Elevation when first seen, over55 miles" at the time of its explosion20 "Inclination of its path to the horizon20° or 25°Velocity per second, about20 miles,or equal to that of the earth's orbital motion.
"This example," says Professor Newton, "affords the strongest proof that the detonating and stone-producing meteors are phenomena not essentially unlike."
(25.) 1868,January30.—It is obviously a matter of much importance that the composition and general characteristics of aerolites, together with the phenomena attending their fall, should be carefully noted; as such facts have a direct bearing on the theory of their origin. In this regard the memoirs of Professors J. G. Galle, of Breslau, and G. vom Rath, of Bonn, on a meteoric fall which occurred at Pultusk, Poland, on the 30th of January, 1868, have more than ordinary interest. These memoirs establish the fact that the aerolites of the Pultusk showerentered our atmosphereas a swarm or cluster of distinct meteoric masses. It is shown, moreover, by Dr. Galle that this meteor-group had a proper motion when it entered the solar system of at least from 4½ to 7 miles per second.
The foregoing list contains but a small proportion of the meteoric stones whose fall has been actually observed. But, besides these, other masses have been found so closely similar in structure to aerolites whose descent has been witnessed, as to leaveno doubt in regard to their origin. One of these is a mass of iron and nickel, weighing 1680 pounds, found by the traveler Pallas, in 1749, at Abakansk, in Siberia. This immense aerolite may be seen in the Imperial Museum at St. Petersburg. On the plain of Otumpa, in Buenos Ayres, is a meteoric mass 7½ feet in length, partly buried in the ground. Its estimated weight is about 16 tons. A specimen of this stone, weighing 1400 pounds, has been removed and deposited in one of the rooms of the British Museum. A similar block, of meteoric origin, weighing more than six tons, was discovered some years since in the province of Bahia, in Brazil.
General Remarks.
1. A Committee on Luminous Meteors was appointed several years since by the British Association for the Advancement of Science. This committee, consisting at present of James Glaisher, F.R.S., Robert P. Greg, F.R.S., Alexander S. Herschel, F.R.A.S., and Charles Brooke, F.R.S., report from year to year not only their own observations on aerolites, fire-balls, and falling stars, but also such facts bearing upon the subject as can be derived from other sources. An analysis of these reports justifies the conclusion that meteoric stone-falls, like star-showers, occur with greater frequency than usual on or about particular days. These epochs, established with more or less certainty, are the following:
(a.)January4th.(b.)"16th.(c.)"29th.(d.)February10th.(e.)"15th—18th.(f.)March6th.(g.)"12th.(h.)April1st.(i.)"10th—14th.(j.)May8th—9th.(k.)"13th—14th.(l.)"17th—19th.(m.)June3d.(n.)"9th.(o.)"12th.(p.)"16th.(q.)July3d—4th.(r.)"14th—17th.(s.)August5th—7th.(t.)"11th.(u.)September4th—10th.(v.)October13th.(w.)November5th.(x.)"12th—13th.(y.)"27th—30th.(z.)December5th.(z´.)"8th—14th.(z´´.)"27th.
2. It is worthy of remark that no new elements have been found in meteoric stones. Humboldt, in his "Cosmos," called attention to this interesting fact. "I would ask," he remarks, "why the elementary substances that compose one group of cosmical bodies, or one planetary system, may not in a great measure be identical? Why should we not adopt this view, since we may conjecture that those planetary bodies, like all the larger or smaller agglomerated masses revolving round the sun, have been thrown off from the once far more expanded solar atmosphere, and have been formed from vaporous rings describing their orbits round the central body?"
3. But while aerolites contain no elements but such as are found in the earth's crust, the manner in which these elements are combined and arranged is so peculiar that a skillful mineralogist will readily distinguish them from terrestrial substances.
4. Of the eighteen or nineteen elements hitherto observed in meteoric stones, iron is found in the greatest abundance. The specific gravities vary from 1.94 to 7.901: the former being that of the stone ofAlais; the latter that of the meteorite of Wayne county, Ohio, described by Professor J. L. Smith inSilliman's Journalfor November, 1864, p. 385.
5. The average number of aerolitic falls in a year was estimated by Schreibers at 700. Baron Reichenbach, however, after a discussion of the data at hand, makes the number much larger. He regards the probable annual average for the entire surface of the earth as not less than 4500. This would give twelve daily falls. They are of every variety as to magnitude, from a weight of less than a single ounce to over fifteen tons. The baron even suspects the meteoric origin of large masses of dolerite which all former geologists had considered native to our planet.
