THE Aurora Borealis is a luminous appearance, generally observed in high northern latitudes, and commonly to the north of the observer, whence it has got the name of Northern Lights; it is known also among the vulgar, by the name of "the streamers," or the "merry-dancers." The Aurora Borealis may be divided into two kinds, the tranquil and the varying. The tranquil shines with a mild and steady light, similar to the different stages of moon-light, either as it appears near the time of new moon, or as it gradually inereases when the moon becomes more enlightened; sometimes it is more vivid than the light of the moon when full; and it often preserves, for a considerable time, the form in which it first appeared, with little or no variation. Muschenbroek has paid much attention to this kind of meteor, and has given it several names, according to the form which it as sumes; but as these names are founded only in fancy, and are not necessary to an explication of the theory, we shall omit them. The varied Aurora is more remarkable in its appearance, and occasionally exhibits the most brilliant and rapidly diversified forms. The following are some of its very interesting properties: It is usually of a reddish colour, inclining to yellow, and it frequently sends out corruscations of pale light, which seem to rise from the horizon in pyramidal undulating forms, shooting with great velocity towards the zenith. This kind of meteor, which is less frequent as we go towards the Equator, is almost constant during the long winter nights in the Polar Regions. In the Shetland Isles they afford the inhabitants great relief, amid the gloomy darkness of their long and dreary nights. They commonly appear at twilight, near the horizon, of a dun colour, approaching to yellow, and continue in that state for several hours; they afterwards break into streams of stronger light, spread into columns, then slowly alter into innumerable shapes, and vary their colours from all the yellow tints to an obscure russet;

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frequently covering the whole atmosphere, exhibiting the most romantic forms and the most beautiful appearance. According to Muschenbroek, in that region of the air which is directly towards the north, or which stretches from the north towards the east or west, there at first appears a cloud in the horizon, which rarely rises to the height of 40 degrees. This cloud is sometimes contiguous to the horizon, sometimes detached from it, in which last case the intermediate sky appears of a bright blue colour. The cloud occupies a portion of the heavens, extending in length to 100 degrees, and sometimes still farther. It is generally white and shining, but sometimes black and thick. Its upper edge is parallel to the horizon, bordered by a long train of light, which rises higher in some places than in others. It appears also bent in the form of a bow, or like the segment of a sphere which has its centre considerably beneath the horizon; and sometimes a large white or luminous band is visible, skirting the upper edge of the black cloud. The dark part of the cloud becomes white and luminous when the Aurora has shone for some time, and after it has sent forth several bright and fiery rays. Then, from the superior edge of the cloud, rays issue in the form of jets, which are sometimes many, sometimes few in number,-sometimes close together, sometimes removed several degrees asunder. These jets diffuse a very brilliant light, as if a luminous or fiery liquor were driven with impetuosity from a syringe. The jet increases in brightness, and has less bulk when it at first issues from the cloud; but it dilates and grows dimmer as it goes farther off. There then arises, from a large opening in the cloud, a luminous train, or column, of which the motion is at first gentle and uniform, and which increases in size as it advances. The dimensions and duration of these columns vary considerably; their light is sometimes white, sometimes reddish, sometimes of a blood colour; and as they advance, their colours

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change, till they form a kind of arch in the heavens. When several of these columns, issuing from different places, encounter each other in the zenith, they intermingle with each other, and form, at their junction, a small thick cloud, which seems, as it were, to kindle, and sends forth a light considerably more brilliant than any of the separate columns. This light changes to green, blue, and purple; and, quitting its original station, it directs itself towards the south, in the form of a small bright cloud. When no more columns are seen to issue, the cloud assumes the appearance of the morning dawn, and insensibly dissipates itself. Sometimes the Aurora is formed and disappears in the course of a few minutes; at other times it continues the whole night; and one that was observed by Muschenbroek in 1734, lasted for ten days and nights successively. The lucid columns are often so transparent, that stars of the first and second magnitudes are visible through them; these also shine through the white border of the horizontal cloud, and sometimes, though rarely, through the opaque cloud itself. But many parts are so thin, that the smallest stars which are visible to the naked eye may be seen through them. A more beautiful spectacle than what is very frequently presented to us in these meteoric appearances, cannot easily be imagined; the spectacle is often grand and terrific, and is sometimes attended with a hissing, crackling noise, which rushes through the air, and is similar to a display of large fire-works. The hunters who pursue the white and blue foxes, on the confines of the icy sea, are often overtaken by these northern lights, at which times their dogs are so much frightened that they will not move, but crouch upon the ground till the noise has passed by them. Maupertuis observed a remarkable Aurora at Oswer-Zornca, which excited his admiration; an extensive region of the heavens towards the south appeared tinged with so lively a red, that the whole of the constellation Orion seemed to be dyed in blood. This light was for some time fixed, but it was soon in motion, and after having successively

assumed all the tints of violet and blue, it formed a dome, the summit of which was near the zenith in the south-west. Its splendour was so great as not to be affected by the strong light of the moon. He adds, that he only observed two of these red northern lights while he was in Lapland, and thinks that they are of rare occurrence in that country, although the Aurora there assumes a great variety of tints; he moreover observes, that they are considered by the poor ignorant natives as ominous, and the forerunners of calamity.

The accounts of noises attending the Aurora Borealis are sufficiently corroborated; they have been heard by numerous persons, and in various places. They have been heard in Hudson's Bay, in Sweden, Norway, and Lapland. Muschenbroek mentions, that the Greenland whale-fishers assured him that they had frequently heard the noise of the Aurora; but he adds, that no person in Holland ever heard any noise occasioned by them. Mr Cavallo, however, declares, that being in Northampton at the time when the northern lights were remarkably bright, he is confident that he heard a hissing or a whizzing sound. In the Orkney and Shetland Isles they are frequently heard. The writer of this article has been told by more than one gentleman from Orkney, that the noise made by the Aurora is often heard by the natives; and one of them assured him that he had sometimes heard it himself. They have also been heard in Canada. As we might very naturally expect, the Aurora Borealis is by no means confined to the northern hemisphere; for similar appearances, and like noises, have been observed and heard in high southern latitudes. If the existence of the Aurora Australis was at any time doubtful, it was completely ascertained by Captain Cooke in his second voyage round the world. "On February the 17th, in 1773,” says Mr Foster, who accompanied Cooke in the capacity of Naturalist, "in south latitude 58 degrees, a beautiful phenomenon was observed during the preceding night, which appeared again on this and several following nights. It consisted of