the rising vapourous smoke out of a great blaze when agitated. But one thing I assured myself of by this attendance and watching, viz. that this iris-like figure by no means owed its origin to the sun's beams; for that about three in the morning, the sun being in the middle between the north and east, our aurora had not followed him, but ended in that very point where he then was; whereas in the true north, which the sun had long passed, the light re. mained unchanged, and in its full lustre.

Thus far I have attempted to describe what was seen, and am heartily sorry I can say no more as to the first and most surprising part thereof, which however frightful and amazing it might seem to the vulgar beholder, would have been to me a most agreeable and wished-for spectacle; for I then should have contemplated propriis oculis all the several sorts of meteors I remember to have hitherto heard or read of. This was the only one I had not as yet seen, and of which I began to despair, since it is certain it has not happened to any remarkable degree in this part of England since. I was born: nor is the like recorded in the English annals since the year of our Lord 1574, that is above 140 years since, in the reign of Queen Elizabeth. Then, as we are told by the historians of those times, Cambden and Stow, eye-witnesses of sufficient credit, for two nights successively, viz. on the 14th and 15th of Nov.. that year, much the same wonderful phænomena were seen, with almost all the same circumstances as now.

Nor indeed, during that reign, was this so rare a sight as it has been since. For we find in a book entitled, A Description of Meteors, reprinted at London in the year 1654, signed W. F. D.D. that the same thing, which the author there calls Burning Spears, was seen at London on January 30, 1560; and again by the testimony of Stow, on the 7th of October, 1564. And from foreign authors we learn, that in the year 1575 the same was twice repeated in Brabant, viz. on the 13th of February and 28th of September; and seen and described by Cornelius Gemma, professor of medi. cine in the university of Lovain, and son of Gemma Frisius the mathematician. In a discourse he wrote on the prodigies of those times, after several ill-boding prognostics, he thus very properly describes the cupola and corona he saw in the Chasma, as he calls it, of February. "A little after," says he, "spears and new flames

arising the sky seemed to be all on a flame, from the north quite up to the zenith; and at last, the face of the sky was, for a whole hour together, changed into the uncommon form of a dice-box, the blue and white changing alternately, with no less swiftness and vertigious motion than the sun beams do, when reflected from a mirror."

Here it is not a little remarkable, that all these four already mentioned fell exactly on the same age of the moon, viz. about two days after the change.

As to the other of September in the same year 1575, Gemma writes; "The form of the Chasma, of the 28th of September following, immediately after sun set, was indeed, less dreadful, but still more confused and various; for, in it were seen a great many bright arches, out of which gradually issued spears, cities with towers and men in battle array; after that, there were excursions of rays every way, waves of clouds and battles; mutually pursued and fled, and wheeling round in a surprising manner." hence it is manifest that this pheomenon appeared in our neigh. bourhood three several times, and that with considerable intervals, within the compass of one year; though our English historians have not recorded the two latter; nor did Gemma see that of November, 1574, probably by reason of clouds. After this, in the year 1580, we have the authority of Michael Mostlin, (himself a good astronomer, and still more famous for having had the honour to be the great Kepler's tutor in the sciences) in his book de Cometa, 1580, that at Baknang in the country of Wirtemburg in Germany, these chasmata, as he likewise stiles them, were seen by himself no less than seven times within the space of twelve months. The first and most considerable of these, was on the very same day of the month with ours, viz, on Sunday the 6th of March, and was attended with much the same circumstances. And again, the same things were seen in a very extraordinary manner on the 9th of April and 10th of September following: but in a less degree, on the 6th of April, 21st of September, 26th of December, and 16th of February 1581: the last of which, and that of the 21st of September must needs have been more considerable than they then appeared, because the moon being near the full, necessa. rily effaced all the fainter lights. Of all these however no one is mentioned in our annals to have been seen in England, nor in

any other place that I can find; such was the neglect of curious matter in those days.

The next in order that we hear of, was that of the year 1621, on September the 2d. O. S. seen all over France, and is well described by Gassendus in his physics, who gives it the name of aurora borealis. This, though little inferior to what we lately saw, and appearing to the northwards both of Rouen and Paris, is no where said to have been observed in England, over which the light seemed to lie. And since then, for above 80 years, we have no account of any such sight, either at home or abroad: though for above half that time, these Philos. Trans. have been a constant register of all such extraordinary occurrences. The first we find on our books, was one of small continuance, seen in Ireland by Mr. Nave, Nov. 10, 1707; of which see Philos. Trans. No. 320. And in the Mis. cellanea Berolinensia, published in 1710, we learn that in the same year 1707, both on January 24, and February 18, O.S. something of this kind was seen by M. Olaus Romer, at Copenhagen: and again February 23, the same excellent astronomer observed there such another appearance, but much more considerable; of which yet he only saw the beginning, clouds interposing. But the same was seen that night by Mr. Gottfried Kirch at Berlin, about 200 miles from Copenhagen, and lasted there till past ten at night. To these add another small one of short duration, seen near London, a little before midnight between the 9th and 10th of August, 1708, by the Right Rev. Philip, Lord Bishop of Hereford, and by his lordship communicated to the Royal Society: so that, it seems, in little more than eighteen months this sort of light has been seen in the sky, no less than five times, in the years 1707 and 1708.

