+like that at St. Helens, not far from Manchester, you will have seen
+streams of liquid glass pouring about, carried to and fro in huge
+caldrons, bright with a living light of fire from its intensity of
+heat. If a ray of _that_ light had been passed through slit and prism,
+what do you think would have been the result? A continuous spectrum
+once more, the same as with the glowing iron or steel. The light-ray
+from a heated and radiant _liquid_, when broken up by a prism, lies in
+soft bands of color, side by side.
+
+Both of them a good deal like the solar spectrum, you will say. Only
+here are no mysterious dark lines crossing the bright bands of color.
+But how about gases? Suppose we have a substance in the state of gas
+or vapor, as almost every known substance might be under the requisite
+conditions, and suppose that substance to be heated to a glowing
+brilliance. Then let its light be passed through the slit and prism of
+a spectroscope. What result shall we find this time? Entirely different
+from anything seen before. Instead of soft, continuous bands of color,
+there are _bright lines_, well separated and sharply defined.
+
+How many bright lines? Ah, that depends upon which particular gas
+is having its ray analyzed. Try sodium first--one of the commonest
+of earthly substances. Enormous quantities of it are distributed
+broadcast in earth and air and water. More than two-thirds of the
+surface of our globe lies under an enfolding vesture of water saturated
+with salt, which is a compound of sodium. That is to say, sodium enters
+largely into the make of salt. Every breeze which sweeps over the ocean
+carries salt inland, to float through the atmosphere. Sir H. E. Roscoe
+writes: “There is not a speck of dust, or a mote seen dancing in the
+sunbeam, which does not contain chloride of sodium”--otherwise salt.
+The very air which surrounds us is full of compounds of sodium, and
+we can not breathe without taking some of it into our bodies. Sodium
+is an “elementary substance.” By which I mean that it is one of a
+number of substances called by us “simple,” because chemists have never
+yet succeeded in breaking up those substances, by any means at their
+command, into other and different materials.
+
+Iron is, so far as we know, a simple substance. It is found as iron
+in the earth. No chemist has ever been able to make iron by combining
+other materials together. No chemist has ever managed to separate iron
+into other materials unlike itself. Iron it is, and iron it remains,
+whether as a solid, as a liquid, or as a gas. Gold is another simple
+substance, and so is silver. Sodium is another. All these we know best
+in the solid form. Mercury, another simple substance, we know best as a
+liquid.
+
+Water is not a simple substance; for it can be separated into
+two different gases. Glass is not a simple substance; for it is
+manufactured out of other substances combined together.
+
+We can speak quite positively as to such substances as are not simple;
+but with regard to so-called “elements,” we may only venture to assert
+that, thus far, nobody has succeeded in breaking them up. Therefore, at
+least for the present, they are to us “elementary.”
+
+All the simple substances, and very many of the combinations of them,
+though often known to us only in the solid form, may, under particular
+conditions, be rendered liquid, and even gaseous. Every metal may be
+either in the solid form, or the liquid form, or the vapor form. Iron,
+as we commonly see it, is solid--in other words, it is frozen, like
+ice. Just as increase of warmth will turn ice into water, so a certain
+amount of heat will make solid iron become liquid iron. And just as yet
+greater warmth will turn water into steam, so a very much increased
+amount of heat will turn liquid iron into vapor of iron. A little heat
+will do for ice what very great heat will do for iron.
+
+Whether iron and other metals exist in the sun, as on earth, in a
+hard and solid form, it is impossible to say. It is only in the form
+of gas that man can become aware of their presence at that distance.
+The intense, glowing, furnace-heat of the sun causes many metals to
+be present in large quantities in the sun’s atmosphere in the form of
+vapor.
+
+Not only have we learned about some of the metals in the sun, but
+this strange spectrum analysis has taught us about some of the metals
+and gases in the stars as well. It is found that in Sirius, sodium
+and magnesium, iron and hydrogen, exist. In Vega and Pollux there are
+sodium, magnesium, and iron. In Aldebaran, these substances and many
+others, including mercury, seem to abound. These are merely a few
+examples among many stars, each being in some degree different from the
+rest.
+
+But how can we know all this? How could the wildest guessing reveal to
+us the fact of iron in the sun, not to speak of the stars? We know it
+by means of the spectrum analysis--or, as we may say, by means of the
+spectroscope. This instrument may be looked upon as the twin-sister to
+the telescope. The telescope gathers together the scattered rays of
+light into a small spot or focus. The spectroscope tears up these rays
+of light into ribbons, sorts them, sifts them, and enables us to read
+in them hidden meanings.
+
+When a ray of light reaches us from the sun, that ray is _white_; but
+in the white ray there are bright colors concealed. Newton was the
+first to discover that a ray of white light is really a bundle of
+colored rays, so mixed up together as to appear white. If a ray of
+sunlight is allowed to pass through a small round hole in a wall, it
+will fall upon the opposite wall in a small round patch of white light.
+But if a _prism_--a piece of glass cut in a particular shape--is put in
+the path of the ray, it has power to do two curious things. First, it
+bends the ray out of a straight course, causing the light to fall upon
+a different part of the wall. Secondly, it breaks up or divides the
+ray of white light into the several rays of colored light of which the
+white ray is really composed. This breaking up, or dividing, is called
+“analyzing.”
+
+If in place of a round hole the ray of light is made to pass through
+a very narrow slit, it is proved that the bright bands of color do not
+overlap. Instead of this, dark lines, or gaps, show here and there.
+Now, these lines or gaps are always to be seen in the spectrum or image
+of bright colors formed by a broken-up ray of _sunlight_. There is
+always a certain number of dark lines in each colored band--some near
+together, some far apart; here one or two, there a great many. Where a
+simple ray of sunlight is concerned, the exact arrangement of the lines
+never changes.
+
+When the stars were examined--when the rays of light coming from
+various stars were split up and analyzed--it was found that they too,
+like the sun, gave a spectrum of bright colors with dark lines. But
+the lines were different in number and different in arrangement from
+the sun’s lines. Each star has his own particular number and his own
+particular arrangement, and that arrangement and number do not change.
+
+If a white-hot metal is burnt, and the light of it as it burns is
+allowed to pass through a prism, a row of bright colors appears as in
+the sun’s spectrum, only there are no dark lines. If a gas is burnt,
+and the light is allowed to pass through a prism, no bright color-bands
+appear, and no dark lines either; but instead of this, there are
+_bright lines_. Each gas or vapor has its own number of lines and its
+own arrangement. Sodium shows two bright lines, side by side. Iron
+shows sixty bright lines, arranged in a particular way.
+
+Now you see how a row of bright colors without bands of color may
+appear. But what about color-bands and dark lines together? That
+discovery came latest. It was found that if a white-hot metal were
+burned, and if its light were allowed before touching the prism to
+shine through the flame of a burning gas, _then_ there were dark lines
+showing in the colored bands. These dark lines changed in position and
+number and arrangement with each different kind of gas, just as the
+bright lines changed if the gases were burned alone. If the light of
+the burning metal passed through a flame colored with gas of sodium,
+two dark lines showed on one part of the spectrum; but if it passed
+through a flame colored with vapor of iron, sixty dark lines showed on
+another part of the spectrum.
+
+So now, by means of this spectrum analysis, we know with all but
+certainty that the sun and stars are solid, burning bodies, sending
+their light through burning, gas-laden atmospheres. By examining the
+little black lines which appear in the spectrum of one or another, it
+is possible to say the names of many metals existing as gas in those
+far-off heavenly bodies. Is not this a wonderful way of reading light?
+
+The split-up rays tell us much more than the kinds of metals in
+different stars. When a nebula is examined, and is found to give no
+spectrum of bright bands and dark lines, but only a certain number of
+bright lines, we know it to be formed of gas, unlike stars and other
+nebulæ. Also, it is by means of the spectroscope that so much has
+lately been discovered about the motions and speed of the stars coming
+towards or going from us.
+
+
+
+
+CHAPTER XXXI.
+
+STELLAR PHOTOGRAPHY.
+
+
+Photography is not only a useful handmaid to astronomy as a whole, but
+also it is so, peculiarly, to that division of astronomy with which we
+are now chiefly concerned--to spectroscopy. A few pages may therefore
+with advantage be given to the subject of celestial photography.
+
+Photography is, indeed, the greatest possible help to the astronomer.
+It pictures for him those stars which his eyes can see but dimly, or
+even can not see at all; it paints for him those light-rays of which he
+would obtain but a passing glance, and which he could not accurately
+remember in all their details; it maps out for him the wide heavens,
+which he, unaided, could never do with anything like equal completeness
+by eye and hand alone.
+
+Only recently a vast photographic map of the whole sky was undertaken.
+About eighteen different observatories, in divers parts of the world,
+divided the task among them, stars down to the sixteenth magnitude
+being most carefully registered in a complete series of something like
+fifteen hundred separate photographs. The whole result, when finally
+completed, will be a grand achievement of the present century. Each
+individual star, in the entire heavens all around our earth, from the
+first to the sixteenth magnitudes, will have its exact position in
+the sky accurately known, and the smallest change in the position of
+anyone of those stars may then be detected.
+
+Even in the delicate and abstruse operation earlier described, the
+measurement of star-distances through annual parallax, photography
+again steps in. Dr. Pritchard, Savilian professor of Astronomy at
+Oxford, pressed photography into the service of this task also.
+Measurements for parallax were made under his direction upon
+photographic plates--a work of no small interest. Here, as elsewhere,
+peculiar advantages belong to the photographic method when it can be
+followed. Its records are lasting, the limited number of hours which
+are fully suitable for direct astronomical work may be employed in
+obtaining those records, and in broad daylight the examination of them
+can be carried on.
+
+One very curious use is made of star-photographs, more especially of
+the photographs of unseen stars--that is, of stars too distant or too
+dim to be detected by the eye. These photographs, when taken, may
+be afterwards looked into further with a microscope. So, first, the
+far-off, invisible suns of the universe are photographed on a prepared
+plate, with the help of a powerful telescope, this being needful to
+secure sufficient starlight; and then the tiny picture of those suns is
+examined more closely with the help of a powerful microscope.
+
+Spectroscopy has much to say to us. It tells us about the positions
+of the different stars. It tells us about the structure of the stars.
+It tells us about the various classes to which the various stars
+belong. And also it tells us about the motions of the stars--not mere
+apparent motions, caused by movements of our own earth, but true onward
+journeyings of the stars themselves through the depths of space.
+
+For by means of photography we do not obtain simple pictures of
+the stars themselves _only_, but pictures also of the _spectra_ of
+the stars. An instrument is made uniting the spectroscope with the
+photographic apparatus, and this is called a spectrograph. By its
+means the disintegrated or broken-up star-ray is photographed in its
+broken-up condition, so that an exact picture is obtained of the bands
+and lines characteristic of any particular star.
+
+No easy matter, as may be imagined, are these spectroscopic
+observations and these spectroscopic photographings of the stars. To
+bring the image of a star exactly opposite a slender opening or slit,
+perhaps only about the _three-hundredth part of an inch in width_,
+and to keep it there, is a task which might well be looked upon as
+practically impossible.
+
+No sooner is a star found in the field of a telescope than it vanishes
+again. As the astronomer gazes, the ground beneath him is ever whirling
+onward, leaving the star behind; and although clockwork apparatus in
+all observatories of any importance is made to counteract this motion
+of the earth, and to keep the heavenly object, whether star or moon, or
+comet, within view by following its apparent motion, yet, as can easily
+be imagined, to follow thus the seeming motion of a dim star through an
+opening so minute, demands exceeding care and delicacy of adjustment.
+
+It is not indeed, for purposes of analysis, _always_ needful to pass
+the light of a star through a narrow slit. In the case of a nearer
+body, such as the sun or moon or one of the planets, light flows
+from all parts of the body, one ray crossing another; and for the
+examination of such light, a slit is imperatively needed, all side-rays
+having to be cut off. But the whole of the brightest star in the sky
+is only one point of light to us, and a slitless telescope may be
+used with no confused results. Where, however, direct comparison is
+required, the star-lines being made to appear, side by side or above
+and below, with the solar spectrum, or with the lines of earthly
+metals, then the slit becomes unavoidable.
+
+By such comparison of the two, side by side--the light from an
+intensely-heated earthly substance and the light from a star, the rays
+of both being broken up in the spectroscope--the oneness or difference
+of lines in the rays can be easily made out.
+
+One main difficulty in such observations arises from the diminution
+of starlight, caused by its passage through a prism. If a rope of a
+dozen strands is untwisted, each of those strands is far weaker than
+the whole rope was; and each strand of color in the twisted rope of
+light is of necessity much more feeble, seen by itself, than the whole
+white ray seen in one. Another difficulty in our country generally
+is the climate, which gives so few days or hours in the year for
+effective work. Yet the full amount accomplished by seizing upon every
+possible opportunity is, in the aggregate, astonishing. A third and
+very pressing difficulty attendant upon examination of star-spectra is
+caused by the incessant motion of our air, through which, as through
+a veil, all observations have to be made. The astronomer can never
+get away from the atmosphere; and unless the air be very still--that
+is to say, as still as it ever can remain--the spectrum-lines are
+so uncertainly seen as to make satisfactory results impossible. Dr.
+Huggins has sometimes passed hours in the examination of a single line,
+unable to determine whether or no it precisely coincided with the
+comparison-line of some earthly substance. In _this_ matter, no leaping
+at conclusions is admissible.
+
+The photography of stars would be easy enough if one could just
+expose a plate to the shining of the star, and there leave it to be
+impressed--there leave the star-ray to sketch slowly its own image. But
+this is hardly possible. The unceasing motion of the earth, causing
+the star perpetually to pass away from the telescopic field, and the
+exceeding narrowness of the slit opposite to which the star has to
+be kept in a stationary position, make the most accurate adjustment
+needful.
+
+Clockwork alone can not be trusted. If it could, the star and the
+photographic apparatus might be comfortably “fixed,” and left to do
+their own work. Instead of which, while a photograph is proceeding,
+it is desirable that an observer should sit gazing patiently at
+the telescope-tube, where the image of the star is seen, ready at
+any moment to correct by a touch the slightest irregularity in the
+clockwork motion of the telescope, and so to prevent a blurred and
+spoilt reproduction of the star, or of its spectrum.
+
+One hour, two hours, three hours, at a stretch, this unceasing
+watchfulness may have to be kept up, and no small amount of enthusiasm
+in the cause of science is requisite for so monotonous and wearying a
+vigil.
+
+As noted earlier, it has been found possible, if the photograph of a
+star or nebula is not completed in one night, to renew the work and
+carry it on the next night, or even for many nights in succession. This
+is especially practicable in spectroscopic photography.
+
+From four to five hours, sometimes from eight to ten hours, may
+be needful before the clear image of the star or of its spectrum
+appears--a dim little star probably to us, yet perhaps in reality a
+splendid sun, shedding warmth and light and life upon any number of
+such worlds as ours.
+
+Eight or ten hours of photography at one stretch with a star are
+impossible; for the stars, ever seemingly on the move, do not remain
+long enough in a good position. For three to six hours, a telescope may
+be made, by means of its clockwork machinery, to keep a star steadily
+in sight, and all that while the photograph is progressing. If further
+exposure is needed, the process has to be resumed the next night.
+
+The more one considers the matter, the more plainly one perceives how
+enormously our powers of sky-observation are increased by photography.
+It is not only that one photographer, with his apparatus, may
+accomplish in a single night the work of many astronomers who have
+to depend upon the power of the eye alone. It is not only that, with
+the help of photography, as much can now be done in a lifetime as
+formerly must have occupied many generations. It is not only that the
+photograph, once taken, remains a permanent possession, instead of a
+record, more or less imperfect, in which otherwise the astronomer would
+have to trust.
+
+It is not even only that in the photograph details come out which could
+not be detected by the eye, and that stars are actually brought to our
+knowledge which no man has ever seen, which perhaps no man ever will
+see from this earth with the assistance of the most powerful telescope.
+For the weak shining, which can by no possibility make itself felt by
+the retina of a man’s eye, _can_ slowly impress its picture on the
+photographic plate. Hundreds of stars, thousands of stars, utterly
+invisible to man, have had their photographs taken as truly as you have
+had your photograph taken, and by the same process, only it has been a
+longer business.
+
+But in addition to all this, we see reproduced upon the plate those
+ultra-violet and infra-red portions of the spectrum of light which but
+for the handmaid, photography, would still be to us as things which
+have no existence. And by means of photography we can observe and study
+in those same unseen portions of the spectra, when looking into a ray
+from sun or star, the innumerable dark lines, every one of which has
+its own tale to tell. To these tales we must have remained blind and
+deaf, but for photographic aid to our limited powers.
+
+Look at some dim star in the sky, and try how long you can gaze without
+blinking. You will very soon find that you have done your best, and
+that to gaze longer only means a sense of fatigue in your eyes, a
+growing dimness in the star. How different with the photographic plate!
+There, no exertion is wasted, no weariness is felt. Faint though the
+light may be, which travels earthward and falls upon the plate, it is
+all collected, all used.
+
+It is easy to photograph the sun, and this has been done. When we come
+to the moon the operation is more difficult on account of the feeble
+intensity of its light, and the difference of tint of the various parts
+of its surface. Skill and perseverance have, however, surmounted the
+greatest difficulties, and now we have photographs of the moon enlarged
+to more than a yard in diameter, which show the smallest details with a
+truly admirable clearness.
+
+In the first second of time, your eye receives as much light from the
+star as does the photographic plate in the same time. But during the
+course of one hour, the plate receives and stores up about thirty-six
+hundred times as much light as it or you received in the first instant.
+There is the secret of the matter. The photographic plate does not only
+receive, it can also keep and treasure up the light, and that our eyes
+are not able to do.
+
+If you magnify the amount received in one hour by five or ten, and
+remember that it is all retained, then you will begin to understand
+how feeble stars, unseen by man, should become known to us through
+photography.
+
+
+
+
+CHAPTER XXXII.
+
+THE DAWN OF ASTRONOMY.
+
+
+The beginnings of astronomy lie in the distance of earliest historical
+ages. It is no easy matter to say when first, in all probability, this
+science grew into existence. Astronomy was alive before the British
+nation was heard of; before Saxons or Franks had sprung into being;
+before the Roman Empire extended its iron rule; before the Grecian
+Empire began to flourish; before the Persian Empire gained power;
+before the yet earlier Assyrian Empire held sway.
+
+Among the ancient Chaldeans were devoted star-gazers--much more devoted
+than the ordinary run of educated Anglo-Saxons in this present century.
+They earnestly sought, in the dim light of those ages, to decipher the
+meaning of heaven’s countless lamps. We have better instruments, and
+more practiced modes of reasoning; also, we have the collected piles
+of knowledge built up by our forefathers through tens of centuries.
+Yet our search is in essence the same as was theirs, to know the truth
+about the stars: not merely to start some attractive theory, and then
+to prove that our theory must be right, because we have been so clever
+as to start it; but to discover that which is in those regions of
+space. No lower aim than this is worthy to be called scientific.
+
+Mistakes, of course, are made; how should it be otherwise? A man
+finding his way at night, for the first time, through a wild and
+unknown country, will almost certainly take some wrong turns before
+he discovers the right road. In astronomy, as in all other natural
+sciences, blunders are a necessity if advance is to be made. We have
+to grope our way to knowledge through observation and conjecture; in
+simpler terms, through gazing and guessing. Observation of facts leads
+to conjecture as to the possible causes for those facts; and each
+conjecture is proved by later observation to be either right or wrong.
+If proved to be right, it takes its place among accepted truths; if
+proved to be wrong, it is flung aside. Some pet delusions die hard,
+because of people’s love for them.
+
+Astronomy, as an infant science, mixed up with astrology, existed
+in the days when the Pyramids were juvenile, and when the Assyrian
+sculptures were modern. How much farther back who shall say? By
+astrology, those who studied the heavens endeavored to determine
+the fate of men and of nations, to predict events, and to interpret
+results. They paid particular attention to the aspect of the planets,
+and the general appearance of the firmament.
+
+These observations were at first simple remarks made by the shepherds
+of the Himalayas after sunset and before sunrise: The phases of the
+moon, and diurnal retrograde motion of that body with reference to
+the sun and stars; the apparent motion of the starry sky accomplished
+silently above our heads; the movements of the beautiful planets
+through the constellations; the shooting star, which seems to fall
+from the heavens; eclipses of the sun and moon, mysterious subjects
+of terror; curious comets, which appear with disheveled hair in
+the heights of heaven,--such were the first subjects of these old
+observations made during thousands of years.
+
+The ancient Chaldean star-gazers had rivals among the early Egyptians;
+and the Chinese profess to have kept actual record of eclipses during
+between three and four thousand years. The earlier records are not
+trustworthy; but of thirty-six eclipses reckoned by the Chinese sage,
+Confucius, no less than thirty-one have been proved true by modern
+astronomers.
+
+We can not name with certainty those people whose shepherds first gazed
+with intelligent eyes upon the midnight sky, and noted the steady sweep
+of stars across the firmament--intelligent eyes, that is to say, so
+far as man then knew how to use his eyes intelligently; so far as man
+had begun to note anything in nature, to watch, to compare, and to
+conjecture causes.
+
+In those times, and indeed for long afterwards, men thought much
+more about the “influences” of stars upon their own lives, and about
+supposed prophecies of the future to be read in the sky, than about the
+actual physical condition of the stars themselves, or the causes and
+meanings of the various phenomena observed in the heavens.
+
+The desire to know, for the pure delight of knowing, had perhaps hardly
+begun to dawn upon the mind of man. What people did want to know was
+what might be going to happen to themselves; whether _they_ would be
+happy or unhappy; and the stars were chiefly of interest as appearing
+to tell beforehand of troubles or joys to come.
+
+The wisest of men in those times knew less of the outspread heavens
+than many a child now knows in our public schools. Earth and sky were
+one vast bewildering puzzle. They had to discover everything for
+themselves--how the sun rose each morning and set each evening; how the
+seasons changed in steady sequence through the year; how the moon and
+stars journeyed in the night; how the ocean-tides went and came; how
+numberless every-day phenomena took place.
+
+In olden days the daily rising and setting of the sun was a mystery,
+accounted for by divers theories, none of which were right; and the
+march of stars across the midnight sky was a complete puzzle; and an
+eclipse of sun or moon was a fearful perplexity; and the tides of
+ocean were a great bewilderment. These things are mysteries still to
+barbarous nations; but they perplex us no longer, because we have found
+out the mode in which such movements, or appearances of movement, are
+brought about through the action of quite natural causes.
+
+As a first step, in earliest times, the journey of the sun by day,
+the journeys of moon and stars by night, across the sky, could hardly
+fail to arrest attention. Very early, too, the stars were grouped into
+constellations, definite figures and names being attached to each. Many
+of the constellations are now known to us by names which belong to the
+earliest historic ages.
+
+The stars were known as “fixed,” because they continued unchangeably in
+their relative positions--that is, in the position held by each star
+with respect to its neighbor stars--although the whole array of them
+moved nightly in company; constellations rising and setting at night,
+as the sun rose and set in the day.
+
+Ages may well have passed before the planets were recognized as
+distinct from the fixed stars; ages more before any definite plan
+was noted in their wanderings. In the course of time men’s attention
+was directed to these matters; and one fact after another, of daily
+or monthly or yearly occurrence, was observed, and commented upon,
+and became familiar to the minds of people. Very slowly the first
+beginnings of systematized knowledge took shape and grew, one discovery
+being made after another, one explanation being offered after another,
+one theory being started after another.
+
+But an essential difference existed between the infantine science of
+those primitive days and the matured astronomy of these later days.
+The whole ancient science was built upon a huge mistake. Men held,
+as a fact of absolutely unquestionable certainty, that this earth
+of ours--this small whirling globe, less than eight thousand miles
+in diameter--was the center, around which sun, moon, and stars all
+revolved.
+
+The Greek philosopher Thales, who lived about six hundred years before
+Christ, is said to have laid the foundations of the Grecian astronomy;
+and Pythagoras is stated to have been one of his disciples. Though, in
+many respects, Thales wandered wide of the truth, he yet taught many
+correct ideas; as, for instance, that the stars were made of fire; that
+the moon had all her light from the sun; that the earth was a sphere
+in shape, besides other facts respecting the earth’s zones and the
+sun’s apparent path in the sky. He was also one of the three ancient
+astronomers who were able to calculate and foretell eclipses.
+
+After him came numerous astronomers, of greater or less merit, in the
+Grecian and in other schools. They watched carefully; they discovered
+many things of interest; they held divers theories. But one truth never
+took firm root among them, although several of them dimly apprehended
+it; and this was the very foundation-truth, for lack of which they were
+all going hopelessly astray--the simple truth that our earth is _not_
+the center of the universe, and that our earth _does_ move. Yet it is
+not surprising. No wonder they were slow to grasp such a possibility.
+
+Anything more bewildering to the mind of ancient man than the thought
+of a solid, substantial world floating in empty space, supported upon
+nothing, upheld by nothing, can hardly be imagined. As yet little was
+known of the controlling laws or forces of nature, and that little was
+with reference only to our earth. The very suspicion of gravitation
+as a universal law lay in the far-distant future, waiting for the
+intellect of a Newton to call it out of apparent chaos; and the
+delicate balance of forces, by means of which the Solar System may
+almost be said to exist, could not be so much as guessed at.
+
+So men still clung to the thought of earth as the center of all things,
+and still believed in a little sun, busily circling round her once in
+every twenty-four hours.
+
+Perhaps the greatest of all ancient astronomers was Hipparchus, about
+150 B. C., who did more than any other in those early times to gather
+together the scattered facts of astronomy, and to arrange them into
+one united and orderly whole. He it was who discovered the precession
+of the equinoxes. He studied eclipses and the motions of the various
+planets. He made elaborate and valuable astronomical tables and
+star-catalogues; but he, like others, failed to discover the gigantic
+error which lay at the root of the whole ancient science.
+
+Despite this great mistake, still persistently believed in, and despite
+the crude notions of early astronomers on many points, it is marvelous
+how much they did manage to observe and to learn for themselves,--as
+to the sun and his apparent path, as to the moon and her path, as to
+the five then known planets and their paths, as to eclipses and other
+phenomena.
+
+By all such careful watching, although they to some extent missed their
+aim and fell into mistakes, yet they paved a way to later discoveries
+and to fuller knowledge. Their work was not thrown away, their trouble
+was not lost; for out of their very errors grew the fair form of truth.
+
+Nearly three hundred years after the time of Hipparchus came the famous
+Ptolemy--famous, not, like certain other astronomers, for stupendous
+genius, or for the brilliancy and accuracy of his observations, but
+rather noted for the ingenuity of his explanations, and for the adroit
+manner in which he systematized such knowledge, on the subject of the
+heavenly bodies, as was then in the possession of mankind.
+
+Ptolemy’s name is best known in connection with what is commonly called
+“The Ptolemaic System of the Universe,” and his greatest astronomical
+work is best known as the _Almagest_.
+
+A great many of Ptolemy’s leading notions, as well as the principal
+mass of facts upon which he worked, were doubtless borrowed from
+Hipparchus. The latter is said to have explained the movements of the
+sun and of the moon by means of small epicycles, traveling round the
+earth on circular orbits; and even Hipparchus did not originate this
+fundamental idea of the so-called “Ptolemaic System,” which had indeed
+been held by the ancients in much earlier days. Hipparchus worked it
+out to some extent, and Ptolemy carried on the process much farther,
+giving forth the system to the world in such wise that ever since it
+has gone by his name.
+
+The theory of cycles and epicycles lasted long--lasted from the time
+of Ptolemy in the second century to the time of Copernicus in the
+sixteenth century, of whom we have already spoken.
+
+[For about two thousand years, astronomers observed attentively the
+apparent revolutions of the heavenly bodies, and this attentive study
+gradually showed them a large number of irregularities and inexplicable
+complications, until at last they recognized that they were deceived as
+to the earth’s position, in the same way that they had been deceived
+as to its stability. The immortal Copernicus, in particular, discussed
+with perseverance the earth’s motion, already previously suspected for
+two thousand years, but always rejected by man’s self-love; and when
+this learned Polish canon bid adieu to our world in the year 1543, he
+bequeathed to science his great work, which demonstrated clearly the
+long-standing error of mankind.--_F._]
+
+The new theory of Copernicus had to make its way slowly against
+the dead weight of unreasoning public opinion, and against
+wrongly-reasoning hierarchical opposition. In time, gradually, despite
+all resistance, the truth made its way, and was generally received,
+though not till Galileo had been forced by ecclesiastical authority to
+recant his opinions. All the same, Copernicus, Kepler, Galileo, were
+right; public sentiment and the Church were wrong,--the earth did move,
+and was not the fixed universe center, and, by and by, those who lived
+on earth had to acknowledge the same.
+
+The succession of these great men is interesting to note. Between the
+two shining lights, Hipparchus and Ptolemy, nearly three hundred years
+intervened. But as the history of the world advances, we find brilliant
+scientific minds appearing more quickly, one following close upon
+another, instead of their being divided by long intervals of blankness.
+
+Within thirty years from the death of Copernicus, were born two mighty
+men of Science: Kepler, who lived till 1630; and Galileo, who lived
+till 1642, when England was plunged in civil strife.
+
+Between Copernicus and Kepler came Tycho Brahe. Copernicus was a
+Roman ecclesiastic, born in Poland. Tycho Brahe was a wealthy Danish
+nobleman, an ardent lover of astronomy, and a most patient and accurate
+observer. But Tycho held fast by the old astronomy. He was not
+convinced by the arguments of Copernicus. To him, earth was still the
+motionless center of all things. He was willing to allow that the rest
+of the planets circled round the sun, as an explanation of things which
+he could not help seeing; but the sun itself had still, in Tycho’s
+imagination, to revolve daily, with planets and stars and the whole
+sky, round our earth.
+
+As an explainer of causes, therefore, Tycho rose to no lofty heights.
+The real good which he did was in watching and noting actual phenomena,
+not in trying to explain how those phenomena were brought about. This
+was left for one of his young pupils, a sickly German lad, named John
+Kepler.
+
+In later years, Kepler made a grand use of his master’s mass of careful
+and thoroughly dependable observations. These had really been gathered
+together by Tycho, with a view of disproving the Copernican theory, and
+of establishing the main features of the olden astronomy, with certain
+improvements. But Kepler used the accumulated information to disprove
+the old astronomy, and to establish the truth of the new Copernican
+system which Tycho had rejected. He found a vast advantage, ready to
+his hand, in the collection of careful observations systematically
+worked out by Tycho in his observatory during many a long year. And
+Kepler did not fail to use his advantage.
+
+The planets still refused, as they always had refused, to keep to the
+paths marked out for them by astronomers. Kepler grappled with the
+difficulty. He particularly turned his attention to Mars, that near
+neighbor of ours, in which we are all now so much interested. A long
+series of close observations of Mars’s movements, made by Tycho in the
+course of many years, lay before him; and he knew that he could depend
+upon the absolute honesty and accuracy of Tycho’s work.
+
+With immense labor and immense patience, he went into the matter, still
+clinging to the old idea of a circular pathway round the sun. He tried
+things this way and that way. He placed his orbit in imagination after
+one mode and another mode; he conjectured various arrangements; he
+tested and proved them in turn, comparing each plan with observations
+made,--and still Mars defied all his efforts; still the little world
+went persistently wrong, traveling contrary to every theory.
+
+Thus far, nobody had ever thought of an orbit of any other shape than
+a circle. When a straightforward journey round a circle was found
+impossible, then epicycles were introduced to explain the planet’s
+perplexing motions. No one had dreamt of an elliptic pathway. But
+suddenly a gleam of daylight came upon this groping in the dark. What
+if Mars traveled round the sun--_not_ in a circle, but in an oval?
+
+Kepler tried this oval and that oval, comparing observations
+past--testing, examining, proving or disproving, with unwearied
+patience. And at length he found, beyond dispute, that Mars actually
+did travel round the sun in a yearly pathway, which was shaped, not as
+a circle, but as the kind of oval known as an _ellipse_; and, further,
+that the sun was not in the exact center of this ellipse, but to one
+side of the center, in one of the foci. Kepler’s success in detecting
+the true shape of a planetary orbit is doubtless owing to the fact
+that the orbit of Mars makes a wider departure from the circular form
+than any of the other important planets.
+
+One step further would have led Kepler to the knowledge that comets
+also travel in elliptic orbits--only in very long and narrow ones
+generally. But he had quite made up his mind that all comets merely
+paid our sun one visit, and never by any chance returned; so he did not
+trouble himself to enter into calculations with respect to them. This
+taking for granted of ideas long held was a very common practice in
+those days.
+
+The above wonderful discovery of elliptic orbits, in place of
+circular orbits, was only one among many made by the illustrious
+Kepler--discoveries not carelessly hit upon, as one might pick up in
+the street a valuable stone which somebody had dropped, but earnestly
+sought for, and found with toil and diligence, as gems are first
+found in foreign lands, after much seeking and long patience. Casual
+discoveries in science are rare. Attainment is far more usually made
+through intense study, through hard work, through profound thought,
+through a gradual groping upward out of darkness to the point where
+daylight breaks forth.
+
+The three well-known “Laws of Kepler” still lie at the very foundation
+of the modern system of astronomy. They are: First, every planet moves
+in an elliptical orbit, in one focus of which the sun is situated;
+second, the line drawn from the sun to a planet moves over equal areas
+in equal times; and, third, the square of the periodic times of the
+planets varies inversely as the cubes of their distances.
+
+
+
+
+CHAPTER XXXIII.
+
+MODERN ASTRONOMY.
+
+
+Still, however, the world was not convinced of the truth of the
+Copernican system. One man here or there saw and acknowledged its
+reality. The mass of mankind continued firmly to believe that they
+dwelt at the universe center, and utterly to scout the idea of a moving
+earth. Indeed, it may be very much doubted whether, not merely the
+mass of mankind, but even the most civilized and cultivated portion of
+that mass, had as yet, to any wide extent, heard a whisper of the new
+theories. Knowledge, in those days, traveled from place to place with
+exceeding deliberation.
+
+Another great man arose, contemporary with Kepler--a man whose story
+seizes more strongly upon our imagination than that of the severe and
+successful studies of Kepler. From an ordinary worldly point of view,
+Kepler would hardly be looked upon as altogether a successful man. He
+was poor, and in sickly health. His chief book was promptly prohibited
+by Rome--then a power in the whole reading world of Europe to an extent
+which can hardly be realized in these days of freedom. Kepler’s book
+was placed in the forbidden category, side by side with the dying
+publication of Copernicus. This checked all hope of literary gains, and
+life with Kepler was one long struggle. But if he could have looked
+ahead two or three hundred years; if he could have foreseen the time
+when not a few wise men of science alone, but all the civilized world,
+including the very Church which condemned him, should meekly have
+accepted and indorsed his discoveries,--then he would have been able to
+gauge the measure of his own real success.
+
+Moreover, with all his troubles, Kepler was so happy as to escape
+absolute persecution. He lived in a country which knew something of
+liberty as an ideal; he was left to write and work freely; and, at
+least, no public recantation of what he held to be truth was forced
+from him.
+
+Galileo’s was a sadder tale. A Florentine of noble birth, he turned his
+attention early to science as the needle turns to the north, and before
+the age of twenty-seven he already occupied a foremost position as
+mathematical lecturer at Pisa. There it was that he direfully offended
+the philosophers of the day by proving Aristotle to be in the wrong.
+For Aristotle was the great master of the schoolmen. His philosophy
+and theories were accepted as final, and whatsoever could not be
+proved in accordance with them was regarded as untrue. Aristotle had
+declared that if two weights--the one being ten times as heavy as the
+other--were dropped together from a height, the heavier weight would
+reach the ground ten times as quickly as the lighter.
+
+Everybody believed this, and nobody had ever thought of putting it to
+the test of actual trial. Aristotle had said so, and Aristotle was
+indorsed as a whole by all the schools of Europe; and what more could
+possibly be wanted by any reasonable human being? But Galileo was not
+so easily satisfied. He looked into the matter independently, bent upon
+finding out, not what Aristotle had thought or what the Church might
+support, but simply what actually _was_.
+
+[Illustration: PROMINENT ASTRONOMERS OF THE NINETEENTH CENTURY.]
+
+Then, in view of many observers, called together for the occasion, he
+dropped, at the same instant, from the top of the leaning tower of
+Pisa, a shot weighing one pound and another shot weighing a hundred
+pounds. And, behold! both reached the ground simultaneously. There was
+not a fraction of difference between the two. To prove Aristotle wrong
+was to prove everybody wrong, the authorities of the Church included.
+Men calmly declined to believe their own eyes, and Galileo was in very
+evil odor.
+
+From falling bodies he went on to subjects of yet wider interest to
+people in general. He read about and eagerly embraced the Copernican
+system. Not only did he accept it himself, but he vigorously set
+to work to teach and convince others also. This, as might only be
+expected, aroused vehement opposition. But Galileo was still in the
+heyday of his powers, and he was not to be easily silenced. In those
+days he could afford to press onward in the teeth of resistance, and to
+laugh at men who would not listen.
+
+When at Venice, a report reached him of a certain optician in Holland
+who had happened to hit upon a curious “combination of lenses,” through
+which objects afar off could be actually seen as if they were near.
+Galileo promptly seized upon the notion, and within twenty-four hours
+he had rigged up a small, rough telescope out of an old organ-pipe and
+two spectacle-glasses.
+
+Thus the first telescope was made--a very elementary affair, formed of
+two lenses, convex and concave, and capable of magnifying some three
+times--a mere child’s toy compared with telescopes of the present day,
+but of exceeding value and interest, because it was the very first;
+because in all the history of the world no telescope had ever been
+manufactured before.
+
+This earliest effort was speedily improved upon. The next trial
+produced a tube which could magnify seven or eight times; and in a
+little while, Galileo had a telescope magnifying as much as thirty-two
+times. Even thirty-two times does not sound very startling to us; but
+in those days the revelations of such an instrument came upon men like
+a thunderclap.
+
+Through it could be seen clearly the broken nature of the moon’s
+surface--the craters, the shadows, the mountains. Through it could be
+seen the phases of Venus, which no man had ever yet detected, but which
+Copernicus had declared must certainly exist, if indeed his system
+were a reality. Through it could be seen four of the moons of Jupiter,
+and their ceaseless journeyings. Through it could be seen spots upon
+the face of the sun, the movements of which showed the rotation of the
+sun upon his axis. Through it could be seen the very curious shape of
+Saturn, caused by his rings, though a much stronger power was needed to
+separate the rings from the body of the planet.
+
+Of all these discoveries, and many others also made by Galileo, none
+seemed worse to the bigoted schoolmen of his day than the preposterous
+notion of black spots upon the sun’s face.
+
+Rather curiously, no human being seems ever before then to have noticed
+such spots, though often they are quite large enough to be detected by
+the naked eye. A general belief had been held that the sun was and must
+be perfect--an absolutely spotless and unblemished being, the purest
+symbol of celestial incorruptibility--and the said discovery went right
+in the teeth of deductions drawn from, and lessons founded upon, this
+belief. Therefore the schoolmen held out and determinedly resisted, and
+would have nought to do with Galileo or his telescopes, shutting their
+eyes to marvels newly revealed.
+
+But Kepler was a true scientist, a man who earnestly pursued truth,
+and sought to discover it at any hazard. He and Galileo were
+contemporaries, and they held communication on these subjects. Some
+of Galileo’s discoveries went quite as much in the teeth of some of
+Kepler’s most dearly-loved theories as they did in the teeth of the
+schoolmen’s most dearly-loved doctrines. Yet, none the less, Kepler
+welcomed them with great delight and eagerness, showing thereby his
+true greatness of character.
+
+Till after the age of fifty, Galileo was allowed to go on undisturbed,
+or at least not materially disturbed, by opposition in his career of
+success--observing, learning, theorizing, calculating, explaining,
+teaching--a prominent figure indeed. Not only did he take a large share
+in establishing firmly the Copernican system of astronomy, but some of
+the principal laws of motion were discovered by him. He first found
+the uses of a pendulum, and there is strong reason for believing that
+the first microscope, as well as the first telescope, was from his
+hands.
+
+But after the age of fifty, reverses came, and one blow succeeded
+another. Rome had been gradually waking up to the true sense of all
+that was implied by his discoveries and his teaching, and at length she
+let loose her thunders--impotent thunders enough, so far as regarded
+any permanent checking of the progress of truth, but by no means
+impotent to crush one defenseless victim, the champion of scientific
+truth in that country and age.
+
+Years of greater or less opposition, amounting often to persecution,
+were followed by an imperious order commanding him to Rome. There he
+was examined and severely “questioned,” and recantation was forced from
+him, worth as much as such forced recantations commonly are worth.
+
+Even then he did not cease from the work that he loved; even in prison
+he carried it on; even when he might not write, nothing could stop him
+from thinking. But his health was broken; his liberty was taken away;
+illness followed illness; his favorite daughter died; his eyesight
+gradually failed; the last book that he wrote might not for a long
+while be printed; and at last he passed away, mercifully set free from
+those who, in an essentially bigoted and intolerant age, were incapable
+of appreciating his greatness.
+
+They would fain _then_ have denied him even a respectable grave. Now,
+all the civilized world unites to honor the name of Galileo.
+
+
+
+
+CHAPTER XXXIII.
+
+ISAAC NEWTON.
+
+
+Even the great fame of Galileo must be relegated to a second place in
+comparison with that of the philosopher who first saw the light in a
+Lincolnshire farmhouse on the 25th of December, 1642, the very same
+year of Galileo’s death. His father, Isaac Newton, had died before his
+birth. The little Isaac was at first so frail and weakly that his life
+was despaired of. The watchful mother, however, tended her delicate
+child with such success that he ultimately acquired a frame strong
+enough to outlast the ordinary span of human life.
+
+In due time the boy was sent to the public school at Grantham. That
+he might be near his work, he was boarded at the house of Mr. Clark,
+an apothecary. He had at first a very low place in the class. His
+first incentive to diligent study seems to have been derived from the
+circumstance that he was severely kicked by one of the boys above
+him in the class. This indignity had the effect of stimulating young
+Newton’s activity to such an extent that he not only attained the
+desired object of passing over the head of the boy who had maltreated
+him, but continued to rise until he became the head of the school.
+
+The play-hours of the great philosopher were devoted to pursuits very
+different from those of most schoolboys. His chief amusement was
+found in making mechanical toys, and various ingenious contrivances.
+He watched, day by day, with great interest, the workmen engaged in
+constructing a windmill in the neighborhood of the school, the result,
+of which was that the boy made a working model of the windmill and of
+its machinery, which seems to have been much admired as indicating his
+aptitude for mechanics. We are told that he also indulged in somewhat
+higher flights of mechanical enterprise. The first philosophical
+instrument he made was a clock, which was actuated by water. He also
+devoted much attention to the construction of paper kites, and his
+skill in this respect was highly appreciated by his schoolfellows. Like
+a true philosopher, even at this stage, he experimented on the best
+methods of attaching the string, and on the proportions which the tail
+ought to have.
+
+When the schoolboy at Grantham was fourteen years of age, it was
+thought necessary to recall him from the school. His recently-born
+industry had been such that he had already made good progress in his
+studies, and his mother hoped that he would now lay aside his books,
+and those silent meditations to which, even at this early age, he had
+become addicted. It was hoped that instead of such pursuits, which were
+deemed quite useless, the boy would enter busily into the duties of
+the farm and the details of a country life. But before long it became
+manifest that the study of nature and the pursuit of knowledge had such
+a fascination for the youth that he could give little attention to
+aught else. It was plain that he would make but an indifferent farmer.
+He greatly preferred experimenting on water-wheels, and working at
+mathematics in the shadow of a hedge.
+
+Fortunately for humanity, his mother, like a wise woman, determined
+to let her boy’s genius have the scope which it required. He was
+accordingly sent back to Grantham school, with the object of being
+trained in the knowledge which would fit him for entering the
+University of Cambridge.
+
+It was the 5th of June, 1660, when Isaac Newton, a youth of eighteen,
+was enrolled as an undergraduate of Trinity College, Cambridge. Little
+did those who sent him there dream that this boy was destined to be the
+most illustrious student who ever entered the portals of that great
+seat of learning. Little could the youth himself have foreseen that the
+rooms near the gateway which he occupied would acquire a celebrity from
+the fact that he dwelt in them, or that the antechapel of his college
+was in good time to be adorned by that noble statue of himself which
+is regarded as the chief art treasure of Cambridge University, both
+on account of its intrinsic beauty and the fact that it commemorates
+the fame of her most distinguished alumnus, Isaac Newton, the immortal
+astronomer. His advent at the university seemed to have been by
+no means auspicious or brilliant. His birth was, as we have seen,
+comparatively obscure, and though he had already given indication of
+his capacity for reflecting on philosophical matters, yet he seems to
+have been but ill-equipped with the routine knowledge which youths are
+generally expected to take with them to the universities.
+
+From the outset of his college career, Newton’s attention seems to have
+been mainly directed to mathematics. Here he began to give evidence of
+that marvelous insight into the deep secrets of nature which, more than
+a century later, led so dispassionate a judge as Laplace to pronounce
+Newton’s immortal work as pre-eminent above all the productions of
+the human intellect. But though Newton was one of the very greatest
+mathematicians that ever lived, he was never a mathematician for the
+mere sake of mathematics. He employed his mathematics as an instrument
+for discovering the laws of nature.
+
+His industry and genius soon brought him under the notice of the
+university authorities. It is stated in the university records that
+he obtained a scholarship in 1664. Two years later we find that
+Newton, as well as many residents in the university, had to leave
+Cambridge temporarily on account of the breaking out of the plague. The
+philosopher retired for a season to his old home at Woolsthorpe, and
+there he remained until he was appointed a Fellow of Trinity College,
+Cambridge, in 1667. From this time onwards, Newton’s reputation as a
+mathematician and as a natural philosopher steadily advanced, so that
+in 1669, while still but twenty-seven years of age, he was appointed to
+the distinguished position of professor of Mathematics at Cambridge.
+Here he found the opportunity to continue and develop that marvelous
+career of discovery which formed his life’s work.
+
+The earliest of Newton’s great achievements in natural philosophy was
+his detection of the composite character of light. That a beam of
+ordinary sunlight is, in fact, a mixture of a very great number of
+different colored lights, is a doctrine now familiar to every one who
+has the slightest education in physical science. We must, however,
+remember that this discovery was really a tremendous advance in
+knowledge at the time when Newton announced it.
+
+[Illustration: SIR ISAAC NEWTON.]
+
+A certain story is often told about Newton. It is said that as he
+sat in a garden an apple fell from a tree, and that its fall set him
+thinking, and that, in consequence of this train of thought, he found
+out all about the law of attraction or gravitation.
+
+But the fall of an apple could not possibly have set Newton thinking,
+because he had already been thinking long and hard upon these
+difficult questions. Indeed, it was _because_ he had been so thinking,
+_because_ his mind was in a watchful and receptive condition, that so
+slight a matter as a falling apple should, perhaps, have suggested to
+him a useful train of ideas.
+
+Newton was a man who really did think, and who really did think
+intensely. He was not, like the ordinary run of people, one who merely
+had a good many notions walking loosely through his brain. He would
+bend his mind to a subject and be absolutely absorbed in it; later in
+life so absorbed that he would forget to finish his dressing, and would
+be unable to say whether or no he had dined. This sort of forgetfulness
+does sometimes spring from vacancy of mind; but with Newton it arose
+from fullness of thought.
+
+An apple falls, of course, as a stone or any other body falls, because
+the earth attracts it. Otherwise, it might as easily rise and float
+away into the sky. But this was known perfectly well long before
+Newton’s days. It was clearly understood that the earth had a curious
+power of drawing all things towards herself. People could not explain
+why or how it was so; neither can we explain now; but they were fully
+aware of the fact.
+
+So men knew something of the force called gravity; but they knew it
+mainly, almost exclusively, as having to do with our earth, and with
+the things upon our earth. They had not begun definitely to think of
+gravity as having to do with bodies in the heavens; as being a chief
+controlling force in the whole Solar System; much less as reigning
+throughout the vast universe of stars. It had not come into their
+minds with any distinctness that, just as the earth pulls towards her
+own center a mountain, a horse, a man, so the sun pulls toward his
+center the earth, the moon, and all the planets.
+
+Certain glimmerings of the notion had, indeed, begun to dawn on the
+horizon of learning. Horrocks, Borelli, Robert Hook, Wren, Halley, and
+others had _glimpses_ of universal gravitation; but only glimpses. A
+gifted English philosopher, late in the sixteenth century, Gilbert
+by name, went so far as to speak of earth and moon acting one upon
+the other “like two magnets.” He also saw the effect of the moon’s
+attraction in bringing about ocean tides, though he oddly explained
+that the said attraction was not so much exerted upon ocean waters as
+upon “subterranean spirits and humors”--whatever he may have meant by
+such an expression.
+
+Kepler, not long after Gilbert, made further advance. He gained some
+definite notions as to the nature of gravity; and he saw distinctly
+that the moon’s attraction was the main cause of the tides. The
+following remarkable statement is found in his writings: “If the earth
+ceased to attract its waters, the whole sea would mount up and unite
+itself with the moon. The sphere of the attracting force of the moon
+extends even to the earth, and draws the waters towards the torrid
+zone, so that they rise to the point which has the moon in the zenith.”
+Here is a distinct enough grasp of the fact that gravity can and does
+act through distance, between worlds separated by thousands of miles.
+
+Yet, though both Gilbert and Kepler saw so much, they failed to go
+farther. Neither of the two had any clear knowledge of the modes in
+which gravitation acts, or of the laws which govern its working.
+Gilbert and Kepler alike, while dimly recognizing, not only the moon’s
+attraction for earth’s oceans, but the mutual attraction of earth and
+moon each for the other, were utterly perplexed as to what force could
+possibly hold the two bodies asunder. Gilbert could seriously talk of
+“subterranean spirits and humors.” Kepler could soberly write of an
+“animal force” or some tantamount power in the moon, which prevented
+her nearer approach to earth.
+
+Galileo was equally vague on the subject. With all his brilliant gifts,
+and while acknowledging the earth’s attractive power over the moon, he
+would not even admit the existence of _mutual_ attraction, and talked
+of the moon as being compelled to “follow the earth.” Unquestionably
+there are times when the moon does follow the earth, and that is when
+the earth happens to go before. But quite as often it happens that the
+moon goes before, and the earth follows after.
+
+All these great men were groping near the truth, yet none managed to
+find the clue that was wanted. They left the unfinished process of
+thought to be carried on by the master-mind of Newton. And Newton set
+himself to think the question out. He used Kepler’s observations.
+He sought to penetrate the secrets of a Solar System in mysterious
+and inviolable order. Some reason or cause for that order he knew
+must exist--if only it might be grasped! He pondered deeply; lost in
+profound cogitation, through stormy days of civil strife, of plague and
+loss and suffering. The object of his life was to discover, if so he
+might, what power or what forces retained the different worlds in their
+respective pathways; in short, what manner of celestial guidance was
+vouchsafed to the planets.
+
+For although men had now learned the shape of the planet-orbits, and
+even knew certain laws which helped to govern the planet-motions, they
+had not discovered one supreme controlling law. They did not dream of
+gravity in the heavens as a prevailing force. There was absolutely no
+reason, with which men were acquainted, why each planet should preserve
+its own particular distance from the sun; why Mars should not wander
+as far away as Jupiter; why Mercury should not flee to the position of
+Saturn; why our own earth should be always about as near as she always
+is.
+
+The resources of Newton’s genius seemed equal to almost any demand
+that could be made upon it. He saw that each planet must disturb the
+other, and in that way he was able to render a satisfactory account of
+certain phenomena which had perplexed all preceding investigators. That
+mysterious movement by which the pole of the earth sways about among
+the stars, had been long an unsolved enigma; but Newton showed that the
+moon grasped with its attraction the protuberant mass at the equatorial
+regions of the earth, and thus tilted the earth’s axis in a way that
+accounted for the phenomenon which had been known, but had never been
+explained, for two thousand years. All these discoveries were brought
+together in that immortal work, Newton’s “Principia,” the greatest work
+on science that the world had yet seen.
+
+It may well be that, as Newton pondered this perplexing question
+while seated in the garden, an apple dropping to the ground might
+have sufficed to turn his wide-awake and ready mind in the direction
+of that familiar force, gravity, which draws all loose bodies towards
+earth’s surface. The apple fell because of gravity. Quite naturally the
+question might have arisen in Newton’s mind--“Why not this same gravity
+in the heavens also? If the earth draws an apple towards herself, why
+should not the earth draw the moon? Why should not the sun draw the
+earth? Nay, more, why should not the sun draw all the planets?” Newton
+set himself to work out this problem, allowing for the distance of the
+moon from earth, and for the bulk and weight of both earth and moon.
+
+And because the answer was _not_ precisely what he had looked for,
+he put the calculation aside, and waited for years. It seems that he
+mentioned his conjecture to no living person. After many years he took
+it up again, and worked it out afresh. By this time new measurements of
+earth’s surface, and new calculations of earth’s size had been made,
+and Newton had fresh figures to go upon. This time the answer came
+just as he had originally hoped, and the truth of his surmise was thus
+proved.
+
+Gravity held the moon near the earth, preventing her from wandering
+off into unknown distances. Gravity held earth and moon, Mars, Venus,
+Jupiter, each planet, in its own pathway, within a certain distance of
+the sun. Gravity held many of the comets as permanent members of the
+Solar System. So strong, indeed, was the drawing of gravity found to
+be, that only the resisting force of each bright world’s rapid rush
+round the sun could keep the sun and his planets apart.
+
+Newton had discovered the long-sought secret. He had found that “every
+particle of matter in the universe attracts every other particle?”
+He had found also the main laws which govern the working of that
+attraction--that it depends, first, upon the mass or amount of “matter”
+in each body; that it depends, secondly, upon the distance of one body
+from another. He found, too, how far attraction increases with greater
+nearness, and decreases with greater distance. All these and countless
+other questions he worked out in the course of years. But first he had
+grasped the great leading principle, after which men had until then
+groped in vain, that by the force of gravity the sun and his worlds
+and their moons are all bound together into one large united family or
+system.
+
+Though Newton lived long enough to receive the honor that his
+astonishing discoveries so justly merited, and though for many years
+of his life his renown was much greater than that of any of his
+contemporaries, yet it is not too much to say that, in the years which
+have since elapsed, Newton’s fame has been ever steadily advancing.
+
+We hardly know whether to admire more the sublime discoveries at
+which he arrived, or the extraordinary character of the intellectual
+processes by which those discoveries were reached. He died on Monday,
+March 20, 1727, in the eighty-fifth year of his age.
+
+
+
+
+CHAPTER XXXV.
+
+LATER ASTRONOMY.
+
+
+Sir William Herschel was born in the city of Hanover, November 15,
+1738. He was the second son of Isaac Herschel, a musician, who brought
+him up, with his four other sons, to his own profession.
+
+A faithful chronicler has given us an interesting account of the way in
+which Isaac Herschel educated his boys; the narrative is taken from the
+recollections of one who, at the time, was a little girl of five or six
+years old. She writes:
+
+“My brothers were often introduced as solo performers and assistants
+in the orchestra at the court, and I remember that I was frequently
+prevented from going to sleep by the lively criticisms on music
+on coming from a concert. Often I would keep myself awake that I
+might listen to their animated remarks, for it made me happy to see
+them so happy. But generally their conversation would branch out on
+philosophical subjects, when my brother William and my father often
+argued with such warmth that my mother’s interference became necessary
+when the names Euler, Leibnitz, and Newton sounded rather too loud for
+the repose of her little ones, who had to be at school by seven in the
+morning.”
+
+The child, whose reminiscences are here given, became afterwards
+the famous Caroline Herschel. The narrative of her life is a most
+interesting book, not only for the account it contains of the
+remarkable woman herself, but also because it presents the best picture
+we have of the great astronomer, to whom Caroline devoted her life.
+
+This modest family circle was, in a measure, dispersed at the outbreak
+of the Seven Years’ War in 1756. The French proceeded to invade
+Hanover, which, it will be remembered, belonged at this time to
+the British dominions. Young William Herschel had already obtained
+the position of a regular performer in the regimental band of the
+Hanoverian Guards, and it was his fortune to obtain some experience
+of actual warfare in the disastrous battle of Hastenbeck. He was not
+wounded, but he had to spend the night after the battle in a ditch, and
+his meditations on the occasion convinced him that soldiering was not
+the profession exactly suited to his tastes. He left his regiment by
+the very simple, but somewhat risky, process of desertion. He had, it
+would seem, to adopt disguises in order to effect his escape. By some
+means he succeeded in eluding detection, and reached England in safety.
+
+The young musician must have had some difficulty in providing for his
+maintenance during the first few years of his abode in England.
+
+It was not until he had reached the age of twenty-two that he succeeded
+in obtaining any regular appointment. He was then made instructor of
+music to the Durham Militia. Shortly afterwards, his talents being more
+widely recognized, he was appointed as organist of the parish Church at
+Halifax.
+
+In 1766 we find that Herschel had received the further promotion of
+organist in the Octagon Chapel, at Bath. Bath was then, as now, a
+highly fashionable resort, and many notable personages patronized the
+rising musician. Herschel had other points in his favor besides his
+professional skill; his appearance was striking, his address superb,
+and his conversation animated, interesting, and instructive; and
+even his nationality was a distinct advantage, inasmuch as he was a
+Hanoverian in the reign of King George the Third. From his earliest
+youth, Herschel had been endowed with that invaluable characteristic,
+an intense desire for knowledge. He naturally wished to perfect himself
+in the theory of music, and thus he was led to study mathematics. When
+he had once tasted the charms of mathematics, he saw vast regions of
+knowledge unfolded before him, and in this way he was induced to direct
+his attention to astronomy. More and more this pursuit engrossed his
+attention until, at last, it had become an absorbing passion.
+
+It was with quite a small telescope, which had been lent him by a
+friend, that Herschel commenced his career as an observer. However, he
+speedily discovered that to see all he wanted to see, a telescope of
+far greater power would be necessary.
+
+He commissioned a friend to procure for him in London a telescope with
+high magnifying power. Fortunately for science the price was so great
+that it precluded the purchase, and he set himself at work to construct
+one. After many trials he succeeded in making a reflecting instrument
+of five feet focal length, with which he was able to observe the rings
+of Saturn and the satellites of Jupiter.
+
+It was in 1774, when the astronomer was thirty-six years old, that he
+obtained his first glimpse of the stars with an instrument of his own
+construction. Night after night, as soon as his musical labors were
+ended, his telescopes were brought out.
+
+His sister Caroline, who occupies such a distinct place in scientific
+history, the same little girl to whom we have already referred, was
+his able assistant, and when mathematical work had to be done, she
+was ready for it. She had taught herself sufficiently to enable her
+to perform the kind of calculations--not, perhaps, very difficult
+ones--that Herschel’s work required; indeed, it is not much to say that
+the mighty life-work which this man was enabled to perform could never
+have been accomplished had it not been for the self-sacrifice of this
+ever-loving and faithful sister.
+
+It was not until 1782 that the great achievement took place by which
+Herschel at once sprang into fame. He appears to have formed a project
+for making a close examination of all the stars above a certain
+magnitude for the purpose of discovering, if possible, a parallax among
+them. Star after star was brought to the center of the field of view of
+his telescope, and after being carefully examined, was then displaced,
+while another star was brought forward to be submitted to the same
+process.
+
+In the great review which Herschel undertook, he doubtless examined
+hundreds, or perhaps thousands of stars, allowing them to pass away
+without note or comment. But on an ever-memorable night in March,
+1782, it happened that he was pursuing his task among the stars in the
+constellation of Gemini. One star was noticed which, to Herschel’s
+acute vision, seemed different from the stars which in so many
+thousands are strewn over the sky. There was something in the starlike
+object that immediately arrested his attention, and made him apply to
+it a higher magnifying power. This at once disclosed the fact that the
+object possessed a disk--that is, a definite, measurable size--and
+that it was thus totally different from any of the hundreds and
+thousands of stars which exist elsewhere in space. The organist at the
+Octagon Chapel at Bath had discovered a new planet with his home-made
+telescope. Great was the astonishment of the scientific world when the
+Bath organist announced that the five planets, which had been known
+from all antiquity, must now admit the company of a sixth.
+
+The now great astronomer was invited to Windsor, and to bring his
+famous telescope in order to exhibit the planet to George III, and
+to tell his majesty all about it. The king took so great a fancy to
+Herschel that he proposed to confer on him the title of “his majesty’s
+own astronomer,” to assign him a residence near Windsor, to provide him
+with a salary, and to furnish such funds as might be required for the
+erection of great telescopes, and for the conduct of that mighty scheme
+of celestial observation on which Herschel was so eager to enter.
+
+No single discovery of Herschel’s later years was, however, of the same
+momentous description as that which first brought him to fame. There
+is no separate collection of his writings, and very scanty accounts of
+his life have been published; but he who has written his name among the
+stars needs no other testimonial to his fame. Prior to his time the
+number of bodies known as belonging to the Solar System was eighteen,
+including secondary planets and Halley’s comet. To these he added nine;
+namely, Uranus and six satellites, and two satellites of Saturn.
+
+Though no additional honors could add to his fame, Dr. Herschel, in
+1816, received the decoration of the Guelphic Order of Knighthood.
+In 1820 he was elected president of the Astronomical Society, and
+among their Transactions, the next year, he published an interesting
+memoir on the places of one hundred and forty-five double-stars. This
+paper was the last which he lived to publish. His health had begun to
+decline, and on the 24th of August, 1822, he sank under the infirmities
+of age, having completed his eighty-fourth year. He was survived by his
+widow, Lady Herschel, an only son, Sir John F. W. Herschel, and his
+sister Caroline, who died in 1847, in her ninety-eighth year.
+
+
+LAPLACE.
+
+The author of “Celestial Mechanics” was born at Beaumont-en-Auge in
+1749, just thirteen years later than his renowned friend Lagrange.
+His father was a farmer, but appears to have been in a position to
+provide a good education for a son who seemed promising. The subject
+which first claimed his attention was theology. He was, however, soon
+introduced to the study of mathematics, in which he presently became so
+proficient that, while he was still no more than eighteen years old, he
+obtained employment as a mathematical teacher in his native town.
+
+Desiring wider opportunities for study, young Laplace started for
+Paris, being provided with letters of introduction to D’Alembert,
+who then occupied the most prominent positions as a mathematician in
+France, if not in Europe. On presenting these letters, he seems to have
+had no reply; whereupon, Laplace wrote to D’Alembert, submitting a
+discussion of some point in dynamics.
+
+This letter instantly produced the desired effect. D’Alembert thought
+that such mathematical talent as the young man displayed was in itself
+the best of introductions to his favor. It could not be overlooked, and
+accordingly he invited Laplace to come and see him. Laplace, of course,
+presented himself, and erelong D’Alembert obtained for the rising
+philosopher a professorship of Mathematics in the military school in
+Paris. This gave the brilliant young mathematician the opening for
+which he sought, and he quickly availed himself of it.
+
+Laplace’s most famous work is “Celestial Mechanics,” in which he
+essayed a comprehensive attempt to carry out, in much greater detail,
+the principles which Newton had laid down. The fact was that Newton
+had not only to construct the theory of gravitation, but he had to
+invent the mathematical processes by which his theory could be applied
+to the explanation of the movements of the heavenly bodies. In the
+course of the century which had elapsed between the time of Newton and
+the time of Laplace, mathematics had been extensively developed. The
+disturbances which one planet exercises upon the rest can only be fully
+ascertained by the aid of long calculations, and for these calculations
+analytical methods are required.
+
+With an armament of mathematical methods which had been perfected
+since the days of Newton by the labors of two or three generations of
+mathematical inventors, Laplace essayed in his “Celestial Mechanics”
+to unravel the mysteries of the heavens. It will hardly be disputed
+that the book which he has produced is one of the most difficult
+books to understand that has ever been written. The investigations of
+Laplace are, generally speaking, of too technical a character to make
+it possible to set forth any account of them in such a work as the
+present. He did, however, publish one treatise, called the “System of
+the Universe,” in which, without introducing mathematical symbols, he
+was able to give a general account of the theories of the celestial
+movements, and of the discoveries to which he and others had been led.
+In this work Laplace laid down the principles of the nebular theory,
+which, in modern days, has been generally accepted.
+
+The nebular theory gives a physical account of the origin of the
+Solar System, and has already been explained in this volume. Bach
+advance in science seems to make it more certain that this hypothesis
+substantially represents the way in which our Solar System has grown to
+its present form.
+
+Not satisfied with a career which was merely scientific, Laplace sought
+to connect himself with public affairs. Napoleon appreciated his
+genius, and desired to enlist him in the service of the state. Laplace
+was appointed to the office of minister of the interior. The experiment
+was not successful, for he was not by nature a statesman. In despair
+of Laplace’s capacity as an administrator, Napoleon declared that he
+carried the spirit of his infinitesimal calculus into the management
+of business. Indeed, Laplace’s political conduct hardly admits of much
+defense. While he accepted the honors which Napoleon showered on him in
+the time of his prosperity, he seems to have forgotten all this when
+Napoleon could no longer render him service. Laplace was made a marquis
+by Louis XVIII. During the latter part of his life the philosopher
+lived in a retired country-place at Arcueile. Here he pursued his
+studies, and, by strict abstemiousness, preserved himself from many of
+the infirmities of old age.
+
+He was endowed with remarkable scientific sagacity; but above all
+his powers his wonderful memory shone pre-eminent. His “Celestial
+Mechanics” is, next to Newton’s “Principia,” the greatest of
+astronomical works.
+
+He died on March 5, 1827, in his seventy-eighth year, his last words
+being, “What we know is but little, what we do not know is immense.”
+
+
+LEVERRIER.
+
+We are apt to identify the idea of an astronomer with that of a man
+who looks through a telescope at the stars; but the word astronomer
+has really a much wider significance. No man who ever lived has been
+more entitled to be designated an astronomer than Urbain Jean Joseph
+Leverrier, and yet it is certain that he never made a telescopic
+discovery of any kind. In mathematics, however, he excelled, and
+he simply used the observations of others as the basis of his
+calculations.
+
+These observations form, as it were, the raw material on which the
+mathematician exercises his skill. It is for him to elicit from the
+observed places the true laws which govern the movements of the
+heavenly bodies. Here is indeed a task in which the highest powers of
+the human intellect may be worthily employed. To Leverrier it has been
+given to provide a superb illustration of the success with which the
+mind of man can penetrate the deep things of nature.
+
+The illustrious Frenchman was born on the 11th of March, 1811, at
+Saint-Lô, in the department of Manche. In the famous polytechnic
+school for education in the higher branches of science he acquired
+considerable fame as a mathematician. His labors at school had revealed
+to Leverrier that he was endowed with the powers requisite for dealing
+with the subtlest instruments of mathematical analysis. When he was
+twenty-eight years old his first great astronomical investigation was
+brought forth. This was the profound calculation of the disturbances of
+the planet Uranus and the causes of them.
+
+The talent which his researches displayed brought Leverrier into
+notice. At that time the Paris Observatory was presided over by
+Arago, a savant who occupies a distinguished position in French
+scientific annals. Arago at once perceived that Leverrier possessed the
+qualifications suitable for undertaking a problem of great importance
+and difficulty that had begun to force itself on the attention of
+astronomers. What this great problem was, and how astonishing was the
+solution it received, must now be considered.
+
+Ever since Herschel brought himself into fame by the discovery of
+Uranus, the movements of this new addition to the Solar System had been
+scrutinized with care and attention. The position of Uranus was thus
+accurately determined from time to time. When due allowance was made
+for whatever influence the attraction of Jupiter and Saturn and all
+the other planets could possibly produce, the movements of Uranus were
+still inexplicable. It was perfectly obvious that there must be some
+other influence at work besides that which could be attributed to the
+planets already known.
+
+Astronomers could only recognize one solution of such a difficulty.
+It was impossible to doubt that there must be some other planet in
+addition to the bodies at that time known, and that the perturbations
+of Uranus, hitherto unaccounted for, were due to the disturbances
+caused by the action of this unknown planet. Arago urged Leverrier
+to undertake the great problem of searching for this body. But the
+conditions of the search were such that it must be conducted on
+principles wholly different from any search which had ever before been
+undertaken for a celestial object. For this was not a case in which
+mere survey with a telescope might be expected to lead to the discovery.
+
+There are in the heavens many millions of stars, and the problem of
+identifying the planet, if indeed it should lie among these stars,
+seemed a very complex matter. Of course, it is the abundant presence of
+the stars which causes the difficulty.
+
+The materials available to the mathematician for the solution of
+this problem were to be derived solely from the discrepancies between
+the calculated places in which Uranus should be found, taking into
+account the known causes of disturbances, and the actual places in
+which observation had shown the planet to exist. Here was, indeed, an
+unprecedented problem, and one of extraordinary difficulty. Leverrier,
+however, faced it, and, to the astonishment of the world, succeeded in
+carrying it through to a brilliant solution.
+
+After many trials, Leverrier ascertained that, by assuming a certain
+size, shape, and position for the unknown planet’s orbit, and a certain
+value for the mass of the hypothetical body, it would be possible
+to account for the observed disturbances of Uranus. Gradually it
+became clear to his perception, not only that the difficulties in
+the movements of Uranus could be thus explained, but that no other
+explanation need be sought for. And now for an episode in this history
+which will be celebrated so long as science shall endure. It is nothing
+less than the telescopic confirmation of the existence of this new
+planet, which had previously been indicated only by mathematical
+calculation.
+
+Great indeed was the admiration of the scientific world at this superb
+triumph. Here was a mighty planet, whose very existence was revealed by
+the indications afforded by refined mathematical calculation. At once
+the name of Leverrier, already known to those conversant with the more
+profound branches of astronomy, became everywhere celebrated.
+
+When, in 1854, Arago’s place had to be filled at the head of the great
+Paris Observatory, it was universally felt that the discoverer of
+Neptune was the suitable man to assume the office. Leverrier died on
+Sunday, September 23, 1877, in his sixty-seventh year.
+
+       *       *       *       *       *
+
+FREDERICK WILLIAM BESSEL was born at Minden in 1784, and early turned
+his attention to mathematical subjects. He devoted himself with
+ardor to astronomy, and in 1804 he undertook the reduction of the
+observations made on the comet of 1607. His results were communicated
+to Olbers, who warmly praised the young astronomer, and in 1806
+recommended him to Schroeter as an assistant in the observatory of
+Lilienthal. In 1810 he was appointed director of the new observatory
+then being founded by the king at Königsberg. He was admirably fitted
+for this post, and is distinguished mainly for his discovery of the
+parallax of the star 61 Cygni, which he accomplished by methods of
+extreme ingenuity and delicacy.
+
+Two kinds of telescopes are commonly used, the refractor and the
+reflector. The first telescopes made were all refractors, and the very
+first of them was made, as you know, by Galileo. The first reflector
+was made in later days by Sir Isaac Newton.
+
+In a refractor the rays of light, from a star or any other bright
+body, reach first a large object-glass, through which they pass, and
+by which, as they pass, they are caused to converge, narrowing to a
+focus or point. From this point they widen slightly on their way to the
+eye-piece. After passing through the eye-piece, by which they are once
+more straightened into parallel rays, they arrive at the eye.
+
+Speaking broadly, the eye receives--actually sees--nearly as much of
+the starlight as if its pupil were the full size of the object-glass
+of that telescope, and the power of such an instrument depends upon
+the size of the object-glass. A refractor has been made with an
+object-glass forty inches across, and this, for the observer, means
+looking at a star with an eye pupil more than three feet in diameter.
+This refractor is now in the Yerkes Observatory at Williams Bay, Lake
+Geneva, Wisconsin.
+
+There are several forms of reflectors. With one form, when it is
+pointed at a star, the rays of starlight fall direct through the
+telescope-tube upon a highly-polished mirror, so shaped that rays of
+light reflected thence are caused to fall converging upon a small
+plane-mirror in the center of the tube, from which they are thrown,
+parallel to the side of the tube, to the eye-piece, which converges
+them to the eye.
+
+The mirror of a reflector can be made very much larger than the
+object-glass of a refractor. The famous Lord Rosse telescope, which
+has a tube sixty feet long, contains a mirror no less than six feet in
+diameter. This, to an observer, is tantamount to looking at the stars
+with an eye so huge that its pupil alone would be nearly equal in size
+to the six-foot wheel of a steam-engine. It will readily be perceived
+how much more starlight can be grasped by such a fishing-net than by
+the tiny pupil of your eye or mine.
+
+A main difference between the two kinds of telescope thus resides in
+the fact that the star-rays--or any other kind of light-rays--when
+first captured, pass, in one case, _through_ the glass on which they
+fall, and, in the other case, are thrown off _from_ the mirror. In both
+cases, the whole amount of light so captured is gathered into a small
+compass, so as to be available for human sight.
+
+[Illustration: EYE-PIECE OF THE LICK TELESCOPE.]
+
+Once more, let me remind you, it should be always kept clearly in
+mind that every object that is seen by us--from a mote of dust to a
+sun, from a coal-scuttle to a star--is perceived purely and solely by
+the light which it gives out, either intrinsic or reflected light.
+Countless myriads of rays pass from the surface of the thing seen to
+our eyes, picturing there, on the sensitive retina, a fleeting vision
+of its form.
+
+All the leading Governments in Europe have observatories for the study
+of the heavens, which are furnished with the best instruments of modern
+construction. The principal observatories are those at Paris, Berlin,
+Vienna, Nice; Dorpat, the seat of a celebrated university founded by
+Gustavus Adolphus, of Sweden, in 1630; Pulkowa, near St. Petersburg;
+Lisbon, and at Greenwich in England. In America, though only in recent
+years has astronomy been cultivated with ardor, there are observatories
+of more or less importance,--the National Observatory at Washington,
+D. C.; the Cincinnati Observatory, projected by the late General O. M.
+Mitchel; the Dudley Observatory, founded by Mrs. Blandina Dudley in
+honor of her husband, at Albany, N. Y.; the Lick Observatory, founded
+by James Lick, on Mount Hamilton, Cal.; and the Yerkes Observatory,
+connected with the Chicago University, founded by Charles T. Yerkes.
+Besides these, there are observatories connected with some of our other
+leading universities and colleges, as those of Harvard, at Cambridge,
+Mass.; Yale University; Williams College; West Point Military Academy;
+Amherst College; Princeton; Dartmouth; Michigan University; Hamilton
+College, N. Y., and several others.
+
+[Illustration: LICK OBSERVATORY IN WINTER, FROM THE EAST.]
+
+The largest and best refracting telescopes in the world are those
+at Lick Observatory and at Yerkes Observatory, now in charge
+of Professor E. E. Barnard, who, while at the head of the Lick
+Observatory, discovered the fifth satellite of Jupiter, and determined
+the character of the inner ring of Saturn. The best reflecting
+telescope is that of Lord Rosse, at Birr Castle, in Kings County,
+Ireland.
+
+[Illustration: E. E. BARNARD.]
+
+In reviewing the path which we have traversed in this volume, though we
+have penetrated the sidereal depths and wandered at will through space,
+we feel that we have not yet reached the outskirts of creation. We
+have never left the center. Beyond us still lies the circumference. We
+see opened before us the infinite, of which the study is not yet begun!
+We have seen nothing; we recoil in terror; we fall back astounded.
+Indeed, we might fall into the yawning abyss--fall forever, during a
+whole eternity; never, never should we reach the bottom, any more than
+we have attained the summit. There is no east nor west, neither right
+nor left. There is no up nor down; there is neither a zenith nor a
+nadir. In whatever way we look, it is infinite in all directions.
+
+In this infinitude of space, the associations of suns and of worlds
+which constitute our visible universe form but an island, a vast
+archipelago; and in the eternity of duration, the life of our proud
+humanity, with all its concerns, its aspirations, and its achievements,
+the whole life of our entire planet, is but the shadow of a dream! Well
+might the Hebrew poet, as he looked forth upon nature, exclaim in his
+amazement: “When I consider thy heavens, the work of thy fingers, the
+moon and the stars which thou hast ordained, what is man that thou art
+mindful of him, and the son of man that thou visitest him?”
+
+The constellations, the charts of the sky; the catalogues of curious
+stars--variable, double or multiple, and colored; the description of
+instruments accessible to the observer of the heavens, and useful
+tables to consult, are only touched upon in this volume. The reader
+whose scientific desires are satisfied by the elements of astronomy,
+may stop here. Few have time to pursue the subject further; but it is
+sweet to live in the sphere of the mind; it is sweet to contemn the
+rough noises of a vulgar world; it is sweet to soar in the ethereal
+heights, and to devote the best moments of our life to the study of the
+true, the infinite, and the eternal!
+
+
+
+
+PUBLISHERS’ NOTE.
+
+
+We have now reached the conclusion of “The Story of the Sun, Moon,
+and Stars.” Miss Giberne’s work has been supplemented with a large
+amount of matter from other sources. The value of the book has thus
+been increased without diminishing its popular character. In most
+admirable form it tells the story of the heavenly world, which is the
+work of God’s hands, the moon and the stars which he has made. The
+reverent reader, to whom the Word of God is “sweeter than honey and
+the honey-comb,” may here find that “the heavens declare the glory of
+God, and the firmament showeth his handiwork.” We confidently present
+it to the reader as the best and completest work in print on the great
+subject of which it treats.
+
+
+
+
+INDEX
+
+
+  Adams, John Couch, 231, 236
+
+  Aërolites, 84
+    Size of, 86
+
+  Aldebaran, Movement of, 277
+
+  Alexander at Arbela, 146
+
+  Alpha Centauri, Distance of, 99
+    Duration of light journey, 102
+    Position, 279
+
+  Alps, Lunar Mountains, 179
+
+  Altai, Lunar Mountains, 179
+
+  Andromeda, Constellation of, 112
+
+  Apennines, Lunar Mountains, 179
+
+  Arago, 235, 402
+
+  Arcturus, Motion of, 114
+    Position, 276
+
+  Aristotle, 376
+
+  Asteroids, 53
+
+  Astronomy, The dawn of, 363
+
+  Attraction, 34
+
+  Aurora Borealis, where seen, 141
+
+  Axis of earth slanting, 44
+
+
+  Barnard, E. E., 53, 410
+
+  Bessel, F. W., 284
+    Discovery of star parallax, 324
+    Discovers star parallax, 405
+
+  Bolides, 87, 257
+
+  Borelli, 388
+
+
+  Capella, Duration of light journey, 103
+    Velocity of motion, 114
+
+  Caucasian Range, Lunar Mountains, 179
+
+  Carpathian, Lunar Mountains, 179
+
+  Carrington, 141
+
+  Cassini, Measurement of sun’s distance, 310
+
+  Cassiopeia, Constellation of, 112
+
+  Ceres, size of, 53
+
+  Chaldean star-gazers, 365
+
+  Chinese records of eclipses, 365
+
+  Cicero, 177
+
+  Clark, Alvan Graham, 289
+
+  Cloven-disk theory, 331
+
+  Coal sack, 329
+
+  Columbus in Jamaica, 146
+
+  Comet, Biela’s, 90, 93
+    Halley’s, 78, 248
+    Of 1843, 80
+    Newton’s, 78
+    With two tails, 77
+    Encke’s, 78
+    Heat endured by, 81
+    Length of tail, 81
+    Collision with, 82
+    Split in two, 91
+
+  Comets, 73, 240, 246
+    Number of, 75
+    Nature of, 74
+    Captured by Jupiter, 213
+    Composition of, 256
+    Composition of tails, 253
+    Orbits of, 129
+    With closed orbits, 76
+
+  Confucius as an astronomer, 365
+
+  Constellations, Grouping, 366
+    When named, 366
+
+  Copernicus, Author of “Celestial Spheres,” 177, 183, 370, 371, 375
+    Star parallax, 319
+
+  Copernican system of the universe, 175
+
+  Corona, Description of, 153
+
+
+  D’Alembert, 399
+
+  Dante, 121
+
+  Demos, Satellite of Mars, 191
+
+  Donati’s Comet, 248, 250
+
+  Draco, Constellation of, 112
+
+
+  Earth, Globular, 17
+    How formed, 21
+    Member of the Solar System, 14
+    In motion, 16
+    Motions, 18, 41, 126
+    One of a family, 14
+    Size of, 26
+    What is it? 13
+
+  Ecliptic, 43
+
+  Eclipses omens of evil, 145
+
+  Egyptian astronomers, 365
+
+  Encke, 238
+
+  Epicycles, 373
+
+  Equinox, 44
+
+
+  Fire-balls, Speed of, 88
+
+  Fabricius discovers sun-spots, 27
+
+  Fraunhofer, Joseph von, 345
+
+
+  Galle, 232, 238
+
+  Galileo, 28, 276, 371, 376, 378, 380
+
+  Gassendi, 184
+
+  George III, 226
+
+  Gilbert, 388
+
+  Great Bear, Constellation of, 108, 340
+
+
+  Halley, 388
+    Transit of Venus, 314
+    Star motions, 318
+
+  Hercules, Constellation of, 112
+
+  Herschel, Caroline, 226, 393
+
+  Herschel, Sir John, 81, 233, 303, 398
+
+  Herschel, William, 96, 119, 225, 271, 393
+
+  Hipparchus, 368, 371
+
+  Hodgson, 141
+
+  Holland, Sir Henry, 237
+
+  Hook, Robert, 388
+
+  Horrocks, 388
+
+  Huggins, Dr., 359
+
+  Humboldt, Alexander von, 265
+
+
+  Jupiter, 55
+    Comparative size, 56
+    Distance of, 122
+    His satellites, 56, 206, 210
+    Velocity, 199
+    Wind storms, 204
+
+
+  Kepler, 75, 296
+    Laws of, 371, 374, 380, 388
+
+  Kew Observatory, 141
+
+
+  Lacaille, Catalogue of, 105
+
+  Lalande, Catalogue of, 105
+
+  Laplace, 385, 398
+
+  Later astronomy, 393
+
+  Leverrier, Urbain J. J., 231, 401
+    Discovers Neptune, 321
+
+  Light, Rapidity of, 101
+    Time, Duration of, 331
+
+  Lowe at Santander, 147
+
+  Lunar craters, Antiquity of, 172
+    How formed, 173
+    Plato and Copernicus, 173
+    Ptolemy, 174
+    Schickard, 174
+    Tycho, 174
+
+  Lunar Mountains, How formed, 174
+
+  Lyra, Constellation, 297
+
+
+  Magellanic clouds, 309
+
+  Magnetism, 140, 141
+
+  Mars, 52, 373, 374
+    Moons of, 191
+    Continents of, 197
+    Distance from earth, 197
+
+  Maury, Lieutenant, 80
+
+  Mercury, Atmosphere, 181
+    Distance from sun, 49
+    Length of year, 180
+    Is it inhabited? 181
+    Orbit of, 180
+    Phases, 50
+    Size of, 49
+    Transit of, 184
+
+  Meteor, 84, 257
+
+  Meteorites, 240, 257
+    Around the sun, 94
+    August system, 90, 242
+    In Saturn’s rings, 94
+    November system, 90, 94, 241
+    Number of, 86
+    Protection from, 86
+    Shower of 1872, 92
+    Shower of 1885, 93
+
+  Milky Way, 270, 329
+
+  Mizar, 342
+
+  Modern Astronomy, 375
+
+  Moon, 62
+    Appearance at its full, 63
+    Atmosphere, 157, 169
+    Phases of, 160
+    Condition of, 65
+    Craters,  68, 170
+    Earth’s satellite, 164
+    Earth-shine, 160
+    Eclipse, 163
+    Influence on tides, 167
+    Landscape of, 68
+    Mountains, 67
+    Orbit of, 166
+    Temperature on, 72
+    Revolution, 64
+    Size of, 64
+    Surface, 67
+
+
+  Nasmyth,              173
+
+  Nebulæ, Number of,   336
+
+  Neptune, 59
+    Discovery of, 232, 234
+    Distance of, 123
+    Length of year,  59
+
+  Newton analyzes light, 385
+    Birth and childhood, 382
+
+  Nicetos of Syracuse,  177
+
+  Nicias, Athenian General, 146
+
+  Nicolas, Cardinal, 177
+
+
+  Observatories, 408
+
+  Orbits, Planetary, 47
+
+  Orion, Constellation of, 112
+
+
+  Parallax, 311
+
+  Phobos, Satellite of Mars, 191
+
+  Photography, Stellar, 355
+
+  Pius IX,  93
+
+  Pisa, Leaning Tower of, 378
+
+  Plane of the Ecliptic, 201
+
+  Planets, Distance from the sun, 123
+    First group,  48
+    How formed, 22
+    Length of years, 49
+    Orbits, 47
+    Order of formation, 23
+    Second group, 48,55
+
+  Plutarch, 177
+
+  Pole star, Duration of light journey, 103
+    Position, 108
+    Rate of motion, 115
+
+  Prism, 344
+
+  Pritchard, C., 356
+
+  Ptolemaic system of the universe, 175, 369
+
+  Ptolemy, 371, 369
+
+  Pythagoras, Grecian astronomer, 367
+
+
+  Rosse, Lord, Telescope, 406
+
+  Rowton siderite, 258
+
+
+  Saturn, 57
+    Composition of rings, 221
+    Distance of, 122
+    Distance from sun, 214
+    Length of year, 57
+    Moons, 217
+    Rings, 219
+    Satellites, 58
+    Size, 214
+    Weight, 214
+
+  Shickard, Crater on the moon, 174
+
+  Scheiner, 28
+
+  Secchi, 92
+
+  Shooting stars, 84
+
+  Sirius, Brightness of, 275, 285
+    Changing color, 285
+    Distance of, 100
+    Duration of light journey, 103
+    Movement of, 277
+
+  Solar cloud, 148
+
+  Solar System, 60, 122
+    Model of, 60
+
+  Spectroscope, 143, 345
+
+  Spectroscopic photography, 360
+
+  Spectrum analysis, 346, 354
+
+  Star clusters, 304, 336
+    Parallax, 284, 316
+    Spectroscopy, 356
+
+  Stars, Apparent motion, 107
+    Attraction, 21
+    Distance of, 99, 310, 320
+    Distance, 281, 282
+    Fixed, Why so called, 20
+    Fixed, Why, 366
+    Golden, 274
+    Magnitude of, 97
+    How many visible, 95
+    Measurement, 278
+    Red, 274
+    Variable, 274, 291
+    White, 274
+
+  Sun, 24
+    Attraction of, 156
+    Attraction of gravitation, 34
+    Chromatosphere, 32
+    Cyclones of 30, 136
+    Density, 26
+    Destination, 119
+    Distance of, 25
+    Eclipse of, 143
+    Flames, Their height, 31, 151
+    Flames, Their velocity, 138
+    Forces and influences, 39
+    Head of our family, 24
+    Magnetic power of, 139
+    Its mottled appearance, 142
+    Rate of motion, 119
+    Penumbra, 133
+    Photosphere, 31, 134
+    Power of, 39, 137
+    Rapidity of motion, 26
+    Revolution on axis, 28
+    Size, 26, 154
+    Solar prominence, 32
+    Spots, 27, 30, 133
+    Symbol of purity, 380
+    Umbra, 133
+    Weight, 27, 154
+
+  Swift, Voyage to Laputa, 194
+
+
+  Telescopes, 378, 379, 405
+    Refractors and reflectors, 405, 408, 410
+
+  Tides, 168
+
+  Thales, founder of Grecian Astronomy, 367
+
+  Toucan, 306
+
+  Tycho Brahe, 175, 371, 372, 373
+
+
+  Universe, Definition of, 19
+
+  Uranus, 58
+    Discovery of, 225
+    Distance of, 123
+
+
+  Venus, Orbit of 51
+    Is it inhabited? 189
+    Distance from earth, 186
+    Phases of, 51, 379
+    Transits of, 185
+
+  Vesta, Size of, 53
+
+  Voltaire, Prophecy of, 193
+
+
+  Wilson, 30
+
+  Wollaston, Dr. W. H., 345
+
+  Wren, 388
+
+
+  Yerkes Observatory, 406
+
+  Young, Chas. A., 142, 148
+
+
+  Zodiacal Light, 94, 224, 265
+
+
+
+
+  Transcriber's Notes:
+
+  In the original a link to Sir Isaac Newton was omitted from the
+  List of Illustrations. The transcriber has inserted one.
