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ECLIPSES OF THE SATELLITES OF JUPITER.

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d. Aug. 9

10 10 16 16 17 19 23 23 23 24 26

30 Sept. 2

3

4 66 10

11 17 18 25 27 28

29 Oct. 4

5 5 5 11 12

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h. m.
8 29 40
11 51 8
7 20 12
7 58 38
13 55 5
13 46 12
8 15 1

26 24
12 0 3
16 30 1
15 41 20
10 10 11
12 27 44
12 5 31
8 22 37
6 34 19
10 57 48

8 29 47 13

4 10 25 20 12 20 58 6 49 55 8 52

11 31 8 45 39 8 1 46 8 35 36 12 8 21 10 41 25 10 37 26

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m. $. 5 10 20 8 8 25 12 37 13 7 6 8 9 1 57

7 10 10 57 47 5 26 46 7 43 15 4 46 8 8 17 39 7 22 34 10 19 29 8 47 57 9 18 20 5 42 56 4 50 36 7 38 34 10 7 51

27 17 9 34 8 10 4 2 4 26 31

58 32

22 39 4 58 23 8 27 46 7 53 54 8 59 55

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The eclipses before the opposition of Jupiter on the 10th of August will take place on the west side of the planet, and afterwards on the east. The Immersions only, of the first and second Satellites, will be visible before the opposition, and the Emersions only, afterwards; but both the phenomena of the same eclipse of the two outer Satellites can sometimes be seen.

The eclipses take place farthest from the body of Jupiter when he is in quadrature, and nearest when in opposition or conjunction; but for some weeks before and after he is in the latter position, the eclipses cannot be observed, the Planet and his Satellites being rendered invisible by the light of the Sun.

Eclipses of these Satellites, of the first and second especially, are very useful for determining to a very considerable degree of accuracy the longi. tude of any place; which, although not so exact as that obtained by an observed occultation of a star by the Moon, is deduced without the long and fatiguing calculation necessary for obtaining it by the latter method. They have likewise the additional advantage of being of very frequent occurrence. Until very recently, it was generally supposed, that these eclipses could not be observed at sea on account of the motion of the vessel; but an officer in the English Navy has lately shown this opinion to be erroneous; he having succeeded in observing their phenomena from a ship, with a very considerable degree of accuracy.

To determine the time at which either of the preceding eclipses will take place, on any other meridian than that of Washington, it is merely necessary to add four minutes for every degree of longitude less than 760°55' 30",

38

POSITION AND MAGNITUDE OF THE RINGS OF SATURN.

and subtract the same quantity for every degree greater, and in proportion for a part of a degree.

For Boston, add 23m. 25s.; for New York, 11m. 38s. For Charleston, subtract 11m. 30s.; for Cincinnati, 29m. 463.; for New Orleans, 52m. 54s.

6.80/1

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- 11

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3

Position and Magnitude of the Rings of Saturn, according to Bessel

and Struve, for every Fortieth Day in the Year. January 1 6° 35' 8° 45' 44.69 February 9 6 45

0 46.44

8.06 March 21 6 56

11 23 45.61

9.00 April 30

42.89

8.80
June
9

39.97

7.66 July 19 6 40

9 18 37.96

6.14
August 28
- 6 19

37.24

4.57
October 7

- 557
4 49 37.93

3.19
November 16 - 5 39

3 11
39.95

2.22
December 26 5 32

2 41 42.86

2.00
p.

1.
a.

b. 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 rings, as seen from Saturn, positive when north, negative when south.

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 been recently ascertained, that Saturn is not placed exactly in the centre of the rings. This singular circumstance was first perceived by M. Schwalz, of Dessau; but for some time was considered an optical illusion, occasioned by the shadow of the planet upon the ring. The question was settled by Prof. Struve, with the celebrated telescope by Fraunhofer, at Dorpat; who ascertained that the rings are actually eccentric. This eccentricity cannot, however, be perceived but by the assistance of the very best telescopes.

a.

The planet Mercury will set after the Sun until the 27th of January, then rise before him until the 5th of April, then set after him until the 25th of May, then rise before him until the 20th of July, then set after him unti! the 25th of September, then rise before him until the 13th of November, then set after him to the 11th of January, 1832.

This planet cannot be easily seen in any other position than when at, or very near, its greatest elongation from the Sun, or when apparently passing over the Sun's disc, a phenomenon of rare occurrence, but which will actually take place on the 5th of May, 1832. The elongations take place, this year, January 10th (elong. 18° 58'), February 20th (el. 26° 40'), May 3d (el. 21° 3'), June 20th (el. 22° 37'), August 31st (el. 27° 11'), October 12th (el. 18° 5'), December 25th (el. 19° 48'); but, in the present year, the following periods will be the most favorable, in the United States, for observing the planet, as during them it will not only be at or near its greatest apparent distance from the Sun, but will be nearer the elevated pole, and consequently will remain longer above the horizon.

