CHAPTER I.

SHOOTING-STARS.

I. The Meteors of November 12th-14th.

Although shooting-stars have doubtless been observed in all ages of the world, they have never, until recently, attracted the special attention of scientific men. The first exact observations of the phenomena were undertaken, about the close of the last century, by Messrs. Brandes and Benzenberg. The importance, however, of this new department of research was not generally recognized till after the brilliant meteoric display of November 13th, 1833. This shower of fire can never be forgotten by those who witnessed it.[1] The display was observed from the West Indies to British America, and from 60° to 100° west longitude from Greenwich. Captain Hammond, of the ship Restitution, had just arrived at Salem, Massachusetts, where he observed the phenomenon from midnight till daylight. He noticed 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 soon 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 in Cumana, South America, by Humboldt, who states that it was "simultaneously seen in the new continent, from the equator to New Herrnhut, in Greenland (lat. 64° 14´), and between 46° and 82° longitude."

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 examination of old historical records led to the discovery of at least 12 appearances of the November shower previous to the great fall of 1833. The descriptions of these phenomena will be found collected in an interesting article by Prof. H. A. Newton, in the _American Journal of Science and Arts_, for May, 1864. They occurred in the years 902, 931, 934, 1002, 1101, 1202, 1366, 1533, 1602, 1698, 1799, and 1832. Besides these 12 enumerated by Professor Newton as "the predecessors of the great exhibition on the morning of November 13th, 1833," we find 6 others, less distinctly marked, in the catalogue of M. Quetelet.[2] These were in the years 1787, 1818, 1822, 1823, 1828, and 1831. From 1883 to 1849, inclusive, Quetelet's catalogue indicates 11 partial returns of the November shower; making in all, up to the latter date, 29. In 1835, November 13th, a straw roof was set on fire by a meteoric fire-ball, in the department de l'Aine, France. On the 12th of November, 1837, "at 8 o'clock in the evening, the attention of observers in various parts of Great Britain was directed to a bright luminous body, apparently proceeding from the North, which, after making a rapid descent, in the manner of a rocket, suddenly burst, and scattering its particles into various beautiful forms, vanished in the atmosphere. This was succeeded by others all similar to the first, both in shape and the manner of its ultimate disappearance. The whole display terminated at ten o'clock, when dark clouds, which continued up till a late hour, overspread the earth, preventing any further observations."--_Milner's Gallery of Nature_, p. 142.

In 1838, November 12th-13th, meteors were observed in unusual numbers at Vienna. One of extraordinary brilliancy, having an apparent magnitude equal to that of the full moon, was seen near Cherburg.

On several other returns of the November epoch the number of meteors observed has been greater than on ordinary nights; the distinctly marked exhibitions, however, up to 1866, have all been enumerated.

THE SHOWER OF NOVEMBER 14, 1866.

The fact that all great displays of the November meteors have taken place at intervals of thirty-three or thirty-four 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. 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 Prof. 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. This was about six times the ordinary number. A more brilliant display was, however, witnessed in Europe. Meteors began to appear in unusual frequency about eleven o'clock on the night of the 13th, and continued to increase with great rapidity for more than two hours; the maximum being reached a little after one o'clock. The Edinburgh _Scotsman_, of November 14th, contains a highly interesting description of the phenomenon as observed at that city. "Standing on the Calton Hill, and looking westward," the editor remarks,--"with the Observatory shutting out the lights of Prince's 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 few seconds, 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. The spectacle, of which the loftiest and most elaborate description could but be at the best imperfect--which truly should have been seen to be imagined--will not soon pass from the memories of those to whose minds were last night presented the mysterious activities and boundless fecundities of that universe of the heavens, the very unchangeableness of whose beauty has to many made it monotonous and of no interest."

The appearance of the phenomenon, as witnessed at London, is minutely described in the _Times_ of November 15th. The shower occurred chiefly between the hours of twelve and two. About one 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.