+
+  Italics are shown thus: _sloping_.
+
+  Variations in spelling and hyphenation are retained.
+
+  Perceived typographical errors have been changed.
+
+
+
+*** END OF THE PROJECT GUTENBERG EBOOK 77004 ***
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+<body>
+<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 77004 ***</div>
+
+<div class="figcenter">
+<img src="images/cover.jpg" alt="cover">
+</div>
+
+<div class="figcenter1" id="f1">
+<img src="images/fig1.jpg" alt="hipparchus">
+<p class="caption"><span class="smcap">Hipparchus in the Observatory of Alexandria.</span></p>
+</div>
+
+<h1>
+<span class="up">THE STORY</span><br>
+
+<br>
+
+<span class="mid">OF THE</span><br>
+
+<br>
+
+<span class="xxlarge">SUN, MOON, AND STARS</span></h1>
+
+<p class="c">BY</p>
+
+<p class="c p2 xlarge">AGNES GIBERNE</p>
+
+<p class="c"><span class="smcap">Author of “The Starry Skies,” “The World’s Foundations,”<br>
+“Radiant Suns,” Etc.</span></p>
+
+<div class="figcenter1">
+<img src="images/fig2.jpg" alt="decoration">
+</div>
+
+
+<p class="c p2 x2large sp">WITH COPIOUS ADDITIONS</p>
+
+<hr class="r5t">
+
+<hr class="r5">
+
+
+<p class="c oldeng large">Fully Illustrated</p>
+
+<hr class="r5">
+
+<hr class="r5">
+
+<p class="c p4">CINCINNATI</p>
+
+<p class="c sp large">NATIONAL BOOK COMPANY
+</p>
+<hr class="full x-ebookmaker-drop">
+
+
+<div class="chapter">
+<p class="c more">
+COPYRIGHT, 1898,</p>
+
+<p class="c more">
+<span class="smcap">By</span> J. T. JONES.
+</p>
+</div>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_5">[Pg 5]</span></p>
+
+<p class="ph2">INTRODUCTION.</p>
+</div>
+
+<div class="figcenter">
+<img src="images/fig3.jpg" alt="decoration">
+</div>
+
+<p class="c large"><span class="smcap">By Charles Pritchard</span>, M. A., F. R. S.,</p>
+
+<p class="c"><span class="smcap">Professor of Astronomy in the University of Oxford</span>.</p>
+
+<hr class="r65">
+
+<p><span class="smcap large">The</span> pages of this volume on a great subject were
+submitted to my criticism while passing through the
+press, with a request from a friend that I would make
+any suggestions which might occur to me for its improvement.
+Naturally, such a request was entertained,
+in the first instance, with hesitation and misgiving.
+But after a rapid perusal of the first sheet, I found my
+interest awakened, and then gradually secured; for the
+book seemed to me to possess certain features of no
+ordinary character, and, in my judgment, held out the
+promise of supplying an undoubted want, thus enabling
+me to answer a question which I have been
+often asked, and which had as often puzzled me, to
+the effect, “Can you tell me of any book on astronomy
+suited to beginners?” I think just such a book
+is here presented to the reader; for the tale of the
+stellar universe is therein told with great simplicity,
+and perhaps with sufficient completeness, in an earnest
+and pleasant style, equally free, I think, from inaccuracy<span class="pagenum" id="Page_6">[Pg 6]</span>
+or unpardonable exaggeration. We have
+here the outlines of elementary astronomy, not merely
+detailed without mathematics, but to a very great extent
+expressed in untechnical language. Success in
+such an attempt I regard as a considerable feat, and
+one of much practical utility.</p>
+
+<p>For the science of astronomy is essentially a science
+of great magnitude and great difficulty. From the
+time of Hipparchus, some century and a half before
+the Christian era, down to the present day, the cultivation
+of astronomy has severely taxed the minds of a
+succession of men endowed with the rarest genius.
+The facts and the truths of the science thus secured
+have been of very slow accretion; but like all other
+truths, when once secured and thoroughly understood,
+they are found to admit of very simple verbal expression,
+and to lie well within the general comprehension,
+and, I may safely add, within the sympathies of all
+educated men and women.</p>
+
+<p>Thus the great astronomers, the original discoverers
+of the last twenty centuries, have labored, each in
+his separate field of the vast universe of nature, and
+other men, endowed with other gifts, have entered on
+their labors, and by systematizing, correlating, and
+simplifying the expression of their results, have
+brought the whole within the grasp of cultivated
+men engaged in other branches of the varied pursuits
+of our complicated life. It is in this sort of order<span class="pagenum" id="Page_7">[Pg 7]</span>
+that the amelioration and civilization of mankind
+have proceeded, and at the present moment are, I
+hope and believe, rapidly proceeding.</p>
+
+<p>It was, I suspect, under this point of view, though
+half unconsciously so, that my attention was arrested
+by the book now presented to the reader; for we
+have here many of the chief results of the laborious
+researches of such men as Ptolemy, Kepler, Newton,
+Herschel, Fraunhofer, Janssen, Lockyer, Schiaparelli,
+and others—no matter where accumulated or by
+whom recorded—filtered through the mind of a
+thoughtful and cultured lady, and here presented to
+other minds in the very forms wherein they have been
+assimilated and pictured in her own. And these forms
+and pictures are true. It is in this way that the intellectual
+“protoplasm” of the human mind is fostered
+and practically disseminated.</p>
+
+<p>And, then, there is still another point of view from
+which this general dissemination of great truths in a
+simple style assumes an aspect of practical importance.
+I allude to the influences of this process on
+the imaginative or poetic side of our complex nature.</p>
+
+<p>Wordsworth, in one of his prefaces, has stated so
+clearly the truth on this subject that I can not do better
+than give his words. “If the time should ever
+come,” he says, “when what is now science becomes
+familiarized to men, then the remotest discoveries of
+the chemist, the botanist, the mineralogist, will be as<span class="pagenum" id="Page_8">[Pg 8]</span>
+proper objects of the poet’s art as any upon which it
+can be employed. He will be ready to follow the
+steps of the man of science; he will be at his side,
+carrying sensation into the midst of the objects of
+science itself. The poet will lend his divine spirit to
+aid the transfiguration, and will welcome the being
+thus produced as a dear and genuine inmate of the
+household of man.”</p>
+
+<p>It is for reasons such as here stated that I heartily
+commend this book to the attention of those who
+take an interest in the advancement of the intellectual
+progress and culture of society. The story of
+the Kosmos is told by the authoress in her own language
+and after her own method. I believe, as I have
+said, the story is correct.</p>
+
+<p class="pad"><span class="smcap">Oxford University.</span></p>
+
+
+<hr class="full x-ebookmaker-drop">
+
+<p><span class="pagenum" id="Page_9">[Pg 9]</span></p>
+
+<div class="chapter">
+<p class="ph22">CONTENTS.</p>
+</div>
+
+<div class="figcenter">
+<img src="images/fig3.jpg" alt="decoration">
+</div>
+
+<table>
+
+<tr>
+  <td class="tdr"><span class="smcap more">Chapter.</span></td>
+  <td class="tdl"></td>
+  <td class="tdr"><span class="smcap more">Page.</span></td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c1">I.</a></td>
+  <td class="tdl"><span class="smcap">The Earth One of a Family</span>,</td>
+  <td class="tdr">13</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c2">II.</a></td>
+  <td class="tdl"><span class="smcap">The Head of Our Family</span>,</td>
+  <td class="tdr">24</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c3">III.</a></td>
+  <td class="tdl"><span class="smcap">What Binds the Family Together</span>,</td>
+  <td class="tdr">34</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c4">IV.</a></td>
+  <td class="tdl"><span class="smcap">The Leading Members of Our Family.—First
+Group</span>,</td>
+  <td class="tdr">46</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c5">V.</a></td>
+  <td class="tdl"><span class="smcap">The Leading Members of Our Family.—Second
+Group</span>,</td>
+  <td class="tdr">55</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c6">VI.</a></td>
+  <td class="tdl"><span class="smcap">The Moon</span>,</td>
+  <td class="tdr">62</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c7">VII.</a></td>
+  <td class="tdl"><span class="smcap">Visitors</span>,</td>
+  <td class="tdr">73</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c8">VIII.</a></td>
+  <td class="tdl"><span class="smcap">Little Servants</span>,</td>
+  <td class="tdr">83</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c9">IX.</a></td>
+  <td class="tdl"><span class="smcap">Neighboring Families</span>,</td>
+  <td class="tdr">95</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c10">X.</a></td>
+  <td class="tdl"><span class="smcap">Our Neighbors’ Movements</span>,</td>
+  <td class="tdr">106</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c11">XI.</a></td>
+  <td class="tdl"><span class="smcap">More About the Solar System</span>,</td>
+  <td class="tdr">122</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c12">XII.</a></td>
+  <td class="tdl"><span class="smcap">More About the Sun</span>,</td>
+  <td class="tdr">133</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c13">XIII.</a></td>
+  <td class="tdl"><span class="smcap">Yet More About the Sun</span>,</td>
+  <td class="tdr">148</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c14">XIV.</a></td>
+  <td class="tdl"><span class="smcap">More About the Moon</span>,</td>
+  <td class="tdr">157</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c15">XV.</a></td>
+  <td class="tdl"><span class="smcap">Yet More About the Moon</span>,</td>
+  <td class="tdr">164</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c16">XVI.</a></td>
+  <td class="tdl"><span class="smcap">Mercury, Venus, and Mars</span>,</td>
+  <td class="tdr">180</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c17">XVII.</a></td>
+  <td class="tdl"><span class="smcap">Jupiter</span>,</td>
+  <td class="tdr">199</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c18">XVIII.</a></td>
+  <td class="tdl"><span class="smcap">Saturn</span>,</td>
+  <td class="tdr">214</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c19">XIX.</a></td>
+  <td class="tdl"><span class="smcap">Uranus and Neptune</span>,</td>
+  <td class="tdr">225</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c20">XX.</a></td>
+  <td class="tdl"><span class="smcap">Comets and Meteorites</span>,</td>
+  <td class="tdr">240</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c21">XXI.</a></td>
+  <td class="tdl"><span class="smcap">More About Comets and Meteorites</span>,</td>
+  <td class="tdr">246</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c22">XXII.</a></td>
+  <td class="tdl"><span class="smcap">Many Suns</span>,</td>
+  <td class="tdr">267</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c23">XXIII.</a></td>
+  <td class="tdl"><span class="smcap">Some Particular Suns</span>,<span class="pagenum" id="Page_10">[Pg 10]</span></td>
+  <td class="tdr">278</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c24">XXIV.</a></td>
+  <td class="tdl"><span class="smcap">Different Kinds of Suns</span>,</td>
+  <td class="tdr">291</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c25">XXV.</a></td>
+  <td class="tdl"><span class="smcap">Groups and Clusters of Suns</span>,</td>
+  <td class="tdr">304</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c26">XXVI.</a></td>
+  <td class="tdl"><span class="smcap">The Problem of Sun and Star Distances</span>,</td>
+  <td class="tdr">310</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c27">XXVII.</a></td>
+  <td class="tdl"><span class="smcap">Measurement of Star Distances</span>,</td>
+  <td class="tdr">320</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c28">XXVIII.</a></td>
+  <td class="tdl"><span class="smcap">The Milky Way</span>,</td>
+  <td class="tdr">329</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c29">XXIX.</a></td>
+  <td class="tdl"><span class="smcap">A Whirling Universe</span>,</td>
+  <td class="tdr">337</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c30">XXX.</a></td>
+  <td class="tdl"><span class="smcap">Reading the Light</span>,</td>
+  <td class="tdr">344</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c31">XXXI.</a></td>
+  <td class="tdl"><span class="smcap">Stellar Photography</span>,</td>
+  <td class="tdr">355</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c32">XXXII.</a></td>
+  <td class="tdl"><span class="smcap">The Dawn of Astronomy</span>,</td>
+  <td class="tdr">363</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c33">XXXIII.</a></td>
+  <td class="tdl"><span class="smcap">Modern Astronomy</span>,</td>
+  <td class="tdr">375</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c34">XXXIV.</a></td>
+  <td class="tdl"><span class="smcap">Sir Isaac Newton</span>,</td>
+  <td class="tdr">382</td></tr>
+
+<tr>
+  <td class="tdr"><a href="#c35">XXXV.</a></td>
+  <td class="tdl"><span class="smcap">Later Astronomy</span>,</td>
+  <td class="tdr">393</td></tr>
+
+</table>
+
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_11">[Pg 11]</span></p>
+
+<p class="ph22">LIST OF ILLUSTRATIONS.</p>
+</div>
+
+<div class="figcenter">
+<img src="images/fig3.jpg" alt="decoration">
+</div>
+
+<table>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdr"><span class="smcap more">Page.</span></td></tr>
+
+<tr>
+  <td class="tdl">Hipparchus in the Observatory at Alexandria</td>
+  <td class="tdr"><a href="#f1"><i>Frontispiece.</i></a></td></tr>
+
+<tr>
+  <td class="tdl">The Solar System</td>
+  <td class="tdr"><a href="#f4">15</a></td></tr>
+
+<tr>
+  <td class="tdl">The Pleiades</td>
+  <td class="tdr"><a href="#f5">19</a></td></tr>
+
+<tr>
+  <td class="tdl">Sun-spots</td>
+  <td class="tdr"><a href="#f6">29</a></td></tr>
+
+<tr>
+  <td class="tdl">Phases of Mercury before Inferior Conjunction—Evening Star</td>
+  <td class="tdr"><a href="#f7">50</a></td></tr>
+
+<tr>
+  <td class="tdl">Appearance of the Full Moon</td>
+  <td class="tdr"><a href="#f8">63</a></td></tr>
+
+<tr>
+  <td class="tdl">One Form of Lunar Crater</td>
+  <td class="tdr"><a href="#f9">69</a></td></tr>
+
+<tr>
+  <td class="tdl">The Earth as Seen from the Moon</td>
+  <td class="tdr"><a href="#f10">71</a></td></tr>
+
+<tr>
+  <td class="tdl">Passage of the Earth and the Moon through the Tail of a Comet</td>
+  <td class="tdr"><a href="#f11">76</a></td></tr>
+
+<tr>
+  <td class="tdl">Passage of the Comet of 1843 Close to the Sun</td>
+  <td class="tdr"><a href="#f12">79</a></td></tr>
+
+<tr>
+  <td class="tdl">Meteor Emerging from Behind a Cloud</td>
+  <td class="tdr"><a href="#f13">84</a></td></tr>
+
+<tr>
+  <td class="tdl">The Great Shower of Shooting-stars, November 27, 1872</td>
+  <td class="tdr"><a href="#f14">90</a></td></tr>
+
+<tr>
+  <td class="tdl">Constellation of the Great Bear</td>
+  <td class="tdr"><a href="#f15">108</a></td></tr>
+
+<tr>
+  <td class="tdl">The Great Bear 50,000 Years Ago</td>
+  <td class="tdr"><a href="#f16">109</a></td></tr>
+
+<tr>
+  <td class="tdl">The Great Bear 50,000 Years Hence</td>
+  <td class="tdr"><a href="#f17">109</a></td></tr>
+
+<tr>
+  <td class="tdl">Constellation of Orion as it Appears Now</td>
+  <td class="tdr"><a href="#f18">110</a></td></tr>
+
+<tr>
+  <td class="tdl">Constellation of Orion 50,000 Years Hence</td>
+  <td class="tdr"><a href="#f19">111</a></td></tr>
+
+<tr>
+  <td class="tdl">Position of Planets Inferior to Jupiter—Showing the Zone of the
+Asteroids</td>
+  <td class="tdr"><a href="#f20">123</a></td></tr>
+
+<tr>
+  <td class="tdl">Comparative Size of the Planetary Worlds</td>
+  <td class="tdr"><a href="#f21">130</a></td></tr>
+
+<tr>
+  <td class="tdl">A Typical Sun-spot</td>
+  <td class="tdr"><a href="#f22">135</a></td></tr>
+
+<tr>
+  <td class="tdl">A Solar Eruption</td>
+  <td class="tdr"><a href="#f23">138</a></td></tr>
+
+<tr>
+  <td class="tdl">Sun-flames, May 3, 1892</td>
+  <td class="tdr"><a href="#f24">143</a></td></tr>
+
+<tr>
+  <td class="tdl">Solar Corona and Prominence</td>
+  <td class="tdr"><a href="#f25">152</a></td></tr>
+
+<tr>
+  <td class="tdl">Comparative Size of the Earth and Sun</td>
+  <td class="tdr"><a href="#f26">155</a></td></tr>
+
+<tr>
+  <td class="tdl">The Moon—an Expired Planet</td>
+  <td class="tdr"><a href="#f27">159</a></td></tr>
+
+<tr>
+  <td class="tdl">The Lunar Crater Copernicus</td>
+  <td class="tdr"><a href="#f28">170</a></td></tr>
+
+<tr>
+  <td class="tdl">Lunar Eruption—Brisk Action</td>
+  <td class="tdr"><a href="#f29">172</a></td></tr>
+
+<tr>
+  <td class="tdl">Lunar Eruption—Feeble Action</td>
+  <td class="tdr"><a href="#f30">173</a></td></tr>
+
+<tr>
+  <td class="tdl">Nicolaus Copernicus</td>
+  <td class="tdr"><a href="#f31">176</a></td></tr>
+
+<tr>
+  <td class="tdl">Phases of Venus</td>
+  <td class="tdr"><a href="#f32">186</a><span class="pagenum" id="Page_12">[Pg 12]</span></td></tr>
+
+<tr>
+  <td class="tdl">Mars and the Path of its Satellites</td>
+  <td class="tdr"><a href="#f33">191</a></td></tr>
+
+<tr>
+  <td class="tdl">General Aspect of Jupiter—Satellite and its Shadow</td>
+  <td class="tdr"><a href="#f34">200</a></td></tr>
+
+<tr>
+  <td class="tdl">Satellites of Jupiter Compared with the Earth and Moon</td>
+  <td class="tdr"><a href="#f35">206</a></td></tr>
+
+<tr>
+  <td class="tdl">The System of Jupiter</td>
+  <td class="tdr"><a href="#f36">208</a></td></tr>
+
+<tr>
+  <td class="tdl">Orbits of Nine Comets Captured by Jupiter</td>
+  <td class="tdr"><a href="#f37">213</a></td></tr>
+
+<tr>
+  <td class="tdl">Saturn and the Earth—Comparative Size</td>
+  <td class="tdr"><a href="#f38">215</a></td></tr>
+
+<tr>
+  <td class="tdl">Ideal View of Saturn’s Rings and Satellites from the Planet</td>
+  <td class="tdr"><a href="#f39">222</a></td></tr>
+
+<tr>
+  <td class="tdl">Great Astronomers of Earlier Times</td>
+  <td class="tdr"><a href="#f40">227</a></td></tr>
+
+<tr>
+  <td class="tdl">The Great Comet of 1811</td>
+  <td class="tdr"><a href="#f41">247</a></td></tr>
+
+<tr>
+  <td class="tdl">Donati’s Comet, 1858</td>
+  <td class="tdr"><a href="#f42">249</a></td></tr>
+
+<tr>
+  <td class="tdl">Great Comet of 1744</td>
+  <td class="tdr"><a href="#f43">254</a></td></tr>
+
+<tr>
+  <td class="tdl">The First Comet of 1888—June 4</td>
+  <td class="tdr"><a href="#f44">255</a></td></tr>
+
+<tr>
+  <td class="tdl">Great Comet of 1680</td>
+  <td class="tdr"><a href="#f45">260</a></td></tr>
+
+<tr>
+  <td class="tdl">Great Comet of 1769</td>
+  <td class="tdr"><a href="#f46">261</a></td></tr>
+
+<tr>
+  <td class="tdl">Baron Alexander Von Humboldt</td>
+  <td class="tdr"><a href="#f47">264</a></td></tr>
+
+<tr>
+  <td class="tdl">A Telescopic Field in the Milky Way</td>
+  <td class="tdr"><a href="#f48">270</a></td></tr>
+
+<tr>
+  <td class="tdl">Cygnus, Constellation of</td>
+  <td class="tdr"><a href="#f49">279</a></td></tr>
+
+<tr>
+  <td class="tdl">Stars whose Distances are Best Known</td>
+  <td class="tdr"><a href="#f50">281</a></td></tr>
+
+<tr>
+  <td class="tdl">Lyra, Constellation of</td>
+  <td class="tdr"><a href="#f51">297</a></td></tr>
+
+<tr>
+  <td class="tdl">Constellations in the Northern Hemisphere</td>
+  <td class="tdr"><a href="#f52">300</a></td></tr>
+
+<tr>
+  <td class="tdl">A Cluster of Stars in Centaurus</td>
+  <td class="tdr"><a href="#f53">305</a></td></tr>
+
+<tr>
+  <td class="tdl">The Great Nebula in Andromeda, Compared with Size of the Solar
+System</td>
+  <td class="tdr"><a href="#f54">307</a></td></tr>
+
+<tr>
+  <td class="tdl">A Cluster of Stars in Perseus</td>
+  <td class="tdr"><a href="#f55">332</a></td></tr>
+
+<tr>
+  <td class="tdl">Hercules, Constellation of</td>
+  <td class="tdr"><a href="#f56">338</a></td></tr>
+
+<tr>
+  <td class="tdl">The Great Bear, Constellation of</td>
+  <td class="tdr"><a href="#f57">341</a></td></tr>
+
+<tr>
+  <td class="tdl">The Prism and Spectrum</td>
+  <td class="tdr"><a href="#f58">344</a></td></tr>
+
+<tr>
+  <td class="tdl">The Spectroscope</td>
+  <td class="tdr"><a href="#f59">345</a></td></tr>
+
+<tr>
+  <td class="tdl">Spectra, Showing the Dark Lines</td>
+  <td class="tdr"><a href="#f60">347</a></td></tr>
+
+<tr>
+  <td class="tdl">Great Astronomers of Later Times</td>
+  <td class="tdr"><a href="#f61">377</a></td></tr>
+
+<tr>
+  <td class="tdl">Sir Isaac Newton</td>
+  <td class="tdr"><a href="#f62">386</a></td></tr>
+
+<tr>
+  <td class="tdl">Eye-piece of Lick Telescope</td>
+  <td class="tdr"><a href="#f63">407</a></td></tr>
+
+<tr>
+  <td class="tdl">Lick Observatory</td>
+  <td class="tdr"><a href="#f64">409</a></td></tr>
+
+<tr>
+  <td class="tdl">Professor E. E. Barnard</td>
+  <td class="tdr"><a href="#f65">410</a></td></tr>
+
+</table>
+
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_13">[Pg 13]</span></p>
+
+<p class="c up sp" id="c1">THE STORY</p>
+</div>
+
+<p class="c less sp">OF THE</p>
+
+<p class="c up sp">SUN, MOON, AND STARS.</p>
+
+<hr class="r65">
+
+
+<h2>CHAPTER I.</h2>
+
+<p class="c sp">THE EARTH ONE OF A FAMILY.</p>
+
+
+<p><span class="smcap large">What</span> is this earth of ours?</p>
+
+<p>Something very great—and yet something very
+little. Something very great, compared with the
+things upon the earth; something very little, compared
+with the things outside the earth.</p>
+
+<p>And as our journeyings together are for a while to
+be away from earth, we shall find ourselves obliged
+to count her as something quite small in the great
+universe, where so many larger and mightier things
+are to be found,—if indeed they are mightier. Not
+that we have to say good-bye altogether to our old
+home. We must linger about her for a while before
+starting, and afterwards it will be often needful to
+come back, with speed swifter than the flight of light,
+that we may compare notes on the sizes and conditions
+of other places visited by us.</p>
+
+<p>But first of all: what <i>is</i> this earth of ours?</p>
+
+<p>It was rather a pleasant notion which men held in
+olden days, that we—that great and important “We”<span class="pagenum" id="Page_14">[Pg 14]</span>
+which loves to perch itself upon a height—stood firm
+and fixed at the very center of everything. The earth
+was supposed to be a vast flat plain, reaching nobody
+could tell how far. The sun rose and set for us alone;
+and the thousands of stars twinkled in the sky at night
+for nobody’s good except ours; and the blue sky overhead
+was a crystal covering for the men of our earth,
+and nothing more. In fact, people seem to have
+counted themselves not merely to have had a kind of
+kingship over the lower animals of our earth, but to
+have been kings over the whole universe. Sun, stars,
+and sky, as well as earth, were made for man, and for
+man only.</p>
+
+<p>This was the common belief, though even in those
+olden days there were <i>some</i> who knew better. But the
+world in general knows better now.</p>
+
+<p>Earth the center of the universe! Why, she is not
+that of even the particular family in the heavens to
+which she belongs. For we do not stand alone. The
+earth is one of a family of worlds, and that family is
+called <span class="smcap">The Solar System</span>. And so far is our earth
+from being the head of the family, that she is not
+even one of the more important members. She is
+merely one of the little sisters, as it were.</p>
+
+<p>Men not only believed the earth, in past days, to
+be at the center of the universe; but also they believed
+her to remain there without change. Sun, moon, stars,
+planets, sky, might move; but never the earth. The
+solid ground beneath their feet, <i>that</i> at least was firm.
+Every day the sun rose and set, and every night the
+stars, in like manner, rose and set. But this was
+easily explained. We on our great earth stood firm<span class="pagenum" id="Page_15">[Pg 15]</span>
+and still, while sun, moon, stars, went circling round
+us once in every twenty-four hours, just for our sole
+and particular convenience. What an important personage
+man must have felt himself then in God’s great
+universe! Once again, we know better now!</p>
+
+<div class="figcenter" id="f4">
+<img src="images/fig4.jpg" alt="solar">
+<p class="caption">THE SOLAR SYSTEM.</p>
+</div>
+
+<p><span class="pagenum" id="Page_16">[Pg 16]</span></p>
+
+<p>For it is the earth that moves, and not the sun; it
+is the earth that moves, and not the stars. The daily
+movements of sun and stars, rising in the east, traveling
+over the sky, and setting in the west, are no more
+real movements on their part than, when we travel in
+a rail way-train, the seeming rush of hedges, telegraph
+posts, houses, and fields is real. They are fixed and
+we are moving; yet the movement appears to us to be
+not ours but theirs.</p>
+
+<p>Still more strongly would this appear to be the case
+if there were no noise, no shaking, no jarring and
+trembling, to make us feel that we are not at rest.
+Sometimes when a train begins to move gently out of
+a station, from among other trains, it is at the first
+moment quite impossible to say whether the movement
+belongs to the train in which we are seated or to
+a neighboring train. And in the motions of our earth
+there is no noise, no shaking, no jarring—all are rapid,
+silent, and even.</p>
+
+<p>If you were rising through the air in a balloon, you
+would at first only know your own movement by seeing
+the earth seem to drop away from beneath you.
+And just so we can only know the earth’s movements
+by seeing how worlds around us <i>seem</i> to move in consequence.</p>
+
+<p>When I speak of the Universe, I mean the whole of
+God’s mighty creation as far as the stars reach. Sometimes
+the word is used in this sense, and sometimes
+it is used only for a particular part of creation nearer
+to us than other parts. At present, however, we will
+put aside all thought of the second narrower meaning.</p>
+
+<p>The wisest astronomer living can not tell us how<span class="pagenum" id="Page_17">[Pg 17]</span>
+far the stars reach. We know now that there is no
+firm crystal covering over our heads, dotted with
+bright points here and there; but only the wide open
+sky or heaven, containing millions of stars, some
+nearer, some farther, some bright enough to be seen
+by us all, some only visible through a telescope.</p>
+
+<p>People talk often of the stars being “set in space;”
+and the meaning of “space” is simply “room.” Where
+you are must be space, or you could not be there.
+But it is when we get away from earth, and travel in
+thought through the wide fields of space, where God
+has placed his stars, that we begin to feel how vast it
+is, and what specks we are ourselves—nay, what a
+speck our very earth is, in this great and boundless
+creation.</p>
+
+<p>For there is no getting to the borders of space.
+As one telescope after another is made, each one
+stronger in power and able to reach farther than the
+last, still more and more stars are seen, and yet more
+and more behind and beyond, in countless millions.</p>
+
+<p>It is the same all round the earth. The old notion
+about our world being a flat plain has been long since
+given up. We know her now to be a round globe,
+not fixed, but floating like the stars in space.</p>
+
+<p>When you look <i>up</i> into the sky, you are looking
+exactly in the opposite direction from where
+you would be looking <i>up</i> if you were in Australia.
+For Australia’s “up” is our “down,” and our “down”
+is Australia’s “up.” Or, to put it more truly, “up” is
+always in the direction straight away from this earth,
+on whatever part of it you may be standing; and
+“down” is always towards the center of the earth.</p>
+
+<p><span class="pagenum" id="Page_18">[Pg 18]</span></p>
+
+<p>All round the globe, in north, south, east, west,
+whether you are in Europe, Asia, Africa, or America,
+though you will see different stars in certain different
+quarters of the earth, still overhead you will find shining
+countless points of light.</p>
+
+<p>And now, what are these stars? This is a matter
+on which people are often confused, and on which
+it is well to be quite clear before going one step
+farther.</p>
+
+<p>Some of the stars you have most likely often noticed.
+The seven chief stars of the Great Bear are
+known to a large number of people; and there are few
+who have not admired the splendid constellation of
+Orion. Perhaps you also know the W-shape of Cassiopeia,
+and the brilliant shining of Sirius, and the
+soft glimmer of the Pleiades.</p>
+
+<p>The different constellations or groups of principal
+stars have been watched by men for long ages past.
+They are called the fixed stars, for they do not change.
+How many thousands of years ago they were first arranged
+by men into these groups, and who first gave
+them their names, we can not tell.</p>
+
+<p>True, night by night, through century after century,
+they rise, and cross the sky, and set. But those
+are only seeming movements. Precisely as the turning
+round of the earth upon her axis, once in every
+twenty-four hours, makes the sun appear to rise and
+cross the sky and set, in the day-time; so also the
+same turning of the earth makes the stars appear to
+do the same in the night-time.</p>
+
+<p>There is another seeming movement among the
+stars, which is only in seeming. Some come into<span class="pagenum" id="Page_19">[Pg 19]</span>
+view in summer which can not be seen in winter; and
+some come into view in winter which can not be seen
+in summer. For the sun, moving on his pathway
+through the sky, hides those stars which shine with
+him in the day-time. The zodiac is an imaginary
+belt in the heavens, sixteen or eighteen degrees wide,
+containing the twelve constellations through which
+the sun passes. And as he passes from point to point
+of his pathway, he constantly conceals from us fresh
+groups of stars by day, and allows fresh groups to appear
+by night.
+Speaking generally,
+however,
+the stars remain
+the same year
+after year, century
+after century.
+The groups
+may still be seen
+as of old, fixed
+and unchanging.</p>
+
+<div class="figright" id="f5">
+<img src="images/fig5.jpg" alt="pleiades">
+<p class="caption">THE PLEIADES.</p>
+</div>
+
+<p>What are these stars? Stars and planets have
+both been spoken about. There is a great difference
+between the two.</p>
+
+<p>Perhaps if you were asked whether the sun is most
+like to a star or a planet, you would be rather at a loss;
+and many who have admired the brilliant evening
+star, Venus, often to be seen after sunset, would be
+surprised to learn that the evening star is in reality no
+star at all.</p>
+
+<p>A star is a sun. Our sun is nothing more nor less
+than a star. Each one of the so-called “fixed stars,”<span class="pagenum" id="Page_20">[Pg 20]</span>
+that you see shining at night in the sky, is a sun like
+our sun; only some of the stars are larger suns and
+some are smaller suns than ours.</p>
+
+<p>The main reason why our sun looks so much larger
+and brighter than the stars is, that he is so very much
+nearer to us. The stars are one and all at enormous
+distances from the earth. By and by we will go more
+closely into the matter of their distance, compared
+with the distance of the sun.</p>
+
+<p>At present it is enough to say that if many of the
+stars were placed just as near to us as our sun is
+placed, they would look just as large and bright;
+while there are some that would look a great deal
+larger and brighter. And if our sun were to travel
+away from us, to the distance of the very nearest
+of the little twinkling stars, he would dwindle down
+and down in size and brilliancy, till at last we should
+not be able to tell him apart from the rest of the
+stars.</p>
+
+<p>I have told you that the stars are called “fixed”
+because they keep their places, and do not change from
+age to age. Though the movement of the earth makes
+them seem all to sweep past every night in company,
+yet they do not travel in and out among one another,
+or backwards and forwards, or from side to side. At
+all events, if there be such changes, they are so slow
+and so small as to be exceedingly difficult to find out.
+Each group of stars keeps its own old shape, as for
+hundreds of years back.</p>
+
+<p>But among these fixed stars there are certain stars
+which do go to and fro, and backwards and forwards.
+Now they are to be seen in the middle of one constellation,<span class="pagenum" id="Page_21">[Pg 21]</span>
+and now in the middle of another. These restless
+stars were long a great perplexity. Men named
+them Planets or Wanderers.</p>
+
+<p>We know now that the planets are in reality not
+stars at all, and also that they are not nearly so far
+away from us as the fixed stars. In fact, they are
+simply members of our own family—the Solar System.
+They are worlds, more or less like the world we live
+in; and they travel round and round the sun as we
+do, each more or less near to him; and they depend
+upon him for heat and light, in more or less the same
+manner as ourselves.</p>
+
+<p>Therefore, just as our sun is a star, and stars are
+suns, so our earth or world is a planet, and planets
+are worlds. <span class="smcap">Earth</span> is the name we give to that particular
+world or planet on which we live. Planets
+may generally be known from stars by the fact that
+they do not twinkle. But the great difference between
+the two lies in the fact that a star shines by
+its own radiant, burning light, whereas a planet shines
+merely by light reflected or borrowed from the sun.</p>
+
+<p>But how were the earth and the other worlds made?
+Let us imagine an immense gaseous mass placed in
+space. Attraction is a force inherent in every atom of
+matter. The denser portion of this mass will insensibly
+attract towards it the other parts, and in the slow
+fall of the more distant molecules towards this more
+attractive region, a general motion is produced, incompletely
+directed towards this center, and soon involving
+the whole mass in the same motion of rotation.
+The simplest form of all, even in virtue of this
+law of attraction, is the spherical form. It is that<span class="pagenum" id="Page_22">[Pg 22]</span>
+which a drop of water takes, and a drop of mercury
+if left to itself.</p>
+
+<p>The laws of mechanics show that, as this gaseous
+mass condenses and shrinks, the motion of rotation of
+the nebula is accelerated. In turning, it becomes
+flattened at the poles, and gradually takes the form of
+an immense lens-shaped mass of gas. It has begun
+to turn so quickly as to develop at its exterior circumference
+a centrifugal force superior to the general
+attraction of the mass, as when we whirl a sling. The
+inevitable consequence of this excess is a rupture of
+the equilibrium, which detaches an external ring.
+This gaseous ring will continue to rotate in the same
+time and with the same velocity; but the nebulous
+mother will be henceforth detached, and will continue
+to undergo progressive condensation and acceleration
+of motion. The same feat will be reproduced as often
+as the velocity of rotation surpasses that by which the
+centrifugal force remains inferior to the attraction. It
+may have happened also that secondary centers of
+condensation would be formed even in the interior of
+the nebula.</p>
+
+<p>In our system the rings of Saturn still subsist.</p>
+
+<p>The successive formation of the planets, their situation
+near the plane of the solar equator, and their
+motions of translation round the same center, are explained
+by the theory which we are discussing. The
+most distant known planet, Neptune, would be detached
+from the nebula at the epoch when this nebula
+extended as far as the planet, out to nearly three thousand
+millions of miles, and would turn in a slow revolution
+requiring a period of 165 years for its accomplishment.<span class="pagenum" id="Page_23">[Pg 23]</span>
+The original ring could not remain in the
+state of a ring unless it was perfectly homogeneous
+and regular; but such a condition is, so to say, unrealizable,
+and it did not delay in condensing itself into
+a sphere. Successively, Uranus, Saturn, Jupiter, the
+army of small planets, Mars, would thus be detached
+or formed in the interior of this same nebula. Afterwards
+came the earth, of which the birth goes back
+to the epoch when the sun had arrived at the earth’s
+present position. Venus and Mercury would be born
+later. Will the sun give birth to a new world? This
+is not probable.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_24">[Pg 24]</span></p>
+
+<h2 class="nobreak" id="c2">CHAPTER II</h2>
+</div>
+
+<p class="c sp">THE HEAD OF OUR FAMILY.</p>
+
+
+<p><span class="smcap large">People</span> began very early in the history of the
+world to pay close attention to the sun. And no
+wonder. We owe so much to his heat and light that
+the marvel would be if men had not thought much
+about him.</p>
+
+<p>Was the sun really any larger than he looked, and
+if so, how much larger was he? And what was his
+distance from the earth? These were two of the questions
+which puzzled our ancestors the longest. If
+once they could have settled exactly how far off the
+sun really was, they could easily have calculated his
+exact size; but this was just what they could not do.</p>
+
+<p>So one man supposed that the sun must be quite
+near, and very little larger than he looked. Another
+thought he might be seventy-five miles in diameter.
+A third ventured to believe that he was larger than
+the country of Greece. A fourth was so bold as to
+imagine that he might even outweigh the earth
+herself.</p>
+
+<p>After a while many attempts were made to measure
+the distance of the sun; and a great many different
+answers to this difficult question were given by different
+men, most of them very wide of the mark. It is
+only of late years that the matter has been clearly
+settled. And, indeed, it was found quite lately that a
+mistake of no less than three millions of miles had<span class="pagenum" id="Page_25">[Pg 25]</span>
+been made, notwithstanding all the care and all the
+attention given. But though three millions of miles
+sounds a great deal, yet it is really very little—only a
+tiny portion of the whole.</p>
+
+<p>For the distance of the sun from the earth is no
+less than about <span class="allsmcap">NINETY-THREE MILLIONS OF MILES</span>.
+Ninety-three millions of miles! Can you picture that
+to yourself? Try to think what is meant by a thousand
+miles. Our earth is eight thousand miles in
+diameter. In other words, if you were to thrust a
+gigantic knitting-needle through her body, from the
+North Pole to the South Pole, it would have to be
+about eight thousand miles long.</p>
+
+<p>To reach the thought of one million, you must picture
+<i>one thousand times one thousand</i>. Our earth is
+about twenty-five thousand miles round. If you were
+to start from the mouth of the River Amazon, in South
+America, and journey straight round the whole earth on
+the equator, till you came back to the same point, you
+would have traveled about twenty-five thousand miles.
+But that would be a long way off from a million miles.
+You would have gone only once round the earth.
+Now a cord one million miles in length could be
+wrapped, not once only, but <i>forty times</i>, round and
+round the earth. And when you have managed to
+reach up to the thought of one million miles, you have
+then to remember that the sun’s distance is ninety-three
+times as much again. So, to picture clearly to
+ourselves the actual meaning of “ninety-three millions
+of miles” is not so easy.</p>
+
+<p>Suppose it were possible to lay a railroad from here
+to the sun. If you could journey thither in a perfectly<span class="pagenum" id="Page_26">[Pg 26]</span>
+straight line, at the rate of thirty miles an hour,
+never pausing for one single minute, night or day, you
+would reach the sun in about three hundred and forty-six
+years.</p>
+
+<p>Thirty miles an hour is a slow train. Suppose we
+double the speed, and make it an express train, rushing
+along at the pace of sixty miles an hour. Then
+you might hope to reach the end of your journey in
+one hundred and seventy-three years. If you had
+quitted this earth early in the eighteenth century,
+never stopping on your way, you would be, just about
+now, near the end of the nineteenth, arriving at the sun.</p>
+
+<p>So much for the sun’s distance from us. Now as
+to his size.</p>
+
+<p>I have already mentioned that our earth’s diameter—that
+is, her <i>through measure</i>, as, for instance, the
+line drawn straight from England through her center
+to New Zealand—is about eight thousand miles. This
+sounds a good deal. But what do you think of the
+diameter of the sun being no less than <i>eight hundred
+and fifty-eight thousand miles</i>? The one is eight thousand
+miles, the other over eight hundred thousand!</p>
+
+<p>Suppose you had a long slender pole which would
+pass through the middle of the earth, one end just
+showing at the North Pole and the other at the South
+Pole. You would need more than a hundred and
+eight of such poles, all joined together, to show the
+diameter of the sun.</p>
+
+<p>The sun seems not to be made of nearly such heavy
+materials as the earth. He is what astronomers call
+less “dense,” less close and compact in his make, just
+as wood is less dense and heavy than iron. Still, his<span class="pagenum" id="Page_27">[Pg 27]</span>
+size is so enormous, that if you could have a pair of
+gigantic scales, and put the sun into one scale and
+the earth with every one of her brother and sister
+planets into the other, the sun’s side would go down
+like lightning. He would be found to weigh seven
+hundred and fifty times as much as all the rest put
+together. And, it would take more than twelve hundred
+thousand little earths like ours, rolled into one
+huge ball, to make a globe as large as the sun.</p>
+
+<p>In the beginning of the seventeenth century a man
+named Fabricius was startled by the sight of a certain
+black spot upon the face of the sun. He watched till
+too dazzled to look any longer, supposing it to be a
+small cloud, yet anxious to learn more. Next day
+the spot was there still, but it seemed to have moved
+on a little way. Morning after morning this movement
+was found to continue, and soon a second spot, and
+then a third spot, were observed creeping in like manner
+across the sun. After a while they vanished, one
+at a time, round his edge, as it were; but after some
+days of patient waiting on the part of the lookers-on,
+they appeared again at the opposite edge, and once
+more began their journey across.</p>
+
+<p>Fabricius seems to have been the first, but he was
+not the last, to watch sun-spots. Many astronomers
+have given close attention to them. Modern telescopes,
+and the modern plan of looking at the sun
+through darkened glass, have made this possible in a
+way that was not possible two or three hundred years
+ago.</p>
+
+<p>The first important discovery made through the
+spots on the sun, was that the sun turns round upon<span class="pagenum" id="Page_28">[Pg 28]</span>
+his axis, just in the same manner that the earth turns
+round upon hers. Instead of doing so once in the
+course of each twenty-four hours, like the earth, he
+turns once in the course of about twenty-five days.</p>
+
+<p>It must not be supposed that the spots seen now
+upon the sun are the same spots that Fabricius saw
+so long ago. There is perpetual change going on;
+new spots forming, old spots vanishing; one spot breaking
+into two, two spots joining into one, and so on.
+Even in a single hour great alterations are sometimes
+seen to take place.</p>
+
+<p>Still, many of the spots do remain long enough and
+keep their shapes closely enough to be watched from
+day to day, and to be known again as old friends when
+they reappear, after being about twelve days hidden
+on the other side of the sun. So that the turning of
+the sun upon his axis has become, after long and careful
+examination, a certain known fact.</p>
+
+<p>For more than thirty years one astronomer kept
+close watch over the spots on every day that it was
+possible to see the sun. Much has been learned from
+his resolute perseverance.</p>
+
+<p>Now what are these spots?</p>
+
+<p>One thing seems pretty sure, and that is that they
+are caused by some kind of tremendous storms or
+cyclones taking place on the surface of that huge ball
+of fire.</p>
+
+<div class="figcenter" id="f6">
+<img src="images/fig6.jpg" alt="sun spots">
+<p class="caption">SUN SPOTS.</p>
+</div>
+
+<p>The first attentive observer of the sun, Scheiner,
+at first regarded the spots as satellites—an indefensible
+opinion, which, however, some have attempted to
+revive. Galileo attributed them to clouds or vapors
+floating in the solar atmosphere; this was the best
+<span class="pagenum" id="Page_29">[Pg 29]</span>conclusion which could be drawn from the observations
+of that epoch. This opinion met for a long
+time with general approval; it has even been renewed
+in our day. Some astronomers, and among them
+Lalande, believed, on the contrary, that they were
+mountains, of which the flanks, more or less steep,
+might produce the aspect of the penumbra—an opinion
+irreconcilable with the proper motion which the
+spots sometimes possess in a very marked manner.
+It is not usual, in fact, to see mountains traveling.<span class="pagenum" id="Page_30">[Pg 30]</span>
+Derham attributed them to the smoke issuing from
+the volcanic craters of the sun, an opinion revived and
+maintained in recent times by Chacornac. Several
+<i>savants</i>, regarding the sun as a liquid and incandescent
+mass, have also explained the spots by immense cinders
+floating on this ocean of fire. But a century had
+scarcely elapsed after the epoch when the spots were
+observed for the first time, when an English astronomer,
+Wilson, showed with certainty that the spots are
+hollow.</p>
+
+<p>We do not know with any certainty whether the
+sun is through and through one mass of glowing molten
+heat, or whether he may have a solid and even
+cool body within the blazing covering. Some have
+thought the one, and some the other. We only know
+that he is a mighty furnace of heat and flame, beyond
+anything that we can possibly imagine on our quiet
+little earth.</p>
+
+<p>It seems very sure that no such thing as “quietness”
+is to be found on the surface of the sun. The wildest
+and fiercest turmoil of rushing wind and roaring flame
+there prevails. The cyclones or hurricanes which take
+place are sometimes so rapid and so tremendous in
+extent, tearing open the blazing envelope of the sun,
+and showing glimpses of fiery though darker depths
+below, that we, on our far-distant earth, can actually
+watch their progress.</p>
+
+<p>Astronomers speak of the “quivering fringe of fire”
+all around the edge of the sun, visible through telescopes.
+But the sun is perpetually turning on his
+axis, so that each hour fresh portions of his surface
+thus pass the edge, showing the same appearance.<span class="pagenum" id="Page_31">[Pg 31]</span>
+What conclusion can we come to but that the whole
+enormous surface of the sun is one restless, billowy
+sea of fire and flame?</p>
+
+<p>It sounds to us both grand and startling to hear of
+the mighty outbreaks from Mount Vesuvius, or to read
+of glowing lava from a volcano in Hawaii pouring in
+one unbroken stream for miles.</p>
+
+<p>But what shall be thought of rosy flames mounting
+to a height of fifty or a hundred thousand miles above
+the edge of the sun? What shall be thought of a
+tongue of fire long enough to fold three or four times
+round our solid earth? What shall be thought of the
+awful rush of burning gases, sometimes seen, borne
+along at the rate of one or two or even three hundred
+miles in a single second across the sun’s surface?
+What shall be thought of the huge dark rents in this
+raging fiery ocean, rents commonly from fifty to one
+hundred thousand miles across, and not seldom more?</p>
+
+<p>Fifty thousand miles! A mere speck, scarcely
+visible without a telescope; yet large enough to hold
+seven earths like ours flung in together. The largest
+spot measured was so enormous that eighteen earths
+might have been arranged in a row across the breadth
+of it, like huge boulders of rock in a mountain cavern;
+and to have filled up the entire hole about one hundred
+earths would have been needed.</p>
+
+<p>It is well to grow familiar with certain names given
+by astronomers to certain parts of the sun.</p>
+
+<p>The round shining disk or flat surface, seen by all
+of us, is called the <i>photosphere</i>, or “light-sphere.” It
+has a tolerably well-defined edge or “limb,” and dazzles
+the eye with its intense brightness.</p>
+
+<p><span class="pagenum" id="Page_32">[Pg 32]</span></p>
+
+<p>Across the photosphere the spots move, sometimes
+many, sometimes few, in number. Besides the dark
+spots, there are spots of extreme brilliancy, standing
+out on even that dazzling surface, which causes a piece
+of white-hot iron to look black and cold by contrast.
+These extra-radiant spots which come and go, and at
+times change with great rapidity, are named <i>faculæ</i>—a
+Latin word meaning “torches.”</p>
+
+<p>At the edge of the photosphere astronomers see
+what has been already mentioned, that which is sometimes
+called the <i>chromotosphere</i>, which one has named
+“the <i>sierra</i>,” and which another has described as “a
+quivering fringe of fire.” The waves of the sea, on a
+stormy day, seen in the distance rising and breaking
+the horizon-line, may serve as an illustration; only in
+the sun the waves are of fire, not water. What must
+their height be, to be thus visible at a distance of
+ninety-three millions of miles?</p>
+
+<p>Outside the <i>sierra</i> are seen, at certain seasons,
+bright, “rose-colored prominences” or flames of enormous
+height. During an eclipse, when the dark body
+of the moon comes between the sun and us, exactly
+covering the photosphere, these red tips stand out
+distinctly beyond the edge of sun and moon. Their
+changes have been watched, and their height repeatedly
+measured. Some are so lofty that ten little earths
+such as ours might be heaped up, one upon another,
+without reaching to their top. Whether they are in
+character at all like the outbursts from our own volcanoes
+it is hard to say. To compare the two would
+be rather like comparing a small kitchen fire with
+a mighty iron-smelting furnace. The faculæ, the<span class="pagenum" id="Page_33">[Pg 33]</span>
+sierra, and the prominences are visible only through
+a telescope.</p>
+
+<p>Outside these red flames or “prominences” is the
+corona, commonly divided into the inner and outer
+coronas.</p>
+
+<p>Many different explanations have been offered of
+this beautiful crown of light round the sun, plainly
+visible to the naked eye during an eclipse. But here
+again we know little, and must be content to watch
+and wait.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_34">[Pg 34]</span></p>
+
+<h2 class="nobreak" id="c3">CHAPTER III.</h2>
+</div>
+
+<p class="c sp">WHAT BINDS THE FAMILY TOGETHER?</p>
+
+
+<p><span class="smcap large">What</span> is it which binds together all the members
+of the Solar System? Ah, what? Why should not
+the sun at any moment rush away in one direction,
+the earth in a second, the planets in half a dozen
+others? What is there to hinder such a catastrophe?
+Nothing—except that they are all held together by a
+certain close family tie; or, more correctly, by the
+powerful influence of the head of the family.</p>
+
+<p>This mysterious power which the sun has, and
+which all the planets have also in their smaller degrees,
+is called Attraction. Sometimes it is named
+Gravitation or Gravity. When we speak, as we often
+do, of the <i>law</i> of attraction or gravitation, we mean
+simply this—that throughout the universe, in things
+little and great, is found a certain wonderful <i>something</i>,
+in constant action, which we call a “law.”
+What the “something” may be, man can not tell;
+for he knows it only by its effects. But these effects
+are seen everywhere, on all sides, in the earth and in
+the universe. It is well named in being called a
+“law;” for we are compelled to obey it. None but
+the Divine Lawgiver who made this law can for a single
+moment suspend its working.</p>
+
+<p>What causes an apple to fall to the ground when
+it drops from the branch? Why should it not, instead,
+rise upwards? Because, of course, it is heavy, or has<span class="pagenum" id="Page_35">[Pg 35]</span>
+weight. But what <i>is</i> weight? Simply this—that the
+earth draws or drags everything downwards towards
+herself by the power of attraction. Every substance,
+great or small, light or heavy, is made up of tiny
+atoms. Each one of these atoms attracts or draws
+all the other atoms towards itself; and the closer
+they are together, the more strongly they pull one
+another.</p>
+
+<p>The atoms in a piece of iron are much closer than
+the atoms in a piece of wood; therefore the iron is
+called the “more <i>dense</i>” of the two, and its weight or
+“mass” is greater. The more closely the atoms are
+pressed together, the greater the number of them in
+a small space, and the more strong the drawing towards
+the earth; for the earth draws each one of these
+atoms equally. That is only another way of saying
+that a thing is “heavier.” If you drop a stone from
+the top of a cliff, will it rise upwards or float in the
+air? No, indeed. The pull of the earth’s attraction,
+dragging and still dragging downward, makes it rush
+through the air, with speed quickening each instant,
+till it strikes the ground. Every single atom in every
+single body <i>pulls</i> every other atom, whether far or
+near. The nearer it is, the stronger always the
+pulling.</p>
+
+<p>We do not always feel this, because the very much
+greater attraction of the earth hides—or smothers, as
+we may say—the lesser attraction of each small thing
+for another. But though you and I might stand side
+by side upon earth, and feel no mutual attraction, yet
+if we could mount up a few thousands of miles, far
+away from earth, and float in distant space, there we<span class="pagenum" id="Page_36">[Pg 36]</span>
+should find ourselves drawn together, and unable to
+remain apart.</p>
+
+<p>Now precisely as an apple falling from a tree and
+a stone dropping from a cliff are dragged downward
+to the earth, just so our earth and all the planets are
+dragged downwards towards the sun and towards each
+other. The law of the earth’s attraction of all objects
+on its surface to itself was indistinctly suspected a
+very long time ago; but it was the great Newton who
+first discovered that this same law was to be found
+working among the members of the whole Solar System.
+The sun attracts the earth, and the earth attracts
+the sun. But the enormous size of the sun
+compared with our earth—like a great nine-foot globe
+beside a tiny one-inch ball—makes our power of attraction
+to be quite lost sight of in his, which is so
+much greater.</p>
+
+<p>The principle of gravitation is of far wider scope
+than we have yet indicated. We have spoken merely
+of the attraction of the earth, and we have stated that
+its attraction extends throughout space. But the law
+of gravitation is not so limited. Not only does the
+earth attract every other body, and every other body
+attract the earth, but each of these bodies attracts
+each other; so that, in its more complete shape, the
+law of gravitation announces that “every body in the
+universe attracts every other body with a force which
+varies inversely as the square of the distance.” It is
+impossible for us to overestimate the importance of
+this law. It supplies the clue by which we can unravel
+the complicated movements of the planets. It
+has led to marvelous discoveries, in which the law of<span class="pagenum" id="Page_37">[Pg 37]</span>
+gravitation has enabled us to anticipate the telescope,
+and, indeed, actually to feel the existence of bodies
+before those bodies have even been seen.</p>
+
+<p>We come now to another question. If the sun is
+pulling with such power at the earth and all her sister
+planets, why do they not fall down upon him?
+What is to prevent their rolling some day into one of
+those deep rents in his fiery envelope? Did you ever
+tie a ball to a string, and swing it rapidly round and
+round your head? If you did, you must have noticed
+the steady outward pull of the ball. The heavier the
+ball, and the more rapid its whirl, the stronger the pull
+will be. Let the string slip, and the rush of the ball
+through the air to the side of the room will make this
+yet more plain. Did you ever carry a glass of water
+quickly along, and then, on suddenly turning a corner,
+find that the water has not turned with you? It has
+gone on in its former direction, leaving the glass, and
+spilling itself on the floor.</p>
+
+<p>The cause in both cases is the same. Here is another
+“law of nature,” so-called. Though we can
+neither explain nor understand why and how it is so,
+we see it to be one of the fixed rules of God’s working
+in every-day life throughout his universe. The law,
+as we see it, seems to be this: Everything which is at
+rest must remain at rest, until set moving by some
+cause outside of, or independent of itself; and everything
+which is once set moving, must continue moving
+in a straight line until checked.</p>
+
+<p>According to this a cannon-ball lying on the ground
+ought to remain there until it is set in motion; and,
+once set in motion by being fired from a cannon, it ought<span class="pagenum" id="Page_38">[Pg 38]</span>
+to go on forever. Exactly so—if nothing stops it. But
+the earth’s attraction draws the cannon-ball downward,
+and every time it strikes the ground it is partly
+checked. Also each particle of air that touches it
+helps to bring it to rest. If there were no earth
+and no air in the question, the cannon-ball might rush
+on in space for thousands of years.</p>
+
+<p>Why did the water get spilled? Because it necessarily
+continued moving in a straight line. Your sudden
+change of direction compelled the solid glass to
+make the same change, but the liquid water was free to
+go straight on in its former course; so it obeyed this
+law, and <i>did</i> go on. Why did the ball pull hard at the
+string as you swung it round? Because at each instant
+it was striving to obey this same law, and to
+rush onward in a straight line. The pull of the string
+was every moment fighting against that inclination,
+and forcing the ball to move in a circle.</p>
+
+<p>Just such is the earth’s movement in her yearly
+journey round the sun. The string holding in the
+ball pictures the sun’s attraction holding in the earth.
+The pulling of the ball outward in order to continue
+its course in a straight line, pictures the pulling of
+our earth each moment to break loose from the sun’s
+attraction and to flee away into distant space.</p>
+
+<p>For the earth is not at rest. Each tick of the clock
+she has sped onward over more than eighteen miles
+of her pathway through the sky. Every instant the
+sun is dragging, with the tremendous force of his attraction,
+to make her fall nearer to him. Every instant
+the earth is dragging with the tremendous force
+of her rapid rush, to get away from him. These two<span class="pagenum" id="Page_39">[Pg 39]</span>
+pullings so far balance each other, or, more strictly, so
+far combine together, that between the two she journeys
+steadily round and round in her nearly circular
+orbit.</p>
+
+<p>If the sun pulled a little harder she would need to
+travel a little faster, or she would gradually go nearer
+to him. If the earth went faster, and the sun’s attraction
+remained the same as it is now, she would
+gradually widen her distance. Indeed, it would only
+be needful for the earth to quicken her pace to
+about five-and-twenty miles a second, the sun’s power
+to draw her being unchanged, and she would then
+wander away from him for ever. Day by day we on
+our earth should travel farther and farther away, leaving
+behind us all light, all heat, all life, and finding
+ourselves slowly lost in darkness, cold, and death.</p>
+
+<p>For what should we do without the sun? All our
+light, all our warmth, come from him. Without the
+sun, life could not exist on the earth. Plants, herbage,
+trees, would wither; the waters of rivers, lakes, oceans,
+would turn to masses of ice; animals and men would
+die. Our earth would soon be one vast, cold, forsaken
+tomb of darkness and desolation.</p>
+
+<p>We may not think so, but everything which moves,
+circulates, and lives on our planet is the child of the
+sun. The most nutritious foods come from the sun.
+The wood which warms us in winter is, again, the sun
+in fragments. Every cubic inch, every pound of wood,
+is formed by the power of the sun. The mill which
+turns under the impulse of wind or water, revolves
+only by the sun. And in the black night, under the
+rain or snow, the blind and noisy train, which darts<span class="pagenum" id="Page_40">[Pg 40]</span>
+like a flying serpent through the fields, rushes along
+above the valleys, is swallowed up under the mountains,
+goes hissing past the stations, of which the pale eyes
+strike silently through the mist,—in the midst of night
+and cold, this modern animal, produced by human industry,
+is still a child of the sun. The coal from the
+earth which feeds its stomach is solar work, stored up
+during millions of years in the geological strata of
+the globe.</p>
+
+<p>As it is certain that the force which sets the watch
+in motion is derived from the hand which has wound
+it, so it is certain that all terrestrial power proceeds
+from the sun. It is its heat which maintains the three
+states of bodies—solid, liquid, and gaseous. The last
+two would vanish, there would be nothing but solids;
+water and air itself would be in massive blocks,—if
+the solar heat did not maintain them in the fluid state.
+It is the sun which blows in the air, which flows in
+the water, which moans in the tempest, which sings
+in the unwearied throat of the nightingale. It attaches
+to the sides of the mountains the sources of the
+rivers and glaciers, and consequently the cataracts and
+the avalanches are precipitated with an energy which
+they draw directly from him. Thunder and lightning
+are in their turn a manifestation of his power. Every
+fire which burns and every flame which shines has received
+its life from the sun. And when two armies
+are hurled together with a crash, each charge of cavalry,
+each shock between two army corps, is nothing
+else but the misuse of mechanical force from the same
+star. The sun comes to us in the form of heat, he
+leaves us in the form of heat; but between his arrival<span class="pagenum" id="Page_41">[Pg 41]</span>
+and his departure, he has given birth to the
+varied powers of our globe.</p>
+
+<p>I have spoken before about the old-world notion
+that our earth was a fixed plain, with the sun circling
+round her. When the truth dawned slowly upon
+some great minds, anxious only to know what really
+was the truth, others made a hard struggle for the
+older and pleasanter mode of thinking. It went with
+many sorely against the grain to give up all idea of
+the earth being the chief place in the universe. Also
+there was something bewildering and dizzying in the
+notion that our solid world is never for one moment
+still. But truth won the victory at last. Men consented
+slowly to give up the past dream, and to learn
+the new lesson put before them.</p>
+
+<p>We still talk of the sun rising and setting, and of
+the stars doing the same. This is, however, merely a
+common form of speech, which means just the opposite.
+For instead of the sun and stars moving, it is
+the earth which moves.</p>
+
+<p>The earth has two distinct movements. Indeed, I
+ought to say that she has three; but we will leave all
+thought of the third for the present. First, she turns
+round upon her axis once in every twenty-four hours.
+Secondly, she travels round the sun once in about every
+three hundred and sixty-five days and a quarter. No
+wonder our ancestors were startled to learn that the
+world, which they had counted so immovable, was perpetually
+spinning like a humming-top, and rushing
+through space like an arrow.</p>
+
+<p>You may gain some clear notions as to the daily
+rising and setting of our sun, with the help of an<span class="pagenum" id="Page_42">[Pg 42]</span>
+orange. Pass a slender knitting-needle through the
+orange, from end to end, and hold it about a yard distant
+from a single candle in a room otherwise darkened.
+Let the needle or axis slant somewhat, and turn the
+orange slowly upon it.</p>
+
+<p>The candle does not move; but as the orange turns,
+the candle-light falls in succession upon each portion
+of the yellow rind. Half of the orange is always in
+shade, and half is always in light; while at either side,
+if a small fly were standing there, he would be passing
+round out of shade into candle-light, or out of candle-light
+into shade.</p>
+
+<p>Each spot on our earth moves round in turn into
+half-light, full-light, half-light, and darkness; or, in
+other words, has morning-dawn, midday-light, evening
+twilight, and night. Each spot on our earth would
+undergo regularly these changes every twenty-four
+hours throughout the year, were it not for another
+arrangement which so far affects this that the North
+and South Poles are, by turns, cut off from the light
+during many months together.</p>
+
+<p>Thus the sun is in the center of the Solar System,
+turning slowly on his axis; and the earth and the
+planets travel round him, each spinning like a teetotum,
+so as to make the most of his bright warm rays.
+But for this spinning movement of the earth, our day
+and night, instead of being each a few hours long,
+would each last six months.</p>
+
+<p>You may notice that, as you turn the orange steadily
+round, the outside surface of the skin has to move
+much more slowly in those parts close to the knitting-needle,
+than in those parts which bulge out farthest<span class="pagenum" id="Page_43">[Pg 43]</span>
+from it. Near the North and South Poles the surface
+of our earth travels slowly round a very small circle in
+the course of twenty-four hours. But at the equator
+every piece of ground has to travel about twenty-five
+thousand miles in the same time; so that it rushes along
+at the rate of more than one thousand miles an hour.
+A man standing on the earth at the equator is being
+carried along at this great speed, not <i>through</i> the air,
+for the whole atmosphere partakes of the same rapid
+motion, but <i>with</i> the air, round and round the earth’s
+axis.</p>
+
+<p>Now about the other movement of the earth—her
+yearly journey round the sun. While she moves, the
+sun, as seen from the earth, seems to change his place.
+First he is observed against a background of one group
+of stars, then against a second, then against a third.
+Not that the stars are visible in the daytime when
+the sun is shining, but their places are well known in
+the heavens; and also they can be noted very soon
+after he sets, or before he rises, so that the constellations
+nearest to him may each day be easily found out.</p>
+
+<p>Of course, in old times the sun was thought to be
+really taking this journey among the stars, and men
+talked of “the sun’s path” in the heavens. This path
+was named “the Ecliptic,” and we use the word still,
+though we know well that the movements are not
+really his, but ours.</p>
+
+<p>As the earth’s daily movement causes day and night,
+so the earth’s yearly movement causes spring, summer,
+autumn, and winter. A few pages back I mentioned,
+in passing, one slight yet important fact which lies at
+the root of this matter about the seasons. The earth,<span class="pagenum" id="Page_44">[Pg 44]</span>
+journeying round the sun, travels with her axis <i>slanting</i>.
+Put your candle in the middle of the table, and
+stand at one end, holding your orange. Now let the
+knitting-needle, with the orange upon it, so slant that
+one end shall point straight over the candle, towards
+the upper part of the wall at the farther end of the
+room. Call the upper end so pointing the North Pole
+of your orange. You will see that the candle-light
+falls chiefly upon the upper half of the orange; and as
+you turn it slowly, to picture day and night, you will
+find that the North Pole has no night, and the South
+Pole has no day. That is summer in the northern
+hemisphere, and winter in the southern.</p>
+
+<p>Walk round next to one side of the table, towards
+the right hand, taking care to let the knitting-needle
+point steadily still in exactly the same direction, not
+towards the same <i>spot</i>, for that would alter its direction
+as you move, but towards the same <i>wall</i>. Stop, and
+you will find the candle lighting up one-half of your
+orange, from the North to the South Poles. Turn it
+slowly, never altering the slope of the axis, and you
+will see that every part of the orange comes by turns
+under the light. This is the Autumnal Equinox,
+when days and nights all over the world are equal in
+length.</p>
+
+<p>Walk on to the other end of the table, still letting
+the needle slope and point steadily as before. Now
+the candle-light will shine upon the lower or South
+Pole, and the North Pole will be entirely in the shade.
+This is summer in the southern hemisphere, and
+winter in the northern.</p>
+
+<p>Pass on to the fourth side of the table, and once<span class="pagenum" id="Page_45">[Pg 45]</span>
+more you will find it, as at the second side, equal light
+from North Pole to South Pole. This will be the
+Spring Equinox.</p>
+
+<p>It is an illustration that may be easily practiced.
+But everything depends upon keeping the slant of the
+needle or axis unchanged throughout. If it be allowed
+to point first to right, and then to left, first towards the
+ceiling, and then towards the wall, the attempt will
+prove a failure.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_46">[Pg 46]</span></p>
+
+<h2 class="nobreak" id="c4">CHAPTER IV.</h2>
+</div>
+
+<p class="c sp">THE LEADING MEMBERS OF OUR FAMILY—FIRST<br>
+GROUP.</p>
+
+
+<p><span class="smcap large">The</span> chief distinction between stars and planets is, as
+before said, that the stars shine entirely by their own
+light, while the planets shine chiefly, if not entirely,
+by reflected light. The stars are suns; mighty globes of
+glowing flame. The planets simply receive the light
+of the sun, and shine with a brightness not their own.</p>
+
+<p>A lamp shines by its own light; but a looking-glass,
+set in the sun’s rays and flashing beams in all directions,
+shines by reflected light. In a dark room it would
+be dark. If there were no sun to shine upon Mars or
+Venus, we should see no brightness in them. The
+moon is like the planets in this. She has only borrowed
+light to give, and none of her own.</p>
+
+<p>Any one of the planets removed to the distance of
+the nearest fixed star, would be invisible to us. Reflected
+light will not shine nearly so far as the direct
+light of a burning body. There may be thousands or
+millions of planets circling round the stars—those
+great and distant suns—just as our brother-planets
+circle round our sun. But it is impossible for us to
+see them. The planets which we can see are close
+neighbors, compared with the stars. I do not mean
+that they are near in the sense in which we speak of
+nearness upon earth. They are only near in comparison
+with what is so very much farther away.</p>
+
+<p><span class="pagenum" id="Page_47">[Pg 47]</span></p>
+
+<p>For a while we must now leave alone all thought
+of the distant stars, and try to gain a clear idea of the
+chief members of our own Family Circle—that family
+circle of which the sun is the head, the center, the
+source of life and warmth and light. There are two
+ways in which astronomers group the planets of the
+Solar System. One way is to divide them into the
+Inferior Planets, and the Superior Planets.</p>
+
+<p>As the earth travels in her pathway round the sun,
+two planets travel on their pathways round the sun
+nearer to him than ourselves. If the pathway or orbit
+of our earth were pictured by a hoop laid upon the
+table, with a ball in the center for the sun; then
+those two planets would have two smaller hoops of
+different sizes <i>within</i> ours; and the rest would have
+larger hoops of different sizes <i>outside</i> ours. The two
+within are called inferior planets, and the rest outside
+are called superior planets.</p>
+
+<p>A round hoop would not make a good picture of
+an orbit. For the yearly pathway of our earth is not
+in shape perfectly round, but slightly oval; and the
+sun is not exactly in the center, but a little to one side
+of the center. This is more or less the case with the
+orbits of all the planets.</p>
+
+<p>But the laying of the hoops upon the table would
+give no bad idea of the way in which the orbits really
+lie in the heavens. The orbits of all the chief planets
+do not slope and slant round the sun in all manner of
+directions. They are placed almost in the same <i>plane</i>
+as it is called—or, as we might say, in the same <i>flat</i>.
+In these orbits the planets all travel round in the same
+direction. One may overtake a second on a neighboring<span class="pagenum" id="Page_48">[Pg 48]</span>
+orbit, and get ahead of him, but one planet never
+goes back to meet another.</p>
+
+<p>In speaking of the orbits, I do not mean that the
+planets have visible marked pathways through the
+heavens, any more than a swallow has a visible pathway
+through the sky, or a ship a marked pathway
+through the sea. Yet each planet has his own orbit,
+and each planet so distinctly keeps to his own, that
+astronomers can tell us precisely whereabouts in the
+heavens any particular planet will be, at any particular
+time, long years beforehand.</p>
+
+<p>There is also another mode of grouping the planets,
+besides dividing them into superior and inferior planets.
+By this other mode we find two principal groups
+or quartets of planets, separated by a zone or belt of a
+great many very small planets.</p>
+
+<table>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdl">{ Mercury.</td></tr>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdl">{ Venus.</td></tr>
+
+<tr>
+  <td class="tdl">First Group</td>
+  <td class="tdl">{ Earth.</td></tr>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdl">{ Mars.</td></tr>
+
+<tr>
+  <td class="tdc" colspan="2">The Asteroids or Planetoids.</td>
+  </tr>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdl">{ Jupiter.</td></tr>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdl">{ Saturn.</td></tr>
+
+<tr>
+  <td class="tdl">Second Group</td>
+  <td class="tdl">{ Uranus.</td></tr>
+
+<tr>
+  <td class="tdl"></td>
+  <td class="tdl">{ Neptune.</td></tr>
+
+
+</table>
+
+<p>The first four are small compared with the last
+four, though much larger than any in the belt of tiny
+Asteroids.</p>
+
+<p>It was believed at one time that a planet had been
+discovered nearer to the sun than Mercury, and the
+name Vulcan was given to it. But no more has been
+seen of Vulcan, and his existence is so doubtful that
+we must not count him as a member of the family
+without further information.</p>
+
+<p><span class="pagenum" id="Page_49">[Pg 49]</span></p>
+
+<p>Mercury is very much smaller than our Earth. The
+diameter of the earth is eight thousand miles, but the
+diameter of Mercury is only about three thousand
+miles—not even half that of the earth. Being so
+much nearer to the sun than ourselves, the pulling of
+his attraction is much greater, and this has to be balanced
+by greater speed, or Mercury would soon fall down
+upon the sun. Our distance from the sun is ninety-three
+millions of miles. Mercury’s distance is only
+about one-third of ours; and instead of traveling, like
+the earth, at the rate of eighteen miles each second,
+Mercury dashes headlong through space at the mad
+pace of twenty-nine miles each second. It is a good
+thing the earth does not follow his example, or she
+would soon break loose from the sun’s control altogether.</p>
+
+<p>The earth takes more than three hundred and sixty-five
+days, or twelve months, to journey round the sun
+in her orbit. That is what we call “the length of our
+year.” But Mercury’s year is only eighty-eight days,
+or not quite three of our months. No wonder!—when
+his pathway is so much shorter, and his speed so much
+greater than ours. So Mercury has four years to one
+year on earth; and a person who had lived on Mercury
+as long as five earthly years, would then be
+twenty years old. The increased number of birthdays
+would scarcely be welcome in large families, supposing
+we could pay a long visit there.</p>
+
+<p>The sun, as seen from Mercury, looks about four
+and a half times as large as from here; the heat and
+glare being increased in proportion. No moon has
+ever been found, belonging to Mercury.</p>
+
+<p><span class="pagenum" id="Page_50">[Pg 50]</span></p>
+
+<p>The planet Mercury is, like the earth and the moon,
+a globe of dark matter which only shines and is visible
+by the illumination of the solar light. Its motion
+round the central star, which brings it sometimes between
+the sun and us, sometimes in an oblique direction,
+sometimes at right angles, and shows us a part
+incessantly variable, of its illuminated hemisphere,
+produces in its aspect, as seen in a telescope, a succession
+of phases similar to those which the moon
+presents to us. The cut represent the apparent variations
+of size and the succession of phases, visible in
+the evening after sunset; when the planet attains its
+most slender crescent, it is in the region of its orbit
+nearest to the earth, and passes between the sun and
+us; then, some weeks afterwards, it emerges from the
+solar rays and passes again through the same series
+of phases in inverse order, as we see them by reversing
+the figure.</p>
+
+<div class="figcenter" id="f7">
+<img src="images/fig7.jpg" alt="mercury">
+<p class="caption">PHASES OF MERCURY BEFORE INFERIOR CONJUNCTION—EVENING<br>
+STAR.</p>
+</div>
+
+<p>Venus, the second inferior planet, is nearly the same
+size as our earth. Seen from the earth, she is one of
+the most brilliant and beautiful of all the planets.<span class="pagenum" id="Page_51">[Pg 51]</span>
+Her speed is three miles a second faster than ours,
+and her distance from the sun is about two-thirds that
+of our own; so that the orbit of Venus lies half-way
+between the orbit of Mercury and the orbit
+of the earth. The day of Venus is about half an
+hour shorter than ours. Her year is nearly two hundred
+and twenty-five days, or seven and a half of our
+months. One or two astronomers have fancied that
+they caught glimpses of a moon near Venus; but this
+is still quite doubtful, and indeed it is believed to have
+been a mistake.</p>
+
+<p>Venus and Mercury are only visible as morning
+and evening planets. Venus, being farther from the
+sun, does not go before and follow after him quite so
+closely as Mercury, and she is therefore the longer
+within sight.</p>
+
+<p>When Venus, traveling on her orbit, comes just
+between the sun and us, her dark side is turned towards
+the earth, and we can catch no glimpse of her.
+When she reaches that part of her orbit which is
+farthest from us, quite on the other side of the sun,
+her great distance from us makes her light seem less.
+But about half-way round on either side, she shows
+exceeding brilliancy, and that is the best view we can
+get of her.</p>
+
+<p>Seen through a telescope, Venus undergoes phases
+like those of Mercury, or of our moon. That is to
+say, we really have “new Venus,” “quarter Venus,”
+“half Venus,” “full Venus,” and so on.</p>
+
+<p>Of all the luminaries in the heavens, the sun and
+moon excepted, the planet Venus is the most conspicuous
+and splendid. She appears like a brilliant lamp<span class="pagenum" id="Page_52">[Pg 52]</span>
+amid the lesser orbs of night, and alternately anticipates
+the morning dawn, and ushers in the evening
+twilight. When she is to the westward of the sun, in
+winter, she cheers our mornings with her vivid light,
+and is a prelude to the near approach of the break of
+day and the rising sun. When she is eastward of that
+luminary, her light bursts upon us after sunset, before
+any of the other radiant orbs of heaven make their
+appearance; and she discharges, in some measure, the
+functions of the absent moon. The brilliancy of this
+planet has been noticed in all ages, and has been frequently
+the subject of description and admiration both
+by shepherds and by poets. The Greek poets distinguished
+it by the name of Phosphor, “light-bringer,”
+when it rose before the sun, and Hesperus, “the west,”
+when it appeared in the evening after the sun retired.
+It is now generally distinguished by the name of the
+Morning and Evening Star.</p>
+
+<p>Next to the orbit of Venus comes the orbit of our
+own Earth, the third planet of the first group.</p>
+
+<p>Mars, the fourth of the inner quartet, but the first
+of the superior planets, is a good deal smaller than
+Venus or the earth. The name Mars, from the heathen
+god of war, was given on account of his fiery reddish
+color. Mars is better placed than Venus for being
+observed from earth. When he is at the nearest point
+of his orbit to us, we see him full in the blaze of sunlight;
+whereas Venus, at her nearest point, turns her
+bright face away.</p>
+
+<p>The length of the day of Mars—or, in other words,
+the time he takes to turn upon his axis—is only forty
+minutes longer than that of earth. Mars’ journey<span class="pagenum" id="Page_53">[Pg 53]</span>
+round the sun is completed in the course of six hundred
+and eighty-seven days, not much less than two
+of our years. His distance from the sun is about one
+hundred and forty millions of miles, and his speed is
+fourteen miles a second. We shall find, with the increasing
+distance of each planet, that the slower pace
+balances the lessened amount of the sun’s attraction.</p>
+
+<p>Passing on from Mars, the last of the first group of
+planets, we reach the belt of Asteroids, sometimes
+called Planetoids, Minor Planets, or Telescopic Planets.
+They are so tiny that Mercury is a giant compared
+with the largest among them.</p>
+
+<p>The zone of space containing all these little planets
+is more than a hundred millions of miles broad. Their
+orbits do not lie flat in almost the same plane, but
+slant about variously in a very entangled fashion. If
+a neat model were made of this zone, with a slender
+piece of wire to represent each orbit, it would be
+found impossible to lift up one wire without pulling
+up all the rest with it. Those asteroids lying nearest
+to the sun take about three of our years to travel
+round him, and those lying farthest take about six of
+our years.</p>
+
+<p>New members of the group are very often found.
+The number of asteroids now known amounts to
+about three hundred and twenty. Ceres is estimated
+by Professor Barnard, of the Yerkes Observatory, Chicago
+University, to be six hundred miles in diameter.
+Vesta is about two hundred and fifty miles in diameter.
+Meta, on the other hand, is less than seventy-five
+miles. There are some smaller ones that do not
+measure twenty miles in diameter, and it is probable<span class="pagenum" id="Page_54">[Pg 54]</span>
+that there are many which are so small as to be absolutely
+invisible to the best telescopes, and which
+measure only a few hundred rods in diameter. Twenty
+thousand Vestas would be needed to make one globe
+equal to our earth in size.</p>
+
+<p>Are they <i>worlds</i>? Why not? Is not a drop of
+water, shown in the microscope, peopled with a multitude
+of various beings? Does not a stone in a
+meadow hide a world of swarming insects? Is not
+the leaf of a plant a world for the species which inhabit
+and prey upon it? Doubtless among the multitude
+of small planets there are those which must
+remain desert and sterile, because the conditions of
+life (of any kind) are not found united. But we can
+not doubt that on the majority the ever-active forces
+of nature have produced, as in our world, creations
+appropriate to these minute planets. Let us repeat,
+moreover, that for nature there is neither great nor
+little. And there is no necessity to flatter ourselves
+with a supreme disdain for these little worlds; for in
+reality the inhabitants of Jupiter would have more
+right to despise us than we have to despise Vesta,
+Ceres, Pallas, or Juno. The disparity is greater between
+Jupiter and the earth than between the earth
+and these planets. A world of two, three, or four
+hundred miles in diameter is still a continent worthy
+to satisfy the ambition of a Xerxes or a Tamerlane.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_55">[Pg 55]</span></p>
+
+<h2 class="nobreak" id="c5">CHAPTER V.</h2>
+</div>
+
+<p class="c sp">THE LEADING MEMBERS OF OUR FAMILY—SECOND<br>
+GROUP.</p>
+
+
+<p><span class="smcap large">Leaving</span> behind us the busy zone of planetoids,
+hurrying round and round the sun in company, we
+cross a wide gap, and come upon a very different
+sight.</p>
+
+<p>The distance from the sun which we have now
+reached is little less than four hundred and fifty millions
+of miles, or about five times as much as the
+earth’s distance; and the sun in the heavens shows a
+diameter only one-fifth of that which we are accustomed
+to see. Slowly—yet not slowly—floating onwards
+through space, in his far-off orbit, we find the
+magnificent planet Jupiter.</p>
+
+<p>Is eight miles each second slow progress? Compared
+with the wild whirl of little Mercury, or even
+compared with the rate of our own earth’s advance,
+we may count it so; but certainly not, compared with
+our notions of speed upon earth. Eight miles each
+second is five hundred times as fast as the swiftest express-train
+ever made by man. No mean pace that
+for so enormous a body. For Jupiter is the very
+largest of all the members of the Solar System except
+the sun himself—quite the eldest brother of the family.
+His diameter is about eighty-five thousand miles,
+his axis being nearly eleven times as long as that of
+earth. Though in proportion to his great bulk not<span class="pagenum" id="Page_56">[Pg 56]</span>
+nearly so heavy as our earth, yet his bulk is so vast
+that more than twelve hundred earths would be needed
+to make one Jupiter.</p>
+
+<p>It must not, however, be forgotten that there is a
+certain amount of uncertainty about these measurements
+of Jupiter. He seems to be so covered with a
+dense atmosphere and heavy clouds that it is quite
+impossible for us to learn the exact size of the solid
+body within.</p>
+
+<p>Jupiter does not travel alone. Borne onwards with
+him, and circling steadily around him, are five moons;
+the smallest with a probable diameter of about one hundred
+miles; one about the same size as our own moon,
+and the others all larger. The nearest of the five,
+though distant from the center of the planet over one
+hundred and twelve thousand miles, revolves about
+him in twelve hours; the second, though farther from
+Jupiter than our moon from the earth, speeds round
+him in less than two of our days. The most distant,
+though over a million miles away, takes scarcely seventeen
+days to accomplish its long journey. Jupiter and
+his moons make a little system by themselves—a
+family circle within a family circle.</p>
+
+<p>Like the smaller planets, Jupiter spins upon his
+axis; and he does this so rapidly that, notwithstanding
+his great size, his day lasts only ten hours, instead of
+twenty-four hours like ours. But if Jupiter’s day is
+short, his year is not. Nearly twelve of our years pass
+by before Jupiter has traveled once completely round
+the sun. So a native of earth who had just reached
+his thirty-seventh year, would, on Jupiter, be only
+three years old.</p>
+
+<p><span class="pagenum" id="Page_57">[Pg 57]</span></p>
+
+<p>Passing onward from Jupiter, ever farther and
+farther from the sun, we leave behind us another vast
+and empty space—empty as we count emptiness,
+though it may be that there is in reality no such thing
+as emptiness throughout the length and breadth of
+the universe. The width of the gap which divides
+the pathway of Jupiter from the pathway of his giant
+brother-planet Saturn is nearly five times as much as
+the width of the gap separating the earth from the
+sun. The distance of Saturn from the sun is not
+much less than double the distance of Jupiter.</p>
+
+<p>With this great space in our rear, we come upon
+another large and radiant planet, the center, like Jupiter,
+of another little system; though it can only be
+called “little” in comparison with the much greater
+Solar System of which it forms a part.</p>
+
+<p>Saturn’s diameter is less than that of Jupiter, but
+the two come near enough to be naturally ranked together.
+Nearly seven hundred earths would be needed
+to make one globe as large as Saturn. But here again
+the dense and cloudy envelope makes us very uncertain
+about the planet’s actual size. Saturn is like Jupiter
+in being made of lighter materials than our earth;
+and also in his rapid whirl upon his axis, the length
+of his “day” being only ten and a half of our hours.</p>
+
+<p>From Jupiter’s speed of eight miles each second,
+we come down in the case of Saturn to only five miles
+each second. And Jupiter’s long annual journey looks
+almost short, seen beside Saturn’s long journey of
+thirty earthly years. A man aged sixty, according to
+our fashion of reckoning time, would on Saturn have
+just kept his second birthday.</p>
+
+<p><span class="pagenum" id="Page_58">[Pg 58]</span></p>
+
+<p>The system or family of Saturn is yet more wonderful
+than that of Jupiter. Not five only but eight
+moons travel ceaselessly round Saturn, each in its own
+orbit; and in addition to the eight moons, he has
+revolving round him three magnificent rings. These
+rings, as well as the moons, shine, not by their own
+brilliancy, for they have none, but by borrowed sunlight.
+The farthest of the moons wanders in his
+lonely pathway about two millions of miles away from
+Saturn. The largest of them is believed to be about
+the same size as the planet Mars. Of the three rings
+circling round Saturn, almost exactly over his equator,
+the inside one is dusky, purplish, and transparent; the
+one outside or over that is very brilliant; and the
+third, outside the second, is rather grayish in hue.</p>
+
+<p>Another vast gap—more enormous than the last.