6. An analysis of any extensive table of meteorites and fire-balls proves that a greater number of aerolitic falls have been observed during the months of June and July, when the earth is near its aphelion, than in December and January, when near its perihelion. It is found, however, that the reverse is true in regard to bolides, or fire-balls. These facts are susceptible of an obvious explanation. The fall of meteoric stones would be more likely to escape observation by night than by day, on account of the relatively small number of observers. But the days are shortest when the earth is in perihelion, and longest when in aphelion; the ratio of their lengths being nearly equal to that of the corresponding numbers of aerolitic falls. On the other hand, it is obvious that fire-balls, unless very large, would not be visible during the day. Theobservednumber will therefore be greatest when the nights are longest; that is, when the earth is near its perihelion. This, it will be found, is precisely in accordance with observation.
Although shooting-stars have doubtless been observed in all ages of the world, it is only within the last half century that they have attracted the special attention of scientific men. A few efforts had been made to determine the height of such meteors, but the first general interest in the subject was excited by the brilliant meteoric display of November 13, 1833. This shower of fire can never be forgotten by those who witnessed it. The meteors were observed from the West Indies to British America, and from 60° to 100° west longitude from Greenwich. As early as 10 o'clock on the evening of the 12th shooting-stars were observed with unusual frequency; their motions being generally westward. Soon after midnight their numbers became so extraordinary as to attract the attention of all who happened to be in the open air. The meteors, however, became more and more numerous till 4, or half past 4, o'clock; and the fall did not entirely cease till ten minutes before sunrise. From 2 to 6 o'clock the numbers were so great as to defy all efforts at counting them; while their brilliancy was such that persons sleeping in rooms with uncurtained windows were aroused by their light. Themeteors varied in apparent magnitude from the smallest visible points to fire-balls equaling the moon in diameter. Occasionally one of the larger class would separate into several parts, and in some instances a luminous train remained visible for three or four minutes. No sound whatever accompanied the display. It was noticed by many observers that all the meteors diverged from a point near the starGamma Leonis; in other words, their paths if traced backward would intersect each other at a particular locality in the constellation Leo. In some parts of the country the inhabitants were completely terror-stricken by the magnificence of the display. In the afternoon of the day on which the shower occurred the writer met with an illiterate farmer who, after describing the phenomena as witnessed by himself, remarked that "the stars continued to fall till none were left," and added, "I am anxious to see how the heavens will appear this evening; I believe we shall see no more stars." A gentleman of South Carolina described the effect on the negroes of his plantation as follows:—"I was suddenly awakened by the most distressing cries that ever fell on my ears. Shrieks of horror and cries for mercy I could hear from most of the negroes of the three plantations, amounting in all to about 600 or 800. While earnestly listening for the cause I heard a faint voice near the door, calling my name. I arose, and, taking my sword, stood at the door. At this moment I heard the same voice still beseeching me to arise, and saying, 'O my God, the world is on fire!' I then opened the door, and it is difficult to say which excited me the most,—the awfulness of thescene, or the distressed cries of the negroes. Upwards of a hundred lay prostrate on the ground,—some speechless, and some with the bitterest cries, but with their hands raised, imploring God to save the world and them. The scene was truly awful; for never did rain fall much thicker than the meteors fell towards the earth; east, west, north, and south, it was the same."
At the time of this wonderful meteoric display Captain Hammond, of the shipRestitution, had just arrived at Salem, Massachusetts, where he observed the phenomenon from midnight till daylight. He recollected with astonishment that precisely one year before, viz., on the 13th of November, 1832, he had observed a similar appearance (although the meteors were less numerous) at Mocha, in Arabia. It was found, moreover, as a further and most remarkable coincidence, that an extraordinary fall of meteors had been witnessed on the 12th of November, 1799. This was seen and described by Andrew Ellicott, Esq., who was then at sea near Cape Florida. It was also observed by Humboldt and Bonpland, in Cumana, South America. Baron Humboldt's description of the shower is as follows:—"From half after two, the most extraordinary luminous meteors were seen toward the east. Thousands of bolides and falling stars succeeded each other during four hours. They filled a space in the sky extending from the true east 30° toward the north and south. In an amplitude of 60° the meteors were seen to rise above the horizon at E.N.E. and at E., describe arcs more or less extended, and fall toward the south, after having followed the direction of the meridian. Some of them attained a height of 40°, and all exceeded 25° or 30°. Mr. Bonpland relates, that from the beginning of the phenomenon there was not a space in the firmament equal in extent to three diameters of the moon, that was not filled at every instant with bolides and falling stars. The Guaiqueries in the Indian suburb came out and asserted that the firework had begun at one o'clock. The phenomenon ceased by degrees after four o'clock, and the bolides and falling stars became less frequent; but we still distinguished some toward the northeast a quarter of an hour after sunrise."