_The Meteors of 1866 compared with those of former Displays._

The star shower of 1866 was much inferior to those of 1799 and 1833.[3] With these exceptions, however, it has, perhaps, been scarcely surpassed during the last 500 years. Historians represent the meteors of 902 as innumerable, and as moving like rain in all possible directions.[4] The exhibition of 1202 was no less magnificent. The stars, it is said, were seen to dash against each other like swarms of locusts; the phenomenon lasting till daybreak.[5] 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, Dom 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 following is Humboldt's description of the shower of 1799, as witnessed by himself and Bonpland, in Cumana, South America: "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."

DISCUSSION OF THE PHENOMENA.

Since the memorable display of November 13th, 1833, the phenomena of shooting-stars have been observed and discussed by Brandes, Benzenberg, Olbers, Saigey, Heis, Olmsted, Herrick, Twining, Newton, Greg, and many others. In the elaborate paper of Professor Olmsted, it was shown that the meteors had their origin at a distance of more than 2000 miles from the earth's surface; that their paths diverged from a common point near the star _Gamma Leonis_; that in a number of instances they became visible about 80 miles from the earth's surface; that their velocity was comparable to that of the earth in its orbit; and that in some cases their extinction occurred at an elevation of 30 miles. It was inferred, moreover, that they consisted of combustible matter which took fire and was consumed in passing through the atmosphere; that this matter was derived from a nebulous body revolving round the sun in an elliptical orbit, but little inclined to the plane of the ecliptic; that its aphelion was near that point of the earth's orbit through which we annually pass about the 13th of November--the perihelion being a little within the orbit of Mercury; and finally that its period was about one-half that of the earth. Dr. Olmsted subsequently modified his theory, having been led by further observations to regard the zodiacal light as the nebulous body from which the shooting-stars are derived. The latter hypothesis was also adopted by the celebrated Biot.

The fact that the position of the radiant point does not change with the earth's rotation, places the cosmical origin of the meteors wholly beyond question. The theory of a closed ring of nebulous matter revolving round the sun in an elliptical orbit which intersects that of the earth, affords a simple and satisfactory explanation of the phenomena. This theory was adopted by Humboldt, Arago, and others, shortly after the occurrence of the meteoric shower of 1833. That the body which furnishes the material of these meteors moves in a closed or elliptical orbit is evident from the periodicity of the shower. It is also manifest from the partial recurrence of the phenomenon from year to year, that the matter is diffused around the orbit; while the extraordinary falls of 1833, 1799, 1366, and 1202, prove the diffusion to be far from uniform.

ELEMENTS OF THE ORBIT.

Future observations, it may be hoped, will ultimately lead to an accurate determination of the elements of this ring: many years, however, will probably elapse before all the circumstances of its motion can be satisfactorily known. Professor Newton, of Yale College, has led the way in an able discussion of the observations.[6] He has shown that the different parts of the ring are, in all probability, of very unequal density; that the motion is retrograde; and that the time, during which the meteors complete a revolution about the sun, must be limited to one of five accurately determined periods, viz.: 180·05 days, 185·54 days, 354·62 days, 376·5 days, or 33·25 years. He makes the inclination of the ring to the ecliptic about 17°. The five periods specified, he remarks, "are not all equally probable. Some of the members of the group which visited us last November [1863] gave us the means of locating approximately the central point of the region from which the paths diverge. Mr. G. A. Nolen has, by graphical processes specially devised for the purpose, found its longitude to be 142°, and its latitude 8° 30´. This longitude is very nearly that of the point in the ecliptic toward which the earth is moving. Hence the point from which the absolute motion of the bodies is directed (being in a great circle through the other two points) has the same longitude. The absolute motion of each meteor, then, is directed very nearly at right angles to a line from it to the sun, the deviation being probably not more than two or three degrees.