+It is a wearisome journey. From the orbit of Jupiter
+to the orbit of Saturn at their nearest points, was five
+times as much as from the sun to the earth. But from
+the orbit of Saturn to the orbit of Uranus, the next
+member of the sun’s family, we have double even that
+great space to cross.</p>
+
+<p>Still, obedient to the pulling of the sun’s attractive
+power, Uranus wanders onward in his wide pathway
+round the sun, at the rate of four miles a second.
+Eighty-four of our years make one year of Uranus.
+This planet has four moons, and thus forms a third
+smaller system within the Solar System; but he may
+have other satellites also, as yet undiscovered. In size
+he is seventy-four times as large as our earth.</p>
+
+<p>One more mighty chasm of nine hundred millions
+of miles, for the same distance which separates the<span class="pagenum" id="Page_59">[Pg 59]</span>
+pathway of Saturn from the pathway of Uranus, separates
+also the pathway of Uranus from the pathway
+of Neptune. Cold, and dark, and dreary indeed seems
+to us the orbit on which this banished member of our
+family circle creeps round the sun, in the course of one
+hundred and sixty-five years, at the sluggish rate of
+three miles a second.</p>
+
+<p>On the planet Saturn, the quantity of light and
+heat received from the sun is not much more than a
+hundredth part of that which we are accustomed to
+receive on earth. But by the time we reach Neptune,
+the great sun has faded and shrunk in the distance
+until to our eyes he looks only like an exceedingly
+brilliant and dazzling star.</p>
+
+<p>We know little of this far-off brother, Neptune,
+except that he is rather larger than Uranus, being one
+hundred and five times as big as the earth; that he has
+at least one moon; and also that, like Uranus, he is
+made of materials lighter than those of earth, but
+heavier than those of Jupiter or Saturn.</p>
+
+<p>After all, it is no easy matter to gain clear ideas as
+to sizes and distances from mere statements of “so
+many miles in diameter,” and “so many millions of
+miles away.” A “million miles” carries to the mind
+a very dim notion of the actual reality.</p>
+
+<p>Now if we can in imagination bring down all the
+members of the Solar System to a small size, keeping
+always the same proportions, we may find it a help.
+“Keeping the same proportions” means that all must
+be lessened alike, all must be altered in the same
+degree. Whatever the supposed size of the earth may
+be, Venus must be still about the same size as the<span class="pagenum" id="Page_60">[Pg 60]</span>
+earth, Saturn seven hundred times as large, and so on.
+Also, whatever the distance of the earth from the sun,
+in miles, or yards, or inches, Mercury must still be one-third
+as far, Jupiter still five times as far, and thus
+with the rest.</p>
+
+<p>First, as to size alone. Suppose the earth is represented
+by a small globe, exactly three inches in diameter.
+It will be a very small globe. Not only men
+and houses, but mountains, valleys, seas, will all have
+to be reduced to so minute a size, as to be quite invisible
+to the naked eye.</p>
+
+<p>Fairly to picture the other members of the Solar
+System, in due proportion, you will have them as
+follows:</p>
+
+<p>Mercury and Mars will be balls smaller than the
+earth, and Venus nearly the same size of the earth.
+Uranus and Neptune will be each somewhere about a
+foot in diameter. Saturn will be twenty-eight inches
+and Jupiter thirty-two inches in diameter. The sun
+will be a huge dazzling globe, <i>twenty-six feet</i> in diameter.
+No wonder he weighs seven hundred and
+fifty times as much as all his planets put together.</p>
+
+<p>Next let us picture the system more exactly on
+another and smaller scale. First, think of the sun as
+a brilliant globe, about nine feet, or three yards, in
+diameter, floating in space.</p>
+
+<p>About one hundred yards from the sun travels a
+tiny ball, not half an inch in diameter, passing slowly
+round the sun—slowly, because as sizes and distances
+are lessened, speed must in due proportion be lessened
+also. This is Mercury. About two hundred yards
+from the sun travels another tiny ball, one inch in diameter.<span class="pagenum" id="Page_61">[Pg 61]</span>
+This is Venus. Nearly a quarter of a mile
+from the sun travels a third tiny ball, one inch again
+in diameter; and at a distance of two feet and a half
+from it a still smaller ball, one quarter of an inch in
+diameter, journeys round it and with it. These are
+the earth and the moon. About half as far again as
+the last-named ball, travels another, over half an inch
+in diameter. This is Mars.</p>
+
+<p>Then comes a wide blank space, followed by a large
+number of minute objects, no bigger than grains of
+powder, floating round the sun in company. These
+are the Asteroids. Another wide blank space succeeds
+the outermost of them.</p>
+
+<p>About one mile distant from the sun journeys a
+globe, ten inches in diameter. Round him, as he
+journeys, there travel five smaller balls, the largest of
+which is about the third of an inch in diameter. Their
+distances from the bigger globe vary from one and a
+third to twelve and a half feet. These are Jupiter and
+his moons.</p>
+
+<p>Nearly two miles distant from the sun journeys
+another globe, about eight and a half inches in diameter.
+Eight tiny balls and three delicate rings circle
+round him as he moves. These are Saturn and his
+belongings. About four miles distant from the sun
+journeys another globe, four inches in diameter, with
+four tiny balls accompanying him—Uranus and his
+moons. Lastly, at a distance of six miles from the
+sun, one more globe, not much larger than the last,
+with one tiny companion, pursues his far-off pathway.</p>
+
+<p>These proportions as to size and distance will serve
+to give a clear idea of the Solar System.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_62">[Pg 62]</span></p>
+
+<h2 class="nobreak" id="c6">CHAPTER VI.</h2>
+</div>
+
+<p class="c sp">THE MOON.</p>
+
+
+<p><span class="smcap large">Come</span>, and let us pay a visit to the moon. We
+seem to feel a personal interest in her, just because
+she is, in so peculiar a sense, our own friend and close
+attendant. The sun shines for us; but, then, he shines
+for all the members of the Solar System. And the
+stars—so many as we can see of them—shine for us
+too; but no doubt they shine far more brilliantly for
+other and nearer worlds. The moon alone seems to
+belong especially to ourselves.</p>
+
+<p>Indeed, we are quite in the habit of speaking about
+her as “our moon.” Rather a cold and calm friend,
+some may think her, sailing always serenely past,
+whatever may be going on beneath her beams; yet
+she has certainly proved herself constant and faithful
+in her attachment.</p>
+
+<p>We have not very far to travel before reaching her,—merely
+about two hundred and forty thousand miles.
+That is nothing, compared with the weary millions of
+miles which we have had to cross to visit some members
+of our family. A rope two hundred and forty
+thousand miles long would fold nearly ten times round
+the earth at the equator. You know the earth’s diameter—about
+eight thousand miles. If you had
+thirty poles, each eight thousand miles long, and
+could fasten them all together, end to end, one beyond
+another, you would have a rod long enough to reach
+from the earth to the moon.</p>
+
+<p><span class="pagenum" id="Page_63">[Pg 63]</span></p>
+
+<p>Let us take a good look at her before starting. She
+is very beautiful. That soft silvery light, so unlike
+sunlight or gaslight, or any other kind of light seen
+upon earth, has made her the darling of poets and
+the delight of all who love nature. Little children
+like to watch her curious markings, and to make out
+the old man with his bundle of sticks, or the eyes,
+nose, and mouth of the moon—not dreaming what
+those markings really are. And in moods of sadness,
+how the pure calm moonlight seems to soothe the
+feelings! Who would suppose that the moon’s beauty
+is the beauty rather of death than of life?</p>
+
+<div class="figcenter" id="f8">
+<img src="images/fig8.jpg" alt="moon">
+<p class="caption">APPEARANCE OF THE FULL MOON.</p>
+</div>
+
+<p>The stars have not much chance of shining through
+her bright rays. It is well for astronomers that she is
+not always at the full. But when she is, how large
+she looks—quite as large as the sun, though in reality<span class="pagenum" id="Page_64">[Pg 64]</span>
+her size, compared with his, is only as a very small
+pin’s head compared with a school globe two feet in
+diameter. Her diameter is little more than two thousand
+miles, or one quarter that of our earth; and her
+whole surface, spread out flat, would scarcely equal
+North and South America, without any of the surrounding
+islands.</p>
+
+<p>The reason she looks the same size as the sun, is
+that she is so very much nearer. The sun’s distance
+from us is more than one-third as many <i>millions</i> of
+miles as the moon’s distance is <i>thousands</i> of miles.
+This makes an enormous difference.</p>
+
+<p>We call our friend a “moon,” and say that she
+journeys round the earth, while the earth journeys
+round the sun. This is true, but it is only part of the
+truth. Just as certainly as the earth travels round
+the sun, so the moon also travels round the sun. And
+just as surely as the earth is a planet, so the moon also
+is a planet. It is a common mode of expression to
+talk about “the earth and her satellite.” A no less
+correct, if not more correct, way would be to talk of
+ourselves as “a pair of planets,” journeying round the
+same sun, each pulled strongly towards him, and each
+pulling the other with a greater or less attraction, according
+to her size and weight. For the sun actually
+does draw the moon with more force than that with
+which the earth draws her. Only as he draws the
+earth with the same sort of force, and nearly in the
+same degree, he does not pull them apart.</p>
+
+<p>The moon, like the other planets, turns upon her
+axis. She does this very slowly, however; and most
+singularly she takes exactly the same time to turn<span class="pagenum" id="Page_65">[Pg 65]</span>
+once upon her axis that she does to travel once round
+the earth. The result of this is, that we only see one
+face of the moon. If she turned upon her axis,
+and journeyed round the earth in two different lengths
+of time, or if she journeyed round us and did not turn
+upon her axis at all, we should have views of her on
+all sides, as of other planets. But as her two movements
+so curiously agree, it happens that we always
+have one side of the moon towards us, and never catch
+a glimpse of the other side.</p>
+
+<p>And now we are ready to start on our journey of
+two hundred and forty thousand miles. An express
+train, moving ceaselessly onward night and day, at the
+rate of sixty miles an hour, would take us there in
+about five months and a half. But no line of rails has
+ever yet been laid from the earth to the moon, and no
+“Flying Dutchman” has ever yet plied its way to and
+fro on that path through the heavens. Not on the
+wings of steam, but on the wings of imagination, we
+must rise aloft. Come—it will not take us long. We
+shall pass no planets or stars on the road, for the moon
+lies nearer to us than any other of the larger heavenly
+bodies.</p>
+
+<p>Far, far behind us lies the earth, and beneath our
+feet, as we descend, stretch the broad tracts of moonland.
+For “downward” now means towards the
+moon, and away from the distant earth.</p>
+
+<p>What a strange place we have reached! The weird,
+ghastly stillness of all around, and the glaring, dazzling,
+cloudless heat, strike us first and most forcibly.
+Nothing like this heat have we ever felt on earth. For
+the close of the moon’s long day—on this side of its<span class="pagenum" id="Page_66">[Pg 66]</span>
+globe—is approaching, and during a whole fortnight
+past the sun’s fierce rays have been beating down on
+these shelterless plains. Talk of sweltering tropics on
+earth! What do you call <i>this</i> heat? Look at the
+thermometer: how the quicksilver is rising! Well, that
+is not a common thermometer which we have brought
+with us. The mercury has stopped—three hundred
+degrees above boiling water!</p>
+
+<p>Not a cloud to be seen overhead; only a sky of inky
+blackness, with a blazing sun, and thousands of brilliant
+stars, and the dark body of our own earth, large
+and motionless, and rimmed with light. Seen from
+earth, sun and moon look much the same size; but
+seen from the moon, the earth looks thirteen times as
+large as our full moon. Not even a little mistiness in
+the air to soften this fearful glare! Air! why, there
+is no air; at least not enough for any human being to
+breathe or feel. If there were air, the sky would be
+blue, not black, and the stars would be invisible in
+the daytime. It looks strange to see them now shining
+beside the sun.</p>
+
+<p>And then, this deadly stillness! Not a sound, not
+a voice, not a murmur of breeze or water. How could
+there be? Sound can not be carried without air, and
+of air there is none. As for breeze—wind is moving
+air, and where we have no air we can have no wind.
+As for water—if there ever was any water on the
+moon, it has entirely disappeared. We shall walk to
+and fro vainly in search of it now. No rivers, no rills,
+no torrents in those stern mountain ramparts rising on
+every side. All is craggy, motionless, desolate.</p>
+
+<p>How very, very slowly the sun creeps over the black<span class="pagenum" id="Page_67">[Pg 67]</span>
+sky! And no marvel, since a fortnight of earth-time
+is here but one day, answering to twelve hours upon
+earth. Can not we find shelter somewhere from this
+blazing heat? Yonder tall rock will do, casting a sharp
+shadow of intense blackness. We never saw such
+shadows upon earth. There the atmosphere so breaks
+and bends and scatters about the light, that outlines
+of shadows are soft and hazy, even the clearest and
+darkest of them, compared with this.</p>
+
+<p>When will the sun go down? But he is well worth
+looking at meanwhile. How magnificent he appears,
+with his pure radiant photosphere, fringed by a sierra
+of dazzling pink and white, orange and gold, purple
+and blue. For here no atmosphere lies between to
+blend all into yellow-white brightness. And how
+plainly stand out those prominences or tongues of
+tinted flame, not merely rose-colored, as seen from
+earth, but matching the sierra in varying hues; while
+beyond spreads a gorgeous belt of pink and green,
+bounded by lines and streams of delicate white light,
+reaching far and dying slowly out against the jet background.
+The black spots on the face of the sun are
+very distinct, and so also are the brilliant faculæ.</p>
+
+<p>We must take a look around us now at moonland,
+and not only sit gazing at the sun, though such a sky
+may well enchain attention. How unlike our earthly
+landscapes! No sea, no rivers, no lakes, no streams,
+no brooks, no trees, bushes, plants, grass, or flowers;
+no wind or breeze; no cloud or mist or thought of possible
+rain; no sound of bird or insect, of rustling
+leaves or trickling water. Nothing but burning, steadfast,
+changeless glare, contrasting with inky shadows;<span class="pagenum" id="Page_68">[Pg 68]</span>
+sun and earth and stars in a black heaven above;
+silent, desolate mountains and plains below.</p>
+
+<p>For though we stand here upon a rough plain, this
+moon is a mountainous world. Ranges of rugged
+hills stretch away in the distance, with valleys lying
+between—not soft, green, sloping, earthly valleys, but
+steep gorges and precipitous hollows, all white dazzle
+and deep shade.</p>
+
+<p>But the mountains do not commonly lie in long
+ranges, as on earth. The surface of the moon seems
+to be dented with strange round pits, or craters, of
+every imaginable size. We had a bird’s-eye view of
+them as we descended at the end of our long journey
+moonward. In many parts the ground appears to be
+quite honeycombed with them. Here are small ones
+near at hand, and larger ones in the distance. The
+smaller craters are surrounded by steep ramparts of
+rock, the larger ones by circular mountain-ranges. We
+have nothing quite like them on earth.</p>
+
+<p>Are they volcanoes? So it would seem; only no
+life, no fire, no action, remain now. All is dead,
+motionless, still. Is this verily a blasted world? Has
+it fallen under the breath of Almighty wrath, coming
+out scorched and seared? Is it simply passing
+through a certain burnt-out, chilled phase of existence,
+through which other planets also pass, or will pass, at
+some stage of their career? Who can tell?</p>
+
+<p>We will move onward, and look more closely at
+that towering mass of rugged rocks, beyond which the
+sun will by and by go down. Long jetty shadows lie
+from them in this direction. No wonder astronomers
+on earth can through their telescopes plainly see these<span class="pagenum" id="Page_69">[Pg 69]</span>
+black shadows contrasting with the glaring brightness
+on the other side.</p>
+
+<p>A “mass of rocks” I have said; but as, with our
+powers of rapid movement, we draw near, we find a
+range of craggy mountains sweeping round in a vast
+circle. Such a height in Switzerland would demand
+many hours of hard climbing. But on this small
+globe attraction
+is a very different
+matter from
+what it is on
+earth; our weight
+is so lessened
+that we can leap
+the height of a
+tall house without
+the smallest
+difficulty. No
+chamois ever
+sprang from
+peak to peak in
+his native Switzerland with such amazing lightness as
+that with which we now ascend these mighty rocks.</p>
+
+<div class="figright" id="f9">
+<img src="images/fig9.jpg" alt="crater">
+<p class="caption">ONE FORM OF LUNAR CRATER.</p>
+</div>
+
+<p>Ha! what a depth on the other side! We stand
+looking down into one of the monster craters of the
+moon. A sheer descent of at least eleven thousand
+feet would land us at the bottom. Why, Mont Blanc
+itself is only about fifteen thousand feet in height.
+And what a crater! Fifty-six miles across in a straight
+line, from here to the other side, with these lofty
+rugged battlements circling round, while from the
+center of the rough plain below a sharp, cone-shaped<span class="pagenum" id="Page_70">[Pg 70]</span>
+mountain rises to about a quarter of the height of the
+surrounding range.</p>
+
+<p>It is a grand sight; peak piled upon peak, crag upon
+crag, sharp rifts or valleys breaking here and there the
+line of the narrow, uplifted ledge; all wrapped in silent
+and desolate calm. There are many such craters as
+this on the moon, and some much larger.</p>
+
+<p>The sun slowly nears his setting, and sinks behind
+the opposite range. How we shiver! The last ray of
+sunlight has gone and already the ground is pouring
+out its heat into space, unchecked by the presence of
+air or clouds. The change takes place with marvelous
+quickness. A deadly chill creeps over all around. A
+whole fortnight of earth-time must pass before the
+sun’s rays will again touch this spot. Verily the contrasts
+of climate in the moon, during the twelve long
+days and nights which make up her year, are startling
+to human notions.</p>
+
+<p>But though the sun is gone we are not in darkness.
+The stars shine with dazzling brightness, and the huge
+body of the earth, always seeming to hang motionless
+at one fixed point in the sky, gives brilliant light,
+though at present only half her face is lit up and half
+is in shadow. Still her shape is plainly to be seen,
+for she has ever round her a ring of light, caused by
+the gathered shining of stars as they pass behind her
+thick atmosphere. She covers a space on the sky
+more than a dozen times as large as that covered by
+the full moon in our sky.</p>
+
+<div class="figcenter" id="f10">
+<img src="images/fig10.jpg" alt="earth">
+<p class="caption">THE EARTH AS SEEN FROM THE MOON.</p>
+</div>
+
+<p>It would be worth while to stay here and watch the
+half-earth grow into magnificent full-earth. But the
+cold is becoming fearful—too intense for even the
+<span class="pagenum" id="Page_72">[Pg 72]</span>imagination to endure longer. What must be the state
+of things on the other side of the moon, where there
+is no bright earth-light to take the place of the sun’s
+shining, during the long two weeks’ night of awful
+chill and darkness?</p>
+
+<p>It seems probable that a building on the moon
+would remain for century after century just as it was
+left by the builders. There need be no glass in the
+windows, for there is no wind and no rain to keep
+out. There need not be fireplaces in the rooms, for
+fuel can not burn without air. Dwellers in a city in
+the moon would find that no dust can rise, no odors
+be perceived, no sounds be heard. Man is a creature
+adapted for life in circumstances which are very narrowly
+limited. A few degrees of temperature, more
+or less; a slight variation in the composition of air,
+the precise suitability of food, make all the difference
+between health and sickness, between life and death.
+Looking beyond the moon, into the length and breadth
+of the universe, we find countless celestial globes, with
+every conceivable variety of temperature and of constitution.
+Amid this vast number of worlds with
+which space teems, are there any inhabited by living
+beings? To this great question science can make no
+response save this: We can not tell.</p>
+
+<p>Time for us to wend our way homewards from this
+desolate hundred-fold arctic scene. We have more to
+learn by and by about our friend and companion.
+For the present—enough.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_73">[Pg 73]</span></p>
+
+<h2 class="nobreak" id="c7">CHAPTER VII.</h2>
+</div>
+
+<p class="c sp">VISITORS.</p>
+
+
+<p><span class="smcap large">We</span> come next to the very largest members of our
+Solar System.</p>
+
+<p>From time to time in past days—and days not
+very long past either—people were startled by the
+sight of a long-tailed star, moving quickly across the
+sky, called a comet. We see such long-tailed stars
+still, now and then; but their appearance no longer
+startles us.</p>
+
+<p>It is hardly surprising, however, that fears were
+once felt. The great size and brilliancy of some of
+these comets naturally caused large ideas to be held
+as to their weight, and the general uncertainty about
+their movements naturally added to the mysterious
+notions afloat with respect to their power of doing
+harm.</p>
+
+<p>A collision between the earth and a comet seemed
+no unlikely event; and if it happened—what then?
+Why, then, of course, the earth would be overpowered,
+crushed, burnt up, destroyed. So convinced were
+many on this point that the sight of a comet and the
+dread of the coming “end of the world” were fast
+bound together in their minds.</p>
+
+<p>Even when astronomers began to understand the
+paths of some of the comets, and to foretell their return
+at certain dates, the old fear was not quickly laid
+to rest. So late as the beginning of the present century,<span class="pagenum" id="Page_74">[Pg 74]</span>
+astronomers having told of an approaching
+comet, other people added the tidings of an approaching
+collision. “If a collision, then the end of the
+world,” was the cry; and one worthy family, living
+and keeping a shop in a well-known town on the
+south coast of England, packed up and fled to America—doubtless
+under full belief that the destruction
+of the Old World would not include the destruction
+of the New.</p>
+
+<p>The nature of these singular bodies is somewhat
+better known in the present day; yet even now, among
+all the members of the Solar System, they are perhaps
+the ones about which we have most to learn. The
+nucleus, or bright and star-like spot, which, with the
+surrounding coma or “hair,” we sometimes call the
+“head” of the comet, is the densest and heaviest part
+of the whole. The comets are of immense size, sometimes
+actually filling more space than the sun himself,
+and their tails stream often for millions of miles
+behind them; nevertheless, they appear to be among
+the lightest of the members of the Solar System.</p>
+
+<p>This excessive lightness greatly lessens the comet’s
+power of harm-doing. In the rebound from all the
+old exaggerated fears, men laughed at the notion of
+so light and delicate a substance working any injury
+whatever, and even declared that a collision might
+take place without people on earth being aware of
+the fact. It is now felt that we really know too little
+about the nature of the said substance to be able to
+say what might or might not be the result of a collision.
+A certain amount of injury to the surface of
+the earth might possibly take place. But of the<span class="pagenum" id="Page_75">[Pg 75]</span>
+“end of the world,” as likely to be brought about
+by any comet in existence, we may safely banish
+all idea.</p>
+
+<p>The word “comet” means “a hairy body,” the
+name having been given from the hairy appearance
+of the light around the nucleus. About seventeen
+hundred different comets have been seen at different
+times by men—some large, some small; some visible
+to the naked eye, but most of them only visible through
+telescopes. These hundreds are, there is no doubt, but
+a very small number out of the myriads ranging through
+the heavens.</p>
+
+<p>If you were seated in a little boat in mid-ocean,
+counting the number of fishes which in one hour
+passed near enough in the clear water for your sight
+to reach them, you might fairly conclude, even if you
+did not know the fact, that for every single fish which
+you could see, there were tens of thousands which you
+could not see.</p>
+
+<p>Reasoning thus about the comets, as we watch
+them from our earth-boat in the ocean of space, we
+feel little doubt that for each one which we can see,
+millions pass to and fro beyond reach of our vision.
+Indeed, so long ago as the days of Kepler, that great
+astronomer gave it as his belief that the comets in
+the Solar System, large and small, were as plentiful
+as the fishes in the sea. And all that modern astronomers
+can discover only tends to strengthen this
+view.</p>
+
+<p>Why should the comets be called “visitors?” I
+call them so simply because many of them <i>are</i> visitors.
+Some, it is true, belong to the Solar System. But<span class="pagenum" id="Page_76">[Pg 76]</span>
+even in their case, strong doubts are felt whether they
+were not once visitors from a distance, caught in the
+first instance by the attraction of one of the larger
+planets, and retained thenceforward, for a time at least,
+by the strong attraction of the sun.</p>
+
+<div class="figcenter" id="f11">
+<img src="images/fig11.jpg" alt="tail">
+<p class="caption">PASSAGE OF THE EARTH AND THE MOON THROUGH THE TAIL OF A<br>
+COMET.</p>
+</div>
+
+<p>Every comet, like every planet, has his own orbit
+or pathway in the heavens, though the kind of orbit
+varies with different comets. There are, first, those
+comets which travel round and round the sun in
+“closed orbits”—that is, in a ring with joined ends.
+Only the ring is always oval, not round. There are,
+secondly, those which travel in an orbit which <i>may</i> be
+closed; but if so, the oval is so long and narrow, and
+the farther closed end is at so great a distance, that
+we can not speak certainly. There are, thirdly, those
+which decidedly are mere visitors. They come from
+the far-off star-depths, flash once with their brilliant
+trains of light through our busy Solar System, causing<span class="pagenum" id="Page_77">[Pg 77]</span>
+some little excitement by the way, and go off in another
+direction, never to return.</p>
+
+<p>Only a small part of the orbits of these comets can
+be seen from earth; but by careful attention astronomers
+learn something of the shape of the curve in
+which they travel. It is in that way possible to calculate,
+sometimes certainly, and sometimes uncertainly,
+whether a comet may be expected to return, or
+whether we have seen him for the first and the last
+time. By looking at <i>part</i> of a curve, the rest of
+which is hidden from us, we are able to judge
+whether that part belongs to a circle or an oval, or
+whether the two ends pass away in different directions,
+and do not join.</p>
+
+<p>The comets, whether members of our family circle
+or visitors from a distance, are altogether very perplexing.
+They are often extremely large, yet they are always
+extremely light. They reflect the sun’s brightness
+like a planet, yet in some measure they seem to
+shine by their own light, like a star. They obey the
+attraction of the sun, yet he appears to have a singular
+power of driving the comets’ tails away from
+himself.</p>
+
+<p>For, however rapidly the comet may be rushing
+round the sun, and however long the tail may be, it is
+almost always found to stream in an opposite direction
+from the sun. An exception to this rule was seen in
+the case of a certain comet with two tails, one of
+which did actually point towards the sun; but the inner
+tail may have been only a “jet” of unusual length,
+like in kind to the smaller jets often thus poured out
+from the nucleus.</p>
+
+<p><span class="pagenum" id="Page_78">[Pg 78]</span></p>
+
+<p>Very curious changes take place in comets as they
+journey, especially as they come near the sun. One
+was seen in the course of a few days to lose all his
+hair, and also his tail. Another was seen to break
+into two pieces, both of which pieces at last disappeared.
+Sometimes the one tail divides into two tails.</p>
+
+<p>Traveling, as the comets do, from intense cold into
+burning heat, they are very much affected by the violent
+change of climate. For the paths of the comets
+are such long ovals, or ellipses, that, while they approach
+the sun very closely in one part of their “year,”
+they travel to enormous distances in the other part.</p>
+
+<p>“Halley’s Comet,” which takes seventy-six of our
+years to journey round the sun, comes nearer to him
+than Venus, and goes farther away from him than
+Neptune. As this comet draws gradually closer, he
+has to make up for the added pull of the sun’s increasing
+attraction by rushing onward with greater
+and greater rapidity, till he whirls madly past the sun,
+and then, with slowly slackening speed, journeys farther
+and farther away, creeps at length lazily round
+the farther end of his orbit in the chill, dark, neighborhood
+of Neptune, and once more travels towards
+the sun with growing haste.</p>
+
+<p>“Encke’s Comet” has a year of only three and a
+half of our years, so he may be said to live quite in
+our midst. But many comets travel much farther
+away than the one named after Halley. It is calculated
+of some that, if they ever return at all, it can not
+be for many hundreds of years.</p>
+
+<div class="figcenter" id="f12">
+<img src="images/fig12.jpg" alt="comet">
+<p class="caption">PASSAGE OF THE COMET OF 1843 CLOSE TO THE SUN (FEBRUARY<br>
+27TH, 10 HOURS, 29 MINUTES.)</p>
+</div>
+
+<p>“Newton’s Comet,” seen about two centuries ago,
+has a journey to perform of such length that he is<span class="pagenum" id="Page_79">[Pg 79]</span>
+not expected again to appear for several thousand
+years. Yet, at the nearest point in his orbit, he approached
+the sun so closely, that the heat which he
+endured was about two thousand times that of red-hot
+iron. Changes were seen to be taking place in
+his shape, as he drew near to the sun, and disappeared.
+Four days he was hidden in the sun’s rays. He vanished,
+with a tail streaming millions of miles behind<span class="pagenum" id="Page_80">[Pg 80]</span>
+him. He made his appearance again with a tail
+streaming millions of miles in front of him. But how
+this wonderful movement took place is beyond man’s
+power to explain.</p>
+
+<p>The comet of 1843 was one of the most attractive
+seen during the present century. It was first observed
+in March, and it appeared with a suddenness which had
+quite a startling effect. It was an imposing object in
+the southern regions. The comet was seen in Italy
+on the 28th of February; at Washington, on the 6th
+of March; at Oporto, on the 14th; but owing to unfavorable
+weather, it was not visible in England, or any
+of the northern countries of Europe, previous to the
+17th. A little after sunset on that day the tail was
+observed in the western sky, but the head had already
+sunk below the horizon. The whole of the comet appeared
+on the following evenings for a short time, for
+it was traveling away from the sun with great velocity,
+having doubled the solar orb before it became
+visible; and about the beginning of April it finally
+disappeared.</p>
+
+<p>The appearance of this startling stranger, as observed
+at Washington, is thus described by Lieutenant
+Maury, of the Hydrographical Office in that city:
+“On Monday morning, March 6th, our attention was
+called to a paragraph in the newspapers, stating that
+a comet was visible near the sun at midday with the
+naked eye. The sky was clear; but not being able to
+discover any thing with the unassisted eye, recourse
+was had to the telescope, but with no better success.
+About sunset in the evening, the examination was renewed
+with great diligence, but to no purpose. The<span class="pagenum" id="Page_81">[Pg 81]</span>
+last faint streak of day gilded the west; beautiful
+and delicate fleeces of cloud curtained the bed of
+the sun; the upper sky was studded with stars,
+and all hopes of seeing the comet that evening had
+vanished. Soon after we had retired, the officer of
+the watch announced its appearance in the west. The
+phenomenon was sublime and beautiful. The needle
+was greatly agitated, and a strongly marked pencil of
+light was streaming up from the path of the sun in
+an oblique direction to the southward and eastward;
+its edges were parallel. It was 30° long. Stars
+could be seen twinkling through it, and no doubt
+was at first entertained that this was the tail of the
+comet.”</p>
+
+<p>The tail, as seen in northerly countries, spread over
+an arc of the heavens of about 40°; but in southern
+latitudes it extended to from 60° to 70°. It had an absolute
+length of two hundred millions of miles; so
+that, had it been coiled around the earth like a serpent,
+it would have girdled it eight thousand times at the
+equator. This comet approached still nearer the sun
+than that of Newton, and must therefore have been
+exposed to a heat of greater intensity. Its center is
+computed to have been within a hundred thousand
+miles of the solar surface; and according to Sir John
+Herschel’s calculations, it was then exposed to a heat
+equal to that which would be received by an equal
+portion of the earth’s surface, if it were subject to the
+influence of forty-seven thousand suns, placed at the
+common distance of the actual sun. It is difficult to
+conceive how a flimsy substance in such circumstances
+could escape being entirely dissipated. But such was<span class="pagenum" id="Page_82">[Pg 82]</span>
+its velocity that it wheeled round the sun in less than
+two hours.</p>
+
+<p>The general question of the probability and the
+consequences of a collision with a comet may be legitimately
+entertained. With reference to the first point,
+it can not be denied that collision is possible; but, at
+the same time, it is so extremely improbable that it
+may be safely dismissed from apprehension. The fact
+of such an event not having been experienced in the
+known course of terrestrial history is surely some
+guarantee against its occurrence. Another may be
+found in the small volume of the earth and of comets
+when compared with the immensity of space in which
+they move. According to the well-understood principles
+of probabilities, Arago has calculated that, upon
+the appearance of a new comet, the odds are as 281,000,000
+to 1, that it will not strike against our globe.
+But even supposing collision to occur, all that we
+know of the constitution of comets justifies the conclusion
+that the encounter would involve no terrestrial
+convulsion, nor any result incompatible with full security
+to life and happiness.</p>
+
+<p>So much for the largest members of our circle—largest,
+though lightest; members some, visitors others.
+Now we turn to the smallest.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_83">[Pg 83]</span></p>
+
+<h2 class="nobreak" id="c8">CHAPTER VIII.</h2>
+</div>
+
+<p class="c sp">LITTLE SERVANTS.</p>
+
+
+<p><span class="smcap large">If</span> you walk out any night after dark, and watch
+the bright stars shining in a clear sky—shining as
+they have done for ages past—you will probably see,
+now and then, a bright point of light suddenly appear,
+dart along a little distance, and as suddenly vanish.
+That which you have seen was not the beginning of
+a story, but in ninety-nine cases out of a hundred
+it was the end of a story. The little shooting-star
+was in existence long before you saw him, whirling
+through space with millions of little companions. But
+he has left them all, and dropped to earth. He is a
+shooting-star no longer.</p>
+
+<p>If such a journey to the moon as the one described
+two chapters back were indeed possible, the voyage
+aloft would hardly be so easily and safely performed
+as is there taken for granted. Putting aside the
+thought of other difficulties, such as lack of conveyance
+and lack of air, there would be the danger of
+passing through a very considerable storm of missiles—a
+kind of “celestial cannonade”—which, to say
+the least, would prove very far from agreeable.</p>
+
+<p>These “starlets” and “meteor planets,” as they
+have been called, are not visible in a normal condition,
+because of their minuteness. But on entering our atmosphere
+they are rendered luminous, owing to the
+heat evolved by the sudden and violent compression<span class="pagenum" id="Page_84">[Pg 84]</span>
+of the air in front of the moving body. According to
+this view, shooting-stars, which simply dart across the
+heavens, may be regarded as coming within the limits
+of the atmosphere, and carried out of it again, by their
+immense velocity, passing on in space. Meteoric
+showers may result from an encounter with a group
+of these bodies, while aërolites are those which come
+so far within the sphere of the earth’s attraction as to
+fall to its surface. More than two thousand years ago
+the Greeks venerated a famous stone which fell from
+the heavens on the river Ægos.</p>
+
+<div class="figcenter" id="f13">
+<img src="images/fig13.jpg" alt="meteor">
+<p class="caption">METEOR EMERGING FROM BEHIND A CLOUD (NOV. 23, 1877).</p>
+</div>
+
+<p>It will scarcely be believed what numbers of these
+shooting-stars or meteorites constantly fall to the earth.
+As she travels on her orbit, hurrying along at the rate
+of nineteen miles each second, she meets them by<span class="pagenum" id="Page_85">[Pg 85]</span>
+tens of thousands. They too, like the earth, are journeying
+round the great center of our family. But
+they are so tiny, and the earth by comparison is so
+immense, that her strong attraction overpowers one
+after another, drags it from its pathway, and draws it
+to herself.</p>
+
+<p>And then it falls, flashing like a bright star across
+the sky, and the little meteorite has come to his end.
+His myriads of companions, hastening still along their
+heavenly track—for the meteorites seem to travel commonly
+in vast flocks or companies—might, had they
+sense, mourn in vain for the lost members of their
+family.</p>
+
+<p>Any one taking the trouble to watch carefully some
+portion of the sky after dark, may expect to see each
+hour about four to eight of these shooting-stars—except
+in the months of August and November, when
+the number is much larger. About six in an hour
+does not sound a great deal. But that merely means
+that there have been six in one direction, and near
+enough for you to see. Somebody else, watching,
+may have seen six in another direction; and somebody
+else, a few miles away, may have seen six more.
+It is calculated that, in the course of every twenty-four
+hours, about four hundred millions of meteorites
+fall to earth, including those visible only through
+telescopes.</p>
+
+<p>This is rather startling. What if you or I should
+some day be struck by one of these solid, hard little
+bodies, darting as they do towards earth with speed
+swifter than that of a cannon-ball? True, they are
+not really stars, neither are they really planets. But<span class="pagenum" id="Page_86">[Pg 86]</span>
+they are, to say the least, often much larger than a
+cannon-ball, and a cannon-ball can destroy life.</p>
+
+<p>Four hundred millions every twenty-four hours!
+Does it not seem singular that we do not see them
+constantly dropping to the ground? The truth is, we
+<i>should</i> see them, and feel them too, and dire would
+be the danger to human life, but for a certain protecting
+something folded round this earth of ours to
+ward off the peril. That “something” is the earth’s
+atmosphere. But for the thick, soft, strong, elastic
+air through which the meteorites have to pass, they
+would fall with fearful violence, often doing terrible
+mischief. As it is, we are guarded. The shooting-star,
+drawn by the earth’s attraction, drops into her
+atmosphere, darting with tremendous speed. In consequence
+of this speed and the resistance of the air,
+it catches fire. That is when we first see it. The
+meteorites are believed to appear at a height of about
+seventy miles, and to disappear at a height of about
+fifty miles. So that, in one instant’s flash, the shooting-star
+has traveled some twenty miles toward us.
+Then the light goes out. The little meteorite is burnt.
+It falls to earth still; but only as fine dust, sinking
+harmlessly downward.</p>
+
+<p>The meteorites do not always vanish so quickly.
+Now and then a larger one—too large to be rapidly
+burnt—does actually reach the ground. If any man
+were struck by such a stone he would undoubtedly be
+killed.</p>
+
+<p>When meteorites thus fall to earth they are usually
+called <i>aërolites</i>. Some are found no bigger than a
+man’s fist, while others much exceed this size. There<span class="pagenum" id="Page_87">[Pg 87]</span>
+is one, kept carefully in the British Museum, which
+weighs three tons and a half; and we hear of another,
+lying in South America, between seven and eight feet
+in length. Such a sky-visitant would be very unwelcome
+in any of our towns.</p>
+
+<p>We must remember that, whatever size an aërolite
+may be when it reaches the earth, it must have been
+far greater when journeying round the sun, since a
+good part of it has been burnt away during its rush
+downward through the earth’s atmosphere.</p>
+
+<p>Meteors, or bolides, or fireballs, are of much the
+same nature as meteorites; but they are larger, longer
+to be seen, and slower in movement. Also, it is not
+uncommon for them to burst with a loud explosion.
+Early in the present century such a meteor visited
+Normandy. It exploded with a noise like the roll of
+musketry, scattering thousands of hot stones over a
+distance of several miles. A great number of them
+were collected, still smoking. The largest of these
+stones weighed no less than twenty pounds. Happily
+no one seems to have been injured. Other such
+falls have taken place from time to time. Sometimes
+bright, slowly-moving meteors have been seen, looking
+as large as the moon.</p>
+
+<p>A remarkable fireball appeared in England on
+November 6, 1869. This fireball was extensively
+seen from different parts of the island, and by combining
+and comparing these observations, we obtain
+accurate information as to the height of the object
+and the velocity with which it traveled. It appears
+that this meteor commenced to be visible at a point
+ninety miles above Frome, in Somersetshire, and that<span class="pagenum" id="Page_88">[Pg 88]</span>
+it disappeared at a point twenty-seven miles over the
+sea, near St. Ives, in Cornwall. The whole length of
+its course was about 170 miles, which was performed
+in a period of five seconds, thus giving an average velocity
+of thirty-four miles a second. A remarkable
+feature in the appearance which this fireball presented
+was the long, persistent streak of luminous
+cloud, about fifty miles long and four miles wide,
+which remained in sight for fully fifty minutes. We
+have in this example an illustration of the chief features
+of the phenomena of a shooting-star presented
+on a very grand scale. It is, however, to be observed
+that the persistent luminous streak is not a universal,
+nor, indeed, a very common characteristic of a shooting-star.</p>
+
+<p>If we may liken comets to the <i>fishes</i> of the Solar
+System—and in their number, their speed, their varying
+sizes, their diverse motions, they may be fairly so
+likened—we may perhaps speak of the meteorites as
+the <i>animalcula</i> of the Solar System. For, in comparison
+with the planets, they are, in the matter of
+size, as the animalcula of our ponds in comparison
+with human beings. In point of numbers they are
+countless.</p>
+
+<p>Take a single drop of water from some long-stagnant
+pond, and place it under a powerful microscope.
+You will find it to be full of life, teeming with tiny animals,
+darting briskly to and fro. The drop of water
+is in itself a world of living creatures, though the
+naked eye of man could never discover their existence.
+So with the meteorites. There is good reason to believe
+that the Solar System fairly teems with them.<span class="pagenum" id="Page_89">[Pg 89]</span>
+We talk of “wide gaps of empty space,” between the
+planets; but how do we know that there is any such
+thing as empty space to be found throughout all the
+sun’s domain?</p>
+
+<p>Not only are the meteorites themselves countless, a
+matter easily realized, but the families or systems of
+meteorites appear to be countless also. They, like
+the systems of Jupiter and Saturn, are each a family
+within a family—a part of the Solar System, and yet
+a complete system by themselves. Each circles round
+the sun, and each consists of millions of tiny meteorites.
+When I say “tiny,” I mean it of course only by
+comparison with other heavenly bodies. Many among
+them may possibly be hundreds of feet and even more
+in diameter, but the greater proportion appear to be
+much smaller. It is not impossible that multitudes
+beyond imagination exist, so small in size that it is
+impossible we should ever see them, since their
+dying flash in the upper regions of our atmosphere
+would be too faint to reach our sight.</p>
+
+<p>The earth, traveling on her narrow orbit round the
+sun, crosses the track of about one hundred of these
+systems, or rings. Sometimes she merely touches the
+edge of a ring, and sometimes she goes into the very
+thick of a dense shower of meteorites. Twice every
+year, for instance, on the 10th of August and the 11th
+of November, the earth passes through such a ring,
+and very many falling stars may be seen on those
+nights. Numbers of little meteorites, dragged from
+their orbits and entangled in the earth’s atmosphere,
+like a fly caught in a spider’s web, give their dying
+flash, and vanish. It used to be supposed that the<span class="pagenum" id="Page_90">[Pg 90]</span>
+August and November meteorites belonged to one
+single system; but now they are believed to be two
+entirely distinct systems.</p>
+
+<div class="figcenter" id="f14">
+<img src="images/fig14.jpg" alt="shower">
+<p class="caption">THE GREAT SHOWER OF SHOOTING-STARS, NOVEMBER 27, 1872.</p>
+</div>
+
+<p>The comet discovered on February 27, 1827, by
+Biela, and ten days later at Marseilles by Gambart,
+who recognized that it was the same as that of 1772
+and 1805, returned six and a half years later, in 1832.
+In fact it crossed, as we have seen, the plane of the
+terrestrial orbit at the respectable distance of fifty
+millions of miles from the earth; but if there was
+any danger in this meeting, it was rather for it than
+for us; for it was certainly strongly disturbed in its
+course. It returned in 1839, but under conditions
+too unfavorable to enable it to be observed—in the
+month of July, in the long days, and too near the
+sun. It was seen again in 1845, on November<span class="pagenum" id="Page_91">[Pg 91]</span>
+25th, near the place assigned to it by calculation, and
+its course was duly followed. Everything went on to
+the general satisfaction, when—unexpected spectacle!—on
+January 13, 1846, <i>the comet split into two</i>! What
+had passed in its bosom? Why this separation? What
+was the cause of such a celestial cataclysm? We do
+not know; but the fact is, that instead of one comet,
+two were henceforth seen, which continued to move
+in space like two twin-sisters—two veritable comets,
+each having its nucleus, its head, its coma, and its
+tail, slowly separating from each other. On February
+10th there was already a hundred and fifty thousand
+miles of space between the two. They would seem,
+however, to have parted with regret, and during several
+days a sort of bridge was seen thrown from one
+to the other. The cometary couple, departing from
+the earth, soon disappeared in the infinite night.</p>
+
+<p>They returned within view of the earth in the
+month of September, 1852. On the 26th of this
+month the twins reappeared, but much farther apart,
+separated by an interval of twelve hundred and fifty
+thousand miles.</p>
+
+<p>But this is not the strangest peculiarity which this
+curious body presented to the attention of astronomers.
+The catastrophe which was observed in 1846 was only
+a presage of the fate which awaited it; for now its existence
+is merely imagined, the truth being that <i>this
+comet is lost</i>. Since 1852 all attempts to find it again
+have been unavailing.</p>
+
+<p>To be lost is interesting, especially for a comet.
+But this, doubtless, was not enough; for it reserved
+for us a still more complete surprise. Its orbit intersects<span class="pagenum" id="Page_92">[Pg 92]</span>
+the terrestrial orbit at a point which the earth
+passes on November 27th. Well, nothing more was
+thought about it—it was given up as hopeless, when,
+on the evening of November 27, 1872, there fell from
+the sky a veritable <i>rain of shooting stars</i>. The expression
+is not exaggerated. They fell in great flakes.
+Lines of fire glided almost vertically in swarms and
+showers—here, with dazzling globes of light; there,
+with silent explosions, recalling to mind those of rockets;
+and this rain lasted from seven o’clock in the
+evening till one o’clock next morning, the maximum
+being attained about nine o’clock. At the observatory
+of the Roman College, 13,892 were counted; at Montcalieri,
+33,400; in England a single observer counted
+10,579, etc. The total number seen was estimated at
+<i>a hundred and sixty thousand</i>. They all came from the
+same point of the sky, situated near the beautiful star
+Gamma of Andromeda.</p>
+
+<p>On that evening I happened to be at Rome, in the
+quarter of the Villa Medicis, and was favored with a
+balcony looking towards the south. This wonderful
+rain of stars fell almost before my eyes, so to say, and
+I shall never cease regretting not having seen it.
+Convalescent from a fever caught in the Pontine
+Marshes, I was obliged to go into the house immediately
+after the setting of the sun, which on that evening
+appeared from the top of the Coliseum to sleep in
+a bed of purple and gold. My readers will understand
+what disappointment I felt next morning when, on going
+to the observatory, Father Secchi informed me of
+that event! How had he observed it himself? By
+the most fortunate chance: A friend of his, seeing the<span class="pagenum" id="Page_93">[Pg 93]</span>
+stars fall, went to him to ask an explanation of such a
+phenomenon. It was then half-past seven. The spectacle
+had commenced; but it was far from being finished,
+and the illustrious astronomer was enabled to
+view the marvelous shower of nearly <i>fourteen thousand</i>
+meteors.</p>
+
+<p>This event made a considerable stir in Rome, and
+the pope himself did not remain indifferent; for, some
+days afterwards, having had the honor of being received
+at the Vatican, the first words that Pius IX addressed
+to me were these: “Have you seen the shower
+of Danaë?” I had admired, some days before in
+Rome, some admirable “Danaës,” painted by the
+great masters of the Italian school in a manner which
+left nothing to be desired; but I had not had the
+privilege of finding myself under the cupola of the
+sky during this new celestial shower, more beautiful
+even than that of Jupiter.</p>
+
+<p>What was this shower of stars? Evidently—and
+this is not doubtful—the encounter with the earth of
+myriads of small particles of matter moving in space
+along the orbit of Biela’s comet. The comet itself,
+if it still existed, would have passed twelve weeks before.
+It was not, then, to speak correctly, the comet
+itself which we encountered, but perhaps a fraction
+of its decomposed parts, which, since the breaking-up
+of the comet in 1846, would be dispersed along its
+orbit behind the head of the comet.<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">[1]</a></p>
+
+<div class="footnote">
+
+<p><a id="Footnote_1" href="#FNanchor_1" class="label">[1]</a> No doubt can remain of the identity of this swarm of shooting-stars
+with the comet of Biela. On November 27, 1885, the
+same encounter occurred. A magnificent shower of stars was observed
+all over Europe just at the moment when the earth crossed
+the comet’s orbit.</p>
+
+</div>
+
+<p><span class="pagenum" id="Page_94">[Pg 94]</span></p>
+
+<p>Once in every thirty-three years we have a grand
+display of meteorites in November; tens of thousands
+being visible in one single night. The meteorites in
+that ring have their “year” of thirty-three earthly
+years, and once in the course of that long year our
+earth’s orbit carries her deep into their midst. In
+this single November ring there are myriads upon
+myriads of meteorites, spreading through millions of
+miles of space.</p>
+
+<p>Yet this system is but one among many. There is
+no reason whatever to suppose that the streams of meteorites
+cluster more thickly about the orbit of the
+earth, than in other parts of the Solar System. No
+doubt the rest of the planets come across quite as
+many. Indeed, the wonderful rings of Saturn are
+probably formed entirely of meteorites—millions upon
+millions of them whirling round the planet in a regular
+orbit-belt, lit up by the rays of the sun. Also it is
+believed that the meteorite families cluster more and
+more closely in the near neighborhood of the sun,
+rushing wildly round him, and falling by millions into
+the ocean of flame upon his surface. It has even been
+guessed that they may serve in part as fuel to keep up
+his mighty furnace heat.</p>
+
+<p>There is a curious cone-shaped light seen sometimes
+in the west after sunset. It is called the “Zodiacal
+Light,” and men have often been much puzzled
+to account for it. The shining is soft and dim, only
+to be seen when the sky is clear, and only to be seen
+in the neighborhood of the sun. This, too, <i>may</i> be
+caused by reflected light from countless myriads of
+meteorites gathering thickly round the sun.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_95">[Pg 95]</span></p>
+
+<h2 class="nobreak" id="c9">CHAPTER IX.</h2>
+</div>
+
+<p class="c sp">NEIGHBORING FAMILIES.</p>
+
+
+<p><span class="smcap large">We</span> have now to take flight in thought far, far beyond
+the outskirts of our little Solar System. Yes,
+our <i>great</i> Solar System, with its mighty sun, its
+planets, its moons, its comets and meteorites, its
+ceaseless motions, its vast distances,—even all this
+sinks to littleness beside the wider reaches of space
+which now have to be pictured to our minds. For
+our sun, in all his greatness, is only a single star—only
+one star among other stars—and not by any
+means one of the largest of the stars.</p>
+
+<p>How many stars are there in the sky? Look overhead
+some cloudless night, and try to count the brilliant
+points of light. “Millions,” you would most
+likely give as your idea of their number. Yet you
+would be wrong; for you do not really perceive so
+many. The stars visible to man’s naked eye have
+been mapped and numbered. It is found that from
+two to three thousand are, as a rule, the utmost ever
+seen at once, even on a favorable night, and with particularly
+good sight.</p>
+
+<p>But what is actually the full number of the stars?
+Two or three thousand overhead. Five or six thousand
+round the whole world. So much visible to
+man’s unaided eyes. Ah, but take a telescope, and
+see through it the opening fields of stars beyond stars.
+Take a stronger telescope, and note how, as you pierce<span class="pagenum" id="Page_96">[Pg 96]</span>
+deeper into space, fresh stars beyond fresh stars shine
+faintly in the measureless distance. Take the most
+powerful telescope ever made, and again it will be the
+same story.</p>
+
+<p>There has been a chart or map drawn of known
+stars in the northern hemisphere—including those
+visible in telescopes down to a certain magnitude—containing
+over three hundred thousand. But that is
+only a part of even what man can see. Sir William
+Herschel calculated roughly that the number of stars
+within reach of his powerful telescope, round the
+whole earth, amounted probably to something like
+twenty millions.</p>
+
+<p>Twenty millions of suns! For that is what it really
+means. Twenty millions of radiant, burning, heavenly
+bodies—some the same size as our sun; some
+larger, perhaps very much larger; some smaller, perhaps
+very much smaller; but all <span class="allsmcap">SUNS</span>. And any
+number of these suns may have, just like our own,
+families of planets traveling round them, enjoying
+their light and their heat.</p>
+
+<p>We talk about stars of the first, second, and other
+magnitudes. Stars can be seen without a telescope
+as low down as the sixth magnitude; after that they
+become invisible to the naked eye. This word “magnitude”
+is rather misleading. “Magnitude” means
+size, and whatever the real size of the stars may be,
+they have to our sight no seeming size at all. So
+when we speak of different <i>magnitudes</i>, we really
+mean different <i>brightnesses</i>. The brightest stars are
+those of the first magnitude, the next brightest those
+of the second magnitude, and so on. No doubt many<span class="pagenum" id="Page_97">[Pg 97]</span>
+a star of the third or fourth magnitude is really much
+larger than many a star of the first or second magnitude,
+only being farther away it shines more dimly, or
+the higher-magnitude star may in itself possess greater
+natural brilliancy.</p>
+
+<p>Of first-magnitude stars there are altogether about
+twenty; of second-magnitude stars about sixty-five;
+of third-magnitude stars about two hundred; and so
+the numbers increase till of the sixth-magnitude stars
+we find more than three thousand. These are all that
+can be commonly seen with the naked eye, amounting
+to five or six thousand. With telescopes the numbers
+rise rapidly to tens of thousands, hundreds of thousands,
+and even millions.</p>
+
+<p>For a long while it was found quite impossible to
+measure the distances of the stars. To this day the
+distances of not over two dozen, among all those tens
+of thousands, have been discovered. The difficulty of
+finding out the distance of the sun was as nothing
+compared with the difficulty of finding out the distances
+of the stars.</p>
+
+<p>No base-line sufficient for the purpose could for
+years be obtained. I must explain slightly what is
+meant by a “base-line.” Suppose you were on the
+brink of a wide river, which you had no means of
+crossing, though you wished to discover its breadth.
+Suppose there were on the opposite brink a small
+tree, standing alone. As you stood, you would see
+the tree seeming to lie against a certain part of the
+country beyond. Then, if you moved along your
+bank some fifty paces, the tree would seem to lie
+against quite a different part of the country beyond.</p>
+
+<p><span class="pagenum" id="Page_98">[Pg 98]</span></p>
+
+<p>Now if you had a long piece of string to lay down
+along the fifty paces you walked, and if two more
+pieces of string were tied, one from each <i>end</i> of the
+fifty paces, both meeting at the tree, then the three
+pieces of string would make one large triangle, and
+the “fifty paces” would be the “base” of your triangle.</p>
+
+<p>If you could not cross the river, you could not of
+course tie strings to the tree. But having found your
+<i>base-line</i>, and measured its exact length, and having
+also found the shape of the two angles at its two ends,
+by noting the seeming change of the tree’s position,
+it would then be quite easy to find out the distance
+of the tree. The exact manner in which this calculation
+is made can hardly be understood without some
+slight knowledge of a science called trigonometry.
+The tree’s distance being found, the breadth of the river
+would be known.</p>
+
+<p>This mode of measuring distance was found comparatively
+easy in the case of the moon. But in the
+case of the sun there was more difficulty, on account
+of the sun’s greater distance. No base-line of ordinary
+length would make the sun seem to change his position
+in the sky in the slightest degree. Nor till the
+very longest base-line on the earth was tried could the
+difficulty be overcome. That base-line is no less than
+eight thousand miles long. One man standing in
+England looking at the sun, and another man standing
+in Australia looking at the sun, have such a base-line
+lying between them, straight through the center
+of the earth.</p>
+
+<p>In the case of the stars this plan was found useless.<span class="pagenum" id="Page_99">[Pg 99]</span>
+So closely has the sky been mapped out, and so exactly
+is the place of each star known, that the tiniest
+change would have been at once noticed. Not a star
+showed the smallest movement. The eight thousand
+miles of the earth’s diameter was a mere point with
+regard to them.</p>
+
+<p>A bright idea came up. Here was our earth traveling
+round the sun, in an orbit so wide that in the
+middle of summer she is over one hundred and eighty
+millions of miles away from where she is in the middle
+of winter. Would not that make a magnificent
+base-line? Why not observe a star in summer and
+observe the same star again in winter, and then calculate
+its distance.</p>
+
+<p>This, too, was done. For a long while in vain!
+The stars showed no signs of change, beyond those due
+to causes already known. Astronomers persevered,
+however, and with close and earnest care and improved
+instruments, success at last rewarded their efforts.
+A few—only a few, but still a few—of those distant
+suns have submitted to the little measuring-line of
+earth, and their distance has been roughly calculated.</p>
+
+<p>Now, what is their distance? Alpha Centauri, the
+second star which was attempted with success, is the
+nearest of all whose distance we know. You have
+heard how far the sun is from the earth. The distance
+of Alpha Centauri is <i>two hundred and seventy-five
+thousand times as much</i>. Can you picture to yourself
+that vast reach of space—a line ninety-three millions
+of miles long, repeated over and over again two hundred
+and seventy-five thousand times?</p>
+
+<p>But Alpha Centauri is one of the very nearest.<span class="pagenum" id="Page_100">[Pg 100]</span>
+The brilliant Sirius is at least twice as far away.
+Others utterly refuse to show the smallest change
+of position. It is with them, as had been said, much
+the same as if a man were to look at a church-steeple,
+twenty miles distant, out of one pane in a
+window, and then were to look at it out of the next
+pane. With the utmost attention he would find no
+change of position in the steeple. And like the base-line
+of two glass panes to that steeple, so is the base-line
+formed by our whole yearly journey to thousands
+of distant stars. We <i>might</i> measure how far away
+they are, only the longest base-line within our reach
+is too short for our purpose.</p>
+
+<p>The planet Neptune has a wider orbit than ours.
+But even his orbit, seen from the greater number of
+the stars, would shrink to a single point. After all,
+how useless to talk of two hundred and seventy-five
+thousand times ninety-three millions of miles! What
+does it mean? We can not grasp the thought.</p>
+
+<p>Let us look at the matter from another view. Do
+you know how fast light travels—this bright light
+shining round us all day long? Light, so far as we
+know, does not exist everywhere. It travels to and
+fro, from the sun to his planets, from the planets to
+one another; from the sun to the moon, from the
+moon to the earth, and from the earth to the moon
+again.</p>
+
+<p>Light takes time to travel. This sounds singular,
+but it is true. Light can not pass from place to place
+in no time. Light, journeying through space, is invisible.
+Only when it strikes upon something, whether
+a solid body or water or air, does it become visible to<span class="pagenum" id="Page_101">[Pg 101]</span>
+our eyes. The shining all round us in the day-time
+is caused by the sunlight being reflected, not only
+from the ground, but from each separate particle of air.
+If we had no atmosphere, we should see still the bright
+rays falling on the ground, but the sky above would
+be black. Yet that black sky would be full of millions
+of light-rays, journeying hither and thither from
+sun and stars, invisible except where they alight upon
+something.</p>
+
+<p>The speed of light is far beyond that of an express
+train, far beyond that of the swiftest planet. In one
+tick of the clock, Mercury has rushed onward twenty-nine
+miles. In one tick of the clock, storm-flames
+upon the surface of the sun will sweep over two or
+three hundred miles. But in one tick of the clock a
+ray of light flashes through one hundred and eighty-six
+thousand three hundred and thirty-seven miles.</p>
+
+<p>One hundred and eighty-six thousand miles! That
+is the same as to say that, during one single instant,
+a ray of light can journey a distance equal to about
+eight times round and round our whole earth at the
+Equator.</p>
+
+<p>By using this wonderful light-speed as a measurement,
+we gain clearer ideas about the distances of the
+stars. A ray of light takes more than eight minutes
+to pass from the sun to the earth. Look at your watch,
+and note the exact time. See the hand moving slowly
+through the minutes, and imagine one single ray of
+light, which has left the sun when first you looked,
+flashing onward and onward through space, one hundred
+and eighty-six thousand miles each second. Eight
+minutes and a half are over. The ray falls upon your<span class="pagenum" id="Page_102">[Pg 102]</span>
+hand. In those few minutes it has journeyed ninety-three
+millions of miles.</p>
+
+<p>So much for the sun’s distance. How about the
+stars? Alpha Centauri, a bright star seen in the
+southern hemisphere, is one of our nearest neighbors.
+Yet each light-gleam which reaches the eye of man
+from that star, left Alpha Centauri four years and a
+third before. During four years and a third, from the
+moment when first it quitted the surface of the blazing
+sun, it has flashed ceaselessly onward, one hundred
+and eighty-six thousand miles each second, dwindling
+down with its bright companion-rays from a glare of
+brilliancy to a slender glimmer of light till it reaches
+the eye of man. Four years and a third sounds much,
+side by side with the eight minutes’ journey from the
+sun. Sound would take more than three millions of
+years to cross the same abyss. At the constant velocity
+of thirty-seven miles an hour, an express-train
+starting from the sun Alpha Centauri would not reach
+the earth until after an uninterrupted course of nearly
+seventy-five millions of years.</p>
+
+<p>This is our <i>neighbor</i> star. The second, the nearest
+after it, is nearly double as far, and is found in
+quite another region of space, in the constellation of
+Cygnus, the Swan, always visible in our northern
+hemisphere. If we wish to understand the relative
+situation of our sun and the nearest two, let us take
+a celestial globe, and draw a plane through the center
+of the globe and through Alpha Centauri and 61
+Cygni. We shall thus have before us the relation
+which exists between our position in infinitude and
+those of these two suns. The angular distance which<span class="pagenum" id="Page_103">[Pg 103]</span>
+separates them on the celestial sphere is 125°. Let
+us make this drawing, and we shall discover certain
+rather curious particulars. In the first place, these
+two nearest stars are in the plane of the Milky Way,
+so that we can also represent the Milky Way on our
+drawing; again, this celestial river is divided into
+two branches, precisely in the positions occupied by
+these two nearest stars, the division remaining marked
+along the whole interval which separates them. This
+drawing shows us, further, that if we wish to trace the
+curve of the Milky Way with reference to the distance
+of our two stars, it will be nearer to us in the constellation
+of the Centaur than in that of the Swan;
+and, in fact, it is probable that the stars of that region
+of the sky are nearer than those of the opposite region.
+Another very curious fact is, that both the
+nearest stars are double.</p>
+
+<p>But look at Sirius, that beautiful star so familiar to
+us all. The light which reaches you to-night, left his
+surface from nine to ten years ago. Look at the Little
+Bear, with the Pole-star shining at the end of his tail.
+That ray of soft light quitted the Pole-star some forty
+years ago. Almost half a century it has been speeding
+onward and ever onward, with ceaseless rapidity,
+till its vast journey is so far accomplished that it has
+reached the earth. Look at Capella, another fair star
+of the first magnitude. The light which reaches you
+from her has taken over thirty years to perform its
+voyage. Ten, thirty, forty years—at the rate of
+186,000 miles per second!</p>
+
+<p>These stars are among the few whose distance can
+be roughly measured. Others lie at incalculable distances<span class="pagenum" id="Page_104">[Pg 104]</span>
+beyond. There are stars whose light must, it
+is believed, have started hundreds or even thousands
+of years before the soft, faint ray at length reaches
+the astronomer’s upturned eye through the telescope.</p>
+
+<p>Look at Capella, how gently and steadily she
+shines! You see Capella, not as she is <i>now</i>, but as
+she <i>was</i> thirty years ago. Capella may have ceased
+to exist meantime. The fires of that mighty sun
+may have gone out. If so, we shall by and by learn
+the fact—more than thirty years after it happened.
+Look at the Pole-star. Is there any Pole-star now?
+I can not tell you. I only know there <i>was</i> one, forty
+years ago, when that ray of light started on its long
+journey. Stars have ceased to shine before now.
+What may have happened in those forty years, who
+can say? Look at that dim star, shining through a
+powerful telescope with faint and glimmering light.
+We are told that in all probability the tiny ray left its
+home long before the time of Adam.</p>
+
+<p>There is a strange solemnity in the thought. Hundreds
+of years ago—thousands of years ago—some say,
+even tens or hundreds of thousands of years ago! It
+carries us out of the little present into the unknown
+ages of a past eternity.</p>
+
+<p>If the neighboring stars are placed at tens and
+hundreds of trillions of miles from us, it is at quadrillions,
+at quintillions of miles that most of the stars
+lie which are visible in the sky in telescopic fields.
+What suns! what splendors! Their light comes from
+such distances! And it is these distant suns which
+human pride would like to make revolve round our
+atom; and it was for our eyes that ancient theology<span class="pagenum" id="Page_105">[Pg 105]</span>
+declared these lights, invisible without a telescope,
+were created! No contemplation expands the thought,
+elevates the mind, and spreads the wings of the soul
+like that of the sidereal immensities illuminated by
+the suns of infinitude. We are already learning that
+there is in the stellar world a diversity no less great
+than that which we noticed in the planetary world.
+As in our own Solar System the globes already studied
+range from 6 miles in diameter (satellites of Mars)
+up to 88,000 miles (Jupiter)—that is to say, in the
+proportion of 1 to 14,000—so in the sidereal system
+the suns present the most enormous differences of
+volume and brightness: 61 Cygni, the stars numbered
+2,398 in the catalogue of Lalande, and 9,352 in the
+catalogue of Lacaille, and others of the eighth or ninth
+magnitude, are incomparably smaller or less luminous
+than Sirius, Arcturus, Capella, Canopus, Rigel, and
+the other brilliants of the firmament.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_106">[Pg 106]</span></p>
+
+<h2 class="nobreak" id="c10">CHAPTER X.</h2>
+</div>
+
+<p class="c sp">OUR NEIGHBORS’ MOVEMENTS.</p>
+
+
+<p><span class="smcap large">How high</span>! how distant! how mighty! How little
+we know about them, yet how overwhelming the little
+we know, and how wonderful that we do know it!</p>
+
+<p>We have now to consider the movements of these
+distant neighbors—first, their seeming movements;
+secondly, their real movements.</p>
+
+<p>I have already spoken about the seeming motions
+of the stars as a whole, once believed to be real, and
+now known to be only caused by the motions of our
+earth. For just as the turning of the earth upon her
+axis makes the sun seem to rise every morning in the
+east, and to set every evening in the west, so that
+same continued turning makes the stars seem to rise
+every evening in the east and to set every morning in
+the west.</p>
+
+<p>When we speak of the stars as rising in the east,
+we do not mean that they all rise at one point in the
+east, but that all rise, more or less, in an easterly direction—northeast,
+east, and southeast. So also with
+respect to the west. It is to the east and west of the
+earth as a whole that they rise and set—not merely to
+the east and west of that particular spot on earth
+where one man may be standing. All night long fresh
+stars are rising, and others are setting, and if it were
+not for the veil of light made by the sunshine in our
+atmosphere, we should see the same going on all day
+long as well.</p>
+
+<p><span class="pagenum" id="Page_107">[Pg 107]</span></p>
+
+<p>There are some constellations, or groups of stars,
+always visible at night in our northern hemisphere;
+and there are some constellations never visible to us,
+but only seen by people living in the southern hemisphere—in
+Australia, for instance. There are other
+constellations which appear in summer and disappear
+in winter, or which appear in winter and disappear in
+summer. This change is caused by our earth’s journey
+round the sun. It is not that the constellations
+have altered their place in the heavens with respect
+to the other constellations, it is merely that the earth
+has so altered its position in the heavens that the
+groups of stars which a short time ago were above the
+horizon with the sun by day are now above the horizon
+without him by night.</p>
+
+<p>Mention has been a good many times made of the
+axis of the earth ending in the North and South Poles.
+If this axis were carried straight onward through
+space, a long, slender pole passing upwards into the
+sky without any bend, from the North Pole in one
+direction and from the South Pole in the other,—this
+would be the pole of the heavens. The places of the
+stars in the sky are counted as “so many degrees”
+from the North and South Celestial Poles, just as the
+places of towns on earth are counted as “so many
+degrees” from the North and South Poles of earth.
+There are atlases of the sky made as well as atlases of
+the earth.</p>
+
+<p>The constellation of the Great Bear is known to all
+who have ever used their eyes at all to watch the
+heavens. Almost equally well known are the two
+bright stars in this constellation named the Pointers,<span class="pagenum" id="Page_108">[Pg 108]</span>
+because, taken together, they point in nearly a straight
+line to a certain important star in the end of the Little
+Bear’s tail, not very distant.</p>
+
+<p>This star, important less from its brightness than
+from its position, lies close to that very spot in the
+heavens where the celestial North Pole passes. It is
+called the Pole-star. Night after night, through the
+year, it there remains, all but motionless, never going
+below the horizon for us in the northern hemisphere,
+or northern half of the earth; never rising above the
+horizon for those in the southern hemisphere. It
+shines ever softly and steadily in its fixed position.
+If you travel further south, the Pole-star sinks downward
+towards the horizon. If you travel further
+north, the Pole-star rises higher above the horizon.
+If you were at the North Pole, you would see the Pole-star
+exactly overhead.</p>
+
+<div class="figcenter" id="f15">
+<img src="images/fig15.jpg" alt="bear">
+<p class="caption">CONSTELLATION OF THE GREAT BEAR.</p>
+</div>
+
+<p>Very near the Pole-star is the constellation of the
+Great Bear, with Cassiopeia nearly opposite on the
+other side of the Little Bear, and other groups between
+the two, completing the circle. These constellations
+do not, to us who live in the northern
+hemisphere, rise or set; for they simply move in a<span class="pagenum" id="Page_109">[Pg 109]</span>
+circle round and round the Pole-star, never going below
+the horizon. All day and all night long this
+circling movement continues, though only visible at
+night. It is caused entirely by the earth’s own motion
+on her axis.</p>
+
+<div class="figcenter" id="f16">
+<img src="images/fig16.jpg" alt="bear">
+<p class="caption">THE GREAT BEAR 50,000 YEARS AGO.</p>
+</div>
+
+<div class="figcenter1" id="f17">
+<img src="images/fig17.jpg" alt="bear">
+<p class="caption">THE GREAT BEAR 50,000 YEARS HENCE.</p>
+</div>
+
+<p>Lower down, or rather further off from the Pole-star,
+comes another ring of constellations. These in
+just the same manner appear to travel round and
+round the Pole-star. But being further away, each
+dips in turn below the horizon—or, as we call it, each
+sets and rises again. And by the time we come to
+yet another circle of leading constellations, we reach<span class="pagenum" id="Page_110">[Pg 110]</span>
+those which are so far affected by the earth’s yearly
+journey as to be only visible through certain months,
+and to be hidden during other months.</p>
+
+<div class="figcenter" id="f18">
+<img src="images/fig18.jpg" alt="orion">
+<p class="caption">CONSTELLATION OF ORION, AS IT APPEARS NOW.</p>
+</div>
+
+<p>If we could stand exactly at the North Pole, during
+part of its six months’ night, we should see the Pole-star
+just overhead, and all the constellations circling
+round it once in every twenty-four hours. Those
+nearest would move slowly, in a small ring. Those
+furthest, and lowest down, would in the same length
+of time sweep round the whole horizon. But the
+stars would not there seem to rise or set. If we were
+standing at the South Pole, we should see exactly the
+same kind of seeming movement, only with altogether
+a different set of stars. If we were standing on the
+Equator at night, we should see the rising and setting
+very plainly. The whole mass of stars would
+appear to rise regularly and evenly in an easterly direction,
+to pass steadily across the sky, each taking<span class="pagenum" id="Page_111">[Pg 111]</span>
+its own straightforward path, and to set in a westerly
+direction.</p>
+
+<p>We who are placed midway between the Pole and
+the Equator, see a mixture of these two motions. Some
+stars seem to circle round and round, as all would do
+if we stood at the North Pole. Some stars seem to
+rise and set, as all would do if we stood at the Equator.
+So much for the seeming
+movements of the stars.</p>
+
+<p>But now, about their
+real movements. Are the
+stars fixed, or are they not?
+These seeming daily and
+yearly motions do not affect
+the question, being
+merely caused by our own
+motions. Trees and hedges
+may appear to move as
+we rush past them in a
+train, yet they are really
+fixed.</p>
+
+<div class="figright" id="f19">
+<img src="images/fig19.jpg" alt="orion">
+<p class="caption">CONSTELLATION OF ORION 50,000<br>
+YEARS FROM NOW.</p>
+</div>
+
+<p>During a long while,
+after it was found out that
+the quick, daily movements of all the stars in company
+were merely apparent, men believed that they
+really had no “proper motions”—that is, no movements
+of their own. For century after century the
+constellations remain the same. Hundreds of years
+ago the seven chief stars of the Great Bear shone in
+company as they shine now. Who could suppose that
+each one of those seven stars is hurrying on its path
+through space with a speed exceeding far that of the<span class="pagenum" id="Page_112">[Pg 112]</span>
+swiftest express-train? Yet so it is. Hundreds of
+years ago the grand group of Orion, with belt and
+sword, gleamed brilliantly night by night as it gleams
+in these days; and Cassiopeia had her W form, and
+Hercules and Draco and Andromeda were shaped as
+they are shaped still. Who would imagine that through
+those hundreds of years each star of these different
+constellations was hastening with more or less of speed
+along its heavenly road? Yet so it is.</p>
+
+<p>Cases have been decisively ascertained of stars
+changing their places among the other stars by a slow
+and gradual motion. Three of the most conspicuous
+of them—Sirius, Arcturus, and Aldebaran—have been
+proved, by the comparison of modern with some ancient
+observations, to have experienced a change of place
+to the southward, to the extent of more than the breadth
+of the moon in all the three. And during the period
+of accurate modern measurement, other instances have
+been ascertained of steady change of place by the
+effect of proper motion.</p>
+
+<p>But if the stars are thus rapidly moving in all directions,
+how is it that we do not <i>see</i> them move? How
+is it that, night after night, year after year, century
+after century, even thousand years after thousand
+years, the shapes of the constellations remain unaltered?</p>
+
+<p>Suppose you and I were standing on the seashore
+together, watching the movements of scores of
+sea-craft, little boats and large boats, steamers, yachts,
+and ships. Suppose we stood through a full quarter
+of an hour looking on. Some might move, it is true,
+very slowly; yet their movements in every case would<span class="pagenum" id="Page_113">[Pg 113]</span>
+plainly be seen. There could be no possibility of
+mistaking the fact, or of supposing them to be
+“fixed.” Just so we see the nearer planets move.
+Little danger of our supposing them to be “fixed
+stars.”</p>
+
+<p>In the matter of the stars themselves, we must
+carry our illustration further. Come with me up to
+the top of that lofty hill on the border of the sea, and
+let us look from the cliff. We see still the movements
+among boats and smacks, yachts and steamers,
+only the increased distance makes the movements
+seem slower. But our view is widened. Look on the
+far horizon and see three distant dots, which we know
+to be ships—one and two close together, and a third a
+little way off, making a small constellation of vessels.
+Watch them steadily for a quarter of an hour. You
+will detect no movement, no increased distance or
+nearness between any two of the three. The group
+remains unchanged.</p>
+
+<p>Are they really moving? Of course they are, more
+or less rapidly, probably with differing speed and in
+different directions. But at so great a distance, one
+quarter of an hour is not long enough for their motions
+to become visible to the naked eye. If we
+could watch longer—say, for two or three hours—ah,
+that would make all the difference! If only we could
+watch longer! But the hundreds, and even thousands
+of years during which men have watched the stars,
+sink, at our vast distance, into no more than one quarter
+of an hour spent in watching the far-off ships from
+the high hilltop. The motions can not be detected.
+In ten thousand years you might see something. In<span class="pagenum" id="Page_114">[Pg 114]</span>
+fifty thousand years you might see much. But four
+or five thousand years are not sufficient.</p>
+
+<p>One other mode there is, by means of which the
+movements of the ships on the horizon might be made
+plain. Suppose you had no more than the quarter of
+an hour to spare, but suppose you had at your command
+a powerful telescope. Then you may practically
+bring the ships nearer, and by magnifying the small,
+slow, distant motions, you may make them, as it were,
+larger, quicker, more easy to see.</p>
+
+<p>Telescopes will do this for us, likewise, in the matter
+of the stars. By means of telescopes, with the assistance
+of careful watching and of close calculation it
+has been found that the stars are really moving quickly,
+each one in his own pathway. The very speed of
+some of them has been measured.</p>
+
+<p>Arcturus is one of those stars, the motions of which
+are most plainly to be seen. In the course of about
+one thousand years he changes visibly his place in the
+sky by a space equal to the apparent diameter of the
+moon. The seeming movement of Arcturus in one
+thousand years is the same as the seeming width of
+the round moon that we see.</p>
+
+<p>But the actual speed with which Arcturus rushes
+through space is said to be no less than fifty-four
+miles each second, or not far from two hundred thousand
+miles an hour. That is nearly three times as
+fast as our own earth’s motion round the sun. How
+enormous the distance must be which can shrink
+such speed to such seeming slowness!</p>
+
+<p>Another beautiful star, Capella, is believed to travel
+at the rate of thirty miles each second. The speed<span class="pagenum" id="Page_115">[Pg 115]</span>
+of Sirius is slower, being only fourteen miles a second.
+The Pole-star creeps along at the rate of only one
+mile and a half each second.</p>
+
+<p>So also with the rest of the stars. There seems
+good reason to believe that every star we see shining
+in the heavens, every star visible in powerful telescopes,
+is perpetually hastening onward. But hastening
+whither? God knows! We do not.</p>
+
+<p>In all probability not one of the tens of millions
+of stars which may be seen through telescopes is in
+repose. This is a matter of conjecture, of reasoning
+from analogy, and of reasoning also from the working
+of known laws. We <i>know</i>, as a consequence of direct
+observation, apart from the new spectroscopic method,
+that at least hundreds are upon the wing. We <i>assume</i>,
+as a matter of the greatest possible likelihood, that all
+the millions besides, which can not be actually seen
+to stir, are equally on the move. Knowing what we
+do know of the laws by which the universe of stars is
+governed, it seems to us an absolute impossibility that
+any single star, amid the whole vast host, can be or
+could be permanently at rest.</p>
+
+<p>If by any means a star were brought to repose—what
+then would happen? It would inevitably start
+off again, drawn by the attraction of other stars.
+From whatever direction the strongest pull came, the
+impulse would be given. Lengthened repose would be
+out of the question. And this, it seems to us, must
+be true, not of one star only, here or there, but of
+every star in the enormous host of radiant suns which
+make up the mighty Stellar System.</p>
+
+<p>Our forefathers, one thousand years ago, could not<span class="pagenum" id="Page_116">[Pg 116]</span>
+measure the precise positions of individual stars, as
+astronomers now are able to do. They had no modern
+observatories, no telescopes, no spectroscopes, no photographic
+appliances. These methods of observation
+we shall explain in another chapter. Their measurements
+at best were rough, their scientific knowledge
+was crude. Had we any such accurate observations
+handed down from one thousand years ago as are
+made in these days, we should no doubt see clearly
+many slight differences in the positions of many stars
+which are not now apparent. But even then we
+should see no changes sufficient in amount to affect
+the general outlines of the leading constellations.</p>
+
+<p>A star, which in the course of a century makes
+visible advance over a space in the sky equal to only
+a small portion of the breadth of the full moon, is
+looked upon as a fast voyager. One hundred times
+this degree of movement, if it took place in a considerable
+number of stars in our sky, would not in
+centuries very materially change the face of our midnight
+heavens.</p>
+
+<p>And all motions which would in the remotest degree
+affect the shapes of constellations, must be sideway
+motions. Those line-of-sight motions, of which
+the spectroscope alone tells us, could never have been
+discovered by simple observation of the sky. Until
+the new method came to light we had no means
+whatever of perceiving such movements among the
+stars.</p>
+
+<p>Suppose you are looking at two men in the distance,
+upon a wide, flat plain. One of the two is
+walking very slowly <i>across</i> your line of vision. The<span class="pagenum" id="Page_117">[Pg 117]</span>
+second man is moving very slowly straight <i>towards</i>
+you. If you watch with care you may find out both
+the movements. The sideway walking will be apparent
+first and most easily, because, as the man
+moves, he has constantly a fresh part of the horizon
+behind him. But in time the advance of the second
+man towards you will also become apparent; for although
+he is seen still against precisely the same spot
+on the horizon, he slowly occupies a larger spot on
+the retina of your eye,—in other words, he seems to
+grow bigger. And that, as you know from long experience,
+can only mean increasing nearness.</p>
+
+<p>If a star seemed to grow larger as it drew nearer,
+we should then be able to perceive that movement
+also. But no star in the sky ever does seem to grow
+any larger. Every star is to us but one point of light.
+It may be rushing towards us at an enormous rate of
+speed, yet still as a single point it remains, always at
+the same point in our sky. Therefore we have no
+chance of perceiving its movement; or rather, we <i>had</i>
+no chance until the discovery of this new method.
+In fact, the very nearest known star is at so enormous
+a distance that, supposing it to be coming towards
+us at the rate of one hundred miles each
+second, it would still gain, in the course of a century,
+only one-fortieth part more of brightness than it has
+now. It would not increase at all in apparent size.</p>
+
+<p>When we leave behind us the thought of starry
+motions, as we faintly detect them at this great distance,
+and picture to ourselves the actual far-off whirl
+of all those glorious suns, the effect upon the mind is
+overwhelming. Stars are found to be rushing hither<span class="pagenum" id="Page_118">[Pg 118]</span>
+and thither, at every degree of speed, in every imaginable
+direction: stars to right, and stars to left; stars
+towards us, and stars away from us; stars alone, and
+stars in company,—all this, and more, deciphered out
+of the tiny gleam of quivering light, which streams
+through the vast abyss of space from each distant orb
+to earth. So real star-motions were known—first,
+through telescopic observation; secondly, through
+spectroscopic observation; and now, lastly, photography
+has stepped in, bringing with it much increase
+of exactitude.</p>
+
+<p>But if all the stars are moving, what of our sun?
+Our sun is a star. And our sun also is moving. He
+is pressing onward, in a wide sweep through space,
+bearing along with him his whole vast family—planets,
+satellites, comets, meteorites—round or towards some
+far distant center. For aught we know, every star in
+the heavens may have a like family traveling with him.</p>
+
+<p>In infinite space the stars are strewn in immense
+clusters, like archipelagoes of islands in the ocean
+of the heavens. To go from one star to another in
+the same archipelago light takes years; to pass from
+one archipelago to another it takes thousands of years.
+Each of these stars is a sun similar to ours, surrounded,
+doubtless, at least for the most part, by
+worlds gravitating in its light; each of these planets
+possesses, sooner or later, a natural history adapted to
+its constitution, and serves for many ages as the abode
+of a multitude of living beings of different species.
+Attempt to count the number of stars which people
+the universe, the number of living beings who are
+born and die in all these worlds, the pleasures and<span class="pagenum" id="Page_119">[Pg 119]</span>
+pains, the smiles and tears, the virtues and vices! Imagination,
+stop thy flight!</p>
+
+<p>The sun is not one of the most quickly-moving
+stars. His rate of speed has not been found out with
+any certainty, but it is believed to be about four or
+five miles a second.</p>
+
+<p>And where are we going? This has been in
+part discovered. If you and I were driving through a
+forest of trees, we should see the trees on each side of
+us seeming to move backward, while behind they
+would close together, and in front they would open out.</p>
+
+<p>Astronomers—and first among them, William Herschel—reasoned
+that if our Solar System were really
+in motion, we ought to be able to see these changes
+among the stars. And some such changes have become
+visible through careful watching—not so much
+those ahead and behind as those at the sides.</p>
+
+<p>It is not actually so simple a matter as looking at
+the trees in a forest, because the trees would be at rest,
+whereas each star has his own particular real motion,
+as well as his seeming change of place caused by our
+sun’s motion. It is more like moving in a small
+steamer at sea, among hundreds of other craft, each
+of which is going on its own way, at the same time
+that all on either side seem to move backward because
+we are moving forward.</p>
+
+<p>So each movement had to be noted, and the real
+motions had to be separated from the seeming backward
+drift of stars to the right and left of the sun’s
+pathway. The result of all this is that the sun, with
+his planets, is found to be hastening towards a certain
+far-off constellation named Hercules.</p>
+
+<p><span class="pagenum" id="Page_120">[Pg 120]</span></p>
+
+<p>It is a strange and unexpected fact, but absolutely
+true, that each sun of space is carried along with a
+velocity so rapid that a cannon-ball represents rest in
+comparison; it is at neither a hundred, nor three hundred,
+nor five hundred yards per second that the
+earth, the sun, Sirius, Vega, Arcturus, and all the
+systems of infinitude travel: it is at ten, twenty,
+thirty, a hundred thousand yards a second; all run, fly,
+fall, roll, rush through the void—and still, seen as a
+whole, all seems in repose.</p>
+
+<p>The immense distance which isolates us from all
+the stars reduces them to the state of motionless lights
+apparently fixed on the vault of the firmament. All
+human eyes, since humanity freed its wings from the
+animal chrysalis, all minds since minds have been,
+have contemplated these distant stars lost in the ethereal
+depths; our ancestors of Central Asia, the Chaldeans
+of Babylon, the Egyptians of the Pyramids, the
+Argonauts of the Golden Fleece, the Hebrews sung by
+Job, the Greeks sung by Homer, the Romans sung by
+Virgil,—all these earthly eyes, for so long dull and
+closed, have been fixed, from age to age, on these eyes
+of the sky, always open, animated, and living. Terrestrial
+generations, nations and their glories, thrones
+and altars have vanished: the sky of Homer is always
+there. Is it astonishing that the heavens were contemplated,
+loved, venerated, questioned, and admired,
+even before anything was known of their true beauties
+and their unfathomable grandeur?</p>
+
+<p>Better than the spectacle of the sea, calm or agitated,
+grander than the spectacle of mountains adorned
+with forests or crowned with perpetual snow, the spectacle<span class="pagenum" id="Page_121">[Pg 121]</span>
+of the sky attracts us, envelops us, speaks to us
+of the Infinite. “I have ascended into the heavens,
+which receive most of His light, and I have seen
+things which he who descends from on high knows
+not, neither can repeat,” wrote Dante in the first canto
+of his poem on “Paradise.” Let us, like him, rise towards
+the celestial heights, no longer on the trembling
+wings of faith, but on the stronger wings of science.
