Philosophical Transactions/Volume 29/Number 347/Lights seen in the Air

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Philosophical Transactions, Volume 29, No. 347 by Edmond Halley
An Account of the late ſurprizing Appearance of the Lights ſeen in the Air

V. An Account of the late ſurprizing Appearance of the Lights ſeen in the Air, on the ſixth of March laſt; with an Attempt to explain the Principal Phænomena thereof; As it was laid before the Royal Society by Edmund Halley, J. V. D. Savilian Profeſſor of Geom. Oxon, and Reg. Soc. Sect.

THE Royal Society having received Accounts from very many Parts of Great Britain, of the unuſual Lights which have of late appeared in the Heavens; were pleased to ſignify their Deſires to me, that I ſhould draw up a general Reaction of the Fact, and explain more at large some Conceptions of mine I had propoſed to them about it, as ſeeming to ſome of them to render a tollerable Solution of the very ſtrange and ſurprizing Phænomena thereof. The Deſires oi the Society having with me the force of Commands; I ſhall not decline the Task: only premiſing that if, in delivering the Etiology of a Matter ſo uncommon, never before ſeen by my ſelf, not fully deſcribed by any either of the Ancients or Moderns, I fail to answer their Expectation or my own Deſires; yet 'tis hoped a good Hiſtory of the Fact, deduced partly from my own Obſervations, and partly collected from the uniform Relations of credible Perſons, or from the Letters of ſuch, may not be unacceptable to the Curious; and may perhaps excite the Genius of ſome more able Meteorologiſt to a more ſatisſactory Enquiry. The Account of this Appearance take as follows.

On Tueſday the ſixth of March, ſt. vet. in the current Year 1716, (the Afternoon having been very ſerene and calm, and somewhat warmer than ordinary) about the Time it began to grow dark, that is much about 7 of the Clock. not only in London, but in all Parts of England, where the Beginning of this wonderful Sight was ſeen; out of what seemed a dusky Cloud, in the N. E. parts of the Heaven and ſcarce ten Degrees high, the Edges whereof were tinged with a reddiſh Yellow like as if the Moon had been hid behind it, there aroſe very long, luminous Rays or Streaks perpendicular to the Horizon, ſome of which ſeem'd nearly to aſcend to the Zenith. Preſently after, that reddiſh Cloud was swiftly propagated along, the Northern Horizon, into the N. W. and ſtill farther Weſterly; and immediately sent forth its Rays after the same manner from all Parts, now here, now there, they obſerving no Rule or Order in their riſing. Many of these Rays ſeeming to concur near the Zenith, formed there a Corona, or Image which drew the Attention of al1 Spectators; who according to their ſeveral Conceptions made very differing Reſemblances thereof; but by which compared together, thoſe that ſaw it not, may well comprehend after what manner it appeared. Some likened it to that Representation of Glory wherewith our Painters in Churches ſurround, the Holy Name of God. Others to thoſe radiating Starrs wherewith the Breaſts of the Knights of the moſt Noble Order of the Garter are adorned. Many compared it to the Concave of the great Cupolæ of St. Paul's Church, diſtinguiſht with Streaks alternately Light and obſcure and having in the middle a Spaceleſs bright than the reſt, reſembling the lantern. Whilſt others, to expreſs as well the Motion as Figure thereof, would have it to be like the Flame in an Oven reverberated and fouling against the arched Roof thereof: And ſome there were that thought it liker to that tremulous Light which is caſt against a Ceiling by the Beams of the Sun, reflected from the Surface of Water in a Baſon that's a little ſhaken; whoſe reciprocal vibrating Motion it very much imitated. But all agree that this Spectrum laſted only a few Minutes, and ſhow'd it ſelf variously tinged with Colours, Yellow, Red and a dusky Green: Nor did it keep in the ſame Place; for when firſt it began to appear, it was ſeen a little to the Northwards of the Zenith, but by degrees declining towards the South, the long Striæ of Light, which arose from all Parts of the Northern Semicircle of the Horizon, ſeemed to meet together, not much above the Head of Caſtor or the Northern Twin, and there ſoon diſappeared.

