(by the Greeks called μετεώρα, q. d. sublima, or "high raised;" by the Latins imprefiones, as making signs or impressions in the air), commonly denotes any bodies in the air that are of a flux or transitory nature. Hence it is extended to the phenomena of hail, rain, snow, thunder, &c.; but is most commonly confined to those unusual and fiery appearances named falling-stars, ignes fatui, aurora borealis, &c., whether they appear at a great distance from the earth or not.—Till the discovery of electricity these meteors could not be accounted for; but they are now resolved, by the almost universal consent of philosophers, into the action of that fluid; which, tho' unheeded, hath shewed itself in all ages.

A luminous appearance, which must have been of an electric nature, is mentioned by Plutarch in his life of Lysander; who considers it as a meteor. Pliny, in his second book of Natural History, calls those appearances stars; and tells us, that they settled not only upon the masts, and other parts of ships, but also upon men's heads. "Stars, says he, make their appearance, both on land and sea. I have seen a light in that form on the spears of soldiers keeping watch by night upon the ramparts. They are seen also on the sail-yards, and other parts of the ships, making an audible sound, and frequently changing their places. Two of these lights forebode good weather and a prosperous voyage; and drive away the single one, which wears a threatening aspect. This the sailors call Helen; but the two they call Castor and Pollux, and invoke them as gods. These lights do sometimes, about the evening, rest on men's heads, and are a great and good omen." Seneca, in his natural questions, chap. i., takes notice of the same phenomenon. "A star (says he) settled on the lance of Gylippus, as he was failing to Syracuse; and spears seemed to be on fire in the Roman camp." In Caesar we find the same appearances attending a violent storm. "About that time, (says the author,) there was a very extraordinary appearance in the army of Cæsar. In the month of February, about the second watch of the night, there suddenly arose a thick cloud, followed by a shower of stones; and the same night, the points of the spears belonging to the fifth legion seemed to be on fire." Livy also mentions two similar facts. "The spears of some soldiers in Sicily, and a walking stick which a horseman in Sardinia was holding in his hand, seemed to be on fire. The shores were also luminous with frequent fires."

These appearances are called, both by the French and Spaniards inhabiting the coasts of the Mediterranean, St Helme's or St Telme's fires; by the Italians, the fires of St Peter and St Nicholas; and are frequently taken notice of by the writers of voyages. If some late accounts from France are to be depended upon, this phenomenon has been observed at Plauzet for time immemorial; and Mr Binon, the curate of the place, says, says, that for 27 years, during which he resided there, in great storms accompanied with black clouds, and frequent lightning, the three-pointed extremities of the cross of the steeple of that place appeared surrounded with a body of flame; and that when this phenomenon has been seen, the storm was no longer to be dreaded, and calm weather returned soon after.

Modern history furnishes a great many examples of a similar kind; but the most remarkable of these terrestrial meteors, if they may be so called, is the ignis fatuus, or, in common English, Will with a wisp, to which the credulous vulgar ascribe very extraordinary and especially mischievous powers. This phenomenon is chiefly visible in damp places, and is also said to be very often seen in burying grounds, and near dung-hills. Travellers say, that it is very frequent near Bologna in Italy, and in several parts of Spain and Ethiopia. The form and size of it are very various, and often variable.

It was the opinion of many philosophers, and especially Willoughby and Ray, that the ignis fatuus is made by shining insects; but this opinion was never well supported. Sir Isaac Newton calls it a vapour shining without heat, and supposes that there is the same difference between this vapour and flame, that there is between wood shining without heat, and burning coals of fire. That this opinion is just, and moreover, that the light of this vapour shining without heat is of the same nature with light from putrescent substances, may, according to Dr Priestley, be concluded from the following circumstances relating to them, as described by Dr Derham, and G. B. Beccari.

The former of these gentlemen, having observed an ignis fatuus in some boggy ground, between two rocky hills, in a dark and calm night, got by degrees within two or three yards of it, and thereby had an opportunity of viewing it to the greatest advantage. It kept skipping about a dead thistle, till a slight motion of the air, occasioned, as he supposed, by his near approach to it, made it jump to another place; and as he advanced, it kept flying before him. He was so near to it, that, had it been the shining of glowworms, he was satisfied that he could not but have distinguished the separate lights of which it must have consisted; whereas it was one uniform body of light. He therefore thought that it must be an ignited vapour. Similar in some respects to this light, was one that surrounded the body and the bed of a woman at Milan, which fled from the hand that approached it, but was at length dispersed by the agitation of the air.

Mr Beccari made it his business to inquire concerning this phenomenon of all his acquaintance, who had had opportunities of observing it, either on the mountains, or on the plain. He found that two which appeared on the plains, one to the north, and the other to the east of Bologna, were to be seen almost every dark night, especially the latter; and the light they gave was equal to that of an ordinary faggot. That to the east of Bologna once appeared to a gentleman of his acquaintance, as he was travelling, and kept him company above a mile, constantly moving before him, and casting a stronger light upon the road than the torch which was carried along with him. All these luminous appearances, he says, gave light enough to make all the neighbouring objects visible, and they were always observed to be in motion, but this motion was various and uncertain. Sometimes they would rise up, and at other times sink; but they commonly kept hovering about six feet from the ground. They would also disappear of a sudden, and instantly appear again in some other place. They differed both in size and figure, sometimes spreading pretty wide, and then again contracting themselves; sometimes breaking into two, and then joining again; sometimes floating like waves, and dropping, as it were, sparks of fire. He was assured that there was not a dark night all the year round in which they did not appear, and that they were observed more frequently when the ground was covered with snow, than in the hottest summer; nor did rain or snow in the least hinder their appearance; but, on the contrary, they were observed more frequently, and cast a stronger light in rainy and wet weather; nor were they much affected by the wind.

