SECTION II.

Account of surprising Tights in the Air, March 6, 1716; with an attempt to explain their principal Phenomena.

By Edmund Halley, J.V.D. Savilian Professor of Geometry, Oxon, and Secretary to the Royal Society.

ON Tuesday, March 6, O. S. 1716, the afternoon having been very serene and calm, and somewhat warmer than ordinary, about seven o'clock, out of what seemed a dusky cloud, in the N.E. parts of the heaven, and scarcely ten degrees high, the edges of which were tinged with a reddish yellow, as if the moon had been hid behind it, there arose very long luminous rays or streaks, perpendicular to the horizon, some of which seemed nearly to ascend to the zenith. Presently after, that reddish cloud was swiftly propagated along the northern horizon, into the N. W. and still far. ther westerly; and immediately sent forth its rays after the same manner from all parts, now here, now there, 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 at tention of all spectators, who according to their several conceptions made very differing resemblances of it; but by which compared together, those that saw it not may well comprehend after what manner it appeared. All agree that this spectrum lasted only a few minutes, and showed itself 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 northward of the zenith; but gradually declining toward 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 the time, or place, or size, luminous radii like the former continued to arise perpendicularly. Nor did they proceed as at first, out of a cloud, but oftener would emerge at once out of the pure sky, which was at that time more than ordinary se.

rene 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 truncated cones or cylinders, so much resembled the long tails of comets, that at first sight they might well be taken for such. Again, some of these rays would continue visible for several minutes; when others, and those the much greater part, just shewed themselves, and died away. Some seemed to have little motion, and to stand as it were fixed among the stars, while others 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 a surprising spectacle to the beholders.

After this sight had continued about an hour and a half, the beams began to rise much fewer in number, and not near so high, and gradually 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. On the first information of the thing, I immediately ran to the windows, which happened to look to 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 scarcely to be seen, and much as it is when the moon of four days old appears after twilight. We perceived a very thin vapour pass before us, which arose from the precise east part of the horizon, ascending obliquely, so as to leave the zenith about fifteen or twenty degrees to the northward. But the swiftness with which it proceeded was scarcely to be believed, seeming not inferior to that of lightning; and exhibiting as it passed on a sort of momentaneous nubecula, which discovered itself by a very diluted and faint whiteness; and was no sooner formed, but before the eye could well take it, it was gone, and left no signs behind it. Nor was this a single appearance; but for several minutes, about six or seven times in a minute, it was again and again repeated; these waves of vapour, if I may so call it, regularly succeeding one another, and nearly at equal intervals; 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 was, became conspicuous by its own proper light, without help of the sun's beams; for these nubecula did not disco

ver 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 immersed in the cone of the earth's shadow, nor were they visible before or after. Whereas the contrary must have hap. pened, had they borrowed their light from the sun.

A little after ten o'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 some. thing declining to the south, which ascending by a quick and undu. lating motion to a considerable height, vanished in a little time; while others, though at uncertain intervals, supplied 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 sight of light to arise from, or join to, the horizon; but on the contrary, what appeared to be an exceedingly black and dismal cloud seemed to hang over all that part of it. Yet it was 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 itself into the shape of two lamina or streaks, lying in a position parallel to the horizon, whose edges were but ill terminated. They extended them. selves from the N. by E. to the north east, and were much 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 a long time, and made the sky so light, that I believe a man might easily have read an ordinary print by it.

While we stood astonished at this surprising 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 north side 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 whitish streaks to appear suddenly, erect, to the horizon, and reaching from 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 increase 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. They were of no determined figure, but both in shape and size might properly be compared to small clouds illumi nated by the full moon, but brighter.

Not long after this, from above the aforesaid two laminæ, there arose a very great pyramidical 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 ze. nith, 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 a perpendicular situation, 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 extreme rarity and perspicuity of the matter it consisted of.

This single beam was so far remarkble above all those that for a great while before had preceded it, or that followed it, that if its situation 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 enabled with some certainty to pronounce, by its diversitas aspectú, concerning its distance and height; which was doubtless very great, though as yet we can no wise determine them. But as this phenomenou found all those that are skilled in the observation of the heavens unprepared, and unacquainted with what was to be expected; so it left them all surprised and astonished at its novelty. 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 me.

ridians, 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 farthest ; that by comparing those observations taken at the same moment in distant places, the difference of their azimuths may serve to deter mine how far those pyramids are from us.

It being now past 11 o'clock, and nothing new offering itself 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. Therefore returning to my house, I made haste to my upper win. dows, which conveniently enough look to the N.E. parts of hea ven, 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 itself to the resemblance of a very bright crepusculum, settling on the northern horizon, so as to be brightest and highest under the pole itself; from whence it spread both ways, into the N.E. and N. W. Under this, in the middle of it, 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 on this as a basis our lumen auroriforme rested, which was 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, its centre 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 exceedingly faint and uncertain, that I could make no pro. per estimate of it.

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 increase of light: only sometimes for very short intervals, as if new fuel had been cast on a fire, the light seemed to undulate and sparkle, not unlike