After the firſt Impetus of this aſcending Vapour was over the Corona we have been deſcribing appeared no more; but ſtill, without any order as to Time, or Place, or Size, luminous Radii like the former continued to ariſe perpendicularly, now oftner and again ſeldomer, now here, now there, now longer, now ſhorter. Nor did they proceed at first: out of a Cloud, but oftner would emerge at once out of the pure Sky, which was at that time more than ordinary ſerene and ſtill. Nor were they all of the ſame Form. Moſt of them ſeemed to end in a Point upwards, like erect Cones; others like truncate Cones or Cylinders, ſo much reſembled the long Tails of Comets, that at firſt light they might well betaken for ſuch. Again, ſome of theſe Rays would continue viſible for ſeveral Minutes; when others, and thoſe the much greater part, juſt ſhew'd themſelves and died away. Some ſeem'd to have little Motion, and to ſtand as it were fix'd among the Stars, whilſt other with a very perceptible Tranſlation moved from Eaſt to Weſt under the Pole, contrary to the Motion of the Heavens; by which means they would ſometimes ſeem to run together, and at other times to fly one another; affording therebya ſurprizing Spectacle to the Beholders.

After this Sight had continued about an Hour and a Half, thoſe Beams began to riſe much fewer in Number and not near ſo high, and by degrees that diffuſed Light, which had illuſtrated the Northern Parts of the Hemiſphere, ſeemed to ſubſide, and ſettling on the Horizon formed the Reſemblance of a very bright Crepuſculum: That this was the State of this Phenomenon, in the firſt Hours, is abundantly confirmed by the unanimous Conſent and concurring Testimony of several very worthy Persons no ways enclined to deceive. For by the Letters we have received from almoſt all the extream Parts of the Kingdom, there is found very little Difference in the Deſcription from what appeared at London and Oxford; unleſs that in the North of England, and in Scotland, the Light seemed somewhat stronger and brighter.

Hitherto I am forced to relate the Obſervations of others, wherein I fear many very material Circumſtances may be omitted: and aſſuredly I am not a little concern'd that I had no Notice of this Matter, till between Nine and Ten of the Clock, being at that Time at a Friends Houſe, and no ways ſuſpecting what past without Doors. But upon the firſt information of the thing, we immediately ran to the Windows, which hapned to regard the South and South-Weſt Quarter; and ſoon perceived, that though the Sky was very clear, yet it was tinged with a ſtrange ſort of Light; ſo that the ſmaller Stars were ſcarce to be ſeen, and much as it is when the Moon of four Days old appears after Twilight. And whilſt we regarded the Heavens with attention, we perceived a very thin Vapour to paſs before us, which aroſe from the preciſe Eaſt part of the Horizon, aſcending obliquely, ſo as to leave the Zenith about 15 or 20 Degrees to the Northward. But the ſwiftneſs wherewith it proceeded was ſcarce to be believed, ſeeming not inferiour to that of Lightning; and exhibiting, as it paſt on, a ſort of momentaneous Nubecula, which diſcovered it ſelf by a very diluted and faint Whiteneſs; and was no ſooner: formed, but before the Eye could well take ‘it, it was gone, aid left no Signs behind it. Nor was this a ſingle. appearance; but for ſeveral Minutes that we regarded: it, about ſix or ſeven times in a Minute, the ſame was again and again repeated; theſe Waves of Vapour (if I may be allowed to uſe the Word) regularly ſucceeding one another, and, as we gueſt, at intervals very nearly equal; all of them in their Aſcent producing a like tranſient Nubecula.

By this particular we were firſt aſſured, that the Vapour we ſaw, whatever it were, became conſpicuous by its own proper Light, without help of the Suns Beams: for theſe Nubecula did not diſcover themſelves in any other part of their paſſage, but only between the South-Eaſt, and South, where being oppoſite to the Sun they were deepeſt immerſt in the Cone of the Earths Shadow; nor were they viſible before or after. Whereas the contrary muſt have happened, had they borrowed their Light from the Sun.

We then made all the haſt we could to a place where there is a free Proſpect of the Northern Horizon. Being come there, net much paſt Ten of the Clock, we found, on the Weſtern Side, viz. between the W. and N. W. the Repreſentation of a very bright Twilight, contiguous to the Horizon; out of which there aroſe very long Beams of Light, not exactly erect toward the Vertex, but ſomething declining to the South, which aſcending by a quick and undulating Motion to a conſiderable Height, vaniſhed in a little time, whilſt others, tho’ at uncertain intervals, ſupply’d their Place, But at the ſame time through all the reſt of the Northern Horizon, viz, from the North-Weſt to the true Eaſt, there did not appear any ſign of Light to ariſe from, or joyn to, the Horizon; but on the contrary, what appeared to be an exceeding black and diſmal Cloud ſeem’d to hang over all that part of it. Yet was it no Cloud, but only the ſerene Sky more than ordinary pure and limpid, ſo that the bright Stars ſhone clearly in it, and particularly Cauda Cygni then very low in the North; the great Blackneſs manifeſtly proceeding from the Neighbourhood of the Light which was collected above it. For the Light had now put on a Form quite different from all that we have hitherto deſcribed, and had faſhioned it ſelf into the Shape of two Laminæ or Streaks, lying in a Poſition parallel to the Horizon, whoſe Edges were but ill terminated. They extended themſelves from the N. by E. to the North Eaſt, and were each about a Degree broad; the undermoſt about eight or nine Degrees high, and the other about four or five Degrees over it; theſe kept their Places for along time, and made the Sky ſo light, that I believe a Man might eaſily have read an ordinary Print by the Help thereof.

