1. Whether the star undergoes any change of light, of colour, or of motion, on its immediate approach to the edge of the moon.

2. Whether it appears to be projected on the moon's disc, and if so for how long a time.

3. Whether the dark limb of the moon be distinctly visible, and well defined, at the time of the phenomenon.

4. Whether the star, on its emersion, appears on the moon's disc, or emerges quite clear of the moon's border.

In the occultation of this star, at Boston, August 21 and 22, 1829, the star, at the immersion, did not appear to undergo any change of light, or to be projected on the moon, but was so tremulous, that there was an uncertainty of two seconds in the time of its disappearance; but its emersion was instantaneous.

The elements of the eclipses and of the occultations (with the exception of the places of the stars) were computed from the Berlin Astronomisches Jahrbuck for 1830, edited by the celebrated Encke, a work far superior, both as to matter and arrangement, to any thing of the kind hitherto published.

Appulses of the Moon to Stars in 1830, calculated for Boston; all or nearly all of which will be Occultations in some part of the United States.

Equat. of time.+13 45.2+10 50.56 29.5+ 3 40.6

0 30.65 19.1

H. M. of equat. dec. 0.3 dec. 0.7\dec. 0.8 dec. 0.5 inc. 0.8 inc. 0.9

9.1

9.3

m. s.

9.0

Long. of

a 8.

June 2, 12h.
z mp.

Long. of D.

H. M.

Lat. of D.

37 1.0 s. 4 58 14.3

+ 29.0
60 18.1

32 51.6

1.4 16 25.9

h. m. S.
3 55 43.0

10.0

0.4

1.4 15 29.0

- 2 22.6

+4 13.7

15 18.2

+ 4 50.4 inc.

10.2

0.4

29 43.0

67° 24' 13.4" 2120 7 43.6" 285° 59' 12.9" 339° 12′ 38.7"

s. 5° 28′ 45.5" n. 2° 55′ 15.3" n. 3° 16′ 53.5" s. 0° 22′ 54.1" 67 18 51.4 211 34 47.0286 30 31.2 338 56 13.3

34 36.9 n. 3 37 51.0 n. 4 10 49.3n.0 13 57.5

July 5, 20h.
d.

df.

54 4.6

In the computation of the preceding eclipses of the sun and occultations, the ellipticity of the earth was assumed to be one three-hundredth, and the semidiameter of the sun was diminished 34" for irradiation, and that of the moon 2" for inflexion, according to the theory of Dusejour.

The elements are given in apparent time for the meridian of Greenwich, reckoned according to the manner of astronomers from noon to noon. When apparent is to be converted into mean time, the equation of time must be applied with the sign prefixed to it, but when mean time is to be reduced to apparent, the sign of the equation must be reversed.

No sign is prefixed to the hourly motion of the moon in longitude, or of the sun in right ascension (A R), as they are always additive.

In the computation of an eclipse of the sun, or of an occultation, for any place, the latitude of the place and the moon's equatorial parallax must be reduced for the ellipticity of the earth, which is generally supposed to be one three-hundredth; these reductions will be found in the 38th table of the "New American Practical Navigator," or they may be computed by the following formulæ.

Let L be the latitude and R the reduction of the latitude, then log. cotang. (L-R) = 0,0029001+ log. cotang. L. The reduction of equatorial parallax, (57' for example,) may be found thus, 5.7-5.7" cos. 2 L.

ECLIPSES OF THE SATELLITES OF JUPITER IN 1830, Visible in the United States; the phases of which are expressed in mean solar time for the meridian of Washington (5h. 7m. 42s. west of Greenwich), reckoned, according to the manner of Astronomers, from

The eclipses before the opposition of Jupiter on the 5th of July, will take place on the west side of the planet, and afterwards on the east. The immersions only, of the 1st and 2d satellites will be visible before the opposition, and the emersions only, after; 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 lost in the rays of the Sun.

Eclipses of these satellites, particularly of the first and second, are very useful in determining, to a very considerable degree of accuracy, the longitude 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, in obtaining it by the latter method; they have likewise the additional advantage of being of very frequent oc

currence.

To determine the time at which either of the preceding eclipses will take place, on any other meridian than that of Washington, it is necessary, merely to add four minutes for every degree of longitude less than 76° 55' 30", and subtract the same quantity for every degree greater. For Boston, add 23m. 25s.; for New York, 11m. 38s. For Charleston, subtract 11m. 30s.; for Cincinnati, 30m. 6s.; for New Orleans, 52m. 54s.