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قراءة كتاب Meteoric astronomy: A treatise on shooting-stars, fire-balls, and aerolites
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Meteoric astronomy: A treatise on shooting-stars, fire-balls, and aerolites
9th or 10th of the month was first shown, however, by Quetelet, shortly after the discovery of the yearly return of the November phenomenon. Since that time an extraordinary number of meteors has been regularly observed, both in Europe and America, from the 7th to the 11th of the month; the greatest number being generally seen on the 10th. In 1839, Edward Heis, of Aix-la-Chapelle, saw 160 meteors in one hour on the night of the 10th. In 1842, he saw 34 in ten minutes at the time of the maximum. In 1861, on the night of the 10th, four observers, watching together at New Haven, saw in three hours—from ten to one o'clock—289 meteors. On the same night, at Natick, Massachusetts, two observers saw 397 in about seven hours. At London, Mercer County, Pennsylvania, on the night of August 9th, 1866, Samuel S. Gilson, Esq., watching alone, saw 72 meteors in forty minutes, and, with an assistant, 117 in one hour and fifteen minutes. Generally, the number observed per hour, at the time of the August maximum, is about nine times as great as on ordinary nights. Like the November meteors, they have a common "radiant;" that is, their tracks, when produced backward, meet, or nearly meet, in a particular point in the constellation Perseus.
Of the 315 meteoric displays given in Quetelet's "Catalogue des principales apparitions d'étoiles filantes," 63 seem to have been derived from the August ring. The first 11 of these, with one exception, were observed in China during the last days of July, as follows:
1 | A.D. 811, | July | 25th. |
2 | 820, | " | 25th–30th. |
3 | 824, | " | 26th–28th. |
4 | 830, | " | 26th. |
5 | 833, | " | 27th. |
6 | 835, | " | 26th. |
7 | 841, | " | 25th–30th. |
8 | 924, | " | 27th–30th. |
9 | 925, | " | 27th–30th. |
10 | 926, | " | 27th–30th. |
11 | 933, | " | 25th–30th. |
The next dates are 1243, August 2d, and 1451, August 7th. A comparison of these dates indicates a forward motion of the node of the ring along the ecliptic. This was pointed out several years since by Boguslawski. A similar motion of the node has also been found in the case of the November ring. That these points should be stationary is, indeed, altogether improbable. The nodes of all the planetary orbits, it is well known, have a secular variation.
On the evening of August 10th, 1861, at about 11h. 30m., a meteor was seen by Mr. E. C. Herrick and Prof. A. C. Twining, at New Haven, Connecticut, which "was much more splendid than Venus, and left a train of sparks which remained luminous for twenty seconds after the meteor disappeared." The same meteor was also accurately observed at Burlington, New Jersey, by Mr. Benjamin V. Marsh. It was "conformable,"—that is, its track produced backward passed through the common radiant—and it was undoubtedly a member of the August group. The observations were discussed by Professor H. A. Newton, of Yale College, who deduced from them the following approximate elements of the ring:8
Semi-axis major | 0·84 | |
Eccentricity | 0·28 | |
Perihelion distance | 0·60 | |
Inclination | 84° | |
Period | 281 | days. |
Motion, retrograde. |
The earth moving at the rate of 68,000 miles per hour, is at least five days in passing entirely through the ring. This gives a thickness of more than 8,000,000 miles.
The result of Professor Newton's researches on the orbit of this ring, though undertaken with inadequate data, and hence, in some respects, probably far from correct, is nevertheless highly interesting as being the first attempt to determine the orbit of shooting-stars. More recent investigations have shown a remarkable resemblance between the elements of these meteors and those of the third comet of 1862. The former, by Schiaparelli, and the latter, by Oppolzer, are as follows:
Meteors of August 10th. | Comet III., 1862. | |
---|---|---|
Longitude of perihelion | 343° 38′ | 344° 41′ |
Ascending node | 138 16 | 137 27 |
Inclination | 63 3 | 66 25 |
Perihelion distance | 0·9643 | 0·9626 |
Period | 105 years(?). | 123 years(?). |
Motion | Retrograde. | Retrograde. |
This similarity is too great to be accidental. The August meteors and the third comet of 1862 probably belong to the same ring.
III. The Meteors of April 18th–26th.
The following dates of the April meteoric showers are extracted from Quetelet's table previously referred to:
1 | A.D. 401, | April | 9th. |
2 | 538, | " | 7th. |
3 | 839, | " | 17th. |
4 | 927, | " | 17th. |
5 | 934, | " | 18th. |
6 | 1009, | " | 16th. |
7 | 1094, | " | 10th. |
8 | 1096, | " | 10th. |