Whilft we ſtood aſtonifhed at this ſurprizing Sight, and expecting what was further to come, the Northern End of the upper Lamina by degrees bent downwards, and at length cloſed with the End of the other that was under it, ſo as to ſhut up on the Northſide an intermediate Space, which ſtill continued open to the Eaſt. Not long after this, in the ſaid included Space, we ſaw a great Number of ſmall Columns or whiyiſh Streaks to appear ſuddenly, erect to the Horizon, and reaching from the one Lamina to the other; which inſtantly diſappearing were too quick for the Eye, ſo that we could not judge whether they aroſe from the Under or fell from the Upper, but by their ſudden Alterations they made ſuch an Appearance, as might well be taken to reſemble the Conflicts of Men in Battle.

And much about the ſame time, to encreaſe our Wonder, there began on a ſudden to appear, low under the Pole and very near due North, three or four lucid Areas like Clouds, diſcovering themſelves, in the pure but very black Sky, by their yellowiſh Light. Theſe, as they broke out at once, ſo after they had continued a few Minutes, diſappeared as quick as if a Curtain had been drawn over them: Nor werethey of any determined Figure, but both in Shape and Size might properly be compared to ſmall Clouds illuminated by the full Moon, but brighter.

Not long after this, from above the aforeſaid two Laminæ, there aroſe a very great Pyramidal Figure, like a Spear, ſharp at the Top, whoſe Sides were inclined to each other with an Angle of about four or five Degrees, and which ſeemed to reach up to the Zenith or, beyond it. This was carried with an equable and not very ſlow Motion, from the N. E. where it aroſe, into the N. W. where it diſappeared, ſtill keeping in a perpendicular Sicuation, or very near it; and paſſing ſucceſſively over all the Stars of the Little Bear, did not efface the ſmaller ones in the Tail, which are but of the Fifth Magnitude; ſuch was the extream Rarity and Perſpicuity of the Matter whereof it conſiſted.

This ſingle Beam was ſo far remarkable above all thoſe that for a great while before had preceeded it, or that followed it, that if the Situation thereof among the Circumpolar Stars had at the ſame Inſtant been accurately noted, for Example, at London and Oxford, whoſe Difference of Longitude is well known, we might be enaabled thereby with ſome certainty to pronounce by its diverſitas Aſpectûs, concerning the Diſtance and Height thereof; which were undoubtedly very great, tho’ as yet we can no ways determine them. But as this Phænomenon found all thoſe that are skill’d in the Obſervation of the Heavens unprepared, and unacquainted with what was to be expected; ſo it left all of them ſurprized and aſtoniſhed at the Novelty thereof. When therefore for the future any ſuch thing ſhall happen, all thoſe that are curious in Aſtronomical Matters, are hereby admoniſhed and entreated to ſet their Clocks to the apparent Time at London, for Example, by allowing ſo many Minutes as is the Difference of Meridians; and then to note at the End of every half Hour preciſely, the exact Situation of what at that time appears remarkable in the Sky; and particularly the Azimuths of thoſe very tall Pyramids ſo eminent above the reſt, and therefore likely to be ſeen furtheſt: to the intent that by comparing thoſe Obſervations taken in the ſame Moment in diſtant Places, the Difference of their Azimuths may ſerve to determine how far thoſe Pyramids are from us.

It being now paſt Eleven of the Clock, and nothing new offering it ſelf to our View, but repeated Phaſes of the ſame Spectacle; we thought it no longer worth while to bear the Chill of the night-Air ſub dio. Wherefore being returned to my Houſe, I made haſte to my upper Windows, which conveniently enough regard the N. E. Parts of Heaven, and ſoon found that the two Laminæ or Streaks parallel to the Horizon, of which we have been ſpeaking, had now wholly diſappeared; and the whole Spectacle reduced it ſelf to the Reſemblance of a very bright Crepuſculum ſetling on the Northern Horizon, ſo as to be brighteſt and higheſt under the Pole it ſelf; from whence it ſpread both Ways, into the N. E. and N. W. Under this, in the middle thereof, there appeared a very black Space, as it were the Segment of a leſſer Circle of the Sphere cut off by the Horizon. It ſeemed to the Eye like a dark Cloud, but was not ſo; for by the Teleſcope the ſmall Stars appeared through it more clearly than uſual, conſidering how low they were; and upon this as a Baſis our Lumen Auroriforme reſted, which was no other than a Segment of a Ring or Zone of the Sphere, intercepted between two parallel leſſer Circles, cut off likewiſe by the Horizon; or, if you pleaſe, the Segment of a very broad Iris, but of one uniform Colour; viz. a Flame-colour inclining to yellow, the Center thereof being about forty Degrees below the Horizon. And above this there were ſeen ſome Rudiments of a much larger Segment, with an Interval of dark Sky between, but this was ſo exceeding faint and uncertain that I could make no proper eſtimate thereof.