This wonderful correspondence of dates excited a very lively interest throughout the scientific world. It was inferred that a recurrence of the phenomenon might be expected, and accordingly arrangements were made for systematic observations on the 12th, 13th, and 14th of November. The periodicity of the shower was thus, in a very short time, placed wholly beyond question. The facts in regard to the phenomena of November 13, 1833, were collected and discussed by Olmsted, Twining, and other astronomers. The inquiry, however, very naturally arose whether any trace of the same meteoric group could be found in ancient times. To determine this question many old historical records were ransacked by the indefatigable scientist, Edward C. Herrick, in our own country, and by Arago, Quetelet, and others, in Europe. These examinations led to the discovery of ten undoubted returns of the November shower previous to that of 1799. The descriptions of these former meteoric falls aregiven by Professor H. A. Newton in theAmerican Journal of Science, for May, 1864. They occurred in the years 902, 931, 934, 1002, 1101, 1202, 1366, 1533, 1602, and 1698. Historians represent the meteors ofA.D.902 as innumerable, and as moving like rain in all directions. The exhibition of 1202 was scarcely less magnificent. "On the last day of Muharrem," says a writer of that period, "stars shot hither and thither in the heavens, eastward and westward, and flew against one another like a scattering swarm of locusts, to the right and left; this phenomenon lasted until daybreak; people were thrown into consternation, and cried to God the Most High with confused clamor." The shower of 1366 is thus described in a Portuguese chronicle, quoted by Humboldt: "In the year 1366, twenty-two days of the month of October being past, three months before the death of the king, Don Pedro (of Portugal), there was in the heavens a movement of stars such as men never before saw or heard of. At midnight, and for some time after, all the stars moved from the east to the west; and after being collected together, they began to move, some in one direction and others in another. And afterward they fell from the sky in such numbers, and so thickly together, that as they descended low in the air they seemed large and fiery, and the sky and the air seemed to be in flames, and even the earth appeared as if ready to take fire. That portion of the sky where there were no stars seemed to be divided into many parts, and this lasted for a long time."
The Showers of 1866-9.
The fact that all great displays of the November meteors have taken place at intervals of 33 or 34 years, or some multiple of that period, had led to a general expectation of a brilliant shower in 1866. In this country, however, the public curiosity was much disappointed.[22]The numbers seen were greater than on ordinary nights, but not such as would have attracted any special attention. The greatest number recorded at any one station was seen at New Haven by Professor Newton. On the night of the 12th 694 were counted in five hours and twenty minutes, and on the following night, 881 in five hours. A more brilliant display was, however, witnessed in Europe. Meteors began to appear in unusual frequency about 11 o'clock on the night of the 13th, and their numbers continued to increase with great rapidity for more than two hours; the maximum being reached a little after 1 o'clock. A writer in Edinburgh, Scotland, thus describes the phenomenon as observed at that city:—"Standing on the Calton Hill, and looking westward,—with the observatory shutting out the lights of Princes Street,—it was easy for the eye to delude the imagination into fancying some distant enemy bombarding Edinburgh Castle from long range; and the occasional cessation of the shower for a fewseconds, only to break out again with more numerous and more brilliant drops of fire, served to countenance this fancy. Again, turning eastward, it was possible now and then to catch broken glimpses of the train of one of the meteors through the grim dark pillars of that ruin of most successful manufacture, the National Monument; and in fact from no point in or out of the city was it possible to watch the strange rain of stars, pervading as it did all points of the heavens, without pleased interest and a kindling of the imagination, and often a touch of deeper feeling that bordered on awe." At London about 1 o'clock a single observer counted 200 in two minutes. The whole number seen at Greenwich was 8485. The shower was also observed in different countries on the continent.
