CHAPTER VII.TEMPORARY STARS, METEORS, AND COMETS.What, then, is the probable cause of these terrific conflagrations, as they appear to us? Take an ordinary electric induction machine,—a Holtz or a Wimshurst,—and, if the surrounding air is moist, as we operate it we will find that the results are poor, the sparks short and relatively few; but let us take the machine into another room in which the atmosphere is dry and crisp. A wondrous change will occur, and instead of a current which could scarcely flash across a few inches of space, we will now have so great an increase of energy that its tension will even cause the spark to perforate and destroy the glass walls of the heavy Leyden jars in which it is condensed. The vast realms of space, with their attenuated vapors, are the field in which the planetary electric generators operate, and into which, likewise, myriads of suns constantly pour their light and heat. We may consider this space, according to the popular view, to be uniform in constitution and density throughout all its parts,—that it is, in fact, like a vast, silent, and motionless dead sea. But this cannot possibly be true, any more than throughout the vast compass of our own atmosphere; for while some parts of space are peopled by millions of solarsystems, others, as we can plainly see, so far as telescopic vision extends, are comparatively vacant. Far more electricity is being abstracted (so to speak) in some parts of space than in others, and far more heat and light are being poured back to restore the equilibrium in some than in others. We have already seen that the temperature at the exterior surface of the terrestrial atmosphere is estimated to be more than two hundred degrees higher than in the realms of open interplanetary space; hence there must be currents,—currents of rotation like cyclones, vortical currents like whirlwinds, currents of transmission like our land- and sea-breezes and the trade-winds,—and, in fact, all space must be in a state of constant displacement and replacement, and, if visible, we should see it like a vast room filled with smoke, in which currents of every shape and direction and of all velocities would be manifest. Such currents could throw nebulæ during their condensation into rotation which could never rotate of their own motion, or gather to centers of aggregation vast whirling clouds of spatial matter, and in the spiral nebulæ we may see many such movements of rotation in apparent active progress. Of these we read in Appleton’s Cyclopædia, “They have the appearance of a maelstrom of stellar matter, and are among the most interesting objects in the heavens.” In Professor Nichol’s splendid work (“The Architecture of the Heavens,” 1850) we may see magnificent engravings of these wonderful phenomena, from the drawings by Lord Rosse,and no one can study these figures without realizing the presence of vast currents in space.In the great spiral nebula in the constellationCanes Venatici(see illustration in Chapter XII.) we perceive that the tail of the smaller nebula has been drawn into the outer convolution of the great spiral, against the radial repulsion of the latter nebula, as we can see by its curvature. This can only be due to a tremendous inflowing current in space. Were the deflection due to gravity the trend would be to the center and not to the outer convolution of the larger nebula. Professor Nichol says, “The spiral figure is characteristic of an extensive class of galaxies.” Not only in the spiral, but in other forms of nebulæ we may observe these currents of space, so that we cannot fail to perceive that they exist, and we should even conclude,a priori, that these must exist.In the elongated linear nebula in Sobieski’s Crown, illustrated above, its length is deflected into irregular curves apparently due to counter-currents of space. These gaseous nebulæ, Flammarion says, “appear like immense vaporous clouds tossed about by some rough winds, pierced with deep rents, and broken in jagged portions.” It may be said generally that every sun, as it drifts throughspace, must leave a wake of increased electric potential among the molecules which line its pathway. Beyond the limits of every vortex extend radial or tangential, polar or equatorial, streams of space, and these must extend without limit until deflected or neutralized by other conditions. Throughout all space, just as in our own atmosphere, but vastly more slowly, there must be an infinitude of movements in every direction,—movements in lines, circles, vortices, ellipses and irregular curvatures, and of all possible varieties of mass and volume.Suppose, now, a sailing vessel lighted with incandescent lamps, the electrical currents for the support of which are derived from the chemical action of sea-water on multiple pairs of suitable metallic plates arranged to extend downward as a galvanic battery into the ocean as the ship sails along, and that these plates, by the chemical action of the sea-water at ordinary, temperatures, should furnish a sufficient current to properly light the vessel. If the constancy of such current depended on the average temperature of the sea-water, at, say, sixty degrees Fahrenheit, we should find that, on suddenly crossing into the Gulf Stream, with a temperature twenty degrees higher, the energy of the battery would be rapidly increased and the lights would glow with increased brilliancy until, on emerging from the Gulf Stream at its opposite side, the original status would be gradually restored. If these distant solar systems, in their drift through space, should encounter a corresponding streamunder an increased molecular tension, more highly heated, for example, or charged with electrical potential by the surrounding solar systems, or otherwise, we should expect a similar result to ensue,—that the currents would be increased suddenly, both in quantity and intensity, and all the phenomena of “blazing” stars be revealed in the precise order in which we see them. Professor Proctor seems to have had some such idea of space vaguely in his mind when he says, in his “Familiar Essays,” “One is invited to believe that the star may have been carried by its proper motions into regions where there is a more uniform distribution of the material whence this orb recruits its fires. It may be that, in the consideration of such causes of variation affecting our sun in long-past ages, a more satisfactory explanation than any yet obtained may be found of the problem geologists found so perplexing,—the former existence of a tropical climate in places within the temperate zone, or even near the arctic regions. Sir John Herschel long since pointed to the variation of the sun as a possible cause of such changes of climate.” In confirmation of the view that such changes may be due to the passage of a solar system into or through such a “Gulf Stream” of space, we quote the following from Professor Proctor’s “Suns in Flames:” “It is noteworthy that all the stars which have blazed out suddenly, except one, have appeared in a particular region of the heavens,—the zone of the Milky Way (all, too, in one-half of that zone). The single exception is the star in the Northern Crown,and that star appeared in a region which I have found to be connected with the Milky Wayby a well-marked stream of stars; not a stream of a few stars scattered here and there, but a stream where thousands of stars are closely aggregated together, though not quite so closely as to form a visible extension of the Milky Way …. Now, the Milky Way and the outlying streams of stars connected with it seem to form a region of the stellar universe where fashioning processes are still at work.” In just such regions of potential energy should we look for such currents in space, as, on our own earth, the Gulf Stream and the trade-winds, as well as cyclones and other atmospheric movements, find their origin under precisely parallel circumstances,—to wit, the outpour upon and direct precipitation of increased quantities of heat at the tropics or other local centers of such development. The effects of such an increase of quantity and potential in an electrical current are clearly illustrated in the device previously referred to, in which electrolytic decomposition was effected in a pail of water; we find it also in the burning out of the brushes and commutators in dynamo-electric machines and in telegraphic apparatus during thunder-storms and the like. Allowing a solar system a drift through space only equal to that of our own, which has a relatively slow movement, it would traverse such a “Gulf Stream” of space seven hundred thousand miles wide in a single day. But it may not even have passed through; it may merely have grazed the margin of such a current; for the motions ofsolar systems are not controlled by the same forces as those upon which their electrical energies depend.Professor Ball, in his chapter on the great heat-wave of 1892, says, “Towards the end of July an extraordinarily high temperature, even for that period of the year, prevailed over a very large part of the North American continent. The so-called heat-wave then seems to have travelled eastward and crossed the Atlantic Ocean; … a fortnight after the occurrence of unusually great heat in the New World there was a similar experience in the Old World …. This discussion will at all events enable us to make some reply to the question which has often been asked, as to what was the cause of the great heat-wave …. It is, however, quite possible that certain changes in progress on the sun may act in a specific manner on our climate …. It cannot be denied that local, if not general, changes in the sun’s temperature must be the accompaniment of the violent disturbances by which our luminary is now and then agitated. It is, indeed, well known that there are occasional outbreaks of solar activity, and that these recur in a periodic manner; it is accordingly not without interest to notice that the present year has been one of the periods of this activity. We are certainly not going so far as to say that any connection has been definitely established between a season of exuberant sun-spots and a season remarkable for excessive warmth; but, as we know that there is a connection between the magnetic condition of theearth and the state of solar activity, it is by no means impossible that climate and sun-spots may also stand in some relationship to each other.” These local deviations are doubtless due to planetary positions with reference to the sun, but more general variations must depend upon the constitution of such parts of space as the solar system may occupy; but even then they will be but temporary, since the sun’s volume will rapidly expand or contract so as finally to restore the normal emission of solar heat, as will be further explained later on in this work.Phenomena of a new or temporary star, a “star in flames.”—1, normal state of star, photosphere more highly heated than chromosphere: 2, stage of highest incandescence, chromosphere expanded and more highly heated than photosphere, bright line spectrum: 3, stage of recession, chromosphere diminishing in incandescence, heat acting upon solar core, numerous spots, volatilization of metallic surface, spectrum of dark absorption bands; 4, return to normal state again.There are other causes also, readily conceivable, for such increased electrical action; for instance, in that thickly-peopled region of space, two solar systems adjacent might easily have their exterior planets so related to each other as suddenly, at their points of nearest approach, to cause one or more to direct an abnormally large electrical current into the sun of the adjacent system; this would correspond in electric energy, in fact, to a violent “perturbation” in its orbit by the action of gravity produced by a neighboring planet or system. No reversal of polarity could take place between these planets under these circumstances, any more than between the earth and the moon. In some portions of the Milky Way, doubtless, suns blaze by dozens across the sky at night, and by day as well, to which, in our more solitary skies, we are strangers. Revolving in perfect harmony, perturbations must nevertheless be frequent, and to what limits they may there be confined we shallnever know until we realize the extent of these galaxies and the relative contiguity of their solar systems to each other. It is enough to show how such variations may occur; in what particular way they do occur does not affect the question of their origin. Even if such increased energy were to continue by permanently increased planetary action, it is not necessary to suppose that a corresponding permanent increase of light and heat would result on the part of the sun, for its density is such (only one-fourth that of the earth) that, under the tremendous force of its gravity (twenty-seven and one-tenth times that of the earth), its constituents cannot be maintained in solid form, but must be, as before stated, either liquid or gaseous, and perhaps in part both. Now, as it has been computed that the sun, by contraction to its present density, would have evolved its present light and heat for a period of millions of years, it is obvious that any increase in its present volume, without increase of mass, would produce precisely opposite and compensated results, so that the sun could receive from outside sources as much heat as would expand its present volume to that at the initial point of such assumed condensation without increased emission of light and heat. The sun is thus, in effect, a self-compensating machine, and its passage through a region of increased electrical generation would first manifest itself in a vast increase of brilliancy, due to higher incandescence of its hydrogen envelope; this, in turn, would be communicated to the deeper structures of the sun, producing increased volatilizationand dark absorption bands, and finally to the whole solar mass, expanding its volume in proportion to the heat absorbed. Hence we should see precisely the phenomena that we do see in flaming stars or so-called new stars. We find such compensations all through nature, and it is simply inaccordance with her universal laws that they occur. It is a singular circumstance that the catastrophe which is foretold in the biblical record as the termination of all human life on earth, for the present cycle, at least, should be almost literally in accordance with the phenomena characteristic of such an increase of solar energy, and one produced in some such manner. If the temperature of the solar atmosphere were rapidly raised by increased planetary action to a point which would reverse the lines of hydrogen from dark to bright, say to a brightness eight hundred times that of the normal, as in the case of the temporary star cited, though the heat would not, of course, be increased in any such proportion, yet the heavens would be indeed rolled up as a scroll, and all life would be extinguished in a very brief period. But the planets would continue to roll along their orbits, the integrity of the earth’s mass would still be intact, and after a few days or weeks the sun would begin to decline in brightness, the volatilized vapors would slowly recede within the solar atmosphere, and the temperature would gradually fall again to its normal, leaving, however, a lifeless world to roll on its way henceforth, but as bright and cheerful in all its possibilities, when the former conditions had gradually become restored, as before. Perhaps some distant astronomer in the neighborhood of Sirius—if we shall have travelled so far away by that time—might send a note to the morning papers to announce that the temporary star near Alpha Centauri had again receded to the tenthmagnitude. In due time—perhaps a thousand years—all would be ready for a new development of life, and the cycle would continue as before. Perchance, too, in some deep abyss, or buried far beneath the surface, some germs of life might still continue to exist; and from these, like the seeds resurrected from buried mummies, a new life might again begin, guided along once more through vast ages in a progressive ascent from development to development until, in some new and strange forms, the higher types of life might again appear. To these there would indeed be revealed a new heaven and a new earth. Who knows how many such cycles of life may have come and gone on earth, in which, like the dwellers of Jerusalem, new peoples have built new cities, one above another, upon the unknown graves of the past? In the words of Tennyson,—“A wondrous eft was of old the Lord and Master of earth,For him did his high sun flame, and his river billowing ran,And he felt himself in his force to be Nature’s crowning race.As nine months go to the shaping an infant ripe for his birth,So many a million of ages have gone to the making man:He now is first, but is he the last?”Whatever the coming, the progress, or the going of life on earth, the course of our solar system will go on the same, the processes of creation unchanged and her mechanism unimpaired. It is obvious that no such conditions could prevail in the return to unorganizable chaos which must be the consequence