,illustration ,curiosities of the ,sky by ,garrett ,p4 ,serviss ,contents ,,preface ,,curiosities ,,of ,,the ,,sky ,i4 ,the ,windows of ,absolute ,night ,,ii4 ,star-,clouds1 ,star-,clusters1 and ,star-,streams ,,iii4 ,stellar ,migrations ,,iv4 ,the ,passing of the ,constellations ,v4 ,conflagrations in the ,heavens ,,vi4 ,explosive and ,whirling ,nebul ,,vii4 ,the ,banners of the ,sun ,,viii4 ,the ,zodiacal ,light ,mystery ,,ix4 ,marvels of the ,aurora ,x4 ,strange ,adventures of ,comets ,,xi4 ,meteors1 ,fire-,balls1 and ,meteorites ,,xii4 ,the ,wrecking of the ,moon ,,xiii4 ,the ,great ,mars ,problem ,,xiv4 ,the ,riddle of the ,asteroids ,illustration3 ,great spiral nebula in ,andromeda ,illustrations ,great spiral nebula in ,andromeda ,the ,milky ,way ,star-cluster in ,hercules ,great southern star-cluster1 ,omega ,centauri ,the ,pleiades ,the 8,great ,dipper0 ,cassiopeia ,the 8,northern ,crown0 ,the 8,southern ,cross0 ,chart showing location of ,tycho's star1 #aegb1 and ,nova ,persei of #aija ,nova ,persei1 with its nebular rings ,lord ,rosse's nebula ,wonderful spiral in triangulum ,spiral in ,ursa ,major ,nebula in ,cetus ,the ,orion nebula ,the ,corona ,a solar 8prominence0 ,auroral beams seen in ,england ,auroral arches of an eliptic form seen in the ,arctic regions ,auroral curtain seen in ,scandinavia ,auroral arches seen in ,scandinavia ,swift's comet ,daniels' comet ,brooks' comet ,curious forms of meteorite trains ,section of the atmosphere up to #ajj kilometers ,a meteor photographed in flight ,looking across ,coon ,butte crater from northern rim ,trail on south side1 ,coon ,butte crater ,the craters ,clavius1 ,longomontanus1 ,tycho1 etc4 ,western part of the ,mare ,serenitatis ,mare ,tranquilitatis and surroundings ,lunar craters ,theophilus and surrounding region ,mare ,crisium ,schiaparelli's chart of ,mars1 showing the so-called system of canals ,,preface ,what ,froude says of history is true also of astronomy3 it is the most impressive where it transcends explanation4 ,it is not the mathematics of astronomy1 but the wonder and the mystery that seize upon the imagination4 ,the calculation of an eclipse owes all its prestige to the sublimity of its data2 the operation1 in itself1 requires no more mental effort than the preparation of a railway time-table4 ,the dominion which astronomy has always held over the minds of men is akin to that of poetry2 when the former becomes merely instructive and the latter purely didactic1 both lose their power over the imagination4 ,astronomy is known as the oldest of the sciences1 and it will be the longest-lived because it will always have arcana that have not been penetrated4 ,some of the things described in this book are little known to the average reader1 while others are well known2 but all possess the fascination of whatever is strange1 marvelous1 obscure1 or mysterious--magnified1 in this case1 by the portentous scale of the phenomena4 ,the idea of the author is to tell about these things in plain language1 but with as much scientific accuracy as plain language will permit1 showing the wonder that is in them without getting away from the facts4 ,most of them have hitherto been discussed only in technical form1 and in treatises that the general public seldom sees and never reads4 ,among the topics touched upon are3 ,the strange unfixedness of the 8fixed stars10 the vast migrations of the suns and worlds constituting the universe4 ,the slow passing out of existence of those collocations of stars which for thousands of years have formed famous 8constellations10 preserving the memory of mythological heroes and heroines1 and perhaps of otherwise unrecorded history4 ,the tendency of stars to assemble in immense clouds1 swarms1 and clusters4 ,the existence in some of the richest regions of the universe of absolutely black1 starless gaps1 deeps1 or holes1 as if one were looking out of a window into the murkiest night4 ,the marvelous phenomena of new1 or temporary1 stars1 which appear as suddenly as conflagrations1 and often turn into something else as eccentric as themselves4 ,the amazing forms of the 8whirlpool10 8spiral10 8pinwheel10 and 8lace10 or 8tress10 nebul4 ,the strange surroundings of the sun1 only seen in particular circumstances1 but evidently playing a constant part in the daily phenomena of the solar system4 ,the mystery of the ,zodiacal ,light and the ,gegenschein4 ,the extraordinary transformations undergone by comets and their tails4 ,the prodigies of meteorites and masses of stone and metal fallen from the sky4 ,the cataclysms that have wrecked the moon4 ,the problem of life and intelligence on the planet ,mars4 ,the problematical origin and fate of the asteroids4 ,the strange phenomena of the auroral lights4 ,an attempt has been made to develop these topics in an orderly way1 showing their connection1 so that the reader may obtain a broad general view of the chief mysteries and problems of astronomy1 and an idea of the immense field of discovery which still lies1 almost unexplored1 before it4 ,,curiosities ,,of ,,the ,,sky ,i ,the ,windows of ,absolute ,night ,to most minds mystery is more fascinating than science4 ,but when science itself leads straight up to the borders of mystery and there comes to a dead stop1 saying1 8,at present ,i can no longer see my way10 the force of the charm is redoubled4 ,on the other hand1 the illimitable is no less potent in mystery than the invisible1 whence the dramatic effect of ,keats' 8stout ,cortez0 staring at the boundless ,pacific while all his men look at each other with a wild surmise1 8silent upon a peak in ,darien40 ,it is with similar feelings that the astronomer regards certain places where from the peaks of the universe his vision seems to range out into endless empty space4 ,he sees there the shore of his little isthmus1 and1 beyond1 unexplored immensity4 ,the name1 8coal-sacks10 given to these strange voids is hardly descriptive4 ,rather they produce upon the mind the effect of blank windows in a lonely house on a pitch-dark night1 which1 when looked at from the brilliant interior1 become appalling in their rayless murk4 ,infinity seems to acquire a new meaning in the presence of these black openings in the sky1 for as one continues to gaze it loses its purely metaphysical quality and becomes a kind of entity1 like the ocean4 ,the observer is conscious that he can actually see the beginning of its ebon depths1 in which the visible universe appears to float like an enchanted island1 resplendent within with lights and life and gorgeous spectacles1 and encircled with screens of crowded stars1 but with its dazzling vistas ending at the fathomless sea of pure darkness which encloses all4 ,the ,galaxy1 or ,milky ,way1 surrounds the borders of our island in space like a stellar garland1 and when openings appear in it they are1 by contrast1 far more impressive than the general darkness of the interstellar expanse seen in other directions4 ,yet even that expanse is not everywhere equally dark1 for it contains gloomy deeps discernable with careful watching4 ,here1 too1 contrast plays an important part1 though less striking than within the galactic region4 ,some of ,sir ,william ,herschel's observations appear to indicate an association between these tenebrious spots and neighboring star clouds and nebul4 ,it is an illuminating bit of astronomical history that when he was sweeping the then virgin heavens with his great telescopes he was accustomed to say to his sister who1 note-book in hand1 waited at his side to take down his words1 fresh with the inspiration of discovery3 8,prepare to write2 the nebul are coming2 here space is vacant40 ,the most famous of the 8coal-sacks10 and the first to be brought to general attention before astronomers had awakened to the significance of such things1 lies adjacent to the 8,southern ,cross10 and is truly an amazing phenomenon4 ,it is not alone the conspicuousness of this celestial vacancy1 opening suddenly in the midst of one of the richest parts of the ,galaxy1 that has given it its fame1 but quite as much the superstitious awe with which it was regarded by the early explorers of the ,south ,seas4 ,to them1 as well as to those who listened in rapt wonder to their tales1 the 8,coal-sack0 seemed to possess some occult connection with the mystic 8,cross40 ,in the eyes of the sailors it was not a vacancy so much as a sable reality in the sky1 and as1 shuddering1 they stared at it1 they piously crossed themselves4 ,it was another of the magical wonders of the unknown ,south1 and as such it formed the basis of many a 8wild surmise0 and many a sea-dog's yarn4 ,scientific investigation has not diminished its prestige1 and today no traveler in the southern hemisphere is indifferent to its fascinating strangeness1 while some find it the most impressive spectacle of the antarctic heavens4 ,all around1 up to the very edge of the yawning gap1 the sheen of the ,milky ,way is surpassingly glorious2 but there1 as if in obedience to an almighty edict1 everything vanishes4 ,a single faint star is visible within the opening1 producing a curious effect upon the sensitive spectator1 like the sight of a tiny islet in the midst of a black1 motionless1 waveless tarn4 ,the dimensions of the lagoon of darkness1 which is oval or pear-shaped1 are eight degrees by five1 so that it occupies a space in the sky about one hundred and thirty times greater than the area of the full moon4 ,it attracts attention as soon as the eye is directed toward the quarter where it exists1 and by virtue of the rarity of such phenomena it appears a far greater wonder than the drifts of stars that are heaped around it4 ,now that observatories are multiplying in the southern hemisphere1 the great austral 8,coal-sack0 will1 no doubt1 receive attention proportioned to its importance as one of the most significant features of the sky4 ,already at the ,sydney ,observatory photographs have shown that the southern portion of this ,dead ,sea of ,space is not quite 8bottomless10 although its northern part defies the longest sounding lines of the astronomer4 ,there is a similar1 but less perfect1 8coal-sack0 in the northern hemisphere1 in the constellation of 8,the ,swan10 which1 strange to say1 also contains a well-marked figure of a cross outlined by stars4 ,this gap lies near the top of the cross-shaped figure4 ,it is best seen by averted vision1 which brings out the contrast with the ,milky ,way1 which is quite brilliant around it4 ,it does not1 however1 exercise the same weird attraction upon the eye as the southern 8,coal-sack10 for instead of looking like an absolute void in the sky1 it rather appears as if a canopy of dark gauze had been drawn over the stars4 ,we shall see the possible significance of this appearance later4 ,illustration3 ,the ,milky ,way4 ,region near ,m4,s4 ,photographed by ,professor ,barnard ,just above the southern horizon of our northern middle latitudes1 in summer1 where the ,milky ,way breaks up into vast sheets of nebulous luminosity1 lying over and between the constellations ,scorpio and ,sagittarius1 there is a remarkable assemblage of 8coal-sacks10 though none is of great size4 ,one of them1 near a conspicuous star-cluster in ,scorpio1 ,m#hj1 is interesting for having been the first of these strange objects noted by ,herschel4 ,probably it was its nearness to ,m#hj which suggested to his mind the apparent connection of such vacancies with star-clusters which we have already mentioned4 ,but the most marvelous of the 8coal-sacks0 are those that have been found by photography in ,sagittarius4 ,one of ,barnard's earliest and most excellent photographs includes two of them1 both in the star-cluster ,m#h4 ,the larger1 which is roughly rectangular in outline1 contains one little star1 and its smaller neighbor is lune-shaped--surely a most singular form for such an object4 ,both are associated with curious dark lanes running through the clustered stars like trails in the woods4 ,along the borders of these lanes the stars are ranked in parallel rows1 and what may be called the bottoms of the lanes are not entirely dark1 but pebbled with faint stellar points4 ,one of them which skirts the two dark gaps and traverses the cluster along its greatest diameter is edged with lines of stars1 recalling the alignment of the trees bordering a ,french highway4 ,this road of stars cannot be less than many billions of miles in length6 ,all about the cluster the bed of the ,galaxy is strangely disturbed1 and in places nearly denuded1 as if its contents had been raked away to form the immense stack and the smaller accumulations of stars around it4 ,the well-known 8,trifid ,nebula0 is also included in the field of the photograph1 which covers a truly marvelous region1 so intricate in its mingling of nebul1 star-clusters1 star-swarms1 star-streams1 and dark vacancies that no description can do it justice4 ,yet1 chaotic as it appears1 there is an unmistakable suggestion of unity about it1 impressing the beholder with the idea that all the different parts are in some way connected1 and have not been fortuitously thrown together4 ,miss ,agnes ,m4 ,clerke made the striking remark that the dusky lanes in ,m#h are exemplified on the largest scale in the great rift dividing the ,milky ,way1 from ,cygnus in the northern hemisphere all the way to the 8,cross0 in the southern4 ,similar lanes are found in many other clusters1 and they are generally associated with flanking rows of stars1 resembling in their arrangement the thick-set houses and villas along the roadways that traverse the approaches to a great city4 ,but to return to the black gaps4 ,are they really windows in the star-walls of the universe8 ,some of them look rather as if they had been made by a shell fired through a luminous target1 allowing the eye to range through the hole into the void space beyond4 ,if science is discretely silent about these things1 what can the more venturesome and less responsible imagination suggest8 ,would a huge 8runaway sun10 like ,arcturus1 for instance1 make such an opening if it should pass like a projectile through the ,milky ,way8 ,it is at least a stimulating inquiry4 ,being probably many thousands of times more massive than the galactic stars1 such a stellar missile would not be stopped by them1 though its direction of flight might be altered4 ,it would drag the small stars lying close to its course out of their spheres1 but the ultimate tendency of its attraction would be to sweep them round in its wake1 thus producing rather a star-swarm than a vacancy4 ,those that were very close to it might be swept away in its rush and become its satellites1 careering away with it in its flight into outer space2 but those that were farther off1 and they would1 of course1 greatly outnumber the nearer ones1 would tend inward from all sides toward the line of flight1 as dust and leaves collect behind a speeding motor 7though the forces operating would be different71 and would fill up the hole1 if hole it were4 ,a swarm thus collected should be rounded in outline and bordered with a relatively barren ring from which the stars had been 8sucked0 away4 ,in a general sense the ,m#h cluster answers to this description1 but even if we undertook to account for its existence by a supposition like the above1 the black gaps would remain unexplained1 unless one could make a further draft on the imagination and suggest that the stars had been thrown into a vast eddy1 or system of eddies1 whose vortices appear as dark holes4 ,only a maelstrom-like motion could keep such a funnel open1 for without regard to the impulse derived from the projectile1 the proper motions of the stars themselves would tend to fill it4 ,perhaps some other cause of the whirling motion may be found4 ,as we shall see when we come to the spiral nebul1 gyratory movements are exceedingly prevalent throughout the universe1 and the structure of the ,milky ,way is everywhere suggestive of them4 ,but this is hazardous sport even for the imagination--to play with suns as if they were but thistle-down in the wind or corks in a mill-race4 ,another question arises3 ,what is the thickness of the hedge of stars through which the holes penetrate8 ,is the depth of the openings proportionate to their width8 ,in other words1 is the ,milky ,way round in section like a rope1 or flat and thin like a ribbon8 ,the answer is not obvious1 for we have little or no information concerning the relative distances of the faint galactic stars4 ,it would be easier1 certainly1 to conceive of openings in a thin belt than in a massive ring1 for in the first case they would resemble mere rifts and breaks1 while in the second they would be like wells or bore-holes4 ,then1 too1 the fact that the ,milky ,way is not a continuous body but is made up of stars whose actual distances apart is great1 offers another quandary2 persistent and sharply bordered apertures in such an assemblage are a priori as improbable1 if not impossible1 as straight1 narrow holes running through a swarm of bees4 ,the difficulty of these questions indicates one of the reasons why it has been suggested that the seeming gaps1 or many of them1 are not openings at all1 but opaque screens cutting off the light from stars behind them4 ,that this is quite possible in some cases is shown by ,barnard's later photographs1 particularly those of the singular region around the star ,rho ,ophiuchi4 ,here are to be seen somber lanes and patches1 apparently forming a connected system which covers an immense space1 and which their discoverer thinks may constitute a 8dark nebula40 ,this seems at first a startling suggestion2 but1 after all1 why should their not be dark nebul as well as visible ones8 ,in truth1 it has troubled some astronomers to explain the luminosity of the bright nebul1 since it is not to be supposed that matter in so diffuse a state can be incandescent through heat1 and phosphorescent light is in itself a mystery4 ,the supposition is also in accord with what we know of the existence of dark solid bodies in space4 ,many bright stars are accompanied by obscure companions1 sometimes as massive as themselves2 the planets are non-luminous2 the same is true of meteors before they plunge into the atmosphere and become heated by friction2 and many plausible reasons have been found for believing that space contains as many obscure as shining bodies of great size4 ,it is not so difficult1 after all1 then1 to believe that there are immense collections of shadowy gases and meteoric dust whose presence is only manifested when they intercept the light coming from shining bodies behind them4 ,this would account for the apparent extinguishment of light in open space1 which is indicated by the falling off in relative number of telescopic stars below the tenth magnitude4 ,even as things are1 the amount of light coming to us from stars too faint to be seen with the naked eye is so great that the statement of it generally surprises persons who are unfamiliar with the inner facts of astronomy4 ,it has been calculated that on a clear night the total starlight from the entire celestial sphere amounts to one-sixtieth of the light of the full moon2 but of this less than one-twenty-fifth is due to stars separately distinguished by the eye4 ,if there were no obscuring medium in space1 it is probable that the amount of starlight would be noticeably and perhaps enormously increased4 ,but while it seems certain that some of the obscure spots in the ,milky ,way are due to the presence of 8dark nebul10 or concealing veils of one kind or another1 it is equally certain that there are many which are true apertures1 however they may have been formed1 and by whatever forces they may be maintained4 ,these1 then1 are veritable windows of the ,galaxy1 and when looking out of them one is face to face with the great mystery of infinite space4 ,there the known universe visibly ends1 but manifestly space itself does not end there4 ,it is not within the power of thought to conceive an end to space1 for the instant we think of a terminal point or line the mind leaps forward to the beyond4 ,there must be space outside as well as inside4 ,eternity of time and infinity of space are ideas that the intellect cannot fully grasp1 but neither can it grasp the idea of a limitation to either space or time4 ,the metaphysical conceptions of hypergeometry1 or fourth-dimensional space1 do not aid us4 ,having1 then1 discovered that the universe is a thing contained in something indefinitely greater than itself2 having looked out of its windows and found only the gloom of starless night outside--what conclusions are we to draw concerning the beyond8 ,it seems as empty as a vacuum1 but is it really so8 ,if it be1 then our universe is a single atom astray in the infinite2 it is the only island in an ocean without shores2 it is the one oasis in an illimitable desert4 ,then the ,milky ,way1 with its wide-flung garland of stars1 is afloat like a tiny smoke-wreath amid a horror of immeasurable vacancy1 or it is an evanescent and solitary ring of sparkling froth cast up for a moment on the viewless billows of immensity4 ,from such conclusions the mind instinctively shrinks4 ,it prefers to think that there is something beyond1 though we cannot see it4 ,even the universe could not bear to be alone--a ,crusoe lost in the ,cosmos6 ,as the inhabitants of the most elegant chteau1 with its gardens1 parks1 and crowds of attendants1 would die of loneliness if they did not know that they have neighbors1 though not seen1 and that a living world of indefinite extent surrounds them1 so we1 when we perceive that the universe has limits1 wish to feel that it is not solitary2 that beyond the hedges and the hills there are other centers of life and activity4 ,could anything be more terrible than the thought of an isolated universe8 ,the greater the being1 the greater the aversion to seclusion4 ,only the infinite satisfies2 in that alone the mind finds rest4 ,we are driven1 then1 to believe that the universal night which envelopes us is not tenantless2 that as we stare out of the star-framed windows of the ,galaxy and see nothing but uniform blackness1 the fault is with our eyes or is due to an obscuring medium4 ,since our universe is limited in extent1 there must be other universes beyond it on all sides4 ,perhaps if we could carry our telescopes to the verge of the great 8,coal-sack0 near the 8,cross10 being then on the frontier of our starry system1 we could discern1 sparkling afar off in the vast night1 some of the outer galaxies4 ,they may be grander than ours1 just as many of the suns surrounding us are immensely greater than ours4 ,if we could take our stand somewhere in the midst of immensity and1 with vision of infinite reach1 look about us1 we should perhaps see a countless number of stellar systems1 amid which ours would be unnoticeable1 like a single star among the multitude glittering in the terrestial sky on a clear night4 ,some might be in the form of a wreath1 like our own2 some might be globular1 like the great star-clusters in ,hercules and ,centaurus2 some might be glittering circles1 or disks1 or rings within rings4 ,if we could enter them we should probably find a vast variety of composition1 including elements unknown to terrestrial chemistry2 for while the visible universe appears to contain few if any substances not existing on the earth or in the sun1 we have no warrant to assume that others may not exist in infinite space4 ,and how as to gravitation8 ,we do not know that gravitation acts beyond the visible universe1 but it is reasonable to suppose that it does4 ,at any rate1 if we let go its sustaining hand we are lost1 and can only wander hopelessly in our speculations1 like children astray4 ,if the empire of gravitation is infinite1 then the various outer systems must have some1 though measuring by our standards an imperceptible1 attractive influence upon each other1 for gravitation never lets go its hold1 however great the space over which it is required to act4 ,just as the stars about us are all in motion1 so the starry systems beyond our sight may be in motion1 and our system as a whole may be moving in concert with them4 ,if this be so1 then after interminable ages the aspect of the entire system of systems must change1 its various members assuming new positions with respect to one another4 ,in the course of time we may even suppose that our universe will approach relatively close to one of the others2 and then1 if men are yet living on the earth1 they may glimpse through the openings which reveal nothing to us now1 the lights of another nearing star system1 like the signals of a strange squadron1 bringing them the assurance 7which can be but an inference at present7 that the ocean of space has other argosies venturing on its limitless expanse4 ,there remains the question of the luminiferous ether by whose agency the waves of light are borne through space4 ,the ether is as mysterious as gravitation4 ,with regard to ether we only infer its existence from the effects which we ascribe to it4 ,evidently the ether must extend as far as the most distant visible stars4 ,but does it continue on indefinitely in outer space8 ,if it does1 then the invisibility of the other systems must be due to their distance diminishing the quantity of light that comes from them below the limit of perceptibility1 or to the interposition of absorbing media2 if it does not1 then the reason why we cannot see them is owing to the absence of a means of conveyance for the light waves1 as the lack of an interplanetary atmosphere prevents us from hearing the thunder of sun-spots4 7,it is interesting to recall that ,mr ,edison was once credited with the intention to construct a gigantic microphone which should render the roar of sun-spots audible by transforming the electric vibrations into sound-waves74 ,on this supposition each starry system would be enveloped in its own globule of ether1 and no light could cross from one to another4 ,but the probability is that both the ether and gravitation are ubiquitous1 and that all the stellar systems are immersed in the former like clouds of phosphorescent organisms in the sea4 ,so astronomy carries the mind from height to greater height4 ,men were long in accepting the proofs of the relative insignificance of the earth2 they were more quickly convinced of the comparative littleness of the solar system2 and now the evidence assails their reason that what they had regarded as the universe is only one mote gleaming in the sunbeams of ,infinity4 ,,ii ,star-,clouds1 ,star-,clusters1 and ,star-,streams ,in the preceding chapter we have seen something of the strangely complicated structure of the ,galaxy1 or ,milky ,way4 ,we now proceed to study more comprehensively that garlanded 8,pathway of the ,gods40 ,judged by the eye alone1 the ,milky ,way is one of the most delicately beautiful phenomena in the entire realm of nature--a shimmer of silvery gauze stretched across the sky2 but studied in the light of its revelations1 it is the most stupendous object presented to human ken4 ,let us consider1 first1 its appearance to ordinary vision4 ,its apparent position in the sky shifts according to the season4 ,on a serene1 cloudless summer evening1 in the absence of the moon1 whose light obscures it1 one sees the ,galaxy spanning the heavens from north to southeast of the zenith like a phosphorescent arch4 ,in early spring it forms a similar but1 upon the whole1 less brilliant arch west of the zenith4 ,between spring and summer it lies like a long1 faint1 twilight band along the northern horizon4 ,at the beginning of winter it again forms an arch1 this time spanning the sky from east to west1 a little north of the zenith4 ,these are its positions as viewed from the mean latitude of the ,united ,states4 ,even the beginner in star-gazing does not have to watch it throughout the year in order to be convinced that it is1 in reality1 a great circle1 extending entirely around the celestial sphere4 ,we appear to be situated near its center1 but its periphery is evidently far away in the depths of space4 ,although to the casual observer it seems but a delicate scarf of light1 brighter in some places than in others1 but hazy and indefinite at the best1 such is not its appearance to those who study it with care4 ,they perceive that it is an organic whole1 though marvelously complex in detail4 ,the telescope shows that it consists of stars too faint and small through excess of distance to be separately visible4 ,of the hundred million suns which some estimates have fixed as the probable population of the starry universe1 the vast majority 7at least thirty to one7 are included in this strange belt of misty light4 ,but they are not uniformly distributed in it2 on the contrary1 they are arrayed in clusters1 knots1 bunches1 clouds1 and streams4 ,the appearance is somewhat as if the ,galaxy consisted of innumerable swarms of silver-winged bees1 more or less intermixed1 some massed together1 some crossing the paths of others1 but all governed by a single purpose which leads them to encircle the region of space in which we are situated4 ,from the beginning of the systematic study of the heavens1 the fact has been recognized that the form of the ,milky ,way denotes the scheme of the sidereal system4 ,at first it was thought that the shape of the system was that of a vast round disk1 flat like a cheese1 and filled with stars1 our sun and his relatively few neighbors being placed near the center4 ,according to this view1 the galactic belt was an effect of perspective2 for when looking in the direction of the plane of the disk1 the eye ranged through an immense extension of stars which blended into a glimmering blur1 surrounding us like a ring2 while when looking out from the sides of the disk we saw but few stars1 and in those directions the heavens appeared relatively blank4 ,finally it was recognized that this theory did not correspond with the observed appearances1 and it became evident that the ,milky ,way was not a mere effect of perspective1 but an actual band of enormously distant stars1 forming a circle about the sphere1 the central opening of the ring 7containing many scattered stars7 being many times broader than the width of the ring itself4 ,our sun is one of the scattered stars in the central opening4 ,as already remarked1 the ring of the ,galaxy is very irregular1 and in places it is partly broken4 ,with its sinuous outline1 its pendant sprays1 its graceful and accordant curves1 its bunching of masses1 its occasional interstices1 and the manifest order of a general plan governing the jumble of its details1 it bears a remarkable resemblance to a garland--a fact which appears the more wonderful when we recall its composition4 ,that an elm-tree should trace the lines of beauty with its leafy and pendulous branches does not surprise us2 but we can only gaze with growing amazement when we behold a hundred million suns imitating the form of a chaplet6 ,and then we have to remember that this form furnishes the ground-plan of the universe4 ,as an indication of the extraordinary speculations to which the mystery of the ,milky ,way has given rise1 a theory recently 7#aiji7 proposed by ,prof4 ,george ,c4 ,comstock may be mentioned4 ,starting with the data 7first7 that the number of stars increases as the ,milky ,way is approached1 and reaches a maximum in its plane1 while on the other hand the number of nebul is greatest outside the ,milky ,way and increases with distance from it1 and 7second7 that the ,milky ,way1 although a complete ring1 is broad and diffuse on one side through one-half its course--that half alone containing nebul--and relatively narrow and well defined on the opposite side1 the author of this singular speculation avers that these facts can best be explained by supposing that the invisible universe consists of two interpenetrating parts1 one of which is a chaos of indefinite extent1 strewn with stars and nebulous dust1 and the other a long1 broad but comparatively thin cluster of stars1 including the sun as one of its central members4 ,this flat star-cluster is conceived to be moving edgewise through the chaos1 and1 according to ,professor ,comstock1 it acts after the manner of a snow-plough sweeping away the cosmic dust and piling it on either hand above and below the plane of the moving cluster4 ,it thus forms a transparent rift1 through which we see farther and command a view of more stars than through the intensified dust-clouds on either hand4 ,this rift is the ,milky ,way4 ,the dust thrown aside toward the poles of the ,milky ,way is the substance of the nebul which abound there4 ,ahead1 where the front of the star-plough is clearing the way1 the chaos is nearer at hand1 and consequently there the rift subtends a broader angle1 and is filled with primordial dust1 which1 having been annexed by the vanguard of the star-swarm1 forms the nebul seen only in that part of the ,milky ,way4 ,but behind1 the rift appears narrow because there we look farther away between dust-clouds produced ages ago by the front of the plough1 and no scattered dust remains in that part of the rift4 ,in quoting an outline of this strikingly original theory the present writer should not be understood as assenting to it4 ,that it appears bizarre is not1 in itself1 a reason for rejecting it1 when we are dealing with so problematical and enigmatical a subject as the ,milky ,way2 but the serious objection is that the theory does not sufficiently accord with the observed phenomena4 ,there is too much evidence that the ,milky ,way is an organic system1 however fantastic its form1 to permit the belief that it can only be a rift in chaotic clouds4 ,as with every organism1 we find that its parts are more or less clearly repeated in its ensemble4 ,among all the strange things that the ,milky ,way contains there is nothing so extraordinary as itself4 ,every astronomer must many times have found himself marveling at it in those comparatively rare nights when it shows all its beauty and all its strangeness4 ,in its great broken rifts1 divisions1 and spirals are found the gigantic prototypes of similar forms in its star-clouds and clusters4 ,as we have said1 it determines the general shape of the whole sidereal system4 ,some of the brightest stars in the sky appear to hang like jewels suspended at the ends of tassels dropped from the ,galaxy4 ,among these pendants are the ,pleiades and the ,hyades4 ,orion1 too1 the 8,mighty ,hunter10 is caught in 8a loop of light0 thrown out from it4 ,the majority of the great first-magnitude stars seem related to it1 as if they formed an inner ring inclined at an angle of some twenty degrees to its plane4 ,many of the long curves that set off from it on both sides are accompanied by corresponding curves of lucid stars4 ,in a word1 it offers every appearance of structural connection with the entire starry system4 ,that the universe should have assumed the form of a wreath is certainly a matter for astonishment2 but it would have been still more astonishing if it had been a cube1 a rhomboid1 or a dodecahedron1 for then we should have had to suppose that something resembling the forces that shape crystals had acted upon the stars1 and the difficulty of explaining the universe by the laws of gravitation would have been increased4 ,from the ,milky ,way as a whole we pass to the vast clouds1 swarms1 and clusters of stars of which it is made up4 ,it may be1 as some astronomers hold1 that most of the galactic stars are much smaller than the sun1 so that their faintness is not due entirely to the effect of distance4 ,still1 their intrinsic brilliance attests their solar character1 and considering their remoteness1 which has been estimated at not less than ten thousand to twenty thousand light-years 7a light-year is equal to nearly six thousand thousand million miles7 their actual masses cannot be extremely small4 ,the minutest of them are entitled to be regarded as real suns1 and they vary enormously in magnitude4 ,the effects of their attractions upon one another can only be inferred from their clustering1 because their relative movements are not apparent on account of the brevity of the observations that we can make4 ,but imagine a being for whom a million years would be but as a flitting moment2 to him the ,milky ,way would appear in a state of ceaseless agitation--swirling with 8a fury of whirlpool motion40 ,the cloud-like aspect of large parts of the ,galaxy must always have attracted attention1 even from naked-eye observers1 but the true star-clouds were first satisfactorily represented in ,barnard's photographs4 ,the resemblance to actual clouds is often startling4 ,some are close-packed and dense1 like cumuli2 some are wispy or mottled1 like cirri4 ,the rifts and modulations1 as well as the general outlines1 are the same as those of clouds of vapor or dust1 and one notices also the characteristic thinning out at the edges4 ,but we must beware of supposing that the component suns are thickly crowded as the particles forming an ordinary cloud4 ,they look1 indeed1 as if they were matted together1 because of the irradiation of light1 but in reality millions and billions of miles separate each star from its neighbors4 ,nevertheless they form real assemblages1 whose members are far more closely related to one another than is our sun to the stars around him1 and if we were in the ,milky ,way the aspect of the nocturnal sky would be marvelously different from its present appearance4 ,stellar clouds are characteristic of the ,galaxy and are not found beyond its borders1 except in the 8,magellanic ,clouds0 of the southern hemisphere1 which resemble detached portions of the ,milky ,way4 ,these singular objects form as striking a peculiarity of the austral heavens as does the great 8,coal-sack0 described in ,chapter #a4 ,but it is their isolation that makes them so remarkable1 for their composition is essentially galactic1 and if they were included within its boundaries they would not appear more wonderful than many other parts of the ,milky ,way4 ,placed where they are1 they look like masses fallen from the great stellar arch4 ,they are full of nebul and star-clusters1 and show striking evidences of spiral movement4 ,star-swarms1 which are also characteristic features of the ,galaxy1 differ from star-clouds very much in the way that their name would imply--i4e41 their component stars are so arranged1 even when they are countless in number1 that the idea of an exceedingly numerous assemblage rather than that of a cloud is impressed on the observer's mind4 ,in a star-swarm the separate members are distinguishable because they are either larger or nearer than the stars composing a 8cloud40 ,a splendid example of a true star-swarm is furnished by ,chi ,persei1 in that part of the ,milky ,way which runs between the constellations ,perseus and ,cassiopeia4 ,this swarm is much coarser than many others1 and can be seen by the naked eye4 ,in a small telescope it appears double1 as if the suns composing it had divided into two parties which keep on their way side by side1 with some commingling of their members where the skirts of the two companies come in contact4 ,smaller than either star-clouds or star-swarms1 and differing from both in their