I was very deſirous to-have ſeen how this Phænomenon would end, and attended it till near Three in the Morning, and the riſing of the Moon: but for above two Hours together it had no manner of Change in its Appearance, nor Diminution nor Encreaſe of light; only ſometimes for very ſhort Intervals, as if new Fuel had been caſt on a Fire, the Light ſeem’d to undulate and ſparkle, not unlike the riſing of vaporous Smoak 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 did by no means owe its Origine 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 follow’d him, but ended in that very Point where he then was: whereas in the true North, which the Sun had long paſt, the Light remained unchanged and in its full Luſtre.

Hitherto I have endeavoured by Words to repreſent what I ſaw, but being ſenſible how inſufficient ſuch a verbal Deſcription of a thing ſo extraordinary. and unknown may be to moſt Readers, I have thought fit to annex a Figure exhibiting that particular Appearance of the two Laminæ, which I ſaw at London between the Hours of Ten and Eleven: more eſpeciallv. becauſe I do one that has taken notice of it. In this Figure AB is the under Lamina, ſomewhat broader and brighter than the upper CD: it had near its under Edge the Lucida Lyre, and below its Northern Extremity,on the Left-hand, Cauda Cygni: and as well above and below theſe, as in the intermediate Space between them, and indeed all round about that Part of the Heavens, the Sky was ſo unuſually dark and black, as if all that exotick Light that had ſhew’d it ſelf before, had been then collected into thoſe two Streaks. Only at between the Weſt and Northweſt and no where elſe, out of a Brightneſs adjoining to the Horizon, there aroſe conical Beams as M, L, N, after the ſame manner as at firſt.

Whilſt we ſtood looking on, the Streak CD at its Northern End bent downward, and joyned with the Under AB at E, and included the Space DCEAB, which ſtill kept open at the other End towards the Eaſt. And in the mean time, out of the very clear Sky, fome luminous Spots, ſituated and figured as in the. Scheme at G, G, G, G, preſented themſelves to the Eye, in Colour much like the Laminæ. Thefe did not fhew themfelves all together, but came ſucceſſively, yet ſo as two or three of them were ſeen at a time; and as their coming was inſtantaneous, ſo they went away in a Moment. At the ſame time likewiſe, the ſeveral little white Columns marked F, F, F, F, occupied that Part of the. Space between the two Streaks next to E, and by their ſudden and very irregular Motion, and the vaniſhing of ſome whilſt others at the ſame time emerged, gave occaſion to the Conception of thofe that fancy’d Battles fought in the Air. Laſtly from about the middle of C D, there aroſe ſuddenly a Cone or Obelisk of a pale whitiſh Light, greater than any we had yet ſeen, as H; which moving from Eaſt to Weſt, with a Motion ſufficiently regular, was tranſlated to, in the North Weſt, and there diſappeared.

That we might by the ſame Scheme ſhew the Appearance of the laſt Hours, after Midnight; the Reader is deſired to take notice that we have made the Light at , much bigger than what appeared in the Weſt about Ten of the Clock; ſo as to repreſent truly that other. In this Caſe the Point muſt, by the Imagination, be ſuppoſed transferred to the Interſection of the Horizon and Meridian under the Pole. And that we might the better be underſtood in what follows, we have made this ſhort Recapitulation as annex’d to, and explicative of, the Scheme, which could by no means be contrived to anſwer the wonderful Variety this Phænomenon afforded; ſince even the Eye of no one ſingle Obſerver, was ſufficient to follow it in the Suddenneſs and Frequency of its Alterations.