of any possible planetary collisions in space. No conceivable process of creation couldreturn a system disrupted into meteorites to an operative solar system again. Even the nebular hypothesis contemplates nothing of that sort as, by the wildest conjecture, ever possible. But with us the danger is far distant. Professor Proctor says, in his article “Suns in Flames,” “As Sir William Herschel long since pointed out, we can recognize in various parts of the heavens various stages of development, and chief among the regions where as yet nature’s work seems incomplete is the Galactic zone,—especially that half of it where the Milky Way consists of irregular streams and clouds of stellar light. As there is no reason for believing that our sun belongs to this part of the galaxy, but, on the contrary, good ground for considering that he belongs to the class of insulated stars, few of which have shown signs of irregular variation, while none have ever blazed suddenly out with many hundred times their former lustre, we may fairly infer a very high degree of probability in favor of the belief that, for many ages still to come, the sun will continue steadily to discharge his duties as fire, light, and life of the solar system.” The passage of our system through gradually changing regions of space, as contrasted with streams or vortices, could not affect our sun’s light even temporarily, as the contraction and expansion of its volume would fully compensate for any such gradual or partial variation, and, by position, he is far from likely to pass into any of those whirlpools or torrents of space which seem to mark at irregular intervals the region of the irregularly variable stars.Allied in appearance to such stars which suddenly flame out in space, but totally different in reality, are comets. These strangers to our own system have excited the wonder and astonishment of mankind from the earliest ages. They seem to defy all rules and all explanation; but, when properly examined, they will fall inevitably into the general scheme of the source and mode of solar energy which we have endeavored to present. These bodies enter our solar system from without. Appleton’s Cyclopædia says, “Schiaparelli, to whom the discovery is in part due, considers the meteors to be dispersed portions of the comet’s original substance,—that is, of the substance with whichthe comet entered the solar domain.” Professor Proctor, “Meteoric Astronomy,” says, “A word or two may be permitted on the question of the condition ofcomets freshly arriving on the scene of the solar system. It is assumed sometimes that the train of meteors already exists when the cometfirst comes within the solar domain.” In the “Romance of Astronomy” (R. Kalley Miller, M.A.) it is said, “In a sort of debatable territory between our own solar system and the infinite stellar universe around we come upon these erratic and anomalous bodies—the comets; some of which have accidentally become permanent attendants upon our sun; others have only paid it a single casual visit in the course of their wanderings through space, and are not likely again to come within the range of its attracting influence; while countless millions are doubtless scattered throughout the realms of theinfinite, whose existence will never be revealed to human ken at all.” Professor Helmholtz, in fact (see addendum to his lecture on the origin of the planetary system), advanced the idea in a speculative way, that our terrestrial life might have had its origin in one of these meteoric bodies by the “transmission of organisms through space.” In Professor Proctor’s article on comets (“Mysteries of Time and Space”) he says, “The paths followed by comets show no resemblance either to the planetary orbits or to each other. Here we see a comet travelling in a path of moderate extent and not very eccentric; then another which rushes from a distance of two or three thousand millions of miles, approaches the sun with ever-increasing velocity until nearer to him than parts of his own corona (as seen in eclipses), sweeps around him with inconceivable rapidity, and makes off again to where the aphelion of its orbit lies far out in space beyond the most distant known planet,—Neptune. Some comets travel in a direct, some in a retrograde path; a few near the plane of the earth’s orbit, many in planes showing every variety of inclination. Some comets regularly return after intervals of a few years; some after hundreds of years; others are only seen once or twice, and then unaccountably vanish; and not a few show by the paths they follow that they have come from interstellar space to pay our system but a single visit, passing out again to traverse we know not what other systems or regions …. When we have said that these objects obey the law of gravity, we havementioned the only circumstance—as it would appear—in which they conform to the relations observed in terrestrial and planetary arrangements. And even this law—the widest yet revealed to man—they seem to obey half unwillingly. We see the head of a comet tracing out systematically enough its proper orbit, while the comet’s tail is all unruly and disobedient …. The fact, then, is demonstrated that two of the meteor streams encountered by the earth are so far associated with two comets as to travel on the same orbits. We may not unsafely infer that all the meteor systems are in like manner associated with other comets. Nor is it very rash to assume that all comets are in like manner associated with meteor systems.”Concerning the influence of gravitation of the planets, the same author says (“Meteoric Astronomy”), “Now, the circumstances under which a comet approaching the sun on a parabolic or hyperbolic orbit can be thus affected must be regarded as exceptional. The planet’s influence must, in the first place, be very energetically exercised; in other words, the arriving comet must pass very close to the planet, for under any other circumstances the sun’s influence so enormously outvies the planet’s that the figure of the cometic orbit would be very little affected. Moreover, the planet’s attraction must produce an important balance of retardation. The planet will inevitably accelerate the comet up to a certain point, and afterwards will retard it; the latter influence must greatly exceed the former. To show how greatly the comet must be retarded,it is only necessary to mention that the actual velocity of the November meteors when they cross the orbit of Uranus is less than one-third of the velocity with which Uranus himself travels, but their velocity at the same distance from the sun, when they were approaching him from some distant stellar domain, exceeded the velocity of Uranus in his orbit in the proportion of about seven to five …. It follows, not merely as a probable inference, but, I think, as a demonstrated conclusion, that if the November meteors came originally into our system as a comet travelling sunward from infinity, then either that comet was very compact or else Uranus captured only a small portion of the comet, the remaining portions moving thenceforth on orbits wholly different from the path of the November meteors …. No other planet than Uranus can have brought about the subjection of this comet to solar rule.” In his article on comets he says, “It may be well here to consider a case in which some active force (other than gravity) exerted by the sun seems to have brought the destruction of a comet, or at least to have broken up the comet into unrecognizable fragments.” He refers to Biela’s comet, with an orbital period of six and two-thirds years, and a path which was found to approach very near to the path of the earth. In 1832 the comet crossed the earth’s track several weeks before the arrival of the earth at the same point without appreciable interference. On its second return, in 1845–46, it was found to be divided into two comets travelling side by side; in1852 they reappeared, still divided, and gradually diverging from each other. Since then they have never reappeared, though diligently sought for at every period. Professor Proctor adds, “It has been seen again, though not as a comet; nay, the occasion on which it was seen in the way referred to was predicted, and the prediction fulfilled, even in details. For a full account of its reappearance—as a meteor stream—I refer the reader to my essay on Biela’s comet in ‘Familiar Science Studies.’ ”In Miller’s “Romance of Astronomy” we read, “Encke’s comet, which possesses the smallest orbit of any connected with our system, is sensibly drawing nearer and nearer to the sun at every revolution.” In Professor Proctor’s “Cometic Mysteries,” the author says, “We hear it stated that the nucleus of a comet is made up of meteoric stones (Professor P. G. Tait says—for unknown reasons—that they resemble ‘paving stones or even bricks’) as confidently as though the earth had at some time passed through the nucleus of a comet, and some of our streets were now paved with stones which had fallen to the earth on such an occasion. As a matter of fact, all that has yet been proved is that meteoric bodies follow in the track (which is very different from the tail) of some known comets, and that probably all comets are followed by trains of meteors. These may have come out of the head or nucleus in some way as yet unexplained; but it is by no means certain that they have done so, and it is by many astronomers regarded as more than doubtful. The most important point to be noticedin the behavior of large comets as they approach the sun is, that usually the side of the coma which lies towards the sun is the scene of intense disturbance. Streams of luminous matter seem to rise continually towards the sun, attaining a certain distance from the head, when, assuming a cloud-like appearance, they seem to form an envelope around the nucleus. This envelope gradually increases its distance from the sun, growing fainter and larger, while within it the process is repeated and a new envelope is formed. This, in turn, ascends from the nucleus, expanding as it does so, while within it a new envelope is formed. Meanwhile the first one formed has grown fainter, perhaps has disappeared. But sometimes the process goes on so rapidly (a day or two sufficing for the formation of a complete new envelope) that several envelopes will be seen at the same time,—the outermost faintest, the innermost most irregular in shape and most varied in brightness, while the envelope or envelopes between are the best developed and most regular. The matter raised up in these envelopes seems to have undergone a certain change of character, causing it no longer to obey the sun’s attractive influence, but to experience a strong repulsive action from him, whereby it is apparently swept away with great rapidity to form the tail. ‘It flows past the nucleus,’ says Dr. Huggins, ‘on all sides, still ever expanding and shooting backward until a tail is formed in the direction opposite to the sun. This tail is usually curved, though sometimes rays or extra tails sensibly straight are also seen.’ ”In “The Sun as a Perpetual Machine,” Professor Proctor says, “Take, again, the phenomena of comets, which still remain among the greatest of nature’s mysteries. We have reason to believe … that the nucleus of a comet consists of an aggregation of stones similar to meteorites. Adopting this view, and assuming that these stones have absorbed somewhere gases to the amount of six times their volume (taken at atmospheric pressure), we may ask, What will be the effect of such a mass of stones advancing towards the sun at a velocity reaching in perihelion the prodigious rate of three hundred and sixty-six miles per second (as observed in the comet of 1843), being twenty-three times our orbital rate of motion?” Professor Ball says, “One of the most important results of the great shower of 1866 was the demonstration that the swarm of little bodies to which that shower owed its origin was connected with a comet. The swarm was found, in fact, to follow the exact track which the comet pursued around the sun …. Of this connection between the cometary orbits and revolving swarms of meteors many other instances could be cited. I may refer to the remarkable lists published by the British Association, in which, beside the name of the comet or the designation which astronomers had affixed to it, the meteoric swarm with which the comet is associated is also given …. On these grounds it appears to be perfectly certain that the origin of the shooting stars which appear in swarms cannot be disassociated from the origin of the comets by which thoseswarms are accompanied.” The author makes a distinction between such ordinary shooting stars and meteorites, and attributes the appearance of the latter on earth to masses thrown forth from some volcanosomewhere, but this has nothing to do with the special phenomena to be interpreted. It may be said, however, that the presence of olefiant gas as one of the occluded gases in a meteorite (four and fifty-five-hundredths per cent., as stated by Professor Proctor, in his article “The Sun as a Perpetual Machine”), and the remarkable fact, stated in the article “Spectrum Analysis” in Appleton’s Cyclopædia, that, in Winnecke’s comet of 1868, “the bands agree in position with those obtained as the spectrum of carbon, by passing the electric spark through olefiant gas, “would lead one to consider a cometic origin, for this particular meteorite at least, to be highly probable. Professor Ball further says, “There have been several instances in which a comet has approached so close to a planet that the attraction between the two bodies must have had significant influence on the planet, if the cometary mass had been at all comparable with that of the more robust body. The most celebrated instance is presented in the case of Lexell’s comet, which happened to cross the track of Jupiter. The effect upon this body was so overwhelming that it was wrenched from its original path and started afresh along a wholly different track.” The same writer, speaking of the tails of comets, says, “I have no intention to discuss here the vexed question of the tails of comets. I donot now inquire whether the repulsion by which the tail is produced be due to the intense radiation from the sun, or to electricity, or to some other agent. It is sufficient for our present purpose to note that, even if the tails of comets do gravitate towards the sun, the attraction is obscured by a more powerful repulsive force …. Nor do the directions in which the comets move exhibit any conformity; some move round the sun in one direction, some move in the opposite direction. Even the planes which contain the orbits of the comets are totally different from each other. Instead of being inclined at only a very few degrees to their mean position, the planes of the comets hardly follow any common law; they are inclined at all sorts of directions. In no respect do the comets obey those principles which are necessary to prevent constitutional disorder in the planetary system …. Now, all we have hitherto seen with regard to comets tends to show that the masses of comets are extremely small. Attempts have been made to measure them, but have always failed, because the scales in which we have attempted to weigh them have been too coarse to weigh anything of the almost spiritual texture of a comet. It is unnecessary to go as far as some have done, and to say that the weight of a large comet may be only a few pounds or a few ounces. It might be more reasonable to suppose that the weight of a large comet was thousands of tons, though even thousands of tons would be far too small a weight to admit of being measured by the very coarsebalance which is at our disposal.” In the chapter “Visitors from the Sky,” the same author says, “As such a comet in its progress across the heavens passes between us and the stars, those stars are often seen twinkling brilliantly right through the many thousand miles of cometary matter which their rays have to traverse. The lightest haze in our atmosphere would suffice to extinguish the faint gleam of these small stars; indeed, a few feet of mist would have more power of obstructing the stellar light than cometary material scores of thousands of miles thick. It is true that the central portions of many of these comets often exhibit much greater density than is found in the exterior regions; still, in the great majority of such objects there is no opacity, even in the densest part, sufficient to put out a star. In the case of the more splendid bodies of this description, it may be supposed that the matter is somewhat more densely aggregated as well as more voluminous; still, however, it will be remembered that the great comet of 1858 passed over Arcturus, and that the star was seen shining brilliantly, notwithstanding the interposition of a cometary curtain millions of miles in thickness. So far as I know, no case is known in which the nucleus of a really bright and great comet has been witnessed in the act of passage over a considerable star. It would indeed be extremely interesting to ascertain whether in such case the star experienced any considerable diminution in its lustre.”
