SECTION X.

Falling or Shooting Stars.

WE have already observed, that there is much doubt as to the origin of this elegant meteor, common as it is to all countries and seasons. The learned writer of the article in the preceding section seems to ascribe them to the same source as the largest and most concrete meteors of the heavens, and consequently to refer them to a lunar source. And, generally speaking, whatever has been the hypothesis entertained concerning the one class, it has been equally applied to explain the other.

"I am unwilling to assert," says Mr. Cavallo, "though I have no particular reason to deny, that the large meteors, and those which are commonly called shooting stars, have a common origin, or are of the same nature, and differ only in size; our utter ignorance of their nature, and the want of accurate observations, do not enable us to form any other distinction. It appears then, that the number of meteors is immense; for the shooting stars, or the meteors of the smallest size, are to be seen in plenty every clear night. Some of them are so small as to be accidentally seen only through telescopes; others are visible to the naked eye, that happens to be directed to that part of the sky; whilst others, by casting more or less light, excite attention and are remarked. The apparent size of these meteors is various; but their apparent motions, when they happen to direct their course nearly at right angles to the spectator, seem not to differ much; whence we may conclude, that they are nearly at equal distances from the earth; and of course they must actually differ in size. This point, however, is much in want of confirmation; and it might be wished, that three or four observers, in a pleasant autumnal evening, were situated at certain distances (for instance ten or twenty miles) from each other, and would endeavour to mark the altitudes of all the shooting stars they saw, together with the time of their appearance. The altitude may be easily ascertained by observing the stars over or near which the meteor passes, and by referring it to a common celestial globe, rectified for the latitude of the place and time of the apparition *.”

* Elem. of Philos. vol. iv. p. 365.

Such observations have occasionally been made, and such altitudes remarked with all desirable care and circumspection and especially by M. M. Benzenberg and Brandes.

The meteors in this case were observed from a base of 46,200 feet F. or 2.1 German geographical miles, fifteen of which make a degree their height was from four to thirty of those miles; the mean height about eleven, or near fifty English miles. The velocity of two of them was from four to six miles, or about twentytwo English miles in a second. One was brighter than Jupiter, and was 450 miles distant.

In a second paper Dr. Benzenberg gives two instances in detail. September 15. A shooting star of the fifth magnitude. Elevation of the beginning 7·7 geographical miles, of the end 8.2. Length of the path 1.5 miles. Longitude of the place of disappearance 28° 3'; latitude 53° 22'. Observed by Brandes, in Ekwarden, and Benzenberg, in Ham, near Hamburg: length of the base fourteen miles. October 3. Another of the fourth magnitude observed by the same persons. The termination 7.1 geographical miles above the earth. Longitude 27° 7'; latitude 53° 5'. These observations shew, says Dr. Benzenberg, that a long base will furnish as accurate a comparison as a shorter one; that even meteors of the fourth and fifth magnitude may be seen at places distant above fourteen geographical miles from each other; and they confirm the former observations made at Gottingen with a base of but one or two miles.

We will only further observe, as in truth we have partly hinted at before, that Dr. Benzenberg did not believe these small meteors to be of the same nature as the larger. His opinion concerning fiery balls was, that they were revolving bodies distinct from the earth but he conceived the train of shooting stars to be too numerous for such independent revolving bodies; and with Dr. Chladni objected, that, in such case, they would not appear to ascend, as they are often found to do, as well as to descend. There are, at the same time, various difficulties in the way of regarding them as mere electric scintillæ.

[EDITOR.

* See Gilbert vi. 224, x. 242.

ON

CHAP. XLVII.

LUMINOUS AND BURNING EXHALATIONS UNDER THE

NAMES OF IGNIS FATUI; WILL-O'-THE-WHISPS; JACKO'-LANTHORNS; MARINERS' LIGHTS; AND ST. HELMO's

FIRES.

SECTION I.

General Remarks.

THERE is a class of luminous, and not unfrequently inflammable

meteors, which yet remains to be described and explained; the cause of which has often been confounded with that of the preceding class; but which in reality is as totally distinct as the phænomena are themselves. These meteors, instead of being composed of exotic materials, are real exhalations from the earth; as gas, vapour, or some other attenuate substance, combined with the matter of light or heat, or both together; which has been eliminated from vegetable, animal, or mineral materials. Instead of being dense or solid they are uniformly rare and subtile; and instead of originating in the loftiest regions of the atmosphere, or beyond its range, are generated for the most part in low marshy plains or valleys. To the fearful and superstitious they are a source of as much terror as the nobler and sublimer meteors we have just contemplated; and it is probable that they have occasionally been the source of real and extensive damage when in a state of actual combustion; and that they have still more frequently seduced a timid and benighted traveller into dangerous bogs, and quagmires. By the learned they are usually denominated Ignis Fatui, or Mock-fires; and by the vulgar, Will-o'-the-Whisps, Jacko'-Lanthorns; and at sea, or on the coast, Mariners' Lights, or St. Helmo's Fires.

The true cause of these singular appearances has not often been