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observation to compare with it, in order to determine more nicely the perpendicular altitude there. At Oxford this nubecula was found to be 3° above the middle star of Orion's girdle, at 8h. 3m. and was therefore 2010 above the horizon; and the distance between Oxford and Tiverton being 1° 55', or 115 geographical miles, it will be as the sine of 61° 35' is to the sine of 65° 30, so is the semi-diameter of the earth, or 3437 such mites, to 3498 miles, the distance of the meteor from the centre of the earth ; from which deducting the semi-diameter, there remains 60% geographical miles, for the height of the meteor above Tiverton. And this is confirmed by the observation of the Rev. Mr. William Derhamn, who at Windsor saw the aforesaid nubecula about two degrees above the most southern of the seven stars in the shield of Orion; that is (the time being 8h. 6m.) in the altitude of 231°: whence, the distance between Tiverton and Windsor being 150 measured miles, or 130 geographical, by a like proportion we shall find the same height of the meteor 60 such miles, wanting only one quarter. So that in a round number, we may conclude it to have been just 60 geographic, or 69 statute miles, above the earth's surface. It is impossible to come at a precise determination of this matter; by reason of the course. ness and inaccuracy of the data, which were only the notes of per. sons under the surprise of the suddenbess of the light, and no ways pretending to exactness; however, such as they are, they abun. dantly evince the height to have exceeded 60 English miles, though some would have it to be no more than 38 or 40.
I was unwilling to leave off, till I had pitched on some hypothesis that might subject the motion of this meteor to a calculus; that the curious might be able to compute its visible way, either in respect of the horizon, or among the fixed stars : this I found might be done with tolerable exactness, supposing that it moved in the arch of a circle concentric with the earth, and 60 geographical miles without it; and that the point of the first explosion was over the lat. of 50° 40', and 3° 40' to the west of London; and that of the last extinction over lat. 47° 40', with 4° 50' west longitude; the time being fixed to eight minutes past eight at London. Hence it will be easy, by a trigonometrical process, to obtain the visible altitude and azimuth of the meteor at either of its explosions, as seen from any place whose longitude and latitude is known; and from the time given, the points in the sphere of stars answering to those azimuths and altitudes are readily deduced. And let those who contend for a much less beight of this meteor, try if they can, on such their supposition, to reconcile the several phænomena with one another, and with the observation of the Rev. Mr. William Ella, rector of Rampton in Nottinghamshire, between Gainsborough and Redford, which for its exactness I must not omit. Here, at 8h. 5m. the meteor was seen to pass precisely in the middle between Sirius and the fore foot of Canis Major, moving obliquely to the southward, in a line whose direction seemed to be from the middle between the two shoulders of Orion; the latitude of the place being nearly 53° 20, and long. west from London 0° 45'. Let them try how they can account for its being seen five degrees high at Aberdeen in Scotland, and near as much at Peterhead, half a degree more northerly: and then they will be better able to judge wbether it did not exceed the reputed limits of our atmosphere. Lastly, if the apparent altitude of the meteor at Paris was not five degrees and a half, but eleven, on the W. by N. point, when it must have been in its greatest lustre, there will be no pretence to bring it lower than I bave made it; especially if it be allowed to have followed the track I have assigned it, over Presteigu, Cardiff, Minehead, Tiverton, and Brest in Bretany.
Allowing this to have been the path it moved in, it would be easy to assign the real magnitude and velocity of this meteor, if the several accounts of its apparent diameter, and of the time of its passage from one of its explosions to the other, were consistent among themselves. But some of them making its visible appearance nearly equal to the sun's, wbich in the opinion of many it far es. ceeded, we may suppose with the least that, at the time when it first broke out over Tiverton, its diameter was half a degree; and its horizontal distance being 150 geographical miles from London, and its altitude 60, the hypothenusal, or real distance from the eye, will be more than 160 such miles; to which radius the subtense of half a degree will be above an English mile and half, being about 2800 yards nearly. After the same manner it is difficult to assign its due velocity, while some make it half, others less than a quarter, of a minute, in passing from its first explosion to its last extinction : but the distance it moved in that time being about three degrees, or 180 geographical miles, we may modestly compute it to have run above 300 such miles in a minute; which is a swiftness wholly incredible;
and such, that if a heavy body were projected horizontally with the same, it would not descend by its gravity to the earth, but would rather fly off, and move round its centre in a perpetual orbit like that of the moon.