CHAPTER VII.TEMPORARY STARS, METEORS, AND COMETS.What, then, is the probable cause of these terrific conflagrations, as they appear to us? Take an ordinary electric induction machine,—a Holtz or a Wimshurst,—and, if the surrounding air is moist, as we operate it we will find that the results are poor, the sparks short and relatively few; but let us take the machine into another room in which the atmosphere is dry and crisp. A wondrous change will occur, and instead of a current which could scarcely flash across a few inches of space, we will now have so great an increase of energy that its tension will even cause the spark to perforate and destroy the glass walls of the heavy Leyden jars in which it is condensed. The vast realms of space, with their attenuated vapors, are the field in which the planetary electric generators operate, and into which, likewise, myriads of suns constantly pour their light and heat. We may consider this space, according to the popular view, to be uniform in constitution and density throughout all its parts,—that it is, in fact, like a vast, silent, and motionless dead sea. But this cannot possibly be true, any more than throughout the vast compass of our own atmosphere; for while some parts of space are peopled by millions of solarsystems, others, as we can plainly see, so far as telescopic vision extends, are comparatively vacant. Far more electricity is being abstracted (so to speak) in some parts of space than in others, and far more heat and light are being poured back to restore the equilibrium in some than in others. We have already seen that the temperature at the exterior surface of the terrestrial atmosphere is estimated to be more than two hundred degrees higher than in the realms of open interplanetary space; hence there must be currents,—currents of rotation like cyclones, vortical currents like whirlwinds, currents of transmission like our land- and sea-breezes and the trade-winds,—and, in fact, all space must be in a state of constant displacement and replacement, and, if visible, we should see it like a vast room filled with smoke, in which currents of every shape and direction and of all velocities would be manifest. Such currents could throw nebulæ during their condensation into rotation which could never rotate of their own motion, or gather to centers of aggregation vast whirling clouds of spatial matter, and in the spiral nebulæ we may see many such movements of rotation in apparent active progress. Of these we read in Appleton’s Cyclopædia, “They have the appearance of a maelstrom of stellar matter, and are among the most interesting objects in the heavens.” In Professor Nichol’s splendid work (“The Architecture of the Heavens,” 1850) we may see magnificent engravings of these wonderful phenomena, from the drawings by Lord Rosse,and no one can study these figures without realizing the presence of vast currents in space.In the great spiral nebula in the constellationCanes Venatici(see illustration in Chapter XII.) we perceive that the tail of the smaller nebula has been drawn into the outer convolution of the great spiral, against the radial repulsion of the latter nebula, as we can see by its curvature. This can only be due to a tremendous inflowing current in space. Were the deflection due to gravity the trend would be to the center and not to the outer convolution of the larger nebula. Professor Nichol says, “The spiral figure is characteristic of an extensive class of galaxies.” Not only in the spiral, but in other forms of nebulæ we may observe these currents of space, so that we cannot fail to perceive that they exist, and we should even conclude,a priori, that these must exist.In the elongated linear nebula in Sobieski’s Crown, illustrated above, its length is deflected into irregular curves apparently due to counter-currents of space. These gaseous nebulæ, Flammarion says, “appear like immense vaporous clouds tossed about by some rough winds, pierced with deep rents, and broken in jagged portions.” It may be said generally that every sun, as it drifts throughspace, must leave a wake of increased electric potential among the molecules which line its pathway. Beyond the limits of every vortex extend radial or tangential, polar or equatorial, streams of space, and these must extend without limit until deflected or neutralized by other conditions. Throughout all space, just as in our own atmosphere, but vastly more slowly, there must be an infinitude of movements in every direction,—movements in lines, circles, vortices, ellipses and irregular curvatures, and of all possible varieties of mass and volume.Suppose, now, a sailing vessel lighted with incandescent lamps, the electrical currents for the support of which are derived from the chemical action of sea-water on multiple pairs of suitable metallic plates arranged to extend downward as a galvanic battery into the ocean as the ship sails along, and that these plates, by the chemical action of the sea-water at ordinary, temperatures, should furnish a sufficient current to properly light the vessel. If the constancy of such current depended on the average temperature of the sea-water, at, say, sixty degrees Fahrenheit, we should find that, on suddenly crossing into the Gulf Stream, with a temperature twenty degrees higher, the energy of the battery would be rapidly increased and the lights would glow with increased brilliancy until, on emerging from the Gulf Stream at its opposite side, the original status would be gradually restored. If these distant solar systems, in their drift through space, should encounter a corresponding streamunder an increased molecular tension, more highly heated, for example, or charged with electrical potential by the surrounding solar systems, or otherwise, we should expect a similar result to ensue,—that the currents would be increased suddenly, both in quantity and intensity, and all the phenomena of “blazing” stars be revealed in the precise order in which we see them. Professor Proctor seems to have had some such idea of space vaguely in his mind when he says, in his “Familiar Essays,” “One is invited to believe that the star may have been carried by its proper motions into regions where there is a more uniform distribution of the material whence this orb recruits its fires. It may be that, in the consideration of such causes of variation affecting our sun in long-past ages, a more satisfactory explanation than any yet obtained may be found of the problem geologists found so perplexing,—the former existence of a tropical climate in places within the temperate zone, or even near the arctic regions. Sir John Herschel long since pointed to the variation of the sun as a possible cause of such changes of climate.” In confirmation of the view that such changes may be due to the passage of a solar system into or through such a “Gulf Stream” of space, we quote the following from Professor Proctor’s “Suns in Flames:” “It is noteworthy that all the stars which have blazed out suddenly, except one, have appeared in a particular region of the heavens,—the zone of the Milky Way (all, too, in one-half of that zone). The single exception is the star in the Northern Crown,and that star appeared in a region which I have found to be connected with the Milky Wayby a well-marked stream of stars; not a stream of a few stars scattered here and there, but a stream where thousands of stars are closely aggregated together, though not quite so closely as to form a visible extension of the Milky Way …. Now, the Milky Way and the outlying streams of stars connected with it seem to form a region of the stellar universe where fashioning processes are still at work.” In just such regions of potential energy should we look for such currents in space, as, on our own earth, the Gulf Stream and the trade-winds, as well as cyclones and other atmospheric movements, find their origin under precisely parallel circumstances,—to wit, the outpour upon and direct precipitation of increased quantities of heat at the tropics or other local centers of such development. The effects of such an increase of quantity and potential in an electrical current are clearly illustrated in the device previously referred to, in which electrolytic decomposition was effected in a pail of water; we find it also in the burning out of the brushes and commutators in dynamo-electric machines and in telegraphic apparatus during thunder-storms and the like. Allowing a solar system a drift through space only equal to that of our own, which has a relatively slow movement, it would traverse such a “Gulf Stream” of space seven hundred thousand miles wide in a single day. But it may not even have passed through; it may merely have grazed the margin of such a current; for the motions ofsolar systems are not controlled by the same forces as those upon which their electrical energies depend.Professor Ball, in his chapter on the great heat-wave of 1892, says, “Towards the end of July an extraordinarily high temperature, even for that period of the year, prevailed over a very large part of the North American continent. The so-called heat-wave then seems to have travelled eastward and crossed the Atlantic Ocean; … a fortnight after the occurrence of unusually great heat in the New World there was a similar experience in the Old World …. This discussion will at all events enable us to make some reply to the question which has often been asked, as to what was the cause of the great heat-wave …. It is, however, quite possible that certain changes in progress on the sun may act in a specific manner on our climate …. It cannot be denied that local, if not general, changes in the sun’s temperature must be the accompaniment of the violent disturbances by which our luminary is now and then agitated. It is, indeed, well known that there are occasional outbreaks of solar activity, and that these recur in a periodic manner; it is accordingly not without interest to notice that the present year has been one of the periods of this activity. We are certainly not going so far as to say that any connection has been definitely established between a season of exuberant sun-spots and a season remarkable for excessive warmth; but, as we know that there is a connection between the magnetic condition of theearth and the state of solar activity, it is by no means impossible that climate and sun-spots may also stand in some relationship to each other.” These local deviations are doubtless due to planetary positions with reference to the sun, but more general variations must depend upon the constitution of such parts of space as the solar system may occupy; but even then they will be but temporary, since the sun’s volume will rapidly expand or contract so as finally to restore the normal emission of solar heat, as will be further explained later on in this work.Phenomena of a new or temporary star, a “star in flames.”—1, normal state of star, photosphere more highly heated than chromosphere: 2, stage of highest incandescence, chromosphere expanded and more highly heated than photosphere, bright line spectrum: 3, stage of recession, chromosphere diminishing in incandescence, heat acting upon solar core, numerous spots, volatilization of metallic surface, spectrum of dark absorption bands; 4, return to normal state again.There are other causes also, readily conceivable, for such increased electrical action; for instance, in that thickly-peopled region of space, two solar systems adjacent might easily have their exterior planets so related to each other as suddenly, at their points of nearest approach, to cause one or more to direct an abnormally large electrical current into the sun of the adjacent system; this would correspond in electric energy, in fact, to a violent “perturbation” in its orbit by the action of gravity produced by a neighboring planet or system. No reversal of polarity could take place between these planets under these circumstances, any more than between the earth and the moon. In some portions of the Milky Way, doubtless, suns blaze by dozens across the sky at night, and by day as well, to which, in our more solitary skies, we are strangers. Revolving in perfect harmony, perturbations must nevertheless be frequent, and to what limits they may there be confined we shallnever know until we realize the extent of these galaxies and the relative contiguity of their solar systems to each other. It is enough to show how such variations may occur; in what particular way they do occur does not affect the question of their origin. Even if such increased energy were to continue by permanently increased planetary action, it is not necessary to suppose that a corresponding permanent increase of light and heat would result on the part of the sun, for its density is such (only one-fourth that of the earth) that, under the tremendous force of its gravity (twenty-seven and one-tenth times that of the earth), its constituents cannot be maintained in solid form, but must be, as before stated, either liquid or gaseous, and perhaps in part both. Now, as it has been computed that the sun, by contraction to its present density, would have evolved its present light and heat for a period of millions of years, it is obvious that any increase in its present volume, without increase of mass, would produce precisely opposite and compensated results, so that the sun could receive from outside sources as much heat as would expand its present volume to that at the initial point of such assumed condensation without increased emission of light and heat. The sun is thus, in effect, a self-compensating machine, and its passage through a region of increased electrical generation would first manifest itself in a vast increase of brilliancy, due to higher incandescence of its hydrogen envelope; this, in turn, would be communicated to the deeper structures of the sun, producing increased volatilizationand dark absorption bands, and finally to the whole solar mass, expanding its volume in proportion to the heat absorbed. Hence we should see precisely the phenomena that we do see in flaming stars or so-called new stars. We find such compensations all through nature, and it is simply inaccordance with her universal laws that they occur. It is a singular circumstance that the catastrophe which is foretold in the biblical record as the termination of all human life on earth, for the present cycle, at least, should be almost literally in accordance with the phenomena characteristic of such an increase of solar energy, and one produced in some such manner. If the temperature of the solar atmosphere were rapidly raised by increased planetary action to a point which would reverse the lines of hydrogen from dark to bright, say to a brightness eight hundred times that of the normal, as in the case of the temporary star cited, though the heat would not, of course, be increased in any such proportion, yet the heavens would be indeed rolled up as a scroll, and all life would be extinguished in a very brief period. But the planets would continue to roll along their orbits, the integrity of the earth’s mass would still be intact, and after a few days or weeks the sun would begin to decline in brightness, the volatilized vapors would slowly recede within the solar atmosphere, and the temperature would gradually fall again to its normal, leaving, however, a lifeless world to roll on its way henceforth, but as bright and cheerful in all its possibilities, when the former conditions had gradually become restored, as before. Perhaps some distant astronomer in the neighborhood of Sirius—if we shall have travelled so far away by that time—might send a note to the morning papers to announce that the temporary star near Alpha Centauri had again receded to the tenthmagnitude. In due time—perhaps a thousand years—all would be ready for a new development of life, and the cycle would continue as before. Perchance, too, in some deep abyss, or buried far beneath the surface, some germs of life might still continue to exist; and from these, like the seeds resurrected from buried mummies, a new life might again begin, guided along once more through vast ages in a progressive ascent from development to development until, in some new and strange forms, the higher types of life might again appear. To these there would indeed be revealed a new heaven and a new earth. Who knows how many such cycles of life may have come and gone on earth, in which, like the dwellers of Jerusalem, new peoples have built new cities, one above another, upon the unknown graves of the past? In the words of Tennyson,—“A wondrous eft was of old the Lord and Master of earth,For him did his high sun flame, and his river billowing ran,And he felt himself in his force to be Nature’s crowning race.As nine months go to the shaping an infant ripe for his birth,So many a million of ages have gone to the making man:He now is first, but is he the last?”Whatever the coming, the progress, or the going of life on earth, the course of our solar system will go on the same, the processes of creation unchanged and her mechanism unimpaired. It is obvious that no such conditions could prevail in the return to unorganizable chaos which must be the consequence of any possible planetary