organization1 are star-clusters4 ,these1 unlike the others1 are found outside as well as inside the ,milky ,way1 although they are more numerous inside its boundaries than elsewhere4 ,the term star-cluster is sometimes applied1 though improperly1 to assemblages which are rather groups1 such1 for instance1 as the ,pleiades4 ,in their most characteristic aspect star-clusters are of a globular shape--globes of suns6 ,a famous example of a globular star-cluster1 but one not included in the ,milky ,way1 is the 8,great ,cluster in ,hercules40 ,this is barely visible to the naked eye1 but a small telescope shows its character1 and in a large one it presents a marvelous spectacle4 ,photographs of such clusters are1 perhaps1 less effective than those of star-clouds1 because the central condensation of stars in them is so great that their light becomes blended in an indistinguishable blur4 ,the beautiful effect of the incessant play of infinitesimal rays over the apparently compact surface of the cluster1 as if it were a globe of the finest frosted silver shining in an electric beam1 is also lost in a photograph4 ,still1 even to the eye looking directly at the cluster through a powerful telescope1 the central part of the wonderful congregation seems almost a solid mass in which the stars are packed like the ice crystals in a snowball4 ,the same question rises to the lips of every observer3 ,how can they possibly have been brought into such a situation8 ,the marvel does not grow less when we know that1 instead of being closely compacted1 the stars of the cluster are probably separated by millions of miles2 for we know that their distances apart are slight as compared with their remoteness from the ,earth4 ,sir ,william ,herschel estimated their number to be about fourteen thousand1 but in fact they are uncountable4 ,if we could view them from a point just within the edge of the assemblage1 they would offer the appearance of a hollow hemisphere emblazoned with stars of astonishing brilliancy2 the near-by ones unparalleled in splendor by any celestial object known to us1 while the more distant ones would resemble ordinary stars4 ,an inhabitant of the cluster would not know1 except by a process of ratiocination1 that he was dwelling in a globular assemblage of suns2 only from a point far outside would their spherical arrangement become evident to the eye4 ,imagine fourteen-thousand fire-balloons with an approach to regularity in a spherical space--say1 ten miles in diameter2 there would be an average of less than thirty in every cubic mile1 and it would be necessary to go to a considerable distance in order to see them as a globular aggregation2 yet from a point sufficiently far away they would blend into a glowing ball4 ,illustration3 ,star-cluster in ,hercules 7,photographed with a two-foot reflector7 ,photographs show even better than the best telescopic views that the great cluster is surrounded with a multitude of dispersed stars1 suggestively arrayed in more or less curving lines1 which radiate from the principle mass1 with which their connection is manifest4 ,these stars1 situated outside the central sphere1 look somewhat like vagrant bees buzzing round a dense swarm where the queen bee is sitting4 ,yet while there is so much to suggest the operation of central forces1 bringing and keeping the members of the cluster together1 the attentive observer is also impressed with the idea that the whole wonderful phenomenon may be the result of explosion4 ,as soon as this thought seizes the mind1 confirmation of it seems to be found in the appearance of the outlying stars1 which could be as readily explained by the supposition that they have been blown apart as that they have flocked together toward a center4 ,the probable fact that the stars constituting the cluster are very much smaller than our sun might be regarded as favoring the hypothesis of an explosion4 ,of their real size we know nothing1 but1 on the basis of an uncertain estimate of their parallax1 it has been calculated that they may average forty-five thousand miles in diameter--something more than half the diameter of the planet ,jupiter4 ,assuming the same mean density1 fourteen thousand such stars might have been formed by the explosion of a body about twice the size of the sun4 ,this recalls the theory of ,olbers1 which has never been altogether abandoned or disproved1 that the ,asteroids were formed by the explosion of a planet circulating between the orbits of ,mars and ,jupiter4 ,the ,asteroids1 whatever their manner of origin1 form a ring around the sun2 but1 of course1 the explosion of a great independent body1 not originally revolving about a superior center of gravitational force1 would not result in the formation of a ring of small bodies1 but rather of a dispersed mass of them4 ,but back of any speculation of this kind lies the problem1 at present insoluble3 ,how could the explosion be produced8 7,see the question of explosions in ,chapters #f and #ad74 ,then1 on the other hand1 we have the observation of ,herschel1 since abundantly confirmed1 that space is unusually vacant in the immediate neighborhood of condensed star-clusters and nebul1 which1 as far as it goes1 might be taken as an indication that the assembled stars had been drawn together by their mutual attractions1 and that the tendency to aggregation is still bringing new members toward the cluster4 ,but in that case there must have been an original condensation of stars at that point in space4 ,this could probably have been produced by the coagulation of a great nebula into stellar nuclei1 a process which seems now to be taking place in the ,orion ,nebula4 ,illustration3 ,great southern star-cluster1 ,omega ,centauri ,a yet more remarkable globular star-cluster exists in the southern hemisphere1 ,omega ,centauri4 ,in this case the central condensation of stars presents an almost uniform blaze of light4 ,like the ,hercules cluster1 that in ,centaurus is surrounded with stars scattered over a broad field and showing an appearance of radial arrangement4 ,in fact1 except for its greater richness1 ,omega ,centauri is an exact duplicate of its northern rival4 ,each appears to an imaginative spectator as a veritable 8city of suns40 ,mathematics shrinks from the task of disentangling the maze of motions in such an assemblage4 ,it would seem that the chance of collisions is not to be neglected1 and this idea finds a certain degree of confirmation in the appearance of 8temporary stars0 which have more than once blazed out in1 or close by1 globular star-clusters4 ,this leads up to the notable fact1 first established by ,professor ,bailey a few years ago1 that such clusters are populous with variable stars4 ,omega ,centauri and the ,hercules cluster are especially remarkable in this respect4 ,the variables found in them are all of short period and the changes of light show a noteworthy tendency to uniformity4 ,the first thought is that these phenomena must be due to collisions among the crowded stars1 but1 if so1 the encounters cannot be between the stars themselves1 but probably between stars and meteor swarms revolving around them4 ,such periodic collisions might go on for ages without the meteors being exhausted by incorporation with the stars4 ,this explanation appears all the more probable because one would naturally expect that flocks of meteors would abound in a close aggregation of stars4 ,it is also consistent with ,perrine's discovery--that the globular star clusters are powdered with minute stars strewn thickly among the brighter ones4 ,in speaking of ,professor ,comstock's extraordinary theory of the ,milky ,way1 the fact was mentioned that1 broadly speaking1 the nebul are less numerous in the galactic belt than in the comparatively open spaces on either side of it1 but that they are1 nevertheless1 abundant in the broader half of the ,milky ,way which he designates as the front of the gigantic 8plough0 supposed to be forcing its way through the enveloping chaos4 ,in and around the ,sagittarius region the intermingling of nebul and galactic star clouds and clusters is particularly remarkable4 ,that there is a causal connection no thoughtful person can doubt4 ,we are unable to get away from the evidence that a nebula is like a seed-ground from which stars spring forth2 or we may say that nebul resemble clouds in whose bosom raindrops are forming4 ,the wonderful aspect of the admixtures of nebul and star-clusters in ,sagittarius has been described in ,chapter #a4 ,we now come to a still more extraordinary phenomenon of this kind--the ,pleiades nebul4 ,illustration3 ,the ,pleiades ,the group of the ,pleiades1 although lying outside the main course of the ,galaxy1 is connected with it by a faint loop1 and is the scene of the most remarkable association of stars and nebulous matter known in the visible universe4 ,the naked eye is unaware of the existence of nebul in the ,pleiades1 or1 at the best1 merely suspects that there is something of the kind there2 and even the most powerful telescopes are far from revealing the full wonder of the spectacle2 but in photographs which have been exposed for many hours consecutively1 in order to accumulate the impression of the actinic rays1 the revelation is stunning4 ,the principle stars are seen surrounded by1 and1 as it were1 drowned in1 dense nebulous clouds of an unparalleled kind4 ,the forms assumed by these clouds seem at first sight inexplicable4 ,they look like fleeces1 or perhaps more like splashes and daubs of luminous paint dashed carelessly from a brush4 ,but closer inspection shows that they are1 to a large extent1 woven out of innumerable threads of filmy texture1 and there are many indications of spiral tendencies4 ,each of the bright stars of the group--,alcyone1 ,merope1 ,maia1 ,electra1 ,taygeta1 ,atlas--is the focus of a dense fog 7totally invisible1 remember1 alike to the naked eye and to the telescope71 and these particular stars are veiled from sight behind the strange mists4 ,running in all directions across the relatively open spaces are nebulous wisps and streaks of the most curious forms4 ,on some of the nebular lines1 which are either straight throughout1 or if they change direction do so at an angle1 little stars are strung like beads4 ,in one case seven or eight stars are thus aligned1 and1 as if to emphasize their dependence upon the chain which connects them1 when it makes a slight bend the file of stars turns the same way4 ,many other star rows in the group suggest by their arrangement that they1 too1 were once strung upon similar threads which have now disappeared1 leaving the stars spaced along their ancient tracks4 ,we seem forced to the conclusion that there was a time when the ,pleiades were embedded in a vast nebula resembling that of ,orion1 and that the cloud has now become so rare by gradual condensation into stars that the merest trace of it remains1 and this would probably have escaped detection but for the remarkable actinic power of the radiant matter of which it consists4 ,the richness of many of these faint nebulous masses in ultra-violet radiations1 which are those that specifically affect the photographic plate1 is the cause of the marvelous revelatory power of celestial photography4 ,so the veritable unseen universe1 as distinguished from the 8unseen universe0 of metaphysical speculation1 is shown to us4 ,a different kind of association between stars and nebul is shown in some surprising photographic objects in the constellation ,cygnus1 where long1 wispy nebul1 billions of miles in length1 some of them looking like tresses streaming in a breeze1 lie amid fields of stars which seem related to them4 ,but the relation is of a most singular kind1 for notwithstanding the delicate structure of the long nebul they appear to act as barriers1 causing the stars to heap themselves on one side4 ,the stars are two1 three1 or four times as numerous on one side of the nebul as on the other4 ,these nebul1 as far as appearance goes1 might be likened to rail fences1 or thin hedges1 against which the wind is driving drifts of powdery snow1 which1 while scattered plentifully all around1 tends to bank itself on the leeward side of the obstruction4 ,the imagination is at a loss to account for these extraordinary phenomena2 yet there they are1 faithfully giving us their images whenever the photographic plate is exposed to their radiations4 ,thus the more we see of the universe with improved methods of observation1 and the more we invent aids to human senses1 each enabling us to penetrate a little deeper into the unseen1 the greater becomes the mystery4 ,the telescope carried us far1 photography is carrying us still farther2 but what as yet unimagined instrument will take us to the bottom1 the top1 and the end8 ,and then1 what hitherto untried power of thought will enable us to comprehend the meaning of it all8 ,,iii ,stellar ,migrations ,to the untrained eye the stars and the planets are not distinguishable4 ,it is customary to call them all alike 8stars40 ,but since the planets more or less rapidly change their places in the sky1 in consequence of their revolution about the sun1 while the stars proper seem to remain always in the same relative positions1 the latter are spoken of as 8fixed stars40 ,in the beginnings of astronomy it was not known that the 8fixed stars0 had any motion independent of their apparent annual revolution with the whole sky about the earth as a seeming center4 ,now1 however1 we know that the term 8fixed stars0 is paradoxical1 for there is not a single really fixed object in the whole celestial sphere4 ,the apparent fixity in the positions of the stars is due to their immense distance1 combined with the shortness of the time during which we are able to observe them4 ,it is like viewing the plume of smoke issuing from a steamer1 hull down1 at sea3 if one does not continue to watch it for a long time it appears to be motionless1 although in reality it may be traveling at great speed across the line of sight4 ,even the planets seem fixed in position if one watches them for a single night only1 and the more distant ones do not sensibly change their places1 except after many nights of observation4 ,neptune1 for instance1 moves but little more than two degrees in the course of an entire year1 and in a month its change of place is only about one-third of the diameter of the full moon4 ,yet1 fixed as they seem1 the stars are actually moving with a speed in comparison with which1 in some cases1 the planets might almost be said to stand fast in their tracks4 ,jupiter's speed in his orbit is about eight miles per second1 ,neptune's is less than three and one-half miles1 and the earth's is about eighteen and one-half miles2 while there are 8fixed stars0 which move two hundred or three hundred miles per second4 ,they do not all1 however1 move with so great a velocity1 for some appear to travel no faster than the planets4 ,but in all cases1 notwithstanding their real speed1 long-continued and exceedingly careful observations are required to demonstrate that they are moving at all4 ,no more overwhelming impression of the frightful depths of space in which the stars are buried can be obtained than by reflecting upon the fact that a star whose actual motion across the line of sight amounts to two hundred miles per second does not change its apparent place in the sky1 in the course of a thousand years1 sufficiently to be noticed by the casual observer of the heavens6 ,there is one vast difference between the motions of the stars and those of the planets to which attention should be at once called3 the planets1 being under the control of a central force emanating from their immediate master1 the sun1 all move in the same direction and in orbits concentric about the sun2 the stars1 on the other hand1 move in every conceivable direction and have no apparent center of motion1 for all efforts to discover such a center have failed4 ,at one time1 when theology had finally to accept the facts of science1 a grandiose conception arose in some pious minds1 according to which the ,throne of ,god was situated at the exact center of ,his ,creation1 and1 seated there1 ,he watched the magnificent spectacle of the starry systems obediently revolving around ,him4 ,astronomical discoveries and speculations seemed for a time to afford some warrant for this view1 which was1 moreover1 an acceptable substitute for the abandoned geocentric theory in minds that could only conceive of ,god as a superhuman artificer1 constantly admiring his own work4 ,no longer ago than the middle of the nineteenth century a ,german astronomer1 ,maedler1 believed that he had actually found the location of the center about which the stellar universe revolved4 ,he placed it in the group of the ,pleiades1 and upon his authority an extraordinary imaginative picture was sometimes drawn of the star ,alcyone1 the brightest of the ,pleiades1 as the very seat of the ,almighty4 ,this idea even seemed to gain a kind of traditional support from the mystic significance1 without known historical origin1 which has for many ages1 and among widely separated peoples1 been attached to the remarkable group of which ,alcyone is the chief4 ,but since ,maedler's time it has been demonstrated that the ,pleiades cannot be the center of revolution of the universe1 and1 as already remarked1 all attempts to find or fix such a center have proved abortive4 ,yet so powerful was the hold that the theory took upon the popular imagination1 that even today astronomers are often asked if ,alcyone is not the probable site of 8,jerusalem the ,golden40 ,if there were a discoverable center of predominant gravitative power1 to which the motions of all the stars could be referred1 those motions would appear less mysterious1 and we should then be able to conclude that the universe was1 as a whole1 a prototype of the subsidiary systems of which it is composed4 ,we should look simply to the law of gravitation for an explanation1 and1 naturally1 the center would be placed within the opening enclosed by the ,milky ,way4 ,if it were there the ,milky ,way itself should exhibit signs of revolution about it1 like a wheel turning upon its hub4 ,no theory of the star motions as a whole could stand which failed to take account of the ,milky ,way as the basis of all4 ,but the very form of that divided wreath of stars forbids the assumption of its revolution about a center4 ,even if it could be conceived as a wheel having no material center it would not have the form which it actually presents4 ,as was shown in ,chapter #b1 there is abundant evidence of motion in the ,milky ,way2 but it is not motion of the system as a whole1 but motion affecting its separate parts4 ,instead of all moving one way1 the galactic stars1 as far as their movements can be inferred1 are governed by local influences and conditions4 ,they appear to travel crosswise and in contrary directions1 and perhaps they eddy around foci where great numbers have assembled2 but of a universal revolution involving the entire mass we have no evidence4 ,most of our knowledge of star motions1 called 8proper motions10 relates to individual stars and to a few groups which happen to be so near that the effects of their movements are measurable4 ,in some cases the motion is so rapid 7not in appearance1 but in reality7 that the chief difficulty is to imagine how it can have been imparted1 and what will eventually become of the 8runaways40 ,without a collision1 or a series of very close approaches to great gravitational centers1 a star traveling through space at the rate of two hundred or three hundred miles per second could not be arrested or turned into an orbit which would keep it forever flying within the limits of the visible universe4 ,a famous example of these speeding stars is 8#ahcj ,groombridge10 a star of only the sixth magnitude1 and consequently just visible to the naked eye1 whose motion across the line of sight is so rapid that it moves upon the face of the sky a distance equal to the apparent diameter of the moon every #bhj years4 ,the distance of this star is at least #bjj1jjj1jjj1jjj1jjj miles1 and may be two or three times greater1 so that its actual speed cannot be less than two hundred1 and may be as much as four hundred1 miles per second4 ,it could be turned into a new course by a close approach to a great sun1 but it could only be stopped by collision1 head-on1 with a body of enormous mass4 ,barring such accidents it must1 as far as we can see1 keep on until it has traversed our stellar system1 whence in may escape and pass out into space beyond1 to join1 perhaps1 one of those other universes of which we have spoken4 ,arcturus1 one of the greatest suns in the universe1 is also a runaway1 whose speed of flight has been estimated all the way from fifty to two hundred miles per second4 ,arcturus1 we have every reason to believe1 possesses hundreds of times the mass of our sun--think1 then1 of the prodigious momentum that its motion implies6 ,sirius moves more moderately1 its motion across the line of sight amounting to only ten miles per second1 but it is at the same time approaching the sun at about the same speed1 its actual velocity in space being the resultant of the two displacements4 ,what has been said about the motion of ,sirius brings us to another aspect of this subject4 ,the fact is1 that in every case of stellar motion the displacement that we observe represents only a part of the actual movement of the star concerned4 ,there are stars whose motion carries them straight toward or straight away from the earth1 and such stars1 of course1 show no cross motion4 ,but the vast majority are traveling in paths inclined from a perpendicular to our line of sight4 ,taken as a whole1 the stars may be said to be flying about like the molecules in a mass of gas4 ,the discovery of the radial component in the movements of the stars is due to the spectroscope4 ,if a star is approaching1 its spectral lines are shifted toward the violet end of the spectrum by an amount depending upon the velocity of approach2 if it is receding1 the lines are correspondingly shifted toward the red end4 ,spectroscopic observation1 then1 combined with micrometric measurements of the cross motion1 enables us to detect the real movement of the star in space4 ,sometimes it happens that a star's radial movement is periodically reversed2 first it approaches1 and then it recedes4 ,this indicates that it is revolving around a near-by companion1 which is often invisible1 and superposed upon this motion is that of the two stars concerned1 which together may be approaching or receding or traveling across the line of sight4 ,thus the complications involved in the stellar motions are often exceedingly great and puzzling4 ,yet another source of complication exists in the movement of our own star1 the sun4 ,there is no more difficult problem in astronomy than that of disentangling the effects of the solar motion from those of the motions of the other stars4 ,but the problem1 difficult as it is1 has been solved1 and upon its solution depends our knowledge of the speed and direction of the movement of the solar system through space1 for of course the sun carries its planets with it4 ,one element of the solution is found in the fact that1 as a result of perspective1 the stars toward which we are going appear to move apart toward all points of the compass1 while those behind appear to close up together4 ,then the spectroscopic principle already mentioned is invoked for studying the shift of the lines1 which is toward the violet in the stars ahead of us and toward the red in those that we are leaving behind4 ,of course the effects of the independent motions of the stars must be carefully excluded4 ,the result of the studies devoted to this subject is to show that we are traveling at a speed of twelve to fifteen miles per second in a northerly direction1 toward the border of the constellations ,hercules and ,lyra4 ,a curious fact is that the more recent estimates show that the direction is not very much out of a straight line drawn from the sun to the star ,vega1 one of the most magnificent suns in the heavens4 ,but it should not be inferred from this that ,vega is drawing us on2 it is too distant for its gravitation to have such an effect4 ,many unaccustomed thoughts are suggested by this mighty voyage of the solar system4 ,whence have we come1 and whither do we go8 ,every year of our lives we advance at least #cge1jjj1jjj miles4 ,since the traditional time of ,adam the sun has led his planets through the wastes of space no less than #bbe1jjj1jjj1jjj miles1 or more than #bdjj times the distance that separates him from the earth4 ,go back in imagination to the geologic ages1 and try to comprehend the distance over which the earth has flown4 ,where was our little planet when it emerged out of the clouds of chaos8 ,where was the sun when his 8thunder march0 began8 ,what strange constellations shone down upon our globe when its masters of life were the monstrous beasts of the 8,age of ,reptiles08 ,a million years is not much of a span of time in geologic reckoning1 yet a million years ago the earth was farther from its present place in space than any of the stars with a measurable parallax are now4 ,it was more than seven times as far as ,sirius1 nearly fourteen times as far as ,alpha ,centauri1 three times as far as ,vega1 and twice as far as ,arcturus4 ,but some geologists demand two hundred1 three hundred1 even one thousand million years to enable them to account for the evolutionary development of the earth and its inhabitants4 ,in a thousand million years the earth would have traveled farther than from the remotest conceivable depths of the ,milky ,way6 ,other curious reflections arise when we think of the form of the earth's track as it follows the lead of the sun1 in a journey which has neither known beginning nor conceivable end4 ,there are probably many minds which have found a kind of consolation in the thought that every year the globe returns to the same place1 on the same side of the sun4 ,this idea may have an occult connection with our traditional regard for anniversaries4 ,when that period of the year returns at which any great event in our lives has occurred we have the feeling that the earth1 in its annual round1 has1 in a manner1 brought us back to the scene of that event4 ,we think of the earth's orbit as a well-worn path which we traverse many times in the course of a lifetime4 ,it seems familiar to us1 and we grow to have a sort of attachment to it4 ,the sun we are accustomed to regard as a fixed center in space1 like the mill or pump around which the harnessed patient mule makes his endless circuits4 ,but the real fact is that the earth never returns to the place in space where it has once quitted4 ,in consequence of the motion of the sun carrying the earth and the other planets along1 the track pursued by our globe is a vast spiral in space continually developing and never returning upon its course4 ,it is probable that the tracks of the sun and the others stars are also irregular1 and possibly spiral1 although1 as far as can be at present determined1 they appear to be practically straight4 ,every star1 wherever it may be situated1 is attracted by its fellow-stars from many sides at once1 and although the force is minimized by distance1 yet in the course of many ages its effects must become manifest4 ,looked at from another side1 is there not something immensely stimulating and pleasing to the imagination in the idea of so stupendous a journey1 which makes all of us the greatest of travelers8 ,in the course of a long life a man is transported through space thirty thousand million miles2 ,halley's ,comet does not travel one-quarter as far in making one of its immense circuits4 ,and there are adventures on this voyage of which we are just beginning to learn to take account4 ,space is full of strange things1 and the earth must encounter some of them as it advances through the unknown4 ,many singular speculations have been indulged in by astronomers concerning the possible effects upon the earth of the varying state of the space that it traverses4 ,even the alternation of hot and glacial periods has sometimes been ascribed to this source4 ,when tropical life flourished around the poles1 as the remains in the rocks assure us1 the needed high temperature may1 it has been thought1 have been derived from the presence of the earth in a warm region of space4 ,then1 too1 there is a certain interest for us in the thought of what our familiar planet has passed through4 ,we cannot but admire it for its long journeying as we admire the traveler who comes to us from remote and unexplored lands1 or as we gaze with a glow of interest upon the first locomotive that has crossed a continent1 or a ship that has visited the ,arctic or ,antarctic regions4 ,if we may trust the indications of the present course1 the earth1 piloted by the sun1 has come from the ,milky ,way in the far south and may eventually rejoin that mighty band of stars in the far north4 ,while the stars in general appear to travel independently of one another1 except when they are combined in binary or trinary systems1 there are notable exceptions to this rule4 ,in some quarters of the sky we behold veritable migrations of entire groups of stars whose members are too widely separated to show any indications of revolution about a common center of gravity4 ,this leads us back again to the wonderful group of the ,pleiades4 ,all of the principle stars composing that group are traveling in virtually parallel lines4 ,whatever force set them going evidently acted upon all alike4 ,this might be explained by the assumption that when the original projective force acted upon them they were more closely united than they are at present1 and that in drifting apart they have not lost the impulse of the primal motion4 ,or it may be supposed that they are carried along by some current in space1 although it would be exceedingly difficult1 in the present state of our knowledge1 to explain the nature of such a current4 ,yet the theory of a current has been proposed4 ,as to an attractive center around which they might revolve1 none has been found4 ,another instance of similar 8star-drift0 is furnished by five of the seven stars constituting the figure of the 8,great ,dipper40 ,in this case the stars concerned are separated very widely1 the two extreme ones by not less than fifteen degrees1 so that the idea of a common motion would never have been suggested by their aspect in the sky2 and the case becomes the more remarkable from the fact that among and between them there are other stars1 some of the same magnitude1 which do not share their motion1 but are traveling in other directions4 ,still other examples of the same phenomenon are found in other parts of the sky4 ,of course1 in the case of compact star-clusters1 it is assumed that all the members share a like motion of translation through space1 and the same is probably true of dense star-swarms and star-clouds4 ,the whole question of star-drift has lately assumed a new phase1 in consequence of the investigations of ,kapteyn1 ,dyson1 and ,eddington on the 8systematic motions of the stars40 ,this research will1 it is hoped1 lead to an understanding of the general law governing the movements of the whole body of stars constituting the visible universe4 ,taking about eleven hundred stars whose proper motions have been ascertained with an approach to certainty1 and which are distributed in all parts of the sky1 it has been shown that there exists an apparent double drift1 in two independent streams1 moving in different and nearly opposed directions4 ,the apex of the motion of what is called 8,stream ,i0 is situated1 according to ,professor ,kapteyn1 in right ascension #he1 declination south #aa1 which places it just south of the constellation ,orion2 while the apex of 8,stream ,,ii0 is in right ascension #bfj1 declination south #dh1 placing it in the constellation ,ara1 south of ,scorpio4 ,the two apices differ very nearly #ahj in right ascension and about #abj in declination4 ,the discovery of these vast star-streams1 if they really exist1 is one of the most extraordinary in modern astronomy4 ,it offers the correlation of stellar movements needed as the basis of a theory of those movements1 but it seems far from revealing a physical cause for them4 ,as projected against the celestial sphere the stars forming the two opposite streams appear intermingled1 some obeying one tendency and some the other4 ,as ,professor ,dyson has said1 the hypothesis of this double movement is of a revolutionary character1 and calls for further investigation4 ,indeed1 it seems at first glance not less surprising than would be the observation that in a snow-storm the flakes over our heads were divided into two parties and driving across each other's course in nearly opposite directions1 as if urged by interpenetrating winds4 ,but whatever explanation may eventually be found for the motions of the stars1 the knowledge of the existence of those motions must always afford a new charm to the contemplative observer of the heavens1 for they impart a sense of life to the starry system that would otherwise be lacking4 ,a stagnant universe1 with every star fixed immovably in its place1 would not content the imagination or satisfy our longing for ceaseless activity4 ,the majestic grandeur of the evolutions of the celestial hosts1 the inconceivable vastness of the fields of space in which they are executed1 the countless numbers1 the immeasurable distances1 the involved convolutions1 the flocking and the scattering1 the interpenetrating marches and countermarches1 the strange community of impulsion affecting stars that are wide apart in space and causing them to traverse the general movement about them like aides and despatch-bearers on a battle-field--all these arouse an intensity of interest which is heightened by the mystery behind them4 ,,iv ,the ,passing of the ,constellations ,from a historical and picturesque point of view1 one of the most striking results of the motions of the stars described in the last chapter is their effect upon the forms of the constellations1 which have been watched and admired by mankind from a period so early that the date of their invention is now unknown4 ,the constellations are formed by chance combinations of conspicuous stars1 like figures in a kaleidoscope1 and if our lives were commensurate with the ons of cosmic existence we should perceive that the kaleidoscope of the heavens was ceaselessly turning and throwing the stars into new symmetries4 ,even if the stars stood fast1 the motion of the solar system would gradually alter the configurations1 as the elements of a landscape dissolve and recombine in fresh groupings with the traveler's progress amid them4 ,but with the stars themselves all in motion at various speeds and in many directions1 the changes occur more rapidly4 ,of course1 8rapid0 is here understood in a relative sense2 the wheel of human history to an eye accustomed to the majestic progression of the universe would appear to revolve with the velocity of a whirling dynamo4 ,only the deliberation of geological movements can be contrasted with the evolution and devolution of the constellations4 ,and yet this secular fluctuation of the constellation figures is not without keen interest for the meditative observer4 ,it is another reminder of the swift mutability of terrestial affairs4 ,to the passing glance1 which is all that we can bestow upon these figures1 they appear so immutable that they have been called into service to form the most lasting records of ancient thought and imagination that we possess4 ,in the forms of the constellations1 the most beautiful1 and1 in imaginative quality1 the finest1 mythology that the world has ever known has been perpetuated4 ,yet1 in a broad sense1 this scroll of human thought imprinted on the heavens is as evanescent as the summer clouds4 ,although more enduring than parchment1 tombs1 pyramids1 and temples1 it is as far as they from truly eternizing the memory of what man has fancied and done4 ,before studying the effects that the motions of the stars have had and will have upon the constellations1 it is worth while to consider a little further the importance of the stellar pictures as archives of history4 ,to emphasize the importance of these effects it is only necessary to recall that the constellations register the oldest traditions of our race4 ,in the history of primeval religions they are the most valuable of documents4 ,leaving out of account for the moment the more familiar mythology of the ,greeks1 based on something older yet1 we may refer for illustration to that of the mysterious ,maya race of ,america4 ,at ,izamal1 in ,yucatan1 says ,mr ,stansbury ,hagar1 is a group of ruins perched1 after the ,mexican and ,central-,american plan1 on the summits of pyramidal mounds which mark the site of an ancient theogonic center of the ,mayas4 ,here the temples all evidently refer to a cult based upon the constellations as symbols4 ,the figures and the names1 of course1 were not the same as those that we have derived from our ,aryan ancestors1 but the star groups were the same or nearly so4 ,for instance1 the loftiest of the temples at ,izamal was connected with the sign of the constellation known to us as ,cancer1 marking the place of the sun at the summer solstice1 at which period the sun was supposed to descend at noon like a great bird of fire and consume the offerings left upon the altar4 ,our ,scorpio was known to the ,mayas as a sign of the 8,death ,god40 ,our ,libra1 the 8,balance10 with which the idea of a divine weighing out of justice has always been connected1 seems to be identical with the ,mayan constellation ,teoyaotlatohua1 with which was associated a temple where dwelt the priests whose special business it was to administer justice and to foretell the future by means of information obtained from the spirits of the dead4 ,orion1 the 8,hunter0 of our celestial mythology1 was among the ,mayas a 8,warrior10 while ,sagittarius and others of our constellations were known to them 7under different names1 of course71 and all were endowed with a religious symbolism4 ,and the same star figures1 having the same significance1 were familiar to the ,peruvians1 as shown by the temples at ,cuzco4 ,thus the imagination of ancient ,america sought in the constellations symbols of the unchanging gods4 ,but1 in fact1 there is no nation and no people that has not recognized the constellations1 and at one period or another in its history employed them in some symbolic or representative capacity4 ,as handled by the ,greeks from prehistoric times1 the constellation myths became the very soul of poetry4 ,the imagination of that wonderful race idealized the principal star groups so effectively that the figures and traditions thus attached to them have1 for civilized mankind1 displaced all others1 just as ,greek art in its highest forms stands without parallel and eclipses every rival4 ,the ,romans translated no heroes and heroines of the mythical period of their history to the sky1 and the deified ,csars never entered that lofty company1 but the heavens are filled with the