Jan. 1st to Jan. 19th, in the evening after sunset, bearing W. 20° S. April 22d to May 16th,

W. 24 N.

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HEIGHT OF THE GREATEST OR SPRING TIDES IN 1831.

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Oct. 4th to Oct. 25th, morning bef. sunrise, E. 1 S. Dec, 22d to Dec. 31st, evening after sunset, W. 23 S.

Venus will set after the Sun until the 8th of October, then rise before him until the 28th of July, 1832. Its greatest eastern elongation (elong. 45° 43') will take place on the 30th of July, and its greatest western (46° 55') on the 19th of December; but it will be brightest as evening star on the 20th of August, and as morning star on the 30th of November, about which times the planet can be readily seen whilst the Sun is above the horizon.

Mars will set after the Sun until the 24th of September, then rise before him until November 20th, 1832.

Vesta will set after the Sun until the 1st of June, then rise before him during the remainder of the year.

Pallas will rise before the Sun until the 17th of July, then set after him through the year.

Juno will set after the Sun until the 1st of June, then rise before him through the year.

Ceres will rise before the Sun until the 9th of August, then set after him through the year.

Jupiter will set after the Sun until the 20th of January, then rise before him until the 10th of August, then set after him until February 24th, 1832.

Saturn will rise before the Sun until the 17th of February, then set after him until the 29th of August, then rise before him until March 2d, 1832.

Uranus will set after the Sun until the 30th of January, then rise before him until the 5th of August, then set after him until February 4th, 1832.

On the 21st of March this planet and Jupiter will come into conjunction; at which time their distance will be very small

, Uranus teing 6}' South of H. A conjunction of Jupiter and Uranus is a phenomenon of rare occurrence, happening only once in about fourteen years.

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

The oppositions in 1831 will take place as follows, viz. of Saturn, Feb. 17th ; of Pallas, July 22d; of Ceres, Aug. 4th ; of Uranus, Aug. 5th; of Jupiter, Aug. 10th; but Mars, Vesta, and Juno will not be in opposition this year.

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HEIGHT OF THE GREATEST OR SPRING TIDES IN 1831, Computed by the formula of La Place (Mécanique Céleste, vol. II. p. 289.) New or Full Height of New or Full

Height of Moon. h. the Tide. Moon.

h. the Tide. New Moon Jan. 13th, 8 A. 0.87 New Moon July 9th, 9 M. 0.96 Full 27th, 9 A. 0.94 Full

24th, 4 A. 0.81 New Feb. 12th, 0 A. 0.94 New Aug. 7th, 5 A. 0.98 Full 26th, 0 A. 0.95 Full

23d, 5 M. 0.92 New March 14th, 1 M. 1.07 New Sept. 6th, 3 M. 0.99 Full 28th, 3M. 0.91 Full

21st, 5 A. 1.03 New April 12th, 11 M. 1.10 | New Oct. 5th, 5 A. 0.94 Full 26th, 7 A. 0.83 | Full

21st, 4M.

1.09 New May 11th, 7 A 1.04 New o

Nov. 4th, 9M. 0.86 Full 26th, 11 M. 0.79 Full

19th, 2 A. 1.03 New June 10th, 2 M. 0.87 | New Dec. 4th, 3 M. 0.81 Full 25th, 2 M. 0.76 Full

19th, OM. 1.03 The unit of altitude, is the altitude of the tide which happens about a day and a half after the time of New or Full Moon, the Sun and Moon being, at the moment of o or 8, at their mean distance from the Earth, and in the plane of the equator.

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40

HEIGHT OF THE GREATEST OR SPRING TIDES IN 1831.

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The unit of altitude of any place, multiplied by the quantities in the above table, will give the height of the spring tides at that place, in the present year,

The unit of altitude at Boston, Salem, Marblehead, Cape Ann, and Plymouth, is 114 feet:

At New York, St. Augustine, Block Island, Elizabeth Town Point, Florida Keys, Elizabeth Islands, Hillsborough Inlet, Nantucket Shoals and Town, Buzzard's Bay, Martha's Vineyard, Long Island Sound, Rhode Island, and Sandy Hook, 5 feet:

At Charleston, S. C., Monomoy Point, Port Hood, Prince Edward's Islands, St. Simon's Bar, and St. Simon's Sound, 6 feet.