collisions in space. No conceivable process of creation couldreturn a system disrupted into meteorites to an operative solar system again. Even the nebular hypothesis contemplates nothing of that sort as, by the wildest conjecture, ever possible. But with us the danger is far distant. Professor Proctor says, in his article “Suns in Flames,” “As Sir William Herschel long since pointed out, we can recognize in various parts of the heavens various stages of development, and chief among the regions where as yet nature’s work seems incomplete is the Galactic zone,—especially that half of it where the Milky Way consists of irregular streams and clouds of stellar light. As there is no reason for believing that our sun belongs to this part of the galaxy, but, on the contrary, good ground for considering that he belongs to the class of insulated stars, few of which have shown signs of irregular variation, while none have ever blazed suddenly out with many hundred times their former lustre, we may fairly infer a very high degree of probability in favor of the belief that, for many ages still to come, the sun will continue steadily to discharge his duties as fire, light, and life of the solar system.” The passage of our system through gradually changing regions of space, as contrasted with streams or vortices, could not affect our sun’s light even temporarily, as the contraction and expansion of its volume would fully compensate for any such gradual or partial variation, and, by position, he is far from likely to pass into any of those whirlpools or torrents of space which seem to mark at irregular intervals the region of the irregularly variable stars.Allied in appearance to such stars which suddenly flame out in space, but totally different in reality, are comets. These strangers to our own system have excited the wonder and astonishment of mankind from the earliest ages. They seem to defy all rules and all explanation; but, when properly examined, they will fall inevitably into the general scheme of the source and mode of solar energy which we have endeavored to present. These bodies enter our solar system from without. Appleton’s Cyclopædia says, “Schiaparelli, to whom the discovery is in part due, considers the meteors to be dispersed portions of the comet’s original substance,—that is, of the substance with whichthe comet entered the solar domain.” Professor Proctor, “Meteoric Astronomy,” says, “A word or two may be permitted on the question of the condition ofcomets freshly arriving on the scene of the solar system. It is assumed sometimes that the train of meteors already exists when the cometfirst comes within the solar domain.” In the “Romance of Astronomy” (R. Kalley Miller, M.A.) it is said, “In a sort of debatable territory between our own solar system and the infinite stellar universe around we come upon these erratic and anomalous bodies—the comets; some of which have accidentally become permanent attendants upon our sun; others have only paid it a single casual visit in the course of their wanderings through space, and are not likely again to come within the range of its attracting influence; while countless millions are doubtless scattered throughout the realms of theinfinite, whose existence will never be revealed to human ken at all.” Professor Helmholtz, in fact (see addendum to his lecture on the origin of the planetary system), advanced the idea in a speculative way, that our terrestrial life might have had its origin in one of these meteoric bodies by the “transmission of organisms through space.” In Professor Proctor’s article on comets (“Mysteries of Time and Space”) he says, “The paths followed by comets show no resemblance either to the planetary orbits or to each other. Here we see a comet travelling in a path of moderate extent and not very eccentric; then another which rushes from a distance of two or three thousand millions of miles, approaches the sun with ever-increasing velocity until nearer to him than parts of his own corona (as seen in eclipses), sweeps around him with inconceivable rapidity, and makes off again to where the aphelion of its orbit lies far out in space beyond the most distant known planet,—Neptune. Some comets travel in a direct, some in a retrograde path; a few near the plane of the earth’s orbit, many in planes showing every variety of inclination. Some comets regularly return after intervals of a few years; some after hundreds of years; others are only seen once or twice, and then unaccountably vanish; and not a few show by the paths they follow that they have come from interstellar space to pay our system but a single visit, passing out again to traverse we know not what other systems or regions …. When we have said that these objects obey the law of gravity, we havementioned the only circumstance—as it would appear—in which they conform to the relations observed in terrestrial and planetary arrangements. And even this law—the widest yet revealed to man—they seem to obey half unwillingly. We see the head of a comet tracing out systematically enough its proper orbit, while the comet’s tail is all unruly and disobedient …. The fact, then, is demonstrated that two of the meteor streams encountered by the earth are so far associated with two comets as to travel on the same orbits. We may not unsafely infer that all the meteor systems are in like manner associated with other comets. Nor is it very rash to assume that all comets are in like manner associated with meteor systems.”Concerning the influence of gravitation of the planets, the same author says (“Meteoric Astronomy”), “Now, the circumstances under which a comet approaching the sun on a parabolic or hyperbolic orbit can be thus affected must be regarded as exceptional. The planet’s influence must, in the first place, be very energetically exercised; in other words, the arriving comet must pass very close to the planet, for under any other circumstances the sun’s influence so enormously outvies the planet’s that the figure of the cometic orbit would be very little affected. Moreover, the planet’s attraction must produce an important balance of retardation. The planet will inevitably accelerate the comet up to a certain point, and afterwards will retard it; the latter influence must greatly exceed the former. To show how greatly the comet must be retarded,it is only necessary to mention that the actual velocity of the November meteors when they cross the orbit of Uranus is less than one-third of the velocity with which Uranus himself travels, but their velocity at the same distance from the sun, when they were approaching him from some distant stellar domain, exceeded the velocity of Uranus in his orbit in the proportion of about seven to five …. It follows, not merely as a probable inference, but, I think, as a demonstrated conclusion, that if the November meteors came originally into our system as a comet travelling sunward from infinity, then either that comet was very compact or else Uranus captured only a small portion of the comet, the remaining portions moving thenceforth on orbits wholly different from the path of the November meteors …. No other planet than Uranus can have brought about the subjection of this comet to solar rule.” In his article on comets he says, “It may be well here to consider a case in which some active force (other than gravity) exerted by the sun seems to have brought the destruction of a comet, or at least to have broken up the comet into unrecognizable fragments.” He refers to Biela’s comet, with an orbital period of six and two-thirds years, and a path which was found to approach very near to the path of the earth. In 1832 the comet crossed the earth’s track several weeks before the arrival of the earth at the same point without appreciable interference. On its second return, in 1845–46, it was found to be divided into two comets travelling side by side; in1852 they reappeared, still divided, and gradually diverging from each other. Since then they have never reappeared, though diligently sought for at every period. Professor Proctor adds, “It has been seen again, though not as a comet; nay, the occasion on which it was seen in the way referred to was predicted, and the prediction fulfilled, even in details. For a full account of its reappearance—as a meteor stream—I refer the reader to my essay on Biela’s comet in ‘Familiar Science Studies.’ ”In Miller’s “Romance of Astronomy” we read, “Encke’s comet, which possesses the smallest orbit of any connected with our system, is sensibly drawing nearer and nearer to the sun at every revolution.” In Professor Proctor’s “Cometic Mysteries,” the author says, “We hear it stated that the nucleus of a comet is made up of meteoric stones (Professor P. G. Tait says—for unknown reasons—that they resemble ‘paving stones or even bricks’) as confidently as though the earth had at some time passed through the nucleus of a comet, and some of our streets were now paved with stones which had fallen to the earth on such an occasion. As a matter of fact, all that has yet been proved is that meteoric bodies follow in the track (which is very different from the tail) of some known comets, and that probably all comets are followed by trains of meteors. These may have come out of the head or nucleus in some way as yet unexplained; but it is by no means certain that they have done so, and it is by many astronomers regarded as more than doubtful. The most important point to be noticedin the behavior of large comets as they approach the sun is, that usually the side of the coma which lies towards the sun is the scene of intense disturbance. Streams of luminous matter seem to rise continually towards the sun, attaining a certain distance from the head, when, assuming a cloud-like appearance, they seem to form an envelope around the nucleus. This envelope gradually increases its distance from the sun, growing fainter and larger, while within it the process is repeated and a new envelope is formed. This, in turn, ascends from the nucleus, expanding as it does so, while within it a new envelope is formed. Meanwhile the first one formed has grown fainter, perhaps has disappeared. But sometimes the process goes on so rapidly (a day or two sufficing for the formation of a complete new envelope) that several envelopes will be seen at the same time,—the outermost faintest, the innermost most irregular in shape and most varied in brightness, while the envelope or envelopes between are the best developed and most regular. The matter raised up in these envelopes seems to have undergone a certain change of character, causing it no longer to obey the sun’s attractive influence, but to experience a strong repulsive action from him, whereby it is apparently swept away with great rapidity to form the tail. ‘It flows past the nucleus,’ says Dr. Huggins, ‘on all sides, still ever expanding and shooting backward until a tail is formed in the direction opposite to the sun. This tail is usually curved, though sometimes rays or extra tails sensibly straight are also seen.’ ”In “The Sun as a Perpetual Machine,” Professor Proctor says, “Take, again, the phenomena of comets, which still remain among the greatest of nature’s mysteries. We have reason to believe … that the nucleus of a comet consists of an aggregation of stones similar to meteorites. Adopting this view, and assuming that these stones have absorbed somewhere gases to the amount of six times their volume (taken at atmospheric pressure), we may ask, What will be the effect of such a mass of stones advancing towards the sun at a velocity reaching in perihelion the prodigious rate of three hundred and sixty-six miles per second (as observed in the comet of 1843), being twenty-three times our orbital rate of motion?” Professor Ball says, “One of the most important results of the great shower of 1866 was the demonstration that the swarm of little bodies to which that shower owed its origin was connected with a comet. The swarm was found, in fact, to follow the exact track which the comet pursued around the sun …. Of this connection between the cometary orbits and revolving swarms of meteors many other instances could be cited. I may refer to the remarkable lists published by the British Association, in which, beside the name of the comet or the designation which astronomers had affixed to it, the meteoric swarm with which the comet is associated is also given …. On these grounds it appears to be perfectly certain that the origin of the shooting stars which appear in swarms cannot be disassociated from the origin of the comets by which thoseswarms are accompanied.” The author makes a distinction between such ordinary shooting stars and meteorites, and attributes the appearance of the latter on earth to masses thrown forth from some volcanosomewhere, but this has nothing to do with the special phenomena to be interpreted. It may be said, however, that the presence of olefiant gas as one of the occluded gases in a meteorite (four and fifty-five-hundredths per cent., as stated by Professor Proctor, in his article “The Sun as a Perpetual Machine”), and the remarkable fact, stated in the article “Spectrum Analysis” in Appleton’s Cyclopædia, that, in Winnecke’s comet of 1868, “the bands agree in position with those obtained as the spectrum of carbon, by passing the electric spark through olefiant gas, “would lead one to consider a cometic origin, for this particular meteorite at least, to be highly probable. Professor Ball further says, “There have been several instances in which a comet has approached so close to a planet that the attraction between the two bodies must have had significant influence on the planet, if the cometary mass had been at all comparable with that of the more robust body. The most celebrated instance is presented in the case of Lexell’s comet, which happened to cross the track of Jupiter. The effect upon this body was so overwhelming that it was wrenched from its original path and started afresh along a wholly different track.” The same writer, speaking of the tails of comets, says, “I have no intention to discuss here the vexed question of the tails of comets. I donot now inquire whether the repulsion by which the tail is produced be due to the intense radiation from the sun, or to electricity, or to some other agent. It is sufficient for our present purpose to note that, even if the tails of comets do gravitate towards the sun, the attraction is obscured by a more powerful repulsive force …. Nor do the directions in which the comets move exhibit any conformity; some move round the sun in one direction, some move in the opposite direction. Even the planes which contain the orbits of the comets are totally different from each other. Instead of being inclined at only a very few degrees to their mean position, the planes of the comets hardly follow any common law; they are inclined at all sorts of directions. In no respect do the comets obey those principles which are necessary to prevent constitutional disorder in the planetary system …. Now, all we have hitherto seen with regard to comets tends to show that the masses of comets are extremely small. Attempts have been made to measure them, but have always failed, because the scales in which we have attempted to weigh them have been too coarse to weigh anything of the almost spiritual texture of a comet. It is unnecessary to go as far as some have done, and to say that the weight of a large comet may be only a few pounds or a few ounces. It might be more reasonable to suppose that the weight of a large comet was thousands of tons, though even thousands of tons would be far too small a weight to admit of being measured by the very coarsebalance which is at our disposal.” In the chapter “Visitors from the Sky,” the same author says, “As such a comet in its progress across the heavens passes between us and the stars, those stars are often seen twinkling brilliantly right through the many thousand miles of cometary matter which their rays have to traverse. The lightest haze in our atmosphere would suffice to extinguish the faint gleam of these small stars; indeed, a few feet of mist would have more power of obstructing the stellar light than cometary material scores of thousands of miles thick. It is true that the central portions of many of these comets often exhibit much greater density than is found in the exterior regions; still, in the great majority of such objects there is no opacity, even in the densest part, sufficient to put out a star. In the case of the more splendid bodies of this description, it may be supposed that the matter is somewhat more densely aggregated as well as more voluminous; still, however, it will be remembered that the great comet of 1858 passed over Arcturus, and that the star was seen shining brilliantly, notwithstanding the interposition of a cometary curtain millions of miles in thickness. So far as I know, no case is known in which the nucleus of a really bright and great comet has been witnessed in the act of passage over a considerable star. It would indeed be extremely interesting to ascertain whether in such case the star experienced any considerable diminution in its lustre.”
CHAPTER VII.TEMPORARY STARS, METEORS, AND COMETS.