In 1867 the display was generally observed throughout the United States. From the able and interesting reports of Commodore Sands and Professors Newcomb, Harkness, and Eastman, we derive the following facts in regard to the shower as seen at Washington, D. C.:
Commencement1h.0m.A.M.Nov. 14.Maximum4 20" "End5 0" "Number of meteors per hour at maximum3000Mean height on first appearance75 miles." " on disappearance55 "Position of radiant, R. A. 151°, Decl. 22½°.
The shower of 1868 was in some respects quite remarkable, though the number of meteors was less than in 1866 or 1867. At New Haven the fall commenced about midnight, and from 2 o'clock till daybreak over 5000 meteors were counted. The time of maximum could not be accurately determined, as no decrease in the numbers was observable till dawn. The display was also witnessed in England and in Cape Colony, South Africa. The times of maxima in these countries differed so materially as to indicate a decided stratification of the meteoric stream. The entire depth, moreover, where crossed by the earth in 1868, was much greater than at the part traversed either in 1866 or 1867.
In 1869 the shower was observed at Port Saïd, Lower Egypt, by G. L. Tupman, Esq.; in Florida, U. S., by Commander William Gibson, U.S.N.; and at Santa Barbara, California, by Mr. G. Davidson and Mrs. E. Davidson. The first observed 112 meteors in 1h. 54m., from 2h. 30m. to 4h. 24m., Alexandria mean time; the numbers during this interval being nearly equal, though slightly decreasing. Throughout the morning (November 14) the sky was only partly clear. The two observers at Santa Barbara saw 556 in 2h. 25m., ending at 3h. 43m.A.M.In Florida also the display was quite brilliant, though inferior to that of 1868. It should be remarked that the morning in many parts of the United States was cloudy. No considerable number of the meteors of this stream has been observed in any part of the world since 1869.
Discussion of the Phenomena.
Since the memorable display of November 13, 1833, the phenomena of shooting-stars have been observed and discussed with a very lively interest.Among the first laborers in this department of research the names of Olmsted, Herrick, and Twining must ever hold a conspicuous place. The fact that the position of the radiant point did not change with the earth's rotation at once placed the cosmical origin of the meteors wholly beyond question. The theory of a ring of nebulous matter revolving round the sun in an elliptic orbit—a theory somewhat different from that proposed by Olmsted—was found to afford a simple and satisfactory explanation of the phenomena. This hypothesis of an eccentric stream of meteors intersecting the earth's orbit was adopted by Humboldt, Arago, and others, shortly after the occurrence of the meteoric shower of 1833.
A few years previous to the display of 1866 it was shown by Professor Newton, of Yale College, that the distribution of meteoric matter around the ring or orbit is far from uniform; that the motion is retrograde; that the node of the orbit has an annual forward motion of 102´´.6 with respect to the equinox, or of 52´´.4 with respect to the fixed stars; that the periodic time must be limited to five accurately determined periods, viz.: 180.05 days, 185.54 days, 354.62 days, 376.5 days, or 33.25 years; and that the inclination of the orbit to the ecliptic is about 17°. Professor Newton, for reasons assigned, regarded the third period named as the most probable. He remarked, however, that by computing the secular motion of the node for each periodic time, and comparing the result with the known precession, it was possible to determine which of the five periods is the correct one.
For the application of this crucial test,—a problem of more than ordinary interest,—we are indebted to Professor J. C. Adams, of Cambridge, England. By an elegant analysis it was first shown that for either of the first four periods designated by Professor Newton, the annual motion of the node, resulting from planetary perturbation, would be considerably less than one half of the observed motion. It only remained, therefore, to examine whether the period of 33¼ years would give a motion of the node corresponding with observation. Professor Adams found that in this time the longitude of the node is increased 20´ by the action of Jupiter, 7´ by the action of Saturn, and 1´ by that of Uranus. The effect of the other planets is scarcely perceptible. Thecalculatedmotion in 33¼ years is therefore 28´. Theobservedmotion in the same time, according to Professor Newton, as previously stated, is 29´. This remarkable accordance was at once accepted by astronomers as satisfactory evidence that the period is about 33.25 years.
Having determined the periodic time, the mean distance, or semi-axis major, is found by Kepler's third law to be 10.34. The aphelion is consequently situated at a comparatively short distance beyond the orbit of Uranus. The orbit is represented in Fig. 4.
Fig. 4.Fig. 4.
Fig. 4.
