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first who ascertained the chemical action of galvanism, and its power of decomposing water. Sir Humphry Davy has, also, been very successful in extending this branch of human knowledge. For his important discoveries in reference to this point, the reader will do well to consult Mr. Parkes's Chemical Catechism, or Henry's System of Chemistry.

No. LI.

ON THE AURORA BOREALIS, AND OTHER FIERY METEORS.

Silent from the north

A blaze of meteors shoots: ensweeping first
The lower skies, they all at once converge
High to the crown of heaven, and all at once,
Relapsing quick, as quickly reascend,

And mix, and thwart, extinguish, and renew,
All ether coursing in a maze of light.

THOMSON.

THE Aurora Borealis, or Northern Lights, is a kind of meteor appearing in the northern part of the heavens, mostly in the winter time, and in frosty weather. It is now so generally known, that no description is requisite of the appearance which it usually makes in this country. But it is in the arctic regions that it appears to perfection, particularly during the solstice. In England, the extremities only of these northern lights are to be seen, that we have but a faint idea of their splendour and their motions'. According to the state of the atmosphere,

Of the Aurora Borealis in Shetland, Siberia, and Hud

they differ in colours. They often assume the colour of blood, and make a very dreadful appearance. The rustic sages become prophetic, and terrify the gazing spectators with a dread of war, pestilence, and famine. This superstition was not peculiar to the northern islands; nor are these appearances of recent date. The ancients called them chasmata, trabes, and bolides, according to their forms or colours. But, in old times, they were extremely rare, and, on that account, were the more taken notice of. From the days of Plutarch to those of our sage historian Sir Richard Baker, they were supposed to be portentous of great events, and timid imaginations shaped them into aërial conflicts:

From look to look, contagious through the crowd,
The panic runs, and into wondrous shapes
Th' appearance throws: Armies in meet array,
Thronged with aërial spears and steeds of fire;
Till the long lines of full-extended war
In bleeding fight commixt, the sanguine flood
Rolls a broad slaughter o'er the plains of heaven.
As thus they scan the visionary scene,
On all sides swells the superstitious din,
Incontinent; and busy Frenzy talks

Of blood and battle; cities overturned,
And late at night in swallowing earthquake sunk,
Or hideous wrapt in fierce ascending flame;
Of sallow famine, inundation, storm;

Of pestilence, and every great distress;

Empires subversed, when ruling Fate has struck

son's Bay, and its beneficial effects in the polar regions in general, see No. v, On Winter in the Polar Regions

By dancing meteors then, that ceaseless shake
A waving blaze refracted o'er the heavens,
And vivid moons, and stars that keener play
With double lustre from the glossy waste,
Ev'n in the depth of polar night, they find
A wondrous day: enough to light the chase,
Or guide their daring steps to Finland-fairs. THOMSON.

Th' unalterable hour: ev'n Nature's self
Is deemed to totter on the brink of time.

Not so the man of philosophic eye,
And inspect sage; the waving brightness he
Curious surveys, inquisitive to know
The causes, and materials, yet unfixed,
Of this appearance beautiful and new.

THOMSON.

The earliest distinct history of this phenomenon, is what we have from the learned Dr. Halley, in the Philosophical Transactions, No. 347. The first account he gives, is of the appearance of what the author calls burning spears, and which was seen at London in 1560. This account is taken from a book entitled, A Description of Meteors, by W. F. D. D. and reprinted at London in 1654. The next appearance, on the testimony of Stow, was in October 1564. In 1574 also, according to Camden and Stow, an aurora borealis was observed two nights successively. Two were seen, at different times, in the year following, in Brabant. They were compared, by Cornelius Gemma, to spears, fortified cities, and armies fighting in the air. Michael Mæstlin, tutor to the great Kepler, assures us, that, in the county of Wurtemberg in Germany, these phenomena, which he calls chasmata, were seen by himself, no less than seven times, in 1580. In 1581, they appeared in an extraordinary manner in April and September, and in a less degree at some other times of the same year. In September 1621, this phenomenon was observed all over France, and described by Gassendus, who gave it the name of aurora borealis; yet neither this, nor any similar appearances posterior to 1574, are described by English writers till the year 1707; which, as Dr. Halley observes, shows the great neglect of curious matters which at that time prevailed. From 1621, indeed, to 1707, there is no mention of an aurora borealis having been seen by any person, either in

England or foreign countries; and, considering the number of astronomers, who, during that period, were almost constantly observing the heavens, we may reasonably conclude, that no such phenomenon appeared till after an interval of eighty-six years. In 1707, a small one was seen in November; and during that year and the next, the same appearances were repeated five times. The next on record is that mentioned by Dr. Halley, as appearing on March 6, 1716. The splendour of this attracted universal attention. By the vulgar it was viewed with consternation; and they considered it as mark ing the introduction of a foreign race of princes into this country'. Since that time, these meteors have been so common, that no account has been kept of them.

It was for a long time a doubt whether this meteor appeared only in the northern hemisphere, or whether it were to be observed also near the south

pole. This is now ascertained by Mr. Forster, who, in his Voyage round the World with captain Cook, assures us, that he observed it in the high southern latitudes, although with appearances somewhat different from those which are seen here. • On the 17th of February 1773 (says Mr. Forster) as we were in latitude 58° south, a beautiful phenomenon was observed during the preceding night, which ap peared again several following nights. It consisted of long columns of a clear white light, shooting up from the horizon to the eastward, almost to the ze

Dr. Halley observed, that this aurora borealis rose to a prodigious height, it being seen from the west of Ireland to the confines of Russia and Poland on the east; nor did he know how much farther it might be visible; so that it extended at least 30° in longitude, and from latitude 50° north it was seen over all the northern parts of Europe; and, in all the places where it was visible, the same appearances were exhibited, which Dr. Halley observed in London.

nith, and gradually spreading on the whole southern part of the sky. These columns were sometimes bent sidewise at their upper extremities; and, although in most respects similar to the northern lights of our hemisphere, yet differed from them in being always of a whitish colour; whereas ours assume various tints, especially those of a fiery and purple hue. The sky was generally clear when they appeared, and the air sharp and cold, the thermometer standing at the freezing point.'

I shall not attempt to give any account of the earlier conjectures concerning the cause of this phenomenon. It will be sufficient to observe, that ever since the identity of lightning, and of the electric matter, has been ascertained, philosophers have been naturally led to seek the explication of aërial meteors in the principles of electricity; and there is now no doubt, but that the greater part of them, and especially the aurora borealis, are electrical phenomena. Beside the more obvious and known appearances which constitute a resemblance between this meteor and the electric matter by which lightning is produced, it has been observed, that the aurora borealis produces a very sensible fluctuation in the magnetic needle; and that, when it has extended lower than usual into the atmosphere, the flashes have been attended with various sounds of rumbling and hissing, taken notice of both by Beccaria and M. Messier. But I have, in some measure, anticipated this part of my subject, in my paper On Comets', to which I refer my readers for the sentiments of Dr. Hamilton and abbé Mann, who have each produced the most satisfactory arguments to demonstrate the identity of the matter that forms the tail of comets, the aurora borealis, and the electric fluid. Dr. Blagden has also given a copious illustration of

1 No. VIII.

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