What, then, is the probable cause of these terrific conflagrations, as they appear to us? Take an ordinary electric induction machine,—a Holtz or a Wimshurst,—and, if the surrounding air is moist, as we operate it we will find that the results are poor, the sparks short and relatively few; but let us take the machine into another room in which the atmosphere is dry and crisp. A wondrous change will occur, and instead of a current which could scarcely flash across a few inches of space, we will now have so great an increase of energy that its tension will even cause the spark to perforate and destroy the glass walls of the heavy Leyden jars in which it is condensed. The vast realms of space, with their attenuated vapors, are the field in which the planetary electric generators operate, and into which, likewise, myriads of suns constantly pour their light and heat. We may consider this space, according to the popular view, to be uniform in constitution and density throughout all its parts,—that it is, in fact, like a vast, silent, and motionless dead sea. But this cannot possibly be true, any more than throughout the vast compass of our own atmosphere; for while some parts of space are peopled by millions of solarsystems, others, as we can plainly see, so far as telescopic vision extends, are comparatively vacant. Far more electricity is being abstracted (so to speak) in some parts of space than in others, and far more heat and light are being poured back to restore the equilibrium in some than in others. We have already seen that the temperature at the exterior surface of the terrestrial atmosphere is estimated to be more than two hundred degrees higher than in the realms of open interplanetary space; hence there must be currents,—currents of rotation like cyclones, vortical currents like whirlwinds, currents of transmission like our land- and sea-breezes and the trade-winds,—and, in fact, all space must be in a state of constant displacement and replacement, and, if visible, we should see it like a vast room filled with smoke, in which currents of every shape and direction and of all velocities would be manifest. Such currents could throw nebulæ during their condensation into rotation which could never rotate of their own motion, or gather to centers of aggregation vast whirling clouds of spatial matter, and in the spiral nebulæ we may see many such movements of rotation in apparent active progress. Of these we read in Appleton’s Cyclopædia, “They have the appearance of a maelstrom of stellar matter, and are among the most interesting objects in the heavens.” In Professor Nichol’s splendid work (“The Architecture of the Heavens,” 1850) we may see magnificent engravings of these wonderful phenomena, from the drawings by Lord Rosse,and no one can study these figures without realizing the presence of vast currents in space.In the great spiral nebula in the constellationCanes Venatici(see illustration in Chapter XII.) we perceive that the tail of the smaller nebula has been drawn into the outer convolution of the great spiral, against the radial repulsion of the latter nebula, as we can see by its curvature. This can only be due to a tremendous inflowing current in space. Were the deflection due to gravity the trend would be to the center and not to the outer convolution of the larger nebula. Professor Nichol says, “The spiral figure is characteristic of an extensive class of galaxies.” Not only in the spiral, but in other forms of nebulæ we may observe these currents of space, so that we cannot fail to perceive that they exist, and we should even conclude,a priori, that these must exist.In the elongated linear nebula in Sobieski’s Crown, illustrated above, its length is deflected into irregular curves apparently due to counter-currents of space. These gaseous nebulæ, Flammarion says, “appear like immense vaporous clouds tossed about by some rough winds, pierced with deep rents, and broken in jagged portions.” It may be said generally that every sun, as it drifts throughspace, must leave a wake of increased electric potential among the molecules which line its pathway. Beyond the limits of every vortex extend radial or tangential, polar or equatorial, streams of space, and these must extend without limit until deflected or neutralized by other conditions. Throughout all space, just as in our own atmosphere, but vastly more slowly, there must be an infinitude of movements in every direction,—movements in lines, circles, vortices, ellipses and irregular curvatures, and of all possible varieties of mass and volume.Suppose, now, a sailing vessel lighted with incandescent lamps, the electrical currents for the support of which are derived from the chemical action of sea-water on multiple pairs of suitable metallic plates arranged to extend downward as a galvanic battery into the ocean as the ship sails along, and that these plates, by the chemical action of the sea-water at ordinary, temperatures, should furnish a sufficient current to properly light the vessel. If the constancy of such current depended on the average temperature of the sea-water, at, say, sixty degrees Fahrenheit, we should find that, on suddenly crossing into the Gulf Stream, with a temperature twenty degrees higher, the energy of the battery would be rapidly increased and the lights would glow with increased brilliancy until, on emerging from the Gulf Stream at its opposite side, the original status would be gradually restored. If these distant solar systems, in their drift through space, should encounter a corresponding streamunder an increased molecular tension, more highly heated, for example, or charged with electrical potential by the surrounding solar systems, or otherwise, we should expect a similar result to ensue,—that the currents would be increased suddenly, both in quantity and intensity, and all the phenomena of “blazing” stars be revealed in the precise order in which we see them. Professor Proctor seems to have had some such idea of space vaguely in his mind when he says, in his “Familiar Essays,” “One is invited to believe that the star may have been carried by its proper motions into regions where there is a more uniform distribution of the material whence this orb recruits its fires. It may be that, in the consideration of such causes of variation affecting our sun in long-past ages, a more satisfactory explanation than any yet obtained may be found of the problem geologists found so perplexing,—the former existence of a tropical climate in places within the temperate zone, or even near the arctic regions. Sir John Herschel long since pointed to the variation of the sun as a possible cause of such changes of climate.” In confirmation of the view that such changes may be due to the passage of a solar system into or through such a “Gulf Stream” of space, we quote the following from Professor Proctor’s “Suns in Flames:” “It is noteworthy that all the stars which have blazed out suddenly, except one, have appeared in a particular region of the heavens,—the zone of the Milky Way (all, too, in one-half of that zone). The single exception is the star in the Northern Crown,and that star appeared in a region which I have found to be connected with the Milky Wayby a well-marked stream of stars; not a stream of a few stars scattered here and there, but a stream where thousands of stars are closely aggregated together, though not quite so closely as to form a visible extension of the Milky Way …. Now, the Milky Way and the outlying streams of stars connected with it seem to form a region of the stellar universe where fashioning processes are still at work.” In just such regions of potential energy should we look for such currents in space, as, on our own earth, the Gulf Stream and the trade-winds, as well as cyclones and other atmospheric movements, find their origin under precisely parallel circumstances,—to wit, the outpour upon and direct precipitation of increased quantities of heat at the tropics or other local centers of such development. The effects of such an increase of quantity and potential in an electrical current are clearly illustrated in the device previously referred to, in which electrolytic decomposition was effected in a pail of water; we find it also in the burning out of the brushes and commutators in dynamo-electric machines and in telegraphic apparatus during thunder-storms and the like. Allowing a solar system a drift through space only equal to that of our own, which has a relatively slow movement, it would traverse such a “Gulf Stream” of space seven hundred thousand miles wide in a single day. But it may not even have passed through; it may merely have grazed the margin of such a current; for the motions ofsolar systems are not controlled by the same forces as those upon which their electrical energies depend.Professor Ball, in his chapter on the great heat-wave of 1892, says, “Towards the end of July an extraordinarily high temperature, even for that period of the year, prevailed over a very large part of the North American continent. The so-called heat-wave then seems to have travelled eastward and crossed the Atlantic Ocean; … a fortnight after the occurrence of unusually great heat in the New World there was a similar experience in the Old World …. This discussion will at all events enable us to make some reply to the question which has often been asked, as to what was the cause of the great heat-wave …. It is, however, quite possible that certain changes in progress on the sun may act in a specific manner on our climate …. It cannot be denied that local, if not general, changes in the sun’s temperature must be the accompaniment of the violent disturbances by which our luminary is now and then agitated. It is, indeed, well known that there are occasional outbreaks of solar activity, and that these recur in a periodic manner; it is accordingly not without interest to notice that the present year has been one of the periods of this activity. We are certainly not going so far as to say that any connection has been definitely established between a season of exuberant sun-spots and a season remarkable for excessive warmth; but, as we know that there is a connection between the magnetic condition of theearth and the state of solar activity, it is by no means impossible that climate and sun-spots may also stand in some relationship to each other.” These local deviations are doubtless due to planetary positions with reference to the sun, but more general variations must depend upon the constitution of such parts of space as the solar system may occupy; but even then they will be but temporary, since the sun’s volume will rapidly expand or contract so as finally to restore the normal emission of solar heat, as will be further explained later on in this work.Phenomena of a new or temporary star, a “star in flames.”—1, normal state of star, photosphere more highly heated than chromosphere: 2, stage of highest incandescence, chromosphere expanded and more highly heated than photosphere, bright line spectrum: 3, stage of recession, chromosphere diminishing in incandescence, heat acting upon solar core, numerous spots, volatilization of metallic surface, spectrum of dark absorption bands; 4, return to normal state again.There are other causes also, readily conceivable, for such increased electrical action; for instance, in that thickly-peopled region of space, two solar systems adjacent might easily have their exterior planets so related to each other as suddenly, at their points of nearest approach, to cause one or more to direct an abnormally large electrical current into the sun of the adjacent system; this would correspond in electric energy, in fact, to a violent “perturbation” in its orbit by the action of gravity produced by a neighboring planet or system. No reversal of polarity could take place between these planets under these circumstances, any more than between the earth and the moon. In some portions of the Milky Way, doubtless, suns blaze by dozens across the sky at night, and by day as well, to which, in our more solitary skies, we are strangers. Revolving in perfect harmony, perturbations must nevertheless be frequent, and to what limits they may there be confined we shallnever know until we realize the extent of these galaxies and the relative contiguity of their solar systems to each other. It is enough to show how such variations may occur; in what particular way they do occur does not affect the question of their origin. Even if such increased energy were to continue by permanently increased planetary action, it is not necessary to suppose that a corresponding permanent increase of light and heat would result on the part of the sun, for its density is such (only one-fourth that of the earth) that, under the tremendous force of its gravity (twenty-seven and one-tenth times that of the earth), its constituents cannot be maintained in solid form, but must be, as before stated, either liquid or gaseous, and perhaps in part both. Now, as it has been computed that the sun, by contraction to its present density, would have evolved its present light and heat for a period of millions of years, it is obvious that any increase in its present volume, without increase of mass, would produce precisely opposite and compensated results, so that the sun could receive from outside sources as much heat as would expand its present volume to that at the initial point of such assumed condensation without increased emission of light and heat. The sun is thus, in effect, a self-compensating machine, and its passage through a region of increased electrical generation would first manifest itself in a vast increase of brilliancy, due to higher incandescence of its hydrogen envelope; this, in turn, would be communicated to the deeper structures of the sun, producing increased volatilizationand dark absorption bands, and finally to the whole solar mass, expanding its volume in proportion to the heat absorbed. Hence we should see precisely the phenomena that we do see in flaming stars or so-called new stars. We find such compensations all through nature, and it is simply inaccordance with her universal laws that they occur. It is a singular circumstance that the catastrophe which is foretold in the biblical record as the termination of all human life on earth, for the present cycle, at least, should be almost literally in accordance with the phenomena characteristic of such an increase of solar energy, and one produced in some such manner. If the temperature of the solar atmosphere were rapidly raised by increased planetary action to a point which would reverse the lines of hydrogen from dark to bright, say to a brightness eight hundred times that of the normal, as in the case of the temporary star cited, though the heat would not, of course, be increased in any such proportion, yet the heavens would be indeed rolled up as a scroll, and all life would be extinguished in a very brief period. But the planets would continue to roll along their orbits, the integrity of the earth’s mass would still be intact, and after a few days or weeks the sun would begin to decline in brightness, the volatilized vapors would slowly recede within the solar atmosphere, and the temperature would gradually fall again to its normal, leaving, however, a lifeless world to roll on its way henceforth, but as bright and cheerful in all its possibilities, when the former conditions had gradually become restored, as before. Perhaps some distant astronomer in the neighborhood of Sirius—if we shall have travelled so far away by that time—might send a note to the morning papers to announce that the temporary star near Alpha Centauri had again receded to the tenthmagnitude. In due time—perhaps a thousand years—all would be ready for a new development of life, and the cycle would continue as before. Perchance, too, in some deep abyss, or buried far beneath the surface, some germs of life might still continue to exist; and from these, like the seeds resurrected from buried mummies, a new life might again begin, guided along once more through vast ages in a progressive ascent from development to development until, in some new and strange forms, the higher types of life might again appear. To these there would indeed be revealed a new heaven and a new earth. Who knows how many such cycles of life may have come and gone on earth, in which, like the dwellers of Jerusalem, new peoples have built new cities, one above another, upon the unknown graves of the past? In the words of Tennyson,—“A wondrous eft was of old the Lord and Master of earth,For him did his high sun flame, and his river billowing ran,And he felt himself in his force to be Nature’s crowning race.As nine months go to the shaping an infant ripe for his birth,So many a million of ages have gone to the making man:He now is first, but is he the last?”Whatever the coming, the progress, or the going of life on earth, the course of our solar system will go on the same, the processes of creation unchanged and her mechanism unimpaired. It is obvious that no such conditions could prevail in the return to unorganizable chaos which must be the consequence of any possible planetary