early myths of the ,greeks4 ,herakles nightly resumes his mighty labors in the stars2 ,zeus1 in the form of the white 8,bull10 ,taurus1 bears the fair ,europa on his back through the celestial waves2 ,andromeda stretches forth her shackled arms in the star-gemmed ether1 beseeching aid2 and ,perseus1 in a blaze of diamond armor1 revives his heroic deeds amid sparkling clouds of stellar dust4 ,there1 too1 sits ,queen ,cassiopeia in her dazzling chair1 while the ,great ,king1 ,cepheus1 towers gigantic over the pole4 ,professor ,young has significantly remarked that a great number of the constellations are connected in some way or other with the ,argonautic ,expedition--that strangely fascinating legend of earliest ,greek story which has never lost its charm for mankind4 ,in view of all this1 we may well congratulate ourselves that the constellations will outlast our time and the time of countless generations to follow us2 and yet they are very far from being eternal4 ,let us now study some of the effects of the stellar motions upon them4 ,we begin with the familiar figure of the 8,great ,dipper40 ,he who has not drunk inspiration from its celestial bowl is not yet admitted to the circle of ,olympus4 ,this figure is made up of seven conspicuous stars in the constellation ,ursa ,major1 the 8,greater ,bear40 ,the handle of the 8,dipper0 corresponds to the tail of the imaginary 8,bear10 and the bowl lies upon his flank4 ,in fact1 the figure of a dipper is so evident and that of a bear so unevident1 that to most persons the 8,great ,dipper0 is the only part of the constellation that is recognizable4 ,of the seven stars mentioned1 six are of nearly equal brightness1 ranking as of the second magnitude1 while the seventh is of only the third magnitude4 ,the difference is very striking1 since every increase of one magnitude involves an increase of two-and-a-half times in brightness4 ,there appears to be little doubt that the faint star1 which is situated at the junction of the bowl and the handle1 is a variable of long period1 since three hundred years ago it was as bright as its companions4 ,but however that may be1 its relative faintness at the present time interferes but little with the perfection of the 8,dipper's0 figure4 ,in order the more readily to understand the changes which are taking place1 it will be well to mention both the names and the ,greek letters which are attached to the seven stars4 ,beginning at the star in the upper outer edge of the rim of the bowl and running in regular order round the bottom and then out to the end of the handle1 the names and letters are as follows3 ,dubhe 771 ,merak 771 ,phaed 771 ,megrez 771 ,alioth 771 ,mizar 771 and ,benetnasch 774 ,megrez is the faint star already mentioned at the junction of the bowl and handle1 and ,mizar1 in the middle of the handle1 has a close1 naked-eye companion which is named ,alcor4 ,the ,arabs called this singular pair of stars 8,the ,horse and ,rider40 ,merak and ,duhbe are called 8,the ,pointers10 because an imaginary line drawn northward through them indicates the ,pole ,star4 ,illustration3 ,the 8,great ,dipper0 ,now it has been found that five of these stars--viz41 ,merak1 ,phaed1 ,megrez1 ,alioth1 and ,mizar 7with its comrade7--are moving with practically the same speed in an easterly direction1 while the other two1 ,dubhe and ,benetnasch1 are simultaneously moving westward1 the motions of ,benetnasch being apparently more rapid4 ,the consequence of these opposed motions is1 of course1 that the figure of the 8,dipper0 cannot always have existed and will not continue to exist4 ,in the accompanying diagrams it has been thought interesting to show the relative positions of these seven stars1 as seen from the point which the earth now occupies1 both in the past and in the future4 ,arrows attached to the stars in the figure representing the present appearance of the 8,dipper0 indicate the directions of the motions and the distances over which they will carry the stars in a period of about five hundred centuries4 ,the time1 no doubt1 seems long1 but remember the vast stretch of ages through which the earth has passed1 and then reflect that no reason is apparent why our globe should not continue to be a scene of animation for ten thousand centuries yet to come4 ,the fact that the little star ,alcor placed so close to ,mizar should accompany the latter in its flight is not surprising1 but that two of the principal stars of the group should be found moving in a direction directly opposed to that pursued by the other five is surprising in the highest degree2 and it recalls the strange theory of a double drift affecting all the stars1 to which attention was called in the preceding chapter4 ,it would appear that ,benetnasch and ,dubhe belong to one 8current10 and ,merak1 ,phaed1 ,megrez1 ,alioth1 and ,mizar to the other4 ,as far as is known1 the motion of the seven stars are not shared by the smaller stars scattered about them1 but on the theory of currents there should be such a community of motion1 and further investigation may reveal it4 ,illustration3 ,cassiopeia ,from the 8,great ,dipper0 we turn to a constellation hardly less conspicuous and situated at an equal distance from the pole on the other side--,cassiopeia4 ,this famous star-group commemorating the romantic ,queen of ,ethiopia whose vain boasting of her beauty was punished by the exposure of her daughter ,andromeda to the 8,sea ,monster10 is well-marked by five stars which form an irregular letter 8,w0 with its open side toward the pole4 ,three of these stars are usually ranked as of the second magnitude1 and two of the third2 but to ordinary observation they appear of nearly equal brightness1 and present a very striking picture4 ,they mark out the chair and a part of the figure of the beautiful queen4 ,beginning at the right-hand1 or western1 end of the 8,w10 their ,greek letter designations are3 ,beta 771 ,alpha 771 ,gamma 771 ,delta 771 and ,epsilon 774 ,four of them1 ,beta1 ,alpha1 ,delta1 and ,epsilon are traveling eastwardly at various speeds1 while the fifth1 ,gamma1 moves in a westerly direction4 ,the motion of ,beta is more rapid than that of any of the others4 ,it should be said1 however1 that no little uncertainty attaches to the estimates of the rate of motion of stars which are not going very rapidly1 and different observers often vary considerably in their results4 ,in the beautiful 8,northern ,crown10 one of the most perfect and charming of all the figures to be found in the stars1 the alternate combining and scattering effects of the stellar motions are shown by comparing the appearance which the constellation must have had five hundred centuries ago with that which it has at present and that which it will have in the future4 ,the seven principle stars of the asterism1 forming a surprisingly perfect coronet1 have movements in three directions at right angles to one another4 ,that in these circumstances they should ever have arrived at positions giving them so striking an appearance of definite association is certainly surprising2 from its aspect one would have expected to find a community of movement governing the brilliants of the 8,crown10 but instead of that we find evidence that they will inevitably drift apart and the beautiful figure will dissolve4 ,a similar fate awaits such asterisms as the 8,northern ,cross0 in ,cygnus2 the 8,crow0 7,corvus71 which stands on the back of the great 8,sea ,serpent10 ,hydra1 and pecks at his scales2 8,job's ,coffin0 7,delphinus72 the 8,great ,square of ,pegasus02 the 8,twins0 7,gemini72 the beautiful 8,sickle0 in ,leo2 and the exquisite group of the ,hyades in ,taurus4 ,in the case of the ,hyades1 two controlling movements are manifest3 one1 affecting five of the stars which form the well-known figure of a letter 8,v10 is directed northerly2 the other1 which controls the direction of two stars1 has an easterly trend4 ,the chief star of the group1 ,aldebaran1 one of the finest of all stars both for its brilliance and its color1 is the most affected by the easterly motion4 ,in time it will drift entirely out of connection with its present neighbors4 ,although the ,hyades do not form so compact a group as the ,pleiades in the same constellation1 yet their appearance of relationship is sufficient to awaken a feeling of surprise over the fact that1 as with the stars of the 8,dipper10 their association is only temporary or apparent4 ,illustration3 ,the 8,northern ,crown0 ,the great figure of ,orion appears to be more lasting1 not because its stars are physically connected1 but because of their great distance1 which renders their movements too deliberate to be exactly ascertained4 ,two of the greatest of its stars1 ,betelgeuse and ,rigel1 possess1 as far as has been ascertained1 no perceptible motion across the line of sight1 but there is a little movement perceptible in the 8,belt40 ,at the present time this consists of an almost perfect straight line1 a row of second-magnitude stars about equally spaced and of the most striking beauty4 ,in the course of time1 however1 the two right-hand stars1 ,mintaka and ,alnilam 7how fine are these ,arabic star names67 will approach each other and form a naked-eye double1 but the third1 ,alnita1 will drift away eastward1 so that the 8,belt0 will no longer exist4 ,for one more example1 let us go to the southern hemisphere1 whose most celebrated constellation1 the 8,southern ,cross10 has found a place in all modern literatures1 although it has no claim to consideration on account of association with ancient legends4 ,this most attractive asterism1 which has never ceased to fascinate the imagination of ,christendom since it was first devoutly described by the early explorers of the ,south1 is but a passing collocation of brilliant stars4 ,yet even in its transfigurations it has been for hundreds of centuries1 and will continue to be for hundreds of centuries to come1 a most striking object in the sky4 ,our figures show its appearance in three successive phases3 first1 as it was fifty thousand years ago 7viewed from the earth's present location72 second1 as it is in our day2 and1 third1 as it will be an equal time in the future4 ,the nearness of these bright stars to one another--the length of the longer beam of the 8,cross0 is only sixdegrees--makes this group very noticeable1 whatever the arrangement of its components may be4 ,the largest star1 at the base of the 8,cross10 is of the first magnitude1 two of the others are of the second magnitude1 and the fourth is of the third4 ,other stars1 not represented in the figures1 increase the effect of a celestial blazonry1 although they do not help the resemblance to a cross4 ,illustration3 ,the 8,southern ,cross0 ,but since the motion of the solar system itself will1 in the course of so long a period as fifty thousand years1 produce a great change in the perspective of the heavens as seen from the earth1 by carrying us nearly nineteen trillion miles from our present place1 why1 it may be asked1 seek to represent future appearances of the constellations which we could not hope to see1 even if we could survive so long8 ,the answer is3 ,because these things aid the mind to form a picture of the effects of the mobility of the starry universe4 ,only by showing the changes from some definite point of view can we arrive at a due comprehension of them4 ,the constellations are more or less familiar to everybody1 so that impending changes of their forms must at once strike the eye and the imagination1 and make clearer the significance of the movements of the stars4 ,if the future history of mankind is to resemble its past and if our race is destined to survive yet a million years1 then our remote descendents will see a 8new heavens0 if not a 8new earth10 and will have to invent novel constellations to perpetuate their legends and mythologies4 ,if our knowledge of the relative distances of the stars were more complete1 it would be an interesting exercise in celestial geometry to project the constellations probably visible to the inhabitants of worlds revolving around some of the other suns of space4 ,our sun is too insignificant for us to think that he can make a conspicuous appearance among them1 except1 perhaps1 in a few cases4 ,as seen1 for instance1 from the nearest known star1 ,alpha ,centauri1 the sun would appear of the average first magnitude1 and consequently from that standpoint he might be the gem of some little constellation which had no ,sirius1 or ,arcturus1 or ,vega to eclipse him with its superior splendor4 ,but from the distance of the vast majority of the stars the sun would probably be invisible to the naked eye1 and as seen from nearer systems could only rank as a fifth or sixth magnitude star1 unnoticed and unknown except by the star-charting astronomer4 ,v ,conflagrations in the ,heavens ,suppose it were possible for the world to take fire and burn up--as some pessimists think that it will do when the ,divine wrath shall have sufficiently accumulated against it--nobody out of our own little corner of space would ever be aware of the catastrophe6 ,with all their telescopes1 the astronomers living in the golden light of ,arcturus or the diamond blaze of ,canopus would be unable to detect the least glimmer of the conflagration that had destroyed the seat of ,adam and his descendents1 just as now they are totally ignorant of its existence4 ,but at least fifteen times in the course of recorded history men looking out from the earth have beheld in the remote depths of space great outbursts of fiery light1 some of them more splendidly luminous than anything else in the firmament except the sun6 ,if they were conflagrations1 how many million worlds like ours were required to feed their blaze8 ,it is probable that 8temporary0 or 8new0 stars1 as these wonderful apparitions are called1 really are conflagrations2 not in the sense of a bonfire or a burning house or city1 but in that of a sudden eruption of inconceivable heat and light1 such as would result from the stripping off the shell of an encrusted sun or the crashing together of two mighty orbs flying through space with a hundred times the velocity of the swiftest cannon-shot4 ,temporary stars are the rarest and most erratic of astronomical phenomena4 ,the earliest records relating to them are not very clear1 and we cannot in every instance be certain that it was one of these appearances that the ignorant and superstitious old chroniclers are trying to describe4 ,the first temporary star that we are absolutely sure of appeared in #aegb1 and is known as 8,tycho's ,star10 because the celebrated ,danish astronomer 7whose remains1 with his gold-and-silver artificial nose--made necessary by a duel--still intact1 were disinterred and reburied in #aija7 was the first to perceive it in the sky1 and the most assiduous and successful in his studies of it4 ,as the first fully accredited representative of its class1 this new star made its entry upon the scene with becoming clat4 ,it is characteristic of these phenomena that they burst into view with amazing suddenness1 and1 of course1 entirely unexpectedly4 ,tycho's star appeared in the constellation ,cassiopeia1 near a now well-known and much-watched little star named ,kappa1 on the evening of ,november #aa1 #aegb4 ,the story has often been repeated1 but it never loses interest1 how ,tycho1 going home that evening1 saw people in the street pointing and staring at the sky directly over their heads1 and following the direction of their hands and eyes he was astonished to see1 near the zenith1 an unknown star of surpassing brilliance4 ,it outshone the planet ,jupiter1 and was therefore far brighter than the first magnitude4 ,there was not another star in the heavens that could be compared with it in splendor4 ,tycho was not in all respects free from the superstitions of his time--and who is8--but he had the true scientific instinct1 and immediately he began to study the stranger1 and to record with the greatest care every change in its aspect4 ,first he determined as well as he could with the imperfect instruments of his day1 many of which he himself had invented1 the precise location of the phenomena in the sky4 ,then he followed the changes that it underwent4 ,at first it brightened until its light equaled or exceeded that of the planet ,venus at her brightest1 a statement which will be appreciated at its full value by anyone who has ever watched ,venus when she plays her dazzling rle of 8,evening ,star10 flaring like an arc light in the sunset sky4 ,it even became so brilliant as to be visible in full daylight1 since1 its position being circumpolar1 it never set in the latitude of ,northern ,europe4 ,finally it began to fade1 turning red as it did so1 and in ,march1 #aegd1 it disappeared from ,tycho's searching gaze1 and has never been seen again from that day to this4 ,none of the astronomers of the time could make anything of it4 ,they had not yet as many bases of speculation as we possess today4 ,illustration3 ,chart showing location of ,tycho's star1 #aegb1 and ,nova ,persei of #aija ,tycho's star has achieved a romantic reputation by being fancifully identified with the 8,star of ,bethlehem10 said to have led the wondering ,magi from their eastern deserts to the cradle-manger of the ,savior in ,palestine4 ,many attempts have been made to connect this traditional 8star0 with some known phenomenon of the heavens1 and none seems more idle than this4 ,yet it persistently survives1 and no astronomer is free from eager questions about it addressed by people whose imagination has been excited by the legend4 ,it is only necessary to say that the supposition of a connection between the phenomenon of the ,magi and ,tycho's star is without any scientific foundation4 ,it was originally based on an unwarranted assumption that the star of ,tycho was a variable of long period1 appearing once every three hundred and fifteen years1 or thereabout4 ,if that were true there would have been an apparition somewhere near the traditional date of the birth of ,christ1 a date which is itself uncertain4 ,but even the data on which the assumption was based are inconsistent with the theory4 ,certain monkish records speak of something wonderful appearing in the sky in the years #abfd and #ide1 and these were taken to have been outbursts of ,tycho's star4 ,investigation shows that the records more probably refer to comets1 but even if the objects seen were temporary stars1 their dates do not suit the hypothesis2 from #ide to #abfd there is a gap of #cai years1 and from #abfd to #aegb one of only #cjh years2 moreover #ccg years have now 7#aiji7 elapsed since ,tycho saw the last glimmer of his star4 ,upon a variability so irregular and uncertain as that1 even if we felt sure that it existed1 no conclusion could be found concerning an apparition occurring #bjjj years ago4 ,in the year #afjj 7the year in which ,giordano ,bruno was burned at the stake for teaching that there is more than one physical world71 a temporary star of the third magnitude broke out in the constellation ,cygnus1 and curiously enough1 considering the rarity of such phenomena1 only four years later another surprisingly brilliant one appeared in the constellation ,ophiuchus4 ,this is often called 8,kepler's star10 because the great ,german astronomer devoted to it the same attention that ,tycho had given to the earlier phenomenon4 ,it1 too1 like ,tycho's1 was at first the brightest object in the stellar heavens1 although it seems never to have quite equaled its famous predecessor in splendor4 ,it disappeared after a year1 also turning of a red color as it became more faint4 ,we shall see the significance of this as we go on4 ,some of ,kepler's contemporaries suggested that the outburst of this star was due to a meeting of atoms in space1 and idea bearing a striking resemblance to the modern theory of 8astronomical collisions40 ,in #afgj1 #ahdh1 and #ahfj temporary stars made their appearance1 but none of them was of great brilliance4 ,in #ahff one of the second magnitude broke forth in the 8,northern ,crown0 and awoke much interest1 because by that time the spectroscope had begun to be employed in studying the composition of the stars1 and ,huggins demonstrated that the new star consisted largely of incandescent hydrogen4 ,but this star1 apparently unlike the others mentioned1 was not absolutely new4 ,before its outburst it had shown as a star of the ninth magnitude 7entirely invisible1 of course1 to the naked eye71 and after about six weeks it faded to its original condition in which it has ever since remained4 ,in #ahgf a temporary star appeared in the constellation ,cygnus1 and attained at one time the brightness of the second magnitude4 ,its spectrum and its behavior resembled those of its immediate predecessor4 ,in #ahhe1 astronomers were surprised to see a sixth-magnitude star glimmering in the midst of the hazy cloud of the great ,andromeda ,nebula4 ,it soon absolutely disappeared4 ,its spectrum was remarkable for being 8continuous10 like that of the nebula itself4 ,a continuous spectrum is supposed to represent a body1 or a mass1 which is either solid or liquid1 or composed of gas under great pressure4 ,in ,january1 #ahib1 a new star was suddenly seen in the constellation ,auriga4 ,it never rose much above the fourth magnitude1 but it showed a peculiar spectrum containing both bright and dark lines of hydrogen4 ,but a bewildering surprise was now in store2 the world was to behold at the opening of the twentieth century such a celestial spectacle as had not been on view since the times of ,tycho and ,kepler4 ,before daylight on the morning of ,february #bb1 #aija1 the ,rev4 ,doctor ,anderson1 of ,edinburgh1 an amateur astronomer1 who had also been the first to see the new star in ,auriga1 beheld a strange object in the constellation ,perseus not far from the celebrated variable star ,algol4 ,he recognized its character at once1 and immediately telegraphed the news1 which awoke the startled attention of astronomers all over the world4 ,when first seen the new star was no brighter than ,algol 7less than the second magnitude71 but within twenty-four hours it was ablaze1 outshining even the brilliant ,capella1 and far surpassing the first magnitude4 ,at the spot in the sky where it appeared nothing whatever was visible on the night before its coming4 ,this is known with certainty because a photograph had been made of that very region on ,february #ba1 and this photograph showed everything down to the twelfth magnitude1 but not a trace of the stranger which burst into view between the #bast and the #bbnd like the explosion of a rocket4 ,upon one who knew the stars the apparition of this intruder in a well-known constellation had the effect of a sudden invasion4 ,the new star was not far west of the zenith in the early evening1 and in that position showed to the best advantage4 ,to see ,capella1 the hitherto unchallenged ruler of that quarter of the sky1 abased by comparison with this stranger of alien aspect1 for there was always an unfamiliar look about the 8nova10 was decidedly disconcerting4 ,it seemed to portend the beginning of a revolution in the heavens4 ,one could understand what the effect of such an apparition must have been in the superstitious times of ,tycho4 ,the star of ,tycho had burst forth on the northern border of the ,milky ,way2 this one was on its southern border1 some forty-five degrees farther east4 ,astronomers were well-prepared this time for the scientific study of the new star1 both astronomical photography and spectroscopy having been perfected1 and the results of their investigations were calculated to increase the wonder with which the phenomenon was regarded4 ,the star remained at its brightest only a few days2 then1 like a veritable conflagration1 it began to languish2 and1 like the reflection of a dying fire1 as it sank it began to glow with the red color of embers4 ,but its changes were spasmodic2 once about every three days it flared up only to die away again4 ,during these fluctuations its light varied alternately in the ratio of one to six4 ,finally it took a permanent downward course1 and after a few months the naked eye could no longer perceive it2 but it remained visible with telescopes1 gradually fading until it had sunk to the ninth magnitude4 ,then another astonishing change happened3 in ,august photographs taken at the ,yerkes ,observatory and at ,heidelberg showed that the 8nova0 was surrounded by a spiral nebula6 ,the nebula had not been there before1 and no one could doubt that it represented a phase of the same catastrophe that had produced the outburst of the new star4 ,at one time the star seemed virtually to have disappeared1 as if all its substance had been expanded into the nebulous cloud1 but always there remained a stellar nucleus about which the misty spiral spread wider and ever wider1 like a wave expanding around a center of disturbance4 ,the nebula too showed a variability of brightness1 and four condensations which formed in it seemed to have a motion of revolution about the star4 ,as time went on the nebula continued to expand at a rate which was computed to be not less than twenty thousand miles per second6 ,and now the star itself1 showing indications of having turned into a nebula1 behaved in a most erratic manner1 giving rise to the suspicion that it was about to burst out again4 ,but this did not occur1 and at length it sunk into a state of lethargy from which it has to the present time not recovered4 ,but the nebulous spiral has disappeared1 and the entire phenomena as it now 7#aiji7 exists consists of a faint nebulous star of less than the ninth magnitude4 ,the wonderful transformations just described had been forecast in advance of the discovery of the nebulous spiral encircling the star by the spectroscopic study of the latter4 ,at first there was no suggestion of a nebular constitution1 but within a month or two characteristic nebular lines began to appear1 and in less than six months the whole spectrum had been transformed to the nebular type4 ,in the mean time the shifting of the spectral lines indicated a complication of rapid motions in several directions simultaneously4 ,these motions were estimated to amount to from one hundred to five hundred miles per second4 ,the human mind is so constituted that it feels forced to seek an explanation of so marvelous a phenomenon as this1 even in the absence of the data needed for a sound conclusion4 ,the most natural hypothesis1 perhaps1 is that of a collision4 ,such a catastrophe could certainly happen4 ,it has been shown1 for instance1 that in infinity of time the earth is sure to be hit by a comet2 in the same way it may be asserted that1 if no time limit is fixed1 the sun is certain to run against some obstacle in space1 either another star1 or a dense meteor swarm1 or one of the dark bodies which there is every reason to believe abound around us4 ,the consequences of such a collision are easy to foretell1 provided that we know the masses and the velocities of the colliding bodies4 ,in a preceding chapter we have discussed the motions of the sun and stars1 and have seen that they are so swift that an encounter between any two of them could not but be disastrous4 ,but this is not all2 for as soon as two stars approached within a few million miles their speed would be enormously increased by their reciprocal attractions and1 if their motion was directed radially with respect to their centers1 they would come together with a crash that would reduce them both to nebulous clouds4 ,it is true that the chances of such a 8head-on0 collision are relatively very small2 two stars approaching each other would most probably fall into closed orbits around their common center of gravity4 ,if there were a collision it would most likely be a grazing one instead of a direct front-to-front encounter4 ,but even a close approach1 without any actual collision1 would probably prove disastrous1 owing to the tidal influence of each of the bodies on the other4 ,suns1 in consequence of their enormous masses and dimensions and the peculiarities of their constitution1 are exceedingly dangerous to one another at close quarters4 ,propinquity awakes in them a mutually destructive tendency4 ,consisting of matter in the gaseous1 or perhaps1 in some cases1 liquid1 state1 their tidal pull upon each other if brought close together might burst them asunder1 and the photospheric envelope being destroyed the internal incandescent mass would gush out1 bringing fiery death to any planets that were revolving near4 ,without regard to the resulting disturbance of the earth's orbit1 the close approach of a great star to the sun would be in the highest degree perilous to us4 ,but this is a danger which may properly be regarded as indefinitely remote1 since1 at our present location in space1 we are certainly far from every star except the sun1 and we may feel confident that no great invisible body is near1 for if there were one we should be aware of its presence from the effects of its attraction4 ,as to dark nebul which may possibly lie in the track that the solar system is pursuing at the rate of #cge1jjj1jjj miles per year1 that is another question--and they1 too1 could be dangerous6 ,illustration3 ,nova ,persei1 with its nebular rings ,this brings us directly back to 8,nova ,persei10 for among the many suggestions offered to explain its outburst1 as well as those of other temporary stars1 one of the most fruitful is that of a collision between a star and a vast invisible nebula4 ,professor ,seeliger1 of ,munich1 first proposed this theory1 but it afterward underwent some modifications from others4 ,stated in a general form1 the idea is that a huge dark body1 perhaps an extinguished sun1 encountered in its progress through space a widespread flock of small meteors forming a dark nebula4 ,as it plunged into the swarm the friction of the innumerable collisions with the meteors heated its surface to incandescence1 and being of vast size it then became visible to us as a new star4 ,meanwhile the motion of the body through the nebula1 and its rotation upon itself1 set up a gyration in the blazing atmosphere formed around it by the vaporized meteors2 and as this atmosphere spread wider1 under the laws of gyratory motion a rotation in the opposite direction began in the inflamed meteoric cloud outside the central part of the vortex4 ,thus the spectral lines were caused to show motion in opposite directions1 a part of the incandescent mass approaching the earth simultaneously with the retreat of another part4 ,so the curious spectroscopic observations before mentioned were explained4 ,this theory might also account for the appearance of the nebulous spiral first seen some six months after the original outburst4 ,the sequent changes in the spectrum of the 8nova0 are accounted for by this theory on the assumption1 reasonable enough in itself1 that at first the invading body would be enveloped in a vaporized atmosphere of relatively slight depth1 producing by its absorption the fine dark lines first observed2 but that as time went on and the incessant collisions continued1 the blazing atmosphere would become very deep and extensive1 whereupon the appearance of the spectral lines would change1 and bright lines due to the light of the incandescent meteors surrounding the nucleus at a great distance would take the place of the original dark ones4 ,the vortex of meteors once formed would protect the flying body within from further immediate collisions1 the latter now occurring mainly among the meteors themselves1 and then the central blaze would die down1 and the original splendor of the phenomenon would fade4 ,but the theories about ,nova ,persei have been almost as numerous as the astronomers who have speculated about it4 ,one of the most startling of them assumed that the outburst was caused by the running amuck of a dark star which had encountered another star surrounded with planets1 the renewed outbreaks of light after the principal one had faded being due to the successive running down of the unfortunate planets6 ,yet another hypothesis is based on what we have already said of the tidal influence that two close approaching suns would have upon each other4 ,supposing two such bodies which had become encrusted1 but remained incandescent and fluid within1 to approach within almost striking distance2 they would whirl each other about their common center of gravity1 and at the same time their shells would burst under the tidal strain1 and their glowing nuclei being disclosed would produce a great outburst of light4 ,applying this theory to a 8nova10 like that of #ahff in the 8,northern ,crown10 which had been visible as a small star before the outbreak1 and which afterward resumed its former aspect1 we should have to assume that a yet shining sun had been approached by a dark body whose attraction temporarily burst open its photosphere4 ,it might be supposed that in this case the dark body was too far advanced in cooling to suffer the same fate from the tidal pull of its victim4 ,but a close approach of that kind would be expected to result in the formation of a binary system1 with orbits of great eccentricity1 perhaps1 and after the lapse of a certain time the outburst should be renewed by another approximation of the two bodies4 ,a temporary star of that kind would rather be ranked as a variable4 ,the celebrated ,french astronomer1 ,janssen1 had a different theory of ,nova ,persei1 and of temporary stars in general4 ,according to his idea1 such phenomena might be the result of chemical changes taking place in a sun without interference by1 or collision with1 another body4 ,janssen was engaged for many years in trying to discover evidence of the existence of oxygen in the sun1 and he constructed his observatory on the summit of ,mount ,blanc specially to pursue that research4 ,he believed that oxygen must surely exist in the sun since we find so many other familiar elements included in the constitution of the solar globe1 and as he was unable to discover satisfactory evidence of its presence he assumed that it existed in a form unknown on the earth4 ,if it were normally in the sun's chromosphere1 or coronal atmosphere1 he said1 it would combine with the hydrogen which we know is there and form an obscuring envelope of water vapor4 ,it exists1 then1 in a special state1 uncombined with hydrogen2 but let the temperature of the sun sink to a critical point and the oxygen will assume its normal properties and combine with the hydrogen1 producing a mighty outburst of light and heat4 ,this1 ,janssen thought1 might explain the phenomena of the temporary stars4 ,it would also1 he suggested1 account for their brief career1 because the combination of the elements would be quickly accomplished1 and then the resulting water vapor would form an atmosphere cutting off the radiation from the star within4 ,this theory may be said to have a livelier human interest than some of the others1 since1 according to it1 the sun may carry in its very constitution a menace to mankind2 one does not like to think of it being suddenly transformed into a gigantic laboratory for the explosive combination of oxygen and hydrogen6 ,but while ,janssen's theory might do for some temporary stars1 it is inadequate to explain all the phenomena of ,nova ,persei1 and particularly the appearance of the great spiral nebula that seemed to exhale from the heart of the star4 ,upon the whole1 the theory of an encounter between a star and a dark nebula seems best to fit the observations4 ,by that hypothesis the expanding billow of light surrounding the core of the conflagration is very well accounted for1 and the spectroscopic peculiarities are also explained4 ,dr ,gustov ,le ,bon offers a yet more alarming theory1 suggesting that temporary stars are the result of atomic explosion2 but we shall touch upon this more fully in ,chapter #ad4 ,twice in the course of this discussion we have called attention to the change of color invariably undergone by temporary stars in the later stages of their career4 ,this was conspicuous with ,nova ,persei which glowed more and more redly as it faded1 until the nebulous light began to overpower that of the stellar nucleus4 ,nothing could be more suggestive of the dying out of a great fire4 ,moreover1 change of color from white to red is characteristic of all variable stars of long period1 such as 8,mira0 in ,cetus4 ,it is also characteristic of stars believed to be in the later stages of evolution1 and consequently approaching extinction1 like ,antares and ,betelgeuse1 and still more notably certain small stars which 8gleam like rubies in the field of the telescope40 ,these last appear to be suns in the closing period of existence as self-luminous bodies4 ,between the white stars1 such as ,sirius and ,rigel1 and the red stars1 such as ,aldebaran and ,alpha ,herculis1 there is a progressive series of colors from golden yellow through orange to deep red4 ,the change is believed to be due to the increase of absorbing vapors in the stellar atmosphere as the body cools down4 ,in the case of ordinary stars these changes no doubt occupy many millions of years1 which represent the average duration of solar life2 but the temporary stars run through similar changes in a few months3 they resemble ephemeral insects--born in the morning and doomed to perish with the going down of the sun4 ,,vi ,explosive and ,whirling ,nebul ,one of the most surprising triumphs of celestial photography was ,professor ,keeler's discovery1 in #ahii1 that the great majority of the nebul have a distinctly spiral form4 ,this form1 previously known in ,lord ,rosse's great 8,whirlpool ,nebula10 had been supposed to be exceptional2 now the photographs1 far excelling telescopic views in the revelation of nebular forms1 showed the spiral to be the typical shape4 ,indeed1 it is a question whether all nebul are not to some extent spiral4 ,the extreme importance of this discovery is shown in the effect that it has had upon hitherto prevailing views of solar and planetary evolution4 ,for more than three-quarters of a century ,laplace's celebrated hypothesis of the manner of origin of the solar system from a rotating and contracting nebula surrounding the sun had guided speculation on that subject1 and had been tentatively extended to cover the evolution of systems in general4 ,the apparent forms of some of the nebul which the telescope had revealed were regarded1 and by some are still regarded1 as giving visual evidence in favor of this theory4 ,there is a 8ring nebula0 in ,lyra with a central star1 and a 8planetary nebula0 in ,gemini bearing no little resemblance to the planet ,saturn with its rings1 both of which appear to be practical realizations of ,laplace's idea1 and the elliptical rings surrounding the central condensation of the ,andromeda ,nebula may be cited for the same kind of proof4 ,illustration3 ,lord ,rosse's nebula ,but since ,keeler's discovery there has been a decided turning away of speculation another way4 ,the form of the spiral nebul seems to be entirely inconsistent with the theory of an originally globular or disk-shaped nebula condensing around a sun and throwing or leaving off rings1 to be subsequently shaped into planets4 ,some astronomers1 indeed1 now reject ,laplace's hypothesis in toto1 preferring to think that even our solar system originated from a spiral nebula4 ,since the spiral type prevails among the existing nebul1 we must make any mechanical theory of the development of stars and planetary systems from them accord with the requirements which that form imposes4 ,a glance at the extraordinary variations upon the spiral which ,professor ,keeler's photographs reveal is sufficient to convince one of the difficulty of the task of basing a general theory upon them4 ,in truth1 it is much easier to criticize ,laplace's hypothesis than to invent a satisfactory substitute for it4 ,if the spiral nebul seem to oppose it there are other nebul which appear to support it1 and it may be that no one fixed theory can account for all the forms of stellar evolution in the universe4 ,our particular planetary system may have originated very much as the great ,french mathematician supposed1 while others have undergone1 or are now undergoing1 a different process of development4 ,there is always a too strong tendency to regard an important new discovery and the theories and speculations based upon it as revolutionizing knowledge1 and displacing or overthrowing everything that went before4 ,upon the plea that 8,laplace only made a guess0 more recent guesses have been driven to extremes and treated by injudicious exponents as 8the solid facts at last40 ,illustration3 ,wonderful spiral in triangulum ,before considering more recent theories than ,laplace's1 let us see what the nature of the photographic revelations is4 ,the vast celestial maelstrom discovered by ,lord ,rosse in the 8,hunting ,dogs0 may be taken as the leading type of the spiral nebul1 although there are less conspicuous objects of the kind which1 perhaps1 better illustrate some of their peculiarities4 ,lord ,rosse's nebula appears far more wonderful in the photographs than in his drawings made with the aid of his giant reflecting telescope at ,parsonstown1 for the photographic plate records details that no telescope is capable of showing4 ,suppose we look at the photograph of this object as any person of common sense would look at any great and strange natural phenomenon4 ,what is the first thing that strikes the mind8 ,it is certainly the appearance of violent whirling motion4 ,one would say that the whole glowing mass had been spun about with tremendous velocity1 or that it had been set rotating so rapidly that it had become the victim of 8centrifugal force10 one huge fragment having broken loose and started to gyrate off into space4 ,closer inspection shows that in addition to the principal focus there are various smaller condensations scattered through the mass4 ,these are conspicuous in the spirals4 ,some of them are stellar points1 and but for the significance of their location we might suppose them to be stars which happen to lie in a line between us and the nebula4 ,but when we observe how many of them follow most faithfully the curves of the spirals we cannot but conclude that they form an essential part of the phenomenon2 it is not possible to believe that their presence in such situations is merely fortuitous4 ,one of the outer spirals has at least a dozen of these star-like points strung upon it2 some of them sharp1 small1 and distinct1 others more blurred and nebulous1 suggesting different stages of condensation4 ,even the part which seems to have been flung loose from the main mass has1 in addition to its central condensation1 at least one stellar point gleaming in the half-vanished spire attached to it4 ,some of the more distant stars scattered around the 8whirlpool0 look as if they too had been shot out of the mighty vortex1 afterward condensing into unmistakable solar bodies4 ,there are at least two curved rows of minute stars a little beyond the periphery of the luminous whirl which clearly follow lines concentric with those of the nebulous spirals4 ,such facts are simply dumbfounding for anyone who will bestow sufficient thought upon them1 for these are suns1 though they may be small ones2 and what a birth is that for a sun6 ,look now again at the glowing spirals4 ,we observe that hardly have they left the central mass before they begin to coagulate4 ,in some places they have a 8ropy0 aspect2 or they are like peascods filled with growing seeds1 which eventually will become stars4 ,the great focus itself shows a similar tendency1 especially around its circumference4 ,the sense that it imparts of a tremendous shattering force at work is overwhelming4 ,there is probably more matter in that whirling and bursting nebula than would suffice to make a hundred solar systems6 ,it must be confessed at once that there is no confirmation of the ,laplacean hypothesis here2 but what hypothesis will fit the facts8 ,there is one which it has been claimed does so1 but we shall come to that later4 ,in the meanwhile1 as a preparation1 fix in the memory the appearance of that second spiral mass spinning beside its master which seems to have spurned it away4 ,illustration3 ,spiral in ,ursa ,major ,for a second example of the spiral nebul look at the one in the constellation ,triangulum4 ,god1 how hath the imagination of puny man failed to comprehend ,thee6 ,here is creation through destruction with a vengeance6 ,the spiral form of the nebula is unmistakable1 but it is half obliterated amid the turmoil of flying masses hurled away on all sides with tornadic fury4 ,the focus itself is splitting asunder under the intolerable strain1 and in a little while1 as time is reckoned in the ,cosmos1 it will be gyrating into stars4 ,and then look at the cyclonic rain of already finished stars whirling round the outskirts of the storm4 ,observe how scores of them are yet involved in the fading streams of the nebulous spirals2 see how they have been thrown into vast loops and curves1 of a beauty that half redeems the terror of the spectacle enclosed within their lines--like iridescent cirri hovering about the edges of a hurricane4 ,and so again are suns born6 ,let us turn to the exquisite spiral in ,ursa ,major2 how different its aspect from that of the other6 ,one would say that if the terrific coil in ,triangulum has all but destroyed itself in its fury1 this one on the contrary has just begun its self-demolition4 ,as one gazes one seems to see in it the smooth1 swift1 accelerating motion that precedes catastrophe4 ,the central part is still intact1 dense1 and uniform in texture4 ,how graceful are the spirals that smoothly rise from its oval rim and1 gemmed with little stars1 wind off into the darkness until they have become as delicate as threads of gossamer6 ,but at bottom the story told here is the same--creation by gyration6 ,compare with the above the curious mass in ,cetus4 ,here the plane of the whirling nebula nearly coincides with our line of sight and we see the object at a low angle4 ,it is far advanced and torn to shreds1 and if we could look at it perpendicularly to its plane it is evident that it would closely resemble the spectacle in ,triangulum4 ,then take the famous ,andromeda ,nebula 7see ,frontispiece71 which is so vast that notwithstanding its immense distance even the naked eye perceives it as an enigmatical wisp in the sky4 ,its image on the sensitive plate is the masterpiece of astronomical photography2 for wild1 incomprehensible beauty there is nothing that can be compared with it4 ,here1 if anywhere1 we look upon the spectacle of creation in one of its earliest stages4 ,the ,andromeda ,nebula is apparently less advanced toward transformation into stellar bodies than is that in ,triangulum4 ,the immense crowd of stars sprinkled over it and its neighborhood seem in the main to lie this side of the nebula1 and consequently to have no connection with it4 ,but incipient stars 7in some places clusters of them7 are seen in the nebulous rings1 while one or two huge masses seem to give promise of transformation into stellar bodies of unusual magnitude4 ,i say 8rings0 because although the loops encompassing the ,andromeda ,nebula have been called spirals by those who wish utterly to demolish ,laplace's hypothesis1 yet they are not manifestly such1 as can be seen on comparing them with the undoubted spirals of the ,lord ,rosse ,nebula4 ,they look quite as much like circles or ellipses seen at an angle of1 say1 fifteen or twenty degrees to their plane4 ,if they are truly elliptical they accord fairly well with ,laplace's idea1 except that the scale of magnitude is stupendous1 and if the ,andromeda ,nebula is to become a solar system it will surpass ours in grandeur beyond all possibility of comparison4 ,illustration3 ,nebula in ,cetus ,there is one circumstance connected with the spiral nebul1 and conspicuous in the ,andromeda ,nebula on account of its brightness1 which makes the question of their origin still more puzzling2 they all show continuous spectra1 which1 as we have before remarked1 indicate that the mass from which the light comes is either solid or liquid1 or a gas under heavy pressure4 ,thus nebul fall into two classes3 the 8white0 nebul1 giving a continuous spectrum2 and the 8green0 nebul whose spectra are distinctly gaseous4 ,the ,andromeda ,nebula is the great representative of the former class and the ,orion ,nebula of the latter4 ,the spectrum of the ,andromeda ,nebula has been interpreted to mean that it consists not of luminous gas1 but of a flock of stars so distant that they are separately indistinguishable even with powerful telescopes1 just as the component stars of the ,milky ,way are indistinguishable with the naked eye2 and upon this has been based the suggestion that what we see in ,andromeda is an outer universe whose stars form a series of elliptical garlands surrounding a central mass of amazing richness4 ,but this idea is unacceptable if for no other reason than that1 as just said1 all the spiral nebul possess the same kind of spectrum1 and probably no one would be disposed to regard them all as outer universes4 ,as we shall see later1 the peculiarity of the spectra of the spiral nebul is appealed to in support of a modern substitute for ,laplace's hypothesis4 ,finally1 without having by any means exhausted the variety exhibited by the spiral nebul1 let us turn to the great representative of the other species1 the ,orion ,nebula4 ,in some ways this is even more marvelous than the others4 ,the early drawings with the telescope failed to convey an adequate conception either of its sublimity or of its complication of structure4 ,it exists in a nebulous region of space1 since photographs show that nearly the whole constellation is interwoven with faintly luminous coils4 ,to behold the entry of the great nebula into the field even of a small telescope is a startling experience which never loses its novelty4 ,as shown by the photographs1 it is an inscrutable chaos of perfectly amazing extent1 where spiral bands1 radiating streaks1 dense masses1 and dark yawning gaps are strangely intermingled without apparent order4 ,in one place four conspicuous little stars1 better seen in a telescope than in the photograph on account of the blurring produced by over-exposure1 are suggestively situated in the midst of a dark opening1 and no observer has ever felt any doubt that these stars have been formed from the substance of the surrounding nebula4 ,there are many other stars scattered over its expanse which manifestly owe their origin to the same source4 ,but compare the general appearance of this nebula with the others that we have studied1 and remark the difference4 ,if the unmistakably spiral nebul resemble bursting fly-wheels or grindstones from whose perimeters torrents of sparks are flying1 the ,orion ,nebula rather recalls the aspect of a cloud of smoke and fragments produced by the explosion of a shell4 ,this idea is enforced by the look of the outer portion farthest from the bright half of the nebula1 where sharply edged clouds with dark spaces behind seem to be billowing away as if driven by a wind blowing from the center4 ,illustration3 ,the ,orion nebula ,next let us consider what scientific speculation has done in the effort to explain these mysteries4 ,laplace's hypothesis can certainly find no standing ground either in the ,orion ,nebula or in those of a spiral configuration1 whatever may be its situation with respect to the grand ,nebula of ,andromeda1 or the 8ring0 and 8planetary0 nebul4 ,some other hypothesis more consonant with the appearances must be found4 ,among the many that have been proposed the most elaborate is the 8,planetesimal ,hypothesis0 of ,professors ,chamberlin and ,moulton4 ,it is to be remarked that it applies to the spiral nebul distinctively1 and not to an apparently chaotic mass of gas like the vast luminous cloud in ,orion4 ,the gist of the theory is that these curious objects are probably the result of close approaches to each other of two independent suns1 reminding us of what was said on this subject when we were dealing with temporary stars4 ,of the previous history of these appulsing suns the theory gives us no account2 they are simply supposed to arrive within what may be called an effective tide-producing distance1 and then the drama begins4 ,some of the probable consequences of such an approach have been noticed in ,chapter #e2 let us now consider them a little more in detail4 ,tides always go in couples2 if there is a tide on one side of a globe there will be a corresponding tide on the other side4 ,the cause is to be found in the law that the force of gravitation varies inversely as the square of the distance2 the attraction on the nearest surface of the body exercised by another body is greater than on its center1 and greater yet than on its opposite surface4 ,if two great globes attract each other1 each tends to draw the other out into an ellipsoidal figure2 they must be more rigid than steel to resist this--and even then they cannot altogether resist4 ,if they are liquid or gaseous they will yield readily to the force of distortion1 the amount of which will depend upon their distance apart1 for the nearer they are the greater becomes the tidal strain4 ,if they are encrusted without and liquid or gaseous in the interior1 the internal mass will strive to assume the figure demanded by the tidal force1 and will1 if it can1 burst the restraining envelope4 ,now this is virtually the predicament of the body we call a sun when in the immediate presence of another body of similarly great mass4 ,such a body is presumably gaseous throughout1 the component gases being held in a state of rigidity by the compression produced by the tremendous gravitational force of their own aggregate mass4 ,at the surface such a body is enveloped in a shell of relatively cool matter4 ,now suppose a great attracting body1 such as another sun1 to approach near enough for the difference in its attraction on the two opposite sides of the body and on its center to become very great2 the consequence will be a tidal deformation of the whole body1 and it will lengthen out along the line of the gravitational pull and draw in at the sides1 and if its shell offers considerable resistance1 but not enough to exercise a complete restraint1 it will be violently burst apart1 or blown to atoms1 and the internal mass will leap out on the two opposite sides in great fiery spouts4 ,in the case of a sun further advanced in cooling than ours the interior might be composed of molten matter while the exterior crust had become rigid like the shell of an egg2 then the force of the 8tidal explosion0 produced by the appulse of another sun would be more violent in consequence of the greater resistance overcome4 ,such1 then1 is the mechanism of the first phase in the history of a spiral nebula according to the ,planetesimal ,hypothesis4 ,two suns1 perhaps extinguished ones1 have drawn near together1 and an explosive outburst has occured in one or both4 ,the second phase calls for a more agile exercise of the imagination4 ,to simplify the case1 let us suppose that only one of the tugging suns is seriously affected by the strain4 ,its vast wings produced by the outburst are twisted into spirals by their rotation and the contending attractions exercised upon them1 as the two suns1 like battleships in desperate conflict1 curve round each other1 concentrating their destructive energies4 ,then immense quantities of dbris are scattered about in which eddies are created1 and finally1 as the sun that caused the damage goes on its way1 leaving its victim to repair its injuries as it may1 the dispersed matter cools1 condenses1 and turns into streams of solid particles circling in elliptical paths about their parent sun4 ,these particles1 or fragments1 are the 8planetesimals0 of the theory4 ,in consequence of the inevitable intersection of the orbits of the planetesimals1 nodes are formed where the flying particles meet1 and at these nodes large masses are gradually accumulated4 ,the larger the mass the greater its attraction1 and at last the nodal points become the nuclei of great aggregations from which planets are shaped4 ,this1 in very brief form1 is the ,planetesimal ,hypothesis which we are asked to substitute for that based on ,laplace's suggestion as an explanation of the mode of origin of the solar system2 and the phenomena of the spiral nebul are appealed to as offering evident support to the new hypothesis4 ,we are reminded that they are elliptical in outline1 which accords with the hypothesis2 that their spectra are not gaseous1 which shows that they may be composed of solid particles like the planetesimals2 and that their central masses present an oval form1 which is what would result from the tidal effects1 as just described4 ,we also remember that some of them1 like the ,lord ,rosse and the ,andromeda nebul1 are visually double1 and in these cases we might suppose that the two masses represent the tide-burst suns that ventured into too close proximity4 ,it may be added that the authors of the theory do not insist upon the appulse of two suns as the only way in which the planetesimals may have originated1 but it is the only supposition that has been worked out4 ,but serious questions remain4 ,it needs1 for instance1 but a glance at the ,triangulum monster to convince the observer that it cannot be a solar system which is being evolved there1 but rather a swarm of stars4 ,many of the detached masses are too vast to admit of the supposition that they are to be transformed into planets1 in our sense of planets1 and the distances of the stars which appear to have been originally ejected from the focal masses are too great to allow us to liken the assemblage that they form to a solar system4 ,then1 too1 no nodes such as the hypothesis calls for are visible4 ,moreover1 in most of the spiral nebul the appearances favor the view that the supposititious encountering suns have not separated and gone each rejoicing on its way1 after having inflicted the maximum possible damage on its opponent1 but that1 on the contrary1 they remain in close association like two wrestlers who cannot escape from each other's grasp4 ,and this is exactly what the law of gravitation demands2 stars cannot approach one another with impunity1 with regard either to their physical make-up or their future independence of movement4 ,the theory undertakes to avoid this difficulty by assuming that in the case of our system the approach of the foreign body to the sun was not a close one--just close enough to produce the tidal extrusion of the relatively insignificant quantity of matter needed to form the planets4 ,but even then the effect of the appulse would be to change the direction of flight1 both of the sun and of its visitor1 and there is no known star in the sky which can be selected as the sun's probable partner in their ancient pas deux4 ,that there are unconquered difficulties in ,laplace's hypothesis no one would deny1 but in simplicity of conception it is incomparably more satisfactory1 and with proper modifications could probably be made more consonant with existing facts in our solar system than that which is offered to replace it4 ,even as an explanation of the spiral nebul1 not as solar systems in process of formation1 but as the birthplaces of stellar clusters1 the ,planetesimal ,hypothesis would be open to many objections4 ,granting its assumptions1 it has undoubtedly a strong mathematical framework1 but the trouble is not with the mathematics but with the assumptions4 ,laplace was one of the ablest mathematicians that ever lived1 but he had never seen a spiral nebula2 if he had1 he might have invented a hypothesis to suit its phenomena4 ,his actual hypothesis was intended only for our solar system1 and he left it in the form of a 8note0 for the consideration of his successors1 with the hope that they might be able to discover the full truth1 which he confessed was hidden from him4 ,it cannot be said that that truth has yet been found1 and when it is found the chances are that intuition and not logic will have led to it4 ,the spiral nebul1 then1 remain among the greatest riddles of the universe1 while the gaseous nebul1 like that of ,orion1 are no less mysterious1 although it seems impossible to doubt that both forms give birth to stars4 ,it is but natural to look to them for light on the question of the origin of our planetary system2 but we should not forget that the scale of the phenomena in the two cases is vastly different1 and the forces in operation may be equally different4 ,a hill may have been built up by a glacier1 while a mountain may be the product of volcanic forces or of the upheaval of the strata of the planet4 ,,vii ,the ,banners of the ,sun ,as all the world knows1 the sun1 a blinding globe pouring forth an inconceivable quantity of light and heat1 whose daily passage through the sky is caused by the earth's rotation on its axis1 constitutes the most important phenomenon of terrestial existence4 ,viewed with a dark glass to take off the glare1 or with a telescope1 its rim is seen to be a sharp and smooth circle1 and nothing but dark sky is visible around it4 ,except for the interference of the moon1 we should probably never have known that there is any more of the sun than our eyes ordinarily see4 ,but when an eclipse of the sun occurs1 caused by the interposition of the opaque globe of the moon1 we see its immediate surroundings1 which in some respects are more wonderful than the glowing central orb4 ,these surroundings1 although not in the sense in which we apply the term to the gaseous envelope of the earth1 may be called the sun's atmosphere4 ,they consist of two very different parts--first1 the red 8prominences10 which resemble tongues of flame ascending thousands of miles above the sun's surface2 and1 second1 the 8corona10 which extends to distances of millions of miles from the sun1 and shines with a soft1 glowing light4 ,the two combined1 when well seen1 make a spectacle without parallel among the marvels of the sky4 ,although many attempts have been made to render the corona visible when there is no eclipse1 all have failed1 and it is to the moon alone that we owe its revelation4 ,to cover the sun's disk with a circular screen will not answer the purpose because of the illumination of the air all about the observer4 ,when the moon hides the sun1 on the other hand1 the sunlight is withdrawn from a great cylinder of air extending to the top of the atmosphere and spreading many miles around the observer4 ,there is then no glare to interfere with the spectacle1 and the corona appears in all its surprising beauty4 ,the prominences1 however1 although they were discovered during an eclipse1 can now1 with the aid of the spectroscope1 be seen at any time4 ,but the prominences are rarely large enough to be noticed by the naked eye1 while the streamers of the corona1 stretching far away in space1 like ghostly banners blown out from the black circle of the obscuring moon1 attract every eye1 and to this weird apparition much of the fear inspired by eclipses has been due4 ,but if the corona has been a cause of terror in the past it has become a source of growing knowledge in our time4 ,illustration3 ,the ,corona ,the story of the first scientific observation of the corona and the prominences is thrillingly interesting1 and in fact dramatic4 ,the observation was made during the eclipse of #ahdb1 which fortunately was visible all over ,central and ,southern ,europe so that scores of astronomers saw it4 ,the interest centers in what happened at ,pavia in ,northern ,italy1 where the ,english astronomer ,francis ,baily had set up his telescope4 ,the eclipse had begun and ,bailey was busy at his telescope when1 to quote his own words in the account which he wrote for the ,memoirs of the ,royal ,astronomical ,society3 ,i was astounded by a tremendous burst of applause from the streets below1 and at the same moment was electrified by the sight of one of the most brilliant and splendid phenomena that can well be imagined2 for at that instant the dark body of the moon was suddenly surrounded with a corona1 or kind of bright glory1 similar in shape and magnitude to that which painters draw round the heads of saints444 ,pavia contains many thousand inhabitants1 the major part of whom were at this early hour walking about the streets and squares or looking out of windows in order to witness this long-talked-of phenomenon2 and when the total obscuration took place1 which was instantaneous1 there was a universal shout from every observer which 8made the welkin ring10 and for the moment withdrew my attention from the object with which ,i was immediately occupied4 ,i had1 indeed1 expected the appearance of a luminous circle round the moon during the time of total obscurity2 but ,i did not expect1 from any of the accounts of preceding eclipses that ,i had read1 to witness so magnificent an exhibition as that which took place444 ,splendid and astonishing1 however1 as this remarkable phenomenon really was1 and although it could not fail to call forth the admiration and applause of every beholder1 yet ,i must confess that there was at the same time something in its singular and wonderful appearance that was appalling444 ,but the most remarkable circumstance attending the phenomenon was the appearance of three large protuberances apparently emanating from the circumference of the moon1 but evidently forming a portion of the corona4 ,they had the appearance of mountains of a prodigious elevation2 their color was red tinged with lilac or purple2 perhaps the color of the peach-blossom would more nearly represent it4 ,they somewhat resembled the tops of the snowy ,alpine mountains when colored by the rising or the setting sun4 ,they resembled the ,alpine mountains in another respect1 inasmuch as their light was perfectly steady1 and had none of that flickering or sparkling motion so visible in other parts of the corona444 ,the whole of these protuberances were visible even to the last moment of total obscuration1 and when the first ray of light was admitted from the sun they vanished1 with the corona1 altogether1 and daylight was instantly restored4 ,i have quoted nearly all of this remarkable description not alone for its intrinsic interest1 but because it is the best depiction that can be found of the general phenomena of a total solar eclipse4 ,still1 not every such eclipse offers an equally magnificent spectacle4 ,the eclipses of #aijj and #aije1 for instance1 which were seen by the writer1 the first in ,south ,carolina and the second in ,spain1 fell far short of that described by ,bailey in splendor and impressiveness4 ,of course1 something must be allowed for the effect of surprise2 ,bailey had not expected to see what was so suddenly disclosed to him4 ,but both in #aijj and #aije the amount of scattered light in the sky was sufficient in itself to make the corona appear faint1 and there were no very conspicuous prominences visible4 ,yet on both occasions there was manifest among the spectators that mingling of admiration and awe of which ,bailey speaks4 ,the ,south ,carolinians gave a cheer and the ladies waved their handkerchiefs when the corona1 ineffably delicate of form and texture1 melted into sight and then in two minutes melted away again4 ,the ,spaniards1 crowded on the citadel hill of ,burgos1 with their king and his royal retinue in their midst1 broke out with a great clapping of hands as the awaited spectacle unfolded itself in the sky2 and on both occasions1 before the applause began1 after an awed silence a low murmur ran through the crowds4 ,at ,burgos it is said many made the sign of the cross4 ,it was not long before ,bailey's idea that the prominences were a part of the corona was abandoned1 and it was perceived that the two phenomena were to a great extent independent4 ,at the eclipse of #ahfh1 which the astronomers1 aroused by the wonderful scene of #ahdb1 and eager to test the powers of the newly invented spectroscope1 flocked to ,india to witness1 ,janssen conceived the idea of employing the spectroscope to render the prominences visible when there was no eclipse4 ,he succeeded the very next day1 and these phenomena have been studied in that way ever since4 ,there are recognized two kinds of prominences--the 8erruptive0 and the 8quiescent40 ,the latter1 which are cloud-like in form1 may be seen almost anywhere along the edge of the sun2 but the former1 which often shoot up as if hurled from mighty volcanoes1 appear to be associated with sun-spots1 and appear only above the zones where spots abound4 ,either of them1 when seen in projection against the brilliant solar disk1 appears white1 not red1 as against a background of sky4 ,the quiescent prominences1 whose elevation is often from forty thousand to sixty thousand miles1 consist1 as the spectroscope shows1 mainly of hydrogen and helium4 ,the latter1 it will be remembered1 is an element which was known to be in the sun many years before the discovery that it also exists in small quantities on the earth4 ,a fact which may have a significance which we cannot at present see is that the emanation from radium gradually and spontaneously changes into helium1 an alchemistical feat of nature that has opened many curious vistas to speculative thinkers4 ,the eruptive prominences1 which do not spread horizontally like the others1 but ascend with marvelous velocity to elevations of half a million miles or more1 are apparently composed largely of metallic vapors--i4e4 metals which are usually solid on the earth1 but which at solar temperatures are kept in a volatilized state4 ,the velocity of their ascent occasionally amounts to three hundred or four hundred miles per second4 ,it is known from mathematical considerations that the gravitation of the sun would not be able to bring back any body that started from its surface with a velocity exceeding three hundred and eighty-three miles per second2 so it is evident that some of the matter hurled forth in eruptive prominences may escape from solar control and go speeding out into space1 cooling and condensing into solid masses4 ,there seems to be no reason why some of the projectiles from the sun might not reach the planets4 ,here1 then1 we have on a relatively small scale1 explosions recalling those which it has been imagined may be the originating cause of some of the sudden phenomena of the stellar heavens4 ,illustration3 ,a solar 8prominence40 ,photographed ,may #ba1 #aijg ,of the sun-spots it is not our intention here specifically to speak1 but they evidently have an intimate connection with eruptive prominences1 as well as some relation1 not yet fully understood1 with the corona4 ,of the real cause of sun-spots we know virtually nothing1 but recent studies by ,professor ,hale and others have revealed a strange state of things in the clouds of metallic vapors floating above them and their surroundings4 ,evidences of a cyclonic tendency have been found1 and ,professor ,hale has proved that sun-spots are strong magnetic fields1 and consist of columns of ionized vapors rotating in opposite directions in the two hemispheres4 ,a fact which may have the greatest significance is that titanium and vanadium have been found both in sun-spots and in the remarkable variable ,mira ,ceti1 a star which every eleven months1 or thereabout1 flames up with great brilliancy and then sinks back to invisibility with the naked eye4 ,it has been suggested that sun-spots are indications of the beginning of a process in the sun which will be intensified until it falls into the state of such a star as ,mira4 ,stars very far advanced in evolution1 without showing variability1 also exhibit similar spectra2 so that there is much reason for regarding sunspots as emblems of advancing age4 ,the association of the corona with sun-spots is less evident than that of the eruptive prominences2 still such an association exists1 for the form and extent of the corona vary with the sun-spot period of which we shall presently speak4 ,the constitution of the corona remains to be discovered4 ,it is evidently in part gaseous1 but it also probably contains matter in the form of dust and small meteors4 ,it includes one substance altogether mysterious--8coronium40 ,there are reasons for thinking that this may be the lightest of all the elements1 and ,professor ,young1 its discoverer1 said that it was 8absolutely unique in nature2 utterly distinct from any other known form of matter1 terrestial1 solar1 or cosmical40 ,the enormous extent of the corona is one of its riddles4 ,since the development of the curious subject of the 8pressure of light0 it has been proposed to account for the sustentation of the corona by supposing that it is borne upon the billows of light continually poured out from the sun4 ,experiment has proved1 what mathematical considerations had previously pointed out as probable1 that the waves of light exert a pressure or driving force1 which becomes evident in its effects if the body acted upon is sufficiently small4 ,in that case the light pressure will prevail over the attraction of gravitation1 and propel the attenuated matter away from the sun in the teeth of its attraction4 ,the earth itself would be driven away if1 instead of consisting of a solid globe of immense aggregate mass1 it were a cloud of microscopic particles4 ,the reason is that the pressure varies in proportion to the surface of the body acted upon1 while the gravitational attraction is proportional to the volume1 or the total amount of matter in the body4 ,but the surface of any body depends upon the square of its diameter1 while the volume depends upon the cube of the diameter4 ,if1 for instance1 the diameter is represented by #d1 the surface will be proportional to #d #d1 or #af1 and the volume to #d #d #d1 or #fd2 but if the diameter is taken as #b1 the surface will be #b #b1 or #d1 and the volume #b #b #b1 or #h4 ,now1 the ratio of #d to #h is twice as great as that of #af to #fd4 ,if the diameter is still further decreased1 the ratio of the surface to the volume will proportionally grow larger2 in other words1 the pressure will gain upon the attraction1 and whatever their original ratio may have been1 a time will come1 if the diminution of size continues1 when the pressure will become more effective than the attraction1 and the body will be driven away4 ,supposing the particles of the corona to be below the critical size for the attraction of a mass like that of the sun to control them1 they would be driven off into the surrounding space and appear around the sun like the clouds of dust around a mill4 ,we shall return to this subject in connection with the ,zodiacal ,light1 the ,aurora1 and ,comets4 ,on the other hand1 there are parts of the corona which suggest by their forms the play of electric or magnetic forces4 ,this is beautifully shown in some of the photographs that have been made of the corona during recent eclipses4 ,take1 for instance1 that of the eclipse of #aijj4 ,the sheaves of light emanating from the poles look precisely like the 8lines of force0 surrounding the poles of a magnet4 ,it will be noticed in this photograph that the corona appears to consist of two portions3 one comprising the polar rays just spoken of1 and the other consisting of the broader1 longer1 and less-defined masses of light extending out from the equatorial and middle-latitude zones4 ,yet even in this more diffuse part of the phenomenon one can detect the presence of submerged curves bearing more or less resemblance to those about the poles4 ,just what part electricity or electro-magnetism plays in the mechanism of the solar radiation it is impossible to say1 but on the assumption that it is a very important part is based the hypothesis that there exists a direct solar influence not only upon the magnetism1 but upon the weather of the earth4 ,this hypothesis has been under discussion for half a century1 and still we do not know just how much truth it represents4 ,it is certain that the outbreak of great disturbances on the sun1 accompanied by the formation of sun-spots and the upshooting of eruptive prominences 7phenomena which we should naturally expect to be attended by action71 have been instantly followed by corresponding 8magnetic storms0 on the earth and brilliant displays of the auroral lights4 ,there have been occasions when the influence has manifested itself in the most startling ways1 a great solar outburst being followed by a mysterious gripping of the cable and telegraph systems of the world1 as if an invisible and irresistible hand had seized them4 ,messages are abruptly cut off1 sparks leap from the telegraph instruments1 and the entire earth seems to have been thrown into a magnetic flurry4 ,these occurrences affect the mind with a deep impression of the dependence of our planet on the sun1 such as we do not derive from the more familiar action of the sunlight on the growth of plants and other phenomena of life depending on solar influences4 ,perhaps the theory of solar magnetic influence upon the weather is best known in connection with the 8sun-spot cycle40 ,this1 at any rate1 is1 as already remarked1 closely associated with the corona4 ,its existence was discovered in #ahdc by the ,german astronomer ,schwabe4 ,it is a period of variable length1 averaging about eleven years1 during which the number of spots visible on the sun first increases to a maximum1 then diminishes to a minimum1 and finally increases again to a maximum4 ,for unknown reasons the period is sometimes two or three years longer than the average and sometimes as much shorter4 ,nevertheless1 the phenomena always recur in the same order4 ,starting1 for instance1 with a time when the observer can find few or no spots1 they gradually increase in number and size until a maximum1 in both senses1 is reached1 during which the spots are often of enormous size and exceedingly active4 ,after two or three years they begin to diminish in number1 magnitude1 and activity until they almost or quite disappear4 ,a strange fact is that when a new period opens1 the spots appear first in high northern and southern latitudes1 far from the solar equator1 and as the period advances they not only increase in number and size1 but break out nearer and nearer to the equator1 the last spots of a vanishing period sometimes lingering in the equatorial region after the advance-guard of its successor has made its appearance in the high latitudes4 ,spots are never seen on the equator nor near the poles4 ,it was not very long after the discovery of the sun-spot cycle that the curious observation was made that a striking coincidence existed between the period of the sun-spots and another period affecting the general magnetic condition of the earth4 ,when a curved line representing the varying number of sun-spots was compared with another curve showing the variations in the magnetic state of the earth the two were seen to be in almost exact accord1 a rise in one curve corresponding to a rise in the other1 and a fall to a fall4 ,continued observation has proved that this is a real coincidence and not an accidental one1 so that the connection1 although as yet unexplained1 is accepted as established4 ,but does the influence extend further1 and directly affect the weather and the seasons as well as the magnetic elements of the earth8 ,a final answer to this question cannot yet be given1 for the evidence is contradictory1 and the interpretations put upon it depend largely on the predilections of the judges4 ,but1 in a broad sense1 the sun-spots and the phenomena connected with them must have a relation to terrestial meteorology1 for they prove the sun to be a variable star4 ,reference was made1 a few lines above1 to the resemblance of the spectra of sun-spots to those of certain stars which seem to be failing through age4 ,this in itself is extremely suggestive2 but if this resemblance had never been discovered1 we should have been justified in regarding the sun as variable in its output of energy2 and not only variable1 but probably increasingly so4 ,the very inequalities in the sun-spot cycle are suspicious4 ,when the sun is most spotted its total light may be reduced by one-thousandth part1 although it is by no means certain that its outgiving of thermal radiations is then reduced4 ,a loss of one-thousandth of its luminosity would correspond to a decrease of 4#jjbe of a stellar magnitude1 considering the sun as a star viewed from distant space4 ,so slight a change would not be perceptible2 but it is not alone sun-spots which obscure the solar surface1 its entire globe is enveloped with an obscuring veil4 ,when studied with a powerful telescope the sun's surface is seen to be thickly mottled with relatively obscure specks1 so numerous that it has been estimated that they cut off from one-tenth to one-twentieth of the light that we should receive from it if the whole surface were as brilliant as its brightest parts4 ,the condition of other stars warrants the conclusion that this obscuring envelope is the product of a process of refrigeration which will gradually make the sun more and more variable until its history ends in extinction4 ,looking backward1 we see a time when the sun must have been more brilliant than it is now4 ,at that time it probably shone with the blinding white splendor of such stars as ,sirius1 ,spica1 and ,vega2 now it resembles the relatively dull ,procyon2 in time it will turn ruddy and fall into the closing cycle represented by ,antares4 ,considering that once it must have been more radiantly powerful than at present1 one is tempted to wonder if that could have been the time when tropical life flourished within the earth's polar circles1 sustained by a vivific energy in the sun which it has now lost4 ,the corona1 as we have said1 varies with the sun-spot cycle4 ,when the spots are abundant and active the corona rises strong above the spotted zones1 forming immense beams or streamers1 which on one occasion1 at least1 had an observed length of ten million miles4 ,at the time of a spot minimum the corona is less brilliant and has a different outline4 ,it is then that the curved polar rays are most conspicuous4 ,thus the vast banners of the sun1 shaken out in the eclipse1 are signals to tell of its varying state1 but it will probably be long before we can read correctly their messages4 ,,viii ,the ,zodiacal ,light ,mystery ,there is a singular phenomenon in the sky--one of the most puzzling of all--which has long arrested the attention of astronomers1 defying their efforts at explanation1 but which probably not one in a hundred1 and possibly not one in a thousand1 of the readers of this book has ever seen4 ,yet its name is often spoken1 and it is a conspicuous object if one knows when and where to look for it1 and when well seen it exhibits a mystical beauty which at the same time charms and awes the beholder4 ,it is called 8,the ,zodiacal ,light10 because it lies within the broad circle of the ,zodiac1 marking the sun's apparent annual path through the stars4 ,what it is nobody has yet been able to find out with certainty1 and books on astronomy usually speak of it with singular reserve4 ,but it has given rise to many remarkable theories1 and a true explanation of it would probably throw light on a great many other celestial mysteries4 ,the ,milky ,way is a more wonderful object to look upon1 but its nature can be comprehended1 while there is a sort of uncanniness about the ,zodiacal ,light which immediately impresses one upon seeing it1 for its part in the great scheme of extra-terrestrial affairs is not evident4 ,if you are out-of-doors soon after sunset--say1 on an evening late in the month of ,february--you may perceive1 just after the angry flush of the dying winter's day has faded from the sky1 a pale ghostly presence rising above the place where the sun went down4 ,the writer remembers from boyhood the first time it was pointed out to him and the unearthly impression that it made1 so that he afterward avoided being out alone at night1 fearful of seeing the spectral thing again4 ,the phenomenon brightens slowly with the fading of the twilight1 and soon distinctly assumes the shape of an elongated pyramid of pearly light1 leaning toward the south if the place of observation is in the northern hemisphere4 ,it does not impress the observer at all in the same manner as the ,milky ,way2 that looks far off and is clearly among the stars1 but the ,zodiacal ,light seems closer at hand1 as if it were something more intimately concerning the earth4 ,to all it immediately suggests a connection1 also1 with the sunken sun4 ,if the night is clear and the moon absent 7and if you are in the country1 for city lights ruin the spectacles of the sky71 you will be able to watch the apparition for a long time4 ,you will observe that the light is brightest near the horizon1 gradually fading as the pyramidal beam mounts higher1 but in favorable circumstances it may be traced nearly to the meridian south of the zenith1 where its apex at last vanishes in the starlight4 ,it continues visible during the evenings of ,march and part of ,april1 after which1 ordinarily1 it is seen no more1 or if seen is relatively faint and unimpressive4 ,but when autumn comes it appears again1 this time not like a wraith hovering above the westward tomb of the day-god1 but rather like a spirit of the morning announcing his reincarnation in the east4 ,the reason why the ,zodiacal ,light is best seen in our latitudes at the periods just mentioned is because at those times the ,zodiac is more nearly perpendicular to the horizon1 first in the west and then in the east2 and1 since the phenomenon is confined within the borders of the ,zodiac1 it cannot be favorably placed for observation when the zodiacal plane is but slightly inclined to the horizon4 ,its faint light requires the contrast of a background of dark sky in order to be readily perceptible4 ,but within the tropics1 where the ,zodiac is always at a favorable angle1 the mysterious light is more constantly visible4 ,nearly all observant travelers in the equatorial regions have taken particular note of this phenomenon1 for being so much more conspicuous there than in the temperate zones it at once catches the eye and holds the attention as a novelty4 ,humboldt mentions it many times in his works1 for his genius was always attracted by things out of the ordinary and difficult of explanation1 and he made many careful observations on its shape1 its brilliancy1 and its variations2 for there can be no doubt that it does vary1 and sometimes to an astonishing degree4 ,it is said that it once remained practically invisible in ,europe for several years in succession4 ,during a trip to ,south ,africa in #aiji an ,english astronomer1 ,mr ,e4 ,w4 ,maunder1 found a remarkable difference between the appearance of the ,zodiacal ,light on his going and coming voyages4 ,in fact1 when crossing the equator going south he did not see it at all2 but on returning he had1 on ,march #fth1 when one degree south of the equator1 a memorable view of it4 ,it was a bright1 clear night1 and the ,zodiacal ,light was extraordinarily brilliant--brighter than he had ever seen it before4 ,the ,milky ,way was not to be compared with it4 ,the brightest part extended #ge from the sun4 ,there was a faint and much narrower extension which they could just make out beyond the ,pleiades along the ecliptic1 but the greater part of the ,zodiacal ,light showed as a broad truncated column1 and it did not appear nearly as conical as he had before seen it4 ,when out of the brief twilight of intertropical lands1 where the sun drops vertically to the horizon and night rushes on like a wave of darkness1 the ,zodiacal ,light shoots to the very zenith1 its color is described as a golden tint1 entirely different from the silvery sheen of the ,milky ,way4 ,if ,i may venture again to refer to personal experiences and impressions1 ,i will recall a view of the ,zodiacal ,light from the summit of the cone of ,mt ,etna in the autumn of the year #ahif 7more briefly described in ,astronomy with the ,naked ,eye74 ,there are few lofty mountains so favorably placed as ,etna for observations of this kind4 ,it was once resorted to by ,prof4 ,george ,e4 ,hale1 in an attempt to see the solar corona without an eclipse4 ,rising directly from sea-level to an elevation of nearly eleven thousand feet1 the observer on its summit at night finds himself1 as it were1 lost in the midst of the sky4 ,but for the black flanks of the great cone on which he stands he might fancy himself to be in a balloon4 ,on the occasion to which ,i refer the world beneath was virtually invisible in the moonless night4 ,the blaze of the constellations overhead was astonishingly brilliant1 yet amid all their magnificence my attention was immediately drawn to a great tapering light that sprang from the place on the horizon where the sun would rise later1 and that seemed to be blown out over the stars like a long1 luminous veil4 ,it was the finest view of the ,zodiacal light that ,i had ever enjoyed--thrilling in its strangeness--but ,i was almost disheartened by the indifference of my guide1 to whom it was only a light and nothing more4 ,if he had no science1 he had less poetry--rather a remarkable thing1 ,i thought1 for a child of his clime4 ,the ,light appeared to me to be distinctly brighter than the visible part of the ,milky ,way which included the brilliant stretches in ,auriga and ,perseus1 and its color1 if one may speak of color in connection with such an object1 seemed richer than that of the galactic band2 but ,i did not think of it as yellow1 although ,humboldt has described it as resembling a golden curtain drawn over the stars1 and ,du ,chaillu in ,equatorial ,africa found it of a bright yellow color4 ,it may vary in color as in conspicuousness4 ,the fascination of that extraordinary sight has never faded from my memory4 ,i turned to regard it again and again1 although ,i had never seen the stellar heavens so brilliant1 and it was one of the last things ,i looked for when the morning glow began softly to mount in the east1 and ,sicily and the ,mediterranean slowly emerged from the profound shadow beneath us4 ,the ,zodiacal ,light seems never to have attracted from astronomers in general the amount of careful attention that it deserves2 perhaps because so little can really be made of it as far as explanation is concerned4 ,i have referred to the restraint that scientific writers apparently feel in speaking of it4 ,the grounds for speculation that it affords may be too scanty to lead to long discussions1 yet it piques curiosity1 and as we shall see in a moment has finally led to a most interesting theory4 ,once it was the subject of an elaborate series of studies which carried the observer all round the world4 ,that was in #ahde--df1 during the ,united ,states ,exploring ,expedition that visited the then little known ,japan4 ,the chaplain of the fleet1 the ,rev4 ,mr ,jones1 went out prepared to study the mysterious light in all its phases4 ,he saw it from many latitudes on both sides of the equator1 and the imagination cannot but follow him with keen interest in his world-circling tour1 keeping his eyes every night fixed upon the phantasm overhead1 whose position shifted with that of the hidden sun4 ,he demonstrated that the flow extends at times completely across the celestial dome1 although it is relatively faint directly behind the earth4 ,on his return the government published a large volume of his observations1 in which he undertook to show that the phenomenon was due to the reflection of sunlight from a ring of meteoric bodies encircling the earth4 ,but1 after all1 this elaborate investigation settled nothing4 ,prof4 ,e4 ,e4 ,barnard has more recently devoted much attention to the ,zodiacal ,light1 as well as to a strange attendant phenomenon called the 8,gegenschein10 or ,counterglow1 because it always appears at that point in the sky which is exactly opposite the sun4 ,the ,gegenschein is an extremely elusive phenomenon1 suitable only for eyes that have been specially trained to see it4 ,professor ,newcomb has cautiously remarked that it is said that in that point of the heavens directly opposite the sun there is an elliptical patch of light444 ,this phenomenon is so difficult to account for that its existence is sometimes doubted2 yet the testimony in its favor is difficult to set aside4 ,it certainly cannot be set aside at all since the observations of ,barnard4 ,i recall an attempt to see it under his guidance during a visit to ,mount ,hamilton1 when he was occupied there with the ,lick telescope4 ,of course1 both the ,gegenschein and the ,zodiacal ,light are too diffuse to be studied with telescopes1 which1 so to speak1 magnify them out of existence4 ,they can only be successfully studied with the naked eye1 since every faintest glimmer that they afford must be utilized4 ,this is especially true of the ,gegenschein4 ,at ,mount ,hamilton1 ,mr ,barnard pointed out to me its location with reference to certain stars1 but with all my gazing ,i could not be sure that ,i saw it4 ,to him1 on the contrary1 it was obvious2 he had studied it for months1 and was able to indicate its shape1 its boundaries1 its diameter1 and the declination of its center with regard to the ecliptic4 ,there is not1 of course1 the shadow of a doubt of the existence of the ,gegenschein1 and yet ,i question if one person in a million has ever seen or ever will see it4 ,the ,zodiacal ,light1 on the other hand1 is plain enough1 provided that the time and the circumstances of the observation are properly chosen4 ,in the attempts to explain the ,zodiacal ,light1 the favorite hypothesis has been that it is an appendage of the sun--perhaps simply an extension of the corona in the plane of the ecliptic1 which is not very far from coinciding with that of the sun's equator4 ,this idea is quite a natural one1 because of the evident relation of the light to the position of the sun4 ,the vast extension of the equatorial wings of the corona in #ahgh gave apparent support to this hypothesis2 if the substance of the corona could extend ten million miles from the sun1 why might it not extend even one hundred million1 gradually fading out beyond the orbit of the earth8 ,a variation of this hypothesis assumes that the reflection is due to swarms of meteors circling about the sun1 in the plane of its equator1 all the way from its immediate neighborhood to a distance exceeding that of the earth4 ,but in neither form is the hypothesis satisfactory2 there is nothing in the appearance of the corona to indicate that it extends even as far as the planet ,mercury1 while as to meteors1 the orbits of the known swarms do not accord with the hypothesis1 and we have no reason to believe that clouds of others exist traveling in the part of space where they would have to be in order to answer the requirements of the theory4 ,the extension of the corona in #ahgh did not resemble in its texture the ,zodiacal ,light4 ,now1 it has so often happened in the history of science that an important discovery in one branch has thrown unexpected but most welcome light upon some pending problem in some other branch1 that a strong argument might be based upon that fact alone against the too exclusive devotion of many investigators to the narrow lines of their own particular specialty2 and the ,zodiacal ,light affords a case in point1 when it is considered in connection with recent discoveries in chemistry and physics4 ,from the fact that atoms are compound bodies made up of corpuscles at least a thousand times smaller than the smallest known atom--a fact which astounded most men of science when it was announced a few years ago--a new hypothesis has been developed concerning the nature of the ,zodiacal ,light 7as well as other astronomical riddles71 and this hypothesis comes not from an astronomer1 but from a chemist and physicist1 the ,swede1 ,svante ,arrhenius4 ,in considering an outline of this new hypothesis we need neither accept nor reject it2 it is a case rather for suspension of judgment4 ,to begin with1 it carries us back to the 8pressure of light0 mentioned in the preceding chapter4 ,the manner in which this pressure is believed generally to act was there sufficiently explained1 and it only remains to see how it is theoretically extended to the particles of matter supposed to constitute the ,zodiacal ,light4 ,we know that corpuscles1 or 8fragments of atoms0 negatively electrified1 are discharged from hot bodies4 ,streams of these 8ions0 pour from many flames and from molten metals2 and the impact of the cathode and ultra-violet rays causes them to gush even from cold bodies4 ,in the vast laboratory of the sun it is but reasonable to suppose that similar processes are taking place4 8,as a very hot metal emits these corpuscles10 says ,prof4 ,j4 ,j4 ,thomson1 8it does not seem an improbable hypothesis that they are emitted by that very hot body1 the sun40 ,let it be assumed1 then1 that the sun does emit them2 what happens next8 ,negatively charged corpuscles1 it is known1 serve as nuclei to which particles of matter in the ordinary state are attracted1 and it is probable that those emitted from the sun immediately pick up loads in this manner and so grow in bulk4 ,if they grow large enough the gravitation of the sun draws them back1 and they produce a negative charge in the solar atmosphere4 ,but it is probable that many of the particles do not attain the critical size which1 according to the principles before explained1 would enable the gravitation of the sun to retain them in opposition to the pressure of the waves of light1 and with these particles the light pressure is dominant4 ,clouds of them may be supposed to be continually swept away from the sun into surrounding space1 moving mostly in or near the plane of the solar equator1 where the greatest activity1 as indicated by sunspots and related phenomena1 is taking place4 ,as they pass outward into space many of them encounter the earth4 ,if the earth1 like the moon1 had no atmosphere the particles would impinge directly on its surface1 giving it a negative electric charge4 ,but the presence of the atmosphere changes all that1 for the first of the flying particles that encounter it impart to it their negative electricity1 and then1 since like electric charges repel like1 the storm of particles following will be sheered off from the earth1 and will stream around it in a maze of hyperbolic paths4 ,those that continue on into space beyond the earth may be expected to continue picking up wandering particles of matter until their bulk has become so great that the solar attraction prevails again over the light pressure acting upon them1 and they turn again sunward4 ,passing the earth on their return they will increase the amount of dust-clouds careering round it2 and these will be further increased by the action of the ultra-violet rays of the sunlight causing particles to shoot radially away from the earth when the negative charge of the upper atmosphere has reached a certain amount1 which particles1 although starting sunward1 will be swept back to the earth with the oncoming streams4 ,as the final result of all this accumulation of flying and gyrating particles in the earth's neighborhood1 we are told that the latter must be transformed into the semblance of a gigantic solid-headed comet provided with streaming tails1 the longest of them stretching away from the direction of the sun1 while another shorter one extends toward the sun4 ,this shorter tail is due to the particles that we have just spoken of as being driven sunward from the earth by the action of ultra-violet light4 ,no doubt this whole subject is too technical for popular statement2 but at any rate the general reader can understand the picturesque side of the theory1 for its advocates assure us that if we were on the moon we would doubtless be able to see the comet-like tails of the earth1 and then we could appreciate the part that they play in producing the phenomenon of the ,zodiacal ,light4 ,that the ,light as we see it could be produced by the reflection of sunlight from swarms of particles careering round the earth in the manner supposed by ,arrhenius' hypothesis is evident enough2 and it will be observed that the new theory1 after all1 is only another variant of the older one which attributes the ,zodiacal ,light to an extension of the solar corona4 ,but it differs from the older theory in offering an explanation of the manner in which the extension is effected1 and it differentiates between the corona proper and the streams of negative particles shot away from the sun4 ,in its details the hypothesis of ,arrhenius also affords an explanation of many peculiarities of the ,zodiacal ,light1 such as that it is confined to the neighborhood of the ecliptic1 and that it is stronger on the side of the earth which is just turning away from a position under the sun than on the other side2 but it would carry us beyond our limits to go into these particulars4 ,the ,gegenschein1 according to this theory1 is a part of the same phenomenon as the ,zodiacal ,light1 for by the laws of perspective it is evident that the reflection from the streams of particles situated at a point directly opposite to the sun would be at a maximum1 and this is the place which the ,gegenschein occupies4 ,apart from its geometrical relations to the position of the sun1 the variability of the ,zodiacal ,light appears to affirm its solar dependence1 and this too would be accounted for by ,arrhenius' hypothesis better than by the old theory of coronal extension4 ,the amount of corpuscular discharge from the sun must naturally be governed by the state of relative activity or inactivity of the latter1 and this could not but be reflected in the varying splendor of the ,zodiacal ,light4 ,but much more extended study than has yet been given to the subject will be required before we can feel that we know with reasonable certainty what this mysterious phenomenon really is4 ,by the hypothesis of ,arrhenius every planet that has an atmosphere must have a ,zodiacal ,light attending it1 but the phenomenon is too faint for us to be able to see it in the case1 for instance1 of ,venus1 whose atmosphere is very abundant4 ,the moon has no corresponding 8comet's tail0 because1 as already explained1 of the lack of a lunar atmosphere to repel the streams by becoming itself electrified2 but if there were a lunar ,zodiacal ,light1 no doubt we could see it because of the relative nearness of our satellite4 ,,ix ,marvels of the ,aurora ,one of the most vivid recollections of my early boyhood is that of seeing my father return hastily into the house one evening and call out to the family3 8,come outside and look at the sky60 ,ours was a country house situated on a commanding site1 and as we all emerged from the doorway we were dumbfounded to see the heavens filled with pale flames which ran licking and quivering over the stars4 ,instantly there sprang into my terrified mind the recollection of an awful description of 8the ,day of ,judgment0 7the ,dies ,ir71 which ,i had heard with much perturbation of spirit in the ,dutch ,reformed church from the lips of a tall1 dark-browed1 dreadfully-in-earnest preacher of the old-fashioned type4 ,my heart literally sank at sight of the spectacle1 for it recalled the preacher's very words2 it was just as he had said it would be1 and it needed the assured bearing of my elders finally to convince me that ,that ,day of ,wrath1 ,o dreadful day1 ,when ,heaven and ,earth shall pass away1 ,as ,david and the ,sibyl say had not actually come upon us4 ,and even the older members of the household were not untouched with misgivings when menacing spots of crimson appeared1 breaking out now here1 now there1 in the shuddering sky4 ,toward the north the spectacle was appalling4 ,a huge arch spanned an unnaturally dark segment resting on the horizon1 and above this arch sprang up beams and streamers in a state of incessant agitation1 sometimes shooting up to the zenith with a velocity that took one's breath1 and sometimes suddenly falling into long ranks1 and marching1 marching1 marching1 like an endless phalanx of fiery specters1 and moving1 as ,i remember1 always from east to west4 ,the absolute silence with which these mysterious evolutions were performed and the quavering reflections which were thrown upon the ground increased the awfulness of the exhibition4 ,occasionally enormous curtains of lambent flame rolled and unrolled with a majestic motion1 or were shaken to and fro as if by a mighty1 noiseless wind4 ,at times1 too1 a sudden billowing rush would be made toward the zenith1 and for a minute the sky overhead would glow so brightly that the stars seemed to have been consumed4 ,the spectacle continued with varying intensity for hours4 ,illustration3 ,auroral beams seen in ,england ,this exhibition occurred in ,central ,new ,york1 a latitude in which the ,aurora ,borealis is seldom seen with so much splendor4 ,i remember another similar one seen from the city of ,new ,york in ,november1 #ahhb4 ,on this last occasion some observers saw a great upright beam of light which majestically moved across the heavens1 stalking like an apparition in the midst of the auroral pageant1 of whose general movements it seemed to be independent1 maintaining always its upright posture1 and following a magnetic parallel from east to west4 ,this mysterious beam was seen by no less than twenty-six observers in different parts of the country1 and a comparison of their observations led to a curious calculation indicating that the apparition was about one hundred and thirty-three miles tall and moved at the speed of ten miles per second6 ,illustration3 ,auroral arches of an eliptic form seen in the ,arctic regions ,but1 as everybody knows1 it is in the ,arctic regions that the ,aurora1 or the 8,northern ,lights10 can best be seen4 ,there1 in the long polar night1 when for months together the sun does not rise1 the strange coruscations in the sky often afford a kind of spectral daylight in unison with the weird scenery of the world of ice4 ,the pages in the narratives of ,arctic exploration that are devoted to descriptions of the wonderful effects of the ,northern ,lights are second to none that man has ever penned in their fascination4 ,the lights1 as ,i have already intimated1 display astonishing colors1 particularly shades of red and green1 as they flit from place to place in the sky4 ,the discovery that the magnetic needle is affected by the ,aurora1 quivering and darting about in a state of extraordinary excitement when the lights are playing in the sky1 only added to the mystery of the phenomenon until its electro-magnetic nature had been established4 ,this became evident as soon as it was known that the focus of the displays was the magnetic pole2 and when the far ,south was visited the ,aurora ,australis was found1 having its center at the ,south ,magnetic ,pole4 ,then1 if not before1 it was clear that the earth was a great globular magnet1 having its poles of opposite magnetism1 and that the auroral lights1 whatever their precise cause might be1 were manifestations of the magnetic activity of our planet4 ,after the invention of magnetic telegraphy it was found that whenever a great ,aurora occurred the telegraph lines were interrupted in their operation1 and the ocean cables ceased to work4 ,such a phenomenon is called a 8magnetic storm40 ,the interest excited by the ,aurora in scientific circles was greatly stimulated when1 in the last half of the nineteenth century1 it was discovered that it is a phenomenon intimately associated with disturbances on the sun4 ,the ancient 8,zurich ,chronicles10 extending from the year #ajjj to the year #ahjj1 in which both sun-spots visible to the naked eye and great displays of the auroral lights were recorded1 first set ,rudolf ,wolf on the track of this discovery4 ,the first notable proof of the suspected connection was furnished with dramatic emphasis by an occurrence which happened on ,september #a1 #ahei4 ,near noon on that day two intensely brilliant points suddenly broke out in a group of sun-spots which were under observation by ,mr ,r4 ,c4 ,carrington at his observatory at ,redhill1 ,england4 ,the points remained visible for not more than five minutes1 during which interval they moved thirty-five thousand miles across the solar disk4 ,mr ,r4 ,hodgson happened to see the same phenomenon at his observatory at ,highgate1 and thus all possibility of deception was removed4 ,but neither of the startled observers could have anticipated what was to follow1 and1 indeed1 it was an occurrence which has never been precisely duplicated4 ,i quote the eloquent account given by ,miss ,clerke in her ,history of ,astronomy ,during the ,nineteenth ,century4 ,this unique phenomenon seemed as if specially designed to accentuate the inference of a sympathetic relation between the earth and the sun4 ,from ,august #bh to ,september #d1 #ahei1 a magnetic storm of unparalleled intensity1 extent1 and duration was in progress over the entire globe4 ,telegraphic communication was everywhere interrupted--except1 indeed1 that it was in some cases found practicable to work the lines without batteries by the agency of the earth-currents alone2 sparks issued from the wires2 gorgeous auroras draped the skies in solemn crimson over both hemispheres1 and even in the tropics2 the magnetic needle lost all trace of continuity in its movements and darted to and fro as if stricken with inexplicable panic4 ,the coincidence was even closer4 ,at the very instant of the solar outburst witnessed by ,carrington and ,hodgson the photographic apparatus at ,kew registered a marked disturbance of all the three magnetic elements2 while shortly after the ensuing midnight the electric agitation culminated1 thrilling the whole earth with subtle vibrations1 and lighting up the atmosphere from pole to pole with coruscating splendors which perhaps dimly recall the times when our ancient planet itself shone as a star4 ,if this amazing occurrence stood alone1 and as ,i have already said it has never been exactly duplicated1 doubt might be felt concerning some of the inferences drawn from it2 but in varying forms it has been repeated many times1 so that now hardly anyone questions the reality of the assumed connection between solar outbursts and magnetic storms accompanied by auroral displays on the earth4 ,it is true that the late ,lord ,kelvin raised difficulties in the way of the hypothesis of a direct magnetic action of the sun upon the earth1 because it seemed to him that an inadmissible quantity of energy was demanded to account for such action4 ,but no calculation like that which he made is final1 since all calculations depend upon the validity of the data2 and no authority is unshakable in science1 because no man can possess omniscience4 ,it was ,lord ,kelvin who1 but a few years before the thing was actually accomplished1 declared that aerial navigation was an impracticable dream1 and demonstrated its impracticability by calculation4 ,however the connection may be brought about1 it is as certain as evidence can make it that solar outbursts are coincident with terrestial magnetic disturbances1 and coincident in such a way as to make the inference of a causal connection irresistible4 ,the sun is only a little more than a hundred times its own diameter away from the earth4 ,why1 then1 with the subtle connection between them afforded by the ether which conveys to us the blinding solar light and the life-sustaining solar heat1 should it be so difficult to believe that the sun's enormous electric energies find a way to us also8 ,no doubt the impulse coming from the sun acts upon the earth after the manner of a touch upon a trigger1 releasing energies which are already stored up in our planet4 ,but besides the evidence afforded by such occurrences as have been related of an intimate connection between solar outbreaks and terrestial magnetic flurries1 attended by magnificent auroral displays1 there is another line of proof pointing in the same direction4 ,thus1 it is known that the sun-spot period1 as remarked in a preceding chapter1 coincides in a most remarkable manner with the periodic fluctuations in the magnetic state of the earth4 ,this coincidence runs into the most astonishing details4 ,for instance1 when the sun-spot period shortens1 the auroral period shortens to precisely the same extent2 as the short sun-spot periods usually bring the most intense outbreaks of solar activity1 so the corresponding short auroral periods are attended by the most violent magnetic storms2 a secular period of about two hundred and twenty-two years affecting sun-spots is said to have its auroral duplicate2 a shorter period of fifty-five and a half years1 which some observers believe that they have discovered appears also to be common to the two phenomena2 and yet another 8superposed0 period of about thirty-five years1 which some investigators aver exists1 affects sun-spots and aurora alike4 ,in short1 the coincidences are so numerous and significant that one would have to throw the doctrine of probability to the winds in order to be able to reject the conclusion to which they so plainly lead4 ,illustration3 ,auroral curtain seen in ,scandinavia ,but still the question recurs3 ,how is the influence transmitted8 ,here ,arrhenius comes once more with his hypothesis of negative corpuscles1 or ions1 driven away from the sun by light-pressure--a hypothesis which seems to explain so many things--and offers it also as an explanation of the way in which the sun creates the ,aurora4 ,he would give the ,aurora the same lineage with the ,zodiacal ,light4 ,to understand the application of this theory we must first recall the fact that the earth is a great magnet having its two opposite poles of magnetism1 one near the ,arctic and the other near the ,antarctic ,circle4 ,like all magnets1 the earth is surrounded with 8lines of force10 which1 after the manner of the curved rays we saw in the photograph of a solar eclipse1 start from a pole1 rising at first nearly vertically1 then bend gradually over1 passing high above the equator1 and finally descending in converging sheaves to the opposite pole4 ,now the axis of the earth is so placed in space that it lies at nearly a right angle to the direction of the sun1 and as the streams of negatively charged particles come pouring on from the sun 7see the last preceding chapter71 they arrive in the greatest numbers over the earth's equatorial regions4 ,there they encounter the lines of magnetic force at the place where the latter have their greatest elevation above the earth1 and where their direction is horizontal to the earth's surface4 ,obeying a law which has been demonstrated in the laboratory1 the particles then follow the lines of force toward the poles4 ,while they are above the equatorial regions they do not become luminescent1 because at the great elevation that they there occupy there is virtually no atmosphere2 but as they pass on toward the north and the south they begin to descend with the lines of force1 curving down to meet at the poles2 and1 encountering a part of the atmosphere comparable in density with what remains in an exhausted ,crookes tube1 they produce a glow of cathode rays4 ,this glow is conceived to represent the ,aurora1 which may consequently be likened to a gigantic exhibition of vacuum-tube lights4 ,anybody who recalls his student days in the college laboratory and who has witnessed a display of ,northern ,lights will at once recognize the resemblance between them in colors1 forms1 and behavior4 ,this resemblance had often been noted before ,arrhenius elaborated his hypothesis4 ,without intending to treat his interesting theory as more than a possibly correct explanation of the phenomena of the ,aurora1 we may call attention to some apparently confirmatory facts4 ,one of the most striking of these relates to a seasonal variation in the average number of auror4 ,it has been observed that there are more in ,march and ,september than at any other time of the year1 and fewer in ,june and ,december2 moreover 7and this is a delicate test as applied to the theory71 they are slightly rarer in ,june than in ,december4 ,now all these facts seem to find a ready explanation in the hypothesis of ,arrhenius1 thus3 7#a7 ,the particles issuing from the sun are supposed to come principally from the regions whose excitement is indicated by the presence of sun-spots 7which accords with ,hale's observation that sun-spots are columns of ionized vapors71 and these regions have a definite location on either side of the solar equator1 seldom approaching it nearer than within #e or #aj north or south1 and never extending much beyond #ce toward either pole2 7#b7 ,the equator of the sun is inclined about #g to the plane of the earth's orbit1 from which it results that twice in a year--viz41 in ,june and ,december--the earth is directly over the solar equator1 and twice a year--viz41 in ,march and ,september--when it is farthest north or south of the solar equator1 it is over the inner edge of the sun-spot belts4 ,since the corpuscles must be supposed to be propelled radially from the sun1 few will reach the earth when the latter is over the solar equator in ,june and ,december1 but when it is over1 or nearly over1 the spot belts1 in ,march and ,september1 it will be in the line of fire of the more active parts of the solar surface1 and relatively rich streams of particles will reach it4 ,this1 as will be seen from what has been said above1 is in strict accord with the observed variations in the frequency of auror4 ,even the fact that somewhat fewer auror are seen in ,june than in ,december also finds its explanation in the known fact that the earth is about three million miles nearer the sun in the winter than in the summer1 and the number of particles reaching it will vary1 like the intensity of light1 inversely as the square of the distance4 ,these coincidences are certainly very striking1 and they have a cumulative force4 ,if we accept the theory1 it would appear that we ought to congratulate ourselves that the inclination of the sun's equator is so slight1 for as things stand the earth is never directly over the most active regions of the sun-spots1 and consequently never suffers from the maximum bombardment of charged particles of which the sun is capable4 ,incessant auroral displays1 with their undulating draperies1 flitting colors1 and marching columns might not be objectionable from the point of view of picturesqueness1 but one magnetic storm of extreme intensity following closely upon the heels of another1 for months on end1 crazing the magnetic needle and continually putting the telegraph and cable lines out of commission1 to say nothing of their effect upon 8wireless telegraphy01 would hardly add to the charms of terrestrial existence4 ,illustration3 ,auroral arches seen in ,scandinavia ,one or two other curious points in connection with ,arrhenius' hypothesis may be mentioned4 ,first1 the number of auror1 according to his explanation1 ought to be greatest in the daytime1 when the face of the earth on the sunward side is directly exposed to the atomic bombardment4 ,of course visual observation can give us no information about this1 since the light of the ,aurora is never sufficiently intense to be visible in the presence of daylight1 but the records of the magnetic observatories can be1 and have been1 appealed to for information1 and they indicate that the facts actually accord with the theory4 ,behind the veil of sunlight in the middle of the afternoon1 there is good reason to believe1 auroral exhibitions often take place which would eclipse in magnificence those seen at night if we could behold them4 ,observation shows1 too1 that auror are more frequent before than after midnight1 which is just what we should expect if they originate in the way that ,arrhenius supposes4 ,second1 the theory offers an explanation of the alleged fact that the formation of clouds in the upper air is more frequent in years when auror are most abundant1 because clouds are the result of the condensation of moisture upon floating particles in the atmosphere 7in an absolutely dustless atmosphere there would be no clouds71 and it has been proved that negative ions like those supposed to come from the sun play a master part in the phenomena of cloud formation4 ,yet another singular fact1 almost mystical in its suggestions1 may be mentioned4 ,it seems that the dance of the auroral lights occurs most frequently during the absence of the moon from the hemisphere in which they appear1 and that they flee1 in greater part1 to the opposite hemisphere when the moon's revolution in an orbit considerably inclined to the earth's equator brings her into that where they have been performing4 ,arrhenius himself discovered this curious relation of auroral frequency to the position of the moon north or south of the equator1 and he explains it in this way4 ,the moon1 like the earth1 is exposed to the influx of the ions from the sun2 but having no atmosphere1 or almost none1 to interfere with them1 they descend directly upon her surface and charge her with an electric negative potential to a very high degree4 ,in consequence of this she affects the electric state of the upper parts of the earth's atmosphere where they lie most directly beneath her1 and thus prevents1 to a large extent1 the negative discharges to which the appearance of the ,aurora is due4 ,and so 8the extravagant and erring spirit0 of the ,aurora avoids the moon as ,hamlet's ghost fled at the voice of the cock announcing the awakening of the god of day4 ,there are even other apparent confirmations of the hypothesis1 but we need not go into them4 ,we shall1 however1 find one more application of it in the next chapter1 for it appears to be a kind of cure-all for astronomical troubles2 at any rate it offers a conceivable solution of the question1 ,how does the sun manage to transmit its electric influence to the earth8 ,and this solution is so grandiose in conception1 and so novel in the mental pictures that it offers1 that its acceptance would not in the least detract from the impression that the ,aurora makes upon the imagination4 ,x ,strange ,adventures of ,comets ,the fears and legends of ancient times before ,science was born1 and the superstitions of the ,dark ,ages1 sedulously cultivated for theological purposes by monks and priests1 have so colored our ideas of the influence that comets have had upon the human mind that many readers may be surprised to learn that it was the apparition of a wonderful comet1 that of #ahdc1 which led to the foundation of our greatest astronomical institution1 the ,harvard ,college ,observatory4 ,no doubt the comet superstition existed half a century ago1 as1 indeed1 it exists yet today1 but in this case the marvelous spectacle in the sky proved less effective in inspiring terror than in awakening a desire for knowledge4 ,even in the sixteenth century the views that enlightened minds took of comets tended powerfully to inspire popular confidence in science1 and ,halley's prediction1 after seeing and studying the motion of the comet which appeared in #afhb1 that it would prove to be a regular member of the sun's family and would be seen returning after a period of about seventy-six years1 together with the fulfillment of that prediction1 produced a revulsion from the superstitious notions which had so long prevailed4 ,illustration3 ,swift's comet4 ,taken at ,arequipa1 ,march #cj #ahib ,then the facts were made plain that comets are subject to the law of gravitation equally with the planets2 that there are many which regularly return to the neighborhood of the sun 7perihelion72 and that these travel in orbits differing from those of the planets only in their greater eccentricity1 although they have the peculiarity that they do not1 like the planets1 all go round the sun in the same direction1 and do not keep within the general plane of the planetary system1 but traverse it sometimes from above and sometimes from below4 ,other comets1 including most of the 8great0 ones1 appear to travel in parabolic or1 in a few cases1 hyperbolic orbits1 which1 not being closed curves1 never bring them back again4 ,but it is not certain that these orbits may not be extremely eccentric ellipses1 and that after the lapse of hundreds1 or thousands1 of years the comets that follow them may not reappear4 ,the question is an interesting one1 because if all orbits are really ellipses1 then all comets must be permanent members of the solar system1 while in the contrary case many of them are simply visitors1 seen once and never to be seen again4 ,the hypothesis that comets are originally interlopers might seem to derive some support from the fact that the certainly periodic ones are associated1 in groups1 with the great outer planets1 whose attraction appears to have served as a trap for them by turning them into elliptical orbits and thus making them prisoners in the solar system4 ,jupiter1 owing to his great mass and his commanding situation in the system1 is the chief 8comet-catcher20 but he catches them not for himself1 but for the sun4 ,yet if comets do come originally from without the borders of the planetary system1 it does not1 by any means1 follow that they were wanderers at large in space before they yielded to the overmastering attraction of the sun4 ,investigation of the known cometary orbits1 combined with theoretical considerations1 has led some astronomers to the conclusion that as the sun travels onward through space he 8picks up en route0 cometary masses which1 without belonging strictly to his empire1 are borne along in the same vast 8cosmical current0 that carries the solar system4 ,but while no intelligent person any longer thinks that the appearance of a great comet is a token from the heavenly powers of the approaching death of a mighty ruler1 or the outbreak of a devastating war1 or the infliction of a terrible plague upon wicked mankind1 science itself has discovered mysteries about comets which are not less fascinating because they are more intellectual than the irrational fancies that they have displaced4 ,to bring the subject properly before the mind1 let us see what the principal phenomena connected with a comet are4 ,at the present day comets are ordinarily 8picked up0 with the telescope or the photographic plate before any one except their discoverer is aware of their existence1 and usually they remain so insignificant in appearance that only astronomers ever see them4 ,yet so great is the prestige of the word 8comet0 that the discovery of one of these inconspicuous wanderers1 and its subsequent movements1 become items of the day's news which everybody reads with the feeling1 perhaps1 that at least he knows what is going on in the universe even if he doesn't understand it4 ,but a truly great comet presents quite a different proposition4 ,it1 too1 is apt to be detected coming out of the depths of space before the world at large can get a glimpse of it1 but as it approaches the sun its aspect undergoes a marvelous change4 ,agitated apparently by solar influence1 it throws out a long streaming tail of nebulous light1 directed away from the sun and looking as if blown out like a pennon by a powerful wind4 ,whatever may be the position of the comet with regard to the sun1 as it circles round him it continually keeps its tail on the off side4 ,this1 as we shall soon see1 is a fact of capital importance in relation to the probable nature of comets' tails4 ,almost at the same time that the formation of the tail is observed a remarkable change takes place in the comet's head1 which1 by the way1 is invariably and not merely occasionally its most important part4 ,on approaching the sun the head usually contracts4 ,coincidently with this contraction a nucleus generally makes its appearance4 ,this is a bright1 star-like point in the head1 and it probably represents the totality of solid matter that the comet possesses4 ,but it is regarded as extremely unlikely that even the nucleus consists of a uniformly solid mass4 ,if it were such1 comets would be far more formidable visitors when they pass near the planets than they have been found to be4 ,the diameter of the nucleus may vary from a few hundred up to several thousand miles2 the heads1 on the average1 are from twenty-five thousand to one hundred thousand miles in diameter1 although a few have greatly exceeded these dimensions2 that of the comet of #ahaa1 one of the most stupendous ever seen1 was a million and a quarter miles in diameter6 ,as to the tails1 not withstanding their enormous length--some have been more than a hundred million miles long--there is reason to believe that they are of extreme tenuity1 8as rare as vacuum40 ,the smallest stars have been seen shining through their most brilliant portions with undiminished luster4 ,after the nucleus has been formed it begins to throw out bright jets directed toward the sun4 ,a stream1 and sometimes several streams1 of light also project sunward from the nucleus1 occasionally appearing like a stunted tail directed oppositely to the real tail4 ,symmetrical envelopes which1 seen in section1 appear as half circles or parabolas1 rise sunward from the nucleus1 forming a concentric series4 ,the ends of these stream backward into the tail1 to which they seem to supply material4 ,ordinarily the formation of these ejections and envelopes is attended by intense agitation of the nucleus1 which twists and turns1 swinging and gyrating with an appearance of the greatest violence4 ,sometimes the nucleus is seen to break up into several parts4 ,the entire heads of some comets have been split asunder in passing close around the sun2 ,the comet of #ahhb retreated into space after its perihelion passage with five heads instead of the one that it had originally1 and each of these heads had its own tail6 ,the possession of the spectroscope has enabled astronomers during later years to study the chemical composition of comets by analyzing their light4 ,at first the only substances thus discovered in them were hydro-carbon compounds1 due evidently to the gaseous envelopes in which some combination of hydrogen with carbon existed4 ,behind this gaseous spectrum was found a faint continuous spectrum ascribed to the nucleus1 which apparently both reflects the sunlight and gives forth the light of a glowing solid or liquid4 ,subsequently sodium and iron lines were found in cometary spectra4 ,the presence of iron would seem to indicate that some of these bodies may be much more massive than observations on their attractive effects have indicated4 ,in some recent comets1 such as ,morehouse's1 in #aijh1 several lines have been found1 the origin of which is unknown4 ,without going back of the nineteenth century we may find records of some of the most extraordinary comets that man has ever looked upon4 ,in #ahaa1 still spoken of as 8the year of the comet10 because of the wonderful vintage ascribed to the skyey visitor1 a comet shaped like a gigantic sword amazed the whole world1 and1 as it remained visible for seventeen months1 was regarded by superstitious persons as a symbol of the fearful happenings of ,napoleon's ,russian campaign4 ,this comet1 the extraordinary size of whose head1 greatly exceeding that of the sun itself1 has already been mentioned1 was also remarkable for exhibiting so great a brilliancy without approaching even to the earth's distance from the sun4 ,but there was once a comet 7and only once--in the year #agbi7 which never got nearer to the sun than four times the distance of the earth and yet appeared as a formidable object in the sky4 ,as ,professor ,young has remarked1 8it must have been an enormous comet to be visible from such a distance40 ,and we are to remember that there were no great telescopes in the year #agbi4 ,that comet affects the imagination like a phantom of space peering into the solar system1 displaying its enormous train afar off 7which1 if it had approached as near as other comets1 would probably have become the celestial wonder of all human memory71 and then turning away and vanishing in the depths of immensity4 ,in #ahdc a comet appeared which was so brilliant that it could be seen in broad day close beside the sun6 ,this was the first authenticated instance of that kind1 but the occurrence was to be repeated1 as we shall see in a moment1 less than forty years later4 ,the splendid comet of #aheh1 usually called ,donati's1 is remembered by many persons yet living4 ,it was1 perhaps1 both as seen by the naked eye and with the telescope1 the most beautiful comet of which we have any record4 ,it too marked a rich vintage year1 still remembered in the vineyards of ,france1 where there is a popular belief that a great comet ripens the grape and imparts to the wine a flavor not attainable by the mere skill of the cultivator4 ,there are 8comet wines10 carefully treasured in certain cellars1 and brought forth only when their owner wishes to treat his guests to a sip from paradise4 ,the year #ahfa saw another very remarkable comet1 of an aspect strangely vast and diffuse1 which is believed to have swept the earth with its immense tail when it passed between us and the sun on the night of ,june #cjth1 an event which produced no other known effect than the appearance of an unwonted amount of scattered light in the sky4 ,the next very notable comet was the 8,great ,southern ,comet0 of #ahhj1 which was not seen from the northern hemisphere4 ,it mimicked the aspect of the famous comet of #ahdc1 and to the great surprise of astronomers appeared to be traveling in the same path4 ,this proved to be the rising of the curtain for an astronomical sensation unparalleled in its kind2 for two years later another brilliant comet appeared1 first in the southern hemisphere1 and it too followed the same track4 ,the startling suggestion was now made that this comet was identical with those of #ahdc and #ahhj1 its return having been hastened by the resistance experienced in passing twice through the coronal envelope1 and there were some who thought that it would now swing swiftly round and then plunge straight into the sun1 with consequences that might be disastrous to us on account of the 8flash of heat0 that would be produced by the impact4 ,nervous people were frightened1 but observation soon proved that the danger was imaginary1 for although the comet almost grazed the sun1 and must have rushed through two or three million miles of the coronal region1 no retardation of its immense velocity was perceptible1 and it finally passed away in a damaged condition1 as before remarked1 and has never since appeared4 ,then the probable truth was perceived--viz41 that the three comets 7#ahdc1 #ahhj1 and #ahhb7 were not one identical body1 but three separate ones all traveling in the same orbit4 ,it was found1 too1 that a comet seen in #affh bore similar insignia of relationship4 ,the natural inference was that these four bodies had once formed a single mass which had been split apart by the disruptive action of the sun4 ,strength was lent to this hypothesis by the fact that the comet of #ahhb was apparently torn asunder during its perihelion passage1 retreating into space in a dissevered state4 ,but ,prof4 ,george ,forbes has a theory that the splitting of the original cometary mass was effected by an unknown planet1 probably greater than ,jupiter1 situated at a hundred times the earth's distance from the sun1 and revolving in a period of a thousand years4 ,he supposes that the original comet was not that of #affh1 but one seen in #aeef1 which has since been 8missing10 and that its disruption occurred from an encounter with the supposititious planet about the year #agjj4 ,truly from every point of view comets are the most extraordinary of adventurers6 ,the comet of #ahhb was likewise remarkable for being visible1 like its predecessor of #ahdc1 in full daylight in close proximity to the sun4 ,the story of its detection when almost in contact with the solar disk is dramatic4 ,it had been discovered in the southern hemisphere only a couple of weeks before its perihelion1 which occurred on ,september #agth1 and on the forenoon of that day it was seen by ,doctor ,common in ,england1 and by ,doctor ,elkin and ,mr ,finlay at the ,cape of ,good ,hope1 almost touching the sun4 ,it looked like a dazzling white bird with outspread wings4 ,the southern observers watched it go right into the sun1 when it instantly disappeared4 ,what had happened was that the comet in passing its perihelion point had swung exactly between the earth and the sun4 ,on the following morning it was seen from all parts of the world close by the sun on the opposite side1 and it remained thus visible for three days1 gradually receding from the solar disk4 ,it then became visible for northern observers in the morning sky before sunrise1 brandishing a portentous sword-shaped tail which1 if it had been in the evening sky1 would have excited the wonder of hundreds of millions1 but situated where it was1 comparatively few ever saw it4 ,illustration3 ,daniels' comet4 ,august #aa1 #aijg ,the application of photography to the study of comets has revealed many curious details which might otherwise have escaped detection1 or at best have remained subject to doubt4 ,it has in particular shown not only the precise form of the tails1 but the remarkable vicissitudes that they undergo4 ,professor ,barnard's photographs of ,brooks' comet in #ahic suggested1 by the extraordinary changes in the form of the tail which they revealed1 that the comet was encountering a series of obstructions in space which bent and twisted its tail into fantastic shapes4 ,the reader will observe the strange form into which the tail was thrown on the night of ,october #bast4 ,a cloud of meteors through which the comet was passing might have produced such deformations of its tail4 ,in the photograph of ,daniels' comet of #aijg1 a curious striping of the tail will be noticed4 ,the short bright streaks seen in the photograph1 it may be explained1 are the images of stars which are drawn out into lines in consequence of the fact that the photographic telescope was adjusted to follow the motion of the comet while the stars remained at rest4 ,but the adventures of comets are not confined to possible encounters with unknown obstacles4 ,we have referred to the fact that the great planets1 and especially ,jupiter1 frequently interfere with the motions of comets4 ,this interference is not limited to the original alteration of their orbits from possible parabolas to ellipses1 but is sometimes exercised again and again1 turning the bewildered comets into elliptical paths of all degrees of eccentricity4 ,a famous example of this kind of planetary horse-play is furnished by the story of ,lexell's missing comet4 ,this comet was first seen in #aggj4 ,investigation showed that it was moving in an orbit which should bring it back to perihelion every five and a half years2 yet it had never been seen before and1 although often searched for1 has never been seen since4 ,laplace and ,leverrier proved mathematically that in #agfg it had approached so close to ,jupiter as to be involved among the orbits of his satellites4 ,what its track had been before is not known1 but on that occasion the giant planet seized the interloper1 threw it into a short elliptic orbit and sent it1 like an arrested vagrant1 to receive sentence at the bar of the sun4 ,on this journey it passed within less than #a1ejj1jjj miles of the earth4 ,the form of orbit which ,jupiter had impressed required1 as we have said1 its return in about five and a half years2 but soon after #aggj it had the misfortune a second time to encounter ,jupiter at close range1 and he1 as if dissatisfied with the leniency of the sun1 or indignant at the stranger's familiarity1 seized the comet and hurled it out of the system1 or at any rate so far away that it has never since been able to rejoin the family circle that basks in the immediate rays of the solar hearth4 ,nor is this the only instance in which ,jupiter has dealt summarily with small comets that have approached him with too little deference4 ,illustration3 ,brooks' comet4 ,photographed by ,barnard1 ,october #ba1 #ahic ,the function which ,jupiter so conspicuously fulfills as master of the hounds to the sun is worth considering a little more in detail4 ,to change the figure1 imagine the sun in its voyage through space to be like a majestic battleship surrounded by its scouts4 ,small vessels 7the comets1 as they are overhauled by the squadron1 are taken in charge by the scouts1 with ,jupiter for their chief1 and are forced to accompany the fleet1 but not all are impressed4 ,if a strange comet undertakes to run across ,jupiter's bows the latter brings it to1 and makes prize of it by throwing it into a relatively small ellipse with the sun for its focus4 ,thenceforth1 unless1 as happened to the unhappy comet of ,lexell1 it encounters ,jupiter again in such a way as to be diverted by him into a more distant orbit1 it can never get away4 ,about thirty comets are now known to have thus been captured by the great planet1 and they are called 8,jupiter's ,comet ,family40 ,but1 on the other hand1 if a wandering comet crosses the wake of the chief planetary scout the latter simply drives it away by accelerating its motion and compels it to steer off into open space4 ,the transformation of comets into meteors will be considered in the next chapter1 but here1 in passing1 mention may be made of the strange fate of one member of ,jupiter's family1 ,biela's comet1 which1 having become over bold in its advances to its captor1 was1 after a few revolutions in is impressed orbit1 torn to pieces and turned into a flock of meteors4 ,and now let us return to the mystery of comets' tails4 ,that we are fully justified in speaking of the tails of comets as mysterious is proved by the declaration of ,sir ,john ,herschel1 who averred1 in so many words1 that 8there is some profound secret and mystery of nature concerned in this phenomenon10 and this profound secret and mystery has not yet been altogether cleared up4 ,nevertheless1 the all-explaining hypothesis of ,arrhenius offers us once more a certain amount of aid4 ,comets' tails1 ,arrhenius assures us1 are but another result of the pressure of light4 ,the reader will recall the applications of this theory to the ,zodiacal ,light and the ,aurora4 ,in the form in which we now have to deal with it1 the supposition is made that as a comet approaches the sun eruptions of vapor1 due to the solar heat1 occur in its nucleus4 ,these are naturally most active on the side which is directly exposed to the sun1 whence the appearance of the immense glowing envelopes that surround the nucleus on the sunward side4 ,among the particles of hydro-carbon1 and perhaps solid carbon in the state of fine dust1 which are thus set free there will be many whose size is within the critical limit which enables the light-waves from the sun to drive them away4 ,clouds of such particles1 then1 will stream off behind the advancing comet1 producing the appearance of a tail4 ,this accounts for the fact that the tails of comets are always directed away from the sun1 and it also explains the varying forms of the tails and the extraordinary changes that they undergo4 ,the speed of the particles driven before the light-waves must depend upon their size and weight1 the lightest of a given size traveling the most swiftly4 ,by accretion certain particles might grow1 thus losing velocity and producing the appearance of bunches in the tail1 such as have been observed4 ,the hypothesis also falls in with the researches of ,bredichin1 who has divided the tails of comets into three principal classes--viz43 7#a7 ,those which appear as long1 straight rays2 7#b7 ,those which have the form of curved plumes or scimitars2 7#c7 ,those which are short1 brushy1 and curved sharply backward along the comet's path4 ,in the first type he calculates the repulsive force at from twelve to fifteen times the force of gravity2 in the second at from two to four times2 and in the third at about one and a half times4 ,the straight tails he ascribes to hydrogen because the hydrogen atom is the lightest known2 the sword-shaped tails to hydro-carbons2 and the stumpy tails to vaporized iron4 ,it will be seen that1 if the force driving off the tails is that which ,arrhenius assumes it to be1 the forms of those appendages would accord with those that ,bredichin's theory calls for4 ,at the same time we have an explanation of the multiple tails with which some comets have adorned themselves4 ,the comet of #agdd1 for instance1 had at one time no less than seven tails spread in a wide curved brush behind it4 ,donati's comet of #aheh also had at least two tails1 the principal one sword-shaped and the other long1 narrow1 and as straight as a rule4 ,according to ,bredichin1 the straight tail must have been composed of hydrogen1 and the other of some form of hydro-carbon whose atoms are heavier than those of hydrogen1 and1 consequently1 when swept away by the storm of light-waves1 followed a curvature depending upon the resultant of the forces operating upon them4 ,the seven tails of the comet of #agdd presented a kind of diagram graphically exhibiting its complex composition1 and1 if we knew a little more about the constituents of a comet1 we might be able to say from the amount of curvature of the different tails just what were the seven substances of which that comet consisted4 ,if these theories seem to the reader fantastic1 at any rate they are no more fantastic than the phenomena that they seek to explain4 ,,xi ,meteors1 ,fire-,balls1 and ,meteorites ,one of the most terrorizing spectacles with which the heavens have ever caused the hearts of men to quake occurred on the night of ,november #ac1 #ahcc4 ,on that night ,north ,america1 which faced the storm1 was under a continual rain of fire from about ten o'clock in the evening until daybreak4 ,the fragments of a comet had struck the earth4 ,but the meaning of what had happened was not discovered until long afterward4 ,to the astronomers who1 with astonishment not less than that of other people1 watched the wonderful scene1 it was an unparalleled 8shower of meteors40 ,they did not then suspect that those meteors had once formed the head of a comet4 ,light dawned when1 a year later1 ,prof4 ,denison ,olmsted1 of ,yale ,college1 demonstrated that the meteors had all moved in parallel orbits around the sun1 and that these orbits intersected that of the earth at the point where our planet happened to be on the memorable night of ,november #acth4 ,professor ,olmsted even went so far as to suggest that the cloud of meteors that had encountered the earth might form a diffuse comet2 but full recognition of the fact that they were cometary dbris came later1 as the result of further investigation4 ,the key to the secret was plainly displayed in the spectacle itself1 and was noticed without being understood by thousands of the terror-stricken beholders4 ,it was an umbrella of fire that had opened overhead and covered the heavens2 in other words1 the meteors all radiated from a particular point in the constellation ,leo1 and1 being countless as the snowflakes in a winter tempest1 they ribbed the sky with fiery streaks4 ,professor ,olmsted showed that the radiation of the meteors from a fixed point was an effect of perspective1 and in itself a proof that they were moving in parallel paths when they encountered the earth4 ,the fact was noted that there had been a similar1 but incomparably less brilliant1 display of meteors on the same day of ,november1 #ahcb1 and it was rightly concluded that these had belonged to the same stream1 although the true relationship of the phenomena was not immediately apprehended4 ,olmsted ascribed to the meteors a revolution about the sun once in every six months1 bringing them to the intersection of their orbit with that of the earth every ,november #acth2 but later investigators found that the real period was about thirty-three and one-quarter years1 so that the great displays were due three times in a century1 and their return was confidently predicted for the year #ahff4 ,the appearance of the meteors in #ahcb1 a year before the great display1 was ascribed to the great length of the stream which they formed in space--so great that they required more than two years to cross the earth's orbit4 ,in #ahcb the earth had encountered a relatively rare part of the stream1 but in #ahcc1 on returning to the crossing-place1 it found there the richest part of the stream pouring across its orbit4 ,this explanation also proved to be correct1 and the predicted return in #ahff was duly witnessed1 although the display was much less brilliant than in #ahcc4 ,it was followed by another in #ahfg4 ,illustration3 ,curious forms of meteorite trains ,nos4 #a to #f show the changes undergone by a train left by a meteorite which passed near the 8,great ,dipper02 #g shows the changes and drift of a train seen in the constellation ,virgo2 #h is the singular train of the meteorite of ,february #bb1 #aiji1 near the ,pole ,star4 7,from ,la ,nature47 ,in the mean time ,olmsted's idea of a cometary relationship of the meteors was demonstrated to be correct by the researches of ,schiaparelli and others1 who showed that not only the ,november meteors1 but those of ,august1 which are seen more or less abundantly every year1 traveled in the tracks of well-known comets1 and had undoubtedly an identical origin with those comets4 ,in other words the comets and the meteor-swarms were both remnants of original masses which had probably been split up by the action of the sun1 or of some planet to which they had made close approaches4 ,the annual periodicity of the ,august meteors was ascribed to the fact that the separation had taken place so long ago that the meteors had become distributed all around the orbit1 in consequence of which the earth encountered some of them every year when it arrived at the crossing-point4 ,then ,leverrier showed that the original comet associated with the ,november meteors was probably brought into the system by the influence of the planet ,uranus in the year #abf of the ,christian era4 ,afterward ,alexander ,herschel identified the tracks of no less than seventy-six meteor-swarms 7most of them inconspicuous7 with those of comets4 ,the still more recent researches of ,mr ,w4 ,f4 ,denning make it probable that there are no meteors which do not belong to a flock or system probably formed by the disintegration of a cometary mass2 even the apparently sporadic ones which shoot across the sky1 8lost souls in the night10 being members of flocks which have become so widely scattered that the earth sometimes takes weeks to pass through the region of space where their paths lie4 ,the ,november meteors should have exhibited another pair of spectacles in #ahii and #aijj1 and their failure to do so caused at first much disappointment1 until it was made plain that a good reason existed for their absence4 ,it was found that after their last appearance1 in #ahfg1 they had been disturbed in their movements by the planets ,jupiter and ,saturn1 whose attractions had so shifted the position of their orbit that it no longer intersected that of the earth1 as it did before4 ,whether another planetary interference will sometime bring the principal mass of the ,november meteors back to the former point of intersection with the earth's orbit is a question for the future to decide4 ,it would seem that there may be several parallel streams of the ,november meteors1 and that some of them1 like those of ,august1 are distributed entirely around the orbit1 so that every mid-,november we see a few of them4 ,we come now to a very remarkable example of the disintegration of a comet and the formation of a meteor-stream4 ,in #ahbf ,biela1 of ,josephstadt1 ,austria1 discovered a comet to which his name was given4 ,calculation showed that it had an orbital period of about six and a half years1 belonging to ,jupiter's 8family40 ,on one of its returns1 in #ahdf1 it astonished its watchers by suddenly splitting in two4 ,the two comets thus formed out of one separated to a distance of about one hundred and sixty thousand miles1 and then raced side by side1 sometimes with a curious ligature connecting them1 like ,siamese twins1 until they disappeared together in interplanetary space4 ,in #aheb they came back1 still nearly side by side1 but now the distance between them had increased to a million and a quarter of miles4 ,after that1 at every recurrence of their period1 astronomers looked for them in vain1 until #ahgb1 when an amazing thing happened4 ,on the night of ,november #bhth1 when the earth was crossing the plane of the orbit of the missing comet1 a brilliant shower of meteors burst from the northern sky1 traveling nearly in the track which the comet should have pursued4 ,the astronomers were electrified4 ,klinkerfues1 of ,gttingen1 telegraphed to ,pogson1 of ,madras3 8,biela touched earth2 search near ,theta ,centauri40 ,pogson searched in the place indicated and saw a cometary mass retreating into the southern heavens1 where it was soon swallowed from sight6 ,illustration3 ,section of the atmosphere up to #ajj kilometers4 ,showing the mean elevation at which meteorites and meteors make their appearance4 ,below are shown the elevation of ,mount ,everest1 the highest manned balloon ascent by ,m4 ,berson2 the height of cirrus clouds2 the highest free balloon ascent2 and the elevation attained by the clouds of fire-dust ejected by the ,krakatoa eruption in #ahhc4 7,from ,la ,nature7 ,since then the ,biela meteors have been among the recognized periodic spectacles of the sky1 and few if any doubt that they represent a portion of the missing comet whose disintegration began with the separation into two parts in #ahdf4 ,the comet itself has never since been seen4 ,the first display of these meteors1 sometimes called the 8,andromedes10 because they radiate from the constellation ,andromeda1 was remarkable for the great brilliancy of many of the fire-balls that shot among the shower of smaller sparks1 some of which were described as equaling the full moon in size4 ,none of them is known to have reached the earth1 but during the display of the same meteors in #ahhe a meteoric mass fell at ,mazapil in ,northern ,mexico 7it is now in the ,museum at ,vienna71 which many have thought may actually be a piece of the original comet of ,biela4 ,this brings us to the second branch of our subject4 ,more rare than meteors or falling stars1 and more startling1 except that they never appear in showers1 are the huge balls of fire which occasionally dart through the sky1 lighting up the landscapes beneath with their glare1 leaving trains of sparks behind them1 often producing peals of thunder when they explode1 and in many cases falling upon the earth and burying themselves from a few inches to several feet in the soil1 from which1 more than once1 they have been picked up while yet hot and fuming4 ,these balls are sometimes called bolides4 ,they are not really round in shape1 although they often look so while traversing the sky1 but their forms are fragmentary1 and occasionally fantastic4 ,it has been supposed that their origin is different from that of the true meteors2 it has even been conjectured that they may have originated from the giant volcanoes of the moon or have been shot out from the sun during some of the tremendous explosions that accompany the formation of eruptive prominences4 ,by the same reasoning some of them might be supposed to have come from some distant star4 ,others have conjectured that they are wanderers in space1 of unknown origin1 which the earth encounters as it journeys on1 and ,lord ,kelvin made a suggestion which has become classic because of its imaginative reach--viz41 that the first germs of life may have been brought to the earth by one of these bodies1 8a fragment of an exploded world40 ,it is a singular fact that astronomers and scientific men in general were among the last to admit the possibility of solid masses falling from the sky4 ,the people had believed in the reality of such phenomena from the earliest times1 but the savants shook their heads and talked of superstition4 ,this was the less surprising because no scientifically authenticated instance of such an occurrence was known1 and the stones popularly believed to have fallen from the sky had become the objects of worship or superstitious reverence1 a fact not calculated to recommend them to scientific credence4 ,the celebrated 8black stone0 suspended in the ,kaaba at ,mecca is one of these reputed gifts from heaven2 the 8,palladium0 of ancient ,troy was another2 and a stone which fell near ,ensisheim1 in ,germany1 was placed in a church as an object to be religiously venerated4 ,many legends of falling stones existed in antiquity1 some of them curiously transfigured by the imagination1 like the 8,lion of the ,peloponnesus10 which was said to have sprung down from the sky upon the ,isthmus of ,corinth4 ,but near the beginning of the nineteenth century1 in #ahjc1 a veritable shower of falling stones occurred at ,l',aigle1 in ,northern ,france1 and this time astronomers took note of the phenomenon and scientifically investigated it4 ,thousands of the strange projectiles came from the sky on this occasion1 and were scattered over a wide area of country1 and some buildings were hit4 ,four years later another shower of stones occurred at ,weston1 ,conn41 numbering thousands of individuals4 ,the local alarm created in both cases was great1 as well it might be1 for what could be more intimidating than to find the blue vault of heaven suddenly hurling solid missiles at the homes of men8 ,after these occurrences it was impossible for the most skeptical to doubt any longer1 and the regular study of 8aerolites10 or 8meteorites10 began4 ,one of the first things recognized was the fact that fire-balls are solid meteorites in flight1 and not gaseous exhalations in the air1 as some had assumed4 ,they burn in the air during their flight1 and sometimes1 perhaps1 are entirely consumed before reaching the ground4 ,their velocity before entering the earth's atmosphere is equal to that of the planets in their orbits--viz41 from twenty to thirty miles per second--a fact which proves that the sun is the seat of the central force governing them4 ,their burning in the air is not difficult to explain2 it is the heat of friction which so quickly brings them to incandescence4 ,calculation shows that a body moving through the air at a velocity of about a mile per second will be brought1 superficially1 to the temperature of 8red heat0 by friction with the atmosphere4 ,if its velocity is twenty miles per second the temperature will become thousands of degrees4 ,this is the state of affairs with a meteorite rushing into the earth's atmosphere2 its surface is liquefied within a few seconds after the friction begins to act1 and the melted and vaporized portion of its mass is swept backward1 forming the train of sparks that follows every great fire-ball4 ,however1 there is one phenomenon connected with the trains of meteorites which has never been satisfactorily explained3 they often persist for long periods of time1 drifting and turning with the wind1 but not ceasing to glow with a phosphorescent luminosity4 ,the question is1 ,whence comes this light8 ,it must be light without heat1 since the fine dust or vapor of which the train can only consist would not retain sufficient heat to render it luminous for so long a time4 ,an extremely remarkable incident of this kind occurred on ,february #bb1 #aiji1 when an immense fire-ball that passed over southern ,england left a train that remained visible during two hours1 assuming many curious shapes as it was drifted about by currents in the air4 ,illustration3 ,a meteor photographed in flight ,but notwithstanding the enormous velocity with which meteorites enter the air they are soon slowed down to comparatively moderate speed1 so that when they disappear they are usually traveling not faster than a mile a second4 ,the courses of many have been traced by observers situated along their track at various points1 and thus a knowledge has been obtained of their height above the ground during their flight and of the length of their visible courses4 ,they generally appear at an elevation of eighty or a hundred miles1 and are seldom visible after having descended to within five miles of the ground1 unless the observer happens to be near the striking-point1 when he may actually witness the fall4 ,frequently they burst while high in the air and their fragments are scattered like shrapnel over the surface of the ground1 sometimes covering an area of several square miles1 but of course not thickly2 different fragments of the same meteorite may reach the ground at points several miles apart4 ,the observed length of their courses in the atmosphere varies from fifty to five hundred miles4 ,if they continued a long time in flight after entering the air1 even the largest of them would probably be consumed to the last scrap1 but their fiery career is so short on account of their great speed that the heat does not have time to penetrate very deeply1 and some that have been picked up immediately after their fall have been found cold as ice within4 ,their size after reaching the ground is variable within wide limits2 some are known which weigh several tons1 but the great majority weigh only a few pounds and many only a few ounces4 ,meteorites are of two kinds3 stony meteorites and iron meteorites4 ,the former outnumber the latter twenty to one2 but many stone meteorites contain grains of iron4 ,nickel is commonly found in iron meteorites1 so that it might be said that that redoubtable alloy nickel-steel is of cosmical invention4 ,some twenty-five chemical elements have been found in meteorites1 including carbon and the 8sun-metal10 helium4 ,the presence of the latter is certainly highly suggestive in connection with the question of the origin of meteorites4 ,the iron meteorites1 besides metallic iron and nickel1 of which they are almost entirely composed1 contain hydrogen1 helium1 and carbonic oxide1 and about the only imaginable way in which these gases could have become absorbed in the iron would be through the immersion of the latter while in a molten or vaporized state in a hot and dense atmosphere composed of them1 a condition which we know to exist only in the envelopes of the sun and the stars4 ,the existence of carbon in the ,canyon ,diablo iron meteorites is attended by a circumstance of the most singular character--a very 8fairy tale of science40 ,in some cases the carbon has become diamond6 ,these meteoric diamonds are very small2 nevertheless1 they are true diamonds1 resembling in many ways the little black gems produced by ,moissan's method with the aid of the electric furnace4 ,the fact that they are found embedded in these iron meteorites is another argument in favor of the hypothesis of the solar or stellar origin of the latter4 ,to appreciate this it is necessary to recall the way in which ,moissan made his diamonds4 ,it was by a combination of the effects of great heat1 great pressure1 and sudden or rapid superficial cooling on a mass of iron containing carbon4 ,when he finally broke open his iron he found it a pudding stuffed with miniature black diamonds4 ,when a fragment of the ,canyon ,diablo meteoric iron was polished in ,philadelphia over fifteen years ago it cut the emery-wheel to pieces1 and examination showed that the damage had been effected by microscopic diamonds peppered through the mass4 ,how were those diamonds formed8 ,if the sun or ,sirius was the laboratory that prepared them1 we can get a glimpse at the process of their formation4 ,there is plenty of heat1 plenty of pressure1 and an abundance of vaporized iron in the sun and the stars4 ,when a great solar eruption takes place1 masses of iron which have absorbed carbon may be shot out with a velocity which forbids their return4 ,plunged into the frightful cold of space1 their surfaces are quickly cooled1 as ,moissan cooled his prepared iron by throwing it into water1 and thus the requisite stress is set up within1 and1 as the iron solidifies1 the included carbon crystallizes into diamonds4 ,whether this explanation has a germ of truth in it or not1 at any rate it is evident that iron meteorites were not created in the form in which they come to us2 they must once have been parts of immeasurably more massive bodies than themselves4 ,the fall of meteorites offers an appreciable1 though numerically insignificant1 peril to the inhabitants of the earth4 ,historical records show perhaps three or four instances of people being killed by these bodies4 ,but for the protection afforded by the atmosphere1 which acts as a very effective shield1 the danger would doubtless be very much greater4 ,in the absence of an atmosphere not only would more meteorites reach the ground1 but their striking force would be incomparably greater1 since1 as we have seen1 the larger part of their original velocity is destroyed by the resistance of the air4 ,a meteorite weighing many tons and striking the earth with a velocity of twenty or thirty miles per second1 would probably cause frightful havoc4 ,illustration3 ,looking across ,coon ,butte crater from northern rim ,it is a singular fact that recent investigations seem to have proved that an event of this kind actually happened in ,north ,america--perhaps not longer than a thousand or two thousand years ago4 ,the scene of the supposed catastrophe is in northern central ,arizona1 at ,coon ,butte1 where there is a nearly circular crater in the middle of a circular elevation or small mountain4 ,the crater is somewhat over four thousand feet in diameter1 and the surrounding rim1 formed of upturned strata and ejected rock fragments1 rises at its highest point one hundred and sixty feet above the plain4 ,the crater is about six hundred feet in depth--that is1 from the rim to the visible floor or bottom of the crater4 ,there is no evidence that volcanic action has ever taken place in the immediate neighborhood of ,coon ,butte4 ,the rock in which the crater has been made is composed of horizontal sandstone and limestone strata4 ,between three hundred and four hundred million tons of rock fragments have been detached1 and a large portion hurled by some cause out of the crater4 ,these fragments lie concentrically distributed around the crater1 and in large measure form the elevation known as ,coon ,butte4 ,the region has been famous for nearly twenty years on account of the masses of meteoric iron found scattered about and known as the 8,canyon ,diablo0 meteorites4 ,it was one of these masses1 which consist of nickel-iron containing a small quantity of platinum1 and of which in all some ten tons have been recovered for sale to the various collectors throughout the world1 that as before mentioned destroyed the grinding-tool at ,philadelphia through the cutting power of its embedded diamonds4 ,these meteoric irons are scattered about the crater-hill1 in concentric distribution1 to a maximum distance of about five miles4 ,when the suggestion was first made in #ahif that a monster meteorite might have created by its fall this singular lone crater in stratified rocks1 it was greeted with incredulous smiles2 but since then the matter has assumed a different aspect4 ,the ,standard ,iron ,company1 formed by ,messrs4 ,d4 ,m4 ,barringer1 ,b4 ,c4 ,tilghman1 ,e4 ,j4 ,bennitt1 and ,s4 ,j4 ,holsinger1 having become1 in #aijc1 the owner of this freak of nature1 sunk shafts and bored holes to a great depth in the interior of the crater1 and also trenched the slopes of the mountain1 and the result of their investigations has proved that the meteoric hypothesis of origin is correct4 7,see the papers published in the ,proceedings of the ,academy of ,natural ,sciences of ,philadelphia1 ,december1 #aije1 wherein it is proved that the ,united ,states ,geological ,survey was wrong in believing this crater to have been due to a steam explosion4 ,since that date there has been discovered a great amount of additional confirmatory proof74 ,material of unmistakably meteoric origin was found by means of the drills1 mixed with crushed rock1 to a depth of six hundred to seven hundred feet below the floor of the crater1 and a great deal of it has been found admixed with the ejected rock fragments on the outer slopes of the mountain1 absolutely proving synchronism between the two events1 the formation of this great crater and the falling of the meteoric iron out of the sky4 ,the drill located in the bottom of the crater was sent1 in a number of cases1 much deeper 7over one thousand feet7 into unaltered horizontal red sandstone strata1 but no meteoric material was found below this depth 7seven hundred feet1 or between eleven and twelve hundred feet below the level of the surrounding plain71 which has been assumed as being about the limit of penetration4 ,it is not possible to sink a shaft at present1 owing to the water which has drained into the crater1 and which forms1 with the finely pulverized sandstone1 a very troublesome quicksand encountered at about two hundred feet below the visible floor of the crater4 ,as soon as this water is removed by pumping it will be easy to explore the depths of the crater by means of shafts and drifts4 ,the rock strata 7sandstone and limestone7 of which the walls consist present every appearance of having been violently upturned by a huge body penetrating the earth like a cannon-ball4 ,the general aspect of the crater strikingly resembles the impression made by a steel projectile shot into an armor-plate4 ,mr ,tilghman has estimated that a meteorite about five hundred feet in diameter and moving with a velocity of about five miles per second would have made just such a perforation upon striking rocks of the character of those found at this place4 ,there was some fusion of the colliding masses1 and the heat produced some steam from the small amount of water in the rocks4 ,as a result there has been found at depth a considerable amount of fused quartz 7original sandstone71 and with it innumerable particles or sparks of fused nickel-iron 7original meteorite74 ,a projectile of that size penetrating eleven to twelve hundred feet into the rocky shell of the globe must have produced a shock which was perceptible several hundred miles away4 ,illustration3 ,trail on south side1 ,coon ,butte crater ,the great velocity ascribed to the supposed meteorite at the moment of striking could be accounted for by the fact that it probably plunged nearly vertically downward1 for it formed a circular crater in the rocky crust of the earth4 ,in that case it would have been less retarded by the resistance of the atmosphere than are meteorites which enter the air at a lower angle and shoot ahead hundreds of miles until friction has nearly destroyed their original motion when they drop upon the earth4 ,some meteoric masses of great size1 such as ,peary's iron meteorite found at ,cape ,york1 ,greenland1 and the almost equally large mass discovered at ,bacubirito1 ,mexico1 appear to have penetrated but slightly on striking the earth4 ,this may be explained by supposing that they pursued a long1 horizontal course through the air before falling4 ,the result would be that1 their original velocity having been practically destroyed1 they would drop to the ground with a velocity nearly corresponding to that which gravity would impart within the perpendicular distance of their final fall4 ,a six-hundred-and-sixty-pound meteorite1 which fell at ,knyahinya1 ,hungary1 striking at an angle of #bg from the vertical1 penetrated the ground to a depth of eleven feet4 ,it has been remarked that the ,coon ,butte meteorite may have fallen not longer ago than a few thousand years4 ,this is based upon the fact that the geological indications favor the supposition that the event did not occur more than five thousand years ago1 while on the other hand the rings of growth in the cedar-trees growing on the slopes of the crater show that they have existed there about seven hundred years4 ,prof4 ,william ,h4 ,pickering has recently correlated this with an ancient chronicle which states that at ,cairo1 ,egypt1 in the year #ajbi1 8many stars passed with a great noise40 ,he remarks that ,cairo is about #ajj1 by great circle1 from ,coon ,butte1 so that if the meteorite that made the crater was a member of a flock of similar bodies which encountered the earth moving in parallel lines1 some of them might have traversed the sky tangent to the earth's surface at ,cairo4 ,that the spectacle spoken of in the chronicle was caused by meteorites he deems exceedingly probable because of what is said about 8a great noise20 meteorites are the only celestial phenomena attended with perceptible sounds4 ,professor ,pickering conjectures that this supposed flock of great meteorites may have formed the nucleus of a comet which struck the earth1 and he finds confirmation of the idea in the fact that out of the ten largest meteorites known1 no less than seven were found within nine hundred miles of ,coon ,butte4 ,it would be interesting if we could trace back the history of that comet1 and find out what malicious planet caught it up in its innocent wanderings and hurled it with so true an aim at the earth6 ,this remarkable crater is one of the most interesting places in the world1 for there is absolutely no record of such a mass1 possibly an iron-headed comet1 from outer space having come into collision with our earth4 ,the results of the future exploration of the depths of the crater will be awaited with much interest4 ,,xii ,the ,wrecking of the ,moon ,there are sympathetic moods under whose influence one gazes with a certain poignant tenderness at the worn face of the moon2 that little 8fossil world0 7the child of our mother earth1 too7 bears such terrible scars of its brief convulsive life that a sense of pity is awakened by the sight4 ,the moon is the wonder-land of the telescope4 ,those towering mountains1 whose 8proud aspiring peaks0 cast silhouettes of shadow that seem drawn with india-ink2 those vast plains1 enchained with gentle winding hills and bordered with giant ranges2 those oval 8oceans10 where one looks expectant for the flash of wind-whipped waves2 those enchanting 8bays0 and recesses at the seaward feet of the ,alps2 those broad straits passing between guardian heights incomparably mightier than ,gibraltar2 those locket-like valleys as secluded among their mountains as the ,vale of ,cashmere2 those colossal craters that make us smile at the pretensions of ,vesuvius1 ,etna1 and ,cotopaxi2 those strange white ways which pass with the unconcern of ,roman roads across mountain1 gorge1 and valley--all these give the beholder an irresistible impression that it is truly a world into which he is looking1 a world akin to ours1 and yet no more like our world than ,pompeii is like ,naples4 ,its air1 its waters1 its clouds1 its life are gone1 and only a skeleton remains--a mute but eloquent witness to a cosmical tragedy without parallel in the range of human knowledge4 ,one cannot but regret that the moon1 if it ever was the seat of intelligent life1 has not remained so until our time4 ,think what the consequences would have been if this other world at our very door had been found to be both habitable and inhabited6 ,we talk rather airily of communicating with ,mars by signals2 but ,mars never approaches nearer than #ce1jjj1jjj miles1 while the moon when nearest is only a little more than #bbj1jjj miles away4 ,given an effective magnifying power of five thousand diameters1 which will perhaps be possible at the mountain observatories as telescopes improve1 and we should be able to bring the moon within an apparent distance of about forty miles1 while the corresponding distance for ,mars would be more than seven thousand miles4 ,but even with existing telescopic powers we can see details on the moon no larger than some artificial constructions on the earth4 ,st ,peter's at ,rome1 with the ,vatican palace and the great piazza1 if existing on the moon1 would unquestionably be recognizable as something else than a freak of nature4 ,large cities1 with their radiating lines of communication1 would at once betray their real character4 ,cultivated tracts1 and the changes produced by the interference of intelligent beings1 would be clearly recognizable4 ,the electric illumination of a large town at night would probably be markedly visible4 ,gleams of reflected sunlight would come to us from the surfaces of the lakes and oceans1 and a huge 8liner0 traversing a lunar sea could probably be followed by its trail of smoke4 ,as to communications by 8wireless0 signals1 which certain enthusiasts have thought of in connection with ,mars1 in the case of the moon they should be a relatively simple matter1 and the feat might actually be accomplished4 ,think what a literature would grow up about the moon if it were a living world6 ,its very differences from the earth would only accentuate its interest for us4 ,night and day on the moon are each two weeks in length2 how interesting it would be to watch the manner in which the lunarians dealt with such a situation as that4 ,lunar and terrestrial history would keep step with each other1 and we should record them both4 ,truly one might well wish to have a neighbor world to study2 one would feel so much the less alone in space4 ,it is not impossible that the moon did at one time have inhabitants of some kind4 ,but1 if so1 they vanished with the disappearance of its atmosphere and seas1 or with the advent of its cataclysmic age4 ,at the best1 its career as a living world must have been brief4 ,if the water and air were gradually absorbed1 as some have conjectured1 by its cooling interior rocks1 its surface might1 nevertheless1 have retained them for long ages2 but if1 as others think1 their disappearance was due to the escape of their gaseous molecules in consequence of the inability of the relatively small lunar gravitation to retain them1 then the final catastrophe must have been as swift as it was inevitable4 ,accepting ,darwin's hypothesis1 that the moon was separated from the earth by tidal action while both were yet plastic or nebulous1 we may reasonably conclude that it began its career with a good supply of both water and air1 but did not possess sufficient mass to hold them permanently4 ,yet it may have retained them long enough for life to develop in many forms upon its surface2 in fact1 there are so many indications that air and water have not always been lacking to the lunar world that we are driven to invent theories to explain both their former presence and their present absence4 ,illustration3 ,the craters ,clavius1 ,longomontanus1 ,tycho1 etc4 ,but whatever the former condition of the moon may have been1 its existing appearance gives it a resistless fascination1 and it bears so clearly the story of a vast catastrophe sculptured on its rocky face that the thoughtful observer cannot look upon it without a feeling of awe4 ,the gigantic character of the lunar features impresses the beholder not less than the universality of the play of destructive forces which they attest4 ,let us make a few comparisons4 ,take the lunar crater called 8,tycho01 which is a typical example of its kind4 ,in the telescope ,tycho appears as a perfect ring surrounding a circular depression1 in the center of which rises a group of mountains4 ,its superficial resemblance to some terrestrial volcanic craters is very striking4 ,vesuvius1 seen from a point vertically above1 would no doubt look something like that 7the resemblance would have been greater when the ,monte del ,cavallo formed a more complete circuit about the crater cone74 ,but compare the dimensions4 ,the remains of the outer crater ring of ,vesuvius are perhaps half a mile in diameter1 while the active crater itself is only two or three hundred feet across at the most2 ,tycho has a diameter of fifty-four miles6 ,the group of relatively insignificant peaks in the center of the crater floor of ,tycho is far more massive than the entire mountain that we call ,vesuvius4 ,the largest known volcanic crater on the earth1 ,aso ,san1 in ,japan1 has a diameter of seven miles2 it would take sixty craters like ,aso ,san to equal ,tycho in area6 ,and ,tycho1 though one of the most perfect1 is by no means the largest crater on the moon4 ,another1 called 8,theophilus10 has a diameter of sixty-four miles1 and is eighteen thousand feet deep4 ,there are hundreds from ten to forty miles in diameter1 and thousands from one to ten miles4 ,they are so numerous in many places that they break into one another1 like the cells of a crushed honeycomb4 ,the lunar craters differ from those of the earth more fundamentally than in the matter of mere size2 they are not situated on the tops of mountains4 ,if they were1 and if all the proportions were the same1 a crater like ,tycho might crown a conical peak fifty or one hundred miles high6 ,instead of being cavities in the summits of mountains1 the lunar craters are rather gigantic sink-holes whose bottoms in many cases lie two or three miles below the general surface of the lunar world4 ,around their rims the rocks are piled up to a height of from a few hundred to two or three thousand feet1 with a comparatively gentle inclination1 but on the inner side they fall away in gigantic broken precipices which make the dizzy cliffs of the ,matterhorn seem but 8lover's leaps40 ,down they drop1 ridge below ridge1 crag under crag1 tottering wall beneath wall1 until1 in a crater named 8,newton10 near the south lunar pole1 they attain a depth where the rays of the sun never reach4 ,nothing more frightful than the spectacle which many of these terrible chasms present can be pictured by the imagination4 ,as the lazy lunar day slowly advances1 the sunshine1 unmitigated by clouds or atmospheric veil of any kind1 creeps across their rims and begins to descend the opposite walls4 ,presently it strikes the ragged crest of a ridge which had lain hidden in such darkness as we never know on the earth1 and runs along it like a line of kindling fire4 ,rocky pinnacles and needles shoot up into the sunlight out of the black depths4 ,down sinks the line of light1 mile after mile1 and continually new precipices and cliffs are brought into view1 until at last the vast floor is attained and begins to be illuminated4 ,in the meanwhile the sun's rays1 darting across the gulf1 have touched the summits of the central peaks1 twenty or thirty miles from the crater's inmost edge1 and they immediately kindle and blaze like huge stars amid the darkness4 ,so profound are some of these awful craters that days pass before the sun has risen high enough above them to chase the last shadows from their depths4 ,although several long ranges of mountains resembling those of the earth exist on the moon1 the great majority of its elevations assume the crateriform aspect4 ,sometimes1 instead of a crater1 we find an immense mountain ring whose form and aspect hardly suggest volcanic action4 ,but everywhere the true craters are in evidence1 even on the sea-beds1 although they attain their greatest number and size on those parts of the moon--covering sixty per cent of its visible surface--which are distinctly mountainous in character and which constitute its most brilliant portions4 ,broadly speaking1 the southwestern half of the moon is the most mountainous and broken1 and the northeastern half the least so4 ,right down through the center1 from pole to pole1 runs a wonderful line of craters and crateriform valleys of a magnitude stupendous even for the moon4 ,another similar line follows the western edge4 ,three or four 8seas0 are thrust between these mountainous belts4 ,by the effects of 8libration0 parts of the opposite hemisphere of the moon which is turned away from the earth are from time to time brought into view1 and their aspect indicates that that hemisphere resembles in its surface features the one which faces the earth4 ,there are many things about the craters which seem to give some warrant for the hypothesis which has been particularly urged by ,mr ,g4 ,k4 ,gilbert1 that they were formed by the impact of meteors2 but there are also many things which militate against that idea1 and1 upon the whole1 the volcanic theory of their origin is to be preferred4 ,the enormous size of the lunar volcanoes is not so difficult to account for when we remember how slight is the force of lunar gravity as compared with that of the earth4 ,with equal size and density1 bodies on the moon weigh only one-sixth as much as on the earth4 ,impelled by the same force1 a projectile that would go ten miles on the earth would go sixty miles on the moon4 ,a lunar giant thirty-five feet tall would weigh no more than an ordinary son of ,adam weighs on his greater planet4 ,to shoot a body from the earth so that it would not drop back again1 we should have to start it with a velocity of seven miles per second2 a mile and a half per second would serve on the moon4 ,it is by no means difficult to believe1 then1 that a lunar volcano might form a crater ring eight or ten times broader than the greatest to be found on the earth1 especially when we reflect that in addition to the relatively slight force of gravity1 the materials of the lunar crust are probably lighter than those of our terrestrial rocks4 ,illustration3 ,western part of the ,mare ,serenitatis ,for similar reasons it seems not impossible that the theory mentioned in a former chapter--that some of the meteorites that have fallen upon the earth originated from the lunar volcanoes--is well founded4 ,this would apply especially to the stony meteorites1 for it is hardly to be supposed that the moon1 at least in its superficial parts1 contains much iron4 ,it is surely a scene most strange that is thus presented to the mind's eye--that little attendant of the earth's 7the moon has only one-fiftieth of the volume1 and only one-eightieth of the mass of the earth7 firing great stones back at its parent planet6 ,and what can have been the cause of this furious outbreak of volcanic forces on the moon8 ,evidently it was but a passing stage in its history2 it had enjoyed more quiet times before4 ,as it cooled down from the plastic state in which it parted from the earth1 it became incrusted after the normal manner of a planet1 and then oceans were formed1 its atmosphere being sufficiently dense to prevent the water from evaporating and the would-be oceans from disappearing continually in mist4 ,this1 if any1 must have been the period of life in the lunar world4 ,as we look upon the vestiges of that ancient world buried in the wreck that now covers so much of its surface1 it is difficult to restrain the imagination from picturing the scenes which were once presented there2 and1 in such a case1 should the imagination be fettered8 ,we give it free rein in terrestrial life1 and it rewards us with some of our greatest intellectual pleasures4 ,the wonderful landscapes of the moon offer it an ideal field with just enough half-hidden suggestions of facts to stimulate its powers4 ,the great plains of the ,mare ,imbrium and the ,mare ,serenitatis 7the 8,sea of ,showers0 and the 8,sea of ,serenity071 bordered in part by lofty mountain ranges precisely like terrestrial mountains1 scalloped along their shores with beautiful bays curving back into the adjoining highlands1 and united by a great strait passing between the nearly abutting ends of the 8,lunar ,apennines0 and the 8,lunar ,caucasus10 offer the elements of a scene of world beauty such as it would be difficult to match upon our planet4 ,look at the finely modulated bottom of the ancient sea in ,mr ,ritchey's exquisite photograph of the western part of the ,mare ,serenitatis1 where one seems to see the play of the watery currents heaping the ocean sands in waving lines1 making shallows1 bars1 and deeps for the mariner to avoid or seek1 and affording a playground for the creatures of the main4 ,what geologist would not wish to try his hammer on those rocks with their stony pages of fossilized history8 ,there is in us an instinct which forbids us to think that there was never any life there4 ,if we could visit the moon1 there is not among us a person so prosaic and unimaginative that he would not1 the very first thing1 begin to search for traces of its inhabitants4 ,we would look for them in the deposits on the sea bottoms2 we would examine the shores wherever the configuration seemed favorable for harbors and the sites of maritime cities--forgetting that it may be a little ridiculous to ascribe to the ancient lunarians the same ideas that have governed the development of our race2 we would search through the valleys and along the seeming courses of vanished streams2 we would explore the mountains1 not the terrible craters1 but the pinnacled chains that recall our own ,alps and ,rockies2 seeking everywhere some vestige of the transforming presence of intelligent life4 ,perhaps we should find such traces1 and perhaps1 with all our searching1 we should find nothing to suggest that life had ever existed amid that universal ruin4 ,illustration3 ,mare ,tranquilitatis and surroundings ,look again at the border of the 8,sea of ,serenity0--what a name for such a scene6--and observe how it has been rent with almost inconceivable violence1 the wall of the colossal crater ,posidonius dropping vertically upon the ancient shore and obliterating it1 while its giant neighbor1 ,le ,monnier1 opens a yawning mouth as if to swallow the sea itself4 ,a scene like this makes one question whether1 after all1 those may not be right who have imagined that the so-called sea bottoms are really vast plains of frozen lava which gushed up in floods so extensive that even the mighty volcanoes were half drowned in the fiery sea4 ,this suggestion becomes even stronger when we turn to another of the photographs of ,mr ,ritchey's wonderful series1 showing a part of the ,mare ,tranquilitatis 78,sea of ,tranquility0674 ,notice how near the center of the picture the outline of a huge ring with radiating ridges shows through the sea bottom2 a fossil volcano submerged in a petrified ocean6 ,this is by no means the only instance in which a buried world shows itself under the great lunar plains4 ,yet1 as the newer craters in the sea itself prove1 the volcanic activity survived this other catastrophe1 or broke out again subsequently1 bringing more ruin to pile upon ruin4 ,yet notwithstanding the evidence which we have just been considering in support of the hypothesis that the 8seas0 are lava floods1 ,messrs4 ,loewy and ,puiseux1 the selenographers of the ,paris ,observatory1 are convinced that these great plains bear characteristic marks of the former presence of immense bodies of water4 ,in that case we should be forced to conclude that the later oceans of the moon lay upon vast sheets of solidified lava2 and thus the catastrophe of the lunar world assumes a double aspect1 the earliest oceans being swallowed up in molten floods issuing from the interior1 while the lands were reduced to chaos by a universal eruption of tremendous volcanoes2 and then a period of comparative quiet followed1 during which new seas were formed1 and new life perhaps began to flourish in the lunar world1 only to end in another cataclysm1 which finally put a term to the existence of the moon as a life-supporting world4 ,suppose we examine two more of ,mr ,ritchey's illuminating photographs1 and1 first1 the one showing the crater ,theophilus and its surroundings4 ,we have spoken of ,theophilus before1 citing the facts that it is sixty-four miles in diameter and eighteen thousand feet deep4 ,it will be noticed that it has two brother giants--,cyrillus the nearer1 and ,catharina the more distant2 but ,theophilus is plainly the youngest of the trio4 ,centuries1 and perhaps thousands of years1 must have elapsed between the periods of their upheaval1 for the two older craters are partly filled with dbris1 while it is manifest at a glance that when the south eastern wall of ,theophilus was formed1 it broke away and destroyed a part of the more ancient ring of ,cyrillus4 ,there is no more tremendous scene on the moon than this2 viewed with a powerful telescope1 it is absolutely appalling4 ,illustration3 ,lunar craters ,theophilus and surrounding region ,the next photograph shows1 if possible1 a still wilder region4 ,it is the part of the moon lying between ,tycho and the south pole4 ,tycho is seen in the lower left-hand part of the picture4 ,to the right1 at the edge of the illuminated portion of the moon1 are the crater-rings1 ,longomontanus and ,wilhelm ,i1 the former being the larger4 ,between them are to be seen the ruins of two or three more ancient craters which1 together with portions of the walls of ,wilhelm ,i and ,longomontanus1 have been honeycombed with smaller craters4 ,the vast crateriform depression above the center of the picture is ,clavius1 an unrivaled wonder of lunar scenery1 a hundred and forty-two miles in its greatest length1 while its whole immense floor has sunk two miles below the general surface of the moon outside the ring4 ,the monstrous shadow-filled cavity above ,clavius toward the right is ,blancanus1 whose aspect here gives a good idea of the appearance of these chasms when only their rims are in the sunlight4 ,but observe the indescribable savagery of the entire scene4 ,it looks as though the spirit of destruction had gone mad in this spot4 ,the mighty craters have broken forth one after another1 each rending its predecessor2 and when their work was finished1 a minor but yet tremendous outbreak occurred1 and the face of the moon was gored and punctured with thousands of smaller craters4 ,these relatively small craters 7small1 however1 only in a lunar sense1 for many of them would appear gigantic on the earth7 recall once more the theory of meteoric impact4 ,it does not seem impossible that some of them may have been formed by such an agency4 ,one would not wish for our planet such a fate as that which has overtaken the moon1 but we cannot be absolutely sure that something of the kind may not be in store for it4 ,we really know nothing of the ultimate causes of volcanic activity1 and some have suggested that the internal energies of the earth may be accumulating instead of dying out1 and may never yet have exhibited their utmost destructive power4 ,perhaps the best assurance that we can find that the earth will escape the catastrophe that has overtaken its satellite is to be found in the relatively great force of its gravitation4 ,the moon has been the victim of its weakness2 given equal forces1 and the earth would be the better able to withstand them4 ,it is significant1 in connection with these considerations1 that the little planet ,mercury1 which seems also to have parted with its air and water1 shows to the telescope some indications that it is pitted with craters resembling those that have torn to pieces the face of the moon4 ,upon the whole1 after studying the dreadful lunar landscapes1 one cannot feel a very enthusiastic sympathy with those who are seeking indications of the continued existence of some kind of life on the moon2 such a world is better without inhabitants4 ,it has met its fate2 let it go6 ,fortunately1 it is not so near that it cannot hide its scars and appear beautiful--except when curiosity impels us to look with the penetrating eyes of the astronomer4 ,illustration3 ,mare ,crisium ,,xiii ,the ,great ,mars ,problem ,let any thoughtful person who is acquainted with the general facts of astronomy look up at the heavens some night when they appear in their greatest splendor1 and ask himself what is the strongest impression that they make upon his mind4 ,he may not find it easy to frame an answer1 but when he has succeeded it will probably be to the effect that the stars give him an impression of the universality of intelligence2 they make him feel1 as the sun and the moon cannot do1 that his world is not alone2 that all this was not made simply to form a gorgeous canopy over the tents of men4 ,if he is of a devout turn of mind1 he thinks1 as he gazes into those fathomless deeps and among those bewildering hosts1 of the infinite multitude of created beings that the ,almighty has taken under his care4 ,the narrow ideas of the old geocentric theology1 which made the earth ,god's especial footstool1 and man his only rational creature1 fall away from him like a veil that had obscured his vision2 they are impossible in the presence of what he sees above4 ,thus the natural tendency1 in the light of modern progress1 is to regard the universe as everywhere filled with life4 ,but science1 which is responsible for this broadening of men's thoughts concerning the universality of life1 itself proceeds to set limits4 ,of spiritual existences it pretends to know nothing1 but as to physical beings1 it declares that it can only entertain the supposition of their existence where it finds evidence of an environment suited to their needs1 and such environment may not everywhere exist4 ,science1 though repelled by the antiquated theological conception of the supreme isolation of man among created beings1 regards with complacency the probability that there are regions in the universe where no organic life exists1 stars which shine upon no inhabited worlds1 and planets which nourish no animate creatures4 ,the astronomical view of the universe is that it consists of matter in every stage of evolution3 some nebulous and chaotic2 some just condensing into stars 7suns7 of every magnitude and order2 some shaped into finished solar bodies surrounded by dependent planets2 some forming stars that perhaps have no planets1 and will have none2 some constituting suns that are already aging1 and will soon lose their radiant energy and disappear2 and some aggregated into masses that long ago became inert1 cold1 and rayless1 and that can only be revivified by means about which we can form conjectures1 but of which we actually know nothing4 ,as with the stars1 so with the planets1 which are the satellites of stars4 ,all investigations unite to tell us that the planets are not all in the same state of development4 ,as some are large and some small1 so some are1 in an evolutionary sense1 young1 and some old4 ,as they depend upon the suns around which they revolve for their light1 heat1 and other forms of radiant energy1 so their condition varies with their distance from those suns4 ,many may never arrive at a state suitable for the maintenance of life upon their surfaces2 some which are not at present in such a state may attain it later2 and the forms of life themselves may vary with the peculiar environment that different planets afford4 ,thus we see that we are not scientifically justified in affirming that life is ubiquitous1 although we are thus justified in saying that it must be1 in a general sense1 universal4 ,we might liken the universe to a garden known to contain every variety of plant4 ,if on entering it we see no flowers1 we examine the species before us and find that they are not of those which bloom at this particular season1 or perhaps they are such as never bear flowers4 ,yet we feel no doubt that we shall find flowers somewhere in the garden1 because there are species which bloom at this season1 and the garden contains all varieties4 ,while it is tacitly assumed that there are planets revolving around other stars than the sun1 it would be impossible for us to see them with any telescope yet invented1 and no instrument now in the possession of astronomers could assure us of their existence2 so the only planetary system of which we have visual knowledge is our own4 ,excluding the asteroids1 which could not from any point of view be considered as habitable1 we have in the solar system eight planets of various sizes and situated at various distances from the sun4 ,of these eight we know that one1 the earth1 is inhabited4 ,the question1 then1 arises3 ,are there any of the others which are inhabited or habitable8 ,since it is our intention to discuss the habitability of only one of the seven to which the question applies1 the rest may be dismissed in a few words4 ,the smallest of them1 and the nearest to the sun1 is ,mercury1 which is regarded as uninhabitable because it has no perceptible supply of water and air1 and because1 owing to the extraordinary eccentricity of its orbit1 it is subjected to excessive and very rapid alterations in the amount of solar heat and light poured upon its surface1 such alterations being inconsistent with the supposition that it can support living beings4 ,even its average temperature is more than six and a half times that prevailing on the earth6 ,another circumstance which militates against its habitability is that1 according to the results of the best telescopic studies1 it always keeps the same face toward the sun1 so that one half of the planet is perpetually exposed to the fierce solar rays1 and the other half faces the unmitigated cold of open space4 ,venus1 the next in distance from the sun1 is almost the exact twin of the earth in size1 and many arguments may be urged in favor of its habitability1 although it is suspected of possessing the same peculiarity as ,mercury1 in always keeping the same side sunward4 ,unfortunately its atmosphere appears to be so dense that no permanent markings on its surface are certainly visible1 and the question of its actual condition must1 for the present1 be left in abeyance4 ,mars1 the first planet more distant from the sun than the earth1 is the special subject of this chapter1 and will be described and discussed a few lines further on4 ,jupiter1 ,saturn1 ,uranus1 and ,neptune1 the four giant planets1 all more distant than ,mars1 and each more distant than the other in the order named1 are all regarded as uninhabitable because none of them appears to possess any degree of solidity4 ,they may have solid or liquid nuclei1 but exteriorly they seem to be mere balls of cloud4 ,of course1 one can imagine what he pleases about the existence of creatures suited to the physical constitution of such planets as these1 but they must be excluded from the category of habitable worlds in the ordinary sense of the term4 ,we go back1 then1 to ,mars4 ,it will be best to begin with a description of the planet4 ,mars is #dbcj miles in diameter2 its surface is not much more than one-quarter as extensive as that of the earth 74#bhe74 ,its mean distance from the sun is #ada1ejj1jjj miles1 #dh1ejj1jjj miles greater than that of the earth4 ,since radiant energy varies inversely as the square of distance1 ,mars receives less than half as much solar light and heat as the earth gets4 ,mars' year 7period of revolution round the sun7 is #fhg days4 ,its mean density is #ga per cent of the earth's1 and the force of gravity on its surface is #ch per cent of that on the surface of the earth2 i4e41 a body weighing one hundred pounds on the earth would1 if transported to ,mars1 weigh but thirty-eight pounds4 ,the inclination of its equator to the plane of its orbit differs very little from that of the earth's equator1 and its axial rotation occupies #bd hours #cg minutes4 so that the length of day and night1 and the extent of the seasonal changes on ,mars1 are almost precisely the same as on the earth4 ,but owing to the greater length of its year1 the seasons of ,mars1 while occurring in the same order1 are almost twice as long as ours4 ,the surface of the planet is manifestly solid1 like that of our globe1 and the telescope reveals many permanent markings on it1 recalling the appearance of a globe on which geographical features have been represented in reddish and dusky tints4 ,around the poles are plainly to be seen rounded white areas1 which vary in extent with the ,martian seasons1 nearly vanishing in summer and extending widely in winter4 ,the most recent spectroscopic determinations indicate that ,mars has an atmosphere perhaps as dense as that to be found on our loftiest mountain peaks1 and there is a perceptible amount of watery vapor in this atmosphere4 ,the surface of the planet appears to be remarkably level1 and it has no mountain ranges4 ,no evidences of volcanic action have been discovered on ,mars4 ,the dusky and reddish areas were regarded by the early observers as respectively seas and lands1 but at present it is not believed that there are any bodies of water on the planet4 ,there has never been much doubt expressed that the white areas about the poles represent snow4 ,it will be seen from this brief description that many remarkable resemblances exist between ,mars and the earth1 and there is nothing wonderful in the fact that the question of the habitability of the former has become one of extreme and wide-spread interest1 giving rise to the most diverse views1 to many extraordinary speculations1 and sometimes to regrettably heated controversy4 ,the first champion of the habitability of ,mars was ,sir ,william ,herschel1 although even before his time the idea had been suggested4 ,he was convinced by the revelations of his telescopes1 continually increasing in power1 that ,mars was more like the earth than any other planet4 ,he could not resist the testimony of the polar snows1 whose suggestive conduct was in such striking accord with what occurs upon the earth4 ,gradually1 as telescopes improved and observers increased in number1 the principal features of the planet were disclosed and charted1 and 8areography10 as the geography of ,mars was called1 took its place among the recognized branches of astronomical study4 ,but it was not before #ahgg that a fundamentally new discovery in areography gave a truly sensational turn to speculation about life on 8the red planet40 ,in that year ,mars made one of its nearest approaches to the earth1 and was so situated in its orbit that it could be observed to great advantage from the northern hemisphere of the earth4 ,the celebrated ,italian astronomer1 ,schiaparelli1 took advantage of this opportunity to make a trigonometrical survey of the surface of ,mars--as coolly and confidently as if he were not taking his sights across a thirty-five-million-mile gulf of empty space--and in the course of this survey he was astonished to perceive that the reddish areas1 then called continents1 were crossed in many directions by narrow1 dusky lines1 to which he gave the suggestive name of 8canals40 ,thus a kind of firebrand was cast into the field of astronomical speculation1 which has ever since produced disputes that have sometimes approached the violence of political faction4 ,at first the accuracy of ,schiaparelli's observations was contested2 it required a powerful telescope1 and the most excellent 8seeing10 to render the enigmatical lines visible at all1 and many searchers were unable to detect them4 ,but ,schiaparelli continued his studies in the serene sky of ,italy1 and produced charts of the gridironed face of ,mars containing so much astonishing detail that one had either to reject them in toto or to confess that ,schiaparelli was right4 ,as subsequent favorable oppositions of ,mars occurred1 other observers began to see the 8canals0 and to confirm the substantial accuracy of the ,italian astronomer's work1 and finally few were found who would venture to affirm that the 8canals0 did not exist1 whatever their meaning might be4 ,illustration3 ,schiaparelli's chart of ,mars1 showing the so-called system of canals ,when ,schiaparelli began his observations it was generally believed1 as we have said1 that the dusky areas on ,mars were seas1 and since ,schiaparelli thought that the 8canals0 invariably began and ended at the shores of the 8seas10 the appropriateness of the title given to the lines seemed apparent4 ,their artificial character was immediately assumed by many1 because they were too straight and too suggestively geometrical in their arrangement to permit the conclusion that they were natural watercourses4 ,a most surprising circumstance noted by ,schiaparelli was that the 8canals0 made their appearance after the melting of the polar snow in the corresponding hemisphere had begun1 and that they grew darker1 longer1 and more numerous in proportion as the polar liquidation proceeded2 another very puzzling observation was that many of them became double as the season advanced2 close beside an already existing 8canal10 and in perfect parallelism with it1 another would gradually make its appearance4 ,that these phenomena actually existed and were not illusions was proved by later observations1 and today they are seen whenever ,mars is favorably situated for observation4 ,in the closing decade of the nineteenth century1 ,mr ,percival ,lowell took up the work where ,schiaparelli had virtually dropped it1 and soon added a great number of 8canals0 to those previously known1 so that in his charts the surface of the wonderful little planet appears covered as with a spider's web1 the dusky lines criss-crossing in every direction1 with conspicuous knots wherever a number of them come together4 ,mr ,lowell has demonstrated that the areas originally called seas1 and thus named on the earlier charts1 are not bodies of water1 whatever else they may be4 ,he has also found that the mysterious lines do not1 as ,schiaparelli supposed1 begin and end at the edges of the dusky regions1 but often continue on across them1 reaching in some cases far up into the polar regions4 ,but ,schiaparelli was right in his observation that the appearance of the 8canals0 is synchronous with the gradual disappearance of the polar snows1 and this fact has become the basis of the most extraordinary theory that the subject of life in other worlds has ever given birth to4 ,now1 the effect of such discoveries1 as we have related1 depends upon the type of mind to whose attention they are called4 ,many are content to accept them as strange and inexplicable at present1 and to wait for further light upon them2 others insist upon an immediate inquiry concerning their probable nature and meaning4 ,such an inquiry can only be based upon inference proceeding from analogy4 ,mars1 say ,mr ,lowell and those who are of his opinion1 is manifestly a solidly incrusted planet like the earth2 it has an atmosphere1 though one of great rarity2 it has water vapor1 as the snows in themselves prove2 it has the alternation of day and night1 and a succession of seasons closely resembling those of the earth2 its surface is suggestively divided into regions of contrasting colors and appearance1 and upon that surface we see an immense number of lines geometrically arranged1 with a system of symmetrical intersections where the lines expand into circular and oval areas--and all connected with the annual melting of the polar snows in a way which irresistibly suggests the interference of intelligence directed to a definite end4 ,why1 with so many concurrent circumstances to support the hypothesis1 should we not regard ,mars as an inhabited globe8 ,but the differences between ,mars and the earth are in many ways as striking as their resemblances4 ,mars is relatively small2 it gets less than half as much light and heat as we receive2 its atmosphere is so rare that it would be distressing to us1 even if we could survive in it at all2 it has no lakes1 rivers1 or seas2 its surface is an endless prairie4 and its 8canals0 are phenomena utterly unlike anything on the earth4 ,yet it is precisely upon these divergences between the earth and ,mars1 this repudiation of terrestrial standards1 that the theory of 8life on ,mars10 for which ,mr ,lowell is mainly responsible1 is based4 ,because ,mars is smaller than the earth1 we are told it must necessarily be more advanced in planetary evolution1 the underlying cause of which is the gradual cooling and contraction of the planet's mass4 ,mars has parted with its internal heat more rapidly than the earth2 consequently its waters and its atmosphere have been mostly withdrawn by chemical combinations1 but enough of both yet remain to render life still possible on its surface4 ,as the globe of ,mars is evolutionally older than that of the earth1 so its forms of organic life may be proportionally further advanced1 and its inhabitants may have attained a degree of cultivated intelligence much superior to what at present exists upon the earth4 ,understanding the nature and the causes of the desiccation of their planet1 and possessing engineering science and capabilities far in advance of ours1 they may be conceived to have grappled with the stupendous problem of keeping their world in a habitable condition as long as possible4 ,supposing them to have become accustomed to live in their rarefied atmosphere 7a thing not inconceivable1 since men can live for a time at least in air hardly less rare71 the most pressing problem for them is that of a water-supply1 without which plant life cannot exist1 while animal life in turn depends for its existence upon vegetation4 ,the only direction in which they can seek water is that of the polar regions1 where it is alternately condensed into snow and released in the liquid form by the effect of the seasonal changes4 ,it is1 then1 to the annual melting of the polar snow-fields that the ,martian engineers are supposed to have recourse in supplying the needs of their planet1 and thus providing the means of prolonging their own existence4 ,it is imagined that they have for this purpose constructed a stupendous system of irrigation extending over the temperate and equatorial regions of the planet4 ,the 8canals0 represent the lines of irrigation1 but the narrow streaks that we see are not the canals themselves1 but the irrigated bands covered by them4 ,their dark hue1 and their gradual appearance after the polar melting has begun1 are due to the growth of vegetation stimulated by the water4 ,the rounded areas visible where several 8canals0 meet and cross are called by ,mr ,lowell 8oases40 ,these are supposed to be the principal centers of population and industry4 ,it must be confessed that some of them1 with their complicated systems of radiating lines1 appear to answer very well to such a theory4 ,no attempt to explain them by analogy with natural phenomena on the earth has proved successful4 ,but a great difficulty yet remains3 ,how to explain the seemingly miraculous powers of the supposed engineers8 ,here recourse is had once more to the relative smallness of the planet4 ,we have remarked that the force of gravity on ,mars is only thirty-eight per cent of that on the earth4 ,a steam-shovel driven by a certain horse-power would be nearly three times as effective there as here4 ,a man of our stature on ,mars would find his effective strength increased in the same proportion4 ,but just because of the slight force of gravity there1 a ,martian might attain to the traditional stature of ,goliath without finding his own weight an encumbrance to his activity1 while at the same time his huge muscles would come into unimpeded play1 enabling him single-handed to perform labors that would be impossible to a whole gang of terrestrial workmen4 ,the effective powers of huge machines would be increased in the same way2 and to all this must be added the fact that the mean density of the materials of which ,mars is composed is much less than that of the constituents of the earth4 ,combining all these considerations1 it becomes much less difficult to conceive that public works might be successfully undertaken on ,mars which would be hopelessly beyond the limits of human accomplishment4 ,certain other difficulties have also to be met2 as1 for instance1 the relative coldness of the climate of ,mars4 ,at its distance it gets considerably less than half as much light and heat as we receive4 ,in addition to this1 the rarity of its atmosphere would naturally be expected to decrease the effective temperature at the planet's surface1 since an atmosphere acts somewhat like the glass cover of a hot-house in retaining the solar heat which has penetrated it4 ,it has been calculated that1 unless there are mitigating circumstances of which we know nothing1 the average temperature at the surface of ,mars must be far below the freezing-point of water4 ,to this it is replied that the possible mitigating circumstances spoken of evidently exist in fact1 because we can see that the watery vapor condenses into snow around the poles in winter1 but melts again when summer comes4 ,the mitigating agent may be supposed to exist in the atmosphere where the presence of certain gases would completely alter the temperature gradients4 ,it might also be objected that it is inconceivable that the ,martian engineers1 however great may be their physical powers1 and however gigantic the mechanical energies under their control1 could force water in large quantities from the poles to the equator4 ,this is an achievement that measures up to the cosmical standard4 ,it is admitted by the champions of the theory that the difficulty is a formidable one2 but they call attention to the singular fact that on ,mars there can be found no chains of mountains1 and it is even doubtful if ranges of hills exist there4 ,the entire surface of the planet appears to be almost 8as smooth as a billiard ball10 and even the broad regions which were once supposed to be seas apparently lie at practically the same level as the other parts1 since the 8canals0 in many cases run uninterruptedly across them4 ,lowell's idea is that these sombre areas may be expanses of vegetation covering ground of a more or less marshy character1 for while the largest of them appear to be permanent1 there are some which vary coincidently with the variations of the canals4 ,as to the kind of machinery employed to force the water from the poles1 it has been conjectured that it may have taken the form of a gigantic system of pumps and conduits2 and since the ,martians are assumed to be so far in advance of us in their mastery of scientific principles1 the hypothesis will at least not be harmed by supposing that they have learned to harness forces of nature whose very existence in a manageable form is yet unrecognized on the earth4 ,if we wish to let the imagination loose1 we may conjecture that they have conquered the secret of those intra-atomic forces whose resistless energy is beginning to become evident to us1 but the possibility of whose utilization remains a dream1 the fulfillment of which nobody dares to predict4 ,such1 in very brief form1 is the celebrated theory of ,mars as an inhabited world4 ,it certainly captivates the imagination1 and if we believe it to represent the facts1 we cannot but watch with the deepest sympathy this gallant struggle of an intellectual race to preserve its planet from the effects of advancing age and death4 ,we may1 indeed1 wonder whether our own humanity1 confronted by such a calamity1 could be counted on to meet the emergency with equal stoutness of heart and inexhaustibleness of resource4 ,up to the present time we certainly have shown no capacity to confront ,nature toe to toe1 and to seize her by the shoulders and turn her round when she refuses to go our way4 ,if we could get into wireless telephonic communication with the ,martians we might learn from their own lips the secret of their more than 8,roman recovery40 ,,xiv ,the ,riddle of the ,asteroids ,between the orbits of ,mars and ,jupiter revolves the most remarkable system of little bodies with which we are acquainted--the ,asteroids1 or ,minor ,planets4 ,some six hundred are now known1 and they may actually number thousands4 ,they form virtually a ring about the sun4 ,the most striking general fact about them is that they occupy the place in the sky which should be occupied1 according to ,bode's ,law1 by a single large planet4 ,this fact1 as we shall see1 has led to the invention of one of the most extraordinary theories in astronomy--viz41 that of the explosion of a world6 ,bode's ,law1 so-called1 is only an empiric formula1 but until the discovery of ,neptune it accorded so well with the distances of the planets that astronomers were disposed to look upon it as really representing some underlying principle of planetary distribution4 ,they were puzzled by the absence of a planet in the space between ,mars and ,jupiter1 where the 8law0 demanded that there should be one1 and an association of astronomers was formed to search for it4 ,there was a decided sensation when1 in #ahja1 ,piazzi1 of ,palermo1 announced that he had found a little planet which apparently occupied the place in the system which belonged to the missing body4 ,he named it ,ceres1 and it was the first of the ,asteroids4 ,the next year ,olbers1 of ,bremen1 while looking for ,ceres with his telescope1 stumbled upon another small planet which he named ,pallas4 ,immediately he was inspired with the idea that these two planets were fragments of a larger one which had formerly occupied the vacant place in the planetary ranks1 and he predicted that others would be found by searching in the neighborhood of the intersection of the orbits of the two already discovered4 ,this bold prediction was brilliantly fulfilled by the finding of two more--,juno in #ahjd1 and ,vesta in #ahjg4 ,olbers would seem to have been led to the invention of his hypothesis of a planetary explosion by the faith which astronomers at that time had in ,bode's ,law4 ,they appear to have thought that several planets revolving in the gap where the 8law0 called for but one could only be accounted for upon the theory that the original one had been broken up to form the several4 ,gravitation demanded that the remnants of a planet blown to pieces1 no matter how their orbits might otherwise differ1 should all return at stated periods to the point where the explosion had occurred2 hence ,olbers' prediction that any asteroids that might subsequently be discovered would be found to have a common point of orbital intersection4 ,and curiously enough all of the first asteroids found practically answered to this requirement4 ,olbers' theory seemed to be established4 ,after the first four1 no more asteroids were found until #ahde1 when one was discovered2 then1 in #ahdg1 three more were added to the list2 and after that searchers began to pick them up with such rapidity that by the close of the century hundreds were known1 and it had become almost impossible to keep track of them4 ,the first four are by far the largest members of the group1 but their actual sizes remained unknown until less than twenty years ago4 ,it was long supposed that ,vesta was the largest1 because it shines more brightly than any of the others2 but finally1 in #ahie1 ,barnard1 with the ,lick telescope1 definitely measured their diameters1 and proved to everybody's surprise that ,ceres is really the chief1 and ,vesta only the third in rank4 ,his measures are as follows3 ,ceres1 #dgg miles2 ,pallas1 #cjd miles2 ,vesta1 #bci miles2 and ,juno1 #abj miles4 ,they differ greatly in the reflective power of their surfaces1 a fact of much significance in connection with the question of their origin4 ,vesta is1 surface for surface1 rather more than three times as brilliant as ,ceres1 whence the original mistake about its magnitude4 ,nowadays new asteroids are found frequently by photography1 but physically they are most insignificant bodies1 their average diameter probably not exceeding twenty miles1 and some are believed not to exceed ten4 ,on a planet only ten miles in diameter1 assuming the same mean density as the earth's1 which is undoubtedly too much1 the force of gravity would be so slight that an average man would not weigh more than three ounces1 and could jump off into space whenever he liked4 ,although the asteroids all revolve around the sun in the same direction as that pursued by the major planets1 their orbits are inclined at a great variety of angles to the general plane of the planetary system1 and some of them are very eccentric--almost as much so as the orbits of many of the periodic comets4 ,it has even been conjectured that the two tiny moons of ,mars and the four smaller satellites of ,jupiter may be asteroids gone astray and captured by those planets4 ,two of the asteroids are exceedingly remarkable for the shapes and positions of their orbits2 these are ,eros1 discovered in #ahih1 and ,t4 ,g41 #aijf1 found eight years later4 ,the latter has a mean distance from the sun slightly greater than that of ,jupiter1 while the mean distance of ,eros is less than that of ,mars4 ,the orbit of ,eros is so eccentric that at times it approaches within #ae1jjj1jjj miles of the earth1 nearer than any other regular member of the solar system except the moon1 thus affording an unrivaled means of measuring the solar parallax4 ,but for our present purpose the chief interest of ,eros lies in its extraordinary changes of light4 ,these changes1 although irregular1 have been observed and photographed many times1 and there seems to be no doubt of their reality4 ,their significance consists in their possible connection with the form of the little planet1 whose diameter is generally estimated at not more than twenty miles4 ,von ,oppolzer found1 in #aija1 that ,eros lost three-fourths of its brilliancy once in every two hours and thirty-eight minutes4 ,other observers have found slightly different periods of variability1 but none as long as three hours4 ,the most interesting interpretation that has been offered of this phenomenon is that it is due to a great irregularity of figure1 recalling at once ,olbers' hypothesis4 ,according to some1 ,eros may be double1 the two bodies composing it revolving around each other at very close quarters2 but a more striking1 and it may be said probable1 suggestion is that ,eros has a form not unlike that of a dumb-bell1 or hour-glass1 turning rapidly end over end so that the area of illuminated surface presented to our eyes continually changes1 reaching at certain times a minimum when the amount of light that it reflects toward the earth is reduced to a quarter of its maximum value4 ,various other bizarre shapes have been ascribed to ,eros1 such1 for instance1 as that of a flat stone revolving about one of its longer axes1 so that sometimes we see its face and sometimes its edge4 ,all of these explanations proceed upon the assumption that ,eros cannot have a simple globular figure like that of a typical planet1 a figure which is prescribed by the law of gravitation1 but that its shape is what may be called accidental2 in a word1 it is a fragment1 for it seems impossible to believe that a body formed in interplanetary space1 either through nebular condensation or through the aggregation of particles drawn together by their mutual attractions1 should not be practically spherical in shape4 ,nor is ,eros the only asteroid that gives evidence by variations of brilliancy that there is something abnormal in its constitution2 several others present the same phenomenon in varying degrees4 ,even ,vesta was regarded by ,olbers as sufficiently variable in its light to warrant the conclusion that it was an angular mass instead of a globe4 ,some of the smaller ones show very notable variations1 and all in short periods1 of three or four hours1 suggesting that in turning about one of their axes they present a surface of variable extent toward the sun and the earth4 ,the theory which some have preferred--that the variability of light is due to the differences of reflective power on different parts of the surface--would1 if accepted1 be hardly less suggestive of the origin of these little bodies by the breaking up of a larger one1 because the most natural explanation of such differences would seem to be that they arose from variations in the roughness or smoothness of the reflecting surface1 which would be characteristic of fragmentary bodies4 ,in the case of a large planet alternating expanses of land and water1 or of vegetation and desert1 would produce a notable variation in the amount of reflection1 but on bodies of the size of the asteroids neither water nor vegetation could exist1 and an atmosphere would be equally impossible4 ,one of the strongest objections to ,olbers' hypothesis is that only a few of the first asteroids discovered travel in orbits which measurably satisfy the requirement that they should all intersect at the point where the explosion occurred4 ,to this it was at first replied that the perturbations of the asteroidal orbits1 by the attractions of the major planets1 would soon displace them in such a manner that they would cease to intersect4 ,one of the first investigations undertaken by the late ,prof4 ,simon ,newcomb was directed to the solution of this question1 and he arrived at the conclusion that the planetary perturbations could not explain the actual situation of the asteroidal orbits4 ,but afterward it was pointed out that the difficulty could be avoided by supposing that not one but a series of explosions had produced the asteroids as they now are4 ,after the primary disruption the fragments themselves1 according to this suggestion1 may have exploded1 and then the resulting orbits would be as 8tangled0 as the heart could wish4 ,this has so far rehabilitated the explosion theory that it has never been entirely abandoned1 and the evidence which we have just cited of the probably abnormal shapes of ,eros and other asteroids has lately given it renewed life4 ,it is a subject that needs a thorough rediscussion4 ,we must not fail to mention1 however1 that there is a rival hypothesis which commends itself to many astronomers--viz41 that the asteroids were formed out of a relatively scant ring of matter1 situated between ,mars and ,jupiter and resembling in composition the immensely more massive rings from which1 according to ,laplace's hypothesis1 the planets were born4 ,it is held by the supporters of this theory that the attraction of the giant ,jupiter was sufficient to prevent the small1 nebulous ring that gave birth to the asteroids from condensing like the others into a single planet4 ,but if we accept the explosion theory1 with its corollary that minor explosions followed the principal one1 we have still an unanswered question before us3 ,what caused the explosions8 ,the idea of a world blowing up is too ,titanic to be shocking2 it rather amuses the imagination than seriously impresses it2 in a word1 it seems essentially chimerical4 ,we can by no appeal to experience form a mental picture of such an occurrence4 ,even the moon did not blow up when it was wrecked by volcanoes4 ,the explosive nebul and new stars are far away in space1 and suggest no connection with such a catastrophe as the bursting of a planet into hundreds of pieces4 ,we cannot conceive of a great globe thousands of miles in diameter resembling a pellet of gunpowder only awaiting the touch of a match to cause its sudden disruption4 ,somehow the thought of human agency obtrudes itself in connection with the word 8explosion10 and we smile at the idea that giant powder or nitro-glycerine could blow up a planet4 ,yet it would only need enough of them to do it4 ,after all1 we may deceive ourselves in thinking1 as we are apt to do1 that explosive energies lock themselves up only in small masses of matter4 ,there are many causes producing explosions in nature1 every volcanic eruption manifests the activity of some of them4 ,think of the giant power of confined steam2 if enough steam could be suddenly generated in the center of the earth by a downpour of all the waters of the oceans1 what might not the consequences be for our globe8 ,in a smaller globe1 and it has never been estimated that the original asteroid was even as large as the moon1 such a catastrophe would1 perhaps1 be more easily conceivable2 but since we are compelled in this case to assume that there was a series of successive explosions1 steam would hardly answer the purpose2 it would be more reasonable to suppose that the cause of the explosion was some kind of chemical reaction1 or something affecting the atoms composing the exploding body4 ,here ,dr ,gustav ,le ,bon comes to our aid with a most startling suggestion1 based on his theory of the dissipation of intra-atomic energy4 ,it will be best to quote him at some length from his book on ,the ,evolution of ,forces4 8,it does not seem at first sight10 says ,doctor ,le ,bon1 very comprehensible that worlds which appear more and more stable as they cool could become so unstable as to afterward dissociate entirely4 ,to explain this phenomenon1 we will inquire whether astronomical observations do not allow us to witness this dissociation4 ,we know that the stability of a body in motion1 such as a top or a bicycle1 ceases to be possible when its velocity of rotation descends below a certain limit4 ,once this limit is reached it loses its stability and falls to the ground4 ,prof4 ,j4 ,j4 ,thomson even interprets radio-activity in this manner1 and points out that when the speed of the elements composing the atoms descends below a certain limit they become unstable and tend to lose their equilibria4 ,there would result from this a commencement of dissociation1 with diminution of their potential energy and a corresponding increase of their kinetic energy sufficient to launch into space the products of intra-atomic disintegration4 ,it must not be forgotten that the atom being an enormous reservoir of energy is by this very fact comparable with explosive bodies4 ,these last remain inert so long as their internal equilibria are undisturbed4 ,so soon as some cause or other modifies these1 they explode and smash everything around them after being themselves broken to pieces4 ,atoms1 therefore1 which grow old in consequence of the diminution of a part of their intra-atomic energy gradually lose their stability4 ,a moment1 then1 arrives when this stability is so weak that the matter disappears by a sort of explosion more or less rapid4 ,the bodies of the radium group offer an image of this phenomenon--a rather faint image1 however1 because the atoms of this body have only reached a period of instability when the dissociation is rather slow4 ,it probably precedes another and more rapid period of dissociation capable of producing their final explosion4 ,bodies such as radium1 thorium1 etc41 represent1 no doubt1 a state of old age at which all bodies must some day arrive1 and which they already begin to manifest in our universe1 since all matter is slightly radio-active4 ,it would suffice for the dissociation to be fairly general and fairly rapid for an explosion to occur in a world where it was manifested4 ,these theoretical considerations find a solid support in the sudden appearances and disappearances of stars4 ,the explosions of a world which produce them reveal to us1 perhaps1 how the universes perish when they become old4 ,as astronomical observations show the relative frequency of these rapid destructions1 we may ask ourselves whether the end of a universe by a sudden explosion after a long period of old age does not represent its most general ending4 ,here1 perhaps1 it will be well to stop1 since1 entrancing as the subject may be1 we know very little about it1 and ,doctor ,le ,bon's theory affords a limitless field for the reader's imagination4