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 ſurprizing Part thereof, which however frightful and amazing it might ſeem to the vulgar Beholder, would have been to me a moft agreeable and wiſh’d 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 hath not happen’d 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 One Hundred and Forty Years ago, 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 November that Year, much the ſame wonderful Phænomena were ſeen, with almoſt all the ſame Circumſtances as now. Nor indeed, during the Reign of that glorious Princeſs, was this ſo rare a Sight as it has been ſince. For we find in a Book entituled a Deſription of Meteors, reprinted at London in the Year 1654, whoſe Author writes himſelf W. F. D.D. that the ſame thing, which he there calls Burning Spears, was ſeen at London on Jannary 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 Medicine in the Univerfity of Lovain, and Son of Gemma Friſius the Mathematician. He, in a Diſcourſe he wrote of the Prodigies of thoſe Times, after ſeveral ill-boding Prognoſticks, thus very properly deſcribes the Cupola and Corona that he ſaw in the Chaſma (as he calls it) of February. Paulo paſt undecunque ſurgentibus Haftis & flammis novis, flagrarecalum à Borea parteuſque ad verticem videbatur: ac denique ne nihil qua contigerunt bactenus præfiguratum antea videretur, converſa eft Cæli facies, per boræ ſpatinum, in Fritilli aleatorii ſpeciem peregrinam; alternantibus ſeſe caruleo & candido, non minore vertigine motuſque celeritate, quam ſolares radii ſolent, quoties ab objecto ſpeculo regeruntur. Here it is not a little remarkable, that all theſe four already mentioned fell exactly upon the ſame Age of the Moon, viz. about two Days after the Change.

As to the other of September in the ſame Year 1575, theſe are the Words of Gemma. Minus quidem horrendum, ſed varia tamen magiſque conſula nobis apparuit alterius Chaſmatis forma, quarto Calendas Octobreis ſubſecuti, ſtatim ab occaſu Solis. Nam in illo viſi funt arcus illuſtres plurimi, ex quibus Haſtæ ſenſim eminentes, Urbeſque turritæ & Acies militares. Erant hine radiorum excurſus quaqnaverſum, & nubium fluctus & prælia: inſectabantur invicem & fugiebant, facta in orbem converſione mirabili, From hence ‘tis manifeſt that this Phænomenon appeared in our Neighbourhood three ſeveral Times, and that with conſiderable Intervals, within the Campaſs of one Year; though our Engliſh Hiſtorians have not recorded the two latter; nor did Gemma ſee that of November 1574, as ‘tis moſt likely by reaſon of Clouds. After this, in the Year 1580. we have the Authority of Michael Mæſtlin,[1] (himſelf a good Aſtronomer, and ſtill more famous for having had the honour to be the great Kepler’s Tutor in the Sciences) that at Baknang in the Country of Wirtemburg in Germany, theſe Chaſmata, as he likewife ſtiles them, were ſeen by himſelf no leſs than ſeven times within the Space of twelve Months. The firſt of theſe, and moft conſiderable, fell out on the very ſame Day of the Month with ours, viz. on Sunday the ſixth of March, and was attended with much the ſame Circumſtances, which, for Brevity's ſake, I omit. 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, neceſſarily 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 matters in thoſe Days.

The next in order that we hear of, was that of the Year 1621, on September the 2d. ſt. vet. ſeen all over France, and well deſcribed by Gaſſendus in his Phyſcks, who gives it the Name of Aurora Borealis. This, tho’ little inferiour to what we lately ſaw, and appearing to the Northwards both of Reuen 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 from home or abroad; notwithſtanding that for above half that time, theſe Philoſophical Tranſactions 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. Neve on the 16th of November 1707 of which ſeen Phil. Tranſ. No. 320., And in the Miſcellanea Berolinenſia publiſhed in 1710, we learn that in the ſame Year 1707, both on the 24th of January and 18th of February, ſt. ver. ſomething of this kind was ſeen by M. Olaus Römer at Copenhagen: and again on the 23d of February, the ſame excellent Aſtronomer obſerved there ſuch another Appearence, but much more conſiderable; of which yet he only ſaw the Beginning, Clouds interpoſing. But the ſame was ſeen that Night by Mr. Gotfried Kirch, at Berlin above 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 Ninth and Tenth of Auguſt 1708, by the Right Reverend 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 with great Intervals, diſpoſed to produce this Phænomenon: 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 Moon-ſhine: yet that it ſhould be ſo very often ſeen at ſome times and ſo ſeldom at others, is what cannot well be that way accounted for. Wherefore caſting about and conſidering what might be moſt probably the Material Canſe of theſe Appearances; what firſt occurr’d wasthe Vapour of Water rarified exceedingly by ſubterrancous Fire, and tinged with ſulfureous Steams; which Vapour is now generally taken by our 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 openit ſelf a Paſſage by rending it. And as theſe Vapours are ſuddenly produced by the Fall of Water upon the nitro-ſulphurous Fires 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 Gun-powder, when heated in Vacuo, to ſhine in the Dark, and aſcend to the Top of the Receiver though exhauſted: the Experiment of which I ſaw very neatly performed by Mr. F. Whitefide Keeper of Ambmole’s Muſeum in Oxford.

