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. And 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 up, ascend but to a small height, and are quickly returned in rain, 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 themselves into a narrower compass, might 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 flame 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 inconceivable a velocity 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 more 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 perhaps compensate for the extreme tenuity of the medium. [Phil. Trans. 1719.

SECTION 17.

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 flaming sword. It was seen in the neighbouring towns, but a great way north, as also above fifty miles 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 resemble a trumpet, and moved with the broad end foremost. The light was so sudden and bright, that people were startled to see upon them. their own shadows, when neither sun nor moon shoue 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 ingenious 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 north, in a few moments. It was likewise seen in the counties of Nottingham and Derby, as well as those of York and Lancaster.

[Ibid. 1711.

SECTION V.

Luminous Meteor, seen at Peckham, Dec. 11, 1741.

By Thomas Milner, M.D.

Dec. 11, 1741, at seven minutes past one in the afternoon, a - globe of light, somewhat larger than the horizontal full moon, and as bright as the moon appears at any time while the sun is above the horizon, instantaneously appeared, in a clear blue sky, about the S.S.E. moving towards the east with a continual equable motion, and leaving behind it a narrow streak of light, whiter than the globe itself, throughout its whole course. Towards the end it appeared less than at the beginning of its motion; and within three, or at most four, seconds, it suddenly vanished. Its apparent velocity was nearly equal to half the medium velocity of those usual meteors commonly called falling or shooting stars.

The narrow luminous streak remained very distinct after the globe was gone; and gave a fair opportunity for taking the elevation of this phenomenon above the horizon, at the beginning and end of its motion, &c. which was found to be twenty degrees. This lumi. nous track, or path, seemed a right line, not quite parallel, but a little inclined to the plane of the horizon, viz. highest towards the east. It was at first very narrow, and pointed at each extremity; but soon grew broader, and within twenty minutes after the appearance, it was exactly like a long bright rare cloud, discontinued in two places, above three times its first breadth, and a little more inclined to, and elevated above, the horizon, than it was immediately after the motion of the globe.

[Phil. Trans. 1742.

SECTION VI.

Account of some late Fiery Meteors, with Observations.

By Charles Blagden, M.D. Sec. R. S.

This account respects chiefly the two most remarkable of the meteors that had lately appeared, and is founded partly on private communications, and partly on such accounts as were published in

the newspapers. These meteors were of the kind known to the ancients by the names of Aaurades, Пo, Bolides, Faces, Globi, &c. from particular differences in their shape and appearance, and sometimes, it seems, under the general term of comets: in the Philosophical Transactions they are called indiscriminately fire-balls, or fiery meteors; and names of a similar import have been applied to them in the different languages of Europe. The most material circumstances observed of such meteors may be brought under the following heads. 1. Their general appearance. 2. Their path. 3. Their shape or figure. 4. Their light and colours. 5. Their height. 6. Their noise. 7. Their size. 8. Their duration. 9. Their velocity.

Dr. B. begins with the first of these meteors, which was seen August 18, 1783.

§ 1. Its general appearance in these parts of Great Britain was that of a luminous ball, which rose in the N.N.W. nearly round, became elliptical, and gradually assumed a tail as it ascended, and in a certain part of its course seemed to undergo a remarkable change, compared to bursting: after which it proceeded no longer as an entire mass, but was apparently divided into a great number, or a cluster of balls, some larger than the others, and all carrying a tail or leaving a train behind; under this form it continued its course with a nearly equable motion, dropping or casting off sparks, and yielding a prodigious light, which illuminated all objects to a surprising degree; till having passed the east, and verging consider. ably to the southward, it gradually distended, and at length was lost out of sight. The time of its appearance was 9h. 16 min. P. M. mean time of the meridian of London, and it continued visible about half a minute.

§ 2. How far north the meteor may have begun there are no materials to determine with precision; but, as it was seen in Shetland, and at sea between the Lewes and Fort William, and appeared to persons at Aberdeen and Blair, in Athol, ascending from the northward; and to an observer in Edinburgh as rising like the planet Mars; there can be little doubt but its course commenced beyond the farthest extremity of this island, somewhere over the northern General Murray, F.R S. being then at Athol House, saw it pass over his head as nearly vertical as he could judge, tracing it from about 45 degrees of elevation north-north-westward to 30 or

ocean.

20 degrees south-south-eastward, where a range of buildings intercepted it from his view. From near the zenith of Athol House, it passed on a little westward of Perth, and probably a little eastward of Edinburgh; and continuing its progress over the south of Scotland, and the western parts of Northumberland, and the bishopric of Durham, proceeded almost through the middle of Yorkshire, leaving the capital of that county somewhat to the eastward. Hitherto its path was as nearly S.S.E. as can be ascertained; but somewhere near the borders of Yorkshire, or in Lincolnshire, it appears to have gradually deviated to the eastward; and in the course of that deviation to have suffered a very remarkable change in the nature of its appearance, and to have separated into two parts. After this division the compact cluster of smaller meteors seems to have moved for some time almost S.E. thus traversing Cambridgeshire, and perhaps the western confines of Suffolk; but gradually recovering its original direction, it proceeded over Essex and the Straits of Dover, entering the continent probably not far from Dunkirk, where, as well as at Calais and Ostend, it was thought to be vertical. Afterwards it was seen at Brussels, Paris, and Nuits in Burgundy, still holding on its course to the southward; nay, there is an intimation, though of doubtful authority, that it was perceived at Rome. Our information of its progress over the continent is indeed very defective and obscure; yet we have sufficient proof that it traversed in all thirteen or fourteen degrees of latitude, describing a track of 1000 miles at least over the surface of the earth; a length of course far exceeding the utmost that has been hitherto ascertained of any similar phenomenon.

§ 3. This meteor was described by most spectators under three different forms, and is so represented by Mr. Sandby in his beautiful drawing; but the first two of those do not imply any real variation in its shape, depending only on a difference in the point of view. Accordingly, in the first part of its course over Scotland, it was seen to have a tail, and is thus described by General Murray when it passed Athol House. Two causes concur in this deception; first, the fore-shortening, and even occultation, of the tail, when the object is seen nearly in front; and, 2dly, that the light of most part of the tail is of so inferior a kind, as to be difficultly perceived at a great distance, especially when the eye is dazzled by the overpowering brilliancy of the body. The length and shape of the tail, however,