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ed in the eastern and western parts of the horizon, were connected by an arch of a fainter light.

It reached the horizon in the W.S.W. point. In its course it passed about 12° to the south of the zenith. Its breadth was about 9 or 10f. It remained visible about ten or twelve minutes after he first discovered it, and they vanished gradually and irregularly. He observed no corruscations, nor any motion in this arch. A few minutes after another, and still more beautiful, arch made its appearance. It arose a point or two nearer the N. E. thap the former had done. Its southern edge passed up a little to the north of the tail of ihe Great Bear, which was then in a vertical position. Its northern edge appeared at first a little to the south of the polar star; but, during the continuance of the phenomenon, it gradually receded about 10° to the south. The arch descended about the W.N.W.; but neither the eastern nor western extremities reached the horizon; each of thein ending in a point gradually formed a little above the horizon. This arch might be about 10 or 19° at its vertex. It continued visible for half an hour; and though he could not discover any corruscations, or quick motion, in any part, yet the different portions of it were perpetually varying in the density of their light, and the whole arch, or at least its vertex, made a slow and equitable motion towards the south. Where the light was the most dense, the smaller stars were rendered invisible by the arch, but stars of the second magnitude were not totally eclipsed by it. This arch disappeared, as the former, by patches; the light gradually becoming less intense. The colour of both these arches was white. Before the latter arch bad entirely disappeared, a small one, not quite so broad as the rainbow, arose from its eastern leg, and ascending in a curvilineal direction to the polar star, terminated there. Its light was more faint than that of the other two arches; and it continued visible about a quarter of an hour. The evening was very five when he saw these beautiful phænomena; the stars were bright, and there was not a cloud to be seen except in the horizon. There was a steady light in the north, without the least corruscation, extending from the N. E. to N.W. The wind blew from the N. E.

March 26, about the same time in the evening, Mr. H. was es. tertained with a similar appearance. He first observed two or

three columns of aurora borealis shooting upwards in the north ; and in a skort time after a complete arch, like those already de. scribed, though somewhat different in its position,

It arose between the E. and N. and N. E. points, passed obliquely to the south below Arcturus, and descended in the west through Orion, having alınost the same direction through that constellatiou which the equator has. Its light was the most faint about the vertex of the arch. Its most dense parts were continually varying in the intensity of their light. The larger stars were visible through its densest parts. It varied its position, and it continued visible about hialf an hour; but there was nothing which could be called a shoot. ing, or quick corruscation. There was a steady northern light all the evening, or at least till the arch had disappeared.

The grandest specimen of this phenomenon which Mr. H. had seen, appeared on the 12th of April, between nine and ten in the evening. He perceived a broad arch of a bright pale yellow, arising between Arcturus and Lyra, about the right leg of Hercules, and passing considerably to the south of the zenith, its northern border being a little south of Pollux, and descending to the horizon near Orion, which was then setting. This arch seemed to be about 15° in breadth, and was of such a varied density, that it appeared to consist of small columps of light, wbich had a sensible motion. After above ten minutes he saw innumerable bright corruscations, shooting out at right angles from its northern edge, which was concave, and elongating themselves more and more till they had nearly reached the northern horizon. As they descended, their extremi. ties were tipped with an elegant crimson, such as is produced by the electric spark in an exhausted tube. After some time this aurora borealis ceased from shooting, and formed a range of beauti. ful' yellow clouds, extending horizontally about a quarter of a circle. The greatest part of the aurora borealis which darted from this arch towards the north, as well as the cloud-like and more sta. tionary aurora, were so dense that they hid the stars from view. The moon was eleven days old, and shone bright during this scene, but did not eclipse the brightness of these corruscations. The wind was at north, or a little inclined to the east.

The last phenomenon of this kind which Mr. H. saw, was on the 26th of April. About a quarter before ten in the evening, he observed in the W. a luminous appearance, of the colour of the most common aurora borealis. From this mass or broad column of light issued three luminous arches, each of which made a different angle with the horizon. That nearest to the south seemed to arise at right angles with the horizon; wbile that nearest to the north made the smallest angle, and passed towards the N. E through the constellation Auriga, having Capella close to its upper edge. He had not viewed them many minutes when they were rendered invisible by a general blaze of aurora borealis, which possessed the space just before occupied by these arches. He was soon satisfied that where the aurora borealis was dense, it entirely bid from view the stars of the second magnitude. He observed this particularly with respect to the star B in the left shoulder of Auriga. But the corruscations were never so dense as to render Capella invisible. The wind was between the N. and N. E. this evening.