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 that 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 almoft all the North of Europe; and ia all Places exhibiting at the ſame time the ſame wonderous Circumſtances, as we are informed by the Publick News. 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 Perſbiration 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 Northſide of the Horizon, and never to the South.

Wherefore laying aſide all hopes of being able to explain theſe Things by the ordinary Vapours or Exhalations of the Earth or Waters, we are forced to have recourſe to other ſorts of Effuvia of a much more ſubtile Nature, and which perhaps may ſeem more adapted to bring about thoſe wonderful and ſurprizingly quick Motions we have ſeen. Such are the Magnetical Effuvia, whofs Atoms freely permeate the Pores of the moſt ſolid Bodies, meeting with no Obſtacle from the Interpoſition of Glaſs or Marble or even Gold it ſelf. Theſe by a perpetual Efflux do, ſome of them, 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 des Cartes has endeavoured to explain (Princip. Philoſoph. Lib IV.) by the Hypotheſis of the Circulation of certain skrewed or ſtriate Particles, adapted to the Pores they are to enters

But without enquiring 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 Terreila or Spherical Magnet on a Plane, as the Globe on the Horizon of a Right Sphere: Then threwing fine Steel duſt or Filings very thin on the Plain all round it, the Particles of Steel, upon a continued gentle knocking on the underſide of the Plain, will by degrees conform themſelves to the Figures in which the Circulation is performed. Thus in Fig. II. Let ABCD be a Terrella, and its Poles A the South, and B the North; and by doing as preſcribed, it will be found that the Filings will lie in a Right Line perpendicular to the Surface of the Ball, when in the Line of the Magnetical Axis continued. But for about forty five Degrees on either ſide, from B to G or I, and from A to H or K, they will form themſelves into Curves, more and more crooked as they are remoter from the Poles; aad withall more and more oblique to the Surface of the Stone: as our Figure truly repreſents, and as may readily be ſhewn by the Terrella and Apparatus for that Purpoſe in the Repoſitory of the Royal Society Hence it may appear how this exceeding ſubtile Matter revolves; and particularly how it permeates the Magnet with more force and in greater Quantity in the circumpolar Parts, entring into it on the one ſide, and emerging from it on the other, under the ſame oblique Angles: whilſt in the middie Zone about C and D, near the Magnet’s Equator (if I may uſe the Word) very few if any of theſe Particles do 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 | may be allowed to alledge an Invention of my own) rather two; the one including the other as the Shell includes the Kernel (for ſo and not otherwiſe we may explain the changes of the Variation of the Magnetical 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 exceeding fine Matter to be perpetually performed in the Earth, as we obſerve in the Terella; which ſubtile Matter freely pervading the Pores of the Earth, and entring into it near its Southern Pole, may paſs out again in to the Ether, at the ſame Diſtance from the Northern, and with a like Force; its Direction being ſtill more and more oblique, as the Diſtance from the Poles is greater. To this we beg leave to ſuppoſe, that this ſubtile Matter, no otherways diſcovering it ſelf but by its Effects on the Magnetick Needle, wholly imperceptible and at other times inviſible, may now and then, by the Concourſe of ſeveral Cauſes very rarely coincident, and to us as yet unknown, be capable of producing a ſmall Degree of Light; perhaps from the greater Denſity of the Matter, or the greater Velecity of its Motion: after the ſame manner as we ſee the Affluvia of Electrick Bodies by a ſtrong and quick Friction emit Light in the Dark: to which ſort of Light this ſeems to have a great Affinity.

This being allowed me, I think we may readily aſſign a Cauſe for many of the ſtrange Appearances we have been treating of, and for ſome of the moſt difficult to account for otherwiſe; as why theſe Lights are rarely ſeen any where elſe but in the North and never, that we hear of, near the Equator: as alſo why they are more frequently ſeen in Iceland and Groenland, than in Norway, though nearer the Pole of the World. For the Magnetical Poles, in this Age, are to the Weſtward of our Meridian, and more ſo of that of Norway, and not far from Groenland; as appears by the Variation of the Needle this Year obſerved, full twelve Degrees at London to the Weſt.

