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In the computation of the preceding eclipses of the the ellipticity of the earth was assumed to be one thr semidiameter of the sun was diminished 33" for irrad moon 2" for inflexion, according to the theory of Du

The elements are given in apparent time for the wich, reckoned according to the manner of astro noon. When apparent is to be converted into me of time must be applied with the sign prefixed to it, is to be reduced to apparent, the sign of the equation No sign is prefixed to the hourly motion of the m of the sun in right ascension (AR), as they are alwa

In the computation of an eclipse of the sun, or of a place, the latitude of the place and the moon's equat reduced for the ellipticity of the earth, which is gen one three-hundredth; these reductions will be found the "New American Practical Navigator," or they the following formula.

Let L be the latitude and R the reduction of the lati (L-R) = 0,0029001+ log. cotang. L. The reduc rallax, (57' for example,) may be found thus, 5.7"

ECLIPSES OF THE SATELLITES OF JUE Visible in the United States; the phases of wh mean solar time for the meridian of Washington Greenwich), reckoned, according to the manner

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lipses before the opposition of Jupiter on the 5th of July, will take the west side of the planet, and afterwards on the east. The imonly, of the 1st and 2d satellites will be visible before the opposithe emersions only, after; but both the phenomena of the same f the two outer satellites, can sometimes be seen.

clipses take place farthest from the body of Jupiter, when he is in e, and nearest when in opposition or conjunction; but for some fore and after he is in the latter position, the eclipses cannot be ; the planet and his satellites being lost in the rays of the Sun. es of these satellites, particularly of the first and second, are very determining, to a very considerable degree of accuracy, the lonany place; which, although not so exact as that obtained by ed occultation of a star by the moon, is deduced without the long ing calculation necessary, in obtaining it by the latter method; e likewise the additional advantage of being of very frequent oc

ermine the time at which either of the preceding eclipse; will take any other meridian than that of Washington, it is necessary, to add four minutes for every degree of longitude less than 30", and subtract the same quantity for every degree greater. on, add 23m. 25s.; for New York, 11m. 38s. For Charleston, 11m. 30s.; for Cincinnati, 30m. 6s.; for New Orleans, 52m. 54s.

Position and Magnitude of the Rings of Saturn, according to Bessel and Struve, for every fortieth day in the year.

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p. Angle between the semiconjugate axis of the ring ellipse, with the circle of declination; positive when east, negative when west.

1. Angle of elevation of the earth, above the plane of the ring, as seen from Saturn, positive when north, negative when south.

a.

Semitransverse axis of the ring ellipse.

b. Semiconjugate axis; positive, when the northern surface of the rings is visible; negative, when the southern.

It has lately been ascertained, that the planet is not exactly in the centre of the rings.

The planet Mercury will be visible in the evening until the 11th of February, then in the morning to the 22d of April, then in the evening to the 15th of June, then in the morning to the 4th of August, then in the evening to the 12th of October, then in the morning to the 3d of December, then in the evening.

It is with difficulty that this planet can be seen in any other position, except when at or near its greatest elongation from the Sun, which this year happen January 27th (elongation 18° 24′), March 10th (27° 30′), May 21st (22°32′) July 8th (26° 29'), Sept. 17th (26° 29′), and Oct. 28th (18° 37'); but the following periods will be most favorable for observing it, this year, as during them it will not only be at its greatest distance from the Sun, but will be nearer the elevated pole, and consequently, will remain longer above the horizon.

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Oct. 19th

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From Jan. 16th to Feb. 4th, in the evening after sunset, bearing W. 15° S. May 1st June 4th, in the morning before sunrise, “ E. 23 N. Nov. 7th, E. 6 S. The planet Venus will be visible in the evening to the 7th of March, then in the morning to the 20th of December, then in the evening; its greatest western elongation (45° 59′) will take place on the 16th of May; but it will be the brightest, as evening star, on the 13th of January, and as morning star, on the 25th of April.

The planet Mars will be visible in the morning to the 19th of September, then in the evening to the end of the year.

The planet Vesta will be visible in the morning to the 8th of October, then in the evening.

The planet Pallas will be visible in the morning to the 27th of April, then in the evening.

The planet Juno will be visible in the morning to August 25th, then in the evening.

planet Ceres will be visible in the morning till the 30th of April, then evening.

planet Jupiter will be visible in the morning till July 5th, then in the ng.

planet Saturn will be visible in the morning till the 3d of February, n the evening to the 14th of August, then in the morning to the end year.

planet Uranus or Herschel will be visible in the evening till the 26th uary, then in the morning to August 1st, then in the evening to the the year.

superior planets, or all but Mercury and Venus, will appear brightest nearest to the earth, that is, when in opposition to the sun.

IGHT OF THE GREATEST OR SPRING TIDES IN 1830, uted by the formula of La Place (Mécanique Céleste, vol. II. p. 289.)

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unit of altitude, is the altitude of the tide which happens about a a half after the time of new or full moon; at the moment of new or on the sun and moon being at their mean distance from the earth, the plane of the equator.

unit of altitude of any place, multiplied by the numbers in the preTable, will give the height of the tide at that place.

unit of altitude at BOSTON, Salem, Marblehead, and Cape Ann, is

et.

NEW YORK, St. Augustine, Block Island, Elizabeth Town Point, Keys, Hillsborough Inlet, Nantucket Shoal and Town, New BedChode Island, and Sandy Hook, 5 feet.

CHARLESTON, S. C., Monomoy Point, Port Hood, Prince Edward's , St. Simon's Bar, and St. Simon's Sound, 6 feet. These, multiby the numbers in the preceding table, give the following, as the s of the greatest tides, this year, in those places.

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It appears by the preceding Table, that the tides of Fe 25th, October 3d, and November 1st, will be the greates the positions of the Sun and Moon will not be so favoral last, for producing a great elevation of the sea; the heigh ever, depends so much on the strength and direction of t unfrequently happens that a tide, which would, indepen been small, is higher than one in other respects much g The following Table contains the unit of altitude of places on our coast, from the best authorities. The heig tides in the Bay of Fundy was ascertained from actu gentleman of Boston, in the summers of 1828 and 1829.

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