After comparing the phænomena above described with each other, and with those observed by Mr. Cavallo, in London; by Mr. Swinton, at Oxford; by Dr. Huxham, at Plymouth; and by Mr. Sparshal, at Wells, in Norfolk ; Mr. H. cannot entertain a doubt, that these arches had all the same origin; and that they ought to be considered as a species of that kind of meteor called aurora borealis,

(Phil. Trans, Abr. Vol. xvi, .year 1790.

CHAP. XLVI.

BLAZING BALLS AND BURNING STONES.

SECTION I.

General Remarks. There is a very extraordinary class of atmospheric bodies, usually known by the name of fiery or luminous meteors, which yet remaius to be described, and which has never hitherto been satis. factorily accounted for. They are of all sizes, from a small shoot. ing star of the fifth magnitude, to a cone or cylinder of two or three miles in diameter. They differ in consistency as much as in dimensions, and in colour as much as in either. They are sometimes a sublle, luminous, and pellucid vapour ; sometimes a compact ball or globe, as though the material of which they are formed, were more condensed and concentrated. And not un. frequently they have been found to consist of both, and consequently to assume a coinet-like appearance, with a nucleus or compact substance in the centre or towards the centre and a long thin pellucid luminous main, or tail, sweeping on each side. They are sometimes of a pale white light; at others of a deep igneous crimson; and occasionally iridescent and vibratory. The rarer meteors appear frequently to vanish all of a sudden, as though abruptly dissolved or extinguished in the atmospheric medium; their fight is accompanied with a hissing sound, and their disappearance with an explosion. And the n ost compact of them, or the nuclei of those that are rarer have often descended 10 the sur. face of the earth, and with a force sufficient to bury them many feet under the soil; generally exhibiting marks of imperfect fusion and considerable heat. The substance, in these cases, is for the most part metalline ; but the ore of which they consist is no where to be met with, in the same constituent proportions, in the bowels of the earth. Under this form the projected niasses are denomiuated meteoric stones or aërolites.

Yet, however these extraordinary bodies may differ in colour, shape, dimensions, or consistency; they seem to agree with great exactness, in their transient appearance, velocity, and elevation, when first discovered. It is seldom they have been capable of being traced longer than from a single moment to two or three mi. nutes; their height bas been pretty fairly and coucurrently calculated at from fifty to sixty miles above the surface of the earth; and their velocity, from similar calculations, at from twenty to thirty miles in a second; consequently in the lowest computation exhibiting a sapidity more than ninety times that of sound, and nearly approaching to that of the earth in her annual orbit.

Dr. Halley calculated that the meteor seen throughout England in 1718 19 (as the reader will find in his own very instructing description in the subjoined section) must have been sixty miles high, and have passed over three hundred geographical miles in a minute. It exploded witb a great report.

Lerry coinputed that the extensive meteor which appeared to have originated over the coasts of England, in 1770, was from the first more than eighteen leagues high; and described more than sixty leagues in ten seconds.

The prodigious meteor that appeared nearly in the same direction, in 1783, was calculated by Dr. Blagdon (as we shall perceive presently) to have formed at a height of fifty mjles; to have been about two miles in length; and to bave moved at the rate of about twenty miles in a second. It rushed with a hissing noise, and ex. ploded with a report. Mr. Cavallo computed that at the time of the explosion it was 564 miles high, 1070 yards in diameter, and its path immediately over Lincolnshire.

Awidst the numerous hypotheses that have been successively advanced, to account for these extraordinary phænomena, and we may add, as successively abandoned, we shall content ourselves with enumerating the following, as those which have possessed the greatest pumber of advocates.

1. It was contended by Sir J. Pringle, and various other pliilosa phers, that they are revolving bodies, or a kind of terrestrial comets.

2. Dr. Halley conjectured them to consist of combustible 92. pours, accumulated and formed into concrete bodies on the out skirts, or extreme regions of the atmosphere, and to be suddenly

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