The erect Poſition of the luminous Beams or Striæ ſo often repeated that Night, was occaſioned by the riſing of the Vapour or lucid Matter nearly perpendicular to the Earth’s Surface. For that any Line erected perpendicularly upon the Surface of the Globe, will appear erect to the Horizon of an Eye placed any where in the ſame ſpherical Superſicies; as Euclid demonſtrates in a Plain, that any Line erected at Right Angles to it, will appear to be perpendicular to that Plain from any Point thereof, That it ſhould be ſo in the Sphere is a very pretty Propoſition, not very obvious, but demonſtrated from Prop. 5. Lib. I. Theodoſii Spharic. For by it all Lines erect on the Surface paſs through the Center, where meeting with thoſe from the Eye, they form the Plains of Vertical Circles thereto. And by the Converſe hereof it is evident, that this luminous Matter aroſe nearly perpendicular to the Earth’s Surface, becauſe it appeared in this erect Poſition. And whereas in this Appearance (and perhaps in all others of the Kind) thoſe Beams which aroſe near the Eaſt and Weſt, as L, M, N, were furtheſt from the Perpendicular, on both ſides inclining towards the South, whilſt thoſe in the North were directly upright: the cauſe thereof may well be explained by the Obliquity of the Magnetical Curves, making ſtill obtuſer Angles with the Meridians of the Terrella, as they are further from its Poles.

Hence alſo it is manifeſt how that wonderful Corona that was ſeen to the Southwards of the Vertex, in the Beginning of the Night, and ſo very remarkable for it’s tremulous and vibrating Light, was produced; to wit, by the Concourſe of many of thoſe Beams arifing very high out of the circumjacent Regions, and meeting near the Zenith: the Effluvia whereof they conſiſted mixing and interfering one with another, and thereby occaſioning a much ſtronger but uncertain wavering Light. And ſince it is agreed by all our Accounts that this Corona was tinged with various Colours, ‘tis more than probable that theſe Vapours were carried up to ſuch a Height, as to emerge out of the Shadow of the Earth, and to be illuſtrated by the direct Beams of the Sun: whence it might come to paſs that this firſt Corona was ſeen coloured and much brighter than what appeared afterwards in ſome Places, Where the Sight thereof was more than once repeated, after the Sight was gone down much lower under the Horizon. Hence alſo it will be eaſily underftood that this Corona as net one and the ſame in all Places, but was different in every differing Horizon; exactly after the ſame manner as the Rainbow ſeen in the ſame Cloud is not the ſame Bow, but different to every ſeveral Eye.

Nor is it to be doubted, but the Pyramidical Figure of theſe Aſcending Beams is Opticall: ſince according to all likelyhood they are parallel-ſided, or rather taporing the otherway. But by the Rules of Perſpective, their Sides ought to converge to a Point, as we ſee in Pictures the Parallcl Borders of ſtreight Walks, and all other Lines parallel to the Axis of Viſion, meet as in a Center. Wherefore thoſe Rays which aroſe higheſt above the Earth and were neareſt the Eye, ſeemed to terminate in Cuſps ſufficiently acute, and have been for that reaſon ſuppoſed by the Vulgar to repreſent Spears. Others ſeen from afar, and perhaps not riſing fo high as the former, would terminate as if cut off with Plains parallel to the Horizon, like truncate Cones or Cylinders: theſe have been taken to look like the Battlements and Towers on the Walls of Cities fortified after the ancient manner. Whilſt others yet further off, by reaſon of their great Diſtance, good part of them being intercepted by the Interpofition of the Convexity of the Earth, would only ſhew their pointed Tops, and becauſe of their Shortneſs have gotten the Name of Swords.

Next the Motion of theſe Beams, furniſhes us with a new and, as it ſeems to me, moſt evident Argument to prove the diurnal Rotation of the earth: (though that be a matter which, at preſent, is generally taken by the Learned to be paſt diſpute) For thoſe Beams which rise up to a Point, and did not preſently diſappear, bat continued for ſome time, had moſt of them a ſenſible Motion, from Eaſt to Weſt, contrary to that of the Heavens; the biggeſt and talleſt of them, as being neareſt, ſwifteſt; and the more remote and ſhorter, ſlower. By which means, the one overtaking the other, they would times ſeem to meet and joſtie ; and at other times to ſeparate, and fly one another. But this Motion was only Optical, and occaſioned by the Eye of the Spectator being carried away with the Earth in to the Eaſt; whilſt the exceeding rare Vapour of which thoſe Beams did conſiſt, being, as I take it, railed far above the Atmoſphere, was either wholly left behind, or elſe followed with but part of its Velocity, and therefore could not but ſeem to recede and move the contrary Way. And after the ſame manner as the Stars that go near the Zenith, paſs over thoſe Vertical Circles which border on the Meridian, much ſwifter than thoſe Stars which are more diſtant therefrom; ſo theſe luminous Rays would ſeem to recede faſter from Eaſt ro Weſt, as their Baſes were nearer the Eye of the Spectator; and è contra, flower as they were further off.