+What the stars would teach us is incomparably more
+beautiful, more marvelous, and more splendid than
+anything we can dream of.</p>
+
+<p>How do such contemplations enlarge and transfigure
+the vulgar idea which is generally entertained of the
+world! Should not the knowledge of these truths
+form the first basis of all instruction which aims at
+being serious? Is it not strange to see the immense
+majority of human beings living and dying without
+suspecting these grandeurs, without thinking of learning
+something of the magnificent reality which surrounds
+them?</p>
+
+<p>Where the sun and his planets will journey in future
+ages no living man can say. Indeed, though it
+is a question which does not lack interest to a thoughtful
+mind, yet there are numberless other questions
+about centuries near at hand which concern man far
+more nearly. The history of the Universe, and the
+history of this Earth of ours, must have advanced
+many broad stages before our sun and his attendant
+planets can have traveled so far that any change will
+be apparent in the shape of the star-constellations
+which spangle our sky.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_122">[Pg 122]</span></p>
+
+<h2 class="nobreak" id="c11">CHAPTER XI.</h2>
+</div>
+
+<p class="c sp">MORE ABOUT THE SOLAR SYSTEM.</p>
+
+
+<p><span class="smcap large">We</span> have now reached a point where it ought not to
+be difficult for us to picture to ourselves, with something
+of vividness, the general outlines of the Solar System.
+Awhile ago this Solar System was a very simple
+matter in the eyes of astronomers. There was the
+great sun fixed in the center, with seven planets circling
+round him—seven of course, it was said, since
+seven was the perfect number—and a few moons keeping
+pace with some of the planets, and an occasional
+comet, and a vast amount of black, empty space. But
+astronomers now begin to understand better the wonderful
+richness of the system as a whole; the immense
+variety of the bodies contained in it; the perpetual
+rush and stir and whirl of life in every part. Certainly
+there is no such thing as dull stagnation
+throughout the family.</p>
+
+<p>First, we have the great, blazing, central sun; not
+a sun at rest, as regards the stars, but practically at
+rest as regards his own system, of which he is always
+head and center. Then come the four smaller planets,
+rapidly whirling round him, all journeying in the
+same direction, and all having their oval pathways lying
+on nearly the same flat plane in space. Then the
+broad belt of busy little planetoids. Then the four
+giant planets,—Jupiter nearly five times as far as our
+earth from the sun; Saturn nearly twice as far as Jupiter;<span class="pagenum" id="Page_123">[Pg 123]</span>
+Uranus nearly twice as far as Saturn; Neptune
+as far from Uranus as Uranus from Saturn,—all keeping
+on very nearly the same level as the four inner planets.</p>
+
+<div class="figcenter" id="f20">
+<img src="images/fig20.jpg" alt="jupiter">
+<p class="caption">POSITION OF PLANETS INFERIOR TO JUPITER—SHOWING THE<br>
+ZONE OF THE ASTEROIDS.</p>
+</div>
+
+<p>And between and about these principal members of
+the system, with their accompanying moons, we have
+thousands of comets flashing hither and thither, with
+long, radiant trains; and myriads of meteorites, gathered
+often into dense, vast herds or families, but also scattered
+thickly throughout every part of the system,<span class="pagenum" id="Page_124">[Pg 124]</span>
+each tiny ball reflecting the sun’s rays with its little
+glimmer of light.</p>
+
+<p>Broad reaches of black and empty space! Where
+are they? Perhaps nowhere. We are very apt, in
+our ignorance, to imagine that where we see nothing,
+there must of necessity be nothing. But, for aught
+we know, the whole Solar System, not to speak of
+sky-depths lying beyond, may be bright with reflecting
+bodies great and small, from the mighty Jupiter
+down to the fine diamond-dust of countless meteorites.
+In this earth of ours we find no emptiness. Closer
+and closer examination with the microscope only
+shows tinier and yet tinier wonders of form and life,
+each perfect in finish. Not of form only, but of <i>life</i>.
+How about that matter as regards the Solar System? Is
+our little world the one only spot in God’s great universe
+which teems with life? Are all other worlds
+mere barren, empty wastes? Surely not. We may
+safely conclude that life of one kind or another has
+been, is, or will be, upon our brother and sister
+worlds.</p>
+
+<p>The same reasoning may be used for the distant
+stars—those millions of suns lying beyond reach of
+man’s unassisted eyes. Are they formed in vain?
+Do their beams pour uselessly into space, carrying
+light, warmth, and life-giving power to nothing?
+Surely around many of them, as around our sun,
+must journey worlds; and not only worlds, but worlds
+containing life.</p>
+
+<p>We shall have to speak of this matter again as we
+go on. Whether men and women like ourselves could
+live on the other planets is another question. In some<span class="pagenum" id="Page_125">[Pg 125]</span>
+cases it looks doubtful, in some it would seem to be
+impossible. But the endless variety of life on this
+earth—life on land, life in the air, life in water, life
+underground, life in tropical heat, life in arctic cold—forbids
+us in anywise to be positive as to what may or
+may not be.</p>
+
+<p>If no animals that we know could exist there, animals
+that we do not know might be found instead.
+Any one of the planets may, and very likely does,
+abound with life. Nay, the very meteorites themselves,
+before they catch fire and burn in our air, <i>may</i>
+be the homes of tiny animalcula, altogether different
+from anything we see on earth. We can not fancy
+life without air, but neither could we fancy life in
+water, if we had not seen and known it to be possible.</p>
+
+<p>I have spoken of the probable <i>brightness</i> of the
+Solar System as a whole. We are so apt to think of
+things merely as we see them with our short sight,
+that it is well sometimes to try to realize them as
+they actually are. Picture to yourself the great central
+sun pouring out in every direction his burning
+rays of light. A goodly abundance of them fall on
+our earth, yet the whole amount of light and heat received
+over the whole surface of this world is only the
+two-thousand-millionth part of the enormous amount
+which he lavishly pours into space. How much of
+that whole is wasted? None, though God gives his
+gifts with a kingly profusion which knows no bounds.
+Each ray has its own work to do. Millions of rays
+are needed for the lighting and nourishing and warming
+of our companion-planets, while others are caught
+up by passing comets, and myriads flash upon swift,<span class="pagenum" id="Page_126">[Pg 126]</span>
+tiny meteorites. Of the rays not so used, many pass
+onwards into the vast depths beyond our system, and
+dwindle down into dim, starlike shining till they reach
+the far-off brother-stars of our sun.</p>
+
+<p>Have they work to do there? We can not tell.
+We do not know how far the sun’s influence reaches.
+As head and center, he reigns only in his own system.
+As a star among stars, a peer among his equals,
+he may, for aught we can tell, have other work to do.</p>
+
+<p>In an early chapter, mention was made of the
+earth’s three motions, two only being explained.
+First, she spins ceaselessly upon her axis. So does
+the sun, and so do the planets. Secondly, she travels
+ceaselessly round and round the sun in her fixed orbit.
+So does each one of the planets. Thirdly, she journeys
+ceaselessly onward through space with the sun.
+So also do the rest of the planets. These last two
+movements, thought of together, make the earth’s
+pathway rather perplexing at first sight. We talk of
+her orbit being an ellipse or oval; but how can it be
+an ellipse, if she is always advancing in one direction?</p>
+
+<p>The truth is, the earth’s orbit is and is not an
+ellipse. As regards her yearly journey round the sun,
+roughly speaking, we may call it an ellipse. As regards
+her movement in space, it certainly is not an
+ellipse.</p>
+
+<p>Think of the Solar System, with the orbits of all
+the planets, as lying <i>nearly flat</i>—in the manner that
+hoops might be laid upon a table, one within another.
+The asteroids, comets, and meteorites do not keep to
+the same level; but their light weight makes the matter
+of small importance.</p>
+
+<p><span class="pagenum" id="Page_127">[Pg 127]</span></p>
+
+<p>Having imagined the sun thus in the center of a
+large table—a small ball, with several tiny balls traveling
+round him on the table at different distances—suppose
+the sun to rise slowly upwards, not directly
+up, but in a sharp slant, the whole body of planets
+continuing to travel round, and at the same time rising
+steadily with him.</p>
+
+<p>By carefully considering this double movement,
+you will see that the real motion of the earth—as
+also of each of the planets—is not a going round on
+a flat surface to the same point from which she started,
+but is a corkscrew-like winding round and round upwards
+through space. Yet as regards the central sun,
+the shape of the orbit comes very near being an ellipse,
+if calculated simply by the earth’s distance from
+him at each point in turn of her pathway through
+the year.</p>
+
+<p>An illustration may help to explain this. On the
+deck of a moving vessel, you see a little boy walking
+steadily round and round the mast. Now is that
+child moving in a circle, or is he not? Yes, he is.
+No, he is not. He walks in a circle as regards the
+position of the mast, which remains always the center
+of his pathway. But his movement <i>in space</i> is never
+a circle, since he constantly advances, and does not
+once return to his starting-point. You see how the
+two facts are possible side by side. Being carried
+forward by the ship, with no effort of his own, the
+forward motion does not interfere with the circling
+motion. Each is performed independently of the
+other.</p>
+
+<p>It is the same with the earth and the planets.<span class="pagenum" id="Page_128">[Pg 128]</span>
+The sun, by force of his mighty attraction, bears
+them along wherever he goes—no exertion on their
+part, so to speak, being needed. That motion does
+not in the least interfere with their steady circling
+round the sun.</p>
+
+<p>Just as—to use another illustration—the earth,
+turning on her axis, bears through space a man standing
+on the Equator at the rate of one thousand miles
+an hour. But this uniform movement, unfelt by himself,
+does not prevent his walking backwards, or forwards,
+or in circles, as much as he will.</p>
+
+<p>So, also, a bird in the air is unconsciously borne
+along with the atmosphere, yet his freedom to wheel
+in circles for any length of time is untouched.</p>
+
+<p>A few words about the orbits of the planets. I
+have more than once remarked that these pathways
+are, in shape, not circles, but ellipses. A circle is a
+line drawn in the shape of a ring, every part of which
+is at exactly the same distance from the center-point
+or focus. But an ellipse, instead of being, like a circle,
+perfectly round, is oval in shape; and instead of having
+only one focus, it has two foci, neither being exactly
+in the center. Foci is the plural word for focus.
+If an ellipse is only slightly oval—or slightly <i>elliptical</i>—the
+two foci are near together. The more oval or
+<i>eccentric</i> the ellipse, the farther apart are the two foci.</p>
+
+<p>You may draw a circle in this manner. Lay a
+sheet of white paper on a board, and fix a nail through
+the paper into the board. Then pass a loop of thread—say
+an inch or an inch and a half in length—round
+the nail, and also round a pencil, which you hold.
+Trace a line with the pencil, keeping the loop tight,<span class="pagenum" id="Page_129">[Pg 129]</span>
+so that the distance of your line from the nail will be
+always equal, and when it joins you have a circle.
+The nail in the center is the focus of the circle.</p>
+
+<p>To draw an ellipse, you must fix <i>two</i> nails. Let
+them be about half an inch apart; pass a loop over
+both of them, and again placing a pencil point within
+the loop, again trace a line carefully all round, keeping
+the thread drawn tight. This time an oval instead
+of a circle will appear. By putting the nails nearer
+together or farther apart, you may vary as you will
+the shape of the ellipse.</p>
+
+<p>In the orbits of the earth and the planets, all of
+which are ellipses in shape, the sun is not placed in
+the exact center, but in one of the two foci, the second
+being empty. So at one time of the year the
+planet is nearer to the sun than at another time. Our
+earth is no less than three millions of miles nearer in
+winter than she is in summer—speaking of the winter
+and summer of the northern hemisphere. Three millions
+of miles is so tiny a piece out of ninety-three
+millions of miles, that it makes little or no difference
+in our feelings of heat or cold.</p>
+
+<p>The orbits of the comets are ellipses also, but ellipses
+often so enormously lengthened out, that the two
+foci are almost—if one may so speak—at the two <i>ends</i>
+of the oval. To draw a good comet orbit, you must
+fix the two nails on your paper some five or six
+inches apart, with a loop of thread just large enough to
+slip over them both, and to allow the pencil to pass
+round them. When your ellipse is drawn, you must
+picture the sun in the place of one of the two nails,
+and you will see how, in their pathways, the comets<span class="pagenum" id="Page_130">[Pg 130]</span>
+at one time pass very near the sun, and at another
+time travel very far away from him.</p>
+
+<div class="figcenter" id="f21">
+<img src="images/fig21.jpg" alt="size">
+<p class="caption">COMPARATIVE SIZE OF THE PLANETARY WORLDS.</p>
+</div>
+
+<p>It is generally found in families, not only that the
+parent or head of the family has great influence over
+all the members, but that each member has influence<span class="pagenum" id="Page_131">[Pg 131]</span>
+over each other member. Brother influences brother,
+and sister influences sister.</p>
+
+<p>This, too, we find in the Solar System. Not only
+does the sun, by his powerful attraction, bind the
+whole family together, but each member of the family
+attracts each other member. True, the force of
+the sun’s attraction is overpowering in amount compared
+with others. The sun attracts the planets, and
+the planets attract the sun; but their feeble pulling is
+quite lost in the display of his tremendous strength.</p>
+
+<p>Among themselves we see the power more plainly.
+The earth attracts the moon, keeping her in constant
+close attendance; and the moon attracts the earth, causing
+a slight movement on her part, and also causing the
+tides of the sea. Each planet has more or less power
+to hinder or help forward his nearest brother-planet.
+For instance, when Jupiter on his orbit draws near
+the slower Saturn on his orbit, Saturn’s attraction
+pulls him on, and makes him move faster than usual;
+but as soon as he gets ahead of Saturn then the same
+attraction pulls him back, and makes him go more
+slowly than usual. Jupiter has the same influence
+over Saturn; and so also have Saturn and Uranus over
+one another, or Uranus and Neptune.</p>
+
+<p>In early days astronomers were often greatly puzzled
+by these quickened and slackened movements,
+which could not be explained. Now the “perturbations”
+of the planets, as they are called, are understood
+and allowed for in all calculations. Indeed, it
+is by means of this very attraction that Neptune was
+discovered, and the planets have actually been weighed.
+What a wonderful difference we find in this picture<span class="pagenum" id="Page_132">[Pg 132]</span>
+of the Solar System, as we now know it to be, from
+the old-world notion of our earth as the center of the
+universe!</p>
+
+<p>When we think of all the planets, and of the magnificent
+sun; when we pass onward in imagination
+through space, and find our sun himself merely one
+twinkling star amid the myriads of twinkling stars
+scattered broadcast through the heavens, while planets
+and comets have sunk to nothing in the far distance,—then
+indeed we begin to realize the unutterable
+might of God’s power! Why, our earth and all
+that it contains may be regarded as but one grain of
+dust in the wide universe.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_133">[Pg 133]</span></p>
+
+<h2 class="nobreak" id="c12">CHAPTER XII.</h2>
+</div>
+
+<p class="c sp">MORE ABOUT THE SUN.</p>
+
+
+<p><span class="smcap large">Not</span> among the least of the wondrous things of
+creation are the tremendous disturbances taking place
+upon the surface of the sun—that raging, roaring sea
+of flame.</p>
+
+<p>A good many explanations have been from time to
+time offered as to the dark spots seen to move across
+the face of the sun. Some one or more of these explanations
+may be true; but we know little about the
+matter. A sun-spot does not commonly consist of
+merely one black patch. There is the dark center,
+called the <i>umbra</i>—plural, <i>umbræ</i>. There is the grayish
+part surrounding the umbra, called the <i>penumbra</i>.
+Also, in the center of the umbra there is sometimes
+observable an intensely black spot, called the <i>nucleus</i>.
+Sometimes a spot is made up of nucleus and umbra
+alone, without any penumbra. Sometimes it is made
+of penumbra alone, without any umbra. Sometimes
+in one spot there are several umbræ, with the gray
+penumbra round the whole, and gray bridges dividing
+the umbræ.</p>
+
+<p>The enormous size of these spots has been already
+described in an earlier chapter. Fifty thousand to
+one hundred thousand miles across is nothing unusual.
+In the year 1839 a spot was seen which measured no
+less than one hundred and eighty-six thousand miles
+in diameter.</p>
+
+<p><span class="pagenum" id="Page_134">[Pg 134]</span></p>
+
+<p>One explanation proposed was, that the sun might
+be a cool body, covered over with different envelopes
+or dense layers of cloudy form, one above another.
+The inside envelope—or, as some say, the inside atmosphere—would
+then be thick and dull-colored,
+protecting the solid globe within and reflecting light,
+but having none of its own. The next envelope
+would be one mass of raging, burning gases—the
+<i>photosphere</i>, in fact. The outer envelope would be a
+transparent, surrounding atmosphere, lighted up by
+the sea of fire within. A sun-spot would then consist
+of the tearing open of one or more of these envelopes,
+so as to give glimpses of the gray, inner atmosphere,
+or even of the dark, cool globe at the center.</p>
+
+<p>There may be some truth in this explanation; but
+the notion of a cool and dark body within is now
+pretty well given up. The apparent blackness of a
+spot-nucleus does not prove actual blackness or absence
+of heat. A piece of white-hot iron, held up
+against the sun, looks black; and it may be merely
+the contrast of the glowing photosphere which makes
+the nucleus seem so dark. It is even believed that
+the blackest parts may be the most intensely hot
+of all.</p>
+
+<p>Another proposed explanation was of dark clouds
+floating in the sun’s atmosphere. There, again, are
+found difficulties, particularly in the fact that, as the
+spots move across the sun, the changes which regularly
+take place in their appearance make it pretty
+clear that their shape is not flat, but hollow and cave-like.
+The changes here spoken of are seeming
+changes of shape, caused by change of position.<span class="pagenum" id="Page_135">[Pg 135]</span>
+There are also real changes constantly taking place.
+Although the spots often keep their general outlines
+long enough to be watched across the face of the sun,
+and even to be known again after spending nearly a
+fortnight hidden on the other side, still they are far
+from being fixed in form.</p>
+
+<div class="figcenter" id="f22">
+<img src="images/fig22.jpg" alt="sun-spot">
+<p class="caption">A TYPICAL SUN-SPOT.</p>
+</div>
+
+<p>The alterations are at times not only very great,
+but very rapid. Sometimes in a single hour of watching,
+an astronomer can see marked movement going<span class="pagenum" id="Page_136">[Pg 136]</span>
+on—as you or I might in an hour observe movements
+slowly taking place in a high layer of clouds. For
+movement to show at all in one hour, at so immense
+a distance, proves that the actual rate of motion must
+be very great.</p>
+
+<p>The first great fact which was got from the study
+of these spots was this, that this great sun is very
+much like our own earth, in so far as it rotates on an
+axis in exactly the same way that our earth does. Not
+only do the spots change their position on the face of
+the sun, in consequence of the sun’s rotation on its
+axis, but they change very much from day to day, and
+even from hour to hour; so that we have evidence not
+only that the sun is rotating like our earth, but that
+the atmosphere of the sun is subjected to most tremendous
+storms—storms so tremendous, in fact, that
+the fiercest cyclones on our own earth are not for one
+moment to be compared with them. The fact that
+the spots do really move with the sun, and are really
+indentations, saucer-like hollows, in the photosphere,
+is shown by the appearance, which is always presented
+by a spot when it is near the edge of the sun. You
+know if you take a dinner-plate, and look it full in
+the face, it is round; but if you look at it edgeways,
+it is not round. Take two different views of the same
+spot: In one, you look the sun-spot straight in the face,
+and you see into it and can learn all about it; but in
+the other, when it has nearly gone round the corner,
+and is disappearing on the sun’s edge, you see it in
+the same way that you would see a plate looked at
+edgeways.</p>
+
+<p>These sun-cyclones must indeed be of terrific force<span class="pagenum" id="Page_137">[Pg 137]</span>
+and extent, compared with anything we see on earth.
+It was calculated that the speed of movement perceived
+in one spot was about three hundred and sixty-three
+miles each second.</p>
+
+<p>And still all this is nothing, or almost nothing, in
+comparison with the real power of the sun! The
+liquid state of the ocean; the gaseous state of the atmosphere;
+the currents of the sea; the raising of the
+clouds, the rains, storms, streams, rivers; the calorific
+value of all the forests of the globe and all the coal-mines
+of the earth; the motion of all living beings;
+the heat of all humanity; the stored-up power in
+all human muscles, in all the manufactories, in all
+the guns,—all that is almost nothing compared
+with that of which the sun is capable. Do we
+think that we have measured the solar power
+by enumerating the effects which it produces on
+the earth? Error! profound, tremendous, foolish
+error! This would be to believe still that this star has
+been created on purpose to illuminate terrestrial humanity.
+In reality, what an infinitesimal fraction of
+the sun’s total radiation the earth receives and utilizes!
+In order to appreciate it, let us consider the distance
+of ninety-three millions of miles which separates us
+from the central star, and at this distance let us see
+what effect our little globe produces, what heat it intercepts.
+Let us imagine an immense sphere <i>traced at
+this distance from the sun</i>, and entirely surrounding it.
+Well, on this gigantic sphere, the spot intercepted by
+our little earth is only equivalent to the fraction
+<sup>1</sup>/<sub>2,138,000,000</sub>; that is to say, that the dazzling solar hearth
+radiates all round it through immensity a quantity of<span class="pagenum" id="Page_138">[Pg 138]</span>
+light and heat two thousand one hundred and thirty-eight
+million times more than that which we receive,
+and of which we have just now estimated the stupendous
+effects. The earth only stops in its passage the
+<i>two thousand millionth part of the total radiation</i>.</p>
+
+<p>Sometimes the storms or outbursts come in the
+shape of a bright spot instead of a dark one.</p>
+
+<div class="figcenter" id="f23">
+<img src="images/fig23.jpg" alt="eruption">
+<p class="caption">A SOLAR ERUPTION.</p>
+</div>
+
+<p>Two astronomers were one day watching the sun
+from two different observatories, when they saw such
+an event take place. An intense and dazzling spot of
+light burst out upon the surface of the sun—so intense,
+so dazzling, as to stand quite apart from the
+radiant photosphere. To one astronomer it looked
+like a single spot, while the other saw two spots close
+together. In about a minute the light grew more
+dim, and in five minutes all was over. But in those
+five minutes the spot or spots had traveled a distance
+of thirty-five thousand miles.</p>
+
+<p><span class="pagenum" id="Page_139">[Pg 139]</span></p>
+
+<p>It was a very remarkable thing that the <i>magnets</i>
+on earth—those delicate little needles which point so
+steadily yet perseveringly towards the North Pole—seemed
+to be strongly agitated by the distant solar
+outburst. This brings us to another interesting fact.</p>
+
+<p>The spots on the sun are not always the same in
+number. Sometimes they are many, sometimes they
+are few. Long and close watching has made it clear
+that they pass through a regular <i>order</i> of changes:
+some years of many spots being followed by other
+years of less and less spots; then some years of very
+few spots being followed by other years of more and
+more spots,—decrease and increase being seemingly
+regular and alternate.</p>
+
+<p>This turn or <i>cycle</i> of changes—from more to less,
+and then from less to more again—is found to run its
+course about once in every eleven years, with some
+variations.</p>
+
+<p>Now, it has long been known that the magnetic-needle
+goes through curious variations. Though we
+speak of it as pointing always north, yet it does not
+always so point exactly. Every day the needle is
+found to make certain tiny, delicate motions, as if
+faintly struggling to follow the daily movements of
+the sun—just a little towards the east, or just a little
+towards the west. These tiny motions, having been
+long watched and measured, were found to go through
+a regular course of changes—some years more, and
+some years less, waxing and waning by turns. It was
+discovered that the course of changes from more to
+less, and from less to more again, took place in about
+eleven years.</p>
+
+<p><span class="pagenum" id="Page_140">[Pg 140]</span></p>
+
+<p>These two things, you see, were quite independent
+of one another. Those who watched the sun-spots
+were not thinking of the magnets, and those who
+watched the magnets were not thinking of the sun-spots.
+But somebody did at last happen to think of
+both together. He was laughed at, yet he took the
+trouble carefully to compare the two. And, strange
+to say, he found that these two periods in the main
+agreed—the eleven years of alternate changes in the
+number of sun-spots, and the eleven years of alternate
+changes in the movements of the magnetic-needle.
+When the spots are most, the needle moves most.
+When the spots are least, the needle moves least.
+So much we know. But to explain the why and the
+wherefore is beyond our power.</p>
+
+<p>This study of the magnetism of our wandering
+planet is very interesting, and one which is still very
+little known. Here is a weak needle, a slip of magnetic
+iron, which, with its restless and agitated finger,
+incessantly seeks a region near the north. Carry this
+needle in a balloon up to the higher aerial regions, where
+human life begins to be extinguished; shut it up in a
+tomb closely separated from the light of day; take it down
+into the pit of a mine, to more than a thousand yards in
+depth,—and incessantly, day and night, without fatigue
+and without rest, it watches, trembles, throbs, seeks
+the point which attracts it across the sky, through the
+earth, and through the night. Now—and here is a
+coincidence truly filled with notes of interrogation—the
+years when the oscillation of this innocent little
+steel wire is strongest are the years when there are
+more spots, more eruptions, more tempests in the sun;<span class="pagenum" id="Page_141">[Pg 141]</span>
+and the years when its daily fluctuations are weakest
+are those when we see in the day-star neither spots,
+eruptions, nor storms. Does there exist, then, a magnetic
+bond between the immense solar globe and our
+wandering abode? Is the sun magnetic? But the
+magnetic currents disappear at the temperature of red-hot
+iron, and the incandescent focus of light is at a
+temperature incomparably higher still. Is it an electrical
+influx which is transmitted from the sun to the
+earth across a space of ninety-three millions of miles?
+On September 1, 1859, two astronomers—Carrington
+and Hodgson—were observing the sun, independently
+of each other; the first on a screen which
+received the image; the second directly through a telescope,—when,
+in a moment, a dazzling flash blazed out
+in the midst of a group of spots. This light sparkled
+for five minutes above the spots without modifying
+their form, as if it were completely independent, and
+yet it must have been the effect of a terrible conflagration
+occurring in the solar atmosphere. Each observer
+ascertained the fact separately, and was for an
+instant dazzled. Now, here is a surprising coincidence:
+at the very moment when the sun appeared inflamed
+in this region the magnetic instruments of the Kew
+Observatory, near London, where they were observing,
+manifested a strange agitation; the magnetic
+needle jumped for more than an hour as if infatuated.
+Moreover, a part of the world was on that day and
+the following one enveloped in the fires of an aurora
+borealis, in Europe as well as in America. It was
+seen almost everywhere,—at Rome, at Calcutta, in
+Cuba, in Australia, and in South America. Violent<span class="pagenum" id="Page_142">[Pg 142]</span>
+magnetic perturbations were manifested, and at several
+points the telegraph-lines ceased to act. Why
+should these two curious events not be associated with
+each other? A similar coincidence was observed on
+August 3, 1872, by Professor Charles A. Young, of
+Princeton, N. J.: a paroxysm in the solar chromosphere,
+magnetic disturbances everywhere.</p>
+
+<p>There is a very singular appearance seen upon the
+sun which must not be passed over without mention.
+Some astronomers speak of the whole surface as being
+<i>mottled</i> all over with a curious rough look when examined
+through a powerful telescope. This “mottling”
+is described by various observers in various ways.
+One speaks of “luminous spots shaped like rice-grains.”
+Another, of “luminous spots resembling
+strokes made with a camel’s-hair pencil.” Another,
+of “luminous objects or granules.” Others, of “multitudes
+of leaves,” “nodules,” “crystalline shapes,”
+“leaves or scales, crossing one another in all directions,
+like what are called spills in the game of spillikens.”
+They have also been pictured as “certain
+luminous objects of an exceedingly definite shape and
+general uniformity of size, whose form is that of the
+oblong leaves of a willow-tree.” These cover the whole
+disk of the sun, excepting the space occupied by the
+spots, in countless millions, and lie crossing each other
+in every imaginable direction.</p>
+
+<p>In size they are said to be about one thousand miles
+long, by two or three hundred broad, but they vary a
+good deal. Where there is a spot, the willow-leaves
+at its edge are said to point pretty regularly towards
+the center. Whether they are, as they seem to be,<span class="pagenum" id="Page_143">[Pg 143]</span>
+solid in form; whether they are, as some suppose, the
+chief source of the sun’s light and heat; whether they
+lie on his surface or float in his atmosphere; what is
+their real nature, and what is their real use,—about
+these questions we are at present quite in the dark.</p>
+
+<p>We have next to
+think a little more
+about the edge or
+limb of the sun,
+and the stormy
+flames and outburst
+there seen.
+Until quite lately
+the only time for
+observing such appearances
+was during
+a total eclipse
+of the sun. Lately,
+by means of the
+new instrument
+called the “spectroscope,”
+it has been
+found possible to
+take observations when no eclipse is going on.</p>
+
+<div class="figright" id="f24">
+<img src="images/fig24.jpg" alt="sun-flames">
+<p class="caption">SUN-FLAMES, MAY 3, 1892.</p>
+</div>
+
+<p>A few words of explanation as to eclipses of the
+sun seem needful, before going further. An eclipse
+of the sun is caused simply by the round body of the
+moon passing exactly between the sun and the earth,
+so as to hide the sun from us.</p>
+
+<p>Let there be a candle on the table, while you stand
+near. The rays of light from the candle fall upon
+your face. Now move slowly, to and fro, a round ball<span class="pagenum" id="Page_144">[Pg 144]</span>
+between you and the candle. So long as it is not precisely
+in the line between—so long as it is a little
+higher, or a little lower, or a little to one side—then
+you can still see the flame. Once you let the ball come
+just between the light and your eyes, and you see it no
+more. In other words the candle-flame is eclipsed—hidden,
+veiled, cut off—by the ball.</p>
+
+<p>It may seem curious at first sight that the moon,
+which is very small compared with the sun, should
+have power to cover the sun. But remember the difference
+of the distance. The sun is very far, and the
+moon is very near. Any small object very near will
+easily hide from your sight a large object at a considerable
+distance. You may hold up a shilling-piece
+at arm’s length, and make it cover from sight a man,
+or even a house, if the latter be far enough away.
+The sun at a distance of ninety-three millions of miles,
+and the moon at a distance of two hundred and forty
+thousand miles, have to our vision the same seeming
+size. So, when the moon glides between, her round
+face just about covers the sun’s round face.</p>
+
+<p>If the moon were traveling exactly in the same
+plane as the plane of the earth’s orbit, an eclipse would
+be a very common affair indeed. But the plane of the
+moon’s orbit being not quite the same as the plane of
+the earth’s orbit, she passes sometimes a little above,
+and sometimes a little below, the exact spot where
+she would hide the sun’s rays from us. Now and
+then, at certain intervals, she goes just between. And
+so well is the moon’s path in the heavens understood
+that astronomers can tell us, long years beforehand,
+the day and the hour an eclipse will take place.</p>
+
+<p><span class="pagenum" id="Page_145">[Pg 145]</span></p>
+
+<p>An eclipse of the sun is sometimes partial, sometimes
+total, sometimes annular. In a partial eclipse,
+the moon does indeed pass between, but only so as to
+hide from us <i>part</i> of the sun. She is a little too low,
+or a little too high, to cover his face. In a total
+eclipse, the moon covers the sun completely, so that
+for a few minutes the bright photosphere seems blotted
+out from the heavens, a black round body, surrounded
+by light, taking its place. In an annular
+eclipse, the moon in like manner crosses the sun, but
+does not succeed in covering him entirely, a rim of
+bright photosphere showing round the black moon.
+For in an annular eclipse, the moon, being a little
+farther away from the earth than at the time of a
+total eclipse, has too small a disk quite to hide the
+sun’s disk.</p>
+
+<p>The blackness of the moon during an eclipse is
+caused by the fact that her bright side is turned towards
+the sun, and her dark side toward us. An
+eclipse of the sun can take place only at new moon,
+never at full moon. At her full, the moon is outside
+the earth’s orbit, away from the sun, and can not by
+any possibility pass between.</p>
+
+<p>Eclipses, like comets, have always been interpreted
+as the indication of inevitable calamities.
+Human vanity sees the finger of God making signs
+to us on the least pretext, as if we were the end and
+aim of universal creation. Let us mention, for example,
+what passed even in France, with reference to
+the announcement of an eclipse of the sun, on August
+21, 1560. For one, it presaged a great overthrow of
+States and the ruin of Rome; for another, it implied<span class="pagenum" id="Page_146">[Pg 146]</span>
+another universal deluge; for a third, nothing less
+would result than a conflagration of the globe; finally,
+for the less excited, it would infect the air. The belief
+in these terrible effects was so general that, by
+the express order of the doctors, a multitude of frightened
+people shut themselves up in very close cellars,
+well heated and perfumed, in order to shelter themselves
+from these evil influences. Petit relates that
+the decisive moment approached, that the consternation
+was at its height, and that a parish priest of the
+country, being no longer able to confess his parishioners,
+who believed their last hour had come, was
+obliged to tell them in a sermon “not to be so much
+hurried, seeing that, on account of the wealth of the
+penitents, the eclipse had been postponed for a fortnight.”
+These good parishioners found no more difficulty
+in believing in the postponement of the eclipse
+than they had in believing in its unlucky influence.</p>
+
+<p>History relates a crowd of memorable acts on which
+eclipses have had the greatest influence. Alexander,
+before the battle of Arbela, expected to see his army
+routed by the appearance of a phenomenon of this
+kind. The death of the Athenian general Nicias and
+the ruin of his army in Sicily, with which the decline
+of the Athenians commenced, had for their cause an
+eclipse of the moon. We know how Christopher Columbus,
+with his little army, threatened with death by
+famine at Jamaica, found means of procuring provisions
+from the natives by depriving them in the evening
+of the light of the moon. The eclipse had scarcely
+commenced when they supplied him with food. This
+was the eclipse of March 1, 1504. We need not relate<span class="pagenum" id="Page_147">[Pg 147]</span>
+other facts of this nature, in which history abounds,
+and which are known to every one.</p>
+
+<p>Eclipses no longer cause terror to any one, since we
+know that they are a natural and inevitable consequence
+of the combined motions of the three great
+celestial bodies—the sun, the earth, and the moon;
+especially since we know that these motions are regular
+and permanent, and that we can predict, by means
+of calculation, the eclipses which will be produced in
+the future as well as recognize those which have occurred
+in the past.</p>
+
+<p>The following description of the total eclipse of
+1860 will be found interesting. Mr. Lowe, who observed
+it at Santander, Spain, thus writes:</p>
+
+<p>“Before totality commenced, the colors in the sky
+and on the hills were magnificent beyond all description.
+The clear sky in the north assumed a deep
+indigo color, while in the west the horizon was first
+black like night. In the east the clear sky was very
+pale blue, with orange and red, like sunrise. On the
+shadow creeping across, the deep blue in the north
+changed, like magic, to pale, sunrise tints of orange
+and red, while the sunrise appearance in the east had
+changed to indigo. The darkness was great; the
+countenances of men were of a livid pink. The
+Spaniards lay down, and their children screamed with
+fear; fowls hastened to roost, ducks clustered together,
+pigeons dashed against the houses; flowers
+closed; many butterflies flew as if drunk, and at last
+disappeared. The air became very humid, so much
+so that the grass felt to one of the observers as if recently
+rained upon.”</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_148">[Pg 148]</span></p>
+
+<h2 class="nobreak" id="c13">CHAPTER XIII.</h2>
+</div>
+
+<p class="c sp">YET MORE ABOUT THE SUN.</p>
+
+
+<p><span class="smcap large">Having</span> seen something of storms taking place on
+the sun’s photosphere, we must next give our attention
+to storms taking place at his edge. But it should
+be remembered that the said edge, far from being a
+mere rim to a flat surface, is a kind of horizon-line—is,
+in fact, just that part of the photosphere which is
+passing out of or coming under our sight. The surface
+there is, in kind, the same as the surface of the
+broad disk facing us. In watching outbursts at the
+edge of the sun, we have a side view instead of a
+bird’s-eye view.</p>
+
+<p>In the year 1871, Professor Charles A. Young, of
+Princeton, was looking at a large hydrogen cloud on
+the edge of the sun. When I speak of a “cloud,” it
+must not be supposed that anything like a damp,
+foggy, earthly cloud is meant. This solar cloud was a
+huge mass of red-hot gas, about one hundred thousand
+miles long, rising to a height of fifty thousand
+miles from the sun’s surface, and appearing to rest
+on glowing pillars of fire.</p>
+
+<p>The professor, while watching, was called away for
+half an hour. He came back, expecting to find things
+much as he had left them. Instead of this, a startling
+change had taken place. The whole mass of
+glowing fire seemed to have been actually “blown to
+shreds” by some tremendous outburst from below.<span class="pagenum" id="Page_149">[Pg 149]</span>
+In place of the motionless cloud were masses of scattered
+fire, each from about four thousand to fourteen
+thousand miles long, and a thousand miles wide.</p>
+
+<p>As the professor gazed, these “bits” of broken
+cloud rose rapidly upwards, away from the surface of
+the sun. When I say “rapidly,” I mean that the real
+movement, which the professor could calculate, was
+rapid. The seeming movements were of course slow,
+and over a small space. The actual motions were not
+tardy, for in ten minutes these huge, fiery cloud-pieces
+rushed upwards to a height of two hundred thousand
+miles from the edge of the sun, moving at a rate of at
+least one hundred and sixty-seven miles each second.
+Gradually they faded away.</p>
+
+<p>But what caused this sudden change? Just before
+the professor was interrupted, he had noticed a curious
+little brilliant lump—a sort of suspicious thunder-cloud
+appearance—below the quiet, bright cloud. And
+after this tremendous shattering, the little bright lump
+rose upwards into a huge mass of rolling flame, reaching
+like a pyramid to a height of fifty thousand miles.
+In the course of a few minutes these enormous flames
+could be seen to move and bend, and to curl over their
+gigantic tips. But they did not last long. At half-past
+twelve the professor had been called away; by
+half-past two the rolling flames completely vanished.</p>
+
+<p>Now, whatever may be the full explanation of this
+sight, there is no doubt that on that day was observed
+from earth a tremendous outburst, compared with
+which our mightiest volcanoes are like the sputtering
+of a farthing dip beside a roaring furnace. The awful
+force and greatness of such a solar eruption are<span class="pagenum" id="Page_150">[Pg 150]</span>
+more than we can possibly picture to ourselves. At
+our distance we may catch a faint glimpse of what is
+going on, and calculate speed of movement. But
+vividly to realize the actual terrific grandeur of what
+took place is past our power.</p>
+
+<p>Possibly this was much the same kind of outburst
+as that seen by the two English astronomers; only
+theirs was a bird’s-eye view, as it were, looking down
+on the top of the sight, while the professor had a side-view,
+certainly much the best for observation.</p>
+
+<p>It does not follow from what he saw that the eruption
+must have taken place exactly at the “edge” of
+the sun. Probably it happened near the edge. All
+he could say, was that the flames rose fifty thousand
+miles, and the pieces of cloud were carried two hundred
+thousand miles, away from the edge. The eruption
+may have begun on the other side of the sun, at
+any distance from the horizon-edge where it first became
+visible to earthly eyes.</p>
+
+<p>Also, while the professor found that the shattered
+cloudlets moved at a rate of about one hundred and
+sixty-seven miles each second, it is calculated that the
+first fearful outburst must have caused movement,
+near the surface of the sun, at a rate of at least three
+hundred miles each second. Probably the hydrogen
+cloud was borne upwards along with a vast mass of
+fragments flung out from the sun. We are here upon
+doubtful ground; but this tremendous power of eruption
+in the sun, and of driving matter out of and away
+from his surface, should not be forgotten.</p>
+
+<p>Though such a sun-storm as that just described is
+not often to be seen, yet there are at all times certain<span class="pagenum" id="Page_151">[Pg 151]</span>
+strange red prominences, or glowing flames, rising up
+here and there from the sun’s “limb.” Doubtless they
+rise also from other parts of the photosphere, though
+they are only visible to us when near enough to the
+edge to stand out beyond it.</p>
+
+<p>Seen during an eclipse, these prominences have
+clear, sharp outlines, and are usually bright rose-red
+in color. They are described as sometimes wide and
+low, sometimes tall and slender; sometimes jagged,
+sometimes regular; sometimes keeping long the same
+shape, sometimes changing quickly in a few minutes.
+They are said to be like flames, like mountains, like
+the teeth of a saw, like icebergs, like floating cloudlets.</p>
+
+<p>As to their height, from fifty to eighty thousand
+miles is nothing unusual. We must not speak of
+Mont Blanc or Mount Everest here. Jupiter placed
+bodily on the surface of the sun, beside such a fire-mountain,
+would not far overtop it. The earth, Venus,
+Mars, and Mercury, would lie like little toy-balls at its
+foot. And these are common-sized sun-flames. One
+was measured which reached to the enormous height
+of two hundred thousand miles. The spectroscope
+shows these solar prominences or jets to be made—at
+least in part—of burning hydrogen gas.</p>
+
+<p>Beyond the sierra or chromatosphere—that border
+of rippling, crimson flame-billows round the edge of
+the sun, with red flame-mountains rising out of it
+here and there—beyond these, stretches the corona.
+The corona, as seen from earth, is a bright, far-reaching
+glory of light, shining round the sun in a total
+eclipse. The moon then comes between the sun and<span class="pagenum" id="Page_152">[Pg 152]</span>
+the earth, her dark, round body creeping over the face
+of the sun till the bright photosphere is completely
+covered. But the sierra and the tall, red flames stand
+out from behind the black moon, and the beautiful,
+soft corona-light stretches far beyond.</p>
+
+<div class="figcenter" id="f25">
+<img src="images/fig25.jpg" alt="corona">
+<p class="caption">SOLAR CORONA AND PROMINENCE.</p>
+</div>
+
+<p>It was long doubted whether the corona really belonged
+to the sun or to the moon. There seems now
+no doubt that it is a part of the sun.</p>
+
+<p>Various descriptions of the corona have been
+given at different times, as observed during different<span class="pagenum" id="Page_153">[Pg 153]</span>
+eclipses. It has been seen as a steady, beamy, white
+cloud behind the moon, showing no flickering. It has
+been seen marked with bright lines of light, and seeming
+to move rapidly round and round. It has been
+seen silvery white, sending off long streams of brightness.
+It has been seen in the form of white light,
+with bluish rays running over it. It has been seen
+with entangled jets of light, like “a hank of thread in
+disorder.” It has been seen silvery-white again, with
+a faint tinge of greenish-violet about the outer edge.
+It has been seen from a high mountain-top as a mass
+of soft, bright light, “through which shot out, as if
+from the circumference of the moon, straight, massive,
+silvery rays, seeming distinct and separate from each
+other, to a distance of two or three diameters of the
+lunar disk, the whole spectacle showing as upon a
+background of diffused, rose-colored light.”</p>
+
+<p>Majestic, indeed, are the proportions of some of
+those mighty flames which leap from the surface of
+the sun, yet these flames flicker, as do our terrestrial
+flames, when we allow them time comparable to their
+gigantic dimensions. Drawings of the same prominence
+often show great changes in a few hours, or even
+less. The magnitude of the changes could not be less
+than many thousands of miles, and the actual velocity
+with which such masses move is often not less than
+one hundred miles a second. Still more violent are
+the solar convulsions, which some observers have been
+so fortunate as to behold, when from the sun’s surface,
+as from a mighty furnace, vast incandescent masses
+are projected upwards. All indications point to the
+surface of the sun as the seat of the most frightful<span class="pagenum" id="Page_154">[Pg 154]</span>
+storms and tempests, in which the winds sweep along
+incandescent vapors.</p>
+
+<p>The corona consists of two parts—the inner and
+brighter corona, the outer and fainter corona. The
+shape of the whole seems to change much at different
+times. The outer edge is usually blurred and indistinct,
+fading gently away.</p>
+
+<p>Many explanations have been suggested. At one
+time the corona was supposed to be a solar atmosphere,
+reflecting light like our own atmosphere. Some
+have thought the light might be caused by countless
+myriads of meteorite systems, revolving in the close
+neighborhood of the sun. Some suppose it may be
+owing, in part at least, to solar eruptions, and the
+pouring outward of burning gas and matter. But our
+knowledge of the true nature of the corona is yet in
+its infancy.</p>
+
+<p>A few closing words as to the size and weight of
+the sun. In diameter, eight hundred and fifty-eight
+thousand miles, and in bulk equal to one million two
+hundred and eighty thousand earths, his weight is in
+proportion less. Our earth is about four times as
+dense as the sun. If her size were increased to the
+sun’s size, her density being the same as now, she
+would be very much heavier than the sun, and would
+attract much more strongly. Still, though the sun is
+of lighter materials than the earth, his immense size
+gives him weight equal to seven hundred and fifty
+times as much as all the planets put together.</p>
+
+<p>The attraction on the surface of the sun is also
+very great—so great that we can hardly picture it to
+ourselves. If life exists there at all—supposing it<span class="pagenum" id="Page_155">[Pg 155]</span>
+possible that any kind of life can be in such a fiery
+atmosphere—it must be life very different from any
+known in this world. A man who on earth weighs
+one hundred and sixty pounds, and walks lightly erect,
+would, on the sun, lie helplessly bound to the ground,
+crushed by his own overpowering weight. It is said
+that a cannon-ball, reposing on the sun, if lifted one
+inch and allowed to fall, would dash against the
+ground with a speed three times greater than that of
+our fastest express-trains. For weight on earth is
+merely caused by the amount of force with which the
+earth draws downward a body towards herself—a
+force greater or less according to the density of that
+body. So weight on the sun would be immensely
+increased by his immensely greater power of attraction.</p>
+
+<div class="figcenter" id="f26">
+<img src="images/fig26.jpg" alt="size">
+<p class="caption">COMPARATIVE SIZE OF THE EARTH AND SUN.</p>
+</div>
+
+<p><span class="pagenum" id="Page_156">[Pg 156]</span></p>
+
+<p>It is an interesting question how far the sun’s attractive
+influence reaches effectually through space.
+The nearer a body is to the sun, the greater the attraction
+which he exercises over it. At the distance
+of the planet Mercury, a speed of twenty-nine miles
+each second is needful to overcome or balance it sufficiently
+for the planet to remain in his orbit. At the
+distance of the planet Neptune, about three miles
+each second is enough. If a planet were journeying
+at four times the distance of Neptune, the speed would
+need to be not over two miles each second, lest the
+planet should break loose and wander away. But
+even two miles a second is no mean speed—more
+than seven thousand miles an hour. If we come to
+speak of that which we on earth call rapid motion,
+we shall gain a clearer idea as to the extent of the
+sun’s power.</p>
+
+<p>Suppose a planet were traveling through space at
+the rate of one of our fastest express-trains—sixty
+miles an hour. It has been calculated that, unless
+the sun’s attraction were interfered with and overpowered
+by some nearer sun, the said planet, though
+placed at a distance ten or twelve times as great as
+that of the far-off star Alpha Centauri, would still be
+forced by the sun’s attraction to journey round him in
+a closed orbit. At such a speed it would not be free
+to wander off into the depths of space.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_157">[Pg 157]</span></p>
+
+<h2 class="nobreak" id="c14">CHAPTER XIV.</h2>
+</div>
+
+<p class="c sp">MORE ABOUT THE MOON.</p>
+
+
+<p><span class="smcap large">From</span> a globe all fire, all energy, all action, we
+come to a globe silent, voiceless, changeless, lifeless.
+So, at least, the moon seems to us. But it will not do
+to speak too confidently.</p>
+
+<p>True, we can find no trace of an atmosphere in the
+moon. If there is any atmosphere at all, it must be
+so thin as to be less than that which we on earth
+count as actually none. We pump away the air from
+a glass inclosure in an air-pump, and say the glass
+is empty. Only it is not quite empty. There is always
+just a very little air remaining, though so little
+that fire would not burn and animals could not live in
+it. Some believe that air, up to that amount, may be
+found in the moon. But this is much the same as to
+say there is none at all. For, of course, with either
+no air or so very little air, life can not possibly exist
+on the moon. We can not imagine such a thing for a
+moment. That is just how the matter stands. We
+“can not imagine,” and therefore we conclude it to be
+an impossibility. As if we knew a hundredth part of
+the possibilities in any one corner of God’s great universe!
+As if our being unable to picture a thing
+proves that thing not to exist!</p>
+
+<p>Suppose we had always lived in tropical heat, and
+had never seen, known, or heard of such a fact as life
+in Arctic snows. Should we consider it a thing possible?<span class="pagenum" id="Page_158">[Pg 158]</span>
+Suppose we had always lived on dry land, with
+never a sight of sea or river or pond, and never a
+proof that animal life could exist under water—aye,
+and that some living animals may be suffocated by
+air, just as other living animals are suffocated by
+water. Should we not, in our wisdom, reason out
+such a state of affairs to be utterly impossible?</p>
+
+<p>There <i>may</i> be no life on the moon. It <i>may</i> be that
+she is now passing through a dead, cold, blasted stage,
+either at the close of some past history, or in preparation
+for some future history—or both. But, on the
+other hand, it <i>may</i> be that the moon is no less full of
+life than the earth; only the life must be different in
+kind, must be something which we do not know any
+thing at all about.</p>
+
+<p>The moon is very much smaller than the earth.
+Her diameter is about two-sevenths of the earth’s diameter;
+her entire surface is about two twenty-sevenths
+of the earth’s surface; her size is about two
+ninety-ninths of the earth’s size; and her whole weight
+is about one-eightieth of the earth’s weight. Attraction
+or gravitation on the surface of the moon is very
+different from what it is on the earth. Her much
+smaller bulk greatly lessens her power of attraction.
+While a man from earth would, on the surface of
+the sun—supposing he could exist there at all—lie
+helpless, motionless, and crushed by his own weight,
+he would on the moon find himself astonishingly light
+and active. A leap over a tall house would be nothing
+to him.</p>
+
+<div class="figcenter" id="f27">
+<img src="images/fig27.jpg" alt="moon">
+<p class="caption">THE MOON—AN EXPIRED PLANET.</p>
+</div>
+
+<p>The moon, unlike the sun, has no light or heat of
+her own to give out. She shines merely by reflected
+<span class="pagenum" id="Page_159">[Pg 159]</span>light. Rays of sunlight falling upon her, rebound
+thence, and find their way earthward. This giving of
+reflected light is not a matter all on one side. We
+yield to the moon a great deal more than she yields
+to us. Full earth, seen from the moon, covers a<span class="pagenum" id="Page_160">[Pg 160]</span>
+space thirteen times as large as full moon seen from
+earth.</p>
+
+<p>Perhaps you may have noticed, soon after new
+moon, when a delicate crescent of silver light shows
+in the sky, that within the said crescent seems to lie
+the body of a round, dark moon, only not perfectly
+dark. It shows a faint glimmer. That glimmer is
+called earth-shine. The bright crescent shines with
+reflected sunlight. The dim portion shines with reflected
+earth-light. What a journey those rays have
+had! First, leaving the sun, flashing through ninety-three
+millions of miles to earth, rebounding from earth
+and flashing over two hundred and forty thousand
+miles to the dark shaded part of the moon, then
+once more rebounding and coming back, much wasted
+and enfeebled, across the same two hundred and forty
+thousand miles, to shine dimly in your eyes and mine.
+The popular description of this particular view of the
+moon is “the old moon in the arms of the new.”</p>
+
+<p>Now about the <i>phases</i> of the moon; that is, her
+changes from “new” to “full,” and back again to
+“new.” If the moon were a starlike body, shining
+by her own light, she would always appear to be
+round. But as she shines by reflected sunlight, and
+as part of her bright side is often turned away from
+us, the size and shape of the bright part seem to vary.
+For, of course, only that half of the moon which is
+turned directly towards the sun is bright. The other
+half turned away is dark, and can give out no light at
+all, unless it has a little earth-shine to reflect.</p>
+
+<p>As the moon travels round the earth, she changes
+gradually from new to full moon, and then back to<span class="pagenum" id="Page_161">[Pg 161]</span>
+new again. “New moon” is when the moon, in her
+orbit, comes between the sun and the earth. The
+half of her upon which the sun shines is turned away
+from us, and only her dark side is towards us. So at
+new moon she is quite invisible. It is at new moon
+that an eclipse of the sun takes place, when the
+moon’s orbit carries her in a line precisely between
+sun and earth.</p>
+
+<p>Passing onwards round the earth, the moon, as we
+get a little glimpse of her shining side, first shows a
+slender sickle of light, which widens more and more
+till she reaches her first quarter. She is then neither
+between earth and sun, nor outside the earth away
+from the sun, but just at one side of us, passing over
+the earth’s own orbit. Still, as before, half her body
+is lighted up by the sun. By this time <i>half</i> the bright
+part and <i>half</i> the dark part are turned towards us; so
+that, seeing the bright quarter, we name it the “first
+quarter.”</p>
+
+<p>On and on round us moves the moon, showing
+more light at every step. Now she passes quite outside
+the earth’s orbit, away from the sun. Not the
+slightest chance here of an eclipse of the sun, though
+an eclipse of the moon herself is quite possible. But
+more of that presently. As she reaches a point in a
+line with earth and sun—only generally a little higher
+or lower than the plane of the earth’s orbit—her
+round, bright face, shining in the sun’s rays, is turned
+exactly towards us. Then we have “full moon.”</p>
+
+<p>Still she goes on. Once more her light narrows
+and wanes, as part of her bright half turns away.
+Again at the “last quarter,” as at the first, she occupies<span class="pagenum" id="Page_162">[Pg 162]</span>
+a “sideways” position, turning towards us half
+her bright side and half her dark side. Then she
+journeys on, with lessening rim of light, till it vanishes,
+and once more we have the dark, invisible
+“new moon.”</p>
+
+<p>It was these phases and aspects of the moon which
+formerly gave birth to the custom of measuring time
+by months, and by weeks of seven days, on account of
+the return of the moon’s phases in a month, and because
+the moon appears about every seven days, so to
+say, under a new form. Such was the first measure of
+time; there was not in the sky any signal of which
+the differences, the alternations, and the epochs were
+more remarkable. Families met together at a time
+fixed by some lunar phase.</p>
+
+<p>The new moons served to regulate assemblies, sacrifices,
+and public functions. The ancients counted
+the moon from the day they first perceived it. In order
+to discover it easily, they assembled at evening
+upon the heights. The first appearance of the lunar
+crescent was watched with care, reported by the high
+priest, and announced to the people by the sound of
+trumpets. The new moons which correspond with the
+renewal of the four seasons were the most solemn; we
+find here the origin of the “ember weeks” of the
+Church, as we find that of most of our festivals in the
+ceremonies of the ancients. The Orientals, the Chaldeans,
+Egyptians, and Jews religiously observed this
+custom.</p>
+
+<p>An eclipse of the sun has already been described.
+An eclipse of the moon is an equally simple matter.
+An eclipse of the sun is caused by the dark, solid<span class="pagenum" id="Page_163">[Pg 163]</span>
+body of the moon passing just between earth and sun,
+hiding the sun from us, and casting its shadow upon
+the earth. An eclipse of the moon is also caused by
+a shadow—the shadow of our own earth—falling upon
+the moon.</p>
+
+<p>Here again, if the plane of the moon’s orbit were
+the same as ours, eclipses of the moon would be very
+common. As it is, her orbit carries her often just a
+little too high or too low to be eclipsed, and it is only
+now and then, at regular intervals, that she passes
+through the shadow of the earth.</p>
+
+<p>If a large, solid ball is hung up in the air, with
+bright sunlight shining on it, the sunlight will cast a
+<i>cone of shadow</i> behind the ball. It will throw, in a
+direction just away from the sun, a long, round shadow,
+the same as the ball at first, but tapering gradually off
+to a point. If the ball is near the ground, a round
+shadow will rest there, almost as large as the ball.
+The higher the ball is placed, the smaller will be the
+round shadow, till at length, if the ball be taken far
+enough upwards, the shadow will not reach the ground
+at all. Our earth and all the planets cast just such
+tapering cones of dark shadow behind them into space.
+The cone always lies in a direction away from the sun.</p>
+
+<p>It is when the moon comes into this shadow that
+an “eclipse of the moon” takes place. Sometimes
+she only dips half-way into it, or just grazes along
+the edge of it, and that is called a “partial eclipse.”
+Sometimes she goes in altogether, straight through
+the midst of the shadow, so that the whole of her
+bright face for a short time grows quite dark. Then
+we have a “total lunar eclipse.”</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_164">[Pg 164]</span></p>
+
+<h2 class="nobreak" id="c15">CHAPTER XV.</h2>
+</div>
+
+<p class="c sp">YET MORE ABOUT THE MOON.</p>
+
+
+<p><span class="smcap large">There</span> are two ways of thinking about the moon.
+One way is to consider her as merely the earth’s
+attendant satellite. The other way is to consider
+her as our sister-planet, traveling with us round the
+central sun.</p>
+
+<p>The first is the more common view; but the second
+is just as true as the first.</p>
+
+<p>For the sun does actually pull the moon towards
+himself, with a very much stronger pulling than that
+of the earth. The attraction of the sun for the moon
+is more than double the attraction of the earth for the
+moon. If it were not that he pulls the earth quite as
+hard as he pulls the moon, he would soon overpower
+the earth’s attraction, and drag the moon away from
+us altogether.</p>
+
+<p>People are often puzzled about the orbit or pathway
+of the moon through the heavens. For in one
+sense they have to think of her as traveling round
+and round in a fixed orbit, with the earth in the
+center. In another sense they have to think of her
+as always journeying onwards with the earth in her
+journey round the sun, and thus never returning to
+the same point.</p>
+
+<p>There are two ways of meeting this difficulty.
+First of all, remember that the one movement does
+not interfere with the other. Just as in the case of<span class="pagenum" id="Page_165">[Pg 165]</span>
+the earth traveling round the sun, and also traveling
+onward with him through space; just as in the case
+of a boy walking round and round a mast, and also
+being borne onwards by the moving vessel,—so it is
+here. The two movements are quite separate and
+independent of each other. As regards the earth
+alone, the moon journeys round and round perpetually,
+not in a circle, but in a pathway which comes
+near being an ellipse. As regards the actual <i>line</i>
+which the moon’s movements may be supposed to
+draw in space, it has nothing elliptical about it, since
+no one point of it is ever reached a second time by
+the moon.</p>
+
+<p>But according to this last view of the question, nobody
+ever can or will walk in a circle or an oval.
+Take a walk round your grass-plot, measuring your
+distance carefully at all points from the center. Is
+that a circle? All the while you moved, the surface
+of the earth was rushing along and bearing you with
+it, and the whole earth was hurrying round the sun,
+and was being also carried by him in a third direction.
+Whatever point in space you occupied when
+you started, you can <i>never fill that particular part of
+space again</i>. The two ends of your so-called circle
+can never be joined.</p>
+
+<p>But then you may come back to the same point <i>on
+the grass</i>, as that from which you started. And this
+is all that really signifies. Practically you have
+walked in a circle. Though not a circle as regards
+space generally, it is a circle as regards the earth.
+So also the moon comes back to the same point <i>in
+her orbit round the earth</i>. Letting alone the question<span class="pagenum" id="Page_166">[Pg 166]</span>
+of space, and considering only the earth, the moon
+has—roughly speaking—journeyed in an ellipse.
+You may, however, look at this matter in quite another
+light. Forget about the moon being the earth’s
+satellite, and think of earth and moon as two sister-planets
+going round the sun in company.</p>
+
+<p>The earth, it is true, attracts the moon. So, also,
+the moon attracts the earth; though the far greater
+weight of the earth makes her attraction to be far
+greater. If earth and moon were of the same size,
+they would pull each other with equal force.</p>
+
+<p>But though the pull of the earth upon the moon is
+strong, the pull of the sun upon the moon is more
+than twice as strong. And greatly as the earth influences
+the moon, yet the actual center of the moon’s
+orbit is the sun, and not the earth. Just as the earth
+travels round the sun, so also the moon travels round
+the sun.</p>
+
+<p>The earth travels steadily in her path, being only
+a little swayed and disturbed by the attraction of the
+moon. The moon on the contrary, while traveling
+in her orbit, is very much swayed and disturbed indeed
+by the earth’s attraction. In fact, instead of
+being able to journey straight onwards like the earth,
+her orbit is made up of a succession of delicate curves
+or scallops, passing alternately backwards and forwards
+over the orbit of the earth. Now she is behind the
+earth; now in front of the earth; now between earth
+and sun; now outside the earth away from the sun.
+The order of positions is not as here given, but each
+is occupied by her in turn. Sometimes she moves
+quickly, sometimes she moves slowly, just according<span class="pagenum" id="Page_167">[Pg 167]</span>
+to whether the earth is pulling her on or holding her
+back. Two hundred and forty thousand miles sounds a
+good deal. That is the distance between earth and
+moon. But it is, after all, a mere nothing, compared
+with the ninety-three millions of miles which separate
+the sun from the earth and moon.</p>
+
+<p>If we made a small model, with the sun in the
+center, and the earth and moon traveling a few inches
+off, only one slender piece of wire would be needed
+to represent the path of earth and moon together.
+For not only would the earth and the moon be so
+small as to be quite invisible, but the whole of the
+moon’s orbit would have disappeared into the thickness
+of the single wire. This question of the moon’s
+motions is in its nature intricate, and in its details
+quite beyond the grasp of any beginner in astronomy.
+But so much at least may be understood, that
+though the earth’s attraction powerfully affects the
+moon, and causes in her motions <i>perturbations</i>, such as
+have been already spoken about as taking place among
+the planets, yet that in reality the great controlling
+power over the moon is the attraction of the sun.</p>
+
+<p>The tides of the ocean are chiefly brought about
+by the moon’s attraction. The sun has something to
+do with the matter, but the moon is the chief agent.
+This action of the moon can best be seen in the southern
+hemisphere, where there is less land. As the
+moon travels slowly round the earth, her attraction
+draws up the yielding waters of the ocean in a vast
+wave which travels slowly along with her. The same
+pulling which thus lifts a wave on the side of the
+earth towards the moon, also pulls the earth gently<span class="pagenum" id="Page_168">[Pg 168]</span>
+<i>away from</i> the water on the opposite side, and causes
+a second wave there. The parts of the ocean between
+these two huge waves are depressed, or lower in level.
+These two waves on the opposite sides of the earth
+sweep steadily onwards, following the moon’s movements,—not
+real, but seeming movements, caused by
+the turning of the earth upon her axis.</p>
+
+<p>Once in every twenty-four hours these wide waves
+sweep round the whole earth in the southern ocean.
+They can not do the same in the north, on account of
+the large continents, but offshoots from the south
+waves travel northwards, bringing high-tide into every
+sea and ocean inlet. If there were only one wave,
+there would be only one tide in each twenty-four
+hours. As there are two waves, there are two tides,
+one twelve hours after the other. In the space between
+these two high-tides we have low-tide.</p>
+
+<p>Twice every month we have very high and very low
+tides. Twice every month we have tides not so high
+or so low. The highest are called “spring-tides,” and
+the lowest “neap-tides.” When the moon is between
+us and the sun, or when she is “new moon,” there are
+spring-tides; for the pull or attraction of sun and
+moon upon the ocean act exactly together. It is the
+same at full moon, when once more the moon is in a
+straight line with earth and sun. But at the first and
+last quarters, when the moon has her <i>sideways</i> position,
+and when the sun pulls in one direction and the
+moon pulls in another, each undoes a little of the
+other’s work. Then we only have neap-tides; for the
+wave raised is smaller, and the water does not flow so
+high upon our shores.</p>
+
+<p><span class="pagenum" id="Page_169">[Pg 169]</span></p>
+
+<p>In speaking of the surface of the moon, we are
+able only to speak about one side. The other is
+entirely hidden from us. This is caused by the
+curious fact that the moon turns on her axis and
+travels round the earth in exactly the same length of
+time. One-half of the moon is thus always turned towards
+us, though of that half we can only see so much
+as is receiving the light of the sun. But the half
+turned in our direction is always the same half.
+One part of the moon—not quite so much as half,
+though always the same portion—is turned away from
+us. A small border on each side of that part becomes
+now and then visible to us, owing to certain movements
+of the earth and the moon.</p>
+
+<p>What sort of a landscape may lie in the unknown
+district, it is idle to imagine. Many guesses have
+been made. Some have supposed it possible that air
+<i>might</i> be found there; that water <i>might</i> exist there;
+that something like earthly animals <i>might</i> live there.
+It is difficult to say what may not be, in a place about
+which we know nothing whatever. But judging from
+our earthly experience, nothing seems more unlikely
+than that air, water, clouds, should be entirely banished
+from over one-half of a globe, and collected together
+in the space remaining.</p>
+
+<p>We are on safer ground when we speak about that
+part of the moon which is turned towards us. For we
+can say with confidence that if any atmosphere exist
+there, it must be in thickness less than the two-thousandth
+part of our earthly atmosphere. It seems
+equally clear that water also must be entirely wanting.
+The tremendous heat of the long lunar day would<span class="pagenum" id="Page_170">[Pg 170]</span>
+raise clouds of vapor, which could not fail to be visible.
+But no such mistiness ever disturbs the sharply-defined
+outline of the moon, and no signs of water action are
+seen in the craggy mountains and deep craters.</p>
+
+<div class="figcenter" id="f28">
+<img src="images/fig28.jpg" alt="crater">
+<p class="caption">THE LUNAR CRATER COPERNICUS.</p>
+</div>
+
+<p>The craters which honeycomb the surface of the
+moon are various in size. Many of the larger ones
+are from fifty to a hundred miles in diameter. These
+huge craters—or, as we may call them, deep circular
+plains—are surrounded by mighty mountain ramparts,
+rising to the height of thousands of feet.
+Usually they have in their center a sugar-loaf or<span class="pagenum" id="Page_171">[Pg 171]</span>
+cone-shape mountain, or even two or more such
+mountains, somewhat lower in height than the surrounding
+range. The sunset-lights upon certain of
+these distant mountain-peaks were first watched by
+Galileo through his telescope, and have since been
+seen by many an observer—intense brightness contrasting
+with intense blackness of shadow.</p>
+
+<p>In addition to her great craters, the moon seems
+to be thickly covered with little ones, many of them
+being as small as can be seen at all through a telescope.
+Whether these are all volcano-craters remains to be
+discovered. It is not supposed that any of them are
+now active. From time to time, signs of faint changes
+on the moon’s surface have been noticed, which it
+was thought might be owing to volcanic outbursts.
+Such an outburst as the worst eruptions of Mount
+Vesuvius would be invisible at this distance. But the
+said changes may be quite as well accounted for by
+the startling fortnightly variations of climate which
+the moon has to endure. The general belief now inclines
+to the idea that the moon-volcanoes are extinct,
+though no doubt there was in the past great volcanic
+activity there.</p>
+
+<p>A description has been given earlier of the rain of
+meteorites constantly falling to our earth, and only
+prevented by the atmosphere from becoming serious.
+But the moon has no such protecting atmosphere, and
+the amount of cannonading which she has to endure
+must be by no means small. Perhaps in past times,
+when her slowly-cooling crust was yet soft, these celestial
+missiles showering upon her may have occasionally
+made deep round holes in her surface.</p>
+
+<p><span class="pagenum" id="Page_172">[Pg 172]</span></p>
+
+<p>This is another guess, which time may prove to be
+true. Guesses at possible explanations of mysteries
+do no harm, so long as we do not accept them for
+truth without ample reason.</p>
+
+<div class="figcenter" id="f29">
+<img src="images/fig29.jpg" alt="brisk">
+<p class="caption">LUNAR ERUPTION—BRISK ACTION.</p>
+</div>
+
+<p>The origin of the lunar craters must be referred
+to some ancient epoch in the moon’s history. How
+ancient that epoch is we have no means of knowing;
+but in all probability the antiquity of the lunar craters
+is enormously great. At the time when the moon
+was sufficiently heated to have these vast volcanic
+eruptions, of which the mighty craters are the survivals,
+the earth must have been very much hotter
+than it is at present. It is not, indeed, at all unreasonable
+to believe that when the moon was hot enough
+for its volcanoes to be active, the earth was so hot that
+life was impossible on its surface. This supposition<span class="pagenum" id="Page_173">[Pg 173]</span>
+would point to an antiquity for the moon’s craters far
+too great to be estimated by the centuries and the
+thousands of years which are adequate for the lapse
+of time as recognized by the history of human events.
+It seems not unlikely that millions of years may have
+elapsed since the mighty craters of Plato or of Copernicus
+consolidated into their present form.</p>
+
+<div class="figcenter" id="f30">
+<img src="images/fig30.jpg" alt="feeble">
+<p class="caption">LUNAR ERUPTION—FEEBLE ACTION.</p>
+</div>
+
+<p>It will now be possible for us to attempt to account
+for the formation of the lunar craters. The
+most probable views on the subject are certainly those
+adopted by Mr. Nasmyth, as represented in the cuts,
+though it must be admitted that they are by no means
+free from difficulty. We can explain the way in which
+the rampart around the lunar crater is formed, and
+the great mountain which so often adorns the center
+of the plain. The first of these cuts contains an imaginary<span class="pagenum" id="Page_174">[Pg 174]</span>
+sketch of a volcanic vent on the moon in the
+days when the craters were active. The eruption is
+here in the full flush of its energy, when the internal
+forces are hurling forth a fountain of ashes or stones,
+which fall at a considerable distance from the vent; and
+these accumulations constitute the rampart surrounding
+the crater. The second cut depicts the crater in
+a later stage of its history. The prodigious explosive
+power has now been exhausted, and perhaps has been
+intermitted for some time. A feeble jet issues from
+the vent, and deposits the materials close around the
+orifice, and thus gradually raises a mountain in the
+center.</p>
+
+<p>Besides the craters and their surrounding barriers,
+there are ranges of mountains on the moon, and flat
+plains which were once named “seas,” before it was
+found that water did not exist there. Astronomers
+also see bright ridges, or lines, or cracks of light, hard
+to explain.</p>
+
+<p>One of the chief craters is called “Ptolemy,” and
+in size it is roughly calculated to be no less than one
+hundred and fourteen miles across. Another, “Copernicus,”
+is about fifty-six miles; and another,
+“Tycho,” about fifty-four miles. The central cone-mountain
+of Tycho is five thousand feet high. The
+crater of “Schickard” is supposed to be as much as
+one hundred and thirty-three miles in diameter.</p>
+
+<p>Astronomers have agreed to name these craters
+after the great discoverers who enlarged our knowledge
+of the solar and sidereal systems. It is fitting
+that these great names are suggested every time the
+moon is seen through a telescope. To Ptolemy we<span class="pagenum" id="Page_175">[Pg 175]</span>
+are indebted for what is known as “The Ptolemaic
+System of the Universe,” which makes the earth the
+center around which the sun, moon, planets, and stars
+all revolve, and explains the apparently erratic movements
+of the planets by supposing their orbits to be
+epicycles; that is, curves returning upon themselves
+and forming loops. Tycho Brahe was willing to allow,
+with Copernicus, that the planets all revolved around
+the sun; but he taught that both sun and planets
+turned around the earth.</p>
+
+<p>The system known as “The Copernican” is now
+known to be the only true one, and it is universally
+accepted. It is so called after Nicolaus Copernicus,
+who was born in Thorn, Prussia, February 19, 1473.
+He was educated for the Church, and studied medicine,
+but devoted himself especially to astronomy.</p>
+
+<p>Without being precisely a great genius, this quiet
+and thoughtful monk seems to have been wise far
+beyond the age in which he lived, and remarkable
+for his independence of mind. He had a “profound
+sagacity,” and a wide general grasp of scientific
+subjects.</p>
+
+<p>The extremely complicated and cumbrous nature
+of the Ptolemaic system appeared to his judgment
+hardly compatible with the harmony and simplicity
+elsewhere characteristic of nature. Moreover, he was
+impressed and perplexed by the very marked changes
+in the brilliancy of the planets at different seasons.
+These changes <i>now</i> are no difficulty at all. Venus,
+Mars, Jupiter, when on the same side of the sun as
+ourselves, are comparatively near to us, and naturally
+look much more bright in consequence of that nearness<span class="pagenum" id="Page_176">[Pg 176]</span>
+than when they are on the opposite side of the
+sun from ourselves. But under the Ptolemaic system,
+each planet was supposed to revolve round our earth,
+and to be always at about the same distance from us;
+therefore, why such variations in their brilliancy?</p>
+
+<div class="figcenter" id="f31">
+<img src="images/fig31.jpg" alt="copernicus">
+<p class="caption">NICOLAUS COPERNICUS.</p>
+</div>
+
+<p>During thirty-six long years he patiently worked
+out this theory, and during part of those thirty-six
+years he wrote the one great book of his lifetime, explaining
+the newer view of the Solar System which<span class="pagenum" id="Page_177">[Pg 177]</span>
+had taken hold of his reason and imagination. This
+book, named <i>De Revolutionibus Orbium Cœlestium</i>,
+or, “Concerning the Revolutions of the Celestial
+Spheres,” which came out only a few hours before his
+death, was dedicated to the Bishop of Rome—a little
+touch of worldly wisdom which doubtless staved off
+for a while the opposition of the Vatican.</p>
+
+<p>Copernicus was not the first who thought of interpreting
+the celestial motions by the theory of the
+earth’s motion. That immortal astronomer has taken
+care to give, with rare sincerity, the passages in the
+ancient writers from which he derived the first idea of
+the probability of this motion—especially Cicero, who
+attributed this opinion to Nicetas of Syracuse; Plutarch,
+who puts forward the names of Philolaus, Heraclides
+of Pontus, and Ecphantus the Pythagorean;
+Martianus Capella, who adopted, with the Egyptians,
+the motion of Mercury and Venus around the sun, etc.
+Even a hundred years before the publication of the
+work of Copernicus, Cardinal Nicolas of Cusa, in 1444,
+in his great theological and scientific encyclopedia,
+had also spoken in favor of the idea of the earth’s
+motion and the plurality of worlds. From ancient
+times to the age of Copernicus, the system of the
+earth’s immobility had been doubted by clear-sighted
+minds, and that of the earth’s motion was proposed
+under different forms. But all these attempts still
+leave to Copernicus the glory of establishing it definitely.</p>
+
+<p>Not content with merely admitting the idea of the
+earth’s motion as a simple arbitrary hypothesis, which
+several astronomers had done before him, he wished—and<span class="pagenum" id="Page_178">[Pg 178]</span>
+this is his glory—to demonstrate it to himself by
+acquiring the conviction by study, and wrote his book
+to prove it. The true prophet of a creed, the apostle
+of a doctrine, the author of a theory, is the man who,
+by his works, demonstrates the theory, makes the
+creed believed in, and spreads the doctrine. He is
+not the creator. “There is nothing new under the
+sun,” says an ancient proverb. We may rather say,
+Nothing which succeeds is entirely new. The newborn
+is unformed and incapable. The greatest things
+are born from a state of germ, so to say, and increase
+unperceived. Ideas fertilize each other. The sciences
+help each other; progress marches. Men often feel a
+truth, sympathize with an opinion, touch a discovery,
+without knowing it. The day arrives when a synthetical
+mind feels in some way an idea, almost ripe,
+becoming incarnate in his brain. He becomes enamored
+of it, he fondles it, he contemplates it. It grows
+as he regards it. He sees, grouping round it, a multitude
+of elements which help to support it. To him
+the idea becomes a doctrine. Then, like the apostles
+of good tidings, he becomes an evangelist, announces
+the truth, proves it by his works, and all recognize in
+him the author of the new contemplation of nature,
+although all know perfectly well that he has not invented
+the idea, and that many others before him have
+foreseen its grandeur.</p>
+
+<p>Such is the position of Copernicus in the history of
+astronomy. The hypothesis of the earth’s motion had
+been suggested long before his birth on this planet.
+This theory counted partisans in his time. But he—he
+did his work. He examined it with the patience<span class="pagenum" id="Page_179">[Pg 179]</span>
+of an astronomer, the rigor of a mathematician, the
+sincerity of a sage, and the mind of a philosopher.
+He demonstrated it in his works. Then he died without
+seeing it understood, and it was not till a century
+after his death that astronomy adopted it, and popularized
+it by teaching it. However, Copernicus is really
+the author of the true system of the world, and his
+name will remain respected to the end of time.</p>
+
+<p>The so-called “seas” on the moon are those large
+dark spots to be seen on its surface, in the shape of
+“eyes, nose, and mouth,” or of the famous old man
+with his bundle of sticks. The brighter parts are the
+more mountainous parts.</p>
+
+<p>The chief ranges of lunar mountains have been
+named by astronomers after mountains on earth, such
+as the Apennines, the Alps, the Caucasian range, the
+Carpathian and the Altai Mountains.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_180">[Pg 180]</span></p>
+
+<h2 class="nobreak" id="c16">CHAPTER XVI.</h2>
+</div>
+
+<p class="c sp">MERCURY, VENUS, AND MARS.</p>
+
+
+<p><span class="smcap large">Once</span> again we have to journey through the high-roads
+of the Solar System, paying a brief visit to each
+in turn of our seven chief brother-and-sister planets,
+and learning a few more leading facts about them.
+Having gone the same way before, it will not now seem
+quite so far.</p>
+
+<p>Busy, hurrying Mercury! we must meet him first
+in his wild rush through space. If he were to slacken
+speed for a single instant, he would begin to fall with
+fearful rapidity towards the sun. And if Mercury
+were to drop into one of those huge black chasms of
+rent furnace-flame on the sun’s surface, there would be
+a speedy end to his life as a planet.</p>
+
+<p>Mercury’s day is about the same length as our day,
+and his year is about one quarter the length of our
+year. If Mercury has spring, summer, autumn, and
+winter, each season must be extremely short; but this
+depends upon whether Mercury’s axis slopes like the
+earth’s axis—a matter difficult to find out. Mercury
+is always so near to the sun, that it is by no means
+easy to observe him well.</p>
+
+<p>We know more about his orbit than his axis. The
+earth’s orbit, as before explained, is not a circle, but
+an ellipse or oval. Mercury’s orbit is an ellipse also,
+and a much longer—or, as it is called, a more eccentric—ellipse.
+The earth is three millions of miles<span class="pagenum" id="Page_181">[Pg 181]</span>
+nearer to the sun at one time of the year, than six
+months before or after. Mercury is no less than fifteen
+millions of miles nearer at one time than another,
+which must make a marked difference in the amount
+of heat received.</p>
+
+<p>Even when the distance is greatest, the sun as seen
+from Mercury looks four and a half times as large as
+the sun we see. What a blazing splendor of light!
+It is not easy to imagine human beings living there,
+in such heat and glare, and with either no changes of
+season at all, or such very short seasons rapidly following
+one another. Mercury may, and very likely
+does, abound with living creatures, as much as the
+earth abounds with them; only one fancies they must
+be altogether a different kind of living creatures from
+any ever seen on earth. And yet we do not know. Man
+can so wonderfully adapt himself or be adapted to different
+climates on earth, from extreme heat to extreme
+cold, that we can not tell how far this adapting power
+may reach.</p>
+
+<p>Both Mercury and Venus seem to be enfolded in
+dense, cloud-laden atmospheres, rarely parting so as
+to allow us to get even a glimpse of the real planets
+within the thick, light-reflecting covering. Some
+have thought that a heavy, moist, protecting atmosphere
+may help to ward off the intense heat, and to
+make Mercury a more habitable place. Our earthly
+atmosphere is rather of a kind to store up heat, and
+to make us warmer than we should be without it; but
+there might be vapors differently constituted which
+might act in some other way. At all events, we know
+how easily God can have adapted either the planet<span class="pagenum" id="Page_182">[Pg 182]</span>
+to the creatures he meant to place there, or the creatures
+to the climate. “All things are possible” to
+him. The how and the what are interesting questions
+for us, but we must often be content to wait for an
+answer.</p>
+
+<p>A thick, gray ring or belt has been noticed round
+the small, black disk of Mercury, while it has passed
+between us and the sun. The edge of Mercury, seen
+against the bright photosphere beyond, would, if there
+were no atmosphere, be sharp and clear as the edge of
+the airless moon. This surrounding haze seems to
+show that Mercury has an atmosphere. The sunlight
+reflected from Mercury’s envelope of clouds shines at
+least as brightly as if it were reflected from his solid
+body.</p>
+
+<p>The small size of Mercury makes attraction on his
+surface much less than on earth. A lump of iron
+weighing on earth one pound, would weigh on Mercury
+only about seven ounces, or less than half as
+much. So a man would be a very light leaper indeed
+there, and an elephant might be quite a frolicsome
+animal. If there are star-gazers in Mercury, and if
+the cloud-laden atmosphere allows many clear views
+of the sky, the earth and Venus must both be beautiful
+to look upon. Each of the two would shine far
+more brightly than Jupiter, as seen at his best from
+earth.</p>
+
+<p>Like Mercury, Venus, the next planet, has an orbit
+lying inside our orbit. Mercury and Venus are always
+nearer to the sun than we are; and if Mercury
+and Venus traveled round the sun in orbits, the planes
+of which were exactly the same as the plane of the<span class="pagenum" id="Page_183">[Pg 183]</span>
+earth’s orbit, we should very often see them creeping
+over the surface of the sun. Not that they really
+“creep over” it; only, as they journey between the
+sun and us, we can see them pass like little black dots
+across the sun’s disk. This is the same thing as when
+the moon passes across the sun’s disk and eclipses it.
+But Mercury and Venus are too far away from us to
+cause any eclipse of the sun’s light.</p>
+
+<p>Mercury has given more trouble to astronomers
+than any other member of the system; for, owing to
+his proximity to the sun, he is usually lost in the
+solar glory, and is never seen in a dark part of the
+heavens, even at the time of his greatest distance.
+This circumstance, together with a small mass and an
+immense velocity, renders it difficult to catch and watch
+him. In high latitudes, where the twilight is strong
+and lengthened, while mists often overhang the horizon,
+the planet can seldom be seen with the naked eye.
+Hence an old astro-meteorologist contemptuously describes
+him as “a squirting lacquey of the sun, who
+seldom shows his head in these parts, as if he was in
+debt.” Copernicus lamented that he had never been
+able to obtain a sight of Mercury; and the French astronomer
+Delambre saw him not more than twice with
+the naked eye.</p>
+
+<p>The most favorable times for making observations
+are about an hour and three-quarters before sunrise in
+autumn, and after sunset in spring; but very clear
+weather and a good eye are required. At certain periods,
+when between the earth and the sun, on a line
+joining the centers of the two bodies, Mercury appears
+projected on the solar disk as a small, round, dark<span class="pagenum" id="Page_184">[Pg 184]</span>
+spot. This is called a <i>transit</i>, and would occur during
+every revolution if the plane of his orbit coincided
+with that of the orbit of the earth. But as one-half
+of his orbit is a little above that of the earth, and the
+other half a little below it, he passes above or below
+the sun to the terrestrial spectator, except at those intervals,
+when, being between us and the sun, he is
+also at one of the two opposite points where the planes
+of the respective orbits intersect each other. Then,
+stripped of all luster, the planet passes over the face
+of the great luminary as a black circular speck, affording
+evidence of his shining by reflected light, and
+of his spherical form.</p>
+
+<p>The first transit of Mercury recorded in history
+was predicted by Kepler, and witnessed by Gassendi,
+at Paris, on the morning of a cloudy day, the 7th of
+November, 1631. It was toward nine o’clock when he
+saw the planet; but owing to its extreme smallness,
+he was at first inclined to think it was a minute solar
+spot. It was then going off the sun; and made its
+final egress toward half-past ten. The observed time
+of the transit was nearly five hours in advance of the
+computed time. This was a very satisfactory accordance
+for that age between theory and observation; but
+it was the effect of a fortuitous combination of circumstances,
+rather than of computations founded upon
+well-established data. “The crafty god,” wrote Gassendi,
+in the peculiar style of his day, “had sought to
+deceive astronomers by passing over the sun a little
+earlier than was expected, and had drawn a veil of
+dark clouds over the earth in order to make his escape
+more effectual. But Apollo, knowing his knavish<span class="pagenum" id="Page_185">[Pg 185]</span>
+tricks from his infancy, would not allow him to pass
+altogether unnoticed. To be brief, I have been more
+fortunate than those hunters after Mercury who have
+sought the cunning god in the sun. I found him out,
+and saw him where no one else had hitherto seen
+him.” Since Gassendi’s time a number of transits
+have been observed.</p>
+
+<p>These crossings of the sun’s face, or “transits,” as
+they are called, have been important matters. The
+transit of Venus especially was once eagerly looked
+for by astronomers, since, by close observations of Venus’s
+movements and positions, the distance of the
+sun could at that time be better calculated than in any
+other way. Other methods are now coming into vogue.</p>
+
+<p>The transits of Venus are rare. Two come near
+together, separated by only eight years, and then for
+more than one hundred years the little dark body of
+Venus is never seen from earth to glide over the sun’s
+photosphere. There was a transit of Venus in the
+year 1761, and another in the year 1769. There was
+a transit of Venus in 1874, and another in 1882. At
+the last transits it was found that the sun, instead of
+being ninety-five millions of miles away, as astronomers
+thought, was only ninety-three millions of miles
+away. The reason why these transits happen so
+seldom, is that the orbits of Mercury and Venus lie in
+rather a different plane or level from the earth’s orbit.
+So, like the moon, though often passing between us
+and the sun, they generally go just a little higher or
+just a little lower than his bright face.</p>
+
+<p>Mercury and Venus show phases like the moon, although
+they do not circle round the earth as the moon<span class="pagenum" id="Page_186">[Pg 186]</span>
+does. These “phases,” or changes of shape, are probably
+never visible except through a telescope. It will
+be easier to think about the phases of Venus alone,
+than to consider both together. Her orbit lies within
+the earth’s orbit, and the earth and Venus travel round
+the sun—as do all the planets—in the same direction.
+But as Venus’s pathway is shorter than ours, and as
+her speed is greater, she is much the quickest about
+her yearly journey, and she overtakes us again and
+again at different points of our orbit in turn.</p>
+
+<div class="figleft" id="f32">
+<img src="images/fig32.jpg" alt="venus">
+<p class="caption">PHASES OF VENUS.</p>
+</div>
+
+<p>At one time
+she comes between
+us and
+the sun. That
+is her nearest
+position to us,
+and she is then
+only about
+twenty-five millions
+of miles distant.
+A beautiful sight she would be, but unfortunately
+her bright side is entirely turned away, and
+only her dark side is turned towards us. So then she
+is “new Venus,” and is invisible.</p>
+
+<p>At another time she is completely beyond the sun,
+and at her farthest position away from us. Her shining
+is quite lost in the sun’s rays coming between.