"Now, if in one year the group make 2 ± 1/33·25 revolutions, there is only a small portion of the orbit near the aphelion which fulfills the above condition. In like manner, if the periodic time is 33·25 years, only a small portion of the orbit near the perihelion fulfills it. On the other hand, if the annual motion is 1 ± 1/33·25 revolutions, the required condition is answered through a large part of the orbit. Inasmuch as no reason appears why the earth should meet a group near its apsides rather than elsewhere, we must regard it as more probable that the group makes in one year either 1 + 1/33·25, or 1 - 1/33·25 revolutions."

Professor Newton concludes that the third of the above-mentioned periods, viz., 354·62 days, combines the greatest amount of probability of being the true one. We grant the force of the reasons assigned for its adoption. At least one consideration, however, in favor of the long period of 33·25 years is by no means destitute of weight: of nearly 100 known bodies which revolve about the sun in orbits of small eccentricity, not one has a retrograde motion. Now if this striking fact has resulted from a general cause, how shall we account for the backward motion of a meteoric ring, in an orbit almost circular, and but little inclined to the plane of the ecliptic? In such a case, is not the preponderance of probability in favor of the longer period?

A revolution in 33·25 years corresponds to an ellipse whose major axis is 20·6. Consequently the aphelion distance would be somewhat greater than the mean distance of Uranus. It may also be worthy of note, that five periods of the ring would be very nearly equal to two of Uranus.

The _Monthly Notices of the Royal Astronomical Society_ for December, 1866, and January, 1867, contain numerous articles on the star shower of November 13th-14th, 1866. Sir John Herschel carefully observed the phenomena, and his conclusions in regard to the orbit are confirmatory of those of Professor Newton. "We are constrained to conclude," he remarks, "that the true line of direction, in space of each meteor's flight, lay in a plane at right angles to the earth's radius vector at the moment; and that therefore, except in the improbable assumption that the meteor was at that moment _in perihelio_ or _in aphelio_, its orbit would not deviate greatly from the circular form." The question is one to be decided by observation, and the only meteor whose track and time of flight seem to have been well observed, is that described by Professor Newton in _Silliman's Journal_ for January, 1867, p. 86. The velocity in this case, if the estimated time of flight was nearly correct, was _inconsistent with the theory of a circular orbit_.

It is also worthy of notice that Dr. Oppolzer's elements of the first comet of 1866 resemble, in a remarkable manner, those of the meteoric ring, supposing the latter to have a period of about 33-1/4 years. Schiaparelli's elements of the November ring, and Oppolzer's elements of the comet of 1866, are as follows:

November Comet of Meteors. 1866.

Longitude of perihelion 56° 25´ 60° 28´ Longitude of ascending node. 231 28 231 26 Inclination 17 44 17 18 Perihelion distance 0·9873 0·9765 Eccentricity 0·9046 0·9054 Semi-axis major 10·3400 10·3240 Period, in years 33·2500 33·1760 Motion Retrograde. Retrograde.

It seems very improbable that these coincidences should be accidental. Leverrier and other astronomers have found elements of the meteoric orbit agreeing closely with those given by Schiaparelli. Should the identity of the orbits be fully confirmed, it will follow that the comet of 1866 _is a very large meteor_ of the November stream.

The researches of Professor C. Bruhns, of Leipzig, in regard to this group of meteors afford a probable explanation of the division of Biela's comet--a phenomenon which has greatly perplexed astronomers for the last twenty years. Adopting the period of 33-1/4 years, Professor Bruhns finds that the comet passed extremely near, and probably _through_ the meteoric ring near the last of December, 1845. It is easy to perceive that such a collision might produce the separation soon afterward observed.

As the comet of Biela makes three revolutions in twenty years, it was again at this intersection, or approximate intersection of orbits about the end of 1865. But although the comet's position, with respect to the earth, was the same as in 1845-6, and although astronomers watched eagerly for its appearance, their search was unsuccessful. In short, _the comet is lost_. The denser portion of the meteoric stream was then approaching its perihelion. A portion of the arc had even passed that point, as a meteoric shower was observed at Greenwich on the 13th of November, 1865.[7] The motion of the meteoric stream is retrograde; that of the comet, direct. Did the latter plunge into the former, and was its non appearance the result of such collision and entanglement?