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m. s. Sunday, · October 1st, from the time by the dial subtract 10 23 Friday, - - - - 6th, - - • - - - - - - - 11 53 Wednesday,- - • 11th, - - - - - - - - - - 13 14 Monday, . - - 16th, '. , - - - - - - - - 14 22 Saturday, - - - - 21st, - • - - - - - - - - 15 17 Thursday, • • - 26th, • - - - - - • - • 15 55 Tuesday, - - - 31st, • • • • • • • - - 16 14
Phases of the Moon.
Moon's Passage over the Meridian. The Moon will pass the first meridian at the following convenient times for observations during this month: viz. October 13th, at 2 m. after 5 in the evening
14th, 1 - - 6 - - - -
4 in the morning
- - 5 - - -
Phase of Venus.
2 Dark part -.-= 6:5160
9th, - . 26 after 7 evening
14th, - - 23 - - 1 morning
Form of Saturn's Ring.
s Transverse axis = 1.000
Other Phenomena. Mercury will be in his superior conjunction at 45 m. after 6 in the evening of the 1st of this month. Venus will attain her greatest elongation on the Sth. Saturn will be in opposition at 11 in the morning of the 23d. Mars will be in conjunction with a in Libra at 37 m. after 4 in the afternoon of the 11th, when the star will be 55' north of the planet. Mercury will also be in conjunction with the same star at 10 m. past 2 in the morning of the 23d, and the star will then be 86' north of the planet. The Moon will also be in conjunction with a in Scorpio at 35m. after 8 in the morning of the 3d; with a in Virgo, at 7 m. after 10 in the evening of the 7th ; with a in Scorpio, at 44 m. after 3 in the afternoon of the 11th. The Moon will also eclipse Jupiter on the 18th: the Immersion will take place at 57 m. 15 s. after 4 in the afternoon, when the planet will be 15%' north of the Moon's centre, and the Emersion at 27 m. 45 s. after 5, the star being then 131 north of the same point. The Moon will likewise be in conjunction with ß in Taurus, at 4 m. after 7 in the morning of the 25th ; with Pollux at 16 m. after 3 in the afternoon of the 27th; and with a in Leo, at 28 m. after 3 in the afternoon of the 30th. The Moon will also be in Apogee on the 5th, and in Perigee on the 20th of this month.
Eclipse of the Sun. The solar eclipse which will take place soon after noon on Thursday, September 7th, in this year, will be the greatest that has happened in this part of
Europe since the year 1764, and will not be equalled by any other till 1847. Like both these eclipses it will be annular ; that is, the disc of the Moon will not wholly cover that of the Sun, but in certain parts of the Earth there will be a bright annulus or ring round the disc of the Moon, as a part of the Sun's disc will be seen all round the Moon. The position and magnitude, as well as the very existence of this annulus, will evidently depend upon the situation of the observer. The annular appearance, however, will not be seen in any part of England; though the eclipse will be of great magnitude along all the eastern coasts of Great Britain.
Mr. Baily, of Gray's Inn, with a laudable zeal for the promotion of science, has printed and circulated a Memoir on the subject, in which he has not only collected various particulars relative to those annular eclipses which have already been observed, but has pointed out the particulars which should be attended to in the observation of this which is now approaching; with a view of calling the attention of the public, and particularly those who have any means of making the requisite observations, to the subject. From this Memoir, we shall collect a few of the most interesting particulars, and refer such of our readers, as may wish for more extensive information, to the pamphlet itself, which Mr. Baily kindly offers to furnish to those who will send their cards to him for that purpose.
Mr. Baily has carefully computed the elements of the present eclipse from M. Burckhardt's Tables of the Moon, and M. Delambre's Tables of the Sun, and states them as follows:-· The ecliptic conjunction will take place on September 7th, 1820, at 1 h. 51 m 37 S. P. m. apparent time - - 7
Sat Greenwich 1 - 49 - 26 - P. M. mean time - . .. and at that time we shall have the
True longitude of the luminaries - - - - - 53. 14° 47' 40":7 True latitude of the Moon (north) - - - - - - - 44 39.4 Moon's horary motion from the Sun - - - - - • 27 1.7
- - horary motion in latitude (decreasing) - - - 2 42.0 .• - horizontal parallax . - - - - - - - - - 53 55.0
. - semidiameter - - - - - - - - - - - 14 41:0 Sun's semidiameter - - - - - - - - - - 15 54:8 • horizontal parallax - - - - - - -
8•7 - declination (north) - - - - - - - - - - 5 59 41.0
From these elements it may be determined that the Moon's shadow first touches the Earth's disc at 11 h. 23 m. A.M. apparent time at Greenwich, in north latitude 59° 43', west longitude 90° 50'; and that it finally leaves it at 4 h. 39' P.M. apparent time at Greenwich, in north latitude 3° 21', and east longitude 20° 25'. Consequently the total duration of the general eclipse to the inhabitants of the Earth will be about 5 h. 17 m.; but at no one place in particular will the duration be much more than half that time.
The central path of the Moon's shadow across the Earth's disc, which is the most material circumstance in inquiries of this nature (since it serves to point out those parts of the world where the eclipse will be seen annular), may be determined with considerable accuracy from the principles laid down by M. Delambre, in his Traité d'Astronomie (vol. ii, page 384); and agreeably to the formulæ he has there given, Mr. B. has carefully computed the following table, which shows the several points (expressed by positions of latitude and longitude) through which the centre of the Moon's shadow will pass in its progress across the Earth's disc, at the several times therein mentioned. The first column denotes the apparent time at Greenwich, at the moment when the centre of the Moon's shadow passes the given points laid down in the second and third columns ; and the last column shows the corresponding apparent time at those places.'
Apparent Timel at Greenwich,
Apparent Time at
i 11 h. m. S.
47 31 E. 2 50 42 1 51 23
32 2 13 14
44 13 58
031 7 19 30 24 13 5 1 97 8 11 27 10 30 46 2 416 12 19
From this table it will be seen, that the central eclipse commences in north latitude 81° 39' 29". .. west longitude 149° 32' 55", when the Sun and Moon will rise together (the centre of the Moon being nearly on the centre of the Sun's disc), to the inhabitants of that part of the globe, at 2 h. 56 m. 27 s. in the morning, corresponding to 12 h. 54 m. 39 s. (or 0 h. 54 m. 39 s.) in the afternoon at Greenwich; that the Sun will bé centrally eclipsed on the meridian (or exactly at noon), in north latitude 76° 6' 21", west longitude 17° 3' 15", when it is 1 h. 8 m. 16 s. in the afternoon at Greenwich; and that the Sun will set centrally eclipsed in north latitude 27° 10' 30", east longitude 46° 2' 4", at 6h, 12 m. 19 s. in the afternoon, corresponding to 3 h. 8 m. 11 s. at Greenwich.
If the points mentioned in the second and third columns of the above table be marked on a good