Nor are we to think it ſtrange, if after ſo great a Quantity of luminous Vapour had been carried up into the Ether out of the Pores of the Earth, the Cauſe of its Efferveſcence at length abating, or perhaps the Matter thereof conſumed; theſe Effluvia ſhould at length ſubſide, and form thoſe two bright Laminæ which we have deſcribed, and whoſe Edges being turn’d to us were capable to emit ſo much Light that we might read by them. I chooſe to call them Laminæ, becauſe, without doubt, though they were but thin, they ſpread Horizontally over a large Tract of the Earth Surface. And whilſt this luminous Matter dropt down from the upper Plate to the under, the many little white Columns were formed between them by its Deſcent, only viſible for the Moment of their Fall. Theſe by the Swiftneſs with which they vaniſhed and their great Number, ſhewing themſelves and diſappearing without any order, exhibited a very odd Appearence; thoſe on the Right ſeeming ſometimes to drive and puſh thoſe on the left, and vice verſa.

I have been obliged to omit ſeveral Particulars of leſs moment: But theſe are the principal Phænomena; of whoſe Cauſes I ſhould have more willingly and with more certainty given my Thoughts, if I had had the good luck to have ſeen the whole from Beginning to end; and to have added my own Remarks to the Relations of others; and eſpecially if we could by any means have come at the Diſtances thereof. If it ſhall by any be thought a hard Suppoſition that I aſſume the Effluvia of the Magnetical Matter for this purpoſe, which in certain Caſes may themſelves become luminous, or rather may ſometimes carry with them out of the Bowels of the Earth a ſort of Atoms proper to produce Light in the Ether. I anſwer that we are not as yet informed of any other Kinds of Effluvia of terreftrial Matter which may ferve for our purpoſe, than thoſe we have here conſidered, viz. the Magnetical Atoms, and thoſe of Water highly rarified into Vapour. Nor do we find any thing like it in what we ſee of the Celeſtial Bodies, unleſs it be the Effluvia projected out of the Bodies of Comets to a vaſt Height, and which ſeem by a Vis centrifuga to fly with an incredible Swiftneſs the Centers both of the Sun and Comet, and to go off into Tails of a ſcarce conceivable Length. What may be the Conſtitution of theſe Cometical Vapours, we Inhabitants of the Earth can know but little, and only that they are evidently excited by the Heat of the Sun; whereas this Meteor, if I may ſo call it, ſeldom is ſeen but in the polar Regions of the World, and that moſt commonly in the Winter Months. But whatever may be the Cauſe thereof, if this be not. I have followed the old Axion of the Schools. Entia non eſſe temere nique abſque neciſſitate multiplicanda.

Laſtly I beg leave on this Occaſion to mention what, near 25 Years ſince, I publiſh’d in No 95. of theſe Tranſactions, viz. That ſuppoſing the Earth to be concave, with a leſſer Globe included, in order to make that inner Globe capable of being inhabited, there might not improbably be contained ſome luminous Medium between the Balls, ſo as to make a perpetual Day below. That very great Tracts of the Etherial Space are occupied by ſuch a ſhining Medium is evident from the Inſtances given in the firſt Paper of this Tranſaction: And if fuch a Medium ſhould be thus incloſed within us; what ſhould hinder but we may be allowed to ſuppoſe that ſome parts of this lucid Subſtance may, on very rare and extraordinary Occaſions, tranſude through and penetrate the Cortex of our Earth, and being got looſe may afford the Matter whereof this our Meteor conſiſts. This ſeems favoured by one conſiderable Circumſtance, viz. that the Earth, becauſe of its diurnal Rotation, being neceſſarily of the Figure of a Flat Spheroid, the thickneſs of the Cortex, in the Polar Parts of the Globe, is conſiderably leſs than towards the Equator; and therefore more likely to give Paſſiage to theſe Vapours; whence a reaſon may be given why theſe Lights are always ſeen in the North. But I deſire to lay no more ſtreſs upon this Conceit than it will bear.

It having been noted that in the Years 1575 and 1580, wherein this Appearance was frequent, that it was ſeen not far from the Times of the two Equinoxes; it may be worth while for the Curious, to beſtow ſome Attention on the Heavens in the Months of September and October next; and in caſe it ſhould again happen, to endeavour to obſerve, by the Method I have here laid down, what may determine, with ſome degree of Exactneſs, the Diſtance and Height thereof; without which we can ſcarce come to any juſt Concluſion.


FINIS.

Errata, No. 346. p. 383. l. 18. read 234. p. 408, l., 20,
read, proceed, as at firſt.

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Plate II


Philoſ. Tranſact. No 347

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  1. M. Mæſtlin. lib, de Cometa; 1580.