Of several accidents that were reported to have attended its pase sage, some were the effect of pure fancy; such as the hearing it hiss as it went along, as if it had been very near at hand; some imagined they felt the warmth of its beams; and others thought they were scalded by it. But what is certain, and no way to be disputed, is the wonderful noise that followed its explosion. All accounts from Devon and Cornwall, and the neighbouring counties, are unanimous, that there was heard there, as it were, the report of a very great cannon, or rather of a broadside, at some distance, which was soon followed by a rattling noise, as if many small-arms had been promis. cuously discharged. What was peculiar to this sound was, that it was attended with an uncommon tremour of the air, and every where in those counties, very sensibly shook the glass-windows and doors in the houses, and according to some, even the houses them. selves, beyond the usual effect of cannon, though near; and Mr. Cruwys, at Tiverton, on this occasion, lost a looking-glass, which being loose in its frame, fell out on the shock, and was broken, We do yet know the extent of this prodigious sound, which was heard, against the then easterly wind, in the neighbourhood of Lon: don; and by the learned Dr. Tabor, who distinctly heard it beyond Lewes in Sussex : so that I cannot help thinking, that such a me. teor as this might have occasioned that famous ode of Horace : Parcus deorum cultor, &c.
Egit equos volucremque currum,
But whether the report heard near Lewes was of that explosion right over Devonsbire, or rather of that latter, and much greater at the extinction over Bretany, I shall not undertake to determine, till we have some further accounts from France, and more satisfactory information to build upon. It remains to attempt something towards a solution of the un
common phænomena of this meteor; and by comparing them with things more familiar to us, to shew at least how they might possibly be effected. Aud first, the unusual and continued heats of the last summer in these parts of the world, may well be supposed to have excited an extraordinary quantity of vapour of all sorts; of which the aqueous, and most others, soon condensed by cold, and wanting a certain degree of specific gravity in the air to buoy them op, ascend but to a small height, and are quickly returned in raio, dews, &c. whereas the inflammable sulphurous vapours, by an innate levity, have a sort of vis centrifuga, and not only have no need of the air to support them, but being agitated by heat, will ascend in vacuo Boileano, and sublime to the top of the receiver, when most other fumes fall instantly down, and lie like water at the bottom. By this we may comprehend how the matter of the meteor might have been raised from a large tract of the earth's surface, and ascend far above the reputed limits of the atmosphere ; where, being disengaged from all other particles, by that principle of nature that congregates homogenia, visible in so many instances, its atoms might in length of time coalesce and run together, as we see salts shoot in water, and gradually contracting theniselves into a narrower com. pass, mnight lie like a train of gunpowder in the ether, till catching fire by some internal ferment, as we find the damps in mines frequently do, the fame would be communicated to its continued parts, and so run on like a train fired.
This may explain how it came to move with so ipconceivable a ve. locity: for, if a continued train of powder were no larger than a barrel, it is not easy to say how very fast the fire would fly along it; much less can we imagine the rapidity of the ascension of these inore inflammable vapours, lying in a train of so vast a thickness. If this were the case, as it is highly probable, it was not a globe of fire that ran along, but a successive kindling of new matter : and as some parts of the earth might emit these vapours more copiously than others, this train might, in some parts thereof, be much denser and larger than in others, which might occasion several smaller explo. sions, as the fire ran along it, besides the great ones, which were like the blowing up of magazines. Thus we may account for the rattling noise like small-arms, heard after the great bounce on the explosion over Tiverton; the continuance of which, for some time, argues that its sound came from distances that increased.
What may be said to the propagation of the sound through a medium, according to the received theory of the air above 300,000 times rarer than what we breathe, and next to a vacuum, I must confess I know not. Hitherto we have concluded the air to be the vehicle of sound; and in our artificial vacuum we find it greatly diminished : but we have this only instance of the effect of an ex. plosion of a mile or two diameter, the immensity of which may perlaps compensate for the extreme tenuity of the medium.
[Phil. Trans, 1719.
Meteor of a Flaming Sword, seen in Yorkshire, and other
neighbouring Counties, May 18, 1710.
By Mr. Ralph Thoresby. A STRANGE meteor was seen at Leeds, on Holy Thursday, 1710, which the common people call a faining sword. It was seen in the neighbouring towns, but a great way north, as also above fifty iniles south of Leeds. It appeared here at a quarter past ten at night, and took its course from south to north: it was broad at one end, and small at the other; and was by some thought to re. semble a trumpet, and moved with the broad end foremost. The light was so sudden and bright, that people were startled to see their own shadows, when neither sub nor moon shone upon them. This is remarkable, that all persons, though at many miles distance from each other, when they saw it, thought it fell within three or four furlongs of them, and that it went out with bright sparklings at the small end. An ingenivus clergyman told me, that it was the strangest deceptio visus he was ever sensible of, if it was not absolutely extinguished within a few paces of him ; and yet others saw it many miles off, further nortlı, in a few moments. It was likewise seen in the counties of Nottingham and Derby, as well as those of York and Lancaster.