+And though we get a good view of her as “full Venus,”
+at a little to one side or the other, yet so great
+is her distance—as much as one hundred and fifty-seven
+millions of miles—that her size and brightness
+are very much lessened.</p>
+
+<p><span class="pagenum" id="Page_187">[Pg 187]</span></p>
+
+<p>Between these two nearest and farthest points, she
+occupies two middle distances, one on each side of
+the sun. Then, like the moon at her “quarters,” she
+turns to us only half of her bright side. But this is
+the best view of Venus that we have, as a brilliant,
+untwinkling, starlike form,—the Evening Star of ancients
+and of poets. Between these four leading positions
+Venus is always traveling gradually from one to
+another—always either waxing or waning in size and
+in brightness. Mercury passes through the same
+seeming changes.</p>
+
+<p>Inhabitants of Venus must have a glorious view of
+the earth, with her attendant moon. For just at the
+time when the two planets are nearest together, and
+when she is only “new Venus” to us, a dark and invisible
+body, the earth is “full earth” to Venus. The
+very best sight we ever have of Venus can not come
+near that sight. But if Mercury and Venus really are
+so often covered with heavy clouds as astronomers believe,
+this must greatly interfere with any habits of
+star-gazing.</p>
+
+<p>Venus and the earth have often been called twin-sister
+planets. There are many points of likeness between
+them. In size they differ little, and in length
+of day they are within an hour of being the same.
+Earth certainly has a companion-moon, and Venus, it
+is believed, has not. At one time several astronomers
+were pretty certain that they had caught glimpses of a
+moon; but the supposed moon has of late quite vanished,
+and nobody can say whether it ever really existed.
+Venus travels in an ellipse which comes nearer
+to being a circle than the orbit of any other planet.</p>
+
+<p><span class="pagenum" id="Page_188">[Pg 188]</span></p>
+
+<p>Mountain-shadows have been watched through the
+telescope, in Venus, as in the moon. Some astronomers
+have believed that they saw signs of very lofty
+mountains—as much as twenty-eight miles, or four
+times the height of our highest earthly mountains, but
+this requires confirmation.</p>
+
+<p>There is a good deal of uncertainty about the
+climate of Venus. The heat there must greatly surpass
+heat ever felt on earth—the sun being about
+double the apparent size of our sun, and pouring out
+nearly double the amount of light and heat that we
+receive.</p>
+
+<p>This difference may be met, as already stated, by a
+sheltering, cloudy atmosphere, or the inhabitants may
+have frames and eyesight suited to the increased glare
+and warmth.</p>
+
+<p>An atmosphere and water exist there as here.
+From what we have seen above of the rapid and violent
+seasons of this planet, we might think that the
+agitations of the winds, the rains, and the storms
+would surpass everything which we see and experience
+here, and that its atmosphere and its seas would
+be subject to a continual evaporation and precipitation
+in torrential rains—an hypothesis confirmed by its
+light, due, doubtless, to reflection from its upper
+clouds, and to the multiplicity of the clouds themselves.
+To judge by our own impressions, we should
+be much less pleased with this country than with our
+own, and it is even very probable that our physical
+organization, accommodating and complaisant as it is,
+could not become acclimatized to such variations of
+temperature. But it is not necessary to conclude from<span class="pagenum" id="Page_189">[Pg 189]</span>
+this that Venus is uninhabitable and uninhabited.
+We may even suppose, without exaggeration, that its
+inhabitants, organized to live in the midst of these
+conditions, find themselves at their ease, like a fish in
+water, and think that our earth is too monotonous and
+too cold to serve as an abode for active and intelligent
+beings.</p>
+
+<p>Of what nature are the inhabitants of Venus? Do
+they resemble us in physical form? Are they endowed
+with an intelligence analogous to ours? Do they pass
+their life in pleasure, as Bernardin de St. Pierre said;
+or, rather, are they so tormented by the inclemency of
+their seasons that they have no delicate perception,
+and are incapable of any scientific or artistic attention?
+These are interesting questions, to which we
+have no reply. All that we can say is, that organized
+life on Venus must be little different from terrestrial
+life, and that this world is one of those which resemble
+ours most. It should, then, be inhabited by vegetable,
+animal, and human races but little different from those
+which people our planet. As to imagining it desert
+or sterile—this is an hypothesis which could not arise
+in the brain of any naturalist. The action of the divine
+sun must be there, as in Mercury, still more fertile
+than his terrestrial work, already so wonderful.
+We may add that Venus and Mercury, having been
+formed after the earth, are relatively younger than our
+planet.</p>
+
+<p>It is believed also that the axis of Venus, instead
+of being slanted only as much as the earth’s axis, is
+tilted much more. Even if the tilting is less than
+some have supposed, it is probably very considerable.<span class="pagenum" id="Page_190">[Pg 190]</span>
+If Venus really does “lie over” in such a manner,
+certain startling changes of climate on its surface—unpleasant
+changes, according to our ideas—would
+take place.</p>
+
+<p>Like earth, Venus would have her two arctic regions,
+where a burning summer’s day would succeed
+a bitter winter’s night, each half a year in length.
+She would have also her tropical region—only in that
+region intense cold would alternate with intense heat,
+brief seasons of each in turn. And between the tropics
+and the arctic regions would lie wide belts, by turns
+entirely tropical and entirely arctic. The rapidity and
+severity of these changes, following one another in a
+year about as long as eight of our months, would
+seem to be too much for any human frame to endure.
+But it all rests upon an <i>if</i>. And we may be quite
+sure that <i>if</i> there are any manner of human beings
+in Venus, their frames are well suited to the climate
+of their world.</p>
+
+<p>Though Mars is one of the inner group of four
+small planets, divided by the zone of asteroids from
+the outer group of four great planets, yet he belongs
+to the outside set of Superior Planets. His orbit surrounds
+ours, being at all points farther off from the
+sun. Very slight “phases” have been seen in Mars.
+He turns to us, from time to time, just enough of his
+dark side to prove that he <i>has</i> a dark side, and that
+he does not shine like a star by his own light. But
+the phases on that planet are by no means marked as
+they are with Venus.</p>
+
+<p>Until lately it was believed that Mars possessed no
+moons. Two very small ones have, however, been<span class="pagenum" id="Page_191">[Pg 191]</span>
+lately found circling round him.<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">[2]</a> They have been
+named Deimos and Phobos, after the “sons of Mars”
+in Greek mythology. Deimos travels round Mars in
+thirty-nine hours, while Phobos performs the same
+journey in the astonishingly short period of seven
+hours and a half!</p>
+
+<div class="footnote">
+
+<p><a id="Footnote_2" href="#FNanchor_2" class="label">[2]</a> The discovery of the two moons is due to the agency of a
+woman. Professor Asaph Hall, of Washington City, was searching
+by the aid of the most powerful telescope which had yet been directed
+to Mars, and at the very moment when the planet was in the
+most favorable condition for observation. Having searched in
+vain during several evenings in August, 1877, he was about to give
+up, when Mrs. Hall begged him to search a little more. He did
+so, and on the night of the 11th he discovered the first of the
+satellites, and then on the 17th the second.</p>
+
+</div>
+
+<div class="figcenter" id="f33">
+<img src="images/fig33.jpg" alt="mars">
+<p class="caption">MARS AND THE PATH OF ITS SATELLITES.</p>
+</div>
+
+<p>We have here, then, a system very different from
+that of the earth and moon. But the most curious
+point is the rapidity with which the inner satellite of
+Mars revolves round its planet. This revolution is
+performed in seven hours, thirty-nine minutes, fifteen
+seconds, although the world of Mars rotates on itself
+in twenty-four hours, thirty-seven minutes—that is to<span class="pagenum" id="Page_192">[Pg 192]</span>
+say, this moon turns much more quickly than the
+planet itself. This fact is inconsistent with all the
+ideas we have had up to the present on the law of
+formation of the celestial bodies. Thus, while the
+sun appears to revolve in the Martian sky in a slow
+journey of more than twenty-four hours, the inner
+moon performs its entire revolution in a third of a
+day. It follows that <i>it rises in the west</i> and <i>it sets in
+the east</i>! It passes the second moon, eclipses it from
+time to time, and goes through all its phases in eleven
+hours, each quarter not lasting even three hours.
+What a singular world!</p>
+
+<p>These satellites are quite small—they are the
+smallest celestial bodies we know. The brightness
+of the planet prevents us from measuring them exactly.
+It seems, however, that the nearer is the
+larger, and shows the brightness of a star of the tenth
+magnitude, and that the second shines as a star of the
+twelfth magnitude. According to the most trustworthy
+photometric measures, the first satellite may
+have a diameter of 7.45 miles, and the second a
+diameter of 6.2 miles. <i>The larger of these two worlds
+is scarcely larger than Paris.</i> Should we honor
+them with the title of worlds? They are not even
+terrestrial continents, nor empires, nor kingdoms,
+nor provinces, nor departments. Alexander, Cæsar,
+Charlemagne, or Napoleon, might care but little
+to receive the scepter of such worlds. Gulliver might
+juggle with them. Who knows, however? The vanity
+of men being generally in the direct ratio of their
+mediocrity, the microscopical reasoning mites which
+doubtless swarm on their surface have also, perhaps,<span class="pagenum" id="Page_193">[Pg 193]</span>
+permanent armies, which mutilate each other for the
+possession of a grain of sand.</p>
+
+<p>These two little moons received from their discoverer
+the names of <i>Deimos</i> (Terror) and <i>Phobos</i>
+(Flight), suggested by the two verses of Homer’s
+“Iliad” which represent Mars descending on the earth
+to avenge the death of his son Ascalaphus:</p>
+
+
+<div class="poetry-container">
+<div class="poetry">
+  <div class="stanza">
+    <div class="verse indent0">“He ordered Terror and Flight to yoke his steeds,</div>
+    <div class="verse indent0">And he himself put on his glittering arms.”</div>
+  </div>
+</div>
+</div>
+
+
+<p><i>Phobos</i> is the name of the nearer satellite; <i>Deimos</i>,
+that of the more distant.</p>
+
+<p>The existence of these little globes had already
+been suspected from analogy, and thinkers had frequently
+suggested that, since the earth has one satellite,
+Mars should have two, Jupiter four, Saturn eight;
+and this is indeed the fact—though as Jupiter is now
+found to have <i>five</i> satellites, this arithmetical progression
+is upset. But as we experience too often in
+practice the insufficiency of these reasonings of purely
+human logic, we can not give them more value than
+they really possess. We might suppose in the same
+way now that Uranus has sixteen satellites, and Neptune
+thirty-two. This is possible; but we know nothing
+of them, and have not even the right to consider
+this proportion as probable. It is not the less curious
+to read the following passage, written by Voltaire in
+1750 in his masterpiece, the “Micromégas:”</p>
+
+<p>“On leaving Jupiter, our travelers crossed a space
+of about a hundred millions of leagues, and reached
+the planet Mars. They saw <i>two moons</i>, which wait on
+this planet, and which have escaped the gaze of astronomers.<span class="pagenum" id="Page_194">[Pg 194]</span>
+I know well that Father Castel wrote
+against the existence of these two moons; but I agree
+with those who reason from analogy. These good
+philosophers know how difficult it would be for Mars,
+which is so far from the sun, to get on with less than
+two moons. However this may be, our people found
+it so small that they feared they might not find anything
+to lie upon, and went on their way.”</p>
+
+<p>Here we have unquestionably a very clear prophecy,
+a rare quality in this kind of writing. The astronomico-philosophical
+romance of “Micromégas” has
+been considered as an imitation of Gulliver. Let us
+open the masterpiece of Swift himself, composed about
+1720, and we read, word for word, in Chapter III of
+the “Voyage to Laputa:”</p>
+
+<p>“Certain astronomers ... spend the greatest
+part of their lives in observing the celestial bodies,
+which they do by the assistance of glasses far excelling
+ours in goodness. For this advantage hath enabled
+them to extend the discoveries much farther
+than our astronomers in Europe; for they have made
+a catalogue of ten thousand fixed stars, whereas the
+largest of ours do not contain above one-third part of
+that number. They have likewise discovered two
+lesser stars, or satellites, which revolve about Mars,
+whereof the innermost is distant from the center of
+the primary planet exactly three of his diameters, and
+the outermost five. The former revolves in the space
+of ten hours, and the latter in twenty-one and a half;
+so that the squares of their periodical times are very
+near in the same proportion with the cubes of their
+distance from the center of Mars, which evidently<span class="pagenum" id="Page_195">[Pg 195]</span>
+shows them to be governed by the same law of gravitation
+that influences the other heavenly bodies.”</p>
+
+<p>What are we to think of this double prediction of
+the two satellites of Mars? Indeed, the prophecies
+which have been made so much of in certain doctrinal
+arguments have not always been as clear, nor
+the coincidences so striking. However, it is evident
+that no one had ever seen these satellites before 1877,
+and that there was in this hit merely the capricious
+work of chance. We may even remark that both the
+English and French authors have only spoken ironically
+against the mathematicians, and that in 1610, Kepler,
+on receiving the news of the discovery of the satellites
+of Jupiter, wrote to his friend Wachenfals that
+“not only the existence of these satellites appeared to
+him probable, but that doubtless there might yet be
+found two to Mars, six or eight to Saturn, and perhaps
+one to Venus and Mercury.” We can not, assuredly,
+help noticing that reasoning from analogy is here
+found on the right road. However this may be, this
+discovery truly constitutes one of the most interesting
+facts of contemporary astronomy.</p>
+
+<p>Mars is not only much smaller than the earth, but
+a good deal less dense in his “make.” His material is
+only about three-quarters as heavy as an equal amount
+of the earth’s material. A very heavy man on earth
+would be a most light and active individual on Mars.
+Gold taken from earth to Mars would weigh there no
+more than tin weighs upon earth.</p>
+
+<p>Mars has, it seems, an atmosphere, even as earth
+has. Of all the planets Mars, is the only one whose
+actual surface is discernible in the telescope. Mercury<span class="pagenum" id="Page_196">[Pg 196]</span>
+and Venus are so hidden by dense envelopes of
+clouds that the real planets within are only now and
+then to be dimly caught sight of. Jupiter and Saturn
+are so completely enwrapped in mighty masses of
+vapor, that we can not even be certain whether there
+are any solid bodies at all inside.</p>
+
+<p>But Mars can be studied. Here and there, it is
+true, clouds sweep over the landscape, hiding from
+view for a little while one continent or another, one
+sea or another, growing, changing, melting away, as
+do the clouds of earth. Still, though these clouds
+come and go, there are other markings on the surface
+of Mars which do not change. Or, rather, they only
+change so much as the continents and oceans of earth
+would seem to vary, if watched from another planet,
+as the daily movement of earth carried them from
+west to east, or as they might be hidden for a while
+by cloud-layers coming between. It has been curiously
+noted that these clouds over Mars form often in
+the morning and evening, and are afterwards dispersed
+by the heat of midday. Also there seems
+every reason to believe that rainfalls take place in
+Mars as upon earth.</p>
+
+<p>The red color of Mars is well known. This does
+not vanish in the telescope, but it is found that parts
+only have the red or orange hue, while other parts are
+dark and greenish. These are the markings which
+remain always the same, and they have been so
+closely examined that more is known about the geography
+of Mars than of any other world outside our
+own.</p>
+
+<p>Mars, at his nearest point, does not draw closer to<span class="pagenum" id="Page_197">[Pg 197]</span>
+us than forty millions of miles. At such a distance
+one must not speak too confidently. There are, however,
+many reasons for believing that the red portions
+are continents and that the green portions are oceans.</p>
+
+<p>The spectroscope has lately shown us that water
+does really exist in the atmosphere of Mars—unlike the
+dreary, waterless moon. So we no longer doubt that
+the cloudlike appearances are clouds, and that rain
+sometimes falls on Mars. If there is rain, and if there
+are clouds and vapor, there are probably oceans also.</p>
+
+<p>Two singular white spots are to be seen at the
+north and south poles, which we believe to be polar
+ice and snow. Somebody looking at our earth in like
+manner from a distance, would doubtless perceive two
+such white snow-spots. These two polar caps are
+seen to vary with the seasons. When the north pole
+of Mars is turned towards the sun, the white spot
+there grows smaller; and at the same time, the south
+pole of Mars being turned away from the sun, the
+white spot there grows larger. Again, when the south
+pole is towards the sun, and the north pole away from
+the sun, the white spot at the south is seen to be the
+smallest, and the white spot at the north is seen to
+be the largest. This is exactly what takes place in
+the summers and winters of our north and south poles.</p>
+
+<p>The markings of Mars have been so carefully studied,
+that at last a map has been made of the planet—a
+map of a world, never less than forty millions of
+miles away! Names have been given to the continents
+and oceans—such as Dawes Continent, Herschel
+Continent, De La Rue Ocean, Airy Sea, Huggins
+Inlet, and so on.</p>
+
+<p><span class="pagenum" id="Page_198">[Pg 198]</span></p>
+
+<p>Land and water seem to be very differently arranged
+on Mars from what they are on earth. Here
+we have about three times as much water as land, and
+to get from one continent to another without crossing
+the sea is in some cases impossible. But a traveler
+there might go most conveniently to and fro, hither
+and thither, to all parts of his world, either on land or
+on water, without any change. If he preferred water,
+he would never need to set foot on land; and if he
+preferred land, he would never need to enter a boat.
+The two are so curiously mingled together, narrow
+necks of land running side by side with long, narrow
+sea-inlets, that Atlantic and Pacific Oceans are unknown.</p>
+
+<p>Some have wondered whether the reddish color of
+the land may be caused by grass and trees being red
+instead of green. Very strange if so it were. But in
+that case, no doubt the inhabitants of Mars would
+find green just as trying to their eyesight, as we should
+find red trying to ours.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_199">[Pg 199]</span></p>
+
+<h2 class="nobreak" id="c17">CHAPTER XVII.</h2>
+</div>
+
+<p class="c sp">JUPITER.</p>
+
+
+<p><span class="smcap large">Passing</span> at one leap over the belt of tiny asteroids,
+about which we know little beyond their general movement,
+and the size and weight of a few among them,
+we reach at once the giant planet Jupiter: Mighty
+Jupiter, hurrying ever onward, with a speed, not indeed
+equal to that of Mercury or of our earth, yet eighty
+times as rapid as the speed of a cannon-ball! Think
+of a huge body, equal in bulk to twelve hundred
+earths, equal in weight to three hundred earths, rushing
+ceaselessly through space, at the rate of seven
+hundred thousand miles a day!</p>
+
+<p>Jupiter’s shape is greatly flattened at the poles.
+He spins rapidly on his axis, once in nearly ten hours,
+and has therefore a five hours’ day and a five hours’
+night. As the slope of his axis is exceedingly slight,
+he can boast little or no changes of season. The climate
+near the poles has never much of the sun’s heat.
+In fact, all the year round the sun must shine upon
+Jupiter much as he shines on the earth at the equinoxes.</p>
+
+<p>But the amount of light and heat received by Jupiter
+from the sun is only about one twenty-fifth part
+of that which we receive on earth; and the sun, as
+seen from Jupiter, can have but a small, round surface,
+not even one-quarter the diameter of the sun we see
+in the sky.</p>
+
+<p><span class="pagenum" id="Page_200">[Pg 200]</span></p>
+
+<p>When looked at with magnifying power, the bright,
+starlike Jupiter grows into a broad, softly-shining disk
+or plate, with flattened top and bottom, and five tiny,
+bright moons close at hand. Sometimes one moon is
+on one side, and four are on the other; sometimes
+two are one side and three on the other; sometimes
+one or more are either hidden behind Jupiter or passing
+in front of him. Jupiter has also curious markings
+on his surface, visible through a telescope. These
+markings often undergo changes; for Jupiter is no
+chill, fixed, dead world, such as the moon seems to be.</p>
+
+<div class="figcenter" id="f34">
+<img src="images/fig34.jpg" alt="jupiter">
+<p class="caption">GENERAL ASPECT OF JUPITER—SATELLITE AND ITS SHADOW.</p>
+</div>
+
+<p>There are dark belts and bright belts, usually running
+in a line with the equator, from east to west.<span class="pagenum" id="Page_201">[Pg 201]</span>
+Across the regions of the equator lies commonly a
+band of pearly white, with a dark band on either side
+of “coppery, ruddy, or even purplish” hue. Light
+and dark belts follow one after another, up to the
+north pole and down to the south pole.</p>
+
+<p>When we talk of “north and south poles” in the
+other planets, we merely mean those poles which
+point towards those portions of the starry heavens
+which we have chosen to call “northern” and “southern.”
+You know that all the chief planets travel
+round the sun in very nearly the same <i>plane</i> or flat
+surface that we do ourselves. That plane is called
+the “plane of the ecliptic.” Suppose that you had an
+enormous sheet of cardboard, and that in the middle
+of this cardboard the sun were fixed, half his body
+being above and half below. At a little distance, fixed
+in like manner in the card, would be the small body
+of the earth, half above and half below, her axis being
+in a slanting position. The piece of cardboard represents
+what is called in the heavens the <i>plane of the
+ecliptic</i>—an imaginary flat surface, cutting exactly
+through the middle of the sun and of the earth.</p>
+
+<p>If the planets all traveled in the same precise plane,
+they would all be fixed in the cardboard just like the
+earth, half the body of each above and half below.
+As they do not so travel, some would have to be placed
+a little higher, some a little lower, according to what
+part of their orbits they were on. This supposed
+cardboard “plane of the ecliptic” would divide the
+heavens into two halves. One half, containing the
+constellations of the Great Bear, the Little Bear, Cepheus,
+Draco, and others, would be called the Northern<span class="pagenum" id="Page_202">[Pg 202]</span>
+Heavens. One end of the earth’s axis, pointing just
+now nearly to the Polar Star, we name the North
+Pole; and all poles of planets pointing towards this
+northern half of the heavens, are in like manner
+named by us their north poles.</p>
+
+<p>With regard to west and east, lay in imagination
+upon this cardboard plane a watch, with its face upwards;
+remembering that all the planets and nearly
+all the moons of the Solar System are said both to
+spin on their axes, and to travel in their orbits round
+the sun, <i>from west to east</i>. Note how the hands of
+your watch would move in such a position. The
+“west to east” motions of planets and moons would
+be in exactly the opposite direction from what the motions
+of the watch-hands would be.</p>
+
+<p>To return to Jupiter. It is believed that these
+bands of color are owing to a heavy, dense atmosphere,
+loaded with vast masses of cloudy vapor. By
+the “size” of Jupiter, we really mean the size of this
+outside envelope of clouds. How large the solid body
+within may be, or whether there is any such solid
+body at all, we do not know. The extreme lightness
+of Jupiter, as compared with his great size, has caused
+strong doubts on this head.</p>
+
+<p>The white belts are supposed to be the outer side
+of cloud-masses shining in the sunlight. Travelers
+in the Alps have seen such cloud-masses, spreading
+over the whole country beneath their feet, white as
+driven snow, and shining in the sunbeams which they
+were hiding from villages below; or looking like soft
+masses of cotton-wool, from which the mountain-peaks
+rose sharply here and there.</p>
+
+<p><span class="pagenum" id="Page_203">[Pg 203]</span></p>
+
+<p>The dark spaces between seem to be rifts or breaks
+in the clouds. Whether, when we look at those dark
+spaces, we are looking at the body of Jupiter, or only
+at lower layers of clouds, is not known. But sometimes
+blacker spots show upon the dark cloud-belts,
+and this seems rather as if they were only lower layers
+of clouds, the black spots giving us peeps down
+into still lower and deeper layers, or else perhaps to
+the planet itself. These appearances remind one
+strongly of the sun-spots, each with its penumbra,
+umbra, and nucleus. Occasionally bright white spots
+show, instead of dark ones. It is thought that they
+may be caused by a violent upward rush of dense
+clouds of white vapor. The white spots again recall
+the sun and his <i>faculæ</i>.</p>
+
+<p>Jupiter’s bands are not fixed. Great changes go
+on constantly among them. Sometimes a white band
+will turn dark-colored, or a dark band will turn white.
+Sometimes few and sometimes many belts are to be
+seen. Sometimes a dark belt will lie slanting across
+the others, nearly from north to south. Once, in a
+single hour, an entirely new belt was seen to come
+into shape. Another time, two whole belts vanished
+in one day. The bands, in which such rapid movements
+are seen, are often thousands of miles in breadth.
+Sometimes these wide zones of clouds will remain for
+weeks the same. At another time a break or rift in
+them will be seen to journey swiftly over the surface
+of the planet.</p>
+
+<p>The winds on earth are often destructive. A hurricane,
+moving at the rate of ninety miles an hour,
+will carry away whole buildings and level entire plantations.<span class="pagenum" id="Page_204">[Pg 204]</span>
+Such hurricanes rarely, if ever, last more
+than a few hours. But winds in Jupiter, judging from
+the movements of the clouds, often travel at the rate
+of one hundred and fifty miles an hour; and that, not
+for hours only, but for many weeks together. What
+manner of living beings could stand such weather
+may well be questioned.</p>
+
+<p>Another difficulty which arises is as to the cause
+of these tremendous disturbances on Jupiter. Our
+earthly storms are brought about by the heat of the
+sun acting on our atmosphere. But the sun-heat
+which reaches Jupiter seems very far from enough to
+raise such vast clouds of vapor, and to bring about
+such prolonged and tremendous hurricanes of wind.</p>
+
+<p>What if there is another cause? What if Jupiter
+is <i>not</i> a cooled body like our earth, but a liquid, seething,
+bubbling mass of fiery heat—just as we believe
+our earth was once upon a time, in long past ages, before
+her outside crust became cold enough for men and
+animals to live thereon? <i>Then</i>, indeed, we could understand
+how, instead of oceans lying on his surface,
+all the water of Jupiter would be driven aloft to hang
+in masses of steam or be condensed into vast cloud-layers.
+<i>Then</i> we could understand why a perpetual
+stir of rushing winds should disturb the planet’s atmosphere.</p>
+
+<p>In that case would Jupiter be a planet at all? Certainly—in
+the sense of obeying the sun’s control. Our
+earth was once, we believe, a globe of melted matter,
+glowing with heat—and farther back still, possibly, a
+globe of gas. Some people are very positive about
+these past changes; but it is wise not to be over-positive<span class="pagenum" id="Page_205">[Pg 205]</span>
+where we can not know to a certainty what
+has taken place. However, Jupiter <i>may</i> have cooled
+down only to the liquid state, and if he goes on cooling
+he may, by and by, gain a solid crust like the earth.</p>
+
+<p>This idea about Jupiter’s hot and molten state belongs
+quite to late years. Certain other matters seem
+to bear it out, though of actual proof we have none.
+It is thought, for instance, that the dull, coppery red
+light, showing often in the dark bands, may be a red
+glow from the heated body within. Also it has been
+calculated that Jupiter gives out much more light than
+our earth would do, if increased to his size and moved
+to his place—more, in fact, than we could reasonably
+expect him to give out. If so, whence does he obtain
+the extra brightness? If he does not shine by reflected
+light alone, he probably shines also in some
+additional degree by his own light.</p>
+
+<p>But what about Jupiter being inhabited? Would
+it in such a case be quite impossible? “Impossible”
+is not a word for us to use about matters where we are
+ignorant. We can only say that it is impossible for
+us to <i>imagine</i> any kind of living creatures finding a
+home there, if our present notions about the present
+state of Jupiter are correct. Then is the chief planet
+of the Solar System a huge, useless monument of
+God’s power to create? Not so fast. Even as merely
+such a monument, he could not be useless. And
+even if he were put to no present use at all, it might
+be merely because this is a time of preparation for
+the future. God has his times of long and slow
+preparation, alike with worlds, with nations, and
+with individuals.</p>
+
+<p><span class="pagenum" id="Page_206">[Pg 206]</span></p>
+
+<p>But now as to the five moons circling round Jupiter.
+There used to be some very pretty ideas afloat
+about the wonderful beauty of the moons, as seen
+from Jupiter, their united brilliancy so far surpassing
+the shining of our one poor satellite, and making up
+for the dim light of Jupiter’s sun.</p>
+
+<p>A certain little difficulty was not quite enough considered.
+If anybody were living on the surface of Jupiter,
+he would have, one is inclined to think, small
+chance of often seeing the moons through the cloud-laden
+atmosphere.</p>
+
+<div class="figcenter" id="f35">
+<img src="images/fig35.jpg" alt="satellites">
+<p class="caption">SATELLITES OF JUPITER COMPARED WITH THE EARTH AND MOON.</p>
+</div>
+
+<p>The nearest of the four larger moons to Jupiter
+would, it is true, appear—when visible at all—rather
+bigger than ours does to us; while the two next would
+be almost half as large, and the farthest about a quarter
+as large—supposing inhabitants of Jupiter to have
+our powers of vision.</p>
+
+<p>All taken together they would cover a considerably
+larger space in the sky than does our moon. But it
+must be remembered that Jupiter’s moons, like ours,
+shine merely by reflected sunlight. And so dim is the<span class="pagenum" id="Page_207">[Pg 207]</span>
+sunshine at that distance compared with what it is
+at our distance, that all the five moons together, even
+if full at the same time, could only give about one-sixteenth
+part of the light which we obtain from our
+one full moon.</p>
+
+<p>Besides, they never are full together, seen from any
+one part of Jupiter. The four inner moons are never
+to be seen “full” at all; for just when they might be
+so, they are eclipsed or shaded by Jupiter’s shadow.
+The fourth sometimes escapes this eclipse, from being
+so much farther away.</p>
+
+<p>A thought has been lately put forward, which may
+or may not have truth in it. What if—instead of
+Jupiter being a world, inhabited by animals and people,
+as is often supposed, with a small distant sun and
+five dim moons to give them light—what if Jupiter is
+himself in some sort a second sun to his moons, and
+what if those “moons” are really inhabited planets?
+It may be so. That is all we can say. The idea is
+not an impossible one.</p>
+
+<p>The so-called “moons” are certainly small. But
+they are by no means too small for such a purpose.
+Jupiter would in that case, with his five moons circling
+round him, enjoying his light and warmth, be a small
+picture of the sun, with his four inner planets and the
+asteroids circling round him, basking in a more lavish
+amount of the same.</p>
+
+<p>Picturing the moons as giving light to Jupiter, we
+find them seemingly dim and weak for such a purpose—though,
+of course, we may here make a grand
+mistake in supposing the eyesight of living creatures
+in Jupiter to be no better than our own eyesight.<span class="pagenum" id="Page_208">[Pg 208]</span>
+Even upon earth a cat can see plainly where a man
+has to grope his way in darkness.</p>
+
+<p>But by picturing the moons as inhabited, and
+Jupiter as giving out some measure of heat and light
+to make up for the lessened amount of light and heat
+received from the sun, the matter becomes more easy
+to our understanding.</p>
+
+<div class="figcenter" id="f36">
+<img src="images/fig36.jpg" alt="system">
+<p class="caption">THE SYSTEM OF JUPITER.</p>
+</div>
+
+<p>The nearest moon has indeed a magnificent view
+of Jupiter as a huge bright disk in its sky, no less<span class="pagenum" id="Page_209">[Pg 209]</span>
+than three thousand times as large as our moon appears
+to us, shining brightly with reflected sunlight,
+and it may be glowing with a red light of his own in
+addition. Even the farthest off of the five sees him
+with a face sixty-five times the size of our moon.
+And the varying colors and stormy changes in the
+cloud-belts, viewed thus near at hand, must afford
+marvelously beautiful effects.</p>
+
+<p>Just as Mercury, Venus, Earth, and Mars travel
+round the sun, at different distances, nearly in the
+same plane, so Jupiter’s five moons travel round him,
+at different distances, nearly in the same plane.
+Jupiter’s moons are always to be seen in a line, not
+one high and another low, one near his pole and another
+near his equator.</p>
+
+<p>The moon nearest to Jupiter, discovered in September,
+1892, by Professor Barnard, now of the Yerkes
+Observatory of the Chicago University, has a probable
+diameter of one hundred miles, and revolves round its
+primary in about twelve hours. The second satellite,
+named Io, is said to be over two thousand miles in
+diameter, travels round Jupiter in less than two of our
+days, and is eclipsed by Jupiter’s shadow once in every
+forty-two hours.</p>
+
+<p>The third moon, Europa, is rather smaller, takes
+over three days to its journey, and suffers eclipse once
+in every eighty-five hours.</p>
+
+<p>The fourth moon, Ganymede, is believed to be considerably
+larger than Mercury, journeys round Jupiter
+once a week, and is eclipsed once every hundred and
+seventy-one hours.</p>
+
+<p>The fifth moon, Callisto, is also said to be slightly<span class="pagenum" id="Page_210">[Pg 210]</span>
+larger than Mercury, performs its journey in something
+more than sixteen days, and from its greater
+distance suffers eclipse less often than the other four.</p>
+
+<p>The distance of the nearest is more than one hundred
+thousand miles from Jupiter; that of the farthest,
+more than one million miles.</p>
+
+<p>The following table presents more minutely the
+results of the latest discoveries concerning these satellites:</p>
+
+<table>
+
+<tr>
+  <td class="tdc bl bt bb">SATELLITES.</td>
+  <td class="tdc bl bt bb">DISTANCE FROM<br>CENTER OF<br>JUPITER.</td>
+  <td class="tdc bl bt bb">DIAMETER.</td>
+  <td class="tdc bl bt br bb">PERIOD OF<br>REVOLUTION.</td></tr>
+
+<tr>
+  <td class="tdl bl br"></td>
+  <td class="tdl br"></td>
+  <td class="tdl br"></td>
+  <td class="tdr br">D. H. M. S.</td></tr>
+
+<tr>
+  <td class="tdl bl br">1. Barnard’s Satellite,</td>
+  <td class="tdl br">112,500 miles.</td>
+  <td class="tdl br">100 miles.</td>
+  <td class="tdr br">11 57 23</td></tr>
+
+<tr>
+  <td class="tdl bl br">2. Io,</td>
+  <td class="tdl br">266,000   ”</td>
+  <td class="tdl br">2,356   ”</td>
+  <td class="tdr br">1 18 27 33</td></tr>
+
+<tr>
+  <td class="tdl bl br">3. Europa,</td>
+  <td class="tdl br">424,000   ”</td>
+  <td class="tdl br">2,046   ”</td>
+  <td class="tdr br">3 13 13 42</td></tr>
+
+<tr>
+  <td class="tdl bl br">4. Ganymede,</td>
+  <td class="tdl br">676,000   ”</td>
+  <td class="tdl br">3,596   ”</td>
+  <td class="tdr br">7 &#160;  3 42 33</td></tr>
+
+<tr>
+  <td class="tdl bl br bb">5. Callisto,</td>
+  <td class="tdl br bb">1,189,000   ”</td>
+  <td class="tdl br bb">2,728   ”</td>
+  <td class="tdr br bb">16 15 32 11</td></tr>
+
+
+</table>
+
+
+<p>The fact of these eclipses, and of the shadow
+thrown by Jupiter’s body, shows plainly that though
+he may give out some measure of light, as has been
+suggested, yet that light can not be strong, or it
+would prevent any shadow from being thrown by the
+sunlight. Also, the dense masses of cloud around
+him, though reflecting sunlight brightly, would shut
+in much of his own light. Possibly it is chiefly as
+heat-giver and as sunlight-reflector that Jupiter serves
+his five satellites.</p>
+
+<p>As with our own moon, so with Jupiter’s moons,
+the real center of their orbit is the sun, and not
+Jupiter. They accompany Jupiter in his journey,
+controlled by the sun, and immensely influenced by
+Jupiter.</p>
+
+<p><span class="pagenum" id="Page_211">[Pg 211]</span></p>
+
+<p>At night the spectacle of the sky seen from Jupiter
+is, with reference to the constellations, the same
+as that which we see from the earth. There, as here,
+shine Orion, the Great Bear, Pegasus, Andromeda,
+Gemini, and all the other constellations, as well as the
+diamonds of our sky: Sirius, Vega, Capella, Procyon,
+Rigel, and their rivals. The 390,000,000 of miles
+which separate us from Jupiter <i>in no way</i> alter the
+celestial perspectives. But the most curious character
+of this sky is unquestionably the spectacle of the
+five moons, each of which shows a different motion.
+The second moves in the firmament with an enormous
+velocity, and Barnard’s satellite still faster, and
+produce almost every day total eclipses of the sun in
+the equatorial regions. The four inner moons are
+eclipsed at each revolution, just at the hours when they
+are at their “full.” The fifth alone attains the full
+phase.</p>
+
+<p>Contrary to the generally received opinion, these
+bodies do not give to Jupiter all the light which is
+supposed. We might think, in fact, as has been so
+often stated, that these five moons illuminate the
+nights five times better relatively than our single
+moon does in this respect, and that they supplement in
+some measure the feebleness of the light received
+from the sun. This result would be, assuredly, very
+agreeable, but nature has not so arranged it. The
+five satellites cover, it is true, an area of the sky
+greater than our moon, but they reflect the light of a
+sun twenty-seven times smaller than ours; indeed, the
+total light reflected is only equal to a sixteenth of
+that of our full moon, even supposing the soil of these<span class="pagenum" id="Page_212">[Pg 212]</span>
+satellites to be as white as it appears to be, especially
+the fifth satellite.</p>
+
+<p>Jupiter appears to be a world still in process of
+formation, which lately—some thousands of centuries
+ago—served as a sun to his own system of five or
+perhaps more worlds. If the central body is not at
+present inhabited, his satellites may be. In this case,
+the magnificence of the spectacle presented by Jupiter
+himself to the inhabitants of the satellites is worthy
+of our attention. Seen from Barnard’s satellite, Jupiter’s
+disk has a diameter of 47°, or more than half
+the distance from the horizon to the zenith. Seen
+from the second satellite, the Jovian globe presents an
+immense disk of twenty degrees in diameter, or 1,400
+times larger than the full moon! What a body!
+What a picture, with its belts, its cloud motions, and
+its glowing coloration, seen from so near! What a
+nocturnal sun!—still warm, perhaps. Add to this the
+aspect of the satellites themselves seen from each other,
+and you have a spectacle of which no terrestrial night
+can give an idea.</p>
+
+<p>Such is the world of Jupiter from the double point
+of view of its vital organization and of the spectacle
+of external nature, seen from this immense observatory.</p>
+
+<p>The attraction of the planets has always played an
+important part in the motion of comets and the form
+of their orbits. The enormous size of Jupiter gives
+it more influence than any other planet, and we are
+not surprised that it should have seriously interfered
+with some of the comets that belong to the Solar
+System. We have already seen that Biela’s comet<span class="pagenum" id="Page_213">[Pg 213]</span>
+was captured by Jupiter, and that it was probably dissolved
+into meteoric dust. We show in the cut the
+orbits of eight others that circle around the sun, but
+retreat no farther away than Jupiter. These are the
+orbits as now determined, but they vary from age to
+age on account of disturbances of other planets. But
+it is not likely that the comets themselves will ever
+escape from the control of Jupiter.</p>
+
+<div class="figcenter" id="f37">
+<img src="images/fig37.jpg" alt="comets">
+<p class="caption">ORBITS OF NINE COMETS CAPTURED BY JUPITER.</p>
+</div>
+
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_214">[Pg 214]</span></p>
+
+<h2 class="nobreak" id="c18">CHAPTER XVIII.</h2>
+</div>
+
+<p class="c sp">SATURN.</p>
+
+
+<p><span class="smcap large">The</span> system of Jupiter is a simple system compared
+with that of Saturn, next in order. For whereas
+Jupiter has only five moons, Saturn has eight, and,
+in addition to these, he has three wonderful rings.
+Neither rings nor moons can be seen without a telescope,
+on account of Saturn’s great distance from us—more
+than three thousand times the distance of the
+moon, or upwards of eight hundred millions of miles.
+Saturn’s mean distance from the sun is eight hundred
+and seventy-six million seven hundred and sixty-seven
+thousand miles.</p>
+
+<p>Saturn does not equal his mighty brother Jupiter
+in size, though he comes near enough in this respect
+to be called often his “twin”—just as that small pair
+of worlds, Venus and Earth, are called “twins.”
+While Jupiter is equal in size to over one thousand
+two hundred earths, Saturn is equal to about seven
+hundred earths. And while Jupiter is equal in weight
+to three hundred earths, Saturn is only equal in weight
+to ninety earths. He appears to be made of very light
+materials—not more than three-quarters as dense as
+water. This would show the present state of Saturn
+to be very different from the present state of the earth.
+We are under the same uncertainty in speaking of
+Saturn as in speaking of Jupiter. Like Jupiter, Saturn
+is covered with dense masses of varying clouds, occasionally<span class="pagenum" id="Page_215">[Pg 215]</span>
+opening and allowing the astronomer peeps
+into lower cloud-levels; but rarely or never permitting
+the actual body of the planet to be seen.</p>
+
+<p>The same perplexities also come in here, to be answered
+much in the same manner. We should certainly
+expect that in a vast globe like Saturn the
+strong force of attraction would bind the whole into a
+dense solid mass; instead of which, Saturn is about
+the least solid of all the planets. He seems to be
+made up of a light, watery substance, surrounded by
+vapor.</p>
+
+<div class="figcenter" id="f38">
+<img src="images/fig38.jpg" alt="saturn">
+<p class="caption">SATURN AND THE EARTH—COMPARATIVE SIZE.</p>
+</div>
+
+<p>One explanation can be offered. What if the globe
+of Saturn be still in a red-hot, molten state, keeping
+such water as would otherwise lie in oceans on his
+surface, floating aloft in masses of steam, the outer
+parts of which condense into clouds?</p>
+
+<p>No one supposes that Jupiter and Saturn are in the
+same condition of fierce and tempestuous heat as the<span class="pagenum" id="Page_216">[Pg 216]</span>
+sun. They may have been so once, but they must
+now have cooled down very many stages from that
+condition. Though no longer, however, a mass of
+far-reaching flames and fiery cyclones, the body of
+each may have only so far cooled as to have reached a
+stage of glowing molten red-heat, keeping all water in
+the form of vapor, and sending up strong rushes of
+burning air to cause the hurricanes which sweep to
+and fro the vast cloud-masses overhead.</p>
+
+<p>And if this be the case, then, with Saturn as with
+Jupiter, comes the question, Can Saturn be inhabited?
+And if—though we may not say it is impossible, yet
+we feel it to be utterly unlikely—then again follows
+the question, What if Saturn’s <i>moons</i> are inhabited?</p>
+
+<p>Telescopic observations tempt us to believe that
+there is on this planet a quantity of heat greater than
+that which results from its distance from the sun; for
+the day-star as seen from Saturn is, as we have said,
+ninety times smaller in surface, and its heat and light
+are reduced in the same proportion. Water could
+only exist in the solid state of ice, and the vapor of
+water could not be produced so as to form clouds
+similar to ours. Now, meteorological variations are
+observed similar to those which we have noticed on
+Jupiter, but less intense. Facts, then, combine with
+theory to show us that the world of Saturn is at a
+temperature at least as high as ours, if not higher.</p>
+
+<p>But the strangest feature of the Saturnian calendar
+is, unquestionably, its being complicated, not only
+with the fabulous number of 25,060 days in a year,
+but, further, with eight different kinds of months, of
+which the length varies from 22 hours to 79 days—that<span class="pagenum" id="Page_217">[Pg 217]</span>
+is to say, from about two Saturnian days to 167.
+It is as if we had here <i>eight moons revolving in eight
+different periods</i>.</p>
+
+<p>The inhabitants of such a world must assuredly
+differ strangely from us from all points of view.
+The specific lightness of the Saturnian substances
+and the density of the atmosphere will have conducted
+the vital organization in an extra-terrestrial
+direction, and the manifestations of life will be produced
+and developed under unimaginable forms. To
+suppose that there is nothing fixed, that the planet itself
+is but a skeleton, that the surface is liquid, that
+the living beings are gelatinous—in a word, that all is
+unstable—would be to surpass the limits of scientific
+induction.</p>
+
+<p>The diameter of the largest moon is about half the
+diameter of the earth, or much larger than Mercury.
+The four inner satellites are all nearer to Saturn than
+our moon to us, though the most distant of the eight
+is ten times as far away. The inner moon takes less
+than twenty-three hours to travel round Saturn, and
+the outer one over seventy-nine days.</p>
+
+<p>A great many charming descriptions have been
+worked up, with Saturn as with Jupiter, respecting
+the magnificent appearance of the eight radiant
+moons, joined to the glorious shining of the rings,
+as quite making up for the diminished light and heat
+of the sun. But here again comes in the doubt,
+whether really it is the moons who make up to Saturn
+for lack of light, or whether it is Saturn who makes
+up to the moons for lack of light.</p>
+
+<p>Certainly, Saturn’s cloudy covering would a little<span class="pagenum" id="Page_218">[Pg 218]</span>
+interfere with observations of the moons by any inhabitants
+of the solid body within—supposing there
+be any solid body at all. And though it sounds very
+wonderful to have eight moons instead of one moon,
+yet all the eight together give Saturn only a very
+small part of the light which we receive from our
+one full moon—so much more dimly does the sun light
+them up at that enormous distance.</p>
+
+<p>The same thing has been noticed with Saturn as
+with Jupiter—that he seems to shine more brightly
+than is to be expected in his position, from mere reflection
+of the sun’s rays. A glowing body within,
+sending a certain amount of added light through or
+between the masses of clouds, would explain away
+this difficulty.</p>
+
+<p>One more possible proof of Saturn’s half-liquid
+state is to be found in his occasional very odd changes
+of shape. Astronomers have been startled by a peculiar
+bulging out on one side, taking off from his
+roundness, and giving a square-shouldered aspect.
+We may not say it is quite impossible that a solid
+globe should undergo such tremendous upheavals and
+outbursts as to raise a great portion of its surface five
+or six hundred miles above the usual level—the
+change being visible at a distance of eight hundred
+millions of miles. But it would be easier to understand
+the possibility of such an event, in the case
+of a liquid, seething mass, than in the case of a
+solid ball.</p>
+
+<p>On the other hand this alteration of outline may
+be caused simply by a great upheaval not of the planet’s
+surface, but of the overhanging layers of clouds.<span class="pagenum" id="Page_219">[Pg 219]</span>
+Some such changes, only much slighter, have been
+remarked in Jupiter.</p>
+
+<p>And now as to the rings. Nothing like them is to
+be seen elsewhere in the Solar System. They are believed
+to be three in number; though some would
+divide them into more than three. Passing completely
+round the whole body of Saturn, they rise, one
+beyond another, to a height of many thousands of miles.</p>
+
+<p>The inner edge of the inner ring—an edge perhaps
+one hundred miles in thickness—is more than ten
+thousand miles from the surface of Saturn or more
+strictly speaking, from the outer surface of Saturn’s
+cloudy envelope. A man standing exactly on
+the equator and looking up, even if no clouds came
+between, would scarcely be able to see such a slender
+dark line at such a height.</p>
+
+<p>This dark, transparent ring, described sometimes
+as dusky, sometimes as richly purple, rises upwards
+to a height or breadth of nine thousand miles. Closely
+following it is a ring more brilliant than Saturn himself,
+over eighteen thousand miles in breadth. When astronomers
+talk of the “breadth” of these rings, it
+must be understood that they mean the width of the
+band measured <i>upwards</i>, in a direction away from the
+planet.</p>
+
+<p>Beyond the broad, bright ring is a gap of about
+one thousand seven hundred miles. Then follows the
+third ring, ten thousand miles in breadth; its outermost
+edge being at a height of more than forty-eight
+thousand miles from Saturn. The color of the third
+ring is grayish, much like the gray markings often
+seen on Saturn.</p>
+
+<p><span class="pagenum" id="Page_220">[Pg 220]</span></p>
+
+<p>What would not be our admiration, our astonishment,
+our stupor perhaps, if it were granted us to be
+transported there alive, and, among all these extra-terrestrial
+spectacles, to contemplate the strange aspect
+of the rings, which stretch across the sky like a
+bridge suspended in the heights of the firmament!
+Suppose we lived on the Saturnian equator itself,
+these rings would appear to us as a thin line drawn
+across the sky above our heads, and passing exactly
+through the zenith, rising from the east and increasing
+in width, then descending to the west and diminishing
+according to perspective. Only there have we
+the rings precisely in the zenith. The traveler who
+journeys from the equator towards either pole leaves
+the plane of the rings, and these sink imperceptibly,
+at the same time that the two extremities cease to appear
+diametrically opposite, and by degrees approach
+each other. What an amazing effect would be produced
+by this gigantic arch, which springs from the
+horizon and spans the sky! The celestial arch diminishes
+in height as we approach the pole. When we
+reach the sixty-third degree of latitude the summit of
+the arch has descended to the level of our horizon and
+the marvelous system disappears from the sky; so that
+the inhabitants of those regions know nothing of it,
+and find themselves in a less favorable position to
+study their own world than we, who are nearly 800,000,000
+miles distant.</p>
+
+<p>During one-half of the Saturnian year the rings
+afford an admirable moonlight on one hemisphere of
+the planet, and during the other half they illuminate
+the other hemisphere; but there is always a half-year<span class="pagenum" id="Page_221">[Pg 221]</span>
+without “ringlight,” since the sun illuminates but one
+face at a time. Notwithstanding their volume and
+number, the satellites do not give as much nocturnal
+light as might be supposed; for they receive, on an
+equal surface, only the ninetieth part of the solar
+light which our moon receives. All the Saturnian satellites
+which can be at the same time above the horizon
+and as near as possible to the full phase do not
+afford more than the hundredth part of our lunar light.
+But the result may be nearly the same, for the optic
+nerve of the Saturnians may be ninety times more
+sensitive than ours.</p>
+
+<p>But there are further strange features in this system.
+The rings are so wide that their shadow extends over
+the greater part of the mean latitudes. During fifteen
+years the sun is to the south of the rings, and for fifteen
+years it is to the north. The countries of Saturn’s
+world which have the latitude of Paris endure
+this shadow for more than five years. At the equator
+the eclipse is shorter, and is only renewed every fifteen
+years; but there are every night, so to say, eclipses
+of the Saturnian moons by the rings and by themselves.
+In the circumpolar regions the day-star is
+never eclipsed by the rings; but the satellites revolve
+in a spiral, describing fantastic rounds, and the sun
+himself disappears at the pole during a long night of
+fifteen years.</p>
+
+<p>At one time it was supposed that the rings were
+solid, but they are now believed to consist of countless
+myriads of meteorites, each whirling in its own appointed
+pathway round the monster planet.</p>
+
+<div class="figcenter" id="f39">
+<img src="images/fig39.jpg" alt="saturn">
+<p class="caption">IDEAL VIEW OF SATURN’S RINGS AND SATELLITES FROM THE<br>
+PLANET.</p>
+</div>
+
+<p>As already said—leaving out of the question the
+<span class="pagenum" id="Page_222">[Pg 222]</span>cloudy atmosphere—a man standing on the equator
+would see nothing of the rings. A man standing at
+the north pole or the south pole of Saturn could see
+nothing either, since the rings would all lie below his
+horizon. But if he traveled southward from the north
+pole, or northward from the south pole, towards the
+equator, he would in time see the ringed arch appearing
+above the horizon, rising higher and growing
+wider with every mile of his journey; and when he
+was in a position to view the whole broad expanse, the
+transparent half-dark belt below, the wide radiant band<span class="pagenum" id="Page_223">[Pg 223]</span>
+rising upwards over that, and the grayish border surmounting
+all, he would truly have a magnificent spectacle
+before him.</p>
+
+<p>This magnificent spectacle is, however, by no means
+always visible, even from those parts of Saturn where
+alone it ever can be seen. The rings shine merely
+by reflected sunlight. Necessarily, therefore, while
+the sunbeams make one side bright the other side is
+dark; and not only this, but the rings throw broad and
+heavy shadows upon Saturn in the direction away
+from the sunlight.</p>
+
+<p>In the daytime they probably give out a faint shining,
+something like our own moon when seen in sunlight.
+During the summer nights they shine, no
+doubt, very beautifully. During the winter nights it
+so happens that their bright side is turned away; and
+not only that, but during the winter days the rings,
+while giving no light themselves to the wintry hemisphere
+of Saturn, completely hide the sun.</p>
+
+<p>When it is remembered that Saturn’s winter—that
+is, the winter of each hemisphere in turn—lasts during
+fifteen of our years; and when we hear of total
+eclipses of the sun lasting unbroken through eight
+years of such a winter, with not even bright rings to
+make up for his absence, we can not think of Saturn
+as a tempting residence. The sun gives Saturn
+at his best only about one-ninetieth of the heat and
+light that he gives to our earth; but to be deprived of
+even that little for eight years at a time, does indeed
+sound somewhat melancholy.</p>
+
+<p>Looking now at the other side of the question, the
+possible inhabitants of the moons, especially those<span class="pagenum" id="Page_224">[Pg 224]</span>
+near at hand, would have splendid views of Saturn
+and his rings in all their varying phases. For Saturn
+is a beautiful globe, wrapped in his changeful envelope
+of clouds, which, seen through a telescope, are lit
+up often with rainbow tints of blue and gold; a creamy
+white belt lying usually on the equator; while around
+extend the purple and shining and gray rings, sometimes
+rivaling in bright colors Saturn himself.</p>
+
+<p>We are compelled to assume that the continuous
+appearance of the rings is not due to real continuity
+of substance, but that they are composed of flights of
+disconnected satellites, so small and so closely packed
+that, at the immense distance to which Saturn is removed,
+they appear to form a continuous mass. There
+are analogous instances in the Solar System. In the
+zone of asteroids we have an undoubted instance
+of a flight of disconnected bodies traveling in a ring
+about a central attracting mass. The existence of
+zones of meteorites traveling around the sun has long
+been accepted as the only probable explanation of the
+periodic returns of meteoric showers. Again, the singular
+phenomenon called the Zodiacal Light is, in all
+probability, caused by a ring of minute cosmical bodies
+surrounding the sun. In the Milky Way and in the
+ring-nebulæ we have other illustrations of similar arrangements
+in nature, belonging, however, to orders
+immeasurably vaster than any within the Solar System.</p>
+
+<p>The moons of Saturn do not, like those of Jupiter,
+travel in one plane.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_225">[Pg 225]</span></p>
+
+<h2 class="nobreak" id="c19">CHAPTER XIX.</h2>
+</div>
+
+<p class="c sp">URANUS AND NEPTUNE.</p>
+
+
+<p><span class="smcap large">Till</span> the year 1781, Saturn was believed to be the
+outermost planet of the Solar System, and nobody
+suspected the fact of two great, lonely brother-planets
+wandering around the same sun at vast distances beyond,—Uranus,
+nine hundred millions of miles from
+Saturn; Neptune, nine hundred millions of miles
+from Uranus. No wonder they remained long undiscovered.</p>
+
+<p>Uranus can sometimes be seen by the unaided eye
+as a dim star of the sixth magnitude. And when he
+was known for a planet, it was found that he <i>had</i>
+been often so seen and noted. Again and again he
+had been taken for a fixed star, and as he moved on,
+disappearing from that particular spot, it was supposed
+that the star had vanished.</p>
+
+<p>One night, March 13, 1781, when William Herschel
+was busily exploring the heavens with a powerful
+telescope, he noticed something which he took for a
+comet without a tail. He saw it was no mere point of
+light like the stars, but had a tiny round disk or face,
+which could be magnified. So he watched it carefully,
+and found in the course of a few nights that it
+moved—very slowly, certainly; but still it did move.
+Further watching and calculation made it clear that,
+though the newly-found heavenly body was at a very
+great distance from the sun, yet it was moving slowly<span class="pagenum" id="Page_226">[Pg 226]</span>
+in an orbit <i>round</i> the sun. Then it was known to be
+a planet, and another member of the Solar System.</p>
+
+<p>From that day the reputation of Herschel rapidly
+increased. King George III, who loved the sciences
+and patronized them, had the astronomer presented
+to him; charmed with the simple and modest account
+of his efforts and his labors, he secured him a life
+pension and a residence at Slough, in the neighborhood
+of Windsor Castle. His sister Caroline assisted
+him as secretary, copied all his observations, and
+made all his calculations; the king gave him the title
+and salary of assistant astronomer. Before long the
+observatory at Slough surpassed in celebrity the principal
+observatories of Europe; we may say that, in
+the whole world, this is the place where the most discoveries
+have been made.</p>
+
+<p>Astronomers soon applied themselves to the observation
+of the new body. They supposed that this
+“comet” would describe, as usually happens, a very
+elongated ellipse, and that it would approach considerably
+to the sun at its perihelion. But all the calculations
+made on this supposition had to be constantly
+recommenced. They could never succeed in representing
+all its positions, although the star moved very
+slowly: the observations of one month would utterly
+upset the calculations of the preceding month.</p>
+
+<p>Several months elapsed without a suspicion that a
+veritable planet was under observation, and it was not
+till after recognizing that all the imaginary orbits for
+the supposed comet were contradicted by the observations,
+and that it had probably a circular orbit much
+farther from the sun than Saturn, till then the frontier
+<span class="pagenum" id="Page_228">[Pg 228]</span>of the system, that astronomers came to consider
+it as a planet. Still, this was at first but a provisional
+consent.</p>
+
+<div class="figcenter" id="f40">
+<img src="images/fig40.jpg" alt="astronomers">
+<p class="caption"><span class="smcap">Prominent Astronomers of Former Times.</span></p>
+<p class="caption">Tycho Brahe, Hipparchos, Galilei, Newton,<br>Kepler, Kant, Kopernikus, Laplace.</p>
+</div>
+
+<p>It was, in fact, more difficult than we may think to
+increase without scruple the family of the sun. Indeed,
+for reasons of expediency this idea was opposed.
+Ancient ideas are tyrannical. Men had so
+long been accustomed to consider old Saturn as the
+guardian of the frontiers, that it required a rare boldness
+of spirit to decide on extending these frontiers
+and marking them by a new world.</p>
+
+<p>William Herschel proposed the name of <i>Georgium
+Sidus</i> “the Star of George,” just as Galileo had given
+the name of “Medicean stars” to the satellites of Jupiter
+discovered by him, and as Horace had said <i>Julium
+Sidus</i>. Others proposed the name of <i>Neptune</i>, in
+order to maintain the mythological character, and to
+give to the new body the trident of the English maritime
+power; others, <i>Uranus</i>, the most ancient deity of
+all, and the father of Saturn, to whom reparation was
+due for so many centuries of neglect. Lalande proposed
+the name of <i>Herschel</i>, to immortalize the name
+of its discoverer. These last two denominations prevailed.
+For a long time the planet bore the name of
+Herschel; but custom has since declared for the mythological
+appellation, and Jupiter, Saturn, and Uranus
+succeed each other in order of descent—son, father,
+and grandfather.</p>
+
+<p>The discovery of Uranus extended the radius of
+the Solar System from 885,000,000 to 1,765,000,000
+of miles.</p>
+
+<p>The apparent brightness of this planet is that of<span class="pagenum" id="Page_229">[Pg 229]</span>
+a star of the sixth magnitude; observers whose sight
+is very piercing may succeed in recognizing it with
+the naked eye when they know where to look for it.
+Uranus moves slowly from west to east, and takes no
+less than eighty-four years to make the complete circuit
+of the sky. In its annual motion round the sun
+the earth passes between the sun and Uranus every
+369 days—that is to say, once in a year and four days.
+It is at these times that this planet crosses the meridian
+at midnight. We can observe it in the evening
+sky for about six months of every year.</p>
+
+<p>Everybody supposed that now, at least, the outermost
+member of all was discovered. But a very
+strange and remarkable thing happened.</p>
+
+<p>Astronomers know with great exactness the paths
+of the planets in the heavens. They can tell, years
+beforehand, precisely what spot in space will be filled
+at any particular time by any particular planet. I am
+speaking now of their movements round the sun and
+in the Solar System—not of the movements of the
+whole family with the sun, about which little is yet
+known.</p>
+
+<p>Each planet has its own particular pathway; its
+own particular distance from the sun, varying at each
+part of its pathway; its own particular speed in traveling
+round the sun, changing constantly from faster
+to slower or slower to faster, according to its distance
+from the sun, and according to the pull backwards or
+forwards of our neighboring planets in front or in rear.
+For as the orbits of all the planets are ovals, with the
+sun not in the middle, but somewhat to one side of the
+middle, it follows that all the planets, in the course of<span class="pagenum" id="Page_230">[Pg 230]</span>
+their years, are sometimes nearer to and sometimes
+farther from the sun.</p>
+
+<p>The astronomers of the present day understand
+this well, and can describe with exactness the pathway
+of each planet. This knowledge does not come
+merely from watching one year how the planets travel,
+and remembering for another year, but is much more
+a matter of close and difficult calculation. Many
+things have to be considered, such as the planet’s
+distance from the sun, the sun’s power of attraction,
+the planet’s speed, the nearness and weight of other
+neighboring planets.</p>
+
+<p>All these questions were gone into, and astronomers
+sketched out the pathway in the heavens which they
+expected Uranus to follow. He would move in such
+and such an orbit, at such and such distances from the
+sun, and at such and such rates of speed.</p>
+
+<p>But Uranus would not keep to these rules. He
+quite discomfited the astronomers. Sometimes he
+went fast, when, according to their notions, he ought
+to have gone more slowly; and sometimes he went
+slowly, when they would have looked for him to go
+more fast, and the line of his orbit was quite outside
+the line of the orbit which they had laid down. He
+was altogether a perplexing acquaintance, and difficult
+to understand. However, astronomers felt sure
+of their rules and modes of calculation, often before
+tested, and not found to fail. They made a guess at
+an explanation. What if there were yet another
+planet beyond Uranus, disturbing his motions—now
+drawing him on, now dragging him back, now so far
+balancing the sun’s attraction by pulling in the opposite<span class="pagenum" id="Page_231">[Pg 231]</span>
+direction as to increase the distance of Uranus
+from the sun?</p>
+
+<p>It might be so. But who could prove it? Hundreds
+of years might pass before any astronomer, in
+his star-gazing, should happen to light upon such a
+dim and distant world. Nay, the supposed planet
+might be, like Uranus, actually seen, and only be mistaken
+for a “variable star,” shining but to disappear.</p>
+
+<p>There the matter seemed likely to rest. There the
+matter probably would have rested for a good while,
+had not two men set themselves to conquer the difficulty.
+One was a young Englishman, a student of
+Cambridge, John Couch Adams; the other, a young
+Frenchman, Urbain Jean Joseph Leverrier,—both being
+astronomers.</p>
+
+<p>Each worked independently of the other, neither
+knowing of the other’s toil. The task which they
+had undertaken was no light one—that of reaching
+out into the unknown depths of space to find an unknown
+planet.</p>
+
+<p>Each of these silent searchers into the sky-depths
+calculated what the orbit and speed of Uranus would
+be, without the presence of another disturbing planet
+beyond. Each examined what the amount of disturbance
+was, and considered the degree of attraction
+needful to produce that disturbance, together with
+the direction from which it had come. Each, in
+short, gradually worked his way through calculations
+far too deep and difficult for ordinary minds to grasp,
+till he had found just that spot in the heavens where a
+planet <i>ought</i> to be, to cause, according to known laws,
+just such an effect upon Uranus as had been observed.</p>
+
+<p><span class="pagenum" id="Page_232">[Pg 232]</span></p>
+
+<p>Adams finished his calculation first, and sent the
+result to two different observatories. Unfortunately,
+his report was not eagerly taken up. It was, in fact,
+hardly believed. Leverrier finished his calculation
+also, and sent the result to the Berlin Observatory.
+The planet was actually seen in England first, but the
+discovery was actually made known from Berlin first.
+The young Englishman had been beforehand, but the
+young Frenchman gained foremost honor.</p>
+
+<p>It was on the 23d of September, 1846, that Leverrier’s
+letter reached the Berlin astronomers. The
+sky that night was clear, and we can easily understand
+with what anxiety Dr. Galle directed his telescope to
+the heavens. The instrument was pointed in accordance
+with Leverrier’s instructions. The field of view
+showed, as does every part of the heavens, a multitude
+of stars. One of these was really the planet.
+The new chart—prepared by the Berlin Academy of
+Sciences, upon which the place of every star, down
+even to those of the tenth magnitude, was engraved—was
+unrolled, and, star by star, the heavens were compared
+with the chart. As the process of identification
+went on, one object after another was found in the
+heavens as engraved on the chart, and was of course
+rejected. At length a star of the eighth magnitude—a
+brilliant object—was brought into review. The
+map was examined, but there was no star there.
+This object could not have been in its present place
+when the map was formed. The object was therefore
+a wanderer—a planet. Yet it is necessary to be
+excessively cautious in such a matter.</p>
+
+<p>Many possibilities had to be guarded against. It<span class="pagenum" id="Page_233">[Pg 233]</span>
+was, for instance, possible that the object was really a
+star which, by some mischance, eluded the careful eye
+of the astronomer who constructed the map. It was
+even possible that the star might be one of the large
+class of variables which alternate in brightness, and
+it might have been conceivable that it was too faint
+to be seen when the chart was made. Even if neither
+of these explanations would answer, it was still necessary
+to show that the object was now moving, and
+moving with that particular velocity and in that particular
+direction which the theory of Leverrier indicated.
+The lapse of a single day was sufficient to
+dissipate all doubts. The next night the object was
+again observed. It had moved, and when its motion
+was measured it was found to accord precisely with
+what Leverrier had foretold. Indeed, as if no circumstance
+in the confirmation should be wanting, it was
+ascertained that the diameter of the planet, as measured
+by the micrometers at Berlin, was practically coincident
+with that anticipated by Leverrier.</p>
+
+<p>The world speedily rang with the news of this
+splendid achievement. Instantly the name of Leverrier
+rose to a pinnacle hardly surpassed by that of any
+astronomer of any age or country. For a moment it
+seemed as if the French nation were to enjoy the undivided
+honor of this splendid triumph. But in the
+midst of the pæans of triumph with which the enthusiastic
+French nation hailed the discovery of Leverrier,
+there appeared a letter from Sir John Herschel
+in the <i>Athenæum</i> for 3d October, 1846, in which he
+announced the researches made by Adams, and claimed
+for him a participation in the glory of the discovery.<span class="pagenum" id="Page_234">[Pg 234]</span>
+Subsequent inquiry has shown that this claim was a
+just one, and it is now universally admitted by all independent
+authorities.</p>
+
+<p>This, however, was of slight comparative importance.
+The truly wonderful part of the matter was,
+that these two men could have so reasoned that, from
+the movements of one lately-discovered planet, they
+could point out the exact spot where a yet more distant
+planet ought to be, and that close to this very
+spot the planet was found. For when, both in England
+and in Germany, powerful telescopes were pointed
+in the direction named—<i>there the planet was</i>. No
+doubt about the matter. Not a star, but a real new
+planet in the far distance, wandering slowly round
+the sun.</p>
+
+<p>Here we have the discovery of Neptune in its simple
+grandeur. This discovery is splendid, and of the
+highest order from a philosophical point of view, for
+it proves the security and the precision of the data of
+modern astronomy. Considered from the point of
+view of practical astronomy, it was but a simple exercise
+of calculation, and the most eminent astronomers
+saw in it nothing else! It was only after its verification,
+its public demonstration—it was only after the
+visual discovery of Neptune—that they had their eyes
+opened, and felt for a moment the dizziness of the infinite
+in view of the horizon revealed by the Neptunian
+perspective. The author of the calculation himself,
+the transcendent mathematician, did not even
+give himself the trouble to take a telescope and look
+at the sky to see whether a planet was really there!
+I even believe that he never saw it. For him, however,<span class="pagenum" id="Page_235">[Pg 235]</span>
+then and always, to the end of his life, astronomy
+was entirely inclosed in formulæ—the stars were but
+centers of force.</p>
+
+<p>Very often I submitted to him the doubts of an
+anxious mind on the great problems of infinitude: I
+asked him if he thought that the other planets might
+be inhabited like ours, what might be especially the
+strange vital conditions of a world separated from the
+sun by the distance of Neptune, what might be the
+retinue of innumerable suns scattered in immensity,
+what astonishing colored lights the double stars should
+shed on the unknown planets which gravitate in these
+distant systems. His replies always showed me that
+these questions had no interest for him, and that, in
+his opinion, the essential knowledge of the universe
+consisted in equations, formulæ, and logarithmic series
+having for their object the mathematical theory of velocities
+and forces.</p>
+
+<p>But it is not the less surprising that he had not
+the <i>curiosity</i> to verify the position of his planet, which
+would have been easy, since it shows a planetary disk;
+and, besides, he might have had the aid of a chart,
+because he had only to ask for these charts from the
+Berlin Observatory, where they had just been finished
+and <i>published</i>. It is not the less surprising that Arago,
+who was more of a physicist than a mathematician,
+more of a naturalist than a calculator, and whose
+mind had so remarkable a synthetical character, had
+not himself directed one of the telescopes of the observatory
+towards this point of the sky, and that no
+other French astronomer had this idea. But what surprises
+us still more is to know that <i>nearly a year before<span class="pagenum" id="Page_236">[Pg 236]</span></i>,
+in October, 1845, a young student of the University
+of Cambridge, Mr. Adams, had sought the
+solution of the <i>same</i> problem, obtained the same results,
+and communicated these results to the director
+of the Greenwich Observatory, and that the astronomer
+to whom these results were confided had said
+nothing, and had not himself searched in the sky
+for the optical verification of his compatriot’s solution!</p>
+
+<p>This was indeed a triumph of human intellect.
+Yet it is no matter for human pride, but rather of
+thankfulness to God, who gave to man this marvelous
+reasoning power. And the very delight we have in
+such a success may humble us in the recollection of
+the vast amount lying beyond of the utterly unknown.
+But while the rare mind of a Newton could meekly
+realize the littleness of all he knew, lesser minds are
+very apt to be puffed up with the thought of what the
+human intellect can accomplish.</p>
+
+<p>Perhaps the chief feeling of lawful satisfaction in
+this particular discovery arises from the fact that it
+gives marked and strong proof of the truth of our
+present astronomical system and beliefs. Many mistakes
+may be made, and much has often to be unlearned.
+Nevertheless, if the general principles of
+modern astronomy were wrong, if the commonly-received
+facts were a delusion, such complete success
+could not have attended so delicate and difficult a
+calculation.</p>
+
+<p>We do not know much about these two outer planets,
+owing to their enormous distance from us. Uranus
+is in size equal to seventy-four earths, and Neptune is<span class="pagenum" id="Page_237">[Pg 237]</span>
+in size equal to one hundred and five earths. Both
+these planets are formed of somewhat heavier materials
+than Saturn, being about as dense as water.</p>
+
+<p>The size of the sun as seen from Uranus is about
+one three-hundred-and-ninetieth part of the size of
+the sun we see. To Neptune he shows a disk only
+one nine-hundredth part of the size of that visible to
+us—no disk at all, in fact, but only starlike brilliancy.</p>
+
+<p>The Uranian year lasts about eighty-four of our
+years; and this, with a very sloping axis, must cause
+most long and dreary winters, the tiny sun being hidden
+from parts of the planet during half an earthly
+life-time.</p>
+
+<p>Uranus has at least four moons, traveling in very
+different planes from the plane of the ecliptic. Once
+it was thought that he had eight, but astronomers have
+since searched in vain for the other four, believed for
+a while to exist. Neptune has one moon, and may
+possess others not yet discovered.</p>
+
+<p>Sir Henry Holland, the celebrated physician, and
+a devoted student of astronomy, has left on record an
+incident of his life connected with the planet Neptune
+of singular interest. I give it here, and in his own
+words, because it is scarcely likely otherwise to fall
+under the notice of astronomical readers. After stating
+that his interest in astronomy had led him to take advantage
+of all opportunities of visiting foreign observatories,
+he says:</p>
+
+<p>“Some of these opportunities, indeed, arising out
+of my visits to observatories both in Europe and
+America, have been remarkable enough to warrant a
+more particular mention of them. That which most<span class="pagenum" id="Page_238">[Pg 238]</span>
+strongly clings to my memory is an evening I passed
+with Encke and Galle in the observatory at Berlin,
+some ten or twelve days after the discovery of the
+planet Neptune on this very spot; and when every
+night’s observations of its motions had still an especial
+value in denoting the elements of its orbit. I
+had casually heard of the discovery at Bremen, and
+lost no time in hurrying on to Berlin. The night in
+question was one of floating clouds, gradually growing
+into cumuli; and hour after hour passed away
+without sight of the planet which had just come to
+our knowledge by so wonderful a method of predictive
+research. Frustrated in this main point, it was
+some compensation to stay and converse with Encke
+in his own observatory, one signalized by so many
+discoveries, the stillness and darkness of the place
+broken only by the solemn ticking of the astronomical
+clock, which, as the unfailing interpreter of the
+celestial times and motions, has a sort of living existence
+to the astronomer. Among other things discussed,
+while thus sitting together in a sort of tremulous
+impatience, was the name to be given to the new
+planet. Encke told me he had thought of ‘Vulcan,’
+but deemed it right to remit the choice to Leverrier,
+then supposed to be the sole indicator of the planet and
+its place in the heavens; adding that he expected Leverrier’s
+answer by the first post. Not an hour had
+elapsed before a knock at the door of the observatory
+announced the letter expected. Encke read it aloud;
+and, coming to the passage where Leverrier proposed
+the name of ‘Neptune,’ exclaimed, ‘<i>So lass den Namen
+Neptun sein.</i>’</p>
+
+<p><span class="pagenum" id="Page_239">[Pg 239]</span></p>
+
+<p>It was a midnight scene not easily to be forgotten.
+A royal baptism, with its long array of titles, would
+ill compare with this simple naming of the remote
+and solitary planet thus wonderfully discovered. There
+is no place, indeed, where the grandeur and wild ambitions
+of the world are so thoroughly rebuked and
+dwarfed into littleness as in the astronomical observatory.
+As a practical illustration of this remark,
+I would add that my own knowledge of astronomers—those
+who have worked themselves with the telescope—has
+shown them to be generally men of tranquil
+temperament, and less disturbed than others by
+worldly affairs, or by the quarrels incident even to
+scientific research.”</p>
+
+<p>The same reasoning which has been used in reference
+to Jupiter and his moons, and to Saturn and his
+moons, might perhaps be applied also to Uranus and
+Neptune and their moons.</p>
+
+<p>We know too little yet of their condition to venture
+far in such speculations. Still, taking the matter as
+a whole, there seem many reasons to incline us to the
+idea that each of the four greater outside planets may
+be a kind of secondary half-cooled sun to his satellites,
+helping to make up to them for the small amount
+of light and heat which they can obtain from the far-off
+sun.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_240">[Pg 240]</span></p>
+
+<h2 class="nobreak" id="c20">CHAPTER XX.</h2>
+</div>
+
+<p class="c sp">COMETS AND METEORITES.</p>
+
+
+<p><span class="smcap large">A curious</span> discovery has been lately made. It is
+that some sort of mysterious tie seems to exist between
+comets and meteorites. For a long while this
+was never suspected. How should it be? The comets,
+so large, so airy, so light; the meteorites, so small, so
+solid, so heavy,—how could it possibly be supposed
+that the one had anything to do with the other? But
+supposings often have to give in to facts. Astronomers
+are gradually becoming convinced that there certainly
+is a connection between the two.</p>
+
+<p>Strange to say, comets and meteorites occupy—sometimes,
+at least—the very same pathways in the
+heavens, the very same orbits round the sun. A certain
+number of meteorite systems are now pretty well
+known to astronomers as regularly met by our earth
+at certain points in her yearly journey. Some of
+these systems or rings have each a comet belonging
+to it—not merely journeying near, but actually in its
+midst, on the same orbit.</p>
+
+<p>Perhaps it would be more correct to say that the
+meteorites belong to the comet, than that the comet
+belongs to the meteorites. We tread here on uncertain
+ground; for whether the meteorites spring from
+the comet, or whether the comet springs from the
+meteorites, or whether each has been brought into<span class="pagenum" id="Page_241">[Pg 241]</span>
+existence independently of the other, no one can at
+present say.</p>
+
+<p>Though it is out of our power to explain the kind
+of connection, yet a connection there plainly is. So
+many instances are now known of a comet and a
+meteorite ring traveling together that it is doubtful
+whether any such ring could be found without a
+comet in its midst. By and by the doubt may spring
+up whether there ever exists a comet without a train
+of meteorites following him.</p>
+
+<p>Among the many different meteorite rings which
+are known, two of the most important are the so-called
+August and November systems. Of these two,
+the November system must claim our chief attention.
+Not that we are at all sure of these being the most
+important meteorite rings in the Solar System. On
+the contrary, as regards the November ring, we have
+some reason to think that matters may lie just the
+other way.</p>
+
+<p>The comet belonging to the November system is
+a small one—quite an insignificant little comet—only
+visible through a telescope. We do not, of course,
+know positively that larger comets and greater meteorite
+systems generally go together, but, to say the least,
+it seems likely. And if the greatness of a ring can
+at all be judged of by the size of its comet, then the
+November system must be a third-rate specimen of
+its kind. It is of particular importance to us, merely
+because it happens to be the one into which our
+earth plunges most deeply, and which we therefore
+see and know the best. The August ring is, on the
+contrary, connected with a magnificent comet, and<span class="pagenum" id="Page_242">[Pg 242]</span>
+may be a far grander system. But our pathway does
+not lead us into the midst of the August meteors as
+into those of November. We pass, seemingly, through
+its outskirts.</p>
+
+<p>The meteorites of the November system are very
+small. They are believed to weigh commonly only
+a few grains each. If they were larger and heavier,
+some of them would fall to earth as aerolites, not
+more than half-burnt in their rush through the atmosphere.
+But this they are never found to do.</p>
+
+<p>There are known meteorite systems, which our
+earth merely touches or grazes in passing, from which
+drop aerolites of a very different description—large,
+heavy, solid masses. It is well for us that we do not
+plunge into the midst of any such ring, or we might
+find our air, after all, a poor protection.</p>
+
+<p>The last grand display of the November system of
+meteorites took place in the years 1866 to 1869, being
+continued more or less during three or four Novembers
+following. The next grand display will occur
+in the year 1899.</p>
+
+<p>For this system—Leonides, as it is called, because
+the falling-stars in this display seem all to shoot towards
+us from a spot in the constellation Leo—seems
+to have a “time” or “year” of thirty-three and a
+quarter earthly years. The shape of its orbit is a
+very long ellipse, near one end of which is the sun,
+while the other end is believed to reach farther away
+than the orbit of Uranus.</p>
+
+<p>A great deal of curiosity has been felt about the
+actual length and breadth and depth of the stream of
+meteorites through which our solid earth has so often<span class="pagenum" id="Page_243">[Pg 243]</span>
+plowed her way. During many hours at a time,
+lookers-on have watched the magnificent display of
+heavenly fireworks,—not a mere shooting-star here
+and there, as on common nights, but radiant meteors,
+flashing and dying by thousands through the sky.
+In 1866 no less than eight thousand meteors, in two
+hours and a quarter, were counted from the Greenwich
+Observatory in England. A natural wonder
+sprang up in many minds as to the extent of the ring
+from which they fell.</p>
+
+<p>For not in one night only, but in several nights
+during three or four years, and that not once only but
+once in every thirty-three years, thousands and tens
+of thousands appear to have been stolen by our earth
+from the meteorite-ring, never again to be restored.
+Yet each time we touch the ring, we find the abundance
+of little meteorites in nowise seemingly lessened.</p>
+
+<p>When speaking of a “ring” of meteorites, it must
+not be supposed that necessarily the meteorites form
+a whole unbroken ring all round the long oval orbit.
+There may be no breaks. There may be a more or
+less thin scattering throughout the entire length of
+the pathway. But the meteorites certainly seem to
+cluster far more densely in some parts of the orbit
+than in other parts, and it was about the size of the
+densest cluster that so much curiosity was felt.</p>
+
+<p>Little can be positively known, though it is very
+certain that the cluster must be enormous in extent.
+Three or four years running, as our earth, after journeying
+the whole way round the sun, came again to
+that point in her orbit where she passes through the<span class="pagenum" id="Page_244">[Pg 244]</span>
+orbit of the Leonides, she found the thick stream of
+meteorites still pouring on, though each year lessening
+in amount. Taking into account this fact, and
+also the numbers that were seen to fall night after
+night, and also the speed of our earth, a “rough estimate”
+was formed.</p>
+
+<p>The length of this dense cluster is supposed to
+reach to many hundreds of millions of miles. The
+thickness or depth of the stream is calculated to be
+in parts over five hundred thousand miles, and the
+breadth about ten times as much as the depth. Each
+meteorite is probably at a considerable distance from
+his neighbor; but the whole mass of them, when in
+the near neighborhood of the sun, must form a magnificent
+sight.</p>
+
+<p>And if this be only a third-rate system, what must
+a first-rate system be like? And how many such systems
+are there throughout the sun’s wide domains?
+The most powerful telescope gives us no hint of the
+existence of these rings till we find ourselves in their
+midst.</p>
+
+<p>It may be that they are numbered by thousands,
+even by millions. The whole of the Solar System—nay,
+the very depths of space beyond—may, for aught
+we know, be crowded with meteorite systems. Every
+comet may have his stream of meteorites following
+him. But though the comet is visible to us, the meteorites
+are not. Billions upon billions of them may
+be ever rushing round our sun, entirely beyond our
+ken, till one or another straggler touches our atmosphere
+to flash and die as a “shooting star” in our sight.</p>
+
+<p>We have, and with our present powers we can<span class="pagenum" id="Page_245">[Pg 245]</span>
+have, no certainty as to all this. But I may quote
+here the illustration of a well-known astronomical
+writer on the subject.</p>
+
+<p>Suppose a blind man were walking out of doors
+along a high road, and during the course of a few
+miles were to feel rain falling constantly upon him.
+Would it be reasonable on his part, if he concluded
+that a small shower of rain had accompanied him along
+the road as he moved, but that fine weather certainly
+existed on either side of the road? On the contrary,
+he might be sure that the drops which he felt, were
+but a few among millions falling all together.</p>
+
+<p>Or, look at the raindrops on your window some
+dull day at home. Count how many there are? Could
+you, with any show of common sense, decide that
+those raindrops, and those alone, had fallen that day?
+So, when we find these showers of meteorites falling
+to earth, we may safely conclude that, for every one
+which touches our atmosphere, myriads rush elsewhere
+in space, never coming near us.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_246">[Pg 246]</span></p>
+
+<h2 class="nobreak" id="c21">CHAPTER XXI.</h2>
+</div>
+
+<p class="c sp">MORE ABOUT COMETS AND METEORITES.</p>
+
+
+<p><span class="smcap large">The</span> three prominent features of comets—a head,
+nucleus, and tail—are seen only in particular instances.
+The great majority appear as faint globular
+masses of vapor, with little or no central condensation,
+and without tails. On the other hand, some
+have a strongly-defined nucleus, which shines with a
+light as vivacious as that of the planets, so as to be
+even visible in the daytime. This was the case with
+one seen at Rome soon after the assassination of Julius
+Cæsar, believed by the populace to be the soul of
+the dictator translated to the skies. The first comet
+of the year 1442 was also so brilliant, that the light of
+the sun at noon, at the end of March, did not prevent
+it from being seen; and the second, which appeared
+in the summer, was visible for a considerable time
+before sunset. In 1532, the people of Milan were
+alarmed by the appearance of a star in the broad daylight;
+and as Venus was not then in a position to be
+visible, the object is inferred to have been a comet.
+Tycho Brahe discovered the comet of 1577, from his
+observatory in the isle of Huene, in the sound, before
+sunset; and Chizeaux saw the comet of 1744, at one
+o’clock in the afternoon, without a telescope.</p>
+
+<p>The comet of 1843, already referred to in a previous
+chapter, was distinctly seen at noon by many persons
+in the streets of Bologna without the aid of glasses.<span class="pagenum" id="Page_247">[Pg 247]</span>
+The nucleus is generally of small size, but the surrounding
+nebulosity, which forms the head, is often of
+immense extent; and the hazy envelope, the “horrid
+hair” of poetry, is sometimes seen separated from it
+by a dark space, encircling it like a ring. This was
+the aspect of the comet of 1811. The entire diameter of
+the head measured 1,250,000 miles, and hence its bulk
+was nearly three times that of the sun, and four million
+times that of the earth. But such extraordinary
+dimensions are quite exceptional.</p>
+
+<div class="figcenter" id="f41">
+<img src="images/fig41.jpg" alt="1811">
+<p class="caption">THE GREAT COMET OF 1811.</p>
+</div>
+
+<p>Popular impressions respecting the supposed terrestrial
+effects of the comet of 1811—a fine object in
+the autumn of that year, long remembered by many—are
+on record. It was gravely noted, that wasps<span class="pagenum" id="Page_248">[Pg 248]</span>
+were very few in number; that flies became blind,
+and disappeared early; and that twins were born more
+frequently than usual. The season was remarkable
+for its bountiful harvest and abundant vintage. Grapes,
+figs, melons, and other fruits, were not only produced
+in extraordinary quantity, but of delicious flavor, so
+that “comet wines” had distinct bins allotted to them
+in the cellars of merchants, and were sold at high
+prices. There is, however, no fact better attested, by
+a comparison of observations, than that comets have
+no influence whatever in heightening or depressing
+the temperature of the seasons. The fine fruits and
+ample harvest of the year in question were, therefore,
+coincidences merely with the celestial phenomenon,
+without the slightest physical connection with it.</p>
+
+<p>Though the advanced civilization of recent times
+has led to juster views of cometary apparitions than
+to regard them as divinely-appointed omens of terrestrial
+calamity, yet society is apt to be nervous respecting
+these bodies, as likely to cause some great natural
+convulsion by collision with our globe.</p>
+
+<p>The great comet, which in 1682 received first the
+name of Halley’s comet, appeared last in 1835, his
+return having been foretold within three days of its
+actually taking place. For Halley’s comet is a member
+of the Solar System, having a yearly journey of
+seventy-six earthly years. He journeys nearer the
+sun than Venus, and travels farther away than
+Neptune.</p>
+
+<p>In the years 1858, 1861, and 1862, three more
+comets appeared, all visible without the help of a
+telescope. Of these three, Donati’s comet, in 1858,<span class="pagenum" id="Page_249">[Pg 249]</span>
+was far superior to the rest. This fine object was
+first discovered on the 2d of June by Dr. Donati, at
+Florence. It appeared at first as a faint nebulous
+patch of light, without any remarkable condensation;
+and as its motion towards the sun at that time was
+slow, it was not till the beginning of September that
+it became visible to the naked eye. A short tail was
+then seen on the side opposite to the sun.</p>
+
+<div class="figcenter" id="f42">
+<img src="images/fig42.jpg" alt="1858">
+<p class="caption">DONATI’S COMET, 1858.</p>
+</div>
+
+<p>The development was afterwards rapid, and the
+comet became equally interesting to the professional
+astronomer and to the unlearned gazer. In the first
+week of October the tail attained its greatest length,
+36°. At this time the tail was sensibly curved, and<span class="pagenum" id="Page_250">[Pg 250]</span>
+had the appearance of a large ostrich-feather when
+waved gently in the hand. At the latter end of October
+the comet was lost in the evening twilight. Its
+nearest approach to the earth was about equal to half
+the distance of the earth from the sun, and the nearest
+approach to Venus was about one-ninth part of that
+distance. An elliptical orbit, with a periodic time of
+more than 2,000 years, has been assigned to our late
+visitor.</p>
+
+<p>It was a singular fact about this comet that at one
+time the star Arcturus could be seen shining through
+the densest portion of the tail, close to the nucleus.
