the planets, when arriving within the sphere of their attractions!

Respecting this remarkable body which appeared in the year 1770, there can be no doubt, but that the calculations of its orbit were correct for the time that it was observed, and that the semi-axis major of its path was 3.14359, and periodic time 5 years, 210 days; according to this computation it ought to have returned in the year 1776, which it probably did, and passed its perihelion in the month of March of that year, though invisible to the earth from being the whole time lost in the solar rays. In anticipating a subsequent return in 1779, astronomers were disappointed,—it was not visible in that year, nor has it been seen since.

The solution of this mysterious disappearance is connected with one of the most striking facts in astronomical science. Previous to the year 1770, the comet moved in an orbit which, when nearest to the sun, was as remote as the path of Jupiter, and which it traversed in 50 years; in 1767 it passed near this planet, and as the comet and Jupiter were both moving the same way and in nearly the same plane, they continued in proximity for several months; this entirely altered the form of the orbit, and caused the comet to wheel its path towards the orbit of the earth, which it crossed, so close to our planet, that had it have been equal in magnitude and density to our earth it would have shortened our year 2 hrs. 40 min. It continued visible from June to October, was extremely brilliant, and its magnitude was estimated to be thirteen times greater than the moon: its period was now changed from 50 years, to 5 years, 210 days.

A

In approaching the sun in 1779, it again encountered the attraction of Jupiter, and continued within the influence of that planet from June to October before they finally separated; this again so altered the elements of its orbit, that now it does not approach nearer to the sun than the asteroid Ceres, or extend its course beyond the orbit of Uranus, completing its revolution in 20 years. It is, therefore, erroneous to say, that this comet is "lost,"-it is in existence, and in each instance of its wanderings faithfully obeyed the laws of gravitation, which in 1770 introduced a bright and beautiful body to the notice of the human race, and again in 1779 withdrew it into distant regions, where it will always remain unseen by us, unless new perturbations direct its course towards the terrestrial orbit.

This is a brief sketch of the history of one of the most remarkable bodies in the system, and is recorded in the annals of human knowledge as one of the noblest efforts which astronomy has achieved in unravelling the mysteries of nature.

COMET OF 1680.

According to Whiston, the comet of 1680 was a principal agent in producing the beautiful order now established on our planet. In his fanciful Theory of the Earth, he considered this world to be originally composed of heterogeneous materials, having its centre occupied with a solid hot nucleus, of about 8000 miles in diameter: this chaotic globe had no rotation about an axis, but simply a revolution round the sun. After a lapse of some thousand years, there came careering from the realms of night, the comet now known by the name of

the comet of 1680; while our earth, in a chaotic state, was pursuing its dreary course, this comet struck it obliquely, so as to cause it to spin on its soft axle, which by producing the kindly interchange of day and night, rendered it the fit abode of life and organization. In this state, the world continued for many centuries, when this comet again visited it, not to strike, but merely to enfold it within the embraces of its huge tail, and thus occasioned the deluge. This philosopher again recognizes this comet, as the one that appeared 44 years before the Christian era, then called the Julium Sidus, again in the years 532, 1106, and 1680; Sir Isaac Newton, who witnessed it, at its last return, had no doubt, that the last four observations, were of one and the same body, and that its period was 575 years. Whiston essayed to penetrate the veil of futurity, to the period, when this comet, (an appointed executioner) being heated to an excessive degree, by its near approach to the sun, would, on its return, envelope the world in flames, and scatter the ashes of its dissolved elements through the regions of heaven.

The comet of 1680, on November, 11th day, 1 hr. 6 min. P. M. was not above a semi-diameter of the sun, to the northwards of the orbit of the earth: the earth was, however, in a distant part of its course, and unaffected by the terrific visitant. This comet will probably return in the year 2255.

THE COMET OF 1811.

This comet, (to which such frequent reference has been made in this volume,) was considered the baleful star of Napoleon, and the precursor of the conflagration

of Moscow. The agriculturist and the grazier, scowled at the same bright stranger, for parching their lands and drowning their flocks. Heedless of the fears or fancies of man, the comet held on its sublime course, though in France it had the credit of improving the vintage,-the produce of that year being called the "comet wine," -one class alone deriving a cheering influence from its presence the rosy bachannal, who hailed the splendid visitant, for sending wines, brilliant as its nucleus, and sparkling as its tail. It is calculated that this comet will return in the year 6048.

THE COMET OF 1831.

The comet that appeared in January of 1831, was supposed to be that of 1770, for which, however, there was not the least foundation,-not even in period; on the supposition, that its orbit remained unaltered, and that it had duly returned every 5 years, 210 days, but invisible from defectiveness of light, it would not have completed its eleventh revolution till early in the year 1832. The comet of 1831 was seen by Mr. Herapath, on the 7th of January, at 6 in the morning. The tail was then perpendicular to the horizon, inclining towards the south, and of a white colour, apparently between 1° and 2o long. The head was of the same colour as the tail, but far more splendid; it appeared to equal in light, stars of the second magnitude, while it exceeded them in size.

January, 7 days, 6 hrs. 30 min. A.M. Right ascension, 17 hrs. 36 min. 44 sec. South declination, 120 33. An observation by Sir James South, about 48 hours afterwards gives,―right ascension, 17 hrs. 27 min.

57 sec.

South declination, 12° 1' 12".

unfavourable weather, for several days

A succession of

after these ob

servations, prevented the comet from being seen; the following were the observations at Deptford :

.

January, 26 days, 4 hrs. 15 min. to 6 hrs. 15 min. (Wednesday morning). The comet was a little west of a line connecting 8, &, and in Ophiucus, and nearly equally distant from 8 and It had a pale nebulous appearance, was of an irregular circular form; no starlike nucleus, though a tendency to condensation was perceptible towards its centre. On the disappearance of the moon, and before the morning twilight interrupted the observations, an extremely diluted tail was suspected, extending in a westerly direction.

28th day, 6 hrs. morning. Notwithstanding the full moon, the comet was distinctly seen with the telescope: its central light was more sharp and twinkling than on the 26th. It formed the summit of an isosceles triangle, with 8 and & in Ophiuchus,—the comet west of the stars.

The mind contemplates with astonishment the very lengthened periods assigned to some of these erratic bodies; the imagination travels back to those epochs, when they were seen by our ancestors with superstitious awe, or devout religious feeling. This idea enters especially into our views as inhabitants of this rolling world, so frequently the witnesses of the visits of these mysterious pilgrims of space, whose periods may be said on a large scale to measure the cares, joys, and destinies of the human family. The comet of Halley;-this may, it is probable, be seen in the year 1835, by the Octogenarian, who witnessed it in the year 1759 with childish