It was stated at the close of Chapter VI. that shooting-stars are the dissevered fragments of cometic matter, which, penetrating our atmosphere, are rendered luminous by the resistance so encountered. The discovery that comets and meteors are actually moving in the same orbits was first announced by Signor Schiaparelli in 1867. Thecoincidence of the orbits of Tempel's comet[23]as computed by Dr. Oppolzer, and the meteors of November 14 as determined by Schiaparelli, is too close to be regarded as merely accidental. These elements are as follows:
Nov. Meteors.Tempel's Comet.Perihelion passageNov. 10.092, 1866.Jan. 11.160, 1866.Passage of descending nodeNov. 13.576,Longitude of perihelion56° 26´60° 28´Longitude of ascending node231° 28´231° 26´Inclination17° 44´17° 18´Perihelion distance0.98730.9765Eccentricity0.90460.9054Semi-major axis10.340010.3240Periodic time33.2500y.33.1760y.MotionRetrograde.Retrograde.
The fact is thus obvious that the meteors of November 14 are the products of the comet's gradual dissolution. It has been stated that the comets of 1366 and 1866 are probably identical. The interval indicates a period of 33.283 years—greater by 39 days than that found by Oppolzer. With this value of the periodic time and the known secular variation of the node it is found that the comet and Uranus were in close proximity about the beginning of the year 547B.C.It is therefore not improbable that the former was then thrown into its present orbit by the attraction of the latter. The celebrated Leverrier designated the year 126 of our era as the probable epoch of the comet's entrance into our system. This date, however, is incompatible with the period here adopted. It is worthy of remark, moreover, as bearing on this question, that the extension of the cluster in the tenth century, as indicated by the showers of 902, 931, and 934, was too great to have been effected in so short a period as 800 years.
With the period of 33.283 years it is easy to find that the comet will make a near approach to the earth about the 16th or 17th of November, 1965, and to Uranus in 1983. At one of these epochs the cometary orbit will probably undergo considerable transformation.
We have seen that the comet of 1866, and also the meteoroids following in its path, have their perihelion at the orbit of the earth, and their aphelion at the orbit of Uranus. Both planets, therefore, at each encounter with the current not only appropriate a portion of the meteoric matter, but entirely change the orbits of many meteoroids. In regard to the devastation produced by the earth in passing through the cluster, it is sufficient to state that, according to Weiss, the meteor orbits resulting from the disturbance will have all possible periods from 21 months to 390 years. It may be regarded, therefore, as evidence of the recent[24]introduction of this meteor-stream into the solar system that the comet of 1866, which constitutes a part of the cluster, has not been deflected from the meteoric orbit by either the earth or Uranus.
The Meteors of August7-11.—Muschenbroek, in his "Introduction to Natural Philosophy," published in 1762, stated as the result of his own observations that shooting-stars are more abundant in August than in any other part of the year. The fact, however, that a maximum occurs on the 9th or 10th of the month was first shown by Quetelet in 1835. Since that time the shower has been regularly observed both in Europe and America; the number of meteors at the maximum sometimes amounting to 160 per hour. Their tracks when produced backward intersect each other at a particular point in the constellation Perseus.
Of the 315 meteoric displays given in Quetelet's catalogue, 63 belong to the August epoch. Their dates up to the commencement of the present century are as follows:
1.A.D.811,July25th.2.820,"25th-30th.3.824,"26th-28th.4.830,"26th.5.833,"27th.6.835,"26th.7.841,"25th-30th.8.924,"27th-30th.9.925,"27th-30th.10.926,"27th-30th.11.933,"25th-30th.12.1243,Aug.2d.13.1451,"7th.14.1709,"8th.15.1779,"9th-10th.16.1781,"8th.17.1784,"6th-9th.18.1789,"10th.19.1798,"9th.20.1799,"9th-10th.21.1800,"10th.
As the earth is about five days in crossing the ring, its breadth in some parts cannot be less than 8,000,000 miles.
In 1866 Professor Schiaparelli, on computing the orbit of this meteoric stream, noticed the remarkable agreement of its elements with those of Swift's or Tuttle's comet[25](1862, III.), as computed by Dr. Oppolzer. These coincidences are exhibited in the following table:
Meteors of August 10.Comet III. of 1862.Longitude of perihelion343° 38´344° 41´Ascending node138° 16´137° 27´Inclination63° 3´66° 25´Perihelion distance0.96430.9626.Period105 years (?)121.5 years.MotionRetrograde.Retrograde.
It appears, therefore, that the third comet of 1862 is a part of the meteoric stream whose orbit is crossed by the earth on the 10th of August.
