in this direction. Since, then, we can look so little forward, it appears a good opportunity for looking back and reviewing the actual amount of our knowledge; or rather, selecting a few outlying points of interest for discussion; for the whole subject in all its bearings spreads itself out to a magnitude that perhaps might be little anticipated; and had we the ability to lead the way, we doubt whether our readers could in fairness be expected to persevere in following us through such an exploration. For example, what may be called the literature of comets has alone attained a disheartening magnitude. To say nothing of the numerous monographs of celebrated comets which marked the awakening of astronomy, or treatises such as those of Kepler and Hevel, which gave a more general view of the subject, all of which materials are valuable, even now, in proportion to the fidelity or sagacity of their authors-we have only to turn to the two folio volumes of the Socinian minister Stanislaus Lubienietzki, whose troubled and miserable life, together with those of two of his daughters, was cut short by poison in 1675, to see how much might be said, even at that early period, and comparatively to how little purpose. Or, if we would form an idea of the field over which cometary information is sown broadcast, we shall find that the indefatigable and trusty Pingré, merit was fully compensated to him by his very favorable circumstances. Far smaller in bulk than the Donati, he came right up over the sun with a more vivid and fiery blaze; his very aspect seemed to show his threatening nearness, and the comparatively feeble diffusion of his tresses might have told us-but that none of us knew at the moment how to interpret their language-that they were closely impending over our heads, if not actually enfolding us in their mazes, and penetrating the very air we were breathing. It seems now an established fact, that we have either traversed bodily the line of that glorious comet's train, or at least have been in such immediate proximity to its sweep, that it is scarcely conceivable that the whole of its materials should have traveled past us. It was a wonderful conjuncture. Such events may have frequently taken place in preastronomical ages, but no record of them, worthy of the name, remains; and we have been told, upon good authority, that the tails of comets were, in 1819, 1823, and 1826, directed toward the earth; but they, again, were too short to have reached us while, on the late occasion, the length of the streams, as they were lifted off our atmosphere, showed plainly that they had passed by us, and far beyond us, away into illimitable space. And now the event has actually happened which was alluded to in our former dissertation as at any rate possible-that in order to form as complete a catanear appulse which, it was supposed, might afford an unequivocal solution of the question of cometary influence; and here we are, proceeding as steadily and quietly as ever in our orbit, and as far as ever at least as regards any positive evidence from any kind of additional information. The comet has come and gone, never to be again beheld by any one now living upon the face of the earth; and we know scarcely any thing more about it than before. It is not only a present, but a prospective disappointment. Generations may pass away, as they have passed, without the record of an equally close approach; and unless some new means of research should unexpectedly be offered to us, or some known mode of investigation may be found capable of a new application, it seems probable that, whatever may be the case with our posterity, we, at least, have reached the limit of our discoveries logue as possible, consulted upward of six hundred authorities-the greater part, of course, annalists of former days. At least sixty-five treatises must have been published relating more or less to the comet of 1680 alone, since that amount is already collected in the noble astronomical library of the Czar's observatory at Poulkowa, near St. Petersburg; and the three hundred and eighty-two works on the subject of comets not long ago to be found there, must in these days be a continually increasing quantity. Or, again, it would be no trifling matter to trace all the absurd superstitions which have been connected with these phenomena from the earliest ages. How they originally came to be aspersed as ominous of evil, or why that impression should have been so widely and so long entertained, it might be difficult to say. It is remarkable that no mention is made of comets in Holy Scripture, though the imagery of prophetic inspiration seems well calculated for their introduction; possibly the object of that silence might be to discourage the dread of portents which would naturally attend upon heathen idolatries : "Learn not the way of the heathen; And be not dismayed at the signs of heaven; "Thus threatening comets, when by night. they rise Shoot sanguine streams, and sadden all the skies." Yet, if we may digress a moment, we have here a specimen of the difficulty of translation, even in the hands of a master. The idea of rising by night has no place in Virgil, and is worthless in point of effect: while the exceedingly beautiful contrast implied in the "liquida nocte" is unrendered in the English version. The state of knowledge, and that of society, in succeeding ages, were little calculated to disperse these apprehensions, and the sciless to remove them than sanguine persons have expected. In France, in 1773, the terror was unbounded, from the mere announcement of a very harmless memoir by Lalande, on Comets which may approach the Earth: it has been even said that there were several cases in which life was sacrificed to the fear of death. In 1832, a similar alarm roused up the same impressible nation to an extent which called forth government interference in the shape of Arago's well-known treatise, great part of which is composed of grave replies to the silliest of inquiries. In our comfort felt a few years ago, in conseown quieter country there was some dis Among the Greeks such apprehensions were general. Yet Aristotle, in assigning a physical cause for the effects of comets on our atmosphere, seems not to have shared the popular opinion as to their political signification; an instance of mod-entific progress of later days has done eration or caution the more to be wondered at, since one of those coïncidences took place in his youth which in every age have alarmed the ignorant, and sometimes staggered the better informed. In the year 373 (or 371) B.C., a tremendous comet which was called the "Beam" (or rafter) and the "Way," from its aspect, and whose tail resembled a long avenue of trees, preceded or attended a fearful earthquake, which overwhelmed the cities of Helice and Bura in the gulf since named from Lepanto, and seemed to herald to the Spartans their bloody overthrow on the field of Leuctra, and the departure of a supremacy of five hundred years. The Romans, as might have been expect-quence of the anticipated approach of ed, inherited the prejudice, as it would be easy to show by a whole string of quotations, but we will only cite those fine lines of Lucan: that great deceiver, the Comet of Charles V.: and even last summer we have been told that the journalists of Paris received official instructions to be sparing in their references to the wonder in the northern heavens, and never to allude to there being such a thing as a comet called "Cæsar's," or to the name of the Emperor Charles V. So much for the boasted "march of intellect" in "the nineteenth century." However, some allowances must be made. Every body can not have a scientific education; and prejudices are slow in departure. There certainly have been singular coïncidences, even in this nineteenth century: the comet of 1807 was followed by the French occupation of Spain; the pallid plume of 1811, by the most disastrous re1854, by the war of Sebastopol; the Dotreat from Moscow; the fiery saber of nati, by that in Italy; and these would naturally be more noticed than the ab sence of any adequate sequel to the greater comet of 1843. No doubt it is one of the indirect benefits of astronomy that it tends to remove unreasonable ap-humor, hatred, conspiracy, and war; and prehensions; but if this were all the re- all persons of delicate or melancholic temsult, poor indeed must be the study that perament being most subject to such incould yield no nobler fruit; and one fluences, it would of course follow that scarcely knows whether to feel most pity princes and rulers, who are naturally of or surprise in reading, at the close of La- such a constitution, would be especial sufplace's Système du Monde, that while ferers. It would be easy to enlarge the modern discoveries have rendered im- list of the absurdities of what Hooke calls portant services to navigation and astron worm eaten antiquity," but to little puromy, "their great benefit has been the poses; and we must not forget that the having dissipated the alarms occasioned elder Pythagoreans, and Apollonius of by extraordinary celestial phenomena, and Myndus, entertained far more sensible nodestroyed the errors springing from the tions upon the subject; and the prophetic ignorance of our true relation with nature words of Seneca would well deserve repe- errors so much the more fatal, as social tition at length, had we room for them; order can only rest on the basis of those he ought never to be forgotten, who relations." And was this all that so gift- said: "The time will come when our posed an intellect could perceive in the study terity will wonder at our ignorance of of the handiwork of God? Most lame things so plain." At a later period light and impotent conclusion! The youthful broke in rapidly upon the dark regions of shepherd of Bethlehem Ephrata, in all his cometomancy; the method of parallaxscientific ignorance, was by far the better or, in other words, of finding the distance philosopher of the two! of an object from its apparent change of place as viewed from different stationsthough it had but partial success as applied by Regiomontanus in 1472, was a spell of power in 1577, in the hands of a greater master, Tycho Brahe: thenceforth not only was our atmosphere forever exorcised from bearing the blame of such ill-omened productions, but the solid Ptolemæan spheres were shattered by the blow, and comets went through in triumph, and the fertile and exuberant genius of Kepler expatiated in the opening and followed them into illimitable space. It is true that his vivid fancy here as else. where, led him into speculations which have been sneered at by men every way his inferiors. He not only supposed that comets were created to occupy the great solitudes of the heavens, as fishes were made to inhabit the sea, and that the celestial hights are as full of the one as the marine depths of the other-and there he was not far wrong, for a moderate computation shows that about four thousand comets have probably traversed our system since the Christian era-but he assigned superior intelligences as their conductors, and on purpose to explain the tempests and inundations which they preceded, attributed to the earth a vital or animal faculty, that, together with the spirit of all mortal creatures, is dismayed at any portent in the heavens. These indeed are dreams. But they are the dreams of a magnificent intellect the unmeasured and unbounded outbreaks of But, were this branch of our subject exhausted, another awaits us-the various hypotheses which have been framed at different times to explain the appearance of comets, or to account for the evil effects for which they have been made answerable. But there would be little to interest us in the ancient ideas of their being reflections of the solar rays in the mirror of the firmament, or the result of the conjunction of planets, or in the more rational guesses that they were lights shut up in lanterns of mist, or lofty clouds illuminated or inflamed by the rays of the sun, moon, or stars. Democritus was said to have gone off in quite a different direction, and beheld in them the translation of heroic souls to a higher region; and Augustus, when a comet appeared during the funeral games of Julius Cæsar, seems to have been willing to cherish a similar notion, and in consequence affixed a star to the forehead of his great predecessor's statue. The theory of Aristotle, that comets, being the combustion of hot and dry terrestrial exhalations in the highest region of the atmosphere, might be followed by winds and drought, was not wide enough for the popular belief; and his followers accordingly attempted to improve upon it by asserting that, in ascending to form the comet, and descending again in the shape of ashes, these hot, sulphureous, and volcanic exhalations would so poison the air through which they passed as to produce pestilence, ill that enthusiasm which is so often the handmaid of true and living power. But dreams visit likewise minds of an inferior order; and we should be unworthily detained were we to recount the visions of various speculators down to the present time, as well of those who looked upon comets as places of torment, as of those who fancied them the most suitable observatories for the study of creation. Celebrated as they were in their day, the lucubrations of the eccentric Whiston, as to the Comet of the Deluge, and that of the future Judgment, are now admitted to be of little more value. Another branch awaits_us-the history of the events and anecdotes connected with these phenomena, which would form a curious collection: such as the repartee by which Vespasian would fain have averted the omen of his death, as though the "hairy star" concerned much less his own bald-headed self than the long-haired King of Parthia; the far no bler remark of Charlemagne to Eginhard before his own decease, when the latter would have dissuaded him from apprehen sion, "We ought to fear nothing but Him who is the Maker both of us and of this star; but we are bound to praise his mercy, who, sinners as we are, vouchsafes to admonish our inertness by such prognostications;" the representation in the Bayeux tapestry of the Comet of the Norman Conquest, (the same with that of Halley;) the church-bell still rung at noon in Roman Catholic countries, in consequence of the terror of Pope Calixtus III. at another return of that comet in 1456; and the arrogant yet somehow sublime exclamation of Giovanni Galeazzo Visconti, first Duke of Milan, on occasion of the wonderful comet of 1402: "On dit," says Pingré, "que galéas l'ayant vue, désespéra de sa vie car, dit-il, notre père, au lit de la mort, nous a révélé que selon le témoignage de tous les astrologues, au temps de notre mort, une semblable étoile devoit paroître durant huit jours . . . ses amis l'aidèrent à sortir de son lit, il vit la comète et s'écria, Je rends grâces à mon Dieu, de ce qu'il a voulu que ma mort fût annoncée aux hommes par ce signe céleste." He died shortly after. We might mention, too, the curious "comet-dollar" still worn as a charm, which was struck in Germany on occasion of the comet of 1664, with the inscription: "O Lord, punish us not in thine anger." But we can only just touch these things. We have a long road before us-well for our readers if they find it not a weary one. We have been merely sketching a few preliminaries; not a word has yet been said as to the real phenomena of comets; and to this part of our undertaking we must now at once address ourselves. Every one knows that comets in general consist of a head and a tail, and is aware at which end the nucleus is to be looked for. But if we make pretensions to accuracy, we must begin further back, and observe that many comets have neither tail or nucleus, being in fact mere circular patches of faint mist, undistinguishable except by their motion, from the numerous class of inconspicuous nebulæ. As we ascend the scale, the center is found to become more dense, and in certain cases to put on a granulated and even a sparkling aspect, like that of a nebula beginning to yield up its starry components to optical power. Through various stages of increasing concentration we thus arrive at the fully-developed specimen, and then the nucleus-bearing head is almost sure to throw out some proportion of tail. In fact, the more brilliant comets seem formed, with many individual peculiarities, upon much the same plan, consisting of a nucleus, a coma, rays or sectors, envelopes, and a tail. We propose to give some account of these in order. I. The Nucleus.