collisions in space. No conceivable process of creation couldreturn a system disrupted into meteorites to an operative solar system again. Even the nebular hypothesis contemplates nothing of that sort as, by the wildest conjecture, ever possible. But with us the danger is far distant. Professor Proctor says, in his article “Suns in Flames,” “As Sir William Herschel long since pointed out, we can recognize in various parts of the heavens various stages of development, and chief among the regions where as yet nature’s work seems incomplete is the Galactic zone,—especially that half of it where the Milky Way consists of irregular streams and clouds of stellar light. As there is no reason for believing that our sun belongs to this part of the galaxy, but, on the contrary, good ground for considering that he belongs to the class of insulated stars, few of which have shown signs of irregular variation, while none have ever blazed suddenly out with many hundred times their former lustre, we may fairly infer a very high degree of probability in favor of the belief that, for many ages still to come, the sun will continue steadily to discharge his duties as fire, light, and life of the solar system.” The passage of our system through gradually changing regions of space, as contrasted with streams or vortices, could not affect our sun’s light even temporarily, as the contraction and expansion of its volume would fully compensate for any such gradual or partial variation, and, by position, he is far from likely to pass into any of those whirlpools or torrents of space which seem to mark at irregular intervals the region of the irregularly variable stars.Allied in appearance to such stars which suddenly flame out in space, but totally different in reality, are comets. These strangers to our own system have excited the wonder and astonishment of mankind from the earliest ages. They seem to defy all rules and all explanation; but, when properly examined, they will fall inevitably into the general scheme of the source and mode of solar energy which we have endeavored to present. These bodies enter our solar system from without. Appleton’s Cyclopædia says, “Schiaparelli, to whom the discovery is in part due, considers the meteors to be dispersed portions of the comet’s original substance,—that is, of the substance with whichthe comet entered the solar domain.” Professor Proctor, “Meteoric Astronomy,” says, “A word or two may be permitted on the question of the condition ofcomets freshly arriving on the scene of the solar system. It is assumed sometimes that the train of meteors already exists when the cometfirst comes within the solar domain.” In the “Romance of Astronomy” (R. Kalley Miller, M.A.) it is said, “In a sort of debatable territory between our own solar system and the infinite stellar universe around we come upon these erratic and anomalous bodies—the comets; some of which have accidentally become permanent attendants upon our sun; others have only paid it a single casual visit in the course of their wanderings through space, and are not likely again to come within the range of its attracting influence; while countless millions are doubtless scattered throughout the realms of theinfinite, whose existence will never be revealed to human ken at all.” Professor Helmholtz, in fact (see addendum to his lecture on the origin of the planetary system), advanced the idea in a speculative way, that our terrestrial life might have had its origin in one of these meteoric bodies by the “transmission of organisms through space.” In Professor Proctor’s article on comets (“Mysteries of Time and Space”) he says, “The paths followed by comets show no resemblance either to the planetary orbits or to each other. Here we see a comet travelling in a path of moderate extent and not very eccentric; then another which rushes from a distance of two or three thousand millions of miles, approaches the sun with ever-increasing velocity until nearer to him than parts of his own corona (as seen in eclipses), sweeps around him with inconceivable rapidity, and makes off again to where the aphelion of its orbit lies far out in space beyond the most distant known planet,—Neptune. Some comets travel in a direct, some in a retrograde path; a few near the plane of the earth’s orbit, many in planes showing every variety of inclination. Some comets regularly return after intervals of a few years; some after hundreds of years; others are only seen once or twice, and then unaccountably vanish; and not a few show by the paths they follow that they have come from interstellar space to pay our system but a single visit, passing out again to traverse we know not what other systems or regions …. When we have said that these objects obey the law of gravity, we havementioned the only circumstance—as it would appear—in which they conform to the relations observed in terrestrial and planetary arrangements. And even this law—the widest yet revealed to man—they seem to obey half unwillingly. We see the head of a comet tracing out systematically enough its proper orbit, while the comet’s tail is all unruly and disobedient …. The fact, then, is demonstrated that two of the meteor streams encountered by the earth are so far associated with two comets as to travel on the same orbits. We may not unsafely infer that all the meteor systems are in like manner associated with other comets. Nor is it very rash to assume that all comets are in like manner associated with meteor systems.”Concerning the influence of gravitation of the planets, the same author says (“Meteoric Astronomy”), “Now, the circumstances under which a comet approaching the sun on a parabolic or hyperbolic orbit can be thus affected must be regarded as exceptional. The planet’s influence must, in the first place, be very energetically exercised; in other words, the arriving comet must pass very close to the planet, for under any other circumstances the sun’s influence so enormously outvies the planet’s that the figure of the cometic orbit would be very little affected. Moreover, the planet’s attraction must produce an important balance of retardation. The planet will inevitably accelerate the comet up to a certain point, and afterwards will retard it; the latter influence must greatly exceed the former. To show how greatly the comet must be retarded,it is only necessary to mention that the actual velocity of the November meteors when they cross the orbit of Uranus is less than one-third of the velocity with which Uranus himself travels, but their velocity at the same distance from the sun, when they were approaching him from some distant stellar domain, exceeded the velocity of Uranus in his orbit in the proportion of about seven to five …. It follows, not merely as a probable inference, but, I think, as a demonstrated conclusion, that if the November meteors came originally into our system as a comet travelling sunward from infinity, then either that comet was very compact or else Uranus captured only a small portion of the comet, the remaining portions moving thenceforth on orbits wholly different from the path of the November meteors …. No other planet than Uranus can have brought about the subjection of this comet to solar rule.” In his article on comets he says, “It may be well here to consider a case in which some active force (other than gravity) exerted by the sun seems to have brought the destruction of a comet, or at least to have broken up the comet into unrecognizable fragments.” He refers to Biela’s comet, with an orbital period of six and two-thirds years, and a path which was found to approach very near to the path of the earth. In 1832 the comet crossed the earth’s track several weeks before the arrival of the earth at the same point without appreciable interference. On its second return, in 1845–46, it was found to be divided into two comets travelling side by side; in1852 they reappeared, still divided, and gradually diverging from each other. Since then they have never reappeared, though diligently sought for at every period. Professor Proctor adds, “It has been seen again, though not as a comet; nay, the occasion on which it was seen in the way referred to was predicted, and the prediction fulfilled, even in details. For a full account of its reappearance—as a meteor stream—I refer the reader to my essay on Biela’s comet in ‘Familiar Science Studies.’ ”In Miller’s “Romance of Astronomy” we read, “Encke’s comet, which possesses the smallest orbit of any connected with our system, is sensibly drawing nearer and nearer to the sun at every revolution.” In Professor Proctor’s “Cometic Mysteries,” the author says, “We hear it stated that the nucleus of a comet is made up of meteoric stones (Professor P. G. Tait says—for unknown reasons—that they resemble ‘paving stones or even bricks’) as confidently as though the earth had at some time passed through the nucleus of a comet, and some of our streets were now paved with stones which had fallen to the earth on such an occasion. As a matter of fact, all that has yet been proved is that meteoric bodies follow in the track (which is very different from the tail) of some known comets, and that probably all comets are followed by trains of meteors. These may have come out of the head or nucleus in some way as yet unexplained; but it is by no means certain that they have done so, and it is by many astronomers regarded as more than doubtful. The most important point to be noticedin the behavior of large comets as they approach the sun is, that usually the side of the coma which lies towards the sun is the scene of intense disturbance. Streams of luminous matter seem to rise continually towards the sun, attaining a certain distance from the head, when, assuming a cloud-like appearance, they seem to form an envelope around the nucleus. This envelope gradually increases its distance from the sun, growing fainter and larger, while within it the process is repeated and a new envelope is formed. This, in turn, ascends from the nucleus, expanding as it does so, while within it a new envelope is formed. Meanwhile the first one formed has grown fainter, perhaps has disappeared. But sometimes the process goes on so rapidly (a day or two sufficing for the formation of a complete new envelope) that several envelopes will be seen at the same time,—the outermost faintest, the innermost most irregular in shape and most varied in brightness, while the envelope or envelopes between are the best developed and most regular. The matter raised up in these envelopes seems to have undergone a certain change of character, causing it no longer to obey the sun’s attractive influence, but to experience a strong repulsive action from him, whereby it is apparently swept away with great rapidity to form the tail. ‘It flows past the nucleus,’ says Dr. Huggins, ‘on all sides, still ever expanding and shooting backward until a tail is formed in the direction opposite to the sun. This tail is usually curved, though sometimes rays or extra tails sensibly straight are also seen.’ ”In “The Sun as a Perpetual Machine,” Professor Proctor says, “Take, again, the phenomena of comets, which still remain among the greatest of nature’s mysteries. We have reason to believe … that the nucleus of a comet consists of an aggregation of stones similar to meteorites. Adopting this view, and assuming that these stones have absorbed somewhere gases to the amount of six times their volume (taken at atmospheric pressure), we may ask, What will be the effect of such a mass of stones advancing towards the sun at a velocity reaching in perihelion the prodigious rate of three hundred and sixty-six miles per second (as observed in the comet of 1843), being twenty-three times our orbital rate of motion?” Professor Ball says, “One of the most important results of the great shower of 1866 was the demonstration that the swarm of little bodies to which that shower owed its origin was connected with a comet. The swarm was found, in fact, to follow the exact track which the comet pursued around the sun …. Of this connection between the cometary orbits and revolving swarms of meteors many other instances could be cited. I may refer to the remarkable lists published by the British Association, in which, beside the name of the comet or the designation which astronomers had affixed to it, the meteoric swarm with which the comet is associated is also given …. On these grounds it appears to be perfectly certain that the origin of the shooting stars which appear in swarms cannot be disassociated from the origin of the comets by which thoseswarms are accompanied.” The author makes a distinction between such ordinary shooting stars and meteorites, and attributes the appearance of the latter on earth to masses thrown forth from some volcanosomewhere, but this has nothing to do with the special phenomena to be interpreted. It may be said, however, that the presence of olefiant gas as one of the occluded gases in a meteorite (four and fifty-five-hundredths per cent., as stated by Professor Proctor, in his article “The Sun as a Perpetual Machine”), and the remarkable fact, stated in the article “Spectrum Analysis” in Appleton’s Cyclopædia, that, in Winnecke’s comet of 1868, “the bands agree in position with those obtained as the spectrum of carbon, by passing the electric spark through olefiant gas, “would lead one to consider a cometic origin, for this particular meteorite at least, to be highly probable. Professor Ball further says, “There have been several instances in which a comet has approached so close to a planet that the attraction between the two bodies must have had significant influence on the planet, if the cometary mass had been at all comparable with that of the more robust body. The most celebrated instance is presented in the case of Lexell’s comet, which happened to cross the track of Jupiter. The effect upon this body was so overwhelming that it was wrenched from its original path and started afresh along a wholly different track.” The same writer, speaking of the tails of comets, says, “I have no intention to discuss here the vexed question of the tails of comets. I donot now inquire whether the repulsion by which the tail is produced be due to the intense radiation from the sun, or to electricity, or to some other agent. It is sufficient for our present purpose to note that, even if the tails of comets do gravitate towards the sun, the attraction is obscured by a more powerful repulsive force …. Nor do the directions in which the comets move exhibit any conformity; some move round the sun in one direction, some move in the opposite direction. Even the planes which contain the orbits of the comets are totally different from each other. Instead of being inclined at only a very few degrees to their mean position, the planes of the comets hardly follow any common law; they are inclined at all sorts of directions. In no respect do the comets obey those principles which are necessary to prevent constitutional disorder in the planetary system …. Now, all we have hitherto seen with regard to comets tends to show that the masses of comets are extremely small. Attempts have been made to measure them, but have always failed, because the scales in which we have attempted to weigh them have been too coarse to weigh anything of the almost spiritual texture of a comet. It is unnecessary to go as far as some have done, and to say that the weight of a large comet may be only a few pounds or a few ounces. It might be more reasonable to suppose that the weight of a large comet was thousands of tons, though even thousands of tons would be far too small a weight to admit of being measured by the very coarsebalance which is at our disposal.” In the chapter “Visitors from the Sky,” the same author says, “As such a comet in its progress across the heavens passes between us and the stars, those stars are often seen twinkling brilliantly right through the many thousand miles of cometary matter which their rays have to traverse. The lightest haze in our atmosphere would suffice to extinguish the faint gleam of these small stars; indeed, a few feet of mist would have more power of obstructing the stellar light than cometary material scores of thousands of miles thick. It is true that the central portions of many of these comets often exhibit much greater density than is found in the exterior regions; still, in the great majority of such objects there is no opacity, even in the densest part, sufficient to put out a star. In the case of the more splendid bodies of this description, it may be supposed that the matter is somewhat more densely aggregated as well as more voluminous; still, however, it will be remembered that the great comet of 1858 passed over Arcturus, and that the star was seen shining brilliantly, notwithstanding the interposition of a cometary curtain millions of miles in thickness. So far as I know, no case is known in which the nucleus of a really bright and great comet has been witnessed in the act of passage over a considerable star. It would indeed be extremely interesting to ascertain whether in such case the star experienced any considerable diminution in its lustre.”
What, then, is the probable cause of these terrific conflagrations, as they appear to us? Take an ordinary electric induction machine,—a Holtz or a Wimshurst,—and, if the surrounding air is moist, as we operate it we will find that the results are poor, the sparks short and relatively few; but let us take the machine into another room in which the atmosphere is dry and crisp. A wondrous change will occur, and instead of a current which could scarcely flash across a few inches of space, we will now have so great an increase of energy that its tension will even cause the spark to perforate and destroy the glass walls of the heavy Leyden jars in which it is condensed. The vast realms of space, with their attenuated vapors, are the field in which the planetary electric generators operate, and into which, likewise, myriads of suns constantly pour their light and heat. We may consider this space, according to the popular view, to be uniform in constitution and density throughout all its parts,—that it is, in fact, like a vast, silent, and motionless dead sea. But this cannot possibly be true, any more than throughout the vast compass of our own atmosphere; for while some parts of space are peopled by millions of solarsystems, others, as we can plainly see, so far as telescopic vision extends, are comparatively vacant. Far more electricity is being abstracted (so to speak) in some parts of space than in others, and far more heat and light are being poured back to restore the equilibrium in some than in others. We have already seen that the temperature at the exterior surface of the terrestrial atmosphere is estimated to be more than two hundred degrees higher than in the realms of open interplanetary space; hence there must be currents,—currents of rotation like cyclones, vortical currents like whirlwinds, currents of transmission like our land- and sea-breezes and the trade-winds,—and, in fact, all space must be in a state of constant displacement and replacement, and, if visible, we should see it like a vast room filled with smoke, in which currents of every shape and direction and of all velocities would be manifest. Such currents could throw nebulæ during their condensation into rotation which could never rotate of their own motion, or gather to centers of aggregation vast whirling clouds of spatial matter, and in the spiral nebulæ we may see many such movements of rotation in apparent active progress. Of these we read in Appleton’s Cyclopædia, “They have the appearance of a maelstrom of stellar matter, and are among the most interesting objects in the heavens.” In Professor Nichol’s splendid work (“The Architecture of the Heavens,” 1850) we may see magnificent engravings of these wonderful phenomena, from the drawings by Lord Rosse,and no one can study these figures without realizing the presence of vast currents in space.
In the great spiral nebula in the constellationCanes Venatici(see illustration in Chapter XII.) we perceive that the tail of the smaller nebula has been drawn into the outer convolution of the great spiral, against the radial repulsion of the latter nebula, as we can see by its curvature. This can only be due to a tremendous inflowing current in space. Were the deflection due to gravity the trend would be to the center and not to the outer convolution of the larger nebula. Professor Nichol says, “The spiral figure is characteristic of an extensive class of galaxies.” Not only in the spiral, but in other forms of nebulæ we may observe these currents of space, so that we cannot fail to perceive that they exist, and we should even conclude,a priori, that these must exist.
In the elongated linear nebula in Sobieski’s Crown, illustrated above, its length is deflected into irregular curves apparently due to counter-currents of space. These gaseous nebulæ, Flammarion says, “appear like immense vaporous clouds tossed about by some rough winds, pierced with deep rents, and broken in jagged portions.” It may be said generally that every sun, as it drifts throughspace, must leave a wake of increased electric potential among the molecules which line its pathway. Beyond the limits of every vortex extend radial or tangential, polar or equatorial, streams of space, and these must extend without limit until deflected or neutralized by other conditions. Throughout all space, just as in our own atmosphere, but vastly more slowly, there must be an infinitude of movements in every direction,—movements in lines, circles, vortices, ellipses and irregular curvatures, and of all possible varieties of mass and volume.
Suppose, now, a sailing vessel lighted with incandescent lamps, the electrical currents for the support of which are derived from the chemical action of sea-water on multiple pairs of suitable metallic plates arranged to extend downward as a galvanic battery into the ocean as the ship sails along, and that these plates, by the chemical action of the sea-water at ordinary, temperatures, should furnish a sufficient current to properly light the vessel. If the constancy of such current depended on the average temperature of the sea-water, at, say, sixty degrees Fahrenheit, we should find that, on suddenly crossing into the Gulf Stream, with a temperature twenty degrees higher, the energy of the battery would be rapidly increased and the lights would glow with increased brilliancy until, on emerging from the Gulf Stream at its opposite side, the original status would be gradually restored. If these distant solar systems, in their drift through space, should encounter a corresponding streamunder an increased molecular tension, more highly heated, for example, or charged with electrical potential by the surrounding solar systems, or otherwise, we should expect a similar result to ensue,—that the currents would be increased suddenly, both in quantity and intensity, and all the phenomena of “blazing” stars be revealed in the precise order in which we see them. Professor Proctor seems to have had some such idea of space vaguely in his mind when he says, in his “Familiar Essays,” “One is invited to believe that the star may have been carried by its proper motions into regions where there is a more uniform distribution of the material whence this orb recruits its fires. It may be that, in the consideration of such causes of variation affecting our sun in long-past ages, a more satisfactory explanation than any yet obtained may be found of the problem geologists found so perplexing,—the former existence of a tropical climate in places within the temperate zone, or even near the arctic regions. Sir John Herschel long since pointed to the variation of the sun as a possible cause of such changes of climate.” In confirmation of the view that such changes may be due to the passage of a solar system into or through such a “Gulf Stream” of space, we quote the following from Professor Proctor’s “Suns in Flames:” “It is noteworthy that all the stars which have blazed out suddenly, except one, have appeared in a particular region of the heavens,—the zone of the Milky Way (all, too, in one-half of that zone). The single exception is the star in the Northern Crown,and that star appeared in a region which I have found to be connected with the Milky Wayby a well-marked stream of stars; not a stream of a few stars scattered here and there, but a stream where thousands of stars are closely aggregated together, though not quite so closely as to form a visible extension of the Milky Way …. Now, the Milky Way and the outlying streams of stars connected with it seem to form a region of the stellar universe where fashioning processes are still at work.” In just such regions of potential energy should we look for such currents in space, as, on our own earth, the Gulf Stream and the trade-winds, as well as cyclones and other atmospheric movements, find their origin under precisely parallel circumstances,—to wit, the outpour upon and direct precipitation of increased quantities of heat at the tropics or other local centers of such development. The effects of such an increase of quantity and potential in an electrical current are clearly illustrated in the device previously referred to, in which electrolytic decomposition was effected in a pail of water; we find it also in the burning out of the brushes and commutators in dynamo-electric machines and in telegraphic apparatus during thunder-storms and the like. Allowing a solar system a drift through space only equal to that of our own, which has a relatively slow movement, it would traverse such a “Gulf Stream” of space seven hundred thousand miles wide in a single day. But it may not even have passed through; it may merely have grazed the margin of such a current; for the motions ofsolar systems are not controlled by the same forces as those upon which their electrical energies depend.
Professor Ball, in his chapter on the great heat-wave of 1892, says, “Towards the end of July an extraordinarily high temperature, even for that period of the year, prevailed over a very large part of the North American continent. The so-called heat-wave then seems to have travelled eastward and crossed the Atlantic Ocean; … a fortnight after the occurrence of unusually great heat in the New World there was a similar experience in the Old World …. This discussion will at all events enable us to make some reply to the question which has often been asked, as to what was the cause of the great heat-wave …. It is, however, quite possible that certain changes in progress on the sun may act in a specific manner on our climate …. It cannot be denied that local, if not general, changes in the sun’s temperature must be the accompaniment of the violent disturbances by which our luminary is now and then agitated. It is, indeed, well known that there are occasional outbreaks of solar activity, and that these recur in a periodic manner; it is accordingly not without interest to notice that the present year has been one of the periods of this activity. We are certainly not going so far as to say that any connection has been definitely established between a season of exuberant sun-spots and a season remarkable for excessive warmth; but, as we know that there is a connection between the magnetic condition of theearth and the state of solar activity, it is by no means impossible that climate and sun-spots may also stand in some relationship to each other.” These local deviations are doubtless due to planetary positions with reference to the sun, but more general variations must depend upon the constitution of such parts of space as the solar system may occupy; but even then they will be but temporary, since the sun’s volume will rapidly expand or contract so as finally to restore the normal emission of solar heat, as will be further explained later on in this work.
Phenomena of a new or temporary star, a “star in flames.”—1, normal state of star, photosphere more highly heated than chromosphere: 2, stage of highest incandescence, chromosphere expanded and more highly heated than photosphere, bright line spectrum: 3, stage of recession, chromosphere diminishing in incandescence, heat acting upon solar core, numerous spots, volatilization of metallic surface, spectrum of dark absorption bands; 4, return to normal state again.
Phenomena of a new or temporary star, a “star in flames.”—1, normal state of star, photosphere more highly heated than chromosphere: 2, stage of highest incandescence, chromosphere expanded and more highly heated than photosphere, bright line spectrum: 3, stage of recession, chromosphere diminishing in incandescence, heat acting upon solar core, numerous spots, volatilization of metallic surface, spectrum of dark absorption bands; 4, return to normal state again.
There are other causes also, readily conceivable, for such increased electrical action; for instance, in that thickly-peopled region of space, two solar systems adjacent might easily have their exterior planets so related to each other as suddenly, at their points of nearest approach, to cause one or more to direct an abnormally large electrical current into the sun of the adjacent system; this would correspond in electric energy, in fact, to a violent “perturbation” in its orbit by the action of gravity produced by a neighboring planet or system. No reversal of polarity could take place between these planets under these circumstances, any more than between the earth and the moon. In some portions of the Milky Way, doubtless, suns blaze by dozens across the sky at night, and by day as well, to which, in our more solitary skies, we are strangers. Revolving in perfect harmony, perturbations must nevertheless be frequent, and to what limits they may there be confined we shallnever know until we realize the extent of these galaxies and the relative contiguity of their solar systems to each other. It is enough to show how such variations may occur; in what particular way they do occur does not affect the question of their origin. Even if such increased energy were to continue by permanently increased planetary action, it is not necessary to suppose that a corresponding permanent increase of light and heat would result on the part of the sun, for its density is such (only one-fourth that of the earth) that, under the tremendous force of its gravity (twenty-seven and one-tenth times that of the earth), its constituents cannot be maintained in solid form, but must be, as before stated, either liquid or gaseous, and perhaps in part both. Now, as it has been computed that the sun, by contraction to its present density, would have evolved its present light and heat for a period of millions of years, it is obvious that any increase in its present volume, without increase of mass, would produce precisely opposite and compensated results, so that the sun could receive from outside sources as much heat as would expand its present volume to that at the initial point of such assumed condensation without increased emission of light and heat. The sun is thus, in effect, a self-compensating machine, and its passage through a region of increased electrical generation would first manifest itself in a vast increase of brilliancy, due to higher incandescence of its hydrogen envelope; this, in turn, would be communicated to the deeper structures of the sun, producing increased volatilizationand dark absorption bands, and finally to the whole solar mass, expanding its volume in proportion to the heat absorbed. Hence we should see precisely the phenomena that we do see in flaming stars or so-called new stars. We find such compensations all through nature, and it is simply inaccordance with her universal laws that they occur. It is a singular circumstance that the catastrophe which is foretold in the biblical record as the termination of all human life on earth, for the present cycle, at least, should be almost literally in accordance with the phenomena characteristic of such an increase of solar energy, and one produced in some such manner. If the temperature of the solar atmosphere were rapidly raised by increased planetary action to a point which would reverse the lines of hydrogen from dark to bright, say to a brightness eight hundred times that of the normal, as in the case of the temporary star cited, though the heat would not, of course, be increased in any such proportion, yet the heavens would be indeed rolled up as a scroll, and all life would be extinguished in a very brief period. But the planets would continue to roll along their orbits, the integrity of the earth’s mass would still be intact, and after a few days or weeks the sun would begin to decline in brightness, the volatilized vapors would slowly recede within the solar atmosphere, and the temperature would gradually fall again to its normal, leaving, however, a lifeless world to roll on its way henceforth, but as bright and cheerful in all its possibilities, when the former conditions had gradually become restored, as before. Perhaps some distant astronomer in the neighborhood of Sirius—if we shall have travelled so far away by that time—might send a note to the morning papers to announce that the temporary star near Alpha Centauri had again receded to the tenthmagnitude. In due time—perhaps a thousand years—all would be ready for a new development of life, and the cycle would continue as before. Perchance, too, in some deep abyss, or buried far beneath the surface, some germs of life might still continue to exist; and from these, like the seeds resurrected from buried mummies, a new life might again begin, guided along once more through vast ages in a progressive ascent from development to development until, in some new and strange forms, the higher types of life might again appear. To these there would indeed be revealed a new heaven and a new earth. Who knows how many such cycles of life may have come and gone on earth, in which, like the dwellers of Jerusalem, new peoples have built new cities, one above another, upon the unknown graves of the past? In the words of Tennyson,—
“A wondrous eft was of old the Lord and Master of earth,For him did his high sun flame, and his river billowing ran,And he felt himself in his force to be Nature’s crowning race.As nine months go to the shaping an infant ripe for his birth,So many a million of ages have gone to the making man:He now is first, but is he the last?”
“A wondrous eft was of old the Lord and Master of earth,
For him did his high sun flame, and his river billowing ran,
And he felt himself in his force to be Nature’s crowning race.
As nine months go to the shaping an infant ripe for his birth,
So many a million of ages have gone to the making man:
He now is first, but is he the last?”