The characteristics of different meteor-zones afford interesting indications in regard to their relative age,the magnitude and composition of their corpuscles, etc. Thus, if we compare the streams of August 10 and November 14, we shall find that the former probably entered our system at a comparatively remote epoch. We have seen that at each return to perihelion the meteoric cluster is extended over a greater arc of its orbit. Now, Tuttle's comet and the August meteors undoubtedly constituted a single group previous to their entering the solar domain. It is evident, however, from the annual return of the shower during the last 90 years, that the ring is at present nearly if not quite continuous. That the meteoric mass had completed many revolutions before the ninth century of our era is manifest from the frequent showers observed between the years 811 and 841. At the same time, the long interval of 83 years between the last observed display in the ninth century, and the first in the tenth, seems to indicate the existence of a wide chasm in the ring no more than a thousand years since.
Neither the period of the meteors nor that of the comet can yet be regarded as accurately ascertained. The latter, however, in all probability, exceeds the former by several years. Now, at each passage of the earth through the elliptic stream, those meteoroids nearest the disturbing body must be thrown into orbits differing more or less from that of the primitive group. In like manner the near approach of thecometto the earth at an ancient epoch may account for the lengthening of its periodic time.
The Meteors of November 27.
Professor Schiaparelli's brilliant discovery of the relation between comets and meteors may now be ranked with the established truths of astronomy. His hypothesis, however, in regard to theoriginof meteoric streams has not been generally accepted. Comets and meteors, according to his theory, are derived from cosmical clouds existing in great numbers in stellar space. These nebulæ, in consequence of their own motion or that of the sun, are drawn towards the centre of our system. By the unequal influence of the sun's attraction on different parts, such clouds are transformed into currents of great length before reaching the limits of the planetary system. Shooting-stars, fire-balls, aerolites, and comets being all of the same nature, differing merely in size, sometimes fall towards the sun as parts of the same current.
The views of Dr. Weiss, of Vienna, differ from those of Schiaparelli, in that he regards comets as the original bodies by whose disintegration meteor-streams are gradually formed.[26]"Cosmical clouds," he remarks, "undoubtedly appear in the universe, but only of such density that in most cases they possess sufficient coherence to withstand the destructive operation of the sun's attraction, not only up to the boundaries of our solar system, but even within it. Such cosmical clouds will always appear to us as comets when they pass near enough to theearth to become visible. Approaching the sun, the comet undergoes great physical changes, which finally affect the stability of its structure: it can no longer hold together: parts of it take independent orbits around the sun, having great resemblance to the orbit of the parent comet. With periodical comets, this process is repeated at each successive approach to the sun. Gradually the products of disintegration are distributed along the comet's orbit, and if the earth's orbit cuts this, the phenomenon of shooting-stars is produced."
These views of the distinguished astronomer of Vienna are confirmed by the star-shower of November 27, 1872. That the orbits of the earth and Biela's comet intersect at the point passed by the former about the last of November, and that in 1845 the comet separated into two visible parts, has been stated in a previous chapter. The comet's non-appearance in December, 1865, and in September, 1872, was regarded by astronomers as presumptive evidence of its progressive dissolution. A meteoric shower, resulting from the earth's collision with the cometarydébris, was accordingly expected about the 27th of November.
The first indication of the approaching display appeared on the evening of November 24, when meteors in unusual numbers were observed by Professor Newton, at New Haven, Connecticut. On Wednesday evening, the 27th, from the close of twilight till 8 o'clock, a decided shower of shooting-stars was noticed in various parts of the United States. At Greencastle, Indiana, Professor Joseph Tingley counted 110 meteors in 40 minutes, and atPrinceton, in the same State, Mr. D. Eckley Hunter counted 70 in 80 minutes. The numbers seen at New Haven were considerably greater. The fact that the display commenced before daylight had entirely closed seemed to indicate that only the termination of the shower had been observed in this country. Accordingly the display was soon found to have been witnessed from 60° E. to 90° W. of Greenwich, or through 150° of longitude. In England the first bolide of the swarm was seen by M. M. Brinkley, at 3 o'clock,P.M., in full daylight. The meteors were most numerous in the southern part of the continent, particularly in Italy. At the Observatory of Breslau, according to M. Faye, 3000 were seen from 6h. 30m. to 7h. 50m. Dr. Heis reported that at Münster 2500 per hour were counted by two observers. At Naples, Signor Gasparis observed two meteors per second. At Turin, M. Denza, Director of the Observatory, reported 33,400 in 6h. 30m.; many of various and delicate colors, and followed by long and brilliant trains. At some points the numbers were so great that an accurate enumeration was wholly impossible. In short, the display was decidedly the most brilliant that has occurred since that of November 13, 1833.