+Now, although the faintest cloud-wreath of earth
+would dim, if not hide, this star, yet the tail of the
+great comet was of so transparent a nature that Arcturus
+shone undimmed, as if no veil had come between.
+The exceedingly slight and airy texture of a
+comet’s tail could hardly be more plainly shown. It
+was this gauzy appendage to a little nucleus which
+men once thought could destroy our solid earth at a
+single blow!</p>
+
+<p>These cometary trains generally appear straight,
+or at least, by the effect of perspective, they seem to
+be directed along the arcs of great circles of the celestial
+sphere. Some are recorded, however, which presented
+a different appearance. Thus, in 1689, a comet
+was seen whose tail, according to the historians, was
+curved like a Turkish saber. This tail had a total
+length of 68°. It was the same with the beautiful
+comet of Donati, which we admired in 1858, and of
+which the tail had a very decided curvature.</p>
+
+<p>A comet can only be observed in the sky for a<span class="pagenum" id="Page_251">[Pg 251]</span>
+limited time. We perceive it at first in a region
+where nothing was visible on preceding days. The
+next day, the third day, we see it again; but it has
+changed its place considerably among the constellations.
+We can thus follow it in the sky for a certain
+number of days, often during several months; then we
+cease to perceive it. Often the comet is lost to view
+because it approaches the sun, and the vivid light of
+that body hides it completely; but soon we observe it
+again on the other side of the sun, and it is not till
+some time afterwards that it definitely disappears.
+Some have been visible at noonday, quite near the
+sun, like that of 1882, on September 17th.</p>
+
+<p>Yet, while taking care not to overrate, we must not
+underrate. True, the comets are delicate and slight
+in structure. One comet, in 1770, wandered into the
+very midst of Jupiter’s moons, and so small was its
+weight that it had no power whatever, so far as has
+been detected, to disturb the said moons in their orbits.
+Jupiter and his moons did very seriously disturb
+the comet, however; and when he came out
+from their midst, though none the worse for his adventure,
+he was forced to travel in an entirely new
+orbit, and never managed to get back to his old pathway
+again.</p>
+
+<p>But there are comets <i>and</i> comets, some being
+heavier than others. The comet named after Donati,
+albeit too transparent to hide a star, was yet so immense
+in size that his weight was calculated by one
+astronomer to amount to as much as a mass of water
+forty thousand miles square and one hundred and nine
+yards deep.</p>
+
+<p><span class="pagenum" id="Page_252">[Pg 252]</span></p>
+
+<p>When first noticed, Donati’s comet had, like all
+large comets, a bright envelope of light round the
+nucleus. After a while the one envelope grew into
+three envelopes, and a new tail formed beside the
+principal tail, which for a time was seen to bend
+gracefully into a curve, like a splendid plume. A
+third, but much fainter tail, also made its appearance,
+and many angry-looking jets were poured out from
+the nucleus. These changes took place while the
+comet was passing through the great heat of near
+neighborhood to the sun. Afterwards, as he passed
+away, he seemed gradually to cool down and grow
+quiet. The singular changes in the appearance of Newton’s
+comet have been earlier noticed. No marvel
+that he did undergo some alterations. The tremendous
+glare and burning heat which that comet had to
+endure in his rush past the sun, were more than
+twenty-five thousand times as much as the glare and
+heat of the fiercest tropical noonday ever known upon
+earth. Can we wonder that he should have shown
+“signs of great excitement,” that his head should have
+grown larger and his tail longer?</p>
+
+<p>It certainly was amazing, and past comprehension,
+that the said tail, over ninety millions of miles in
+length, should in four days have seemingly swept
+round in a tremendous half-circle, so as first to point
+in one direction, and then to point in just the opposite
+direction.</p>
+
+<p>We are much in the habit of speaking about
+comets as traveling through the heavens with their
+tails streaming behind them. But though this is
+sometimes the case, it is by no means always.</p>
+
+<p><span class="pagenum" id="Page_253">[Pg 253]</span></p>
+
+<p>The tails of comets always stream <i>away from the
+sun</i>—whether before or behind the comet’s head seeming
+to be a matter of indifference. As the comet comes
+hurrying along his orbit, with ever-increasing speed,
+towards the sun, the head journeys first, and the long
+tail follows after. But as the comet rounds the loop
+of his orbit near the sun—the point nearest of all
+being called his <i>perihelion</i>—the head always remains
+towards the sun, while the tail swings, or seems to
+swing, in a magnificent sweep round, pointing always
+in the direction just away from the sun.</p>
+
+<p>Then, as the comet journeys with slackening speed,
+on the other side of his orbit, towards the distant
+<i>aphelion</i>, or farthest point from the sun, he still keeps
+his head towards the sun. So, at this part of his
+passage, in place of the head going first and the tail
+following after, the tail goes first and the head follows
+after. The comet thus appears to be moving backwards;
+or, like an engine pushing instead of drawing
+a train, the head seems to be driving the tail
+before it.</p>
+
+<div class="figcenter" id="f43">
+<img src="images/fig43.jpg" alt="1744">
+<p class="caption">GREAT COMET OF 1744.</p>
+</div>
+
+<div class="figcenter1" id="f44">
+<img src="images/fig44.jpg" alt="1888">
+<p class="caption">THE FIRST COMET OF 1888—JUNE 4.</p>
+</div>
+
+<p>The sun, then, acts on these bodies when they approach
+him, produces in them important physical and
+chemical transformations, and exercises on their developed
+atmosphere a repulsive force, the nature of
+which is still unknown to us, but the effects of which
+coincide with the formation and development of the
+tails. The tails are thus, in the extension of the
+cometary atmosphere, driven back, either by the solar
+heat, by the light, by electricity, or by other forces;
+and this extension is rather a motion in the ether than
+a real transport of matter, at least in the great comets
+<span class="pagenum" id="Page_254">[Pg 254]</span>which approach very near the sun, and in their immense
+luminous appendages. The effects produced
+and observed are not the same in all comets, which
+proves that they differ from each other in several respects.
+The tails have sometimes been seen to diminish
+before the perihelion passage, as in 1835.
+<span class="pagenum" id="Page_255">[Pg 255]</span>Luminous envelopes have also been seen succeeding
+each other round the head, concentrating themselves
+on the side opposite to the sun, and leaving the central
+line of the tail darker than the two sides. This
+is what happened in the Donati comet and in that of
+1861. Sometimes a secondary tail has been seen projected
+towards the sun, as in 1824, 1850, 1851, and
+1880. Comets have been seen with the head enveloped
+in phosphorescence, surrounding them with a
+sort of luminous atmosphere. Comets have also been
+seen with three, four, five, and <i>six tails</i>, like that of
+1744, for example, which appeared like a splendid
+aurora borealis rising majestically in the sky, until,
+the celestial fan being raised to its full height, it was
+perceived that the six jets of light all proceeded from
+the same point, which was nothing else but the nucleus
+of a comet. On the other hand, the nuclei
+themselves show great variations—some appear simply
+nebulous, and permit the faintest stars to be visible<span class="pagenum" id="Page_256">[Pg 256]</span>
+through them; others seem to be formed of one
+or more solid masses surrounded by an enormous atmosphere;
+in others, again, a nucleus does not exist,
+as in the Southern comet of 1887. One of the comets
+of 1888 showed a triple nucleus and a bristling coma,
+as may be seen in the cut. We may, then, consider
+that the wandering bodies collected under the name
+of comets are of several origins and <i>several different
+species</i>.</p>
+
+<p><i>Why</i> the tails of comets should so persistently
+avoid the sun it is impossible to say. We do not
+even know whether the cause lies actually in the sun
+or in the comet. Astronomers speak of the “repulsive
+energy” with which the sun “sweeps away” from his
+neighborhood the light vapory matter of which the
+tails are made. But the how and the wherefore of
+this strange seeming repulsion they can not explain.
+For at the selfsame time the sun appears to be attracting
+the comet towards himself, and driving the comet’s
+tail away from himself.</p>
+
+<p>A few of the more well-known comets have been
+mentioned; but a year rarely passes in which at least
+one comet is not discovered, though often only a small
+specimen, sometimes even tailless and hairless. No
+doubt many others pass unseen. The large and grand
+ones only come to view now and then.</p>
+
+<p>What are comets and meteorites made of? Respecting
+comets, a good many ideas are put forth, and
+a good many guesses are made, as to “burning gas,”
+“luminous vapor,” “beams of light,” and so on. But
+in truth, little is known about the matter. Respecting
+meteorites, we can speak more certainly. A good<span class="pagenum" id="Page_257">[Pg 257]</span>
+many meteorites have fallen to earth as aerolites, and
+have been carefully examined. They are found to
+contain nickel, cobalt, iron, phosphorus, and sometimes
+at least, a large supply of hydrogen gas.</p>
+
+<p>Not only do solid aerolites fall half-burnt to the
+ground, but even when the meteorites are quite consumed
+in the air, the fine dust remaining still sinks
+earthward. This fine dust has been found upon
+mountain-tops, and has been proved by close examination
+to be precisely the same as the material of the
+solid aerolites.</p>
+
+<p>A luminous body of sensible dimensions rapidly
+traverses space, diffusing on all sides a vivid light—like
+a globe of fire of which the apparent size is often
+comparable with that of the moon. This body usually
+leaves behind it a perceptible luminous train. On or
+immediately after its appearance it often produces an
+explosion, and sometimes even several successive explosions,
+which are heard at great distances. These
+explosions are also often accompanied by the division
+of the globe of fire into luminous fragments, more or
+less numerous, which seem to be projected in different
+directions. This phenomenon constitutes what is
+called a <i>meteor</i>, properly speaking, or a <i>bolide</i>. It is
+produced during the day as well as the night. The
+light which it causes in the former case is greatly enfeebled
+by the presence of the solar light, and it is
+only when it is developed with sufficient intensity that
+it can be perceived.</p>
+
+<p>In the British Museum there is a superb collection
+of meteorites. They have been brought together from
+all parts of the earth, and vary in size from bodies not<span class="pagenum" id="Page_258">[Pg 258]</span>
+much larger than a pin’s-head up to vast masses
+weighing many hundred pounds. There are also
+many models of celebrated meteorites, of which the
+originals are dispersed through various other museums.</p>
+
+<p>Many of these objects have nothing very remarkable
+in their external appearance. If they were met
+with on the sea-beach, they would be passed by without
+more notice than would be given to any other
+stone. Yet what a history such a stone might tell us
+if we could only manage to obtain it! It fell; it was
+seen to fall from the sky; but what was its course anterior
+to that movement? Where was it one hundred
+years ago, one thousand years ago? Through what
+regions of space has it wandered? Why did it never
+fall before? Why has it actually now fallen? Such
+are some of the questions which crowd upon us as we
+ponder over these most interesting bodies. Some of
+these objects are composed of very characteristic materials.
+Take, for example, one of the more recent meteorites,
+known as the Rowton siderite. This body differs
+very much from the more ordinary kind of stony meteorite.
+It is an object which even a casual passer-by
+would hardly pass without notice. Its great weight
+would also attract attention, while if it be scratched
+or rubbed with a file, it would be found that it was
+not in any sense a stone, but that it was a mass of
+nearly pure iron. We know the circumstances under
+which that piece of iron fell to the earth. It was on
+the 20th of April, 1876, about 3.40 P. M., that a strange
+rumbling noise, followed by a startling explosion, was
+heard over an area of several miles in extent among
+the villages in Shropshire. About an hour after this<span class="pagenum" id="Page_259">[Pg 259]</span>
+occurrence, a farmer noticed the ground in one of his
+grass-fields to have been disturbed, and he probed the
+hole which the meteorite had made, and found it, still
+warm, about eighteen inches below the surface. Some
+men working at no great distance had actually heard
+the noise of its descent, but without being able to indicate
+the exact locality. This remarkable object
+weighs 7¾ pounds. It is an irregular angular mass
+of iron, though all its edges seem to have been rounded
+by fusion in its transit through the air, and it is covered
+with a thick black film of the magnetic oxide of
+iron, except at the point where it first struck the
+ground.</p>
+
+<p>This siderite is specially interesting on account of
+its distinctly metallic character. Falls of the siderites,
+as they are called, are not so common as those of the
+stony meteorites; in fact, there are only a few known
+instances of meteoric irons having been actually seen
+to fall, while the falls of stony meteorites are to be
+counted in scores or in hundreds. The inference is
+that the iron meteorites are much less frequent than
+the stony ones.</p>
+
+<p>It is a wonderful thought that we should really have
+these visitants from the sky, solid metal or showers of
+dust, coming to us from distant space.</p>
+
+<p>If the dust of thousands of meteorites is always
+thus falling earthward, one would imagine that it
+must in time add something to the weight of the
+earth. And this actually is the case. During the last
+three thousand years, no less than one million tons of
+meteorite-dust must, according to calculation, have
+fallen to earth out of the sky. A million tons is of<span class="pagenum" id="Page_260">[Pg 260]</span>
+course a mere nothing compared
+with the size of the world. Still,
+the fact is curious and interesting.</p>
+
+<p>It has been suggested that, <i>perhaps</i>
+the flames of the sun are
+partly fed by vast showers of falling
+meteorites. It has even been
+suggested that <i>perhaps</i>, in long
+past ages, the earth and the planets
+grew to their present size under
+a tremendous downpour of
+meteorites; the numbers which
+now drop to earth being merely
+the thin remains of what once
+existed. But for this guess there
+is no real foundation.</p>
+
+<p>Whether suns and worlds full-grown,
+created as in an instant;
+whether tiny meteorites in countless
+myriads to be used as stones
+in “building;” whether vast
+masses of flaming gas, to be gradually
+cooled and “framed” into
+shape—which ever may have
+come first, and whichever may
+have been the order of God’s
+working—still that “first” was
+made by him; still he throughout
+was the Master-builder.</p>
+
+<div class="figleft" id="f45">
+<img src="images/fig45.jpg" alt="1680">
+<p class="caption">GREAT COMET OF 1680.</p>
+</div>
+
+<p>A few words more about
+“comet-visitors.” Many comets,
+as already stated, belong to our<span class="pagenum" id="Page_261">[Pg 261]</span>
+Solar System, though
+whether they have always
+so belonged is another
+question. It is
+not impossible that they
+may once upon a time
+have wandered hence
+from a vast distance,
+and, being caught prisoner
+by the powerful attraction
+of Jupiter or
+one of his three great
+brother-planets, have
+been compelled thenceforth
+to travel in a closed
+pathway round the sun.</p>
+
+<div class="figright" id="f46">
+<img src="images/fig46.jpg" alt="1769">
+<p class="caption">GREAT COMET OF 1769.</p>
+</div>
+
+<p>There are also many
+comets which come once
+only to our system, flashing
+round past the sun,
+and rushing away in
+quite another direction,
+never to return. Where
+do these comets come
+from? And where do
+they go? From other
+suns—brother suns to
+ours? It may be. One
+is almost disposed to
+think that it must be so.</p>
+
+<p>Do we ever think
+what an immense voyage<span class="pagenum" id="Page_262">[Pg 262]</span>
+they must have made to come from there to here? Do
+we imagine for how many years they must have flown
+through the dark immensity to plunge themselves into
+the fires of our sun? If we take into account the directions
+from which certain comets come to us, and if
+we assign to the stars situated in that region the least
+distances consistent with known facts, we find that
+these comets certainly left their last star more than
+<i>twenty millions of years ago</i>.</p>
+
+<p>In thus putting to us from the height of their celestial
+apparitions so many notes of interrogation on
+the grandest problems of creation, comets assume to
+our eyes an interest incomparably greater than that
+with which superstition blindly surrounded them in
+past ages. When we reflect for a moment that a certain
+comet which shines before us in the sky came
+originally from the depths of the heavens, that it has
+traveled during millions of years to arrive here, and
+that consequently it is by millions of years that we
+must reckon its age if we wish to form any idea of it,
+we can not refrain from respecting this strange visitor
+as a witness of vanished eras, as an echo of the past,
+as the most ancient testimony which we have of the
+existence of matter. But what do we say? These
+bodies are neither old nor young. There is nothing
+old, nothing new—all is present. The ages of the
+past contemplate the ages of the future, which all
+work, all gravitate, all circulate, in the eternal plan.
+Musing, you look at the river which flows so gently
+at your feet, and you believe you see again the river
+of your childhood; but the water of to-day is not that
+of yesterday, it is not the same substance which you<span class="pagenum" id="Page_263">[Pg 263]</span>
+have before your eyes, and never, never shall this
+union of molecules, which you behold at this moment,
+come back there—never till the consummation of
+the ages!</p>
+
+<p>If the appearance of comets forebodes absolutely
+nothing as to the microscopical events of our ephemeral
+human history, it is not the same with the effects
+which might be produced by their encounter with our
+wandering planet. In such an encounter there is
+nothing impossible. No law of celestial mechanics
+forbids that two bodies should come into collision in
+their course, be broken up, pulverized, and mutually
+reduced to vapor.</p>
+
+<p>I have before described some of the tremendous
+outbursts seen on the surface of our sun. It is believed
+that in these outbursts matter is expelled, or
+driven forth, with such fearful violence as to send it
+whirling through space, never to fall back to the sun.</p>
+
+<p>Some meteorites may have their births thus. So
+also may some comets. And if all the stars are suns—huge
+fiery globes like our sun, and subject like him
+to tremendous eruptions—they too, probably, send out
+comets and meteorites to wander through space.
+Whether or no comets come into existence in any such
+manner, one thing seems pretty certain. Those comets
+which come to us from outside our system must
+come from some other system. And the nearest systems
+known are those of the stars.</p>
+
+<p>The nearest star of all, whose distance has been
+measured, is Alpha Centauri. It has been roughly
+calculated that a comet, passing direct from Alpha
+Centauri to our sun, would take about twenty millions<span class="pagenum" id="Page_264">[Pg 264]</span>
+of years for his journey. But here we tread upon
+very doubtful ground. Many matters, at present unknown
+to us, might greatly affect the result of such a
+calculation. Also it is by no means impossible that
+other stars lie really much nearer to us than Alpha
+Centauri, whose distance astronomers have not yet
+attempted to measure.</p>
+
+<div class="figcenter" id="f47">
+<img src="images/fig47.jpg" alt="humboldt">
+<p class="caption">BARON ALEXANDER VON HUMBOLDT.</p>
+</div>
+
+<p>“In order to complete our view,” says Alexander<span class="pagenum" id="Page_265">[Pg 265]</span>
+Von Humboldt, “of all that we have learned to consider
+as appertaining to our Solar System, which now,
+since the discovery of the small planets, of the interior
+comets of short revolutions, and of the meteoric
+asteroids, is so rich and complicated in its form, it
+remains for us to speak of the ring of zodiacal light.
+Those who have lived for many years in the zone of
+palms must retain a pleasing impression of the mild
+radiance with which the zodiacal light, shooting
+pyramidally upward, illumines a part of the uniform
+length of tropical nights. I have seen it shine with
+an intensity of light equal to the Milky Way in Saggitarius,
+and that not only in the rare and dry atmosphere
+of the summit of the Andes, at an elevation of
+from thirteen to fifteen thousand feet, but even on the
+boundless grassy plains of Venezuela, and on the seashore,
+beneath the ever-clear sky of Cumana. This
+phenomenon was often rendered especially beautiful
+by the passage of light, fleecy clouds, which stood out
+in picturesque and bold relief from the luminous background.</p>
+
+<p>“This phenomenon, whose primordial antiquity
+can scarcely be doubted, is not the luminous solar atmosphere
+itself, which can not be diffused beyond
+nine-tenths of the distance of Mercury. With much
+probability we may regard the existence of a very
+compressed ring of nebulous matter, revolving freely
+in space around the sun between the orbits of Venus
+and Mars, as the material cause of the zodiacal light.
+These nebulous particles may either be self-luminous
+or receive their light from the sun.</p>
+
+<p>“I have occasionally been astonished, in the tropical<span class="pagenum" id="Page_266">[Pg 266]</span>
+climates of South America, to observe the variable
+intensity of the zodiacal light. As I passed the nights,
+during many months, in the open air, on the shores of
+rivers and on plains, I enjoyed ample opportunities of
+carefully examining this phenomenon. When the
+zodiacal light had been most intense, I have observed
+that it would be weakened for a few minutes, until it
+again suddenly shone forth in full brilliancy. In a
+few instances I have thought I could perceive, not
+exactly a reddish coloration, nor the lower portion
+darkened in an arc-like form, nor even a scintillation,
+but a kind of flickering and wavering of the light.
+Must we suppose that changes are actually in progress
+in the nebulous ring? Or is it not more probable that
+processes of condensation may be going on in the uppermost
+strata of the air, by means of which the transparency—or,
+rather, the reflection of light—may be
+modified in some peculiar and unknown manner? An
+assumption of the existence of such meteorological
+causes on the confines of our atmosphere is strengthened
+by the sudden flash and pulsations of light which
+have been observed to vibrate for several seconds
+through the tail of a comet. During the continuation
+of these pulsations it has been noticed that the
+comet’s tail was lengthened by several degrees, and
+then again contracted.”</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_267">[Pg 267]</span></p>
+
+<h2 class="nobreak" id="c22">CHAPTER XXII.</h2>
+</div>
+
+<p class="c sp">MANY SUNS.</p>
+
+
+<p><span class="smcap large">Once</span> more we have to wing our flight far, far away
+from the busy Solar System where we live; away from
+whirling planets, moons, meteorites, all shining with
+reflected sunlight; away from the great central sun
+himself, our own particular bright star. Once more
+we have, in imagination, to cross the vast, black,
+empty space—<i>is</i> it black, and <i>is</i> it empty, had we
+sight to see things as they are?—separating our sun
+from other suns, our star from other stars. For the
+sun is a star—only a star. And stars are suns—big,
+blazing suns. One is near, and the others are far
+away. That is the difference.</p>
+
+<p>We have no longer to do with bodies merely reflecting
+another’s light—always dark on one side and
+bright on the other—but with burning bodies, shining
+all round by their own light. We have no longer to
+picture just one single star with his surrounding
+worlds, but we have to fix our thoughts upon the
+great universe of stars or suns in countless millions.</p>
+
+<p>The earth is forgotten, with its small and ephemeral
+history. The sun himself, with all his immense
+system, has sunk in the infinite night. On the wings
+of inter-sidereal comets we have taken our flight towards
+the stars, the suns of space. Have we exactly
+measured, have we worthily realized the road passed
+over by our thoughts? The nearest star to us reigns
+at a distance of 275,000 times our distance from the<span class="pagenum" id="Page_268">[Pg 268]</span>
+sun; out to that star an immense desert surrounds us,
+the most profound, the darkest, and the most silent
+of solitudes.</p>
+
+<p>The solar system seems to us very vast; the abyss
+which separates our world from Mars, Jupiter, Saturn,
+and Neptune, appears to us immense; relatively to
+the fixed stars, however, our whole system represents
+but an isolated family immediately surrounding us:
+a sphere as vast as the whole solar system would be
+reduced to the size of a simple point if it were transported
+to the distance of the nearest star. The space
+which extends between the solar system and the stars,
+and which separates the stars from each other, appears
+to be entirely void of visible matter, with the exception
+of nebulous fragments, cometary or meteoric,
+which circulate here and there in the immense voids.
+Nine thousand two hundred and fifty systems like
+ours, bounded by Neptune, would be contained in the
+space which isolates us from the nearest star!</p>
+
+<p>It is marvelous that we can perceive the stars at
+such a distance. What an admirable transparency
+in these immense spaces to permit the light to pass,
+without being wasted, to thousands of billions of
+miles! Around us, in the thick air which envelops
+us, the mountains are already darkened and difficult
+to see at seventy miles; the least fog hides from us
+objects on the horizon. What must be the tenuity,
+the rarefaction, the extreme transparency of the ethereal
+medium which fills the celestial spaces!</p>
+
+<p>The sun is center and ruler and king in his own
+system. But as a star, he is only one among many
+stars, some greater, some less than himself. From the<span class="pagenum" id="Page_269">[Pg 269]</span>
+far siderial heavens he is hardly recognized even as a
+star among the constellations, so faint is his light.</p>
+
+<p>Do the suns which surround us form a system
+with that which illuminates us, as the planets form
+one round our solar focus, and does our sun revolve
+round an attractive center? Does this center, the
+point of the revolutions of many suns, itself revolve
+round a preponderating center? In a word, is the
+visible universe organized in one or several systems?
+No Divine revelation comes to instruct men on the
+mysteries which interest them most—their personal or
+collective destinies. We have now, as ever, but science
+and observation to answer us.</p>
+
+<p>A problem so vast as this is still far from receiving
+even an approximate solution. From whatever point
+of view we consider it, we find ourselves face to face
+with the infinite in space and time. The present aspect
+of the universe immediately brings into question
+its past and its future state, and then the whole of
+united human learning supplies us in this great research
+with but a pale light, scarcely illuminating the
+first steps of the dark and unknown road on which we
+are traveling. However, such a problem is worthy of
+engaging our attention, and positive science has already
+made sufficient discoveries in the knowledge of
+the laws of nature to permit us to attempt to penetrate
+these great mysteries. What is it that the general
+observation of the heavens—what is it that sidereal
+synthesis teaches us on our real situation in
+infinitude?</p>
+
+<div class="figcenter" id="f48">
+<img src="images/fig48.jpg" alt="field">
+<p class="caption">A TELESCOPIC FIELD IN THE MILKY WAY.</p>
+</div>
+
+<p>In the calm and silent hours of beautiful evenings,
+what pensive gaze is not lost in the vague windings
+<span class="pagenum" id="Page_270">[Pg 270]</span>of the Milky Way, in the soft and celestial gleam of
+that cloudy arch, which seems supported on two opposite
+points of the horizon, and elevated more or less
+in the sky according to the place of the observer and
+the hour of the night? While one-half appears above
+the horizon, the other sinks below it, and if we removed
+the earth, or if it were rendered transparent,
+we should see the complete Milky Way, under the
+form of a great circle, making the whole circuit of the
+sky. The scientific study of this trail of light, and
+its comparison with the starry population of the<span class="pagenum" id="Page_271">[Pg 271]</span>
+heavens, begins for us the solution of the great
+problem.</p>
+
+<p>Let us point a telescope towards any point of this
+stupendous arch. Suddenly hundreds, thousands of
+stars show themselves in the telescopic field, like
+needle-points on the celestial vault. Let us wait for
+some moments, that our eye may become accustomed
+to the darkness of the background, and the little
+sparks shine out by thousands. Let us leave the instrument
+pointed motionless towards the same region,
+and there slowly passes before our dazzled vision the
+distant army of stars. In a quarter of an hour we
+see them appear by thousands and thousands. William
+Herschel counted three hundred and thirty-one
+thousand in a width of 5° in the constellation Cygnus,
+so nebulous to the naked eye. If we could see the
+whole of the Milky Way pass before us, we should see
+eighteen millions of stars.</p>
+
+<p>This seed-plot of stars is formed of objects individually
+invisible to the naked eye, below the sixth
+magnitude; but so crowded that they appear to touch
+each other, and form a nebulous gleam which all human
+eyes, directed to the sky for thousands of years,
+have contemplated and admired. Since it is developed
+like a girdle round the whole circuit of the sky,
+we ourselves must be in the Milky Way. The first
+fact which impresses our mind is, that <i>our sun is a star
+of the Milky Way</i>.</p>
+
+<p>Thought travels fast—faster than a comet, faster
+than light. A rushing comet would, it is believed,
+take twenty millions of years to cross the chasm between
+the nearest known fixed star and us. Light,<span class="pagenum" id="Page_272">[Pg 272]</span>
+flashing along at the rate of about one hundred and
+eighty-six thousand miles a second, will perform the
+same journey in four years and a third. But thought
+can overleap the boundary in less than a single
+moment.</p>
+
+<p>Each star that we see in the heavens is to our eyesight
+simply one point of light. The brighter stars
+are said to be of greater magnitude, and the fainter
+stars of lesser magnitude; yet, one and all, they have
+no apparent size. The most powerful telescope, though
+it can increase their brilliancy, can not add to their
+size. A planet, which to the naked eye may look like
+a star, will, under a telescope, show a disk, the breadth
+of which can be measured or divided; but no star has
+any real, visible disk in the most powerful telescope
+yet constructed. The reason of this is the enormous
+distance of the stars. Far off as many of the planets
+lie, yet the farthest of them is as a member of our
+household compared with the nearest star.</p>
+
+<p>I have already tried to make clear the fact of their
+vast distance. Light, which comes to us from the
+sun in eight minutes and a half, takes over four and a
+third years to reach us from Alpha Centauri. From
+this four-years-and-a-third length of journey between
+Alpha Centauri and earth, the numbers rise rapidly to
+twenty years, fifty years, seventy years, even hundreds
+of years. The distance of most of the stars is completely
+beyond our power to measure. The whole
+orbit of our earth, nay, the whole wide orbit of the
+far-off Neptune, would dwindle down to one single
+point, if seen from the greater number of the stars.</p>
+
+<p>It used to be believed that, taking the stars generally,<span class="pagenum" id="Page_273">[Pg 273]</span>
+there was probably no very marked difference
+in their size, their kind, their brightness. Some of
+course would be rather larger, and others rather
+smaller; still it was supposed that they might be
+roughly classed as formed much on the same scale
+and the same plan. But doubts are now felt about
+this notion. For a very similar idea used to be held
+with regard to the Solar System. The wonderful variety
+of form and richness in numbers, now known to
+abound within its limits, are discoveries of late years.
+May not the same variety in kind and size be found
+also among the stars? The more we look into the
+heavens, the more we find that dull, blank uniformity
+is not to be seen there.</p>
+
+<p>It is the same upon earth. Man builds his little
+rows of boxlike houses side by side, each one exactly
+like all the rest, or dresses his thousand soldiers in
+coats of the same cut and color, or repeats a neat leaf-design
+hundreds of times on carpets or wall-papers;
+but God never makes two leafs or two blades of grass
+alike. Wholesale turning out of things after one pattern
+is quite a human idea, not divine.</p>
+
+<p>We know so much about the stars as that some are
+at least considerably larger and some considerably
+smaller than others. When one star is seen to shine
+brightly, and another beside it shines dimly, we are
+apt to think that the brightest must be the nearest.
+Yet it is often impossible for us to say how much
+of the difference is owing to the greater distance of
+one or the other, to the greater size of one or the
+other, or to the greater brilliancy of one or the other.
+In many instances we do know enough to be quite<span class="pagenum" id="Page_274">[Pg 274]</span>
+sure that there is a great difference, not only in the
+distance of the stars, but in their size, their kind, their
+brightness.</p>
+
+<p>The stars have been lately classed by one or two
+astronomers into four distinct orders or degrees—partly
+depending on their color. The first class is
+that of the White Suns. These are said to be the
+grandest and mightiest of all. The star Sirius belongs
+to the order of White Suns. Secondly comes
+the class of Golden Suns. To these blazing furnaces
+of yellow light, second only to the white-light stars,
+belongs our own sun. Thirdly, there are numbers of
+stars called Variable Stars, the light of which is constantly
+changing, now becoming more, now becoming
+less. Fourthly, there is the class of small Red Suns,
+about which not much is known.</p>
+
+<p>These four orders or divisions do not by any means
+include all the stars, or even all the single stars.
+Roughly speaking, however, the greater number of
+single stars, and many also of the double stars, belong
+to one or another of the above classes.</p>
+
+<p>When we talk of the different sizes of the different
+stars, it should be plainly understood that we have no
+means of directly measuring them. A point of light
+showing no disk, no surface, no breadth, can not be
+measured, for there is nothing to measure.</p>
+
+<p>In certain cases we are not entirely without the
+power of judging. The distances of a few of the
+stars from us have been found out. Knowing how
+far off any particular star is, astronomers are able to
+calculate exactly how bright our own sun would look
+at that same distance. If they find that our sun<span class="pagenum" id="Page_275">[Pg 275]</span>
+would shine just as the star in question shines, there
+is some reason for supposing that our sun and the
+star may be of the same size. If our sun would
+shine more brightly than the star shines, there is
+some reason for supposing that the star may be
+smaller than our sun. If our sun would shine more
+dimly than the star shines, there is some reason for
+supposing that the star may be larger than our sun.</p>
+
+<p>Other matters, however, have to be considered.
+Suppose we find a star at a certain distance shining
+twice as brilliantly as our own sun would shine at
+that same distance. Naturally, then, we say, That
+star must be much larger than our sun.</p>
+
+<p>The reasoning may be mistaken. We do not know
+the fact. What if, instead of being a much <i>larger</i>
+sun, it is only a much <i>brighter</i> sun? This possibly
+must be allowed for. It has, indeed, been strongly
+doubted by one astronomer, after close study of the
+sun, whether any surface of any star <i>could</i> exceed the
+surface of our sun in its power of light and heat.</p>
+
+<p>But Sirius sheds actually forty-eight times as much
+light around it as does our sun; we are not exactly
+entitled to say that Sirius is forty-eight times as big as
+the sun, but we can say that Sirius is forty-eight times as
+brilliant or as splendid. In making this calculation
+we have taken a lower determination of the brightness
+of Sirius relatively to the sun than some other
+careful observations would have warranted. It will
+thus be seen that if there be any uncertainty in
+our result it must only be as to whether Sirius is not
+really more than forty-eight times as bright as the
+sun.</p>
+
+<p><span class="pagenum" id="Page_276">[Pg 276]</span></p>
+
+<p>When we picture to ourselves the star-depths, the
+boundless reaches of heavenly space, with these countless
+blazing suns scattered broadcast throughout, we
+have not to picture an universe in repose. On the
+contrary, all is life, stir, energy. Just as in the busy
+whirl of our Solar System no such thing as rest is to
+be found, so also it seems to be in the wide universe.</p>
+
+<p>Every star is in motion. “Fixed,” as we call
+them, they are not fixed. Invisible as their movements
+are to our eyes through immensity of distance,
+yet all are moving. Those silent, placid, twinkling
+specks of light are, in reality, huge, roaring, seething,
+tumultuous furnaces of fire and flame, heat and
+radiance.</p>
+
+<p>Each, too, is hurrying along his appointed pathway
+in space. Some move faster, some move more slowly.
+One mile per second; ten miles per second; twenty,
+thirty, forty, fifty miles per second,—thus varying are
+their rates of speed. But whether fast or whether
+slowly, still onward and ever onward they press.
+Some are rushing towards us, some are rushing away
+from us. Some are speeding to the right, some are
+speeding to the left.</p>
+
+<p>The fine star Arcturus, which any one may admire
+every evening on the prolongation of the tail of the
+Great Bear, is slowly withdrawing from the fixed point
+where the celestial charts placed it two thousand years
+ago, and is moving towards the southwest. It takes
+eight hundred years to describe a space in the sky
+equal to the apparent diameter of the moon; nevertheless,
+this displacement was sufficiently perceptible
+to attract attention more than a century and a half<span class="pagenum" id="Page_277">[Pg 277]</span>
+ago, for Halley had noticed it in 1718, as well as those
+of Sirius and Aldebaran. However slow it may appear
+at the distance we are from Arcturus, this motion
+is, at a minimum, 1,637 millions of miles a year.
+Sirius takes 1,338 years to pass over the same angular
+space in the sky; at the distance of that star this is,
+at a minimum, 397 millions of miles per annum. The
+study of the proper motions of the stars has made the
+greatest progress in the last half-century, and especially
+in recent years. All the stars visible to the
+naked eye and a large number of telescopic stars
+show displacements of this kind.</p>
+
+<p>Where are they going? Does any single star ever
+return to his starting-point—wherever that starting-point
+may have been? Do they journey in vast circles
+or ellipses, round some far-distant center? What
+controls them all? Is it the mighty power of some
+such center, or does each star, by his faint and distant
+attraction, help to control all his brother-stars, to guide
+them on their appointed path, to preserve the delicate
+balance of a universe?</p>
+
+<p>How little we know about the matter! Only so
+much we can tell—that the controlling and restraining
+hand of God is over the whole. Whether by the
+attraction of one great center or by the united influences
+of a thousand fainter attractions, he steers each
+radiant sun upon its heavenly path, “upholding all
+things by the words of his power.” There is no
+blundering, no confusion, no entanglement. All is
+perfect order, calm arrangement, restrained energy.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_278">[Pg 278]</span></p>
+
+<h2 class="nobreak" id="c23">CHAPTER XXIII.</h2>
+</div>
+
+<p class="c sp">SOME PARTICULAR SUNS.</p>
+
+
+<p><span class="smcap large">In</span> the constellation of the Swan there is a little,
+dim, sixth-magnitude star, scarcely to be seen without
+a telescope. This star, 61 Cygni by name, is the first
+whose distance from us it was found possible to determine.</p>
+
+<p>We may think it strange that so faint a star was
+even attempted. Would not astronomers have naturally
+supposed it to be one of the farther-distant
+stars? No, they did not. For though 61 Cygni
+showed but a dim light, yet his motion—not the daily
+apparent motion, but the real motion as seen from
+earth—was found to be so much more rapid than the
+motion of most other stars that they rightly guessed
+61 Cygni to be a rather near neighbor of ours.</p>
+
+<p>Do not misunderstand me, when I speak of a “more
+rapid motion,” and of “rather near neighborhood.”
+The real rate of 61 Cygni’s rush through space is believed
+to be about forty miles each second, or one
+thousand four hundred and fifty millions of miles
+each year. All we can perceive of this quick motion
+is that, in the course of three hundred and
+fifty years, 61 Cygni travels over a space in the sky
+about as long as the breadth of the full moon. Little
+enough, yet very far beyond what can be detected in
+the greater number of even the brightest stars.</p>
+
+<p>Then, again, as to the near neighborhood of this<span class="pagenum" id="Page_279">[Pg 279]</span>
+star, 61 Cygni is near enough to have his distance
+measured, and that is saying a good deal. Alpha
+Centauri, the nearest star of which we know in the
+southern heavens, is two hundred and seventy-five
+thousand times as far distant as the sun. But 61 Cygni,
+the nearest star of which we know in the northern
+heavens, is nearly twice as far away as Alpha Centauri.</p>
+
+<div class="figright" id="f49">
+<img src="images/fig49.jpg" alt="cygnus">
+<p class="caption">CYGNUS.</p>
+</div>
+
+<p>We call 61 Cygni a star, for so he appears to common
+observers. In reality, instead of being only one
+star, the speck of
+light which we call
+61 Cygni consists
+of <i>two stars</i>. The
+two are separated
+by a gap about half
+as wide again as
+the wide gap between
+the sun and
+Neptune. Yet so
+great is their distance
+from us that to the naked eye the two seem to be
+one. These two suns would together make a sun only
+about one-third as large as our sun. They differ in
+size, the quicker movements of one showing it to be
+the smaller; and it is by means of their known distance
+from one another, and their known rate of motion,
+that their size, or rather their weight, can be
+roughly calculated. Of course neither of the two
+shows any actual measurable disk. So much and so
+little is with tolerable certainty known about this
+particular pair of suns.</p>
+
+<p>Next let us turn to Alpha Centauri—named <i>Alpha</i>,<span class="pagenum" id="Page_280">[Pg 280]</span>
+the first letter of the Greek alphabet, because it is
+the brightest star in the constellation of the Centaur.
+The second brightest star in a constellation is generally
+called Beta, the third Gamma, the fourth Delta,
+and so on; just as if we were to name them A, B,
+C, D, in order of brightness.</p>
+
+<p>The constellation Centaur lies in the southern
+heavens, close to the beautiful constellation called the
+Southern Cross, and is invisible in the northern hemisphere.
+Of all the stars shining in the heavens
+round our earth, two only—Sirius and Canopus—show
+greater brilliancy than Alpha Centauri.</p>
+
+<p>As in the case of 61 Cygni, astronomers were led to
+attempt the measurement of Alpha Centauri’s distance,
+by noticing how much more distinct were his
+movements than the movements of other stars, though
+less rapid both to the eye and in reality than those of
+61 Cygni. Alpha Centauri’s rate of motion is some
+thirteen miles each second.</p>
+
+<p>And this, so far as we yet know, is our sun’s nearest
+neighbor in the heavens outside his own family
+circle.</p>
+
+<p>Strange to say, Alpha Centauri, like 61 Cygni, consists,
+not of a single star, but of a pair of stars. It is
+a two-sun system—whether or no surrounded by planets
+can not be told. We can only reason from what
+we see to what we do not see. And as God did not
+form our earth “in vain,” and did not form our sun
+“in vain,” so we firmly believe that he did not form
+“in vain” any one of his myriads of suns scattered
+through space. What is, has been, or will be the
+particular use of each one, it would be rash to attempt<span class="pagenum" id="Page_281">[Pg 281]</span>
+to say. But that many among them have, like
+our own sun, systems of worlds revolving round them,
+we may safely consider very probable.</p>
+
+<div class="figcenter" id="f50">
+<img src="images/fig50.jpg" alt="stars">
+<p class="caption">STARS WHOSE DISTANCES ARE BEST KNOWN. (See Table.)</p>
+</div>
+
+<p>The two suns of the Alpha Centauri double-star
+are separated by a distance about twenty-two times as
+great as the distance of the earth from the sun, yet to
+the naked eye they show as a single star. Here again
+one is much smaller than the other; and the smaller
+revolves round the larger in about eighty-five years.</p>
+
+<p>It is believed that the two together would form a<span class="pagenum" id="Page_282">[Pg 282]</span>
+sun about twice as large and heavy as our sun. This
+belief is strengthened by the great brilliancy of Alpha
+Centauri. Our own sun, placed at that distance from
+us, would shine only one-third as brightly as he does.</p>
+
+
+<p class="c">STARS WHOSE DISTANCES ARE BEST KNOWN.</p>
+
+<table>
+
+<tr>
+  <td class="tdl bl bt br bb"></td>
+  <td class="tdc bt br bb">NAME OF STAR.</td>
+  <td class="tdc bt br bb">MAG-<br>NITUDE.</td>
+  <td class="tdc bt br bb">DISTANCE<br> IN MILES.</td></tr>
+
+<tr>
+  <td class="tdr bl br">1</td>
+  <td class="tdl br">Alpha Centauri,</td>
+  <td class="tdc br">1.0</td>
+  <td class="tdl br">25 trillions.</td></tr>
+
+<tr>
+  <td class="tdr bl br">2</td>
+  <td class="tdl br">61 Cygni,</td>
+  <td class="tdc br">5.1</td>
+  <td class="tdl br">43 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">3</td>
+  <td class="tdl br">2,398, Draco,</td>
+  <td class="tdc br">8.2</td>
+  <td class="tdl br">55 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">4</td>
+  <td class="tdl br">Sirius,</td>
+  <td class="tdc br">1.0</td>
+  <td class="tdl br">58 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">5</td>
+  <td class="tdl br">9,352, Lacaille,</td>
+  <td class="tdc br">7.5</td>
+  <td class="tdl br">66 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">6</td>
+  <td class="tdl br">Procyon,</td>
+  <td class="tdc br">1.3</td>
+  <td class="tdl br">71 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">7</td>
+  <td class="tdl br">Lalande, 21,258,</td>
+  <td class="tdc br">8.5</td>
+  <td class="tdl br">74 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">8</td>
+  <td class="tdl br">Œltzen, 11,677,</td>
+  <td class="tdc br">9.0</td>
+  <td class="tdl br">74 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">9</td>
+  <td class="tdl br">Sigma Draconis,</td>
+  <td class="tdc br">4.7</td>
+  <td class="tdl br">78 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">10</td>
+  <td class="tdl br">Aldebaran,</td>
+  <td class="tdc br">1.5</td>
+  <td class="tdl br">81 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">11</td>
+  <td class="tdl br">Epsilon Indi,</td>
+  <td class="tdc br">5.2</td>
+  <td class="tdl br">87 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">12</td>
+  <td class="tdl br">Œltzen, 17,415,</td>
+  <td class="tdc br">9.0</td>
+  <td class="tdl br">94 &#160; &#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">13</td>
+  <td class="tdl br">1,516, Draco,</td>
+  <td class="tdc br">7.0</td>
+  <td class="tdl br">101&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">14</td>
+  <td class="tdl br">Omicron Eridani,</td>
+  <td class="tdc br">4.4</td>
+  <td class="tdl br">101&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">15</td>
+  <td class="tdl br">Altair,</td>
+  <td class="tdc br">1.6</td>
+  <td class="tdl br">101&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">16</td>
+  <td class="tdl br">Bradley, 3,077,</td>
+  <td class="tdc br">5.5</td>
+  <td class="tdl br">101&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">17</td>
+  <td class="tdl br">Eta Cassiopeiæ,</td>
+  <td class="tdc br">3.6</td>
+  <td class="tdl br">118&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">18</td>
+  <td class="tdl br">Vega,</td>
+  <td class="tdc br">1.0</td>
+  <td class="tdl br">128&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">19</td>
+  <td class="tdl br">Capella,</td>
+  <td class="tdc br">1.2</td>
+  <td class="tdl br">174&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">20</td>
+  <td class="tdl br">Arcturus,</td>
+  <td class="tdc br">1.0</td>
+  <td class="tdl br">204&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">21</td>
+  <td class="tdl br">Pole Star,</td>
+  <td class="tdc br">2.1</td>
+  <td class="tdl br">215&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br">22</td>
+  <td class="tdl br">Mu Cassiopeiæ,</td>
+  <td class="tdc br">5.2</td>
+  <td class="tdl br">320&#160;&#160;     ”</td></tr>
+
+<tr>
+  <td class="tdr bl br bb"> &#160;23</td>
+  <td class="tdl br bb">1,830, Groombridge,</td>
+  <td class="tdc br bb">6.5 </td>
+  <td class="tdl br bb">426&#160;&#160;     ”</td></tr>
+
+
+
+</table>
+
+<p>This table presents the most trustworthy data which
+we have yet obtained with reference to stellar distances.
+As a great number of attempts have been
+made on stars which, by their brightness or by the
+magnitude of their proper motion, would appear to be
+the nearest to us, we may believe that the star now
+considered as the nearest is really so, and that there
+is no other less distant. Thus our sun, a star in the
+immensity, is isolated in infinitude, and <i>the nearest</i><span class="pagenum" id="Page_283">[Pg 283]</span>
+sun reigns at twenty-five trillions of miles from our
+terrestrial abode. Notwithstanding its unimaginable
+velocity of 186,400 miles a second, light moves, flies,
+during four years and one hundred and twenty-eight
+days to come from this sun to us. Sound would take
+more than three millions of years to cross the same
+abyss. At the constant velocity of thirty-seven miles
+an hour, <i>an express train starting from the sun Alpha
+Centauri would not arrive here till after an uninterrupted
+course of nearly seventy-five millions of years</i>.</p>
+
+<p>Here, then, are the nearest suns to us. These stars,
+twenty-three in number, are almost the only ones
+which have shown a perceptible parallax; still the result
+is very doubtful for the last four, of which the
+parallax is less than a tenth of a second. Attempts
+have been made to ascertain the parallax of all the
+stars of the first magnitude, and the result has been
+negative for those which are not entered in this
+list. Canopus, Rigel, Betelgeuse, Achernar, Alpha of
+the Cross, Antares, Spica, and Fomalhaut, do not show
+a perceptible parallax. The fine star Alpha Cygni,
+which shines near 61 Cygni, does not present to the
+most accurate researches any trace of fluctuation: it is,
+then, incomparably more distant than its modest neighbor—at
+least five times, and perhaps twenty times,
+fifty times, one hundred times beyond that. What must
+be the colossal size and amazing light of these suns,
+of which the distance is greater than three hundred
+to four hundred trillions of miles, and which nevertheless
+still shine with so splendid a brightness!</p>
+
+<p>We did not know the distance of any stars till the
+year 1840. This shows how recent this discovery is;<span class="pagenum" id="Page_284">[Pg 284]</span>
+indeed, we have hardly now begun to form an approximate
+idea of the real distances which separate the
+stars from each other. The parallax of 61 Cygni, the
+first which was known, was determined by Bessel,
+and resulted from observations made at Königsberg
+from 1837 to 1840. Since then, the first figure obtained
+has been corrected by a series of more recent
+observations.</p>
+
+<p>Such distances are amazing and almost terrifying
+to the imagination. The mind is bewildered and almost
+overwhelmed when attempting to form a conception
+of such portions of immensity, and feels its own
+littleness, the limited nature of its powers, and its utter
+incapacity for grasping the amplitudes of creation.
+But though it were possible for us to wing our flight
+to such a distant orb as 61 Cygni, we should still find
+ourselves standing only on the verge of the starry firmament
+where ten thousands of other orbs a thousand
+times more distant would meet our view. We
+have reason to believe that a space equal to that
+which we are now considering intervenes between
+most of the stars which diversify our nocturnal sky.
+The stars appear of different magnitudes; but we
+have the strongest reason to conclude that in the majority
+of instances this is owing, not to the difference
+of their real magnitudes, but to the different distances at
+which they are placed from our globe.</p>
+
+<p>If, then, the distance of a star of the first or second
+magnitude, or those which are nearest to us, be so immensely
+great, what must be the distance of stars of
+the sixteenth or twentieth magnitude, which can be
+distinguished only by the most powerful telescopes?<span class="pagenum" id="Page_285">[Pg 285]</span>
+Some of these must be many millions of times more
+distant than the nearest star whose distance now appears
+to be determined. And what shall we think of
+the distance of those which lie beyond the reach of
+any telescope that has yet been constructed, stretching
+beyond the utmost limits of mortal vision, within
+the unexplored regions of immensity? Here even
+the most vigorous imagination drops its wing, and
+owns itself utterly unable to penetrate this mysterious
+and boundless unknown.</p>
+
+<p>Turning now from the sun, whose distance was
+first measured, and from the nearest star with which
+we are acquainted, let us think about the most radiant
+star in the heavens—Sirius, “the blazing Dog-star of
+the ancients;” named by one astronomer “the king of
+suns.”</p>
+
+<p>First, as to the color of Sirius. He belongs to the
+order of “White Suns,” and among all the white suns
+known to us, Sirius ranks as chief. There may be
+many at greater distances far surpassing him in size,
+and weight, and brilliancy; but we can only speak so
+far as we know. Strange to say, Sirius was not always
+a “white sun;” for ancient writers describe him as
+being, in their days, a <i>red</i> star. This change is very
+singular, and difficult to understand. But Sirius is
+not the only example of the kind. Many alterations
+in color have been noticed as taking place, often in a
+much shorter space of time. For instance, one star,
+which was a white sun in the days of Herschel, is now
+a golden sun.</p>
+
+<p>Secondly, as to the distance of Sirius. Like a few
+other stars, Sirius lies not quite so far away as to be<span class="pagenum" id="Page_286">[Pg 286]</span>
+beyond reach of measurement. No base-line upon
+earth would cause the slightest seeming change of
+position in him; but as our earth journeys round the
+sun, the line from one side of her orbit to the other is
+found wide enough. A base-line of one hundred and
+eighty-six millions of miles does cause just a tiny
+seeming change.</p>
+
+<p>It is very little even with Alpha Centauri, and with
+Sirius it is much less. The “displacement” of Sirius
+is so slight that to measure his distance with exactness
+is impossible. Sirius lies more than twice as
+far away from earth as Alpha Centauri. To reach
+Sirius, the straight line between earth and sun must
+be repeated six hundred and twenty-six thousand
+times. Light, which reaches us from the sun in eight
+minutes and a half, and from Alpha Centauri in four
+years and a third, can not reach us from Sirius in
+less than nine years.</p>
+
+<p>Thirdly, as to the size of Sirius. Here, of course,
+we are in difficulties. Radiantly as Sirius shines on a
+clear night, and dazzling as he looks through a powerful
+telescope, he shows no real disk or round surface,
+but only appears as one point of brilliant light. Some
+believe him to be much the same size as our sun, while
+others believe him to be very much larger. But we
+have no certain ground to rest upon. The only safe
+method of calculating the probable size—or, rather,
+weight—of a star is through the discovery of a companion,
+and a knowledge of its distance from the chief
+star, and its time of revolution round the chief star.</p>
+
+<p>Fourthly, as to the motions of Sirius—not his
+nightly apparent movement, caused by the earth’s<span class="pagenum" id="Page_287">[Pg 287]</span>
+turning on her axis, but his real journey through
+space. For a long while it was only possible to observe
+the movements of a star when the star was traveling
+<i>sideways</i> to us across the sky. A star coming
+straight towards us, or going straight away from us,
+would seem to be at rest. Lately, however, by means
+of that remarkable instrument, the spectroscope, it
+has been found possible to measure the motions of
+stars coming towards or going away from us. This
+is possible as yet only in a few scattered cases, but
+among those few is the brilliant Sirius.</p>
+
+<p>The sideways motion of Sirius had been known
+before. It now appears that he does not move exactly
+sideways to us, but is rushing away in a slanting direction
+at the rate of thirty miles each second, or about
+one thousand millions of miles a year.</p>
+
+<p>How many millions upon millions of miles Sirius
+must now be farther from us than in the days of the
+ancients! Yet he shines still, the most brilliant star
+in the sky. So small a matter are all those millions
+of miles, compared with the whole of his vast distance
+from us, that we do not perceive any lessening
+of light.</p>
+
+<p>It is an interesting fact that while Sirius is moving
+away from us, we are also moving away from him.
+Our “first station ahead,” in the constellation Hercules,
+lies exactly in the opposite direction from Sirius.
+But the sun does not move so fast as Sirius. He is
+believed to accomplish only about one hundred and
+fifty millions of miles each year, drawing all his planets
+with him.</p>
+
+<p>Fifthly, has Sirius a family, or system, like that of<span class="pagenum" id="Page_288">[Pg 288]</span>
+our sun? Why not? Common sense and reason alike
+answer with a “Probably, yes”—not only about Sirius,
+but about other stars also. No doubt the systems—the
+number, size, weight, speed, distance, and kind of
+planets—differ very greatly. No doubt there are
+boundless varieties of beauty and grandeur.</p>
+
+<p>But that our sun should be the head of so wonderful
+and complex a system, that his rays should be the
+source of life and heat to so many dependents, and
+that all the myriads of suns besides should be mere
+solitary lamps shining into empty space, warming,
+lighting, controlling <i>nothing</i>, is an idea scarcely to be
+looked in the face.</p>
+
+<p>Of course, there may be other and different uses
+for some of these suns, beyond our understanding.
+We must not be positive in the matter. It seems,
+however, pretty certain that Sirius at least is not a
+solitary, unattended sun.</p>
+
+<p>Astronomers, carefully watching his movements,
+were somewhat perplexed. As with Uranus, the attraction
+of a heavy body beyond was suspected from
+the nature of the planet’s motions, so it happened
+again with the far more distant Sirius. Astronomers
+could only explain his movements by supposing the
+attraction of some large and near satellite. No one
+knew anything about such a satellite, but it was felt
+that one must exist.</p>
+
+<p>Nearly twenty years had elapsed after Bessel had
+predicted the disturber of Sirius before the telescopic
+discovery which confirmed it was made. The circumstances
+under which that discovery was made are not,
+indeed, so dramatic as those which attended the discovery<span class="pagenum" id="Page_289">[Pg 289]</span>
+of Neptune, but yet they have an interest of
+their own. In February, 1862, Alvan Clark &amp; Sons,
+the celebrated telescope-makers, of Cambridge, Massachusetts,
+were completing a superb eighteen-inch object-glass
+for the Chicago Observatory. Turning the
+instrument on Sirius, for the purpose of trying it, the
+practiced eye of Alvan Graham Clark, the son, soon
+detected something unusual, and he exclaimed, “Why,
+father, the star has a companion!” The father looked,
+and there was a faint companion due east from the
+bright star, and distant about ten seconds of a degree.
+This was exactly the predicted direction of the companion
+of Sirius, and yet the observers knew nothing
+of the prediction. As the news of this discovery
+spread, many great telescopes were pointed on Sirius;
+and it was found that when observers knew exactly
+where to look for the object, many instruments would
+show it. The new companion star to Sirius lay in the
+true direction, and it was now watched with the keenest
+interest, to see whether it also was moving in the
+way it should move,—if it were really the body whose
+existence had been foretold. Four years of observation
+showed that this was the case, so that hardly any
+doubt could remain that the telescopic discovery had
+been made of the star which had caused the inequality
+in the motion of Sirius.</p>
+
+<p>It is certainly a very remarkable fact that, out of
+the thousands of stars with which the heavens are
+adorned, no single star has yet been found which certainly
+shows an appreciable disk in the telescope. We
+are aware that some skillful observers have thought
+that certain small stars do show disks; but we may<span class="pagenum" id="Page_290">[Pg 290]</span>
+lay this aside, and appeal only to the ordinary fact
+that our best telescopes turned on the brightest stars
+show merely glittering points of light, so hopelessly
+small as to elude our most delicate micrometers. The
+ideal astronomical telescope is, indeed, one which will
+show Sirius, or any other bright star, as nearly identical
+as possible with Euclid’s definition of a point,
+being that which has no parts and no magnitude.</p>
+
+<p>Lastly, what is Sirius made of? The late discovery
+of spectrum analysis, or of the instrument called the
+spectroscope, helps us here. A little further explanation
+on this subject will be given later. It may be
+observed in passing that before the said discovery,
+astronomers can scarcely be asserted to have known
+with any certainty that stars were suns. They could,
+indeed, be sure that at the vast distances of the fixed
+stars no bodies, shining by merely reflected light,
+could possibly be visible to us. But there knowledge
+stopped.</p>
+
+<p>Now we can say more. Now the spectroscope, by
+breaking up and dividing for us the slender ray of
+light traveling from each star, has shown to us something
+of the nature of the stars. Now we know that
+the stars, like our sun, are burning bodies, surrounded
+by atmospheres full of burning gas.</p>
+
+<p>It has even been found out that in Sirius there are
+large quantities of sodium and magnesium, besides
+other metals, and an abundant supply of hydrogen gas.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_291">[Pg 291]</span></p>
+
+<h2 class="nobreak" id="c24">CHAPTER XXIV.</h2>
+</div>
+
+<p class="c sp">DIFFERENT KINDS OF SUNS.</p>
+
+
+<p><span class="smcap large">Various</span> in kind, various in size, various in color,
+various in position, various in motion, are the myriad
+suns scattered through space. So far are they from
+being formed on the same plan, turned out on the
+same model, that it may with reason be doubted
+whether any two stars could be found exactly alike.
+Why should we expect to find them so? No two oak-leaves,
+no two elm-leaves, precisely alike, are to be
+found upon earth.</p>
+
+<p>So some stars are large, some are small. Some are
+rapid in movement, some are slow. Some are yellow,
+some white, some red, green, blue, purple, or gray.
+Some are single stars; others are arranged in pairs,
+trios, quartets, or groups. Some appear only for a
+time, and then disappear altogether. Others are
+changeful, with a light that regularly waxes and
+wanes in brightness.</p>
+
+<p>We have now to give a little time and thought to
+variable stars and temporary stars; afterwards to
+double stars and colored stars. There are many stars
+which pass through gradual and steady changes—first
+brightening, then lessening in light, then brightening
+again. One such star is to be seen in the constellation
+of the Whale. It is named “Mira,” or “The
+Marvelous,” and the time in which its changes take
+place extends to eleven months. For about one fortnight<span class="pagenum" id="Page_292">[Pg 292]</span>
+it is a star of the second magnitude. Through
+three months it grows slowly more and more dim, till
+it becomes invisible, not only to the naked eye, but
+through ordinary telescopes. About five months it
+remains thus. Then again, during three months, it
+grows brighter and brighter, till it is once more a
+second-magnitude star, and after a fortnight’s pause
+begins anew to fade.</p>
+
+<p>At its maximum, this star is yellow; when it is
+faint, it is reddish. Spectrum analysis shows in it a
+striped spectrum of the third type, and when its light
+diminishes it preserves all the principal bright rays
+reduced to very fine threads. The most plausible explanation
+of this variability is to suppose that it periodically
+emits vapors similar to the eruptions observed
+in the solar photosphere. Instead of its
+periodicity being like that of the sun—eleven years
+and hardly perceptible—this variation of the sun of
+the Whale is three hundred and thirty-one days and
+very considerable. It is subject to oscillations and irregularities
+similar to those which we remark in our
+sun. Of all the variable stars, this is the easiest to
+observe, and it has been known for nearly three hundred
+years.</p>
+
+<p>The most celebrated of all the variable stars is
+that known as Algol, in the constellation of Perseus.
+This star is very conveniently placed for observation,
+being visible every night in the Northern Hemisphere,
+and its wondrous and regular changes can be observed
+without any telescopic aid. Every one who desires to
+become acquainted with the great truths of astronomy
+should be able to recognize this star, and should have<span class="pagenum" id="Page_293">[Pg 293]</span>
+also followed it during one of its periods of change.
+Algol is usually a star of the second magnitude; but
+in a period between two or three days—or, more accurately,
+in an interval of two days, twenty hours,
+forty-eight minutes, and fifty-five seconds—its brilliancy
+goes through a most remarkable cycle of variations.
+The series commences with a gradual decline
+of the star’s brightness, which, in the course of three
+or four hours, falls from the second magnitude down
+to the fourth. At this lowest stage of brightness, Algol
+remains for about twenty minutes, and then begins
+to increase, until in three or four hours it regains the
+second magnitude, at which it continues for about two
+days, thirteen hours, when the same series commences
+anew. It seems that the period required by Algol to
+go through its changes is itself subject to a slow, but
+certain variation.</p>
+
+<p>Another variable star, Betelgeuse in Orion, undergoes
+its variations in about two hundred days; while
+yet another, Delta Cephei, takes only six days. Our
+own sun is believed to be in some slight degree a
+variable star, passing through his changes in eleven
+years. When the sun-spots are most numerous, he
+would probably appear, if seen from a great distance,
+more dim than when there are few or none of them.</p>
+
+<p>Sometimes a star is not merely variable. Stars have
+appeared for a brief space, and then utterly vanished.
+They are then named Temporary Stars. Whether
+such a star really does go out of existence, or whether
+it merely becomes too dim to be seen; whether the
+furnace-fires are extinguished, and the glowing sun
+changes into a dark body, or whether it merely turns<span class="pagenum" id="Page_294">[Pg 294]</span>
+a dark side towards us for a very long period,—these
+are questions we can not answer.</p>
+
+<p>An extraordinary specimen of a temporary star was
+seen in 1572. It was not a comet, for it had no coma
+or tail, and it never moved from its place. The brightness
+of the star was so great as to surpass Sirius and
+Jupiter, and to equal Venus at her greatest brilliancy.
+Nay, it must have surpassed even Venus, for it was
+plainly visible at midday in a clear sky. Gradually
+the light faded and grew more dim, till at length it
+entirely disappeared. As it lessened in brilliancy, it
+also changed in color, passing from white to yellow,
+and from yellow to red. This curiously agrees with
+the three tints of the first, second, and fourth orders
+of suns, as lately classified.</p>
+
+<p>This star was observed by Tycho Brahe, who gives
+the following curious account:</p>
+
+<p>“One evening, when I was contemplating, as usual,
+the celestial vault, whose aspect was so familiar to me,
+I saw, with inexpressible astonishment, near the zenith,
+in Cassiopeia, a radiant star of extraordinary magnitude.
+Struck with surprise, I could hardly believe my
+eyes. To convince myself that it was not an illusion,
+and to obtain the testimony of other persons, I called
+out the workmen employed in my laboratory, and
+asked them, as well as all passers-by, if they could
+see, as I did, the star, which had appeared all at once.
+I learned later on that in Germany carriers and other
+people had anticipated the astronomers in regard to a
+great apparition in the sky, which gave occasion to
+renew the usual railleries against men of science (as
+with comets whose coming had not been predicted).</p>
+
+<p><span class="pagenum" id="Page_295">[Pg 295]</span></p>
+
+<p>“The new star was destitute of a tail; no nebulosity
+surrounded it; it resembled in every way other stars
+of the first magnitude. Its brightness exceeded that
+of Sirius, of Lyra, and of Jupiter. It could only be
+compared with that of Venus when it is at its nearest
+possible to the earth. Persons gifted with good sight
+could distinguish this star in daylight, even at noonday,
+when the sky was clear. At night, with a cloudy
+sky, when other stars were veiled, the new star often
+remained visible through tolerably thick clouds. The
+distance of this star from the other stars of Cassiopeia,
+which I measured the following year with the
+greatest care, has convinced me of its complete immobility.
+From the month of December, 1572, its
+brightness began to diminish; it was then equal to
+Jupiter. In January, 1573, it became less brilliant
+than Jupiter; in February and March, equal to stars
+of the first order; in April and May, of the brightness
+of stars of the second order. The passage from the
+fifth to the sixth magnitude took place between December,
+1573, and February, 1574. The following
+month the new star disappeared without leaving a
+trace visible to the naked eye, having shone for seventeen
+months.”</p>
+
+<p>These circumstantial details permit us to imagine
+the influence which such a phenomenon must have exercised
+on the minds of men. Few historical events
+have caused so much excitement as this mysterious
+envoy of the sky. It first appeared on November 11,
+1572. General uneasiness, popular superstition, the
+fear of comets, the dread of the end of the world, long
+since announced by the astrologers, were an excellent<span class="pagenum" id="Page_296">[Pg 296]</span>
+setting for such an apparition. It was soon announced
+that the new star was the same which had led the wise
+men to Bethlehem, and that its arrival foretold the return
+of the Messiah and the last judgment. For the
+hundredth time, perhaps, this sort of prognostication
+was recognized as absurd. It did not, however, prevent
+the astrologers from being believed, twelve years
+later, when they announced anew the end of the
+world for the year 1588; these predictions exercised
+the same influence on the public mind.</p>
+
+<p>After the star of 1572 the most celebrated is that
+which appeared in October, 1604, in Serpentarius, and
+which was observed by two illustrious astronomers,
+Kepler and Galileo. As happened with the preceding,
+its light imperceptibly faded. It remained visible for
+fifteen months, and disappeared without leaving any
+traces. In 1670 another temporary star, blazing out
+in the head of the Fox (Vulpecula), showed the singular
+phenomenon of being extinguished and reviving
+several times before it completely vanished. We know
+of <i>twenty-four</i> stars which, during the last two thousand
+years, have presented a sudden increase of light;
+have been visible to the naked eye, often brilliant; and
+have then again become invisible. The last apparitions
+of this kind happened before our eyes in 1866,
+1876, 1885, and 1892, and spectrum analysis enabled
+us to ascertain, as we have seen, that they were due to
+veritable combustion—a fire caused by a tremendous
+expansion of incandescent hydrogen, and to phenomena
+analogous to those which take place in the solar
+photosphere. A rather curious fact about these stars
+is, that they do not blaze out indifferently in any point<span class="pagenum" id="Page_297">[Pg 297]</span>
+of the sky, but in rather restricted regions, chiefly in
+the neighborhood of the Milky Way.</p>
+
+<p>Many other instances have been known, beside
+those referred to, of variable and temporary stars.</p>
+
+<p>There are two distinct kinds of double-stars. First,
+we have those which merely seem to be double, because
+one lies almost directly behind the other, though
+widely distant from it.
+Just as a church-tower,
+two miles off, may appear
+to stand close side
+by side with another
+church-tower two and
+a half miles off, though
+they are in fact separated.
+Secondly, we
+have the real systems
+of two suns belonging
+to one another; the
+smaller moving round
+the larger, or more correctly
+both traveling
+round one central point called the center of gravity,
+the smaller having the quicker rate of motion.</p>
+
+<div class="figright" id="f51">
+<img src="images/fig51.jpg" alt="lyra">
+<p class="caption">LYRA</p>
+</div>
+
+<p>Alpha Centauri and 61 Cygni have been already described,
+as examples of true double-stars. In the
+constellation Lyra a marked instance is to be seen.
+The brightest star in the Lyre is Vega, and near Vega
+shines a tiny star, which to people with particularly
+clear sight has sometimes rather a longish look. If
+you examine this star through an opera-glass, you find
+it to consist of two separate stars. But if you get a<span class="pagenum" id="Page_298">[Pg 298]</span>
+more powerful telescope, and look again, you will find
+that <i>each star</i> of the couple actually consists of <i>two</i>
+stars. The four are not at equal distances. Two points
+of light seemingly close together are parted by a wide
+gap from two other points equally close together.
+These four stars are believed to have a double motion.
+Each of the separate pairs revolves by itself, the two
+suns traveling round one center; and in addition to
+this the two <i>couples</i> of suns probably perform a long
+journey round another center common to them all.</p>
+
+<p>Many thousands of double stars have been discovered;
+and a large number of these are now known to
+be, not merely two distinct suns lying in the same line
+of sight, but two brother-suns, each probably the center
+of his own system of planets.</p>
+
+<p>We have not only to consider the number of suns,
+though of simple numbers more yet remains to be said.
+Attention must also be given to the varying colors of
+different stars; for all suns in the universe are not
+made after the model of our sun. All suns are not
+yellow.</p>
+
+<p>So far as single stars are concerned, colors seem
+rather limited. White stars, golden or orange stars,
+ruby-red stars, placed alone, are often seen; but blue
+stars, green stars, gray stars, silver stars, purple stars,
+are seldom if ever visible to the naked eye, or known
+to exist as single stars.</p>
+
+<p>Take a powerful telescope and examine star-couples,
+and a very different result you will find.
+Not white, yellow, and red alone, but blue, purple,
+gray, green, fawn, buff, silvery white, and coppery
+hues, will delight you in turn. As a rule, when the<span class="pagenum" id="Page_299">[Pg 299]</span>
+two stars of a couple are alike in color, they are
+either white, or yellow, or red. Also in the case of
+double-stars of different colors, the larger of the two
+is almost invariably white or some shade of yellow
+or red.</p>
+
+<p>There are, however, exceptions to all such rules.
+Blue stars are almost never seen alone, and as one of
+a pair the blue star is generally, if not invariably, the
+smaller. But instances are known of double-stars,
+both of which are blue; and one group in the southern
+heavens is entirely made up of a multitude of
+bluish suns.</p>
+
+<p>It is when we come to consider double-stars of two
+colors that the most striking effects are found. Now
+and then the two suns are nearly the same in size; but
+more commonly one is a good deal larger than the other.
+This is known by the brighter light of the largest, and
+the more rapid movements of the smallest. The lesser
+star is often only small by comparison, and may be
+in reality a very goodly and brilliant sun.</p>
+
+<p>Among nearly six hundred “doubles” examined by
+one astronomer, there were three hundred and seventy-five
+in which the two stars were of one color,
+generally white, yellow, orange, or red. The rest were
+different in tint, the difference between the two suns
+in about one hundred and twenty cases being very
+marked.</p>
+
+<p>For instance, a red “primary,” as the larger star is
+called, will be seen with a small green satellite; or a
+white primary will have a little brother-sun of purple,
+or of dark ruby, or of light red. Sometimes the larger
+sun is orange, the companion being purple or dark<span class="pagenum" id="Page_300">[Pg 300]</span>
+blue. Again, the chief star will be red with a blue
+satellite, or yellow with a green satellite, or orange
+with an emerald satellite, or golden with a reddish-green
+satellite. We hear of golden and lilac couples,
+of cream and violet pairs, of white and green companions.
+But, indeed, the variety is almost endless.</p>
+
+<div class="figcenter" id="f52">
+<img src="images/fig52.jpg" alt="northern">
+<p class="caption">CONSTELLATIONS IN THE NORTHERN HEMISPHERE.</p>
+</div>
+
+<p>There may be worlds circling around these suns—worlds,
+perhaps, with living creatures on them.
+We know little about how such systems of suns and
+worlds may be arranged. Probably each sun would<span class="pagenum" id="Page_301">[Pg 301]</span>
+have his own set of planets, and both suns with their
+planets would travel round one central point. Perhaps,
+where the second sun is much the smallest, it
+might occasionally be like a big blazing satellite among
+the planets—a kind of burning Jupiter-sun to the chief
+sun.</p>
+
+<p>Among colored stars, single and double, a few may
+be mentioned by name as examples. Sirius, as already
+observed, is a brilliant white sun; and brilliant
+white also are Vega, Altair, Regulus, Spica, and many
+others. Capella, Procyon, the Pole-star, and our own sun,
+are examples of yellow stars. Aldebaran, Betelgeuse,
+and Pollux, are ruby-red. Antares is a red star, with
+a greenish “scintillation” or change of hue in its
+twinkling. A tiny green sun belonging to this great
+and brilliant red sun has been discovered. Some have
+called Antares “the Sirius of Red Suns.”</p>
+
+<p>It is during the fine nights of winter that the constellation
+Taurus, or The Bull, with the star Aldebaran
+marking its eye, shines in the evening above our
+heads. No other season is so magnificently constellated
+as the months of winter. While nature deprives
+us of certain enjoyments in one way, it offers us in
+exchange others no less precious. The marvels of the
+heavens present themselves from Taurus and Orion
+in the east to Virgo and Boötes on the west. Of eighteen
+stars of the first magnitude, which are counted in
+the whole extent of the firmament, a dozen are visible
+from nine o’clock to midnight, not to mention
+some fine stars of the second magnitude, remarkable
+nebulæ, and celestial objects well worthy of the attention
+of mortals. It is thus that nature establishes an<span class="pagenum" id="Page_302">[Pg 302]</span>
+harmonious compensation, and while it darkens our
+short and frosty days of winter, it gives us long nights
+enriched with the most opulent creations of the sky.
+The constellation of Orion is not only the richest in
+brilliant stars, but it conceals for the initiated treasures
+which no other is known to afford. We might
+almost call it the California of the sky.</p>
+
+<p>To the southeast of Orion, on the line of the
+Three Kings, shines the most magnificent of all the
+stars, <i>Sirius</i>, or <i>Alpha</i> of the constellation of the Great
+Dog. This constellation rises in the evening at the
+end of November, passes the meridian at midnight
+at the end of January, and sets at the end of March.
+It played the greatest part in Egyptian astronomy, for
+it regulated the ancient calendar. It was the famous
+Dog Star; it predicted the inundation of the Nile, the
+summer solstice, great heats and fevers; but the precession
+of the equinoxes has in three thousand years
+moved back the time of its appearance by a month and
+a half; and now this fine star announces nothing,
+either to the Egyptians who are dead or to their successors.
+But we shall see farther on what it teaches
+us of the grandeur of the sidereal universe.</p>
+
+<p>The <i>Little Dog</i>, or Procyon, is found above the
+Great Dog and below the Twins (Castor and Pollux),
+to the east of Orion. With the exception of Alpha
+Procyon, no brilliant star distinguishes it.</p>
+
+<p>The two double-stars, 61 Cygni and Alpha Centauri,
+are formed each of two orange suns.</p>
+
+<p>In the Southern Cross there is a wonderful group
+of stars, consisting of about one hundred and ten
+suns, nearly all invisible to the naked eye. Among the<span class="pagenum" id="Page_303">[Pg 303]</span>
+principal stars of this group, which Sir John Herschel
+described as being, when viewed through a powerful
+telescope, like “a casket of variously-colored precious
+stones,” are two red stars, two bright green, three pale
+green, and one of a greenish blue.</p>
+
+<p>The splendor of these natural illuminations can
+hardly be conceived by our terrestrial imagination.
+The tints which we admire in these stars from here
+can give but a distant idea of the real value of their
+colors. Already, in passing from our foggy latitudes
+to the limpid regions of the tropics, the colors of the
+stars are accentuated, and the sky becomes a veritable
+casket of brilliant gems. What would it be if we
+could transport ourselves beyond the limits of our
+atmosphere? Seen from the moon, these colors would
+be splendid. Antares, Alpha Herculis, Pollux, Aldebaran,
+Betelgeuse, Mars, shine like rubies; the Polar
+Star, Capella, Castor, Arcturus, Procyon, are veritable
+celestial topazes; while Sirius, Vega, and Altair are
+diamonds, eclipsing all by their dazzling whiteness.
+How would it be if we could approach the stars so as
+to perceive their luminous disks, instead of merely
+seeing brilliant points destitute of all diameter?</p>
+
+<p>Blue days, violet days, dazzling red days, livid green
+days! Could the imagination of poets, could the caprice
+of painters, picture on the palette of fancy a
+world of light more astounding than this? Could the
+mad hand of the chimera, throwing on the receptive
+canvas the strange lights of its fancy, erect by chance
+a more astonishing edifice?</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_304">[Pg 304]</span></p>
+
+<h2 class="nobreak" id="c25">CHAPTER XXV.</h2>
+</div>
+
+<p class="c sp">GROUPS AND CLUSTERS OF SUNS.</p>
+
+
+<p><span class="smcap large">We</span> have been thinking a good deal about single
+stars and double stars, as seen from earth. Now we
+have to turn our attention to groups, clusters, <i>masses</i>
+of stars, in the far regions of space.</p>
+
+<p>Have you ever noticed on a winter night, when
+the sky was clear and dotted with twinkling stars, a
+band of faintly-glimmering light stretching across the
+heavens from one horizon to the other? The band is
+irregular in shape, sometimes broader, sometimes narrower;
+here more bright, there more dim. If you
+were in the Southern Hemisphere you would see the
+same soft belt of light passing all across the southern
+heavens. This band or belt is called the Milky Way.</p>
+
+<p>But what is the Milky Way? It is made up of
+stars. So much we know. As the astronomer turns
+his telescope to the zone of faintly-gleaming light, he
+finds stars appearing behind stars in countless multitudes;
+and the stronger his telescope, the more the
+white light changes into distant stars.</p>
+
+<p>Our sun we believe to be one of the stars of the
+Milky Way; merely one star among millions of stars;
+merely one golden grain among the millions of sparkling
+gold-dust grains scattered lavishly through creation.
+Scattered, not recklessly, not by chance, but
+placed, arranged, and guided each by its Maker’s upholding
+hand.</p>
+
+<p><span class="pagenum" id="Page_305">[Pg 305]</span></p>
+
+<p>The Milky Way, or the Galaxy, as it has been
+called, has great interest for astronomers. Many have
+been the attempts made to discover its actual size, its
+real shape, how many stars it contains, how far it extends;
+but to all such questions the only safe answers
+to be returned are fenced around with “perhaps” and
+“may be.” There are many very remarkable clusters of
+stars to be seen in the heavens—some few visible as
+faint spots of light to the naked eye, though the greater
+number are only to be seen through a telescope.
+Either with the naked eye, or in telescopes of varying
+power, they show first as mere glimmers of light,
+which, viewed with a more powerful telescope, separate
+into clusters of distant stars.</p>
+
+<div class="figcenter" id="f53">
+<img src="images/fig53.jpg" alt="cluster">
+<p class="caption">A CLUSTER OF STARS IN CENTAURUS.</p>
+</div>
+
+<p>The most common shape of these clusters is globular—to
+the eye appearing simply round. Stars gather<span class="pagenum" id="Page_306">[Pg 306]</span>
+densely near the center, and gradually open out to
+a thin scattering about the edge. Thousands of suns
+are often thus collected into one cluster.</p>
+
+<p>The clusters are to be seen in all parts of the sky;
+but the greater number seem to be gathered into the
+space covered by the Milky Way and by the famous
+south Magellanic Clouds.</p>
+
+<p>Some of them are beautifully colored; as, for instance,
+a cluster in Toucan, not visible from England,
+the center of which is rose-colored, bordered with
+white. No doubt it contains a large number of
+bright red suns, surrounded by a scattering of white
+suns.</p>
+
+<p>It used to be supposed that many of these clusters
+were other vast gatherings or galaxies of stars, like
+the Milky Way, lying at enormous distances from us.
+This now seems unlikely. The present idea rather is,
+that each cluster, in place of being another “Milky
+Way” of millions of widely-scattered suns, is one
+great <i>star-system</i>, consisting indeed of thousands of
+suns, but all moving round one center. Probably
+most of these clusters are themselves a part of the
+collection of stars to which our sun belongs.</p>
+
+<p>If this be so, and if worlds are traveling among
+the suns—as may well be, since they are doubtless
+quite far enough apart for each sun to have his own
+little or great system of planets—what sights must be
+seen by the inhabitants of such planets!</p>
+
+<p>We do not indeed know the distance between the
+separate suns of a cluster, which may be far greater
+than appears to us. But if astronomers calculate
+rightly, they are near enough together to shed bright<span class="pagenum" id="Page_307">[Pg 307]</span>
+light on all sides of a planet revolving in their midst.
+The said planet might perhaps not have within view
+a single sun equal in apparent size to our sun as seen
+from earth; yet thousands of lesser suns, shining
+brightly in the firmament night and day, would cause
+a radiance which we never enjoy.</p>
+
+<p>No, not <i>night</i>. In such a world there could be no
+night. Worlds in the midst of a star-cluster must be
+regions of perpetual day. No night, no starry heaven,
+no sunrise lights or sunset glories, no shadow mingling
+with sunshine, but one continual, ceaseless blaze of
+brightness. We can hardly picture, even in imagination,
+such a condition of things.</p>
+
+<div class="figcenter" id="f54">
+<img src="images/fig54.jpg" alt="nebula">
+<p class="caption">THE GREAT NEBULA IN ANDROMEDA, COMPARED WITH<br>
+SIZE OF THE SOLAR SYSTEM.</p>
+</div>
+
+<p>Besides star-clusters there are also nebulæ. The
+word <i>nebula</i> comes from the Latin word for “cloud,”
+and the nebulæ are so named from their cloudlike
+appearance.</p>
+
+<p>It is not easy to draw a line of clear division between<span class="pagenum" id="Page_308">[Pg 308]</span>
+nebulæ and distant star-clusters; for both have
+at first sight the same dim, white, cloudy look. In
+past days the star-clusters were included by astronomers
+under the general class of nebulæ. And as with
+the star-clusters, so with many of the nebulæ, the
+more powerful telescopes of modern days have shown
+them to be great clusters, or systems, or galaxies of
+stars, at vast distances from us.</p>
+
+<p>It was supposed with the nebulæ, as with some of
+the star-clusters, that they were other “Milky Ways”
+of countless stars, far beyond the outside boundaries
+of our Milky Way. This may still be true of some or
+many nebulæ, but certainly not of all.</p>
+
+<p>For there are different kinds of nebulæ. Some
+may, as just said, be vast gatherings of stars lying at
+distances beyond calculation, almost beyond imagination.
+Others appear rather to be clusters of stars,
+like those already described, probably situated in our
+own galaxy of stars. There is also a third kind of
+nebula. Many nebulæ, once supposed to be clusters
+of stars, having been lately examined by means of the
+spectroscope, are found to be enormous masses of
+glowing gas, and not solid bodies at all.</p>
+
+<p>The number of nebulæ known amounts to many
+thousands. They are commonly divided into classes,
+according to their seeming shape. There are nebulæ
+of regular form, and nebulæ of irregular form. There
+are circular nebulæ, oval nebulæ, annular nebulæ,
+conical nebulæ, cometary nebulæ, spiral nebulæ, and
+nebulæ of every imaginable description. These
+shapes would no doubt entirely change, if we could
+see them nearer; and indeed, even in more powerful<span class="pagenum" id="Page_309">[Pg 309]</span>
+telescopes, they are often found to look quite different.
+While on the subject of clusters and nebulæ, mention
+should be made of the famous Magellanic Clouds
+in the southern heavens. Sometimes they are called
+the Cape Clouds. They differ from other nebulæ in
+many points, and more particularly in their apparent
+size. The Great Cloud is about two hundred times
+the size of the full moon, while the Small Cloud is
+about one-quarter as large. In appearance they are
+not unlike two patches of the Milky Way, separated
+and moved to a distance from the main stream.</p>
+
+<p>These clouds are surrounded by a very barren portion
+of the heavens, containing few stars; but in
+themselves they are peculiarly rich. Seen through a
+powerful telescope, they are found to abound with
+stars. The Greater Cloud alone contains over six
+hundred from the seventh to the tenth magnitudes,
+countless tiny star-points of lesser magnitudes, star-clusters
+of all descriptions, and nearly three hundred
+nebulæ,—all crowded into this seemingly limited
+space.</p>
+
+<p>Among many famous nebulæ, the one in Orion and
+the one in Andromeda may be particularly mentioned.
+The size of the latter, as compared with the size of
+our Solar System, is shown in the cut of this nebula.
+On the hypothesis of a complete resolvability into stars,
+the mind is lost in numbering the myriads of suns, the
+agglomerated individual lights of which produce these
+nebulous fringes of such different intensities. What
+must be the extent of this universe, of which each sun
+is no more than a grain of luminous dust!</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_310">[Pg 310]</span></p>
+
+<h2 class="nobreak" id="c26">CHAPTER XXVI.</h2>
+</div>
+
+<p class="c sp">THE PROBLEM OF SUN AND STAR DISTANCES.</p>
+
+
+<p><span class="smcap large">One</span> question had long occupied the minds of scientific
+men without the finding of any satisfactory
+answer, and this was the distance of the sun from
+our earth.</p>
+
+<p>At length the sun had fully gained his rightful position
+in the minds of men as center and controller of
+the Solar System, and earth was fully dethroned from
+her old false position. In point of fact, the sun had
+gained <i>more</i> than his rightful position; since he was
+now looked upon very much as the earth had been
+formerly looked upon; since he was regarded practically
+as the motionless Universe-Center. The earth
+might and did move—people had grown used to that
+idea—but the sun, at all events, was fixed. The sun,
+beyond turning upon his axis, was motionless.</p>
+
+<p>Still, as to the true distance of the sun from ourselves,
+ignorance reigned. Tycho Brahe had made a great
+advance on earlier notions by placing the light-giver
+4,000,000 miles away in imagination. Kepler, a
+quarter of a century later, increased this to 14,000,000.