Hence we may reasonably conclude that the air, or earth, or both, are sometimes, though but seldom and at great intervals, disposed to produce this phenomenon: for though it be probable that many times, when it happens, it may not be observed, as falling out in the day time, or in cloudy weather, or bright moonshine yet that it should be so very often seen at some times, and so seldom at others, is what cannot well be accounted for that way. Therefore considering what might be most probably the material cause of these appearances; what first occurred was the vapour of water rarefied exceedingly by subterraneous fire, and tinged with sulphureous steams; which vapour is now generally supposed by

naturalists to be the cause of earthquakes. And as earthquakes happen with great uncertainty, and have been sometimes frequent in places, where for many years before and after they have not been felt; so these, which we might be allowed to suppose produced by the eruption of the pent vapour through the pores of the earth, when it is not in sufficient quantity, nor sudden enough to shake its surface, or to open itself a passage by rending it. And as these vapours are suddenly produced by the fall of water on the nitro-sulphureous fire under ground, they might well be thought to get from thence a tincture which might dispose them to shine in the night, and a tendency contrary to that of gravity; as we find the vapours of gunpowder, when heated in vacuo, to shine in the dark, and ascend to the top of the receiver though exhausted.

Nor should I seek for any other cause than this, if in some of these instances, and particularly this whereof we treat, the appearance had not been seen over a much greater part of the earth's surface than can be thus accounted for. It having in this last been visible from the west side of Ireland to the confines of Russia and Poland on the east, nor do we yet know its limits on that side, extending over at least thirty degrees of longitude; and in latitude, from about fifty degrees over almost all the north of Europe, and in all places exhibiting at the same time the same wonderous circumstances. Now this is a space much too wide to be shaken at any one time by the greatest of earthquakes, or to be affected by the perspiration of that vapour, which being included and wanting vent, might have occasioned the earth to tremble. Nor can we this way account for that remarkable particular attending these lights, of being always seen on the north-side of the horizon, and never to the south.

Therefore laying aside all hopes of being able to explain these things by the ordinary vapours or exhalations of the earth or wa. ters, we must have recourse to other sorts of effluvia of a much more subtle nature, and which perhaps may seem more adapted to bring about those wonderful and surprisingly quick motions we Such is the magnetical effluvia, whose atoms freely permeate the pores of the most solid bodies, meeting with no obstacle from the interposition of glass or marble, or even gold itself. Some of these, by a perpetual efflux, arise from the parts near the poles of the magnet, whilst others of the like kind of atoms, but

with a contrary tendency, enter in at the same parts of the stone, through which they freely pass; and by a kind of circulation surround it on all sides, as with an atmosphere, to the distance of some diameters of the body. This thing Descartes has endeavoured to explain (Princip. Philosoph. lib. iv.) by the hypothesis of the circulation of certain screwed or striate particles, adapted to the pores they are to enter.

But without inquiring how sufficient the Cartesian hypothesis may be for answering the several phænomena of the magnet: that the fact may be the better comprehended, we shall endeavour to exhibit the manner of the circulation of the atoms concerned therein, as they are exposed to view, by placing the poles of a ter. rella or spherical magnet on a plain, as the globe on the horizon of a right sphere; then strewing fine steel dust, or filings, very thin on the plain all round it, the particles of steel, on a continued gentle knocking on the underside of the plain, will by degrees conform themselves to the figures in which the circulation is per. formed. Hence it may appear how this exceedingly subtle matter revolves; and particularly how it permeates the magnet with more force and in greater quantity in the circumpolar parts, entered into it on the one side, and emerging from it on the other, under the same oblique angles: while in the .iniddle zone, near the magnet's equator, very few, if any, of these particles impinge, and those very obliquely.

Now by many and very evident arguments, it appears that our globe of earth is no other than one great magnet, or, if I may be allowed to alledge an invention of my own, rather two; the one in. cluding the other, as the shell includes the kernei; for so and not otherwise we may explain the changes of the variation of the magne tical needle but to our present purpose the result is the same. It suffices, that we may suppose the same sort of circulation of such an exceedingly fine matter to be perpetually performed in the earth, as we observe in the terrella; which subtle matter freely pervading the pores of the earth, and entering into it near its southern pole, may pass out again into the ether, at the same distance from the northern, and with a like force; its direction being still more and more oblique, as the dista ce from the poles is greater. To this we beg leave to suppose, that this subtle matter, no otherwise discovering itself but by its effects on the magnetic needle, wholly