But some of the most interesting circumstances in connection with the phenomena of November 27, 1872, remain to be detailed. Astronomers without exception regarded the display as due to the earth's passage through thedébrisfollowing in the path of Biela's comet. In accordance with this view Dr. Klinkerfues, of Gottingen, concluded that the comet itself, or rather its largest portion, ought tobe found in the region of the heavens nearly opposite to that from which the meteoroids appeared to radiate.[27]As this point in the southern hemisphere could not be observed in Europe, he conceived the happy idea of detecting the fugitiveby means of the electric telegraph. The following was accordingly dispatched to Mr. Pogson, Director of the Government Observatory at Madras, in Southern India: "Biela touched earth on 27th; search near Theta Centauri." The first two mornings after the receipt of this dispatch were cloudy at Madras. On the third, however, the cometary fragment was found, and its motion accurately measured. The observer described it as circular and rather bright, with no traces of a tail. But one fragment could be detected. On the next morning, December 3, the comet was again observed. Its diameter had sensibly increased; it had a bright nucleus, and still presented a circular aspect. A faint tail was also noticed, equal in length to one-fourth of the moon's apparent diameter. The following mornings being again cloudy, no further observations could be obtained. This cometary mass will be in close proximity to the earth about the last of November, 1892. Another brilliant meteoric shower may therefore be expected at that epoch.
The Meteors of April 20.
Meteoric showers have occurred about the 20th of April in the following years:
B.C.68715A.D.5821093109410951096112211231803
The probability that these meteors are derived from a ring which intersects the earth's orbit, was first suggested by Arago in 1836. A comparison of dates led Herrick to designate 27 years as the probable period of the cluster. In theAstronomische Nachrichten, No. 1632, Dr. Weiss called attention to the fact that the orbit of the first comet of 1861 very nearly intersects that of the earth, in longitude 210°—the point passed by the latter at the epoch of the April meteoric shower. A relation between the meteors and the comet, indicating an approximate equality of periods, was thus suggested as probable. But the comet, according to Oppolzer, does not complete a revolution in less than 415 years. If, therefore, the meteoric period is nearly the same, the known dates of star-showers indicate a diffusion of meteoroids around one half of the orbit previous to the display of the year 15B.C.No subsequent perturbation, then, of a particularpartcould sensibly effect the general orbit of the stream. The infrequency of the display renders, therefore, the hypothesis of a long period extremely improbable.
The entire interval between 687B.C.andA.D.1803is 2490 years, or 92 periods of 27.0652 years; and the known dates are all satisfied by the following scheme:
B.C.687 toB.C.15... 672years=25periods of26.8800y.each.15 toA.D.582... 597"=22"27.1363"A.D.582 to1095... 513"=19"27.0000"1095 to1122... 27"=1"27.0000"1122 to1803... 681"=25"27.2400"
With a period of 27 years, the perihelion being interior to the earth's orbit, the aphelion distance of the meteors would be very nearly equal to the distance of Uranus. The next shower, if the assumed period be correct, ought to occur about 1884. It is worthy of remark that near the time of the last (hypothetical) return Mr. Du Chaillu witnessed the meteors of this epoch, in considerable numbers, in the interior of Africa.
The Meteors of December 12.
Meteoric showers have occurred about the 12th of December in the following years:
1.A.D.901. "The whole hemisphere was filled with those meteors called falling-stars from midnight till morning, to the great surprise of the beholders in Egypt."
2. In 930 a remarkable shower of falling stars was observed in China.
3. Extraordinary meteoric phenomena were observed at Zurich at the same epoch in 1571.
4. On the night of the 11th and 12th of December, 1833, a great number of shooting-stars wereseen at Parma. At the maximum as many as ten were visible at the same time.
5. (Doubtful.) 1861, 1862, and 1863. Maximum probably in 1862. The meteors at this return were far from being comparable in numbers with the ancient displays. The shower, however, was distinctly observed. R. P. Greg, Esq., of Manchester, England, says the period of December 12, 1862, was "exceedingly well defined."
These dates indicate a period of about 291⁄8years. Thus: