3. Again, with regard to the apparent direction of the body, this will evidently be various, being that compounded of the body's descent, and the direction of the earth's annual motion at the time of the fall, which is itself various in the different seasons of the year, according to the direction of the several points of the ecliptic to the earth's meridian or axis. Usually, however, from the great excess of the earth's motion, above that of the falling body, the direction of this must appear to be nearly opposite to that of the former. And in fact this exactly agrees with a remark made by Dr. Halley, in his account of the meteors in his paper above given, where he says that the direction of the meteor's motion was exactly opposite to that of the earth in her orbit. And if this shall generally be found to be the case, it will prove a powerful confirmation of this theory of the lunar substances. Unfortunately, however, the observations on this point are very few, and mostly inaccurate: the angle or direction of the fallen stones has not been recorded; and that of the flying meteor commonly mistaken, all the various observers giving it a different course, some even directly the re. verse of others. In future, it will be very advisable that the observers of fallen stones, observe and record the direction or bearing of the perforation, made by the body in the earth, which will give us perhaps the course of the path nearer than any other observation.

4. In the flight of these meteoric stones, it is commonly observ. ed that they yield a loud whizzing sound. Indeed it would be surprising if they did not. For if the like sound be given by the smooth and regularly formed cannon ball, and heard at a consider. able distance, how exceedingly great must be that of a body so much larger, which is of an irregular form and surface too, and striking the air with 50 or 100 times the velocity.

5. That they commonly burst and fly in pieces in their rapid flight, is a circumstance exceedingly like to happen, both from the violent state of fusion on their surface, and from the extreme rapidity of their motion through the air. If a grinding-stone, from its quick rotation, be sometimes burst, and fly in pieces; and if the same thing happen to cannon-balls, when made of stone, and discharged with considerable velocity, merely by the friction and resistance of the air; how much more is the same to be expected to happen to the atmospheric stones, moving with more

than fifty times the velocity, and when their surface may well be supposed to be partly loosened or dissolved by the extremity of the heat there.

6. That the stones strike the ground with a great force, and penetrate to a considerable depth, as is usually observed, is a circumstance only to be expected, from the extreme rapidity of their motion, and their great weight, when we consider that a cannon ball, or a mortar shell, will often bury itself many inches, or even some feet, in the earth.

7. That these stones, when soon sought after and found, are hot, and exhibit the marks of recent fusion, are also the natural consequences of the extreme degree of inflammation in which their surface had been put during their flight through the air.

8. That these stony masses have all the same external appearance and contexture, as well as internally the same nature and composition, are circumstances that strongly point out an identity of origin, whatever may be the cause to which they owe so gene. rally uniform a conformation. And when it is considered, 9thly, that in those respects they differ totally from all terrestrial compo. sitions hitherto known or discovered; they lead the mind strongly to ascribe them to some other origin than the earth we inhabit; and none so likely as coming from our neighbouring planet.

Upon the whole then it appears highly probable, that the flaming meteors, and the burning stones that fall on the earth, are one and the same thing. It also appears impossible, or in the extremest degree improbable, to ascribe these, either to a formation in the superior parts of the atmosphere, or to the eruptions of terrestrial volcanoes, or to the generation by lightning striking the earth. But, on the other hand, that it is possible for such masses to be projected from the moon so as to reach the earth: and that all the phænomena of these meteors, or falling stones, have a surprising conformity with the circumstances of masses that may be expelled from the moon by natural causes, unite in forming a body of strong evidence, that this is in all probability and actually the

case.

[Phil. Trans. Abr. Vol. 6, p. 100.

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 celestia 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. Len th of the path 1.5 miles. Longitude of the place of disappe rance 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.

* See Gilbert vi. 224, x. 242.

[EDITOR.