-All the larger comets, viewed without a telescope, or with only a low power, bear in the midst of the head the likeness of a star. Higher magnifiers, while they enlarge, almost invariably confuse this stellar appearance, and give it the character of a condensed center rather than of a defined planetary disk. In 1807 and 1811, Herschel I. detected a minute and scarcely measurable point, which in the latter case was not in the center of the greatest brightness. Schröter, on the other hand, gave the name of nucleus to the whole interior of those heads, which, though without a defined edge, exhibited in one part a sudden increase of brilliancy. In general, there is a small but measurable central speck, sufficiently distinct from the surrounding haze, yet by no means bounded, like a planet, by a sharp outline. Donati's Comet, in 1858, and our recent visitor, furnished beautiful examples of such nu clei: in splendor, however, they have been far surpassed on former occasions. was noticed in 1861, and possibly this mysterious vailing of the true nucleus may be a general characteristic. Herschel I., in 1807 and 1811, seems to have had a better view of what he calls the Nuclei in general are of a circular form, but an elliptical shape has been in some instances ascribed to them. Every thing seems to indicate that they have no axis of rotation. The Donati was never visible to the naked eye in the day-time; the late comet was so seen only by one observer (Mr. Lowe) on the evening of June thirtieth; but there is evidence more or less satisfactory that the comets of the following years" planetary bodies" of those comets, have all dared to show their faces in the which, according to him, measured only presence of the sun :--B.C. 43, (Cæsar's ;) about five hundred and thirty-eight and A. D. 975, 1106, 1269? 1402, 1472, 1500, four hundred and twenty-eight miles. 1532, 1577, 1618, 1744, 1843. Of these, in 1106 a star was visible at the distance of a foot and a half from the sun, from the third to the ninth hour, on February fourth or fifth, appearing two or three days later as a great comet: Pingré has assigned two such to 1402; but we are inclined to think that one has been multiplied by the inaccuracy of early chronicles; it was the star of Galeazzo Visconti, and did not dread even the vicinity of the solar blaze: that of 1577 was seen by Tycho when he was fishing with his servants a little before sunset; that of 1744, the "Pretender's Comet," was of surpassing splendor, being seen at its perihelion even at mid-day with the naked eye. But all, excepting perhaps that of 1106, must yield the palm to the glorious visitant of 1843. It had just all but grazed the sun's surface, when on February twenty-eighth it was seen in various parts of the world as a star, or a white cloud, confronting his dazzling orb all day long. Amici at Parma measured its distance, and found it only 1° 23', not three times the diameter of the sun, from his limb: of all the planets, Venus alone presumes to show herself at noon, but only when she is far removed and upon a dark-blue sky; a tenfold splendor would be requisite before she could be visible so near the sun: the accuracy of modern times was needed, and fortunately was at hand, to establish so wonderful a phenomenon. The nuclei of comets appear subject to great fluctuations in apparent brightness and real magnitude. Donati varied mate rially from night to night: the American observers made its diameter fifteen hundred and sixty miles on October second; on the fifth, only four hundred miles; the next night it was double that size, and on the eighth eleven hundred and twenty miles. These vast changes seemed dependent upon successive disengagements from its surface of separate clouds of lu minous matter; so that it was difficult to say when, or whether in any case, it was seen free and clear. Something similar II. The Coma.-This term is applied to the exterior light of the head, which always melts away imperceptibly into the surrounding sky. High magnifiers extinguish it in their limited fields, offering so little contrast with the blue heavens. Its form is usually spherical, though some irregularity was recorded in Donati by several observers; its extent is sometimes very great: the coma of the curious "lost comet" of 1770, or "comet of Lexell," (from the name of its investigator,) was spread over a space of no less than two and one third degrees, or more than five times the size of the moon; but this was owing to its proximity, as at that time the head had made the nearest of all such recorded appulses to the earth, being only six times the moon's distance from us: the true diameter was fifty-nine thousand miles. But that of 1811, though from its distance subtending a less angle to the eye, surpassed it far, and was in fact the most voluminous body in the solar system; its diameter, variously given from its indistinct boundary amounting to considerably upward of a million of milesmore by one quarter than the whole globe of the sun, and capable of including the moon's orbit twice over! Yet, with this wonderful extent, its weight was utterly insignificant possibly, as Herschel II. says of the tail, only a few pounds or even ounces! It has been observed that the coma of some, and possibly it may be true of all comets, diminishes in its approach to the sun, sometimes in an extraordinary degree. Kepler has the credit of this discovery, of which much has been said by Valz and others in our own day without any very definite conclusion: it is probably a fact, but allowance must be made for the effect of a brighter background. III. The Rays, Jets, Fans, or Sectors. |