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OF CERTAIN ACCENSIONS WHICH APPEAR TO TAKE PLACE SPONTANEOUSLY IN THE ATMOSPHERE, CALLED FALLING STARS, METEORS, &c.
THE igneous Meteors which occasionally take place in the atmosphere, have been noticed by most of the ancient writers on natural philosophy with which we are acquainted, as may be found by the works of Aristotle,* Pliny,† Virgil,‡ Lucretius, Seneca,§ and others. But the peculiarities remarkable in the different kinds of them do not appear to have been duly noticed. The most minute differences between them ought to be commemorated, together with their relation to other coexisting phaenomena: for in investigating the causes of these luminous accensions, we shall probably be assisted by
* Arist. Meteor. lib. i. c. 4.
+ Plin. H. N. Lib. ii. cc. 4. 25. 36.
Virg. Georg. lib. i. 365.
Lucret. de Rer. Nat. lib. ii. 206. lib. v. 1190.
§ Senec. Nat. Quaest. lib. i. c. 14.
observing and noting down accurately the peculiarities remarkable in the different kinds of Meteors which from time to time appear. The very large sort, which occasionally are seen; such, for example, as that memorable Meteor seen on Monday, 18th August, 1783, that which took place on Sunday, 13th November, 1803, or the large one recently observed at Geneva,* are not numerous enough to admit of being arranged under any general description; besides which, there are peculiarities in all of the larger sort, whereby each differs from every other. But the smaller kind, which appear in common, seem to me to be referable to three principal varieties, which appear to derive their particular character from the kind of weather in which they happen.
The most common sort are those very small Meteors which are prevalent in clear frosty
* See Nicholson's Journal, 1811.
The falling stars have generally been regarded as foreboders of wind: so Seneca in Hippolyto:
"Ocyor cursum rapiente flamma
Stella cum ventis agitata longos
I have noticed this indication of wind particularly from the caudate Meteors still to be described.
winter nights, and in summer also, when there are dry Easterly winds with a clear sky. They have very much of the appearance of the real stars, and have probably, from this circumstance, derived their vulgar name: they leave little or no train behind them, and shoot along in straight lines, generally obliquely downward, but sometimes horizontally.*
The second kind are larger and more brilliant, and generally appear in warm summer evenings, particularly when cirrocumulus, cirrostratus, and electric clouds abound: some of them are very beautiful, and give much light: they vary somewhat in colour and size. They have sometimes a curvilinear motion.
The third sort are strikingly different from the two abovementioned: they are generally small, and of a beautiful bluishwhite colour; but their peculiar characteristic is that of leaving long white trains behind them, which remain visible for some seconds in the tract in which the Meteors have gone. These tails which I have endeavoured to represent in Plate VI.
* I think I have observed that in summer time, when any kind of falling stars appear, some feature of cirrostratus, however small, may generally be seen about. But this does not appear to be always the case in winter.
Fig. 6. seem to be lost by dispersion; they appear to fly off from all points, increasing in breadth as they become fainter, till at last they cease to be distinguishable. They are generally seen in the intervals of showery weather, and most prevalent before the occurrence of high wind of which they have been considered by Aratus, Virgil, and other writers as a certain prognostick.* These kind of Meteors abounded, on the night of 10th August, 1811, after a showery day. I have thought that their tails were the result rather of some gas set on fire by the meteor in its passage, than of any of the luminous substance of the Meteor left behind
* Καὶ διὰ νυκία μελαιναν ὅτ' ἄσερες αΐσσωσι
Saepe etiam stellas vento impendente videbis
Pliny also remarks, "Si volitare plures stellae videbuntur quo feruntur albescentes, ventos ex his partibus nunciabunt." Plin. Hist. Nat. xviii. 35.
Compare also Lucretius de Rer. Nat. ii. 208. Theophrastus observed of old: “Οθεν ἄν ασερες διαττωσι πολλοι ανεμον εντυθεν εαν δὲ πανταχοθεν ομοιως, πολλα πνευμαία σημαινουσί.
Theoph. de Sign. Vent.
it. I may also remark, that if the larger kind of Meteors happen at the same time that these caudate Meteors are prevalent, they also leave this beautiful white and slowly evanescent tail behind them.*
* The train of light which the common Meteors, or falling stars, appear to leave behind, and which lasts scarcely a moment, seems frequently to be an hallucination of vision, like the Δολικοσκιον εγχος sung by Homer, and quoted by Dr. Darwin, Zoon. sect. iii. v. 3.-To which as well as to his paper, De Oculorum Spectris, I refer the reader. M. Aubert observed a train of reddish fire left behind the bright Meteor seen at London, Oct. 4, 1783, which lasted above a minute after the Meteor was extinguished. See Phil. Trans. vol. lxxiv. 115.
The great Meteor of 18th August, 1783, left corruscations behind it, and moved in an irregular tract. See Phil. Trans. lxxiv. 114.
There are some reasons for thinking that the explosion and loud report of some Meteors, and particularly of the great one of 1783, happen at the alteration of their regular course, as if interruption by explosion of hydrogen, which the Meteor might meet with in its passage, or from any other cause, caused the report, and division of the luminous substance of the Meteor. See Phil. Trans. lxxiv. 20.
There is one remarkable thing about the explosion of Meteors. The great Meteor of 1718 w, according to Halley, above sixty miles from the earth's surface; and yet at that elevated station the air was capable of communicating sound, as appears clear by the report of the Meteor: a circumstance