These, multiplied by the preceding numbers, give for the height of the greatest tides, this year, in those places. Tide of Boston, N. York, Charleston, Tide of Boston, N. York, Charleston, &c.

&c. ft. in. ft. in.

ft. in. Jan. 15 9 9

4

July 10 10 10
29 | 10
7 4 8

26 Feb. 13 10 7

8

Aug. 9 10 8 4 9

7 March 15 | 11 10

5 4
Sept. 7

4 11
29 10 3 4 7

23 | 11 April 13 12 5 5 6

Oct. 7 28 9 4 4 2

22 | 12 May 13 11 8 5 2

Nov. 5

9
26
8 9 3 11

20 11

7 June 11 9 9 4 4

Dec. 5 9 8 7 3 10

20 | 11 By the preceding Table it appears, that the tides of March 15th, April 13th, May 13th, September 23d, October 22d, November 20th, and December 20th, will be the most considerable in 1831. The height of the tides, however, depends so much on the strength and direction of the wind, that it not unfrequently happens that a tide, which would independently of this have been small, is higher than one otherwise much greater. But when it happens that a tide, which arrives when the Sun and Moon are in a favorable position for producing a great elevation of the sea, is still further increased by a very strong wind, the rise of the water will be uncommonly great, and injury and loss probably thereby occasioned. A remarkable instance of this occurred in Boston and generally along the coast of New England, on the 26th of March last, when the tide, in itself one of the three highest in the year, being further elevated by a violent easterly gale, actually rose 16 feet 5 inches, and caused very considerable damage. This tide was the greatest observed in that city within the last 45 years.

The following Table contains the unit of altitude of several ports and places on the American coast, from the best authorities.

The height of the tides in the Bay of Fundy was ascertained by recent observations. feet.

feet. Advocate Harbour (Bay of Fundy) 50 Bay, Buzzard's

5 Andrews, St. 25 Casco

9 Annapolis (Bay of Fundy) 30 Chicnecto (north part of

60 Apple River

50 the Bay of Fundy) Augustine, St.

5
6 St. Mary's

16 Basin of Mines (Bay of Fundy) 60

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ng Bay, Bristed 8 Beaver Harbour

7 Broad . 9 Bell Island Straits

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feet.

feet. Block Island 5 Mary's, St., Bar

7 BOSTON

114 Monomoy Point . Cape Ann

11 Moose River (Bay of Fundy) 35 Blomidom (Bay of Fundy) 55 Island (Me.) :

25 Chat 13 Mount Desert

12 Cod

64 Mouths of the Mississippi i)
D'Or (Bay of Fundy) 507 Nantucket (Shoal and Town) 5
Henlopen
Nassau (N. P.)

7 5 Henry 41 New Bedford

5 Look Out 9 Newburyport

10 6 New Haven

8 St. Mary

14 Newport Sable

9 NEW YORK Split (Bay of Fundy) 55 Partridge Island (Bay of Fundy) 55 CHARLESTON (S. C.) 6 Passamaquoddy River

25 Penobscot River

10 71 of the Bay of Fundy

Plymouth

11! Digby (N. S.) 30 Portland .

9 Eastport

25 Port Homer Elizabeth Isles

5

Hood
Town Point

5
Jackson

8 Florida Keys :

Roseway

8 Gay Head (Vineyard) 5 Portsmouth (N. H.).

10 George's River

9 Prince Edward's Islands . 6 Georgetown Bar 4 Providence

5 Goldsborough

12 Rhode Island Harbour Green Islands 16 Salem (Mass.)

11 Gut of Annapolis 30 Sandwich Bay

8 Gut of Cansor

8 Sandy Hook Halifax 8 Seven Isles Harbour

31 Hillsborough Inlet 5 Sheepscut River

9 Holmes' Hole

5 Shubenacadie River (B. of Fun.) 70 John's, St. (N. B.)

30 Simon's, St., Bar St. (N. F.)

7

Sound Kennebec

9 Townsend Harbour Kennebunk 9 Truro (Bay of Fundy)

70 Long Island Sound 5 Vineyard Sound

5 Louisburg (C. B.)

51 Windsor (Bay of Fundy) 60 Machias 12 Woods' Hole

5 Marblehead 11 Yarmouth (N. S.)

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TIDE TABLE. The following Table contains the difference between the time of high water at Boston, and at a large number of places on the American coast, from which the time at any of them may be easily ascertained, by subtracting the difference at the place in question from the time at Boston, when the the sign — is prefixed to it, and by adding it, when the sign ist.

The time of high water, in the calendar pages, is of that tide immediately preceding the southing of the moon.

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