The grounds to the east of Bologna, where the largest of these appearances was seen, is, he says, a hard chalky and clayey soil, which will retain the water a long time, and afterwards, in hot weather, would break into large cracks; but on the mountains, where the ignis fatuus were smaller, the soil was of a loose sandy texture, which would not keep the water very long. According to the best information he could procure, these lights very much frequent brooks and rivers, being often observed on the banks of them; perhaps, he says, because the current of air carries them thither more readily than to any other place.

This gentleman concludes his account of these appearances with the following curious narrative. An intelligent gentleman travelling in March, between eight and nine in the evening, in a mountainous road, about ten miles south of Bologna, perceived a light, which shone very strongly upon some stones which lay on the banks of the river Rioverde. It seemed to be about two feet above the stones, and not far from the water. In size and figure it had the appearance of a parallelopiped, somewhat more than a foot in length, and half a foot high, the longest side being parallel to the horizon. Its light was so strong, that he could plainly distinguish by it part of a neighbouring hedge, and the water of the river; only in the east corner of it the light was rather faint, and the square figure less perfect, as if it was cut off or darkened by the segment of a circle.

His curiosity tempting him to examine this appearance a little nearer, he advanced gently towards the place; but was surprized to find that it changed gradually from a bright red, first to a yellowish, and then to a pale colour, in proportion as he drew nearer; and when he came to the place itself it quite vanished. Upon this he stepped back, and not only saw it again, but found that the farther he went from it, the stronger and brighter it grew. When he examined the place of this luminous appearance, he could not perceive the least smell, or any other mark of fire.

This extraordinary account was confirmed to Mr. Beccari by another gentleman, who frequently travelled the same road, and who assured him that he had seen the very same light five or six different times, in spring and autumn, and that he had always observed it. it to be of the very same shape, and in the same place; and he once took particular notice of its coming out of a neighbouring place, and settling itself in the figure above described.

M. Beccari owns himself to be greatly at a loss to account not only for this very remarkable appearance, but also for the ignis fatuus in general. He only says, that all persons who ever saw any of these appearances, agree, that they cast a light quite different from that of shining flies.

Dr Shaw describes an ignis fatuus, which he saw in the Holy Land, the circumstances of which are very remarkable. As he and his company were travelling by night, through the valleys of mount Ephraim, they were attended, more than an hour, by an ignis fatuus, which was sometimes globular, or in the form of the flame of a candle; and which would, immediately afterwards, spread itself so much as to involve the whole company in a pale inoffensive light, and then contract itself again, and suddenly disappear. But in less than a minute it would become visible as before; or, running along from one place to another, with a swift progressive motion, would expand itself, at certain intervals, over more than two or three acres of the adjacent mountains. The atmosphere, from the beginning of the evening, had been remarkably thick and hazy, and the dew, as they felt it upon their bridles, was unusually clammy and unctuous. In the same kind of weather, he says, he has observed those luminous appearances, which, at sea, skip about the masts and yards of ships, and which the sailors call corpulantes, which is a corruption of the Spanish cuerpo santo.

Of the celestial meteors, the most common are those called falling-stars, which are so well known, that it is needless to describe them. They do not very often appear of a larger size than the brightest fixed stars, tho' sometimes they equal Jupiter, or even Venus in apparent bulk, and are then exceedingly bright. They sometimes rise high in the air; for Mr Brydone takes notice of his having seen them as high to appearance above the top of Mount Aetna, as they usually appear when viewed from the ordinary ground. Sometimes, however, they are much lower. Signior Beccari mentions one which seemed to direct its course towards the place where he sat, growing continually larger and larger as it advanced, till at last it disappeared at no great distance, and left the faces, hands, and clothes, of those who saw it, and all the neighbouring objects, suddenly illuminated with a diffused and lambent light attended with no noise at all. While they were starting up, standing and looking at one another, surprised at the appearance, a servant came running to them out of a neighbouring garden, and asked them if they had seen nothing; for that he had seen a light shine suddenly in the garden, and especially upon the streams which he was throwing to water it.

The other kinds of celestial meteors are, aurora borealis, lightning of various forms, and large fire-balls. All these too sometimes appear very high, and sometimes very low; the fire-balls especially, will sometimes strike the ground, and explode with great violence, producing many mischievous effects. See Atmosphere, Aurora Borealis, Cloud, Lightning, &c.

The general principles on which the phenomena of meteors depend, have already been so fully explained under the article Electricity, &c. that very little remains to be added in this place. The inoffensive lights, such as appear on the points of metallic bodies, the ignis fatuus, &c. are occasioned by a current of electric matter setting into or out of any particular body; for wherever that fluid is much agitated, there a light will be visible. If at the same time there is a considerable difference between the electricity of the atmosphere and the surface of the ground, the electric stream will be quietly imbibed, and no dangerous consequences will ensue to those who approach it; but if the electricity of the atmosphere and the ground happens to be much the same, the fluid will then be much compressed, will burn, explode, and produce all the mischief of the forked or crooked lightning, or of that kind which appears in the form of balls, and which is fully explained under the article Lightning.