Whatever the coming, the progress, or the going of life on earth, the course of our solar system will go on the same, the processes of creation unchanged and her mechanism unimpaired. It is obvious that no such conditions could prevail in the return to unorganizable chaos which must be the consequence of any possible planetary collisions in space. No conceivable process of creation couldreturn a system disrupted into meteorites to an operative solar system again. Even the nebular hypothesis contemplates nothing of that sort as, by the wildest conjecture, ever possible. But with us the danger is far distant. Professor Proctor says, in his article “Suns in Flames,” “As Sir William Herschel long since pointed out, we can recognize in various parts of the heavens various stages of development, and chief among the regions where as yet nature’s work seems incomplete is the Galactic zone,—especially that half of it where the Milky Way consists of irregular streams and clouds of stellar light. As there is no reason for believing that our sun belongs to this part of the galaxy, but, on the contrary, good ground for considering that he belongs to the class of insulated stars, few of which have shown signs of irregular variation, while none have ever blazed suddenly out with many hundred times their former lustre, we may fairly infer a very high degree of probability in favor of the belief that, for many ages still to come, the sun will continue steadily to discharge his duties as fire, light, and life of the solar system.” The passage of our system through gradually changing regions of space, as contrasted with streams or vortices, could not affect our sun’s light even temporarily, as the contraction and expansion of its volume would fully compensate for any such gradual or partial variation, and, by position, he is far from likely to pass into any of those whirlpools or torrents of space which seem to mark at irregular intervals the region of the irregularly variable stars.
Allied in appearance to such stars which suddenly flame out in space, but totally different in reality, are comets. These strangers to our own system have excited the wonder and astonishment of mankind from the earliest ages. They seem to defy all rules and all explanation; but, when properly examined, they will fall inevitably into the general scheme of the source and mode of solar energy which we have endeavored to present. These bodies enter our solar system from without. Appleton’s Cyclopædia says, “Schiaparelli, to whom the discovery is in part due, considers the meteors to be dispersed portions of the comet’s original substance,—that is, of the substance with whichthe comet entered the solar domain.” Professor Proctor, “Meteoric Astronomy,” says, “A word or two may be permitted on the question of the condition ofcomets freshly arriving on the scene of the solar system. It is assumed sometimes that the train of meteors already exists when the cometfirst comes within the solar domain.” In the “Romance of Astronomy” (R. Kalley Miller, M.A.) it is said, “In a sort of debatable territory between our own solar system and the infinite stellar universe around we come upon these erratic and anomalous bodies—the comets; some of which have accidentally become permanent attendants upon our sun; others have only paid it a single casual visit in the course of their wanderings through space, and are not likely again to come within the range of its attracting influence; while countless millions are doubtless scattered throughout the realms of theinfinite, whose existence will never be revealed to human ken at all.” Professor Helmholtz, in fact (see addendum to his lecture on the origin of the planetary system), advanced the idea in a speculative way, that our terrestrial life might have had its origin in one of these meteoric bodies by the “transmission of organisms through space.” In Professor Proctor’s article on comets (“Mysteries of Time and Space”) he says, “The paths followed by comets show no resemblance either to the planetary orbits or to each other. Here we see a comet travelling in a path of moderate extent and not very eccentric; then another which rushes from a distance of two or three thousand millions of miles, approaches the sun with ever-increasing velocity until nearer to him than parts of his own corona (as seen in eclipses), sweeps around him with inconceivable rapidity, and makes off again to where the aphelion of its orbit lies far out in space beyond the most distant known planet,—Neptune. Some comets travel in a direct, some in a retrograde path; a few near the plane of the earth’s orbit, many in planes showing every variety of inclination. Some comets regularly return after intervals of a few years; some after hundreds of years; others are only seen once or twice, and then unaccountably vanish; and not a few show by the paths they follow that they have come from interstellar space to pay our system but a single visit, passing out again to traverse we know not what other systems or regions …. When we have said that these objects obey the law of gravity, we havementioned the only circumstance—as it would appear—in which they conform to the relations observed in terrestrial and planetary arrangements. And even this law—the widest yet revealed to man—they seem to obey half unwillingly. We see the head of a comet tracing out systematically enough its proper orbit, while the comet’s tail is all unruly and disobedient …. The fact, then, is demonstrated that two of the meteor streams encountered by the earth are so far associated with two comets as to travel on the same orbits. We may not unsafely infer that all the meteor systems are in like manner associated with other comets. Nor is it very rash to assume that all comets are in like manner associated with meteor systems.”
Concerning the influence of gravitation of the planets, the same author says (“Meteoric Astronomy”), “Now, the circumstances under which a comet approaching the sun on a parabolic or hyperbolic orbit can be thus affected must be regarded as exceptional. The planet’s influence must, in the first place, be very energetically exercised; in other words, the arriving comet must pass very close to the planet, for under any other circumstances the sun’s influence so enormously outvies the planet’s that the figure of the cometic orbit would be very little affected. Moreover, the planet’s attraction must produce an important balance of retardation. The planet will inevitably accelerate the comet up to a certain point, and afterwards will retard it; the latter influence must greatly exceed the former. To show how greatly the comet must be retarded,it is only necessary to mention that the actual velocity of the November meteors when they cross the orbit of Uranus is less than one-third of the velocity with which Uranus himself travels, but their velocity at the same distance from the sun, when they were approaching him from some distant stellar domain, exceeded the velocity of Uranus in his orbit in the proportion of about seven to five …. It follows, not merely as a probable inference, but, I think, as a demonstrated conclusion, that if the November meteors came originally into our system as a comet travelling sunward from infinity, then either that comet was very compact or else Uranus captured only a small portion of the comet, the remaining portions moving thenceforth on orbits wholly different from the path of the November meteors …. No other planet than Uranus can have brought about the subjection of this comet to solar rule.” In his article on comets he says, “It may be well here to consider a case in which some active force (other than gravity) exerted by the sun seems to have brought the destruction of a comet, or at least to have broken up the comet into unrecognizable fragments.” He refers to Biela’s comet, with an orbital period of six and two-thirds years, and a path which was found to approach very near to the path of the earth. In 1832 the comet crossed the earth’s track several weeks before the arrival of the earth at the same point without appreciable interference. On its second return, in 1845–46, it was found to be divided into two comets travelling side by side; in1852 they reappeared, still divided, and gradually diverging from each other. Since then they have never reappeared, though diligently sought for at every period. Professor Proctor adds, “It has been seen again, though not as a comet; nay, the occasion on which it was seen in the way referred to was predicted, and the prediction fulfilled, even in details. For a full account of its reappearance—as a meteor stream—I refer the reader to my essay on Biela’s comet in ‘Familiar Science Studies.’ ”
In Miller’s “Romance of Astronomy” we read, “Encke’s comet, which possesses the smallest orbit of any connected with our system, is sensibly drawing nearer and nearer to the sun at every revolution.” In Professor Proctor’s “Cometic Mysteries,” the author says, “We hear it stated that the nucleus of a comet is made up of meteoric stones (Professor P. G. Tait says—for unknown reasons—that they resemble ‘paving stones or even bricks’) as confidently as though the earth had at some time passed through the nucleus of a comet, and some of our streets were now paved with stones which had fallen to the earth on such an occasion. As a matter of fact, all that has yet been proved is that meteoric bodies follow in the track (which is very different from the tail) of some known comets, and that probably all comets are followed by trains of meteors. These may have come out of the head or nucleus in some way as yet unexplained; but it is by no means certain that they have done so, and it is by many astronomers regarded as more than doubtful. The most important point to be noticedin the behavior of large comets as they approach the sun is, that usually the side of the coma which lies towards the sun is the scene of intense disturbance. Streams of luminous matter seem to rise continually towards the sun, attaining a certain distance from the head, when, assuming a cloud-like appearance, they seem to form an envelope around the nucleus. This envelope gradually increases its distance from the sun, growing fainter and larger, while within it the process is repeated and a new envelope is formed. This, in turn, ascends from the nucleus, expanding as it does so, while within it a new envelope is formed. Meanwhile the first one formed has grown fainter, perhaps has disappeared. But sometimes the process goes on so rapidly (a day or two sufficing for the formation of a complete new envelope) that several envelopes will be seen at the same time,—the outermost faintest, the innermost most irregular in shape and most varied in brightness, while the envelope or envelopes between are the best developed and most regular. The matter raised up in these envelopes seems to have undergone a certain change of character, causing it no longer to obey the sun’s attractive influence, but to experience a strong repulsive action from him, whereby it is apparently swept away with great rapidity to form the tail. ‘It flows past the nucleus,’ says Dr. Huggins, ‘on all sides, still ever expanding and shooting backward until a tail is formed in the direction opposite to the sun. This tail is usually curved, though sometimes rays or extra tails sensibly straight are also seen.’ ”
In “The Sun as a Perpetual Machine,” Professor Proctor says, “Take, again, the phenomena of comets, which still remain among the greatest of nature’s mysteries. We have reason to believe … that the nucleus of a comet consists of an aggregation of stones similar to meteorites. Adopting this view, and assuming that these stones have absorbed somewhere gases to the amount of six times their volume (taken at atmospheric pressure), we may ask, What will be the effect of such a mass of stones advancing towards the sun at a velocity reaching in perihelion the prodigious rate of three hundred and sixty-six miles per second (as observed in the comet of 1843), being twenty-three times our orbital rate of motion?” Professor Ball says, “One of the most important results of the great shower of 1866 was the demonstration that the swarm of little bodies to which that shower owed its origin was connected with a comet. The swarm was found, in fact, to follow the exact track which the comet pursued around the sun …. Of this connection between the cometary orbits and revolving swarms of meteors many other instances could be cited. I may refer to the remarkable lists published by the British Association, in which, beside the name of the comet or the designation which astronomers had affixed to it, the meteoric swarm with which the comet is associated is also given …. On these grounds it appears to be perfectly certain that the origin of the shooting stars which appear in swarms cannot be disassociated from the origin of the comets by which thoseswarms are accompanied.” The author makes a distinction between such ordinary shooting stars and meteorites, and attributes the appearance of the latter on earth to masses thrown forth from some volcanosomewhere, but this has nothing to do with the special phenomena to be interpreted. It may be said, however, that the presence of olefiant gas as one of the occluded gases in a meteorite (four and fifty-five-hundredths per cent., as stated by Professor Proctor, in his article “The Sun as a Perpetual Machine”), and the remarkable fact, stated in the article “Spectrum Analysis” in Appleton’s Cyclopædia, that, in Winnecke’s comet of 1868, “the bands agree in position with those obtained as the spectrum of carbon, by passing the electric spark through olefiant gas, “would lead one to consider a cometic origin, for this particular meteorite at least, to be highly probable. Professor Ball further says, “There have been several instances in which a comet has approached so close to a planet that the attraction between the two bodies must have had significant influence on the planet, if the cometary mass had been at all comparable with that of the more robust body. The most celebrated instance is presented in the case of Lexell’s comet, which happened to cross the track of Jupiter. The effect upon this body was so overwhelming that it was wrenched from its original path and started afresh along a wholly different track.” The same writer, speaking of the tails of comets, says, “I have no intention to discuss here the vexed question of the tails of comets. I donot now inquire whether the repulsion by which the tail is produced be due to the intense radiation from the sun, or to electricity, or to some other agent. It is sufficient for our present purpose to note that, even if the tails of comets do gravitate towards the sun, the attraction is obscured by a more powerful repulsive force …. Nor do the directions in which the comets move exhibit any conformity; some move round the sun in one direction, some move in the opposite direction. Even the planes which contain the orbits of the comets are totally different from each other. Instead of being inclined at only a very few degrees to their mean position, the planes of the comets hardly follow any common law; they are inclined at all sorts of directions. In no respect do the comets obey those principles which are necessary to prevent constitutional disorder in the planetary system …. Now, all we have hitherto seen with regard to comets tends to show that the masses of comets are extremely small. Attempts have been made to measure them, but have always failed, because the scales in which we have attempted to weigh them have been too coarse to weigh anything of the almost spiritual texture of a comet. It is unnecessary to go as far as some have done, and to say that the weight of a large comet may be only a few pounds or a few ounces. It might be more reasonable to suppose that the weight of a large comet was thousands of tons, though even thousands of tons would be far too small a weight to admit of being measured by the very coarsebalance which is at our disposal.” In the chapter “Visitors from the Sky,” the same author says, “As such a comet in its progress across the heavens passes between us and the stars, those stars are often seen twinkling brilliantly right through the many thousand miles of cometary matter which their rays have to traverse. The lightest haze in our atmosphere would suffice to extinguish the faint gleam of these small stars; indeed, a few feet of mist would have more power of obstructing the stellar light than cometary material scores of thousands of miles thick. It is true that the central portions of many of these comets often exhibit much greater density than is found in the exterior regions; still, in the great majority of such objects there is no opacity, even in the densest part, sufficient to put out a star. In the case of the more splendid bodies of this description, it may be supposed that the matter is somewhat more densely aggregated as well as more voluminous; still, however, it will be remembered that the great comet of 1858 passed over Arcturus, and that the star was seen shining brilliantly, notwithstanding the interposition of a cometary curtain millions of miles in thickness. So far as I know, no case is known in which the nucleus of a really bright and great comet has been witnessed in the act of passage over a considerable star. It would indeed be extremely interesting to ascertain whether in such case the star experienced any considerable diminution in its lustre.”