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only shew their pointed tops, and because of their shortness have been called swords.

Next, the motion of these beams furnishes us with a new, and 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 rose up to a point, and did not presently disappear, but continued for some time, had most of them a sensible motion from east to west, contrary to that of the heavens ; the largest 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 sometimes seem to meet and jostle ; 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 into the east; while the exceedingly rare vapour which those beams consisted of, being raised far above the atmos. phere, 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 from it; so these luminous rays would seem to recede faster from east to west, as their bases were nearer the eye of the spectator; and è contra, slower as they were further off.

Nor are we to think it strange, if after so great a quantity of luminous vapour bad 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 consumed, these effluvia should at length subside, and form those two bright luminations which we have de. scribed; and, whose edges being turned to us, were capable to emit so much light that we might read by them. I choose to call them luminations, because, though they were but thin, doubtless they spread horizontally over a large tract of the earth's surface. And while this luminous matter dropped down from the upper plate to the under, the many 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,

any

exhibited a very odd appearance; those on the right seeming sometimes to drive and push those on the left, and vice versa.

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 their distances. If it shall by any be thought a bold supposition, that I assume the efluvia of the magnetical matter for this pur. pose, 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 an. swer, that we are not as yet informed of any other kinds of effluvia of terrestrial matter which may serve for our purpose, than those we have here considered, viz. the magnetical atoms, and those of water highly rarefied into vapour. Nor do we find 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 swift. ness, the centres both of the sun and comet, and to go off into tails of a scarcely conceivable length. What may be the consti. tution of these cometical vapours, we the 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, is seldom een except in the polar regions of the world, and that most commonly in the winter months. But whatever may be the cause of it, if this be not, I have followed the old axiom of the schools, Entia non esse temere neque absque necessitate multis plicanda.

Lastly, I beg leave on this occasion to mention what, near 25 years since, I published in No. 195 of these Transactions, viz. That supposing the earth to be concave, with a less globe included, in order to make that inner globe capable of being inhabited, there might not improbably be contained some luminous medium be. tween 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 such a medium should be thus inclosed within us; why may we not be allowed to suppose that some parts of this lucid substance may, on very rare and extraordinary occa. sions, transude through and penetrate the cortex of our earth, and being got loose may afford the matter of which this our me. teor 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 passage 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 on this conceit than it will bear.

It having been noted that in the years 1575 and 1580, when this appearance was frequent, that it was seen not far from the lines 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 de. termine, with some degree of exactness, its distance and height; without which we can scarcely come to any just conclusion.

[Phil. Trans. 1716.

SECTION III.

Observations on the Lumen Boreale, or Streaming, Oct. 8,

1726.

By the Rev. W. Derham, F.R.S.

Tuere are two sorts of streamings, which have been noticed; one, by way of explosion from the horizon; the other, by open. ing and shutting, without shootings up, and swift dartings. Of the latter sort chiefly was that of October 8, 1726, in which, although the streams or spires, or lances, or cones, or whatever else they inay be called, were as large and remarkable as in the year 1715.6; yet they exhibited themselves principally by the vaporous matter opening and shutting, as if a curtain had been drawn and withdrawn before them. It began about eight o'clock, and soon streamed all round in the south, east and west, as much, or nearly as much, as in the north ; which was a thing not observed before in these phænomena.

These streams, or cones, were mostly pointed, and of different length, so as to make the appearance of flaming spires or pyramids; some again were truncated, and reached but half way: some had their points reaching up to the zenith, or near it, where they formed a sori of canopy, or thin cloud, sometimes red, sometimes brownish, some. times blazing as if on fire, and sometimes emitting streams all round it. This canopy was manifestly formed by the matter car. ried up by the streaming on all parts of the horizon. This some. times seemed to ascend with a force, as if impelled by the impetus of some explosive agent below, like that of March 1715-16. This forcible ascent of the streaming matter, gave a motion to the ca. nopy, sometimes a gyration, like that of a whirlwind; which was manifestly caused by the streams striking the outer parts of the canopy. But if it struck the canopy in the middle, all was then in confusion.

These two particulars, namely, the streaming all round, in all points of the horizon ; and the canopy in and near the zenith, are what were observed in all parts of England. But in the more southerly parts of Europe, it seems to have been somewhat different, by the accounts from different places.

One thing observed in most places was, that in some part of the greatest streaming, the vapours between the spires, or lances, were of a blood-red colour; which gave those parts of the atmosphere the appearance of blazing lances, and bloody-coloured pillars. There was also a strange commotion among the streams, as if some large cloud, or other body, was moving behind them, and disturbed them. In the northerly and southerly parts the streams were perpendicular to the horizon; but in the intermediate points they seemed to decline more or less one way or other; or rather to in. cline towards the meridian.

As for the cause of these phænomena, Mr. Derham takes it to be from the same matter, or vapours, which produce earthquakes : and that for these reasons : First, because some of these phæno. mena have been followed by earthquakes. As that which Stow gives an account of in his Annals, in the year 1574, on Nov.14; in which he says, “ were seen in the air strange impressions of fire and smoke to proceed forth of a black cloud in the nortb towards the south. That the next night following, the heavens from all parts did seem to burn marvellous ragingly, and over our heads the flames from the horizon round about rising did meet, and there double and roll one in another, as if it had been in a clear fur. nace.” And after this, he says followed, on the 26th of February, great earthquakes in the cities of York, Worcester, Gloucester, Bristol, Hereford, and in the countries about, which caused the people to run out of their houses, for fear they should have fallen on their heads. In Tewksbury, Breedon, &c. the dishes fell from the cupboards, and the books in men's studies from the shelves, &c.

So this last, in October, was preceded by that fatal carthquake at Palermo in Sicily, and succeeded by one in England, on Tues. day, October 25, following. This it seems was perceived in London, and was very considerable at Dorchester, Weymouth, Portland, Portsmouth, Purbeck, and several other places in Dorsetshire, that it caused the doors to fly open, shook down pewter off the shelves, and was felt in some ships that lay in the harbours.

Another reason is, that some gentlemen viewing this appearance, on the tops of their houses at Little Chelsea, plainly perceived a sulphurous smell in the air. Another thing which concurs with what has been said, is, that several persons heard a hissing, and in some places a crackling noise, in the time of the streaming, like what is reported to be often heard in earthquakes.

[Id. 1727

SECTION IV.

Collection of the Observations of the remarkable Red Lights shexon in the dir, Dec. 5, or 16, N.S. sent from different pla es to the Royal Society.

As observed at Naples by the Prince of Cassano, F.R.S. Dec. 16, 1737, N.S. in the evening, the sun being about 25 de. grees below the horizon, a light was observed in the north, as if the air was on fire, and flashing; the intenseness of which gradually increasing, at the 3d hour of the night it spread much westward. Its greatest height was about 65°; for it occupied the whole extent of both the Bears and the polar star; yet at the sides it was not so high ; for in some places near the north it rose only to 50°, and it gradually diminished, so as to become insensible at the true horizon.

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