+Galileo afterwards reverted to the 4,000,000.
+All this, however, was sheer guesswork.</p>
+
+<p>Not till well on in the seventeenth century did Cassini
+make a definite attempt at actual measurement of
+the sun’s distance, and this attempt gave as a result
+some 82,000,000 miles—not far removed from the<span class="pagenum" id="Page_311">[Pg 311]</span>
+truth. But at the same period other observers gave
+results of 41,000,000 and 136,000,000; so for years
+the question still remained swathed in mist. Better
+modes and better instruments were required before it
+could receive settlement.</p>
+
+<p>The measurement of the distance of objects a good
+way off is by means of their “parallax,” or the apparent
+change in their position when viewed from two
+different points at some distance from each other.
+To this method of calculating distance we have already
+referred.</p>
+
+<p>This kind of measurement of distances is not confined
+to our earth’s surface alone. The distances of
+bright bodies in the heavens may be calculated after
+just the same method, provided only that the heavenly
+body is not too far distant to be made to change its
+seeming position in the sky.</p>
+
+<p>Suppose you wished to find out how far off the
+moon is. You would have to make your observation
+of the moon’s exact position in the sky—of just that
+spot precisely where she is to be seen among heavenly
+scenery at a particular moment; and you would have
+to get somebody else to make a similar observation, at
+the same time, from some other part of earth, at a
+good distance from your post.</p>
+
+<p>There are no hills or woods in the sky for the moon
+to be seen against; but there are plenty of stars, bright
+points of light far beyond the moon. If you look at
+her from one place, and your friend looks at her from
+another place a good way off, there will be a difference
+in your two “views.” You will see her very
+close to certain stars; and your friend will see her not<span class="pagenum" id="Page_312">[Pg 312]</span>
+quite so close to those stars, but closer to others. This
+difference of view would give the moon’s parallax.</p>
+
+<p>If your observation were very careful, very exact,
+and if you had the precise distance between the spot
+where you stood, and the spot where your friend stood,—then,
+from that base-line, and from the two angles
+formed by its junction with the lines from the two
+ends of it straight to the moon, you might reckon
+how many miles away the moon is. The greater the
+distance between the two places of observation, the
+better,—as, for instance, at Greenwich and the Cape
+of Good Hope.</p>
+
+<p>Practically, this is not nearly so simple a matter as
+it may sound, because our earth is always on the move,
+and the moon herself is perpetually journeying onward.
+All such motions have to be most scrupulously allowed
+for. So the actual measurement of moon-distance requires
+a great deal of knowledge and of study. Many
+other difficulties and complications besides these enter
+into the question, and have to be overcome.</p>
+
+<p>Now, the sun is very much farther away than the
+moon, and the stumbling-blocks in the way of finding
+out his distance become proportionately greater
+and more numerous. To observe him from two parts
+of England, or from two parts of Europe, would give
+him no parallax. That is to say, there would be no
+change of position on his part apparent to us.</p>
+
+<p>I do not say that there would be no change at all;
+but only that it would be so minute as to be quite unseen
+by human eyes, even with the help of most careful
+and accurate measurement. A very long base-line
+is needed to make the sun distinctly appear to change<span class="pagenum" id="Page_313">[Pg 313]</span>
+his position ever so little. Only the very longest
+base-line which can be found on earth will do for
+this,—nothing less than the earth’s whole diameter
+of nearly eight thousand miles. And I think you
+will see that the success of the calculation would
+then depend, not alone on most careful observation
+from two posts at the opposite sides of earth; not
+alone on mathematical gifts and powers of close reckoning;
+but also, essentially, on a true knowledge of
+our earth’s diameter; that is, of <i>the exact length of
+the base-line</i> from which the whole calculation would
+have to be made, and upon which the answer would
+largely depend.</p>
+
+<p>For a long while the earth’s diameter was not well
+known. As time went on, fresh measurements were
+again and again made of different portions of earth’s
+surface, fresh calculations following therefrom; and
+gradually clear conclusions were reached. A very
+important matter it was that they should be reached;
+for the semi-diameter of our earth has been adopted
+as a “standard measure” for the whole universe; and
+the slightest error in that standard measure would
+affect all after calculations.</p>
+
+<p>When actual observations of sun-distance came to be
+made, innumerable difficulties arose. Foremost stood
+the huge amount of that distance. This made precise
+observations more difficult; and at the same time
+it made every mistake in observation so much the
+worse. A little mistake in observing the moon
+might mean only a hundred miles or so wrong in the
+answer; but a mistake equally small in observing the
+sun would lead to an error of many millions of miles.</p>
+
+<p><span class="pagenum" id="Page_314">[Pg 314]</span></p>
+
+<p>Again, to observe the sun’s exact position among
+the stars, as with the moon, was not possible; because
+when the sun is visible, the stars are not visible.
+Then, too, the dazzling brightness of the sun balked
+the needed exactitude.</p>
+
+<p>Halley had a brilliant thought before he died. He
+could not carry it out himself, but he left it to others
+as a legacy; that was, by observing the transit of
+Venus from two different points on the earth’s surface.
+At his suggestion, on the first opportunity—which
+was not till after his death—the above mode
+was tried of measuring the sun’s distance.</p>
+
+<p>A certain observer, stationed on one part of earth,
+saw the tiny dark body of Venus take one particular
+line across the sun’s bright face. Another observer,
+standing on quite another and a far-off part of earth,
+saw the little dark body take quite another line across
+the sun’s bright face. Not that there were two little
+dark bodies, but that the one body was seen by different
+men in different places.</p>
+
+<p>From these separate views of the path of Venus
+across the face of the sun, in connection with what
+was already known of the earth’s diameter, and therefore
+of the length of base-line between the two places,
+the distance of the sun was reckoned to be about 95,000,000
+miles.</p>
+
+<p>Since that date many fresh attempts have been
+made, and errors have been set right. Mercury as
+well as Venus has been used in this matter, and other
+newer modes of measurement have also been successfully
+tried. We know now, with tolerable accuracy,
+that the sun’s greater distance from earth is between<span class="pagenum" id="Page_315">[Pg 315]</span>
+92,000,000 and 93,000,000 miles. A curious illustration
+of sun-distance has been offered by one writer.
+Sound and light, heat and sensation, all require <i>time</i>
+for journeying. When a child puts his finger into a
+candle-flame, he immediately shrieks with pain. Yet,
+quickly as the cry follows the action, his brain is not
+really aware of the burn until a certain interval has
+elapsed. True, the interval is extremely minute; still
+it is a real interval. News of the burn has to be telegraphed
+from the finger, through the nerves of the
+arm, up to the brain; and it occupies time in transmission,
+though so small a fraction of a second that
+we can not be conscious of it.</p>
+
+<p>Now, try to imagine a child on earth with an arm
+long enough to reach the sun. His fingers might be
+scorched by the raging fires there, while yet his brain
+on earth would remain quite unaware of the fact for
+about one hundred and thirty years. All through
+those years, sensation would be darting along the
+arm exactly as fast as it darts from the finger-tips of
+an ordinary child on earth to that child’s brain.</p>
+
+<p>If the scorching began before he was one year old,
+he would have become a very aged man, one hundred
+and thirty years old, before he could know in his mind
+what was happening in the region of his hand. Moreover,
+if, on receiving the intimation, he should decide
+to withdraw his hand from that unpleasantly-hot
+neighborhood, another hundred and thirty years would
+elapse before the fingers could receive and act upon
+the message, telegraphed from the brain, through the
+nerves of the arm. So much for the distance of the
+sun from our earth!</p>
+
+<p><span class="pagenum" id="Page_316">[Pg 316]</span></p>
+
+<p>But the stars! How far off are the stars?</p>
+
+<p>The distance of the moon is a mere nothing. The
+distances of the planets have been found out. The
+distance of the sun has been measured. But the
+stars—those wondrous points of light, twinkling on,
+night after night, century after century, unchanged in
+position save by the seeming nightly pilgrimage of
+them all across the sky in company, caused only by
+our earth’s restless, continual whirl,—</p>
+
+<p>What about the distances of the stars? Can we
+measure their distance by means of their parallax?
+This mode of measurement was tried successfully on
+the moon, on the planets, and on the sun. But when
+it was tried upon the stars, from two stations as far
+apart as any two stations on earth could be, the attempt
+was a failure. Not a ghost of parallax could
+be detected with any one star. Not the faintest sign
+of displacement was seen in the position of a single
+star when most critically and carefully examined.</p>
+
+<p>Then arose a brilliant thought! What of earth’s
+yearly journey round the sun? If a base-line of 8,000
+miles were not enough, compared with the great distance
+of the stars, this at least remained. Our earth
+at midsummer is somewhere about 185,000,000 miles
+away from where she is at midwinter, comparing her
+position with that of the sun, and reckoning him to
+be at rest.</p>
+
+<p>In reality, the sun is not at rest, but is in ceaseless
+motion, carrying with him, wherever he goes, the
+whole Solar System with as much ease as a train
+carries its passengers. Those passengers are truly in
+motion, yet, with regard merely to the train, they are<span class="pagenum" id="Page_317">[Pg 317]</span>
+at rest. So each member of the Solar System—attached
+to the sun, not by Ptolemaic bars, but by the
+bond of gravity—is borne along by him through
+space; yet, with respect to each member of that system,
+the central sun is always and absolutely at rest.</p>
+
+<p>At one time of the year, our earth is on one side of
+the sun, over 92,000,000 miles distant. Six months
+later, the earth is on the other side of the sun, not
+quite 93,000,000 miles away from him in that opposite
+direction. Twice 93,000,000 comes to 186,000,000.
+This line, therefore—the diameter of the earth’s whole
+yearly orbit, may be roughly stated as about 185,000,000
+of miles in length.</p>
+
+<p>Here surely was a base-line fit to give parallax to
+any star—or, rather, to make parallax visible in the
+case of any star. For it is, after all, a question, not of
+fact, but of visibility; not of whether the thing <i>is</i>, but
+of whether we are able to <i>see</i> it.</p>
+
+<p>As the earth journeys on her annual tour round the
+sun, following a slightly elliptic pathway, the diameter
+of which is about 185,000,000 miles, each star in the
+sky must of necessity undergo a change of position,
+however minute, performing a tiny apparent annual
+journey in exact correspondence with the earth’s great
+annual journey.</p>
+
+<p>The question is not, Does the star do this? but,
+Can we <i>see</i> the star do this? Its apparent change of
+position may be so infinitesimal, through enormous
+distance, that no telescopes or instruments yet made
+by man can possibly show it to us.</p>
+
+<p>The star-motion of which I am now speaking is
+purely a seeming movement, not real. Be very clear<span class="pagenum" id="Page_318">[Pg 318]</span>
+on this point in your mind. <i>Real</i> star-movements,
+though suspected earlier, were not definitely surmised—one
+may even say “discovered”—until the year
+1718, by Halley. And though Cassini in 1728 referred
+to this discovery of Halley’s, yet very little was
+heard about the matter until the days of Herschel.
+Only <i>apparent</i> star-motions were generally understood
+and accepted.</p>
+
+<p>The first and simplest of such seeming star-motions
+is one which we can all see—the nightly journey of
+the whole host of stars, caused by our earth’s whirl
+upon her axis.</p>
+
+<p>The second is also simple, but by no means also
+easily seen. Astronomers reasoned out the logical
+necessity for such an apparent motion long before it
+could be perceived. As far back as the days of Copernicus
+it was felt that if the Copernican System
+were true, if the earth in very deed traveled round
+the sun, then the stars ought to change their positions
+in the sky when viewed from different parts of earth’s
+annual journey. Observations were taken, divided by
+six months of time and by one hundred and eighty-five
+millions of miles of space. And the stars
+stirred not!</p>
+
+<p>Stupendous as was this base-line, it proved insufficient.
+So much <i>more</i> stupendous was the distance of
+the stars that the base-line sank to nothing, and once
+again parallax could not be detected. Not that the
+seeming change of position in the star did not take
+place, but that human eyes were unable to see it,
+human instruments were unable to register it.</p>
+
+<p>There lies the gist of the matter. If the change<span class="pagenum" id="Page_319">[Pg 319]</span>
+of position can be observed, well and good! The
+length of the base-line being known, the distance of
+the star may be mathematically calculated. For the
+size of the tiny apparent path, followed in a year by
+the star, is and must be exactly proportioned to the
+distance of the star from that base-line. If the tiny
+oval be so much larger, then the star is known to be
+so much nearer. If the tiny oval be so much smaller,
+then the star is known to be so much farther away.</p>
+
+<p>But when not the minutest token could be discovered
+of a star’s position in the sky being in the least
+degree affected by the earth’s great annual change of
+position, astronomers were at a loss. There was absolutely
+nothing to calculate from. The star was a
+motionless point to earth. The whole yearly orbit of
+earth was a motionless point to the star. One slender
+beam of light united the two. Reckoners had
+nothing to stand upon.</p>
+
+<p>It is interesting to know that Copernicus had actually,
+long before, suggested this as a possible explanation
+of the absence of star-parallax. He thought
+that astronomers might fail altogether to find it, because
+the stars might be “at a practically infinite distance”
+from our earth.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_320">[Pg 320]</span></p>
+
+<h2 class="nobreak" id="c27">CHAPTER XXVII.</h2>
+</div>
+
+<p class="c sp">MEASUREMENT OF STAR DISTANCES.</p>
+
+
+<p><span class="smcap large">Until</span> the days of Sir William Herschel, little attention
+was bestowed upon the universe of distant stars.
+Before his advent the interest of astronomers had been
+mainly centered in the sun and his revolving worlds.
+The “fixed stars” were indeed studied, as such, with
+a certain amount of care, and numberless efforts were
+made to discover their distances from earth; but the
+thought of a vast Starry System, in which our little
+Solar System should sink to a mere point by comparison
+with its immensity, had not yet dawned.</p>
+
+<p>With larger and yet larger telescopes of his own
+making, Herschel studied the whole Solar System, and
+especially the nature of sun-spots, the rings of Saturn,
+the various motions of attendant moons, together
+with countless other details. He enlarged the system
+by the discovery of another planet outside Saturn—the
+planet Uranus, till then unknown.</p>
+
+<p>These were only first steps. The work which he
+did in respect of the Solar System was as nothing
+compared with the work which he did among the
+stars. His work in our system was supplementary to
+other men’s labors; his work among the stars was the
+beginning of a new era. Like many before him, he,
+too, sought eagerly to find star-parallax, and he, too,
+failed. Not yet had instruments reached a degree of<span class="pagenum" id="Page_321">[Pg 321]</span>
+finish which should permit measuring operations of
+so delicate a nature.</p>
+
+<p>Although he might not detect star-parallax, he
+sprang a mine upon the older notions of star-fixity. He
+shook to its very foundations the sidereal astronomy of
+the day,—the theory, long held, of a motionless universe,
+motionless stars, and a rotating but otherwise
+motionless sun. He did away with the mental picture,
+then widely believed in, of vast interminable fixity
+and stillness, extending through space, varied only
+by a few little wandering worlds. As he swept the
+skies, and endeavored to gauge the fathomless depths,
+and vainly pursued the search for the parallax of one
+star after another, he made a great and unlooked-for
+discovery. This was in connection with double-stars.</p>
+
+<p>Double-stars had long been known, and were generally
+recognized. But whether the doubleness were
+purely accidental, due merely to the fact of two stars
+happening to lie almost in the same line of sight, as
+viewed from earth, or whether any real connection
+existed between the two, no man living could say.
+Indeed, so long as all stars were regarded as utter
+fixtures, the question was of no very great interest.</p>
+
+<p>But light dawned as Herschel watched. He found
+the separate stars in a certain pair to be moving.
+Each from time to time had slightly, very slightly,
+changed its place. Then, at least, if all other stars in
+the universe were fixed, those two were not fixed. He
+watched on, and gradually he made out that their motions
+were steady, were systematic, and were connected
+the one with the other. That was one of the first<span class="pagenum" id="Page_322">[Pg 322]</span>
+steps towards breaking down the olden notion, so
+widely held, of a fixed and unchanging universe.</p>
+
+<p>Another double-star, and yet another, responded to
+Herschel’s intense and careful searching. These other
+couples, too, were revolving, not separately, but in
+company; journeying together round one center;
+bound together apparently by bonds of gravitation,
+even as our sun and his planets are bound together.</p>
+
+<p>Other stars besides binary stars are found to move
+with a real and not merely a seeming movement.
+Viewed carelessly, the stars do indeed appear to remain
+fixed in changeless groups; fixed even through
+centuries. But, to exceedingly close watching and
+accurate measurement, many among them are distinctly
+<i>not</i> fixed; many among them can be actually
+seen to move.</p>
+
+<p>Of course the observed motions are very small and
+slow. One may be found to creep over a space as
+wide as the whole full moon in the course of three
+hundred or four hundred years; and this is rapid traveling
+for a star in earth’s sky! Another will perhaps
+cross a space one-tenth or one-twentieth or one-fiftieth
+of the moon’s width in one hundred years.</p>
+
+<p>Such motions had never been carefully noted or
+examined, until Herschel came to do away with
+the old received notions of star-fixity. Happily,
+Herschel was no slave to “received ideas.” Like
+Galileo in earlier times, he wished to “prove all
+things” personally, anxious only to find out what
+was the truth. And he found that the stars were <i>not</i>
+fixed! He found that numbers of them were moving.
+He conjectured that probably all the rest were<span class="pagenum" id="Page_323">[Pg 323]</span>
+moving also; that in place of a fixed universe of
+changeless stars we have a whirling universe of rushing
+suns.</p>
+
+<p>Herschel could not, of course, watch any one star
+for a hundred years, much less for several centuries.
+But in a very few years he could, by exceedingly close
+measurement, detect sufficient motion to be able to
+calculate how long it would take a certain star to creep
+across a space as wide as the full moon.</p>
+
+<p>From step to step he passed on, never weary of his
+toil. He sought to gauge the Milky Way, and to form
+some notion of its shape. He noted a general drift of
+stars to right and to left, which seemed to speak of a
+possible journey of our sun through space, with all
+the planets of the Solar System. He flung himself
+with ardor into the study of star-clusters and of nebulæ.
+He saw, with an almost prophetic eye, the
+wondrous picture of a developing universe—of nebulæ
+growing slowly into suns, and of suns cooling gradually
+into worlds—so far as to liken the heavens to a
+piece of ground, containing trees and plants in every
+separate stage of growth.</p>
+
+<p>And still the search for star parallax went on, so
+long pursued in vain. No longer base-line than that
+of the diameter of earth’s yearly orbit lay within man’s
+reach. But again and yet again the attempt was
+made. Instruments were improved, and measurements
+became ever more delicate; and at length some
+small success crowned these persistent endeavors. The
+tiny sounding-line of earth, lowered so often into the
+mysterious depths of space, did at last “touch bottom.”</p>
+
+<p>Herschel died, full of years and honors, in 1822;<span class="pagenum" id="Page_324">[Pg 324]</span>
+and some ten years later three different attempts
+proved, all to some extent, and almost at the same
+date, successful. Bessel, however, was actually the
+first in point of time; and his attempt was upon the
+double-star, 61 Cygni; not at all a bright star, but only
+just visible to the naked eye.</p>
+
+<p>There are stars and stars, enough to choose from.
+The difficulty always was, which to select as a subject
+for trial with any reasonable prospect of a good result.
+Some astronomers held that the brightest stars were the
+most hopeful, since they were probably the nearest;
+and of course the nearer stars would show parallax
+more readily, because their parallax would be the
+greater. But certain very bright stars indeed are
+now known to be far more distant than certain very
+dim stars.</p>
+
+<p>Again, some astronomers thought that such stars
+as could be perceived to move most rapidly in the
+course of years would be the most hopeful objects to
+attack, since the more rapid movement might be supposed
+to mean greater nearness, and so greater ease
+of measurement. But some stars, seen to move rapidly,
+are now known to be more distant than others
+which are seen to move more sluggishly. So neither
+of these two rules could altogether be depended on;
+yet both were, on the whole, the best that could be
+followed, either separately or together.</p>
+
+<p>The star 61 Cygni is not one of the brighter stars,
+but it is one of those stars which can be seen to travel
+most quickly across the sky in the course of a century.
+Therefore it was selected for a trial; and that
+trial was the first to meet with success.</p>
+
+<p><span class="pagenum" id="Page_325">[Pg 325]</span></p>
+
+<p>For 61 Cygni was found to have an apparent parallax;
+in other words, its tiny seeming journey through
+the year, caused by our earth’s great journey round
+the sun, could be detected. Small as the star-motion
+was, it might, through careful measurement, be perceived.
+And, in consequence, the distance of the star
+from earth could be measured. Not measured with
+anything like such exactitude as the measurements of
+sun-distance, but with enough to give a fair general
+notion of star-distance.</p>
+
+<p>One success was speedily followed by others. By
+a few others,—not by many. Among the thousands of
+stars which can be seen by the naked eye, one here and
+one there responded faintly to the efforts made. One
+here and one there was found to stir slightly in the
+sky, when viewed from earth’s summer and winter
+positions, or from her spring and autumn positions, in
+her yearly pathway round the sun.</p>
+
+<p>It was a very, very delicate stir on the part of the
+star. Somewhat like the difference in position which
+you might see in a penny a few miles off, if you looked
+at it first out of one window and then out of another
+window in the same house. You may picture the
+penny as radiantly bright, shining through pitch darkness;
+and you may picture yourself as looking at it
+through a telescope. But even so, the apparent change
+of position in the penny, viewed thus, would be exceedingly
+minute, and exceedingly difficult to see.</p>
+
+<p>There are two ways of noting this little seeming
+movement on the part of a star in the sky.</p>
+
+<p>Either its precise place in the sky may be observed—its
+exact position, as in a map of the heavens—or<span class="pagenum" id="Page_326">[Pg 326]</span>
+else its place may be noted as compared with another
+more distant star, near to it in the sky, though
+really far beyond. Parallax, if visible, would make it
+alter its precise place in the sky. Parallax, if visible,
+would bring it nearer to or farther from any other
+star more distant than itself from earth. The more
+distant star would have a much smaller parallax—probably
+so small as to be invisible to us—and so it
+would do nicely for a “comparison star.”</p>
+
+<p>The first of these methods was the first tried; and
+the second was the first successful.</p>
+
+<p>To find star-distance through star-parallax sounds
+quite simple, when one thinks of the general principle
+of it. Just merely the question of a base-line, accurately
+measured; and of two angles, accurately observed;
+and of another angle, a good way off, accurately calculated,—all
+resting on the slight seeming change of
+position in a certain distant object, watched from two
+different positions, about 185,000,000 miles apart.</p>
+
+<p>Quite simple, is it not? Only, when one comes to
+realize that the “change of position” is about equal
+to the change of position in a penny piece, miles away,
+looked at from two windows in one house,—then the
+difficulty grows.</p>
+
+<p>Besides this, one has to remember all the “corrections”
+necessary, before any true result can be
+reached.</p>
+
+<p>A penny piece, miles away, seen from two windows,
+would be difficult enough as a subject for measurement.
+But, at least, the penny would be at rest; and
+you yourself would be at rest; and light would pass
+instantaneously from it to you; and there would be no<span class="pagenum" id="Page_327">[Pg 327]</span>
+wobbling and nodding motions of everything around
+to add to your perplexities.</p>
+
+<p>In the measurement of star-parallax, all these
+things have to be considered and allowed for; all have
+to be put out of the question, as it were, before any
+correct answer is obtained.</p>
+
+<p>The refraction of light must be considered; because
+that displaces the star, and makes it seem to us to be
+where it is not. And the aberration of light must be
+considered; because, in a different way, that does the
+same thing, making the star seem to take a little journey
+in the course of the year. And the precession, or
+forward motion, of the equinoxes, and nutation, or
+vibratory motion, have both to be separately considered;
+because they, too, affect the apparent position
+of every star in the sky.</p>
+
+<p>To watch the star in comparison with another star
+is easier than merely to note its exact position in the
+sky; for the other star—the “companion-star”—is
+equally with itself affected by refraction of light and
+by aberration of light. But, then, another question
+comes in seriously: whether or no the companion-star
+shows any parallax also; since, if it does, that parallax
+must be carefully calculated and allowed for.</p>
+
+<p>So the measurement of star-distance, even when
+parallax can be detected, is by no means a light or
+easy matter. On the contrary, it bristles with difficulties.
+It is a most complicated operation, needing
+profound knowledge, accurate observation, trained
+powers of reasoning and calculation.</p>
+
+<p>Nothing short of what has been termed “the terrific
+accuracy” of the present day could grapple with<span class="pagenum" id="Page_328">[Pg 328]</span>
+the truly tremendous difficulties of this problem of star-distance.
+It has, however, been grappled with, and
+grappled with successfully. We now know, not indeed
+with anything like exactitude, yet with reasonable
+certainty, the distances of a good many stars, as
+expressed roughly in round number of “about” so
+many trillions of miles.<a id="FNanchor_3" href="#Footnote_3" class="fnanchor">[3]</a> We have at least learned
+enough to gain some notion of the immeasurable distances
+of countless other stars, lying far beyond reach
+of earth’s longest measuring-line.</p>
+
+<div class="footnote">
+
+<p><a id="Footnote_3" href="#FNanchor_3" class="label">[3]</a> The diameter of the moon as seen from the earth is equal to one thousand
+eight hundred and sixty eight seconds of space. When the parallax of a star
+is ascertained, it is a simple matter to calculate the distance of the star by the
+use of the following table. If the star shows a displacement of one second in
+space, or one eighteen-hundred-and-sixty-eighth part of the width of the moon,
+that star is distant two hundred and six thousand two hundred and sixty-five
+times the distance of the earth from the sun.</p>
+
+<table>
+
+<tr>
+  <td class="tdl">An angle of</td>
+  <td class="tdl">1″</td>
+  <td class="tdl">is equivalent to</td>
+  <td class="tdl">206,265 times</td>
+  <td class="tdl">93,000,000 of miles.</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.9</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">229,183  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160;  &#160; &#160;     “  &#160; &#160; &#160; &#160;     “  &#160; &#160;    “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.8</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">257,830  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.7</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">294,664  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.6</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">343,750  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.5</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">412,530  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.4</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">515,660  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.3</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">687,500  &#160; &#160;    “</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.2</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">1,031,320 &#160;“</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.1</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl">2,062,650 &#160;“</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;       “ &#160; &#160; &#160;  &#160;     “ &#160; &#160;      “</td>
+</tr>
+
+<tr>
+  <td class="tdl"> &#160;“  &#160; &#160; &#160; “  &#160; &#160;  “  </td>
+  <td class="tdl">0″.0</td>
+  <td class="tdl"> “  &#160; &#160; &#160; &#160;     “   &#160; &#160; &#160; &#160;    “</td>
+  <td class="tdl"><span class="less">Immeasurable.</span> &#160;</td>
+  <td class="tdl"> &#160; &#160; &#160; &#160; &#160;        &#160; &#160; &#160;  &#160;      &#160; &#160;      </td>
+</tr>
+
+</table>
+
+
+<p>The nearest star, Alpha Centauri, shows a parallax of less than one second
+(0″.75). The farthest star, the distance of which has been ascertained, is 1830
+Groombridge, which shows a parallax of only 0″.045, and is distant 4,583,000
+times earth’s distance from the sun, or 426 trillions of miles.</p>
+
+</div>
+
+<p>The very thought of such unimaginable depths of
+space, of suns beyond suns “in endless range,” toned
+down by simple distance to mere quivering specks of
+light, is well-nigh overwhelming.</p>
+
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_329">[Pg 329]</span></p>
+<h2 class="nobreak" id="c28">CHAPTER XXVIII.</h2>
+</div>
+
+<p class="c sp">THE MILKY WAY.</p>
+
+
+<p><span class="smcap large">The Milky Way</span> forms a soft band of light round
+the whole heavens. In the Southern Hemisphere, as
+in the Northern Hemisphere, it is to be seen. In some
+parts the band narrows; in some parts it widens. Here
+it divides into two branches; there we find dark spaces
+in its midst. One such space in the south is so black
+and almost starless as to have been named the Coal-sack.
+All along, over the background of soft, dim
+light, lies a scattering of brighter stars shining on its
+surface. Much interest and curiosity have long been felt
+about this mysterious Milky Way. That it consists
+of innumerable suns, and that our sun is one among
+them, has been believed for a considerable time. But
+other questions arise. How many stars does the
+Milky Way contain? What is its shape? How far
+does it reach?</p>
+
+<p>No harm in asking the questions, only we have to
+be satisfied in astronomy to ask many questions which
+can not yet receive answers. No harm for man to
+learn that the utmost reach of his intellect must fall
+short in any attempt to sound the depths of God’s
+universe, even as the arm of a child would fall short
+in seeking to sound the depths of the ocean over the
+side of a little boat. For the attempt has been made
+to sound the depths of our star-galaxy out of this little
+earth-boat.</p>
+
+<p><span class="pagenum" id="Page_330">[Pg 330]</span></p>
+
+<p>The idea first occurred to the great Herschel, as
+we have already mentioned, and a grand idea it was—only
+a hopeless one. He turned his powerful telescope
+north, south, east, west. He counted the stars
+visible at one time in this, in that, in the other directions.
+He found a marked difference in the numbers.
+The portion of sky seen through his telescope was
+about one quarter the size of that covered by the
+moon. Sometimes he could merely perceive two or
+three bright points on a black background. At other
+times the field of his telescope was crowded. In the
+fuller portions of the Milky Way, he had four or five
+hundred stars under view at once. In one place he
+saw about one hundred and sixteen thousand stars
+pass before him in a single quarter of an hour.</p>
+
+<p>Herschel took it for granted that the stars of the
+Milky Way, uncountable in numbers, are, as a rule,
+much the same in size—so that brightest stars would,
+as a rule, be nearest, and dimmest stars would, as a
+rule, be farthest off. Where he found stars clustering
+thickly, beyond his power to penetrate, he believed
+that the Milky Way reached very far in that direction.
+Where he found black space, unlighted by stars
+or lighted by few stars, he decided that he had found
+the borders of our galaxy in that direction.</p>
+
+<p>Following these rules which he had laid down, he
+made a sort of rough sketch of what he supposed
+might be the shape of the Milky Way. He thought
+it was somewhat flat, extending to a good distance
+breadthways and a much greater distance lengthways,
+and he placed our sun not far from the middle. This
+imagined shape of the Milky Way is called “The<span class="pagenum" id="Page_331">[Pg 331]</span>
+Cloven-disk Theory.” To explain the appearance of
+the Milky Way in the sky, Herschel supposed it to be
+cloven or split through half of its length, with a black
+space between the two split parts.</p>
+
+<p>It seems that Herschel did not hold strongly to
+this idea in later years, and doubts are now felt
+whether the rules on which he formed it have sufficient
+foundation.</p>
+
+<p>For how do we know that the stars of the Milky
+Way are, as a rule, much the same in size? Certainly
+the planets of the Solar System are very far from being
+uniform, and the few stars whose weight can with
+any certainty be measured, seem to vary considerably.
+There is a great difference also between the large and
+small suns in many of the double-stars!</p>
+
+<p>Again, how do we know that the bright stars are,
+as a rule, the nearest, and the dim stars the farthest
+off? Here, also, late discoveries make us doubtful.
+Look at Sirius and 61 Cygni—Sirius the most radiant
+star in the heavens, and 61 Cygni almost invisible to
+the naked eye. According to this rule, 61 Cygni
+ought to lie at an enormous distance beyond Sirius.
+Yet in actual fact, Sirius is the farthest away of
+the two.</p>
+
+<p>The illustrious Herschel believed that he had penetrated,
+on one occasion, into the star-cluster on the
+sword-hand in the constellation of Perseus until he
+found himself among sidereal depths, from which the
+light could not have reached him in less than four
+thousand years.</p>
+
+<p>The distance of those stars had not, and has not,
+been mathematically measured. Herschel judged of<span class="pagenum" id="Page_332">[Pg 332]</span>
+it by their dimness, by the strong power needed to
+make them visible, and by the rules which he had
+adopted as most likely true.</p>
+
+<p>Again, when Herschel found black spaces in the
+heavens almost void of stars, and believed that he
+had reached the outside borders of the Milky Way,
+he may have been in the right, or he may have been
+mistaken. The limit might lie there, or thousands
+more of small stars might extend in that very direction,
+too far off for their little glimmer to be seen
+through the most powerful telescope.</p>
+
+<div class="figcenter" id="f55">
+<img src="images/fig55.jpg" alt="cluster">
+<p class="caption">A CLUSTER OF STARS IN PERSEUS.</p>
+</div>
+
+<p>If this latter idea about the Milky Way being
+formed of a great many brilliant suns, and of vast
+numbers of lesser suns also, be true, astronomers<span class="pagenum" id="Page_333">[Pg 333]</span>
+will, in time, be able to prove its truth. For in that
+case, many faint telescopic stars being much nearer
+to us than bright stars of the greater magnitudes, it
+will be found possible to measure their distance.
+The journey of our earth round the sun must cause
+a seeming change in their position between summer
+and winter.</p>
+
+<p>The theory also that some of the nebulæ are other
+outlying Milky Ways, or galaxies of stars, separated
+by tremendous distances from our own, is interesting,
+and was long held as almost certain, yet we have no
+distinct proof either one way or the other. Many of
+the nebulæ may be such gatherings of countless stars
+outside our own, or every nebula visible may be actually
+part and parcel of our galaxy.</p>
+
+<p>Much attention has of late been paid to the arrangement
+of stars in the sky. The more the matter
+is looked into, the more plainly it is seen that stars
+are neither regular in size nor regular in distribution.
+They are not merely scattered carelessly, as it were,
+here, there, and anywhere, but certain laws and plans
+of arrangement seem to have been followed which
+astronomers are only now beginning dimly to perceive.</p>
+
+<p>Stars are not flung broadcast through the heavens,
+each one alone and independent of the rest. They
+are placed often, as we have already seen, in pairs, in
+triplets, in quartets, in clusters. Also, the great masses
+of them in the heavens seem to be more or less arranged
+in streams, and sprays, and spirals. So remarkable
+are the numbers and forms of many of these
+streams that the idea has been suggested, with regard
+to the Milky Way, whether it also may not be a vast<span class="pagenum" id="Page_334">[Pg 334]</span>
+stream of stars, like a mighty river, collecting into itself
+hundreds of lesser streams.</p>
+
+<p>The contemplation of the heavens affords no spectacle
+so grand and so eloquent as that of a cluster of
+stars. Most of them lie at such a distance that the
+most powerful telescopes still show them to us like
+star-dust. “Their distance from us is such that they
+are beyond, not only all our means of measurement,”
+says Newcomb, “but beyond all our powers of estimation.
+Minute as they appear, there is nothing that we
+know of to prevent our supposing each of them to be
+the center of a group of planets as extensive as our
+own, and each planet to be as full of inhabitants as
+this one. We may thus think of them as little colonies
+on the outskirts of creation itself, and as we see
+all the suns which give them light condensed into one
+little speck, we might be led to think of the inhabitants
+of the various systems as holding intercourse with
+each other. Yet, were we transported to one of these
+distant clusters, and stationed on a planet circling one
+of the suns which compose it, instead of finding the
+neighboring suns in close proximity, we should see a
+firmament of stars around us, such as we see from the
+earth. Probably it would be a brighter firmament, in
+which so many stars would glow, with more than the
+splendor of Sirius, as to make the night far brighter
+than ours; but the inhabitants of the neighboring
+worlds would as completely elude telescopic vision as
+the inhabitants of Mars do here. Consequently, to
+the inhabitants of every planet in the cluster, the question
+of the plurality of worlds might be as insolvable
+as it is to us.”</p>
+
+<p><span class="pagenum" id="Page_335">[Pg 335]</span></p>
+
+<p>These are clusters of stars of regular form in which
+attraction appears to mark its secular stamp. Our
+mind, accustomed to order in the cosmos, anxious for
+harmony in the organization of things, is satisfied with
+these agglomerations of suns, with these distant universes,
+which realize in their entirety an aspect approaching
+the spherical form. More extraordinary,
+more marvelous still, are the clusters of stars which
+appear organized in spirals.</p>
+
+<p>In considering stars of the first six magnitudes
+only—stars visible to the naked eye—a somewhat
+larger number is found in the Southern Hemisphere
+than in the Northern Hemisphere. In both hemispheres
+there are regions densely crowded with stars,
+and regions by comparison almost empty.</p>
+
+<p>It has been long questioned whether the number
+of bright stars is or is not greater in the Milky Way
+than in other parts of the sky. Careful calculations
+have at length been made. It appears that the whole
+of the Milky Way—that zone of soft light passing
+round the earth—covers, if we leave out the Coal-sack
+and other such gaps, between one-tenth and one-eleventh
+of the whole heavens.</p>
+
+<p>The entire number of naked-eye stars, or stars of
+the first six magnitudes, does not exceed six thousand;
+and of these, eleven hundred and fifteen lie scattered
+along the bed of the Milky Way stream. If the
+brighter stars were scattered over all the sky as thickly
+as throughout the Milky Way, their number would
+amount to twelve thousand instead of only six thousand.
+This shows us that the higher-magnitude stars
+really are collected along the Milky Way in greater<span class="pagenum" id="Page_336">[Pg 336]</span>
+numbers than elsewhere, and is an argument used by
+those who believe the Milky Way to be a mighty
+stream of streams of stars.</p>
+
+<p>In the dark spaces of the Milky Way, on the contrary,
+bright stars are so few that if they were scattered
+in the same manner over all the sky, their present
+number of six thousand would come down to
+twelve hundred and forty. This would be a serious
+loss.</p>
+
+<p>We know in the sky 1,034 clusters of stars and
+more than 11,000 nebulæ. The former are composed
+of associated stars; the latter may be divided into two
+classes: First, nebulæ which the ever-increasing progress
+of optics will one day resolve into stars, or which
+in any case are composed of stars, although their distances
+may be too great to enable us to prove it;
+second, nebulæ properly so called, of which spectrum
+analysis demonstrates their gaseous constitution.
+Here is an instructive fact. The clusters of stars
+present the same general distribution as the telescopic
+stars—they are more numerous in the plane of the
+Milky Way, while it is the contrary which is presented
+by the nebulæ properly so called; they are rare, thinly
+spread in the Milky Way, and thickly scattered to the
+north as well as to the south of this zone up to its
+poles. The constitution of the Milky Way—not nebulous,
+but stellar—is a very significant fact. The
+nebulæ properly so called are distributed, in a sense,
+contrary to the stars, being more numerous towards
+the poles of the Milky Way and in regions poor in
+stars, as if they had absorbed the matter of which the
+stars are formed.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_337">[Pg 337]</span></p>
+
+<h2 class="nobreak" id="c29">CHAPTER XXIX.</h2>
+</div>
+
+<p class="c sp">A WHIRLING UNIVERSE.</p>
+
+
+<p><span class="smcap large">No rest,</span>, no quiet, no repose, in that great universe,
+which to our dim eyesight looks so fixed and
+still, but one perpetual rush of moving suns and
+worlds. For every star has its own particular motion,
+every sun is pressing forward in its own appointed
+path. And among the myriads of stars—bright,
+blazing furnaces of white or golden, red, blue,
+or green flame—sweeping with steady rush through
+space, our sun also hastens onwards.</p>
+
+<p>The rate of his speed is not very certain, but it is
+generally believed to be about one hundred and fifty
+million miles each year. Possibly he moves in reality
+much faster.</p>
+
+<p>When I speak of the sun’s movement, it must of
+course be understood that the earth and planets all
+travel with him, much as a great steamer on the sea
+might drag in his wake a number of little boats.
+From one of the little boats you could judge of the
+steamer’s motion quite as well as if you were on the
+steamer itself. Astronomers can only judge of the
+sun’s motion by watching the seeming backward drift
+of stars to the right and left of him; and the watching
+can be as well accomplished from earth as from
+the sun himself.</p>
+
+<p>After all, this mode of judging is, and must be,
+very uncertain. Among the millions of stars visible,<span class="pagenum" id="Page_338">[Pg 338]</span>
+we only know the real distances of about twenty-five;
+and every star has its own real motion, which has to
+be separated from the apparent change of position
+caused by the sun’s advance.</p>
+
+<p>It seems now pretty clear that the sun’s course is
+directed towards a certain point in the constellation
+Hercules. If the sun’s path were straight, he might be
+expected by and by, after long ages, to enter that constellation.
+But if orbits of suns, like orbits of planets,
+are ellipses, he will curve away sideways long before
+he reaches Hercules.</p>
+
+<div class="figcenter" id="f56">
+<img src="images/fig56.jpg" alt="hercules">
+<p class="caption">HERCULES</p>
+</div>
+
+<p>One German astronomer thought he had found the
+center of the sun’s orbit. He believed the sun and
+the stars of the Milky Way to be traveling round the
+chief star in the Pleiades, Alcyone. This is not impossible;
+but it is now felt that much stronger proof
+will be required before the idea can be accepted.</p>
+
+<p>In the last chapter mention was made of star-streams
+as a late discovery. Though a discovery still
+in its infancy, it is one of no small importance. Briefly<span class="pagenum" id="Page_339">[Pg 339]</span>
+stated, the old theory as to the plan of the Milky Way
+was as follows: Our sun was a single star among millions
+of stars forming the galaxy, some comparatively
+near, some lying at distances past human powers of
+calculation, and all formed upon much the same model
+as to size and brightness. Where the band of milky
+light showed, stars were believed to extend in countless
+thousands to measureless distances. Where dark
+spaces showed, it was believed that we looked beyond
+the limits of our universe into black space. Stars scattered
+in other parts of the sky were supposed generally
+to be outlying members of the same great Milky Way.
+Many of the nebulæ and star-clusters were believed to
+be vast and distant gatherings of stars, like the Milky
+Way itself, but separated by unutterably wide reaches
+of space. Some of these views may yet be found to
+contain truth, though at the present moment a different
+theory is afloat.</p>
+
+<p>It is still thought probable that our sun is one among
+many millions of suns, forming a vast system or collection
+of stars, called by some a universe. It is also
+thought possible that other such mighty collections of
+stars may exist outside and separate from our own at
+immense distances. It is thought not impossible or
+improbable that some among the nebulæ may be such
+far-off galaxies of stars; though, on the other hand, it
+is felt that every star-cluster and nebula within reach
+of man’s sight may form a part of our own “universe.”</p>
+
+<p>According to this view of the question, the Milky
+Way, instead of being an enormous universe of countless
+suns reaching to incalculable distances, may<span class="pagenum" id="Page_340">[Pg 340]</span>
+rather be a vast and mighty star-stream, consisting of
+hundreds of brilliant leading suns, intermixed with
+thousands or even millions of lesser shining orbs. If
+this be the true view, the lesser suns would often be
+nearer than the greater suns, although more dim;
+and the Milky Way would not be itself a universe,
+though a very wonderful and beautiful portion of our
+universe.</p>
+
+<p>Which of these two different theories or opinions
+contains the most truth remains to be found out. But
+respecting the arrangement of stars into streams, interesting
+facts have lately been discovered. We certainly
+see in the Solar System a tendency of heavenly
+bodies to travel in the same lines and in companies.
+Not to speak of Jupiter and his moons, or Saturn and
+his moons, we see it more remarkably in the hundreds
+of asteroids pursuing one path, the millions of meteorites
+whirling in herds. Would there be anything
+startling in the same tendency appearing on a mightier
+scale? Should we be greatly astonished to find
+streams of stars, as well as streams of planets?</p>
+
+<p>For such, indeed, appears to be the case. Separated
+by abysses of space, brother suns are plainly to
+be seen journeying side by side through the heavens,
+towards the same goal.</p>
+
+<p>The question of star-drift is too complex and difficult
+to be gone into closely in a book of this kind.
+One example, however, may be given. Almost everybody
+knows by sight the constellation of the Great
+Bear—the seven principal stars of which are called also
+Charles’s Wain, a corruption of the old Gothic <i>Karl
+Wagen</i>, the churl’s or peasant’s wagon. It is also<span class="pagenum" id="Page_341">[Pg 341]</span>
+called the Great Dipper. Four bright stars form a
+rough sort of oblong, and from one of the corners
+three more bright stars stretch away in a curve, representing
+the Bear’s tail. Many smaller stars are intermixed.</p>
+
+<div class="figcenter" id="f57">
+<img src="images/fig57.jpg" alt="bear">
+<p class="caption">THE GREAT BEAR.</p>
+</div>
+
+<p>These seven bright stars have always been bound
+together in men’s minds, as if they belonged to one
+another. But who, through the centuries past, since
+aught was known of the real distances of the stars
+from ourselves and from one another, ever supposed
+that any among the seven were <i>really</i> connected together?</p>
+
+<p>One of these seven stars, the middle one in the
+tail, has a tiny companion-star, close to it, visible to<span class="pagenum" id="Page_342">[Pg 342]</span>
+the naked eye. For a good while it was uncertain
+whether the two were a “real double,” or only a seeming
+double. In time it became clear that the two did
+actually belong to one another.</p>
+
+<p>Mizar is the name of the chief star, and Alcor of
+the companion. Alcor is believed to be about three
+thousand times as far away from Mizar, as our earth
+from the sun. Now, if this be the width of space between
+those two bright points, lying seemingly so close
+together as almost to look to the naked eye like one,
+what must be the distance between the seven leading
+stars of the Great Bear, separated by broad sky-spaces?
+Who could imagine that one of these suns had aught
+to do with the rest?</p>
+
+<p>Yet among other amazing discoveries of late years
+it has been found by means of the new instrument,
+the spectroscope, that <i>five</i> out of these seven suns are
+traveling the same journey, with the same speed. Two
+of the seven appear to be moving in another direction,
+but three of the body-stars and two of the tail-stars
+are hastening in the direction away from us, all in the
+same line of march, all rushing through space at the
+rate of twenty miles each second. Some smaller stars
+close to them are also moving in the same path. Is
+not this wonderful? We see here a vast system of
+suns, all moving towards one goal, and each probably
+bearing with him his own family of worlds.</p>
+
+<p>Many such streams have been noticed, and many
+more will doubtless be found. For aught we know,
+our own sun may be one among such a company of
+brother-suns, traveling in company.</p>
+
+<p>It is difficult to give any clear idea of the immensity<span class="pagenum" id="Page_343">[Pg 343]</span>
+of the universe—even of that portion of the universe
+which lies within reach of our most powerful
+telescopes. How far beyond such limits it may reach,
+we lose ourselves in imagining.</p>
+
+<p>Earlier in the book we have supposed possible models
+of the Solar System, bringing down the sun and
+worlds to a small size, yet keeping due proportions.
+What if we were to attempt to make a reduced model
+of the universe; that is of just so much of it as
+comes within our ken?</p>
+
+<p>Suppose a man were to set himself to form such a
+model, including every star which has ever been seen.
+Let him have one tiny ball for the sun, and another
+tiny ball for Alpha Centauri; and let him, as a beginning,
+set the two <i>one yard apart</i>. That single yard
+represents ninety-three millions of miles, two hundred
+and seventy-five thousand times repeated. Then let
+him arrange countless multitudes of other tiny balls,
+at due distances—some five times, ten times, twenty
+times, fifty times, as far away from the sun as Alpha
+Centauri.</p>
+
+<p>It is said that the known universe, made upon a
+model of these proportions, would be many miles in
+length and breadth. But the model would appear
+fixed as marble. The sizes and distances of the stars
+being so enormously reduced, their rates of motion
+would be lessened in proportion. Long intervals of
+time would need to pass before the faintest motion in
+one of the millions of tiny balls could become visible
+to a human eye.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_344">[Pg 344]</span></p>
+
+<h2 class="nobreak" id="c30">CHAPTER XXX.</h2>
+</div>
+
+<p class="c sp">READING THE LIGHT.</p>
+
+<div class="figcenter" id="f58">
+<img src="images/fig58.jpg" alt="prism">
+<p class="caption">THE PRISM AND SPECTRUM.</p>
+</div>
+
+<p><span class="smcap large">Several</span> times, in the course of this book, mention
+has been made of a wonderful new instrument called
+the spectroscope. We now proceed to give a brief
+account of the origin and achievements of this newest
+of scientific appliances. The first step towards its
+formation was made by Sir Isaac Newton, when he
+discovered the power of the prism to decompose light.
+This consists in the fact that a ray of light, after passing
+through a transparent prism, becomes expanded
+into an elongated spectrum, no longer white, but presenting
+an invariable succession of colors from red to
+violet. These are called the seven primary colors;
+namely, red, orange, yellow, green, blue, indigo, and
+violet. The rainbow is a familiar illustration of this<span class="pagenum" id="Page_345">[Pg 345]</span>
+spectrum with its various colors; and the raindrops
+are the prisms which reflect and decompose the light.</p>
+
+<div class="figcenter" id="f59">
+<img src="images/fig59.jpg" alt="spectroscope">
+<p class="caption">THE SPECTROSCOPE.</p>
+</div>
+
+<p>Optical science was long satisfied with this glance
+into the interior constitution of light, occupying itself
+with the phenomena of the prismatic colors, and theorizing
+on the nature of white light. In 1802, Dr.
+W. H. Wollaston, in closely examining a spectrum,
+found it to be crossed by at least four fine dark lines.
+It is only when an extremely narrow slit is employed
+in admitting the sunlight that they become visible.
+Dr. Wollaston, supposing them to be merely “natural
+boundaries” of the different color-bands, inquired no
+further; and there for a while the matter rested. Not
+many years later, in 1815, the matter was taken up by
+a German optician and scientist of Munich, Joseph
+von Fraunhofer. Applying more delicate means of
+observation, he was surprised to find very numerous
+dark lines crossing the spectrum.</p>
+
+<p>With patience he went into the question, using the<span class="pagenum" id="Page_346">[Pg 346]</span>
+telescope as well as a very narrow slit, and soon he
+discovered that the dark lines were to be numbered,
+not by units or by tens, but by hundreds—or, as we
+now know, by thousands. Some were in the red, some
+were in the violet, some were in the intermediate
+bands; but each one had, and has, its own invariable
+position on the solar spectrum. For, be it understood,
+these dark lines are constant, not variable. Where a
+line is seen, there it remains. Whenever a ray of sunlight
+is properly examined, with slit and with prism,
+that line will be found always occupying precisely the
+same spot in the spectrum.</p>
+
+<p>Some of the chief and more distinct lines were
+named by Fraunhofer after certain letters of the alphabet,
+and by those letter-names they are still known.
+He began with A in the red and went on to H in the
+violet. Fraunhofer made a great many experiments
+connected with these mysterious lines, anxious to discover,
+if possible, their meaning. For although he
+now saw the lines, which had scarcely so much as
+been seen before, he could not understand them—he
+could not read what they said. They spoke to him,
+indeed, about the sun; but they spoke in a foreign
+language, the key to which he did not possess. He
+tried making use of prisms of different materials,
+thinking that perhaps the lines might be due to something
+in the nature of the prism employed. But let
+the prism be what it might, he found the lines still
+there. Then he examined the light which shines from
+bright clouds, instead of capturing a ray direct from
+the sun. And he found the lines still there. For
+cloudlight is merely reflected sunlight.</p>
+
+<p><span class="pagenum" id="Page_347">[Pg 347]</span></p>
+
+<p>Then he examined the light of the moon, to see if
+perchance the spectrum might be clear of breaks.
+And he found the lines still there. For moonlight is
+only reflected sunlight. Next he set himself to examine
+the light which travels to us
+from some of the planets, imagining
+that a different result might follow.
+And he found the lines still there.
+For planet-light again is no more than
+reflected sunlight.</p>
+
+<div class="figright" id="f60">
+<img src="images/fig60.jpg" alt="spectra">
+<p class="caption">SPECTRA, SHOWING<br>
+THE DARK LINES.</p>
+</div>
+
+<p>Lastly, he turned his attention to
+some of the brighter stars, examining,
+one by one, the ray which came from
+each. And, behold! he found the lines
+<i>not</i> there. For starlight is not reflected
+sunlight. That is to say, the
+identical lines which distinguish sunlight
+were not there. Each star had
+a spectrum as the sun has a spectrum,
+and each star-spectrum was crossed by
+faint dark lines, more or less in number.
+But the spectra of the stars differed
+from the spectrum of the sun.
+Each particular star had its own particular
+spectrum of light, different
+from that of the sun, and different
+from that of every other star. For now,
+Fraunhofer was examining, not sunlight,
+but starlight; not the light of our sun, either
+direct from himself or reflected from some other
+body, such as planet or moon or cloud, but the light
+of other suns very far distant, each one varying<span class="pagenum" id="Page_348">[Pg 348]</span>
+to some extent from the rest in its make. The
+fact of the stars showing numerous sets of black
+lines, all unlike those of our sun, showed conclusively
+that those lines could not possibly be due to
+anything in our earthly atmosphere. Sunlight and
+starlight travel equally through the air, and are equally
+affected by it. If our atmosphere were the cause of
+the black lines in sunlight, it would cause the <i>same</i>
+lines in starlight. But the sun and each individual
+star has its own individual lines, quite irrespective of
+changeful states of the air.</p>
+
+<p>So, also, the light from any metal sufficiently heated
+will give a spectrum, just as sunlight gives a spectrum,
+under the needful conditions. That is to say, there
+must be slit and prism, or slit and diffraction-grating,
+for the light to pass through. But the kind of spectrum
+is by no means always the same.</p>
+
+<p>Putting aside for a few minutes the thought of
+sunlight and starlight, let us look at the kind of rays
+or beams which are given forth by heated earthly
+substances. Any very much heated substance sends
+forth its light in rays or beams, and any such rays or
+beams may be passed through a prism, and broken
+up or “analyzed,” just as easily as sunlight may be
+“analyzed.”</p>
+
+<p>Suppose that we have a solid substance first—a
+piece of iron or of steel wire. If it is heated so far as
+to give out, not only heat, but also light, and if that
+light is made to travel through the slit and prism of a
+spectroscope, the ray will then be broken up into its
+sub-rays. They, like the sub-rays of a sunbeam, will
+form a continuous row of soft color-bands, one melting<span class="pagenum" id="Page_349">[Pg 349]</span>
+into another. This is the characteristic spectrum
+of the light which is given forth by a burning or glowing
+<i>solid</i>.</p>
+
+<p>Next, suppose we take a liquid—some molten iron
+or some molten glass, for instance. If you have ever
+been to a great plate-glass manufactory, like that at
+St. Helens, not far from Manchester, you will have
+seen streams of liquid glass pouring about, carried to
+and fro in huge caldrons, bright with a living light of
+fire from its intensity of heat. If a ray of <i>that</i> light
+had been passed through slit and prism, what do you
+think would have been the result? A continuous
+spectrum once more, the same as with the glowing
+iron or steel. The light-ray from a heated and radiant
+<i>liquid</i>, when broken up by a prism, lies in soft bands
+of color, side by side.</p>
+
+<p>Both of them a good deal like the solar spectrum,
+you will say. Only here are no mysterious dark lines
+crossing the bright bands of color. But how about
+gases? Suppose we have a substance in the state of
+gas or vapor, as almost every known substance might
+be under the requisite conditions, and suppose that
+substance to be heated to a glowing brilliance. Then
+let its light be passed through the slit and prism of a
+spectroscope. What result shall we find this time?
+Entirely different from anything seen before. Instead
+of soft, continuous bands of color, there are <i>bright
+lines</i>, well separated and sharply defined.</p>
+
+<p>How many bright lines? Ah, that depends upon
+which particular gas is having its ray analyzed. Try
+sodium first—one of the commonest of earthly substances.
+Enormous quantities of it are distributed<span class="pagenum" id="Page_350">[Pg 350]</span>
+broadcast in earth and air and water. More than
+two-thirds of the surface of our globe lies under an
+enfolding vesture of water saturated with salt, which
+is a compound of sodium. That is to say, sodium
+enters largely into the make of salt. Every breeze
+which sweeps over the ocean carries salt inland, to
+float through the atmosphere. Sir H. E. Roscoe
+writes: “There is not a speck of dust, or a mote seen
+dancing in the sunbeam, which does not contain chloride
+of sodium”—otherwise salt. The very air which
+surrounds us is full of compounds of sodium, and we
+can not breathe without taking some of it into our bodies.
+Sodium is an “elementary substance.” By which
+I mean that it is one of a number of substances called
+by us “simple,” because chemists have never yet
+succeeded in breaking up those substances, by any
+means at their command, into other and different
+materials.</p>
+
+<p>Iron is, so far as we know, a simple substance. It
+is found as iron in the earth. No chemist has ever
+been able to make iron by combining other materials
+together. No chemist has ever managed to separate
+iron into other materials unlike itself. Iron it is, and
+iron it remains, whether as a solid, as a liquid, or as a
+gas. Gold is another simple substance, and so is silver.
+Sodium is another. All these we know best in the
+solid form. Mercury, another simple substance, we
+know best as a liquid.</p>
+
+<p>Water is not a simple substance; for it can be separated
+into two different gases. Glass is not a simple
+substance; for it is manufactured out of other substances
+combined together.</p>
+
+<p><span class="pagenum" id="Page_351">[Pg 351]</span></p>
+
+<p>We can speak quite positively as to such substances
+as are not simple; but with regard to so-called “elements,”
+we may only venture to assert that, thus far,
+nobody has succeeded in breaking them up. Therefore,
+at least for the present, they are to us “elementary.”</p>
+
+<p>All the simple substances, and very many of the
+combinations of them, though often known to us only
+in the solid form, may, under particular conditions, be
+rendered liquid, and even gaseous. Every metal may
+be either in the solid form, or the liquid form, or the
+vapor form. Iron, as we commonly see it, is solid—in
+other words, it is frozen, like ice. Just as increase
+of warmth will turn ice into water, so a certain amount
+of heat will make solid iron become liquid iron. And
+just as yet greater warmth will turn water into steam,
+so a very much increased amount of heat will turn
+liquid iron into vapor of iron. A little heat will do
+for ice what very great heat will do for iron.</p>
+
+<p>Whether iron and other metals exist in the sun, as
+on earth, in a hard and solid form, it is impossible to
+say. It is only in the form of gas that man can become
+aware of their presence at that distance. The
+intense, glowing, furnace-heat of the sun causes many
+metals to be present in large quantities in the sun’s
+atmosphere in the form of vapor.</p>
+
+<p>Not only have we learned about some of the metals
+in the sun, but this strange spectrum analysis has
+taught us about some of the metals and gases in the
+stars as well. It is found that in Sirius, sodium and
+magnesium, iron and hydrogen, exist. In Vega and
+Pollux there are sodium, magnesium, and iron. In<span class="pagenum" id="Page_352">[Pg 352]</span>
+Aldebaran, these substances and many others, including
+mercury, seem to abound. These are merely a few
+examples among many stars, each being in some degree
+different from the rest.</p>
+
+<p>But how can we know all this? How could the
+wildest guessing reveal to us the fact of iron in the
+sun, not to speak of the stars? We know it by means
+of the spectrum analysis—or, as we may say, by means
+of the spectroscope. This instrument may be looked
+upon as the twin-sister to the telescope. The telescope
+gathers together the scattered rays of light into
+a small spot or focus. The spectroscope tears up these
+rays of light into ribbons, sorts them, sifts them, and
+enables us to read in them hidden meanings.</p>
+
+<p>When a ray of light reaches us from the sun, that
+ray is <i>white</i>; but in the white ray there are bright
+colors concealed. Newton was the first to discover
+that a ray of white light is really a bundle of colored
+rays, so mixed up together as to appear white. If a
+ray of sunlight is allowed to pass through a small
+round hole in a wall, it will fall upon the opposite
+wall in a small round patch of white light. But if a
+<i>prism</i>—a piece of glass cut in a particular shape—is
+put in the path of the ray, it has power to do two
+curious things. First, it bends the ray out of a
+straight course, causing the light to fall upon a different
+part of the wall. Secondly, it breaks up or
+divides the ray of white light into the several rays
+of colored light of which the white ray is really
+composed. This breaking up, or dividing, is called
+“analyzing.”</p>
+
+<p>If in place of a round hole the ray of light is made<span class="pagenum" id="Page_353">[Pg 353]</span>
+to pass through a very narrow slit, it is proved that
+the bright bands of color do not overlap. Instead of
+this, dark lines, or gaps, show here and there. Now,
+these lines or gaps are always to be seen in the spectrum
+or image of bright colors formed by a broken-up
+ray of <i>sunlight</i>. There is always a certain number of
+dark lines in each colored band—some near together,
+some far apart; here one or two, there a great many.
+Where a simple ray of sunlight is concerned, the exact
+arrangement of the lines never changes.</p>
+
+<p>When the stars were examined—when the rays of
+light coming from various stars were split up and
+analyzed—it was found that they too, like the sun,
+gave a spectrum of bright colors with dark lines.
+But the lines were different in number and different
+in arrangement from the sun’s lines. Each star has
+his own particular number and his own particular arrangement,
+and that arrangement and number do not
+change.</p>
+
+<p>If a white-hot metal is burnt, and the light of it as
+it burns is allowed to pass through a prism, a row of
+bright colors appears as in the sun’s spectrum, only
+there are no dark lines. If a gas is burnt, and the
+light is allowed to pass through a prism, no bright
+color-bands appear, and no dark lines either; but instead
+of this, there are <i>bright lines</i>. Each gas or
+vapor has its own number of lines and its own arrangement.
+Sodium shows two bright lines, side by
+side. Iron shows sixty bright lines, arranged in a
+particular way.</p>
+
+<p>Now you see how a row of bright colors without
+bands of color may appear. But what about color-bands<span class="pagenum" id="Page_354">[Pg 354]</span>
+and dark lines together? That discovery came
+latest. It was found that if a white-hot metal were
+burned, and if its light were allowed before touching
+the prism to shine through the flame of a burning gas,
+<i>then</i> there were dark lines showing in the colored
+bands. These dark lines changed in position and
+number and arrangement with each different kind
+of gas, just as the bright lines changed if the gases
+were burned alone. If the light of the burning
+metal passed through a flame colored with gas of
+sodium, two dark lines showed on one part of the
+spectrum; but if it passed through a flame colored
+with vapor of iron, sixty dark lines showed on another
+part of the spectrum.</p>
+
+<p>So now, by means of this spectrum analysis, we
+know with all but certainty that the sun and stars
+are solid, burning bodies, sending their light through
+burning, gas-laden atmospheres. By examining the
+little black lines which appear in the spectrum of one
+or another, it is possible to say the names of many
+metals existing as gas in those far-off heavenly
+bodies. Is not this a wonderful way of reading light?</p>
+
+<p>The split-up rays tell us much more than the kinds
+of metals in different stars. When a nebula is examined,
+and is found to give no spectrum of bright bands
+and dark lines, but only a certain number of bright
+lines, we know it to be formed of gas, unlike stars
+and other nebulæ. Also, it is by means of the spectroscope
+that so much has lately been discovered about
+the motions and speed of the stars coming towards or
+going from us.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_355">[Pg 355]</span></p>
+
+<h2 class="nobreak" id="c31">CHAPTER XXXI.</h2>
+</div>
+
+<p class="c sp">STELLAR PHOTOGRAPHY.</p>
+
+
+<p><span class="smcap large">Photography</span> is not only a useful handmaid to
+astronomy as a whole, but also it is so, peculiarly, to
+that division of astronomy with which we are now
+chiefly concerned—to spectroscopy. A few pages may
+therefore with advantage be given to the subject of
+celestial photography.</p>
+
+<p>Photography is, indeed, the greatest possible help
+to the astronomer. It pictures for him those stars
+which his eyes can see but dimly, or even can not see
+at all; it paints for him those light-rays of which he
+would obtain but a passing glance, and which he
+could not accurately remember in all their details; it
+maps out for him the wide heavens, which he, unaided,
+could never do with anything like equal completeness
+by eye and hand alone.</p>
+
+<p>Only recently a vast photographic map of the
+whole sky was undertaken. About eighteen different
+observatories, in divers parts of the world, divided the
+task among them, stars down to the sixteenth magnitude
+being most carefully registered in a complete
+series of something like fifteen hundred separate photographs.
+The whole result, when finally completed,
+will be a grand achievement of the present century.
+Each individual star, in the entire heavens all around
+our earth, from the first to the sixteenth magnitudes,
+will have its exact position in the sky accurately<span class="pagenum" id="Page_356">[Pg 356]</span>
+known, and the smallest change in the position of anyone
+of those stars may then be detected.</p>
+
+<p>Even in the delicate and abstruse operation earlier
+described, the measurement of star-distances through
+annual parallax, photography again steps in. Dr.
+Pritchard, Savilian professor of Astronomy at Oxford,
+pressed photography into the service of this task also.
+Measurements for parallax were made under his direction
+upon photographic plates—a work of no small
+interest. Here, as elsewhere, peculiar advantages belong
+to the photographic method when it can be followed.
+Its records are lasting, the limited number of
+hours which are fully suitable for direct astronomical
+work may be employed in obtaining those records,
+and in broad daylight the examination of them can be
+carried on.</p>
+
+<p>One very curious use is made of star-photographs,
+more especially of the photographs of unseen stars—that
+is, of stars too distant or too dim to be detected
+by the eye. These photographs, when taken, may
+be afterwards looked into further with a microscope.
+So, first, the far-off, invisible suns of the universe are
+photographed on a prepared plate, with the help of a
+powerful telescope, this being needful to secure sufficient
+starlight; and then the tiny picture of those
+suns is examined more closely with the help of a
+powerful microscope.</p>
+
+<p>Spectroscopy has much to say to us. It tells us
+about the positions of the different stars. It tells us
+about the structure of the stars. It tells us about the
+various classes to which the various stars belong. And
+also it tells us about the motions of the stars—not<span class="pagenum" id="Page_357">[Pg 357]</span>
+mere apparent motions, caused by movements of our
+own earth, but true onward journeyings of the stars
+themselves through the depths of space.</p>
+
+<p>For by means of photography we do not obtain
+simple pictures of the stars themselves <i>only</i>, but pictures
+also of the <i>spectra</i> of the stars. An instrument
+is made uniting the spectroscope with the photographic
+apparatus, and this is called a spectrograph. By its
+means the disintegrated or broken-up star-ray is photographed
+in its broken-up condition, so that an exact
+picture is obtained of the bands and lines characteristic
+of any particular star.</p>
+
+<p>No easy matter, as may be imagined, are these
+spectroscopic observations and these spectroscopic
+photographings of the stars. To bring the image of
+a star exactly opposite a slender opening or slit, perhaps
+only about the <i>three-hundredth part of an inch
+in width</i>, and to keep it there, is a task which might
+well be looked upon as practically impossible.</p>
+
+<p>No sooner is a star found in the field of a telescope
+than it vanishes again. As the astronomer gazes, the
+ground beneath him is ever whirling onward, leaving
+the star behind; and although clockwork apparatus
+in all observatories of any importance is made to
+counteract this motion of the earth, and to keep the
+heavenly object, whether star or moon, or comet,
+within view by following its apparent motion, yet, as
+can easily be imagined, to follow thus the seeming
+motion of a dim star through an opening so minute,
+demands exceeding care and delicacy of adjustment.</p>
+
+<p>It is not indeed, for purposes of analysis, <i>always</i>
+needful to pass the light of a star through a narrow<span class="pagenum" id="Page_358">[Pg 358]</span>
+slit. In the case of a nearer body, such as the sun or
+moon or one of the planets, light flows from all parts
+of the body, one ray crossing another; and for the
+examination of such light, a slit is imperatively
+needed, all side-rays having to be cut off. But the
+whole of the brightest star in the sky is only one
+point of light to us, and a slitless telescope may be
+used with no confused results. Where, however, direct
+comparison is required, the star-lines being made
+to appear, side by side or above and below, with the
+solar spectrum, or with the lines of earthly metals,
+then the slit becomes unavoidable.</p>
+
+<p>By such comparison of the two, side by side—the
+light from an intensely-heated earthly substance and
+the light from a star, the rays of both being broken up
+in the spectroscope—the oneness or difference of lines
+in the rays can be easily made out.</p>
+
+<p>One main difficulty in such observations arises from
+the diminution of starlight, caused by its passage
+through a prism. If a rope of a dozen strands is untwisted,
+each of those strands is far weaker than the
+whole rope was; and each strand of color in the
+twisted rope of light is of necessity much more feeble,
+seen by itself, than the whole white ray seen in one.
+Another difficulty in our country generally is the climate,
+which gives so few days or hours in the year for
+effective work. Yet the full amount accomplished by
+seizing upon every possible opportunity is, in the aggregate,
+astonishing. A third and very pressing difficulty
+attendant upon examination of star-spectra is
+caused by the incessant motion of our air, through
+which, as through a veil, all observations have to be<span class="pagenum" id="Page_359">[Pg 359]</span>
+made. The astronomer can never get away from the
+atmosphere; and unless the air be very still—that is
+to say, as still as it ever can remain—the spectrum-lines
+are so uncertainly seen as to make satisfactory
+results impossible. Dr. Huggins has sometimes
+passed hours in the examination of a single line,
+unable to determine whether or no it precisely coincided
+with the comparison-line of some earthly substance.
+In <i>this</i> matter, no leaping at conclusions is
+admissible.</p>
+
+<p>The photography of stars would be easy enough
+if one could just expose a plate to the shining of the
+star, and there leave it to be impressed—there leave
+the star-ray to sketch slowly its own image. But
+this is hardly possible. The unceasing motion of the
+earth, causing the star perpetually to pass away from
+the telescopic field, and the exceeding narrowness of
+the slit opposite to which the star has to be kept in a
+stationary position, make the most accurate adjustment
+needful.</p>
+
+<p>Clockwork alone can not be trusted. If it could,
+the star and the photographic apparatus might be
+comfortably “fixed,” and left to do their own work.
+Instead of which, while a photograph is proceeding,
+it is desirable that an observer should sit gazing patiently
+at the telescope-tube, where the image of the
+star is seen, ready at any moment to correct by a
+touch the slightest irregularity in the clockwork motion
+of the telescope, and so to prevent a blurred
+and spoilt reproduction of the star, or of its spectrum.</p>
+
+<p>One hour, two hours, three hours, at a stretch, this
+unceasing watchfulness may have to be kept up, and<span class="pagenum" id="Page_360">[Pg 360]</span>
+no small amount of enthusiasm in the cause of
+science is requisite for so monotonous and wearying
+a vigil.</p>
+
+<p>As noted earlier, it has been found possible, if the
+photograph of a star or nebula is not completed in
+one night, to renew the work and carry it on the
+next night, or even for many nights in succession.
+This is especially practicable in spectroscopic photography.</p>
+
+<p>From four to five hours, sometimes from eight to
+ten hours, may be needful before the clear image of
+the star or of its spectrum appears—a dim little star
+probably to us, yet perhaps in reality a splendid sun,
+shedding warmth and light and life upon any number
+of such worlds as ours.</p>
+
+<p>Eight or ten hours of photography at one stretch
+with a star are impossible; for the stars, ever seemingly
+on the move, do not remain long enough in a
+good position. For three to six hours, a telescope
+may be made, by means of its clockwork machinery,
+to keep a star steadily in sight, and all that while
+the photograph is progressing. If further exposure
+is needed, the process has to be resumed the next
+night.</p>
+
+<p>The more one considers the matter, the more
+plainly one perceives how enormously our powers of
+sky-observation are increased by photography. It is
+not only that one photographer, with his apparatus,
+may accomplish in a single night the work of many
+astronomers who have to depend upon the power of
+the eye alone. It is not only that, with the help of
+photography, as much can now be done in a lifetime<span class="pagenum" id="Page_361">[Pg 361]</span>
+as formerly must have occupied many generations. It
+is not only that the photograph, once taken, remains a
+permanent possession, instead of a record, more or less
+imperfect, in which otherwise the astronomer would
+have to trust.</p>
+
+<p>It is not even only that in the photograph details
+come out which could not be detected by the eye, and
+that stars are actually brought to our knowledge which
+no man has ever seen, which perhaps no man ever will
+see from this earth with the assistance of the most
+powerful telescope. For the weak shining, which can
+by no possibility make itself felt by the retina of a
+man’s eye, <i>can</i> slowly impress its picture on the photographic
+plate. Hundreds of stars, thousands of
+stars, utterly invisible to man, have had their photographs
+taken as truly as you have had your photograph
+taken, and by the same process, only it has
+been a longer business.</p>
+
+<p>But in addition to all this, we see reproduced upon
+the plate those ultra-violet and infra-red portions of
+the spectrum of light which but for the handmaid,
+photography, would still be to us as things which
+have no existence. And by means of photography
+we can observe and study in those same unseen portions
+of the spectra, when looking into a ray from sun
+or star, the innumerable dark lines, every one of which
+has its own tale to tell. To these tales we must have
+remained blind and deaf, but for photographic aid to
+our limited powers.</p>
+
+<p>Look at some dim star in the sky, and try how long
+you can gaze without blinking. You will very soon
+find that you have done your best, and that to gaze<span class="pagenum" id="Page_362">[Pg 362]</span>
+longer only means a sense of fatigue in your eyes, a
+growing dimness in the star. How different with the
+photographic plate! There, no exertion is wasted, no
+weariness is felt. Faint though the light may be,
+which travels earthward and falls upon the plate, it is
+all collected, all used.</p>
+
+<p>It is easy to photograph the sun, and this has been
+done. When we come to the moon the operation is
+more difficult on account of the feeble intensity of its
+light, and the difference of tint of the various parts
+of its surface. Skill and perseverance have, however,
+surmounted the greatest difficulties, and now we have
+photographs of the moon enlarged to more than a
+yard in diameter, which show the smallest details
+with a truly admirable clearness.</p>
+
+<p>In the first second of time, your eye receives as
+much light from the star as does the photographic
+plate in the same time. But during the course of
+one hour, the plate receives and stores up about thirty-six
+hundred times as much light as it or you received
+in the first instant. There is the secret of the matter.
+The photographic plate does not only receive, it can
+also keep and treasure up the light, and that our eyes
+are not able to do.</p>
+
+<p>If you magnify the amount received in one hour
+by five or ten, and remember that it is all retained,
+then you will begin to understand how feeble stars,
+unseen by man, should become known to us through
+photography.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_363">[Pg 363]</span></p>
+
+<h2 class="nobreak" id="c32">CHAPTER XXXII.</h2>
+</div>
+
+<p class="c sp">THE DAWN OF ASTRONOMY.</p>
+
+
+<p><span class="smcap large">The</span> beginnings of astronomy lie in the distance of
+earliest historical ages. It is no easy matter to say
+when first, in all probability, this science grew into
+existence. Astronomy was alive before the British
+nation was heard of; before Saxons or Franks had
+sprung into being; before the Roman Empire extended
+its iron rule; before the Grecian Empire began to
+flourish; before the Persian Empire gained power; before
+the yet earlier Assyrian Empire held sway.</p>
+
+<p>Among the ancient Chaldeans were devoted star-gazers—much
+more devoted than the ordinary run of
+educated Anglo-Saxons in this present century. They
+earnestly sought, in the dim light of those ages, to
+decipher the meaning of heaven’s countless lamps.
+We have better instruments, and more practiced modes
+of reasoning; also, we have the collected piles of knowledge
+built up by our forefathers through tens of centuries.
+Yet our search is in essence the same as was
+theirs, to know the truth about the stars: not merely
+to start some attractive theory, and then to prove that
+our theory must be right, because we have been so
+clever as to start it; but to discover that which is in
+those regions of space. No lower aim than this is
+worthy to be called scientific.</p>
+
+<p>Mistakes, of course, are made; how should it be
+otherwise? A man finding his way at night, for the<span class="pagenum" id="Page_364">[Pg 364]</span>
+first time, through a wild and unknown country, will
+almost certainly take some wrong turns before he discovers
+the right road. In astronomy, as in all other
+natural sciences, blunders are a necessity if advance is
+to be made. We have to grope our way to knowledge
+through observation and conjecture; in simpler
+terms, through gazing and guessing. Observation of
+facts leads to conjecture as to the possible causes for
+those facts; and each conjecture is proved by later observation
+to be either right or wrong. If proved to be
+right, it takes its place among accepted truths; if proved
+to be wrong, it is flung aside. Some pet delusions
+die hard, because of people’s love for them.</p>
+
+<p>Astronomy, as an infant science, mixed up with astrology,
+existed in the days when the Pyramids were
+juvenile, and when the Assyrian sculptures were modern.
+How much farther back who shall say? By
+astrology, those who studied the heavens endeavored
+to determine the fate of men and of nations, to predict
+events, and to interpret results. They paid particular
+attention to the aspect of the planets, and the
+general appearance of the firmament.</p>
+
+<p>These observations were at first simple remarks
+made by the shepherds of the Himalayas after sunset
+and before sunrise: The phases of the moon, and diurnal
+retrograde motion of that body with reference to
+the sun and stars; the apparent motion of the starry
+sky accomplished silently above our heads; the movements
+of the beautiful planets through the constellations;
+the shooting star, which seems to fall from the
+heavens; eclipses of the sun and moon, mysterious
+subjects of terror; curious comets, which appear with<span class="pagenum" id="Page_365">[Pg 365]</span>
+disheveled hair in the heights of heaven,—such were
+the first subjects of these old observations made during
+thousands of years.</p>
+
+<p>The ancient Chaldean star-gazers had rivals among
+the early Egyptians; and the Chinese profess to have
+kept actual record of eclipses during between three
+and four thousand years. The earlier records are not
+trustworthy; but of thirty-six eclipses reckoned by
+the Chinese sage, Confucius, no less than thirty-one
+have been proved true by modern astronomers.</p>
+
+<p>We can not name with certainty those people whose
+shepherds first gazed with intelligent eyes upon the
+midnight sky, and noted the steady sweep of stars
+across the firmament—intelligent eyes, that is to say,
+so far as man then knew how to use his eyes intelligently;
+so far as man had begun to note anything in
+nature, to watch, to compare, and to conjecture causes.</p>
+
+<p>In those times, and indeed for long afterwards, men
+thought much more about the “influences” of stars
+upon their own lives, and about supposed prophecies
+of the future to be read in the sky, than about the
+actual physical condition of the stars themselves, or
+the causes and meanings of the various phenomena
+observed in the heavens.</p>
+
+<p>The desire to know, for the pure delight of knowing,
+had perhaps hardly begun to dawn upon the mind
+of man. What people did want to know was what
+might be going to happen to themselves; whether <i>they</i>
+would be happy or unhappy; and the stars were chiefly
+of interest as appearing to tell beforehand of troubles
+or joys to come.</p>
+
+<p>The wisest of men in those times knew less of the<span class="pagenum" id="Page_366">[Pg 366]</span>
+outspread heavens than many a child now knows in
+our public schools. Earth and sky were one vast bewildering
+puzzle. They had to discover everything
+for themselves—how the sun rose each morning and
+set each evening; how the seasons changed in steady
+sequence through the year; how the moon and stars
+journeyed in the night; how the ocean-tides went and
+came; how numberless every-day phenomena took
+place.</p>
+
+<p>In olden days the daily rising and setting of the
+sun was a mystery, accounted for by divers theories,
+none of which were right; and the march of stars
+across the midnight sky was a complete puzzle; and
+an eclipse of sun or moon was a fearful perplexity;
+and the tides of ocean were a great bewilderment.
+These things are mysteries still to barbarous nations;
+but they perplex us no longer, because we have found
+out the mode in which such movements, or appearances
+of movement, are brought about through the action
+of quite natural causes.</p>
+
+<p>As a first step, in earliest times, the journey of the
+sun by day, the journeys of moon and stars by night,
+across the sky, could hardly fail to arrest attention.
+Very early, too, the stars were grouped into constellations,
+definite figures and names being attached to
+each. Many of the constellations are now known to
+us by names which belong to the earliest historic ages.</p>
+
+<p>The stars were known as “fixed,” because they
+continued unchangeably in their relative positions—that
+is, in the position held by each star with respect
+to its neighbor stars—although the whole array of
+them moved nightly in company; constellations rising<span class="pagenum" id="Page_367">[Pg 367]</span>
+and setting at night, as the sun rose and set in the
+day.</p>
+
+<p>Ages may well have passed before the planets were
+recognized as distinct from the fixed stars; ages more
+before any definite plan was noted in their wanderings.
+In the course of time men’s attention was directed
+to these matters; and one fact after another, of
+daily or monthly or yearly occurrence, was observed,
+and commented upon, and became familiar to the
+minds of people. Very slowly the first beginnings of
+systematized knowledge took shape and grew, one
+discovery being made after another, one explanation
+being offered after another, one theory being started
+after another.</p>
+
+<p>But an essential difference existed between the infantine
+science of those primitive days and the matured
+astronomy of these later days. The whole ancient
+science was built upon a huge mistake. Men held, as
+a fact of absolutely unquestionable certainty, that this
+earth of ours—this small whirling globe, less than eight
+thousand miles in diameter—was the center, around
+which sun, moon, and stars all revolved.</p>
+
+<p>The Greek philosopher Thales, who lived about six
+hundred years before Christ, is said to have laid the
+foundations of the Grecian astronomy; and Pythagoras
+is stated to have been one of his disciples.
+Though, in many respects, Thales wandered wide of
+the truth, he yet taught many correct ideas; as, for instance,
+that the stars were made of fire; that the moon
+had all her light from the sun; that the earth was a
+sphere in shape, besides other facts respecting the
+earth’s zones and the sun’s apparent path in the sky.<span class="pagenum" id="Page_368">[Pg 368]</span>
+He was also one of the three ancient astronomers who
+were able to calculate and foretell eclipses.</p>
+
+<p>After him came numerous astronomers, of greater
+or less merit, in the Grecian and in other schools.
+They watched carefully; they discovered many things
+of interest; they held divers theories. But one truth
+never took firm root among them, although several of
+them dimly apprehended it; and this was the very
+foundation-truth, for lack of which they were all going
+hopelessly astray—the simple truth that our earth
+is <i>not</i> the center of the universe, and that our earth
+<i>does</i> move. Yet it is not surprising. No wonder they
+were slow to grasp such a possibility.</p>
+
+<p>Anything more bewildering to the mind of ancient
+man than the thought of a solid, substantial world
+floating in empty space, supported upon nothing, upheld
+by nothing, can hardly be imagined. As yet
+little was known of the controlling laws or forces of
+nature, and that little was with reference only to our
+earth. The very suspicion of gravitation as a universal
+law lay in the far-distant future, waiting for the
+intellect of a Newton to call it out of apparent chaos;
+and the delicate balance of forces, by means of which
+the Solar System may almost be said to exist, could
+not be so much as guessed at.</p>
+
+<p>So men still clung to the thought of earth as the
+center of all things, and still believed in a little sun,
+busily circling round her once in every twenty-four
+hours.</p>
+
+<p>Perhaps the greatest of all ancient astronomers was
+Hipparchus, about 150 B. C., who did more than any
+other in those early times to gather together the scattered<span class="pagenum" id="Page_369">[Pg 369]</span>
+facts of astronomy, and to arrange them into
+one united and orderly whole. He it was who discovered
+the precession of the equinoxes. He studied
+eclipses and the motions of the various planets. He
+made elaborate and valuable astronomical tables and
+star-catalogues; but he, like others, failed to discover
+the gigantic error which lay at the root of the whole
+ancient science.</p>
+
+<p>Despite this great mistake, still persistently believed
+in, and despite the crude notions of early astronomers
+on many points, it is marvelous how much
+they did manage to observe and to learn for themselves,—as
+to the sun and his apparent path, as to
+the moon and her path, as to the five then known
+planets and their paths, as to eclipses and other phenomena.</p>
+
+<p>By all such careful watching, although they to some
+extent missed their aim and fell into mistakes, yet they
+paved a way to later discoveries and to fuller knowledge.
+Their work was not thrown away, their trouble
+was not lost; for out of their very errors grew the fair
+form of truth.</p>
+
+<p>Nearly three hundred years after the time of Hipparchus
+came the famous Ptolemy—famous, not, like
+certain other astronomers, for stupendous genius, or
+for the brilliancy and accuracy of his observations,
+but rather noted for the ingenuity of his explanations,
+and for the adroit manner in which he systematized
+such knowledge, on the subject of the heavenly bodies,
+as was then in the possession of mankind.</p>
+
+<p>Ptolemy’s name is best known in connection with
+what is commonly called “The Ptolemaic System of<span class="pagenum" id="Page_370">[Pg 370]</span>
+the Universe,” and his greatest astronomical work is
+best known as the <i>Almagest</i>.</p>
+
+<p>A great many of Ptolemy’s leading notions, as well
+as the principal mass of facts upon which he worked,
+were doubtless borrowed from Hipparchus. The latter
+is said to have explained the movements of the sun
+and of the moon by means of small epicycles, traveling
+round the earth on circular orbits; and even Hipparchus
+did not originate this fundamental idea of the
+so-called “Ptolemaic System,” which had indeed been
+held by the ancients in much earlier days. Hipparchus
+worked it out to some extent, and Ptolemy carried
+on the process much farther, giving forth the
+system to the world in such wise that ever since it has
+gone by his name.</p>
+
+<p>The theory of cycles and epicycles lasted long—lasted
+from the time of Ptolemy in the second century
+to the time of Copernicus in the sixteenth century, of
+whom we have already spoken.</p>
+
+<p>[For about two thousand years, astronomers observed
+attentively the apparent revolutions of the
+heavenly bodies, and this attentive study gradually
+showed them a large number of irregularities and inexplicable
+complications, until at last they recognized
+that they were deceived as to the earth’s position, in
+the same way that they had been deceived as to its stability.
+The immortal Copernicus, in particular, discussed
+with perseverance the earth’s motion, already
+previously suspected for two thousand years, but always
+rejected by man’s self-love; and when this learned
+Polish canon bid adieu to our world in the year 1543,
+he bequeathed to science his great work, which demonstrated<span class="pagenum" id="Page_371">[Pg 371]</span>
+clearly the long-standing error of mankind.—<i>F.</i>]</p>
+
+<p>The new theory of Copernicus had to make its
+way slowly against the dead weight of unreasoning
+public opinion, and against wrongly-reasoning hierarchical
+opposition. In time, gradually, despite all
+resistance, the truth made its way, and was generally
+received, though not till Galileo had been forced by
+ecclesiastical authority to recant his opinions. All
+the same, Copernicus, Kepler, Galileo, were right;
+public sentiment and the Church were wrong,—the
+earth did move, and was not the fixed universe center,
+and, by and by, those who lived on earth had to
+acknowledge the same.</p>
+
+<p>The succession of these great men is interesting to
+note. Between the two shining lights, Hipparchus
+and Ptolemy, nearly three hundred years intervened.
+But as the history of the world advances, we find
+brilliant scientific minds appearing more quickly, one
+following close upon another, instead of their being
+divided by long intervals of blankness.</p>
+
+<p>Within thirty years from the death of Copernicus,
+were born two mighty men of Science: Kepler, who
+lived till 1630; and Galileo, who lived till 1642, when
+England was plunged in civil strife.</p>
+
+<p>Between Copernicus and Kepler came Tycho Brahe.
+Copernicus was a Roman ecclesiastic, born in Poland.
+Tycho Brahe was a wealthy Danish nobleman, an ardent
+lover of astronomy, and a most patient and accurate
+observer. But Tycho held fast by the old
+astronomy. He was not convinced by the arguments
+of Copernicus. To him, earth was still the motionless<span class="pagenum" id="Page_372">[Pg 372]</span>
+center of all things. He was willing to allow
+that the rest of the planets circled round the sun, as
+an explanation of things which he could not help seeing;
+but the sun itself had still, in Tycho’s imagination,
+to revolve daily, with planets and stars and the
+whole sky, round our earth.</p>
+
+<p>As an explainer of causes, therefore, Tycho rose to
+no lofty heights. The real good which he did was in
+watching and noting actual phenomena, not in trying
+to explain how those phenomena were brought about.
+This was left for one of his young pupils, a sickly German
+lad, named John Kepler.</p>
+
+<p>In later years, Kepler made a grand use of his
+master’s mass of careful and thoroughly dependable
+observations. These had really been gathered together
+by Tycho, with a view of disproving the
+Copernican theory, and of establishing the main features
+of the olden astronomy, with certain improvements.
+But Kepler used the accumulated information
+to disprove the old astronomy, and to establish
+the truth of the new Copernican system which Tycho
+had rejected. He found a vast advantage, ready to
+his hand, in the collection of careful observations systematically
+worked out by Tycho in his observatory
+during many a long year. And Kepler did not fail to
+use his advantage.</p>
+
+<p>The planets still refused, as they always had refused,
+to keep to the paths marked out for them by
+astronomers. Kepler grappled with the difficulty.
+He particularly turned his attention to Mars, that
+near neighbor of ours, in which we are all now so
+much interested. A long series of close observations<span class="pagenum" id="Page_373">[Pg 373]</span>
+of Mars’s movements, made by Tycho in the course
+of many years, lay before him; and he knew that he
+could depend upon the absolute honesty and accuracy
+of Tycho’s work.</p>
+
+<p>With immense labor and immense patience, he
+went into the matter, still clinging to the old idea of
+a circular pathway round the sun. He tried things
+this way and that way. He placed his orbit in imagination
+after one mode and another mode; he conjectured
+various arrangements; he tested and proved
+them in turn, comparing each plan with observations
+made,—and still Mars defied all his efforts; still the
+little world went persistently wrong, traveling contrary
+to every theory.</p>
+
+<p>Thus far, nobody had ever thought of an orbit of
+any other shape than a circle. When a straightforward
+journey round a circle was found impossible,
+then epicycles were introduced to explain the planet’s
+perplexing motions. No one had dreamt of an elliptic
+pathway. But suddenly a gleam of daylight came
+upon this groping in the dark. What if Mars traveled
+round the sun—<i>not</i> in a circle, but in an oval?</p>
+
+<p>Kepler tried this oval and that oval, comparing observations
+past—testing, examining, proving or disproving,
+with unwearied patience. And at length he
+found, beyond dispute, that Mars actually did travel
+round the sun in a yearly pathway, which was shaped,
+not as a circle, but as the kind of oval known as an
+<i>ellipse</i>; and, further, that the sun was not in the exact
+center of this ellipse, but to one side of the center, in
+one of the foci. Kepler’s success in detecting the true
+shape of a planetary orbit is doubtless owing to the fact<span class="pagenum" id="Page_374">[Pg 374]</span>
+that the orbit of Mars makes a wider departure from the
+circular form than any of the other important planets.</p>
+
+<p>One step further would have led Kepler to the
+knowledge that comets also travel in elliptic orbits—only
+in very long and narrow ones generally. But he
+had quite made up his mind that all comets merely
+paid our sun one visit, and never by any chance returned;
+so he did not trouble himself to enter into
+calculations with respect to them. This taking for
+granted of ideas long held was a very common practice
+in those days.</p>
+
+<p>The above wonderful discovery of elliptic orbits, in
+place of circular orbits, was only one among many
+made by the illustrious Kepler—discoveries not carelessly
+hit upon, as one might pick up in the street a
+valuable stone which somebody had dropped, but earnestly
+sought for, and found with toil and diligence,
+as gems are first found in foreign lands, after much
+seeking and long patience. Casual discoveries in
+science are rare. Attainment is far more usually
+made through intense study, through hard work,
+through profound thought, through a gradual groping
+upward out of darkness to the point where daylight
+breaks forth.</p>
+
+<p>The three well-known “Laws of Kepler” still lie
+at the very foundation of the modern system of astronomy.
+They are: First, every planet moves in an
+elliptical orbit, in one focus of which the sun is situated;
+second, the line drawn from the sun to a
+planet moves over equal areas in equal times; and,
+third, the square of the periodic times of the planets
+varies inversely as the cubes of their distances.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_375">[Pg 375]</span></p>
+
+<h2 class="nobreak" id="c33">CHAPTER XXXIII.</h2>
+</div>
+
+<p class="c sp">MODERN ASTRONOMY.</p>
+
+
+<p><span class="smcap large">Still</span>, however, the world was not convinced of
+the truth of the Copernican system. One man here
+or there saw and acknowledged its reality. The mass
+of mankind continued firmly to believe that they
+dwelt at the universe center, and utterly to scout the
+idea of a moving earth. Indeed, it may be very much
+doubted whether, not merely the mass of mankind,
+but even the most civilized and cultivated portion of
+that mass, had as yet, to any wide extent, heard a
+whisper of the new theories. Knowledge, in those
+days, traveled from place to place with exceeding deliberation.</p>
+
+<p>Another great man arose, contemporary with Kepler—a
+man whose story seizes more strongly upon our
+imagination than that of the severe and successful
+studies of Kepler. From an ordinary worldly point of
+view, Kepler would hardly be looked upon as altogether
+a successful man. He was poor, and in sickly health.
+His chief book was promptly prohibited by Rome—then
+a power in the whole reading world of Europe to
+an extent which can hardly be realized in these days
+of freedom. Kepler’s book was placed in the forbidden
+category, side by side with the dying publication
+of Copernicus. This checked all hope of literary
+gains, and life with Kepler was one long struggle.
+But if he could have looked ahead two or three hundred<span class="pagenum" id="Page_376">[Pg 376]</span>
+years; if he could have foreseen the time when
+not a few wise men of science alone, but all the civilized
+world, including the very Church which condemned
+him, should meekly have accepted and indorsed his
+discoveries,—then he would have been able to gauge
+the measure of his own real success.</p>
+
+<p>Moreover, with all his troubles, Kepler was so
+happy as to escape absolute persecution. He lived in
+a country which knew something of liberty as an ideal;
+he was left to write and work freely; and, at least, no
+public recantation of what he held to be truth was
+forced from him.</p>
+
+<p>Galileo’s was a sadder tale. A Florentine of noble
+birth, he turned his attention early to science as the
+needle turns to the north, and before the age of twenty-seven
+he already occupied a foremost position as mathematical
+lecturer at Pisa. There it was that he direfully
+offended the philosophers of the day by proving
+Aristotle to be in the wrong. For Aristotle was the
+great master of the schoolmen. His philosophy and
+theories were accepted as final, and whatsoever could
+not be proved in accordance with them was regarded
+as untrue. Aristotle had declared that if two weights—the
+one being ten times as heavy as the other—were
+dropped together from a height, the heavier weight
+would reach the ground ten times as quickly as the
+lighter.</p>
+
+<p>Everybody believed this, and nobody had ever
+thought of putting it to the test of actual trial. Aristotle
+had said so, and Aristotle was indorsed as a whole
+by all the schools of Europe; and what more could
+possibly be wanted by any reasonable human being?
+<span class="pagenum" id="Page_378">[Pg 378]</span>But Galileo was not so easily satisfied. He looked
+into the matter independently, bent upon finding out,
+not what Aristotle had thought or what the Church
+might support, but simply what actually <i>was</i>.</p>
+
+<div class="figcenter" id="f61">
+<img src="images/fig61.jpg" alt="astronomers">
+<p class="caption"><span class="smcap">Prominent Astronomers of the Nineteenth Century.</span></p>
+</div>
+
+<p>Then, in view of many observers, called together
+for the occasion, he dropped, at the same instant, from
+the top of the leaning tower of Pisa, a shot weighing
+one pound and another shot weighing a hundred
+pounds. And, behold! both reached the ground simultaneously.
+There was not a fraction of difference
+between the two. To prove Aristotle wrong was to
+prove everybody wrong, the authorities of the Church
+included. Men calmly declined to believe their own
+eyes, and Galileo was in very evil odor.</p>
+
+<p>From falling bodies he went on to subjects of yet
+wider interest to people in general. He read about
+and eagerly embraced the Copernican system. Not
+only did he accept it himself, but he vigorously set to
+work to teach and convince others also. This, as
+might only be expected, aroused vehement opposition.
+But Galileo was still in the heyday of his powers, and
+he was not to be easily silenced. In those days he
+could afford to press onward in the teeth of resistance,
+and to laugh at men who would not listen.</p>
+
+<p>When at Venice, a report reached him of a certain
+optician in Holland who had happened to hit upon a
+curious “combination of lenses,” through which objects
+afar off could be actually seen as if they were
+near. Galileo promptly seized upon the notion, and
+within twenty-four hours he had rigged up a small,
+rough telescope out of an old organ-pipe and two
+spectacle-glasses.</p>
+
+<p><span class="pagenum" id="Page_379">[Pg 379]</span></p>
+
+<p>Thus the first telescope was made—a very elementary
+affair, formed of two lenses, convex and concave,
+and capable of magnifying some three times—a
+mere child’s toy compared with telescopes of the
+present day, but of exceeding value and interest, because
+it was the very first; because in all the history
+of the world no telescope had ever been manufactured
+before.</p>
+
+<p>This earliest effort was speedily improved upon.
+The next trial produced a tube which could magnify
+seven or eight times; and in a little while, Galileo
+had a telescope magnifying as much as thirty-two
+times. Even thirty-two times does not sound very
+startling to us; but in those days the revelations of
+such an instrument came upon men like a thunderclap.</p>
+
+<p>Through it could be seen clearly the broken nature
+of the moon’s surface—the craters, the shadows, the
+mountains. Through it could be seen the phases of
+Venus, which no man had ever yet detected, but
+which Copernicus had declared must certainly exist,
+if indeed his system were a reality. Through it could
+be seen four of the moons of Jupiter, and their ceaseless
+journeyings. Through it could be seen spots upon
+the face of the sun, the movements of which showed
+the rotation of the sun upon his axis. Through it
+could be seen the very curious shape of Saturn,
+caused by his rings, though a much stronger power
+was needed to separate the rings from the body of the
+planet.</p>
+
+<p>Of all these discoveries, and many others also made
+by Galileo, none seemed worse to the bigoted schoolmen<span class="pagenum" id="Page_380">[Pg 380]</span>
+of his day than the preposterous notion of black
+spots upon the sun’s face.</p>
+
+<p>Rather curiously, no human being seems ever before
+then to have noticed such spots, though often they
+are quite large enough to be detected by the naked
+eye. A general belief had been held that the sun was
+and must be perfect—an absolutely spotless and unblemished
+being, the purest symbol of celestial incorruptibility—and
+the said discovery went right
+in the teeth of deductions drawn from, and lessons
+founded upon, this belief. Therefore the schoolmen
+held out and determinedly resisted, and would have
+nought to do with Galileo or his telescopes, shutting
+their eyes to marvels newly revealed.</p>
+
+<p>But Kepler was a true scientist, a man who earnestly
+pursued truth, and sought to discover it at any hazard.
+He and Galileo were contemporaries, and they held
+communication on these subjects. Some of Galileo’s
+discoveries went quite as much in the teeth of some
+of Kepler’s most dearly-loved theories as they did in
+the teeth of the schoolmen’s most dearly-loved doctrines.
+Yet, none the less, Kepler welcomed them
+with great delight and eagerness, showing thereby his
+true greatness of character.</p>
+
+<p>Till after the age of fifty, Galileo was allowed to go
+on undisturbed, or at least not materially disturbed,
+by opposition in his career of success—observing,
+learning, theorizing, calculating, explaining, teaching—a
+prominent figure indeed. Not only did he take a
+large share in establishing firmly the Copernican system
+of astronomy, but some of the principal laws of
+motion were discovered by him. He first found the<span class="pagenum" id="Page_381">[Pg 381]</span>
+uses of a pendulum, and there is strong reason for believing
+that the first microscope, as well as the first
+telescope, was from his hands.</p>
+
+<p>But after the age of fifty, reverses came, and one
+blow succeeded another. Rome had been gradually
+waking up to the true sense of all that was implied
+by his discoveries and his teaching, and at length she
+let loose her thunders—impotent thunders enough, so
+far as regarded any permanent checking of the progress
+of truth, but by no means impotent to crush one
+defenseless victim, the champion of scientific truth in
+that country and age.</p>
+
+<p>Years of greater or less opposition, amounting often
+to persecution, were followed by an imperious order
+commanding him to Rome. There he was examined
+and severely “questioned,” and recantation was forced
+from him, worth as much as such forced recantations
+commonly are worth.</p>
+
+<p>Even then he did not cease from the work that he
+loved; even in prison he carried it on; even when he
+might not write, nothing could stop him from thinking.
+But his health was broken; his liberty was taken
+away; illness followed illness; his favorite daughter
+died; his eyesight gradually failed; the last book that
+he wrote might not for a long while be printed; and
+at last he passed away, mercifully set free from those
+who, in an essentially bigoted and intolerant age, were
+incapable of appreciating his greatness.</p>
+
+<p>They would fain <i>then</i> have denied him even a respectable
+grave. Now, all the civilized world unites
+to honor the name of Galileo.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_382">[Pg 382]</span></p>
+
+<h2 class="nobreak" id="c34">CHAPTER XXXIII.</h2>
+</div>
+
+<p class="c sp">ISAAC NEWTON.</p>
+
+
+<p><span class="smcap large">Even</span> the great fame of Galileo must be relegated
+to a second place in comparison with that of the philosopher
+who first saw the light in a Lincolnshire
+farmhouse on the 25th of December, 1642, the very
+same year of Galileo’s death. His father, Isaac Newton,
+had died before his birth. The little Isaac was
+at first so frail and weakly that his life was despaired
+of. The watchful mother, however, tended her delicate
+child with such success that he ultimately acquired
+a frame strong enough to outlast the ordinary
+span of human life.</p>
+
+<p>In due time the boy was sent to the public school
+at Grantham. That he might be near his work, he
+was boarded at the house of Mr. Clark, an apothecary.
+He had at first a very low place in the class. His first
+incentive to diligent study seems to have been derived
+from the circumstance that he was severely kicked by
+one of the boys above him in the class. This indignity
+had the effect of stimulating young Newton’s activity
+to such an extent that he not only attained the
+desired object of passing over the head of the boy
+who had maltreated him, but continued to rise until
+he became the head of the school.</p>
+
+<p>The play-hours of the great philosopher were devoted
+to pursuits very different from those of most
+schoolboys. His chief amusement was found in making<span class="pagenum" id="Page_383">[Pg 383]</span>
+mechanical toys, and various ingenious contrivances.
+He watched, day by day, with great interest,
+the workmen engaged in constructing a windmill in
+the neighborhood of the school, the result, of which
+was that the boy made a working model of the windmill
+and of its machinery, which seems to have been
+much admired as indicating his aptitude for mechanics.
+We are told that he also indulged in somewhat
+higher flights of mechanical enterprise. The first
+philosophical instrument he made was a clock, which
+was actuated by water. He also devoted much attention
+to the construction of paper kites, and his skill in
+this respect was highly appreciated by his schoolfellows.
+Like a true philosopher, even at this stage,
+he experimented on the best methods of attaching the
+string, and on the proportions which the tail ought
+to have.</p>
+
+<p>When the schoolboy at Grantham was fourteen
+years of age, it was thought necessary to recall him
+from the school. His recently-born industry had been
+such that he had already made good progress in his
+studies, and his mother hoped that he would now lay
+aside his books, and those silent meditations to which,
+even at this early age, he had become addicted. It
+was hoped that instead of such pursuits, which were
+deemed quite useless, the boy would enter busily into
+the duties of the farm and the details of a country
+life. But before long it became manifest that the
+study of nature and the pursuit of knowledge had
+such a fascination for the youth that he could give
+little attention to aught else. It was plain that he
+would make but an indifferent farmer. He greatly<span class="pagenum" id="Page_384">[Pg 384]</span>
+preferred experimenting on water-wheels, and working
+at mathematics in the shadow of a hedge.</p>
+
+<p>Fortunately for humanity, his mother, like a wise
+woman, determined to let her boy’s genius have the
+scope which it required. He was accordingly sent
+back to Grantham school, with the object of being
+trained in the knowledge which would fit him for entering
+the University of Cambridge.</p>
+
+<p>It was the 5th of June, 1660, when Isaac Newton,
+a youth of eighteen, was enrolled as an undergraduate
+of Trinity College, Cambridge. Little did those who
+sent him there dream that this boy was destined to be
+the most illustrious student who ever entered the portals
+of that great seat of learning. Little could the
+youth himself have foreseen that the rooms near the
+gateway which he occupied would acquire a celebrity
+from the fact that he dwelt in them, or that the antechapel
+of his college was in good time to be adorned
+by that noble statue of himself which is regarded as
+the chief art treasure of Cambridge University, both
+on account of its intrinsic beauty and the fact that it
+commemorates the fame of her most distinguished
+alumnus, Isaac Newton, the immortal astronomer. His
+advent at the university seemed to have been by no
+means auspicious or brilliant. His birth was, as we have
+seen, comparatively obscure, and though he had already
+given indication of his capacity for reflecting on philosophical
+matters, yet he seems to have been but ill-equipped
+with the routine knowledge which youths are
+generally expected to take with them to the universities.</p>
+
+<p>From the outset of his college career, Newton’s attention
+seems to have been mainly directed to mathematics.<span class="pagenum" id="Page_385">[Pg 385]</span>
+Here he began to give evidence of that marvelous
+insight into the deep secrets of nature which,
+more than a century later, led so dispassionate a judge
+as Laplace to pronounce Newton’s immortal work as
+pre-eminent above all the productions of the human
+intellect. But though Newton was one of the very
+greatest mathematicians that ever lived, he was never
+a mathematician for the mere sake of mathematics.
+He employed his mathematics as an instrument for
+discovering the laws of nature.</p>
+
+<p>His industry and genius soon brought him under
+the notice of the university authorities. It is stated
+in the university records that he obtained a scholarship
+in 1664. Two years later we find that Newton,
+as well as many residents in the university, had to
+leave Cambridge temporarily on account of the breaking
+out of the plague. The philosopher retired for a
+season to his old home at Woolsthorpe, and there he
+remained until he was appointed a Fellow of Trinity
+College, Cambridge, in 1667. From this time onwards,
+Newton’s reputation as a mathematician and
+as a natural philosopher steadily advanced, so that in
+1669, while still but twenty-seven years of age, he
+was appointed to the distinguished position of professor
+of Mathematics at Cambridge. Here he found
+the opportunity to continue and develop that marvelous
+career of discovery which formed his life’s work.</p>
+
+<p>The earliest of Newton’s great achievements in
+natural philosophy was his detection of the composite
+character of light. That a beam of ordinary sunlight
+is, in fact, a mixture of a very great number of
+different colored lights, is a doctrine now familiar to<span class="pagenum" id="Page_386">[Pg 386]</span>
+every one who has the slightest education in physical
+science. We must, however, remember that this discovery
+was really a tremendous advance in knowledge
+at the time when Newton announced it.</p>
+
+<div class="figcenter" id="f62">
+<img src="images/fig62.jpg" alt="newton">
+<p class="caption">SIR ISAAC NEWTON.</p>
+</div>
+
+<p>A certain story is often told about Newton. It is
+said that as he sat in a garden an apple fell from a
+tree, and that its fall set him thinking, and that, in
+consequence of this train of thought, he found out all
+about the law of attraction or gravitation.</p>
+
+<p>But the fall of an apple could not possibly have set
+Newton thinking, because he had already been thinking<span class="pagenum" id="Page_387">[Pg 387]</span>
+long and hard upon these difficult questions. Indeed,
+it was <i>because</i> he had been so thinking, <i>because</i>
+his mind was in a watchful and receptive condition,
+that so slight a matter as a falling apple should, perhaps,
+have suggested to him a useful train of ideas.</p>
+
+<p>Newton was a man who really did think, and who
+really did think intensely. He was not, like the ordinary
+run of people, one who merely had a good
+many notions walking loosely through his brain. He
+would bend his mind to a subject and be absolutely
+absorbed in it; later in life so absorbed that he would
+forget to finish his dressing, and would be unable to
+say whether or no he had dined. This sort of forgetfulness
+does sometimes spring from vacancy of mind;
+but with Newton it arose from fullness of thought.</p>
+
+<p>An apple falls, of course, as a stone or any other
+body falls, because the earth attracts it. Otherwise,
+it might as easily rise and float away into the sky.
+But this was known perfectly well long before Newton’s
+days. It was clearly understood that the earth
+had a curious power of drawing all things towards
+herself. People could not explain why or how it was
+so; neither can we explain now; but they were fully
+aware of the fact.</p>
+
+<p>So men knew something of the force called gravity;
+but they knew it mainly, almost exclusively, as
+having to do with our earth, and with the things upon
+our earth. They had not begun definitely to think of
+gravity as having to do with bodies in the heavens;
+as being a chief controlling force in the whole Solar
+System; much less as reigning throughout the vast
+universe of stars. It had not come into their minds<span class="pagenum" id="Page_388">[Pg 388]</span>
+with any distinctness that, just as the earth pulls towards
+her own center a mountain, a horse, a man, so
+the sun pulls toward his center the earth, the moon,
+and all the planets.</p>
+
+<p>Certain glimmerings of the notion had, indeed,
+begun to dawn on the horizon of learning. Horrocks,
+Borelli, Robert Hook, Wren, Halley, and others had
+<i>glimpses</i> of universal gravitation; but only glimpses.
+A gifted English philosopher, late in the sixteenth century,
+Gilbert by name, went so far as to speak of earth
+and moon acting one upon the other “like two magnets.”
+He also saw the effect of the moon’s attraction
+in bringing about ocean tides, though he oddly explained
+that the said attraction was not so much exerted
+upon ocean waters as upon “subterranean spirits
+and humors”—whatever he may have meant by such
+an expression.</p>
+
+<p>Kepler, not long after Gilbert, made further advance.
+He gained some definite notions as to the nature
+of gravity; and he saw distinctly that the moon’s
+attraction was the main cause of the tides. The following
+remarkable statement is found in his writings:
+“If the earth ceased to attract its waters, the whole
+sea would mount up and unite itself with the moon.
+The sphere of the attracting force of the moon extends
+even to the earth, and draws the waters towards
+the torrid zone, so that they rise to the point which
+has the moon in the zenith.” Here is a distinct enough
+grasp of the fact that gravity can and does act through
+distance, between worlds separated by thousands of
+miles.</p>
+
+<p>Yet, though both Gilbert and Kepler saw so much,<span class="pagenum" id="Page_389">[Pg 389]</span>
+they failed to go farther. Neither of the two had any
+clear knowledge of the modes in which gravitation
+acts, or of the laws which govern its working. Gilbert
+and Kepler alike, while dimly recognizing, not
+only the moon’s attraction for earth’s oceans, but the
+mutual attraction of earth and moon each for the other,
+were utterly perplexed as to what force could possibly
+hold the two bodies asunder. Gilbert could seriously
+talk of “subterranean spirits and humors.”
+Kepler could soberly write of an “animal force” or
+some tantamount power in the moon, which prevented
+her nearer approach to earth.</p>
+
+<p>Galileo was equally vague on the subject. With all
+his brilliant gifts, and while acknowledging the earth’s
+attractive power over the moon, he would not even
+admit the existence of <i>mutual</i> attraction, and talked
+of the moon as being compelled to “follow the earth.”
+Unquestionably there are times when the moon does
+follow the earth, and that is when the earth happens
+to go before. But quite as often it happens that the
+moon goes before, and the earth follows after.</p>
+
+<p>All these great men were groping near the truth,
+yet none managed to find the clue that was wanted.
+They left the unfinished process of thought to be carried
+on by the master-mind of Newton. And Newton
+set himself to think the question out. He used Kepler’s
+observations. He sought to penetrate the secrets
+of a Solar System in mysterious and inviolable order.
+Some reason or cause for that order he knew must exist—if
+only it might be grasped! He pondered deeply;
+lost in profound cogitation, through stormy days of
+civil strife, of plague and loss and suffering. The<span class="pagenum" id="Page_390">[Pg 390]</span>
+object of his life was to discover, if so he might, what
+power or what forces retained the different worlds in
+their respective pathways; in short, what manner of
+celestial guidance was vouchsafed to the planets.</p>
+
+<p>For although men had now learned the shape of the
+planet-orbits, and even knew certain laws which helped
+to govern the planet-motions, they had not discovered
+one supreme controlling law. They did not dream of
+gravity in the heavens as a prevailing force. There
+was absolutely no reason, with which men were acquainted,
+why each planet should preserve its own
+particular distance from the sun; why Mars should not
+wander as far away as Jupiter; why Mercury should
+not flee to the position of Saturn; why our own
+earth should be always about as near as she always
+is.</p>
+
+<p>The resources of Newton’s genius seemed equal to
+almost any demand that could be made upon it. He
+saw that each planet must disturb the other, and in
+that way he was able to render a satisfactory account
+of certain phenomena which had perplexed all preceding
+investigators. That mysterious movement by
+which the pole of the earth sways about among the
+stars, had been long an unsolved enigma; but Newton
+showed that the moon grasped with its attraction
+the protuberant mass at the equatorial regions of the
+earth, and thus tilted the earth’s axis in a way that
+accounted for the phenomenon which had been known,
+but had never been explained, for two thousand years.
+All these discoveries were brought together in that
+immortal work, Newton’s “Principia,” the greatest
+work on science that the world had yet seen.</p>
+
+<p><span class="pagenum" id="Page_391">[Pg 391]</span></p>
+
+<p>It may well be that, as Newton pondered this perplexing
+question while seated in the garden, an apple
+dropping to the ground might have sufficed to turn his
+wide-awake and ready mind in the direction of that
+familiar force, gravity, which draws all loose bodies towards
+earth’s surface. The apple fell because of gravity.
+Quite naturally the question might have arisen
+in Newton’s mind—“Why not this same gravity in the
+heavens also? If the earth draws an apple towards
+herself, why should not the earth draw the moon?
+Why should not the sun draw the earth? Nay, more,
+why should not the sun draw all the planets?” Newton
+set himself to work out this problem, allowing for the
+distance of the moon from earth, and for the bulk and
+weight of both earth and moon.</p>
+
+<p>And because the answer was <i>not</i> precisely what he
+had looked for, he put the calculation aside, and
+waited for years. It seems that he mentioned his conjecture
+to no living person. After many years he took
+it up again, and worked it out afresh. By this time
+new measurements of earth’s surface, and new calculations
+of earth’s size had been made, and Newton had
+fresh figures to go upon. This time the answer came
+just as he had originally hoped, and the truth of his
+surmise was thus proved.</p>
+
+<p>Gravity held the moon near the earth, preventing
+her from wandering off into unknown distances. Gravity
+held earth and moon, Mars, Venus, Jupiter, each
+planet, in its own pathway, within a certain distance
+of the sun. Gravity held many of the comets as permanent
+members of the Solar System. So strong,
+indeed, was the drawing of gravity found to be, that<span class="pagenum" id="Page_392">[Pg 392]</span>
+only the resisting force of each bright world’s rapid
+rush round the sun could keep the sun and his planets
+apart.</p>
+
+<p>Newton had discovered the long-sought secret. He
+had found that “every particle of matter in the universe
+attracts every other particle?” He had found
+also the main laws which govern the working of that
+attraction—that it depends, first, upon the mass or
+amount of “matter” in each body; that it depends,
+secondly, upon the distance of one body from another.
+He found, too, how far attraction increases with greater
+nearness, and decreases with greater distance. All
+these and countless other questions he worked out in
+the course of years. But first he had grasped the
+great leading principle, after which men had until then
+groped in vain, that by the force of gravity the sun
+and his worlds and their moons are all bound together
+into one large united family or system.</p>
+
+<p>Though Newton lived long enough to receive the
+honor that his astonishing discoveries so justly merited,
+and though for many years of his life his renown
+was much greater than that of any of his contemporaries,
+yet it is not too much to say that, in the years
+which have since elapsed, Newton’s fame has been
+ever steadily advancing.</p>
+
+<p>We hardly know whether to admire more the sublime
+discoveries at which he arrived, or the extraordinary
+character of the intellectual processes by which
+those discoveries were reached. He died on Monday,
+March 20, 1727, in the eighty-fifth year of his age.</p>
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_393">[Pg 393]</span></p>
+
+<h2 class="nobreak" id="c35">CHAPTER XXXV.</h2>
+</div>
+
+<p class="c sp">LATER ASTRONOMY.</p>
+
+
+<p><span class="smcap large">Sir William Herschel</span> was born in the city of
+Hanover, November 15, 1738. He was the second
+son of Isaac Herschel, a musician, who brought him
+up, with his four other sons, to his own profession.</p>
+
+<p>A faithful chronicler has given us an interesting account
+of the way in which Isaac Herschel educated
+his boys; the narrative is taken from the recollections
+of one who, at the time, was a little girl of five or six
+years old. She writes:</p>
+
+<p>“My brothers were often introduced as solo performers
+and assistants in the orchestra at the court,
+and I remember that I was frequently prevented from
+going to sleep by the lively criticisms on music on
+coming from a concert. Often I would keep myself
+awake that I might listen to their animated remarks,
+for it made me happy to see them so happy. But
+generally their conversation would branch out on
+philosophical subjects, when my brother William and
+my father often argued with such warmth that my
+mother’s interference became necessary when the
+names Euler, Leibnitz, and Newton sounded rather
+too loud for the repose of her little ones, who had to
+be at school by seven in the morning.”</p>
+
+<p>The child, whose reminiscences are here given, became
+afterwards the famous Caroline Herschel. The
+narrative of her life is a most interesting book, not<span class="pagenum" id="Page_394">[Pg 394]</span>
+only for the account it contains of the remarkable
+woman herself, but also because it presents the best
+picture we have of the great astronomer, to whom
+Caroline devoted her life.</p>
+
+<p>This modest family circle was, in a measure, dispersed
+at the outbreak of the Seven Years’ War in
+1756. The French proceeded to invade Hanover,
+which, it will be remembered, belonged at this time
+to the British dominions. Young William Herschel
+had already obtained the position of a regular performer
+in the regimental band of the Hanoverian
+Guards, and it was his fortune to obtain some experience
+of actual warfare in the disastrous battle of
+Hastenbeck. He was not wounded, but he had to
+spend the night after the battle in a ditch, and his
+meditations on the occasion convinced him that soldiering
+was not the profession exactly suited to his
+tastes. He left his regiment by the very simple, but
+somewhat risky, process of desertion. He had, it
+would seem, to adopt disguises in order to effect his
+escape. By some means he succeeded in eluding detection,
+and reached England in safety.</p>
+
+<p>The young musician must have had some difficulty
+in providing for his maintenance during the first few
+years of his abode in England.</p>
+
+<p>It was not until he had reached the age of twenty-two
+that he succeeded in obtaining any regular appointment.
+He was then made instructor of music to the
+Durham Militia. Shortly afterwards, his talents being
+more widely recognized, he was appointed as organist
+of the parish Church at Halifax.</p>
+
+<p>In 1766 we find that Herschel had received the<span class="pagenum" id="Page_395">[Pg 395]</span>
+further promotion of organist in the Octagon Chapel,
+at Bath. Bath was then, as now, a highly fashionable
+resort, and many notable personages patronized the
+rising musician. Herschel had other points in his
+favor besides his professional skill; his appearance was
+striking, his address superb, and his conversation animated,
+interesting, and instructive; and even his nationality
+was a distinct advantage, inasmuch as he
+was a Hanoverian in the reign of King George the
+Third. From his earliest youth, Herschel had been endowed
+with that invaluable characteristic, an intense
+desire for knowledge. He naturally wished to perfect
+himself in the theory of music, and thus he was
+led to study mathematics. When he had once tasted
+the charms of mathematics, he saw vast regions of
+knowledge unfolded before him, and in this way he
+was induced to direct his attention to astronomy.
+More and more this pursuit engrossed his attention
+until, at last, it had become an absorbing passion.</p>
+
+<p>It was with quite a small telescope, which had been
+lent him by a friend, that Herschel commenced his
+career as an observer. However, he speedily discovered
+that to see all he wanted to see, a telescope of
+far greater power would be necessary.</p>
+
+<p>He commissioned a friend to procure for him in
+London a telescope with high magnifying power.
+Fortunately for science the price was so great that it
+precluded the purchase, and he set himself at work to
+construct one. After many trials he succeeded in making
+a reflecting instrument of five feet focal length,
+with which he was able to observe the rings of Saturn
+and the satellites of Jupiter.</p>
+
+<p><span class="pagenum" id="Page_396">[Pg 396]</span></p>
+
+<p>It was in 1774, when the astronomer was thirty-six
+years old, that he obtained his first glimpse of the
+stars with an instrument of his own construction.
+Night after night, as soon as his musical labors were
+ended, his telescopes were brought out.</p>
+
+<p>His sister Caroline, who occupies such a distinct
+place in scientific history, the same little girl to whom
+we have already referred, was his able assistant,
+and when mathematical work had to be done, she
+was ready for it. She had taught herself sufficiently
+to enable her to perform the kind of calculations—not,
+perhaps, very difficult ones—that Herschel’s work required;
+indeed, it is not much to say that the mighty
+life-work which this man was enabled to perform
+could never have been accomplished had it not been for
+the self-sacrifice of this ever-loving and faithful sister.</p>
+
+<p>It was not until 1782 that the great achievement
+took place by which Herschel at once sprang into
+fame. He appears to have formed a project for making
+a close examination of all the stars above a certain
+magnitude for the purpose of discovering, if possible,
+a parallax among them. Star after star was brought
+to the center of the field of view of his telescope, and
+after being carefully examined, was then displaced,
+while another star was brought forward to be submitted
+to the same process.</p>
+
+<p>In the great review which Herschel undertook, he
+doubtless examined hundreds, or perhaps thousands of
+stars, allowing them to pass away without note or comment.
+But on an ever-memorable night in March, 1782,
+it happened that he was pursuing his task among the
+stars in the constellation of Gemini. One star was<span class="pagenum" id="Page_397">[Pg 397]</span>
+noticed which, to Herschel’s acute vision, seemed different
+from the stars which in so many thousands are
+strewn over the sky. There was something in the
+starlike object that immediately arrested his attention,
+and made him apply to it a higher magnifying power.
+This at once disclosed the fact that the object possessed
+a disk—that is, a definite, measurable size—and
+that it was thus totally different from any of the hundreds
+and thousands of stars which exist elsewhere in
+space. The organist at the Octagon Chapel at Bath
+had discovered a new planet with his home-made
+telescope. Great was the astonishment of the scientific
+world when the Bath organist announced that the
+five planets, which had been known from all antiquity,
+must now admit the company of a sixth.</p>
+
+<p>The now great astronomer was invited to Windsor,
+and to bring his famous telescope in order to exhibit
+the planet to George III, and to tell his majesty all
+about it. The king took so great a fancy to Herschel
+that he proposed to confer on him the title of “his
+majesty’s own astronomer,” to assign him a residence
+near Windsor, to provide him with a salary, and to
+furnish such funds as might be required for the erection
+of great telescopes, and for the conduct of that
+mighty scheme of celestial observation on which Herschel
+was so eager to enter.</p>
+
+<p>No single discovery of Herschel’s later years was,
+however, of the same momentous description as that
+which first brought him to fame. There is no separate
+collection of his writings, and very scanty accounts
+of his life have been published; but he who has
+written his name among the stars needs no other<span class="pagenum" id="Page_398">[Pg 398]</span>
+testimonial to his fame. Prior to his time the number
+of bodies known as belonging to the Solar System
+was eighteen, including secondary planets and
+Halley’s comet. To these he added nine; namely,
+Uranus and six satellites, and two satellites of Saturn.</p>
+
+<p>Though no additional honors could add to his fame,
+Dr. Herschel, in 1816, received the decoration of the
+Guelphic Order of Knighthood. In 1820 he was elected
+president of the Astronomical Society, and among their
+Transactions, the next year, he published an interesting
+memoir on the places of one hundred and forty-five
+double-stars. This paper was the last which he
+lived to publish. His health had begun to decline,
+and on the 24th of August, 1822, he sank under the
+infirmities of age, having completed his eighty-fourth
+year. He was survived by his widow, Lady Herschel,
+an only son, Sir John F. W. Herschel, and his sister
+Caroline, who died in 1847, in her ninety-eighth year.</p>
+
+
+<p class="c large"><span class="smcap">Laplace.</span></p>
+
+<p>The author of “Celestial Mechanics” was born at
+Beaumont-en-Auge in 1749, just thirteen years later
+than his renowned friend Lagrange. His father was
+a farmer, but appears to have been in a position to
+provide a good education for a son who seemed promising.
+The subject which first claimed his attention
+was theology. He was, however, soon introduced to
+the study of mathematics, in which he presently became
+so proficient that, while he was still no more
+than eighteen years old, he obtained employment as a
+mathematical teacher in his native town.</p>
+
+<p>Desiring wider opportunities for study, young Laplace<span class="pagenum" id="Page_399">[Pg 399]</span>
+started for Paris, being provided with letters of
+introduction to D’Alembert, who then occupied the
+most prominent positions as a mathematician in
+France, if not in Europe. On presenting these letters,
+he seems to have had no reply; whereupon, Laplace
+wrote to D’Alembert, submitting a discussion of
+some point in dynamics.</p>
+
+<p>This letter instantly produced the desired effect.
+D’Alembert thought that such mathematical talent as
+the young man displayed was in itself the best of introductions
+to his favor. It could not be overlooked,
+and accordingly he invited Laplace to come and see
+him. Laplace, of course, presented himself, and erelong
+D’Alembert obtained for the rising philosopher
+a professorship of Mathematics in the military school
+in Paris. This gave the brilliant young mathematician
+the opening for which he sought, and he quickly
+availed himself of it.</p>
+
+<p>Laplace’s most famous work is “Celestial Mechanics,”
+in which he essayed a comprehensive attempt to
+carry out, in much greater detail, the principles which
+Newton had laid down. The fact was that Newton
+had not only to construct the theory of gravitation,
+but he had to invent the mathematical processes by
+which his theory could be applied to the explanation
+of the movements of the heavenly bodies. In the
+course of the century which had elapsed between the
+time of Newton and the time of Laplace, mathematics
+had been extensively developed. The disturbances
+which one planet exercises upon the rest can only be
+fully ascertained by the aid of long calculations, and
+for these calculations analytical methods are required.</p>
+
+<p><span class="pagenum" id="Page_400">[Pg 400]</span></p>
+
+<p>With an armament of mathematical methods
+which had been perfected since the days of Newton
+by the labors of two or three generations of mathematical
+inventors, Laplace essayed in his “Celestial
+Mechanics” to unravel the mysteries of the heavens.
+It will hardly be disputed that the book which he has
+produced is one of the most difficult books to understand
+that has ever been written. The investigations
+of Laplace are, generally speaking, of too technical a
+character to make it possible to set forth any account
+of them in such a work as the present. He did, however,
+publish one treatise, called the “System of the
+Universe,” in which, without introducing mathematical
+symbols, he was able to give a general account of the
+theories of the celestial movements, and of the discoveries
+to which he and others had been led. In this
+work Laplace laid down the principles of the nebular
+theory, which, in modern days, has been generally
+accepted.</p>
+
+<p>The nebular theory gives a physical account of the
+origin of the Solar System, and has already been explained
+in this volume. Bach advance in science
+seems to make it more certain that this hypothesis
+substantially represents the way in which our Solar
+System has grown to its present form.</p>
+
+<p>Not satisfied with a career which was merely scientific,
+Laplace sought to connect himself with public
+affairs. Napoleon appreciated his genius, and desired
+to enlist him in the service of the state. Laplace was
+appointed to the office of minister of the interior. The
+experiment was not successful, for he was not by nature
+a statesman. In despair of Laplace’s capacity as<span class="pagenum" id="Page_401">[Pg 401]</span>
+an administrator, Napoleon declared that he carried
+the spirit of his infinitesimal calculus into the management
+of business. Indeed, Laplace’s political conduct
+hardly admits of much defense. While he accepted
+the honors which Napoleon showered on him
+in the time of his prosperity, he seems to have forgotten
+all this when Napoleon could no longer render him
+service. Laplace was made a marquis by Louis XVIII.
+During the latter part of his life the philosopher lived
+in a retired country-place at Arcueile. Here he pursued
+his studies, and, by strict abstemiousness, preserved
+himself from many of the infirmities of old age.</p>
+
+<p>He was endowed with remarkable scientific sagacity;
+but above all his powers his wonderful memory
+shone pre-eminent. His “Celestial Mechanics” is,
+next to Newton’s “Principia,” the greatest of astronomical
+works.</p>
+
+<p>He died on March 5, 1827, in his seventy-eighth
+year, his last words being, “What we know is but little,
+what we do not know is immense.”</p>
+
+
+<p class="c large"><span class="smcap">Leverrier.</span></p>
+
+<p>We are apt to identify the idea of an astronomer
+with that of a man who looks through a telescope at
+the stars; but the word astronomer has really a much
+wider significance. No man who ever lived has been
+more entitled to be designated an astronomer than
+Urbain Jean Joseph Leverrier, and yet it is certain
+that he never made a telescopic discovery of any kind.
+In mathematics, however, he excelled, and he simply
+used the observations of others as the basis of his calculations.</p>
+
+<p><span class="pagenum" id="Page_402">[Pg 402]</span></p>
+
+<p>These observations form, as it were, the raw material
+on which the mathematician exercises his skill.
+It is for him to elicit from the observed places the
+true laws which govern the movements of the heavenly
+bodies. Here is indeed a task in which the
+highest powers of the human intellect may be worthily
+employed. To Leverrier it has been given to provide
+a superb illustration of the success with which
+the mind of man can penetrate the deep things of
+nature.</p>
+
+<p>The illustrious Frenchman was born on the 11th of
+March, 1811, at Saint-Lô, in the department of Manche.
+In the famous polytechnic school for education in the
+higher branches of science he acquired considerable
+fame as a mathematician. His labors at school had
+revealed to Leverrier that he was endowed with the
+powers requisite for dealing with the subtlest instruments
+of mathematical analysis. When he was
+twenty-eight years old his first great astronomical investigation
+was brought forth. This was the profound
+calculation of the disturbances of the planet
+Uranus and the causes of them.</p>
+
+<p>The talent which his researches displayed brought
+Leverrier into notice. At that time the Paris Observatory
+was presided over by Arago, a savant who
+occupies a distinguished position in French scientific
+annals. Arago at once perceived that Leverrier possessed
+the qualifications suitable for undertaking a
+problem of great importance and difficulty that had
+begun to force itself on the attention of astronomers.
+What this great problem was, and how astonishing was
+the solution it received, must now be considered.</p>
+
+<p><span class="pagenum" id="Page_403">[Pg 403]</span></p>
+
+<p>Ever since Herschel brought himself into fame by
+the discovery of Uranus, the movements of this new
+addition to the Solar System had been scrutinized
+with care and attention. The position of Uranus was
+thus accurately determined from time to time. When
+due allowance was made for whatever influence the
+attraction of Jupiter and Saturn and all the other planets
+could possibly produce, the movements of Uranus
+were still inexplicable. It was perfectly obvious that
+there must be some other influence at work besides
+that which could be attributed to the planets already
+known.</p>
+
+<p>Astronomers could only recognize one solution of
+such a difficulty. It was impossible to doubt that
+there must be some other planet in addition to the
+bodies at that time known, and that the perturbations
+of Uranus, hitherto unaccounted for, were due to the
+disturbances caused by the action of this unknown
+planet. Arago urged Leverrier to undertake the great
+problem of searching for this body. But the conditions
+of the search were such that it must be conducted
+on principles wholly different from any search
+which had ever before been undertaken for a celestial
+object. For this was not a case in which mere survey
+with a telescope might be expected to lead to the discovery.</p>
+
+<p>There are in the heavens many millions of stars,
+and the problem of identifying the planet, if indeed it
+should lie among these stars, seemed a very complex
+matter. Of course, it is the abundant presence of the
+stars which causes the difficulty.</p>
+
+<p>The materials available to the mathematician for<span class="pagenum" id="Page_404">[Pg 404]</span>
+the solution of this problem were to be derived solely
+from the discrepancies between the calculated places
+in which Uranus should be found, taking into account
+the known causes of disturbances, and the actual
+places in which observation had shown the planet to
+exist. Here was, indeed, an unprecedented problem,
+and one of extraordinary difficulty. Leverrier, however,
+faced it, and, to the astonishment of the world,
+succeeded in carrying it through to a brilliant solution.</p>
+
+<p>After many trials, Leverrier ascertained that, by
+assuming a certain size, shape, and position for the
+unknown planet’s orbit, and a certain value for the
+mass of the hypothetical body, it would be possible to
+account for the observed disturbances of Uranus.
+Gradually it became clear to his perception, not only
+that the difficulties in the movements of Uranus
+could be thus explained, but that no other explanation
+need be sought for. And now for an episode in
+this history which will be celebrated so long as science
+shall endure. It is nothing less than the telescopic
+confirmation of the existence of this new planet,
+which had previously been indicated only by mathematical
+calculation.</p>
+
+<p>Great indeed was the admiration of the scientific
+world at this superb triumph. Here was a mighty
+planet, whose very existence was revealed by the indications
+afforded by refined mathematical calculation.
+At once the name of Leverrier, already known to
+those conversant with the more profound branches of
+astronomy, became everywhere celebrated.</p>
+
+<p>When, in 1854, Arago’s place had to be filled at<span class="pagenum" id="Page_405">[Pg 405]</span>
+the head of the great Paris Observatory, it was universally
+felt that the discoverer of Neptune was the
+suitable man to assume the office. Leverrier died on
+Sunday, September 23, 1877, in his sixty-seventh year.</p>
+
+<p class="gtb">******</p>
+
+<p><span class="smcap large">Frederick William Bessel</span> was born at Minden
+in 1784, and early turned his attention to mathematical
+subjects. He devoted himself with ardor to astronomy,
+and in 1804 he undertook the reduction of the
+observations made on the comet of 1607. His results
+were communicated to Olbers, who warmly praised
+the young astronomer, and in 1806 recommended him
+to Schroeter as an assistant in the observatory of Lilienthal.
+In 1810 he was appointed director of the
+new observatory then being founded by the king at
+Königsberg. He was admirably fitted for this post,
+and is distinguished mainly for his discovery of the
+parallax of the star 61 Cygni, which he accomplished
+by methods of extreme ingenuity and delicacy.</p>
+
+<p>Two kinds of telescopes are commonly used, the
+refractor and the reflector. The first telescopes made
+were all refractors, and the very first of them was
+made, as you know, by Galileo. The first reflector
+was made in later days by Sir Isaac Newton.</p>
+
+<p>In a refractor the rays of light, from a star or any
+other bright body, reach first a large object-glass,
+through which they pass, and by which, as they pass,
+they are caused to converge, narrowing to a focus or
+point. From this point they widen slightly on their
+way to the eye-piece. After passing through the eye-piece,
+by which they are once more straightened into
+parallel rays, they arrive at the eye.</p>
+
+<p><span class="pagenum" id="Page_406">[Pg 406]</span></p>
+
+<p>Speaking broadly, the eye receives—actually sees—nearly
+as much of the starlight as if its pupil were
+the full size of the object-glass of that telescope, and
+the power of such an instrument depends upon the
+size of the object-glass. A refractor has been made
+with an object-glass forty inches across, and this, for
+the observer, means looking at a star with an eye pupil
+more than three feet in diameter. This refractor
+is now in the Yerkes Observatory at Williams Bay,
+Lake Geneva, Wisconsin.</p>
+
+<p>There are several forms of reflectors. With one
+form, when it is pointed at a star, the rays of starlight
+fall direct through the telescope-tube upon a highly-polished
+mirror, so shaped that rays of light reflected
+thence are caused to fall converging upon a small
+plane-mirror in the center of the tube, from which
+they are thrown, parallel to the side of the tube, to the
+eye-piece, which converges them to the eye.</p>
+
+<p>The mirror of a reflector can be made very much
+larger than the object-glass of a refractor. The famous
+Lord Rosse telescope, which has a tube sixty
+feet long, contains a mirror no less than six feet in
+diameter. This, to an observer, is tantamount to
+looking at the stars with an eye so huge that its pupil
+alone would be nearly equal in size to the six-foot
+wheel of a steam-engine. It will readily be perceived
+how much more starlight can be grasped by such a
+fishing-net than by the tiny pupil of your eye or
+mine.</p>
+
+<p>A main difference between the two kinds of telescope
+thus resides in the fact that the star-rays—or
+any other kind of light-rays—when first captured,<span class="pagenum" id="Page_407">[Pg 407]</span>
+pass, in one case, <i>through</i> the glass on which they
+fall, and, in the other case, are thrown off <i>from</i> the
+mirror. In both cases, the whole amount of light so
+captured is gathered into a small compass, so as to be
+available for human sight.</p>
+
+<div class="figcenter" id="f63">
+<img src="images/fig63.jpg" alt="lick">
+<p class="caption">EYE-PIECE OF THE LICK TELESCOPE.</p>
+</div>
+
+<p>Once more, let me remind you, it should be always
+kept clearly in mind that every object that is seen by<span class="pagenum" id="Page_408">[Pg 408]</span>
+us—from a mote of dust to a sun, from a coal-scuttle
+to a star—is perceived purely and solely by the light
+which it gives out, either intrinsic or reflected light.
+Countless myriads of rays pass from the surface of the
+thing seen to our eyes, picturing there, on the sensitive
+retina, a fleeting vision of its form.</p>
+
+<p>All the leading Governments in Europe have observatories
+for the study of the heavens, which are
+furnished with the best instruments of modern construction.
+The principal observatories are those at
+Paris, Berlin, Vienna, Nice; Dorpat, the seat of a celebrated
+university founded by Gustavus Adolphus, of
+Sweden, in 1630; Pulkowa, near St. Petersburg; Lisbon,
+and at Greenwich in England. In America,
+though only in recent years has astronomy been cultivated
+with ardor, there are observatories of more or
+less importance,—the National Observatory at Washington,
+D. C.; the Cincinnati Observatory, projected
+by the late General O. M. Mitchel; the Dudley Observatory,
+founded by Mrs. Blandina Dudley in honor
+of her husband, at Albany, N. Y.; the Lick Observatory,
+founded by James Lick, on Mount Hamilton, Cal.;
+and the Yerkes Observatory, connected with the Chicago
+University, founded by Charles T. Yerkes. Besides
+these, there are observatories connected with some
+of our other leading universities and colleges, as those
+of Harvard, at Cambridge, Mass.; Yale University;
+Williams College; West Point Military Academy; Amherst
+College; Princeton; Dartmouth; Michigan University;
+Hamilton College, N. Y., and several others.</p>
+
+<div class="figcenter" id="f64">
+<img src="images/fig64.jpg" alt="lick">
+<p class="caption">LICK OBSERVATORY IN WINTER, FROM THE EAST.</p>
+</div>
+
+<p>The largest and best refracting telescopes in the
+world are those at Lick Observatory and at Yerkes
+<span class="pagenum" id="Page_410">[Pg 410]</span>Observatory, now in charge of Professor E. E. Barnard,
+who, while at the head of the Lick Observatory, discovered
+the fifth satellite of Jupiter, and determined
+the character of the inner ring of Saturn. The best
+reflecting telescope is that of Lord Rosse, at Birr Castle,
+in Kings County, Ireland.</p>
+
+<div class="figcenter" id="f65">
+<img src="images/fig65.jpg" alt="barnard">
+<p class="caption">E. E. BARNARD.</p>
+</div>
+
+<p>In reviewing the path which we have traversed in
+this volume, though we have penetrated the sidereal
+depths and wandered at will through space, we feel<span class="pagenum" id="Page_411">[Pg 411]</span>
+that we have not yet reached the outskirts of creation.
+We have never left the center. Beyond us still lies
+the circumference. We see opened before us the infinite,
+of which the study is not yet begun! We have
+seen nothing; we recoil in terror; we fall back astounded.
+Indeed, we might fall into the yawning
+abyss—fall forever, during a whole eternity; never,
+never should we reach the bottom, any more than we
+have attained the summit. There is no east nor west,
+neither right nor left. There is no up nor down;
+there is neither a zenith nor a nadir. In whatever
+way we look, it is infinite in all directions.</p>
+
+<p>In this infinitude of space, the associations of suns
+and of worlds which constitute our visible universe form
+but an island, a vast archipelago; and in the eternity
+of duration, the life of our proud humanity, with all
+its concerns, its aspirations, and its achievements, the
+whole life of our entire planet, is but the shadow of a
+dream! Well might the Hebrew poet, as he looked
+forth upon nature, exclaim in his amazement: “When
+I consider thy heavens, the work of thy fingers, the
+moon and the stars which thou hast ordained, what is
+man that thou art mindful of him, and the son of man
+that thou visitest him?”</p>
+
+<p>The constellations, the charts of the sky; the catalogues
+of curious stars—variable, double or multiple,
+and colored; the description of instruments accessible
+to the observer of the heavens, and useful tables to
+consult, are only touched upon in this volume. The
+reader whose scientific desires are satisfied by the elements
+of astronomy, may stop here. Few have time
+to pursue the subject further; but it is sweet to live<span class="pagenum" id="Page_412">[Pg 412]</span>
+in the sphere of the mind; it is sweet to contemn the
+rough noises of a vulgar world; it is sweet to soar in
+the ethereal heights, and to devote the best moments
+of our life to the study of the true, the infinite, and
+the eternal!</p>
+
+
+<div class="figcenter">
+<img src="images/fig3.jpg" alt="decoration">
+</div>
+
+
+<p class="c sp xlarge">PUBLISHERS’ NOTE.</p>
+
+
+
+<p>We have now reached the conclusion of “The
+Story of the Sun, Moon, and Stars.” Miss Giberne’s
+work has been supplemented with a large amount of
+matter from other sources. The value of the book
+has thus been increased without diminishing its popular
+character. In most admirable form it tells the
+story of the heavenly world, which is the work of
+God’s hands, the moon and the stars which he has
+made. The reverent reader, to whom the Word of
+God is “sweeter than honey and the honey-comb,”
+may here find that “the heavens declare the glory of
+God, and the firmament showeth his handiwork.”
+We confidently present it to the reader as the best
+and completest work in print on the great subject of
+which it treats.</p>
+
+
+<hr class="full x-ebookmaker-drop">
+
+<div class="chapter">
+<p class="ph2">INDEX</p>
+</div>
+
+<div class="figcenter">
+<img src="images/fig3.jpg" alt="decoration">
+</div>
+
+<ul class="index">
+<li class="ifrst">Adams, John Couch, <a href="#Page_231">231</a>, <a href="#Page_236">236</a></li>
+
+<li class="indx">Aërolites, <a href="#Page_84">84</a></li>
+<li class="isub1">Size of, <a href="#Page_86">86</a></li>
+
+<li class="indx">Aldebaran, Movement of, <a href="#Page_277">277</a></li>
+
+<li class="indx">Alexander at Arbela, <a href="#Page_146">146</a></li>
+
+<li class="indx">Alpha Centauri, Distance of, <a href="#Page_99">99</a></li>
+<li class="isub1">Duration of light journey, <a href="#Page_102">102</a></li>
+<li class="isub1">Position, <a href="#Page_279">279</a></li>
+
+<li class="indx">Alps, Lunar Mountains, <a href="#Page_179">179</a></li>
+
+<li class="indx">Altai, Lunar Mountains, <a href="#Page_179">179</a></li>
+
+<li class="indx">Andromeda, Constellation of, <a href="#Page_112">112</a></li>
+
+<li class="indx">Apennines, Lunar Mountains, <a href="#Page_179">179</a></li>
+
+<li class="indx">Arago, <a href="#Page_235">235</a>, <a href="#Page_402">402</a></li>
+
+<li class="indx">Arcturus, Motion of, <a href="#Page_114">114</a></li>
+<li class="isub1">Position, <a href="#Page_276">276</a></li>
+
+<li class="indx">Aristotle, <a href="#Page_376">376</a></li>
+
+<li class="indx">Asteroids, <a href="#Page_53">53</a></li>
+
+<li class="indx">Astronomy, The dawn of, <a href="#Page_363">363</a></li>
+
+<li class="indx">Attraction, <a href="#Page_34">34</a></li>
+
+<li class="indx">Aurora Borealis, where seen, <a href="#Page_141">141</a></li>
+
+<li class="indx">Axis of earth slanting, <a href="#Page_44">44</a></li>
+
+
+<li class="ifrst">Barnard, E. E., <a href="#Page_53">53</a>, <a href="#Page_410">410</a></li>
+
+<li class="indx">Bessel, F. W., <a href="#Page_284">284</a></li>
+<li class="isub1">Discovery of star parallax, <a href="#Page_324">324</a></li>
+<li class="isub1">Discovers star parallax, <a href="#Page_405">405</a></li>
+
+<li class="indx">Bolides, <a href="#Page_87">87</a>, <a href="#Page_257">257</a></li>
+
+<li class="indx">Borelli, <a href="#Page_388">388</a></li>
+
+
+<li class="ifrst">Capella, Duration of light journey, <a href="#Page_103">103</a></li>
+<li class="isub1">Velocity of motion, <a href="#Page_114">114</a></li>
+
+<li class="indx">Caucasian Range, Lunar Mountains, <a href="#Page_179">179</a></li>
+
+<li class="indx">Carpathian, Lunar Mountains, <a href="#Page_179">179</a></li>
+
+<li class="indx">Carrington, <a href="#Page_141">141</a></li>
+
+<li class="indx">Cassini, Measurement of sun’s distance, <a href="#Page_310">310</a></li>
+
+<li class="indx">Cassiopeia, Constellation of, <a href="#Page_112">112</a></li>
+
+<li class="indx">Ceres, size of, <a href="#Page_53">53</a></li>
+
+<li class="indx">Chaldean star-gazers, <a href="#Page_365">365</a></li>
+
+<li class="indx">Chinese records of eclipses, <a href="#Page_365">365</a></li>
+
+<li class="indx">Cicero, <a href="#Page_177">177</a></li>
+
+<li class="indx">Clark, Alvan Graham, <a href="#Page_289">289</a></li>
+
+<li class="indx">Cloven-disk theory, <a href="#Page_331">331</a></li>
+
+<li class="indx">Coal sack, <a href="#Page_329">329</a></li>
+
+<li class="indx">Columbus in Jamaica, <a href="#Page_146">146</a></li>
+
+<li class="indx">Comet, Biela’s, <a href="#Page_90">90</a>, <a href="#Page_93">93</a></li>
+<li class="isub1">Halley’s, <a href="#Page_78">78</a>, <a href="#Page_248">248</a></li>
+<li class="isub1">Of 1843, <a href="#Page_80">80</a></li>
+<li class="isub1">Newton’s, <a href="#Page_78">78</a></li>
+<li class="isub1">With two tails, <a href="#Page_77">77</a></li>
+<li class="isub1">Encke’s, <a href="#Page_78">78</a></li>
+<li class="isub1">Heat endured by, <a href="#Page_81">81</a></li>
+<li class="isub1">Length of tail, <a href="#Page_81">81</a></li>
+<li class="isub1">Collision with, <a href="#Page_82">82</a></li>
+<li class="isub1">Split in two, <a href="#Page_91">91</a></li>
+
+<li class="indx">Comets, <a href="#Page_73">73</a>, <a href="#Page_240">240</a>, <a href="#Page_246">246</a></li>
+<li class="isub1">Number of, <a href="#Page_75">75</a></li>
+<li class="isub1">Nature of, <a href="#Page_74">74</a></li>
+<li class="isub1">Captured by Jupiter, <a href="#Page_213">213</a></li>
+<li class="isub1">Composition of, <a href="#Page_256">256</a></li>
+<li class="isub1">Composition of tails, <a href="#Page_253">253</a></li>
+<li class="isub1">Orbits of, <a href="#Page_129">129</a></li>
+<li class="isub1">With closed orbits, <a href="#Page_76">76</a></li>
+
+<li class="indx">Confucius as an astronomer, <a href="#Page_365">365</a></li>
+
+<li class="indx">Constellations, Grouping, <a href="#Page_366">366</a></li>
+<li class="isub1">When named, <a href="#Page_366">366</a></li>
+
+<li class="indx">Copernicus, Author of “Celestial Spheres,” <a href="#Page_177">177</a>, <a href="#Page_183">183</a>, <a href="#Page_370">370</a>, <a href="#Page_371">371</a>,
+    <a href="#Page_375">375</a></li>
+<li class="isub1">Star parallax, <a href="#Page_319">319</a></li>
+
+<li class="indx">Copernican system of the universe, <a href="#Page_175">175</a></li>
+
+<li class="indx">Corona, Description of, <a href="#Page_153">153</a></li>
+
+
+<li class="ifrst">D’Alembert, <a href="#Page_399">399</a></li>
+
+<li class="indx">Dante, <a href="#Page_121">121</a></li>
+
+<li class="indx">Demos, Satellite of Mars, <a href="#Page_191">191</a></li>
+
+<li class="indx">Donati’s Comet, <a href="#Page_248">248</a>, <a href="#Page_250">250</a></li>
+
+<li class="indx">Draco, Constellation of, <a href="#Page_112">112</a></li>
+
+
+<li class="ifrst">Earth, Globular, <a href="#Page_17">17</a></li>
+<li class="isub1">How formed, <a href="#Page_21">21</a></li>
+<li class="isub1">Member of the Solar System, <a href="#Page_14">14</a></li>
+<li class="isub1">In motion, <a href="#Page_16">16</a></li>
+<li class="isub1">Motions, <a href="#Page_18">18</a>, <a href="#Page_41">41</a>, <a href="#Page_126">126</a></li>
+<li class="isub1">One of a family, <a href="#Page_14">14</a></li>
+<li class="isub1">Size of, <a href="#Page_26">26</a></li>
+<li class="isub1">What is it? <a href="#Page_13">13</a></li>
+
+<li class="indx">Ecliptic, <a href="#Page_43">43</a></li>
+
+<li class="indx">Eclipses omens of evil, <a href="#Page_145">145</a></li>
+
+<li class="indx">Egyptian astronomers, <a href="#Page_365">365</a></li>
+
+<li class="indx">Encke, <a href="#Page_238">238</a></li>
+
+<li class="indx">Epicycles, <a href="#Page_373">373</a></li>
+
+<li class="indx">Equinox, <a href="#Page_44">44</a></li>
+
+
+<li class="ifrst">Fire-balls, Speed of, <a href="#Page_88">88</a></li>
+
+<li class="indx">Fabricius discovers sun-spots, <a href="#Page_27">27</a></li>
+
+<li class="indx">Fraunhofer, Joseph von, <a href="#Page_345">345</a></li>
+
+
+<li class="ifrst">Galle, <a href="#Page_232">232</a>, <a href="#Page_238">238</a></li>
+
+<li class="indx">Galileo, <a href="#Page_28">28</a>, <a href="#Page_276">276</a>, <a href="#Page_371">371</a>, <a href="#Page_376">376</a>, <a href="#Page_378">378</a>,
+    <a href="#Page_380">380</a></li>
+
+<li class="indx">Gassendi, <a href="#Page_184">184</a></li>
+
+<li class="indx">George III, <a href="#Page_226">226</a></li>
+
+<li class="indx">Gilbert, <a href="#Page_388">388</a></li>
+
+<li class="indx">Great Bear, Constellation of, <a href="#Page_108">108</a>, <a href="#Page_340">340</a></li>
+
+
+<li class="ifrst">Halley, <a href="#Page_388">388</a></li>
+<li class="isub1">Transit of Venus, <a href="#Page_314">314</a></li>
+<li class="isub1">Star motions, <a href="#Page_318">318</a></li>
+
+<li class="indx">Hercules, Constellation of, <a href="#Page_112">112</a></li>
+
+<li class="indx">Herschel, Caroline, <a href="#Page_226">226</a>, <a href="#Page_393">393</a></li>
+
+<li class="indx">Herschel, Sir John, <a href="#Page_81">81</a>, <a href="#Page_233">233</a>, <a href="#Page_303">303</a>, <a href="#Page_398">398</a></li>
+
+<li class="indx">Herschel, William, <a href="#Page_96">96</a>, <a href="#Page_119">119</a>, <a href="#Page_225">225</a>, <a href="#Page_271">271</a>, <a href="#Page_393">393</a></li>
+
+<li class="indx">Hipparchus, <a href="#Page_368">368</a>, <a href="#Page_371">371</a></li>
+
+<li class="indx">Hodgson, <a href="#Page_141">141</a></li>
+
+<li class="indx">Holland, Sir Henry, <a href="#Page_237">237</a></li>
+
+<li class="indx">Hook, Robert, <a href="#Page_388">388</a></li>
+
+<li class="indx">Horrocks, <a href="#Page_388">388</a></li>
+
+<li class="indx">Huggins, Dr., <a href="#Page_359">359</a></li>
+
+<li class="indx">Humboldt, Alexander von, <a href="#Page_265">265</a></li>
+
+
+<li class="ifrst">Jupiter, <a href="#Page_55">55</a></li>
+<li class="isub1">Comparative size, <a href="#Page_56">56</a></li>
+<li class="isub1">Distance of, <a href="#Page_122">122</a></li>
+<li class="isub1">His satellites, <a href="#Page_56">56</a>, <a href="#Page_206">206</a>, <a href="#Page_210">210</a></li>
+<li class="isub1">Velocity, <a href="#Page_199">199</a></li>
+<li class="isub1">Wind storms, <a href="#Page_204">204</a></li>
+
+
+<li class="ifrst">Kepler, <a href="#Page_75">75</a>, <a href="#Page_296">296</a></li>
+<li class="isub1">Laws of, <a href="#Page_371">371</a>, <a href="#Page_374">374</a>, <a href="#Page_380">380</a>, <a href="#Page_388">388</a></li>
+
+<li class="indx">Kew Observatory, <a href="#Page_141">141</a></li>
+
+
+<li class="ifrst">Lacaille, Catalogue of, <a href="#Page_105">105</a></li>
+
+<li class="indx">Lalande, Catalogue of, <a href="#Page_105">105</a></li>
+
+<li class="indx">Laplace, <a href="#Page_385">385</a>, <a href="#Page_398">398</a></li>
+
+<li class="indx">Later astronomy, <a href="#Page_393">393</a></li>
+
+<li class="indx">Leverrier, Urbain J. J., <a href="#Page_231">231</a>, <a href="#Page_401">401</a></li>
+<li class="isub1">Discovers Neptune, <a href="#Page_321">321</a></li>
+
+<li class="indx">Light, Rapidity of, <a href="#Page_101">101</a></li>
+<li class="isub1">Time, Duration of, <a href="#Page_331">331</a></li>
+
+<li class="indx">Lowe at Santander, <a href="#Page_147">147</a></li>
+
+<li class="indx">Lunar craters, Antiquity of, <a href="#Page_172">172</a></li>
+<li class="isub1">How formed, <a href="#Page_173">173</a></li>
+<li class="isub1">Plato and Copernicus, <a href="#Page_173">173</a></li>
+<li class="isub1">Ptolemy, <a href="#Page_174">174</a></li>
+<li class="isub1">Schickard, <a href="#Page_174">174</a></li>
+<li class="isub1">Tycho, <a href="#Page_174">174</a></li>
+
+<li class="indx">Lunar Mountains, How formed, <a href="#Page_174">174</a></li>
+
+<li class="indx">Lyra, Constellation, <a href="#Page_297">297</a></li>
+
+
+<li class="ifrst">Magellanic clouds, <a href="#Page_309">309</a></li>
+
+<li class="indx">Magnetism, <a href="#Page_140">140</a>, <a href="#Page_141">141</a></li>
+
+<li class="indx">Mars, <a href="#Page_52">52</a>, <a href="#Page_373">373</a>, <a href="#Page_374">374</a></li>
+<li class="isub1">Moons of, <a href="#Page_191">191</a></li>
+<li class="isub1">Continents of, <a href="#Page_197">197</a></li>
+<li class="isub1">Distance from earth, <a href="#Page_197">197</a></li>
+
+<li class="indx">Maury, Lieutenant, <a href="#Page_80">80</a></li>
+
+<li class="indx">Mercury, Atmosphere, <a href="#Page_181">181</a></li>
+<li class="isub1">Distance from sun, <a href="#Page_49">49</a></li>
+<li class="isub1">Length of year, <a href="#Page_180">180</a></li>
+<li class="isub1">Is it inhabited? <a href="#Page_181">181</a></li>
+<li class="isub1">Orbit of, <a href="#Page_180">180</a></li>
+<li class="isub1">Phases, <a href="#Page_50">50</a></li>
+<li class="isub1">Size of, <a href="#Page_49">49</a></li>
+<li class="isub1">Transit of, <a href="#Page_184">184</a></li>
+
+<li class="indx">Meteor, <a href="#Page_84">84</a>, <a href="#Page_257">257</a></li>
+
+<li class="indx">Meteorites, <a href="#Page_240">240</a>, <a href="#Page_257">257</a></li>
+<li class="isub1">Around the sun, <a href="#Page_94">94</a></li>
+<li class="isub1">August system, <a href="#Page_90">90</a>, <a href="#Page_242">242</a></li>
+<li class="isub1">In Saturn’s rings, <a href="#Page_94">94</a></li>
+<li class="isub1">November system, <a href="#Page_90">90</a>, <a href="#Page_94">94</a>, <a href="#Page_241">241</a></li>
+<li class="isub1">Number of, <a href="#Page_86">86</a></li>
+<li class="isub1">Protection from, <a href="#Page_86">86</a></li>
+<li class="isub1">Shower of 1872, <a href="#Page_92">92</a></li>
+<li class="isub1">Shower of 1885, <a href="#Page_93">93</a></li>
+
+<li class="indx">Milky Way, <a href="#Page_270">270</a>, <a href="#Page_329">329</a></li>
+
+<li class="indx">Mizar, <a href="#Page_342">342</a></li>
+
+<li class="indx">Modern Astronomy, <a href="#Page_375">375</a></li>
+
+<li class="indx">Moon, <a href="#Page_62">62</a></li>
+<li class="isub1">Appearance at its full, <a href="#Page_63">63</a></li>
+<li class="isub1">Atmosphere, <a href="#Page_157">157</a>, <a href="#Page_169">169</a></li>
+<li class="isub1">Phases of, <a href="#Page_160">160</a></li>
+<li class="isub1">Condition of, <a href="#Page_65">65</a></li>
+<li class="isub1">Craters, <a href="#Page_68">68</a>, <a href="#Page_170">170</a></li>
+<li class="isub1">Earth’s satellite, <a href="#Page_164">164</a></li>
+<li class="isub1">Earth-shine, <a href="#Page_160">160</a></li>
+<li class="isub1">Eclipse, <a href="#Page_163">163</a></li>
+<li class="isub1">Influence on tides, <a href="#Page_167">167</a></li>
+<li class="isub1">Landscape of, <a href="#Page_68">68</a></li>
+<li class="isub1">Mountains, <a href="#Page_67">67</a></li>
+<li class="isub1">Orbit of, <a href="#Page_166">166</a></li>
+<li class="isub1">Temperature on, <a href="#Page_72">72</a></li>
+<li class="isub1">Revolution, <a href="#Page_64">64</a></li>
+<li class="isub1">Size of, <a href="#Page_64">64</a></li>
+<li class="isub1">Surface, <a href="#Page_67">67</a></li>
+
+
+<li class="ifrst">Nasmyth, <a href="#Page_173">173</a></li>
+
+<li class="indx">Nebulæ, Number of, <a href="#Page_336">336</a></li>
+
+<li class="indx">Neptune, <a href="#Page_59">59</a></li>
+<li class="isub1">Discovery of, <a href="#Page_232">232</a>, <a href="#Page_234">234</a></li>
+<li class="isub1">Distance of, <a href="#Page_123">123</a></li>
+<li class="isub1">Length of year, <a href="#Page_59">59</a></li>
+
+<li class="indx">Newton analyzes light, <a href="#Page_385">385</a></li>
+<li class="isub1">Birth and childhood, <a href="#Page_382">382</a></li>
+
+<li class="indx">Nicetos of Syracuse, <a href="#Page_177">177</a></li>
+
+<li class="indx">Nicias, Athenian General, <a href="#Page_146">146</a></li>
+
+<li class="indx">Nicolas, Cardinal, <a href="#Page_177">177</a></li>
+
+
+<li class="ifrst">Observatories, <a href="#Page_408">408</a></li>
+
+<li class="indx">Orbits, Planetary, <a href="#Page_47">47</a></li>
+
+<li class="indx">Orion, Constellation of, <a href="#Page_112">112</a></li>
+
+
+<li class="ifrst">Parallax, <a href="#Page_311">311</a></li>
+
+<li class="indx">Phobos, Satellite of Mars, <a href="#Page_191">191</a></li>
+
+<li class="indx">Photography, Stellar, <a href="#Page_355">355</a></li>
+
+<li class="indx">Pius IX, <a href="#Page_93">93</a></li>
+
+<li class="indx">Pisa, Leaning Tower of, <a href="#Page_378">378</a></li>
+
+<li class="indx">Plane of the Ecliptic, <a href="#Page_201">201</a></li>
+
+<li class="indx">Planets, Distance from the sun, <a href="#Page_123">123</a></li>
+<li class="isub1">First group, <a href="#Page_48">48</a></li>
+<li class="isub1">How formed, <a href="#Page_22">22</a></li>
+<li class="isub1">Length of years, <a href="#Page_49">49</a></li>
+<li class="isub1">Orbits, <a href="#Page_47">47</a></li>
+<li class="isub1">Order of formation, <a href="#Page_23">23</a></li>
+<li class="isub1">Second group, <a href="#Page_48">48</a>, <a href="#Page_55">55</a></li>
+
+<li class="indx">Plutarch, <a href="#Page_177">177</a></li>
+
+<li class="indx">Pole star, Duration of light journey, <a href="#Page_103">103</a></li>
+<li class="isub1">Position, <a href="#Page_108">108</a></li>
+<li class="isub1">Rate of motion, <a href="#Page_115">115</a></li>
+
+<li class="indx">Prism, <a href="#Page_344">344</a></li>
+
+<li class="indx">Pritchard, C., <a href="#Page_356">356</a></li>
+
+<li class="indx">Ptolemaic system of the universe, <a href="#Page_175">175</a>, <a href="#Page_369">369</a></li>
+
+<li class="indx">Ptolemy, <a href="#Page_371">371</a>, <a href="#Page_369">369</a></li>
+
+<li class="indx">Pythagoras, Grecian astronomer, <a href="#Page_367">367</a></li>
+
+
+<li class="ifrst">Rosse, Lord, Telescope, <a href="#Page_406">406</a></li>
+
+<li class="indx">Rowton siderite, <a href="#Page_258">258</a></li>
+
+
+<li class="ifrst">Saturn, <a href="#Page_57">57</a></li>
+<li class="isub1">Composition of rings, <a href="#Page_221">221</a></li>
+<li class="isub1">Distance of, <a href="#Page_122">122</a></li>
+<li class="isub1">Distance from sun, <a href="#Page_214">214</a></li>
+<li class="isub1">Length of year, <a href="#Page_57">57</a></li>
+<li class="isub1">Moons, <a href="#Page_217">217</a></li>
+<li class="isub1">Rings, <a href="#Page_219">219</a></li>
+<li class="isub1">Satellites, <a href="#Page_58">58</a></li>
+<li class="isub1">Size, <a href="#Page_214">214</a></li>
+<li class="isub1">Weight, <a href="#Page_214">214</a></li>
+
+<li class="indx">Shickard, Crater on the moon, <a href="#Page_174">174</a></li>
+
+<li class="indx">Scheiner, <a href="#Page_28">28</a></li>
+
+<li class="indx">Secchi, <a href="#Page_92">92</a></li>
+
+<li class="indx">Shooting stars, <a href="#Page_84">84</a></li>
+
+<li class="indx">Sirius, Brightness of, <a href="#Page_275">275</a>, <a href="#Page_285">285</a></li>
+<li class="isub1">Changing color, <a href="#Page_285">285</a></li>
+<li class="isub1">Distance of, <a href="#Page_100">100</a></li>
+<li class="isub1">Duration of light journey, <a href="#Page_103">103</a></li>
+<li class="isub1">Movement of, <a href="#Page_277">277</a></li>
+
+<li class="indx">Solar cloud, <a href="#Page_148">148</a></li>
+
+<li class="indx">Solar System, <a href="#Page_60">60</a>, <a href="#Page_122">122</a></li>
+<li class="isub1">Model of, <a href="#Page_60">60</a></li>
+
+<li class="indx">Spectroscope, <a href="#Page_143">143</a>, <a href="#Page_345">345</a></li>
+
+<li class="indx">Spectroscopic photography, <a href="#Page_360">360</a></li>
+
+<li class="indx">Spectrum analysis, <a href="#Page_346">346</a>, <a href="#Page_354">354</a></li>
+
+<li class="indx">Star clusters, <a href="#Page_304">304</a>, <a href="#Page_336">336</a></li>
+<li class="isub1">Parallax, <a href="#Page_284">284</a>, <a href="#Page_316">316</a></li>
+<li class="isub1">Spectroscopy, <a href="#Page_356">356</a></li>
+
+<li class="indx">Stars, Apparent motion, <a href="#Page_107">107</a></li>
+<li class="isub1">Attraction, <a href="#Page_21">21</a></li>
+<li class="isub1">Distance of, <a href="#Page_99">99</a>, <a href="#Page_310">310</a>, <a href="#Page_320">320</a></li>
+<li class="isub1">Distance, <a href="#Page_281">281</a>, <a href="#Page_282">282</a></li>
+<li class="isub1">Fixed, Why so called, <a href="#Page_20">20</a></li>
+<li class="isub1">Fixed, Why, <a href="#Page_366">366</a></li>
+<li class="isub1">Golden, <a href="#Page_274">274</a></li>
+<li class="isub1">Magnitude of, <a href="#Page_97">97</a></li>
+<li class="isub1">How many visible, <a href="#Page_95">95</a></li>
+<li class="isub1">Measurement, <a href="#Page_278">278</a></li>
+<li class="isub1">Red, <a href="#Page_274">274</a></li>
+<li class="isub1">Variable, <a href="#Page_274">274</a>, <a href="#Page_291">291</a></li>
+<li class="isub1">White, <a href="#Page_274">274</a></li>
+
+<li class="indx">Sun, <a href="#Page_24">24</a></li>
+<li class="isub1">Attraction of, <a href="#Page_156">156</a></li>
+<li class="isub1">Attraction of gravitation, <a href="#Page_34">34</a></li>
+<li class="isub1">Chromatosphere, <a href="#Page_32">32</a></li>
+<li class="isub1">Cyclones of <a href="#Page_30">30</a>, <a href="#Page_136">136</a></li>
+<li class="isub1">Density, <a href="#Page_26">26</a></li>
+<li class="isub1">Destination, <a href="#Page_119">119</a></li>
+<li class="isub1">Distance of, <a href="#Page_25">25</a></li>
+<li class="isub1">Eclipse of, <a href="#Page_143">143</a></li>
+<li class="isub1">Flames, Their height, <a href="#Page_31">31</a>, <a href="#Page_151">151</a></li>
+<li class="isub1">Flames, Their velocity, <a href="#Page_138">138</a></li>
+<li class="isub1">Forces and influences, <a href="#Page_39">39</a></li>
+<li class="isub1">Head of our family, <a href="#Page_24">24</a></li>
+<li class="isub1">Magnetic power of, <a href="#Page_139">139</a></li>
+<li class="isub1">Its mottled appearance, <a href="#Page_142">142</a></li>
+<li class="isub1">Rate of motion, <a href="#Page_119">119</a></li>
+<li class="isub1">Penumbra, <a href="#Page_133">133</a></li>
+<li class="isub1">Photosphere, <a href="#Page_31">31</a>, <a href="#Page_134">134</a></li>
+<li class="isub1">Power of, <a href="#Page_39">39</a>, <a href="#Page_137">137</a></li>
+<li class="isub1">Rapidity of motion, <a href="#Page_26">26</a></li>
+<li class="isub1">Revolution on axis, <a href="#Page_28">28</a></li>
+<li class="isub1">Size, <a href="#Page_26">26</a>, <a href="#Page_154">154</a></li>
+<li class="isub1">Solar prominence, <a href="#Page_32">32</a></li>
+<li class="isub1">Spots, <a href="#Page_27">27</a>, <a href="#Page_30">30</a>, <a href="#Page_133">133</a></li>
+<li class="isub1">Symbol of purity, <a href="#Page_380">380</a></li>
+<li class="isub1">Umbra, <a href="#Page_133">133</a></li>
+<li class="isub1">Weight, <a href="#Page_27">27</a>, <a href="#Page_154">154</a></li>
+
+<li class="indx">Swift, Voyage to Laputa, <a href="#Page_194">194</a></li>
+
+
+<li class="ifrst">Telescopes, <a href="#Page_378">378</a>, <a href="#Page_379">379</a>, <a href="#Page_405">405</a></li>
+<li class="isub1">Refractors and reflectors, <a href="#Page_405">405</a>, <a href="#Page_408">408</a>, <a href="#Page_410">410</a></li>
+
+<li class="indx">Tides, <a href="#Page_168">168</a></li>
+
+<li class="indx">Thales, founder of Grecian Astronomy, <a href="#Page_367">367</a></li>
+
+<li class="indx">Toucan, <a href="#Page_306">306</a></li>
+
+<li class="indx">Tycho Brahe, <a href="#Page_175">175</a>, <a href="#Page_371">371</a>, <a href="#Page_372">372</a>, <a href="#Page_373">373</a></li>
+
+
+<li class="ifrst">Universe, Definition of, <a href="#Page_19">19</a></li>
+
+<li class="indx">Uranus, <a href="#Page_58">58</a></li>
+<li class="isub1">Discovery of, <a href="#Page_225">225</a></li>
+<li class="isub1">Distance of, <a href="#Page_123">123</a></li>
+
+
+<li class="ifrst">Venus, Orbit of <a href="#Page_51">51</a></li>
+<li class="isub1">Is it inhabited? <a href="#Page_189">189</a></li>
+<li class="isub1">Distance from earth, <a href="#Page_186">186</a></li>
+<li class="isub1">Phases of, <a href="#Page_51">51</a>, <a href="#Page_379">379</a></li>
+<li class="isub1">Transits of, <a href="#Page_185">185</a></li>
+
+<li class="indx">Vesta, Size of, <a href="#Page_53">53</a></li>
+
+<li class="indx">Voltaire, Prophecy of, <a href="#Page_193">193</a></li>
+
+
+<li class="ifrst">Wilson, <a href="#Page_30">30</a></li>
+
+<li class="indx">Wollaston, Dr. W. H., <a href="#Page_345">345</a></li>
+
+<li class="indx">Wren, <a href="#Page_388">388</a></li>
+
+
+<li class="ifrst">Yerkes Observatory, <a href="#Page_406">406</a></li>
+
+<li class="indx">Young, Chas. A., <a href="#Page_142">142</a>, <a href="#Page_148">148</a></li>
+
+
+<li class="ifrst">Zodiacal Light, <a href="#Page_94">94</a>, <a href="#Page_224">224</a>, <a href="#Page_265">265</a></li>
+</ul>
+
+<hr class="full">
+
+<div class="transnote">
+
+<p class="c">Transcriber’s Notes:</p>
+
+<p>In the original a link to Sir Isaac Newton was omitted from the List of Illustrations. The transcriber has inserted one.</p>
+
+<p>Variations in spelling and hyphenation are retained.</p>
+
+<p>Perceived typographical errors have been changed.</p>
+
+</div>
+
+<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 77004 ***</div>
+</body>
+</html>
+
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diff --git a/LICENSE.txt b/LICENSE.txt
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@@ -0,0 +1,11 @@
+This book, including all associated images, markup, improvements,
+metadata, and any other content or labor, has been confirmed to be
+in the PUBLIC DOMAIN IN THE UNITED STATES.
+
+Procedures for determining public domain status are described in
+the "Copyright How-To" at https://www.gutenberg.org.
+
+No investigation has been made concerning possible copyrights in
+jurisdictions other than the United States. Anyone seeking to utilize
+this book outside of the United States should confirm copyright
+status under the laws that apply to them.
diff --git a/README.md b/README.md
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+++ b/README.md
@@ -0,0 +1,2 @@
+Project Gutenberg (https://www.gutenberg.org) public repository for book #77004
+(https://www.gutenberg.org/ebooks/77004)