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Eclipses of the Satellites.

Jupiter is too near the sun to admit of any of these being visible.

Saturn in opposition at 30 min. after 6 of the morning of the 2nd.

FORM OF SATURN'S RING.
March 21st.-Semi-transverse axis

Semi-conjugate axis

45".46

4 .13

There is every reason to conclude that a more vigilant examination of the planet Saturn, by skilful observers, with exquisite instruments, would be amply repaid by extensive discoveries connected with its mysterious structure. It has only recently been observed that the ring is not concentric with the globe of Saturn, the orb being nearer to the western than the eastern side from a mean of fifteen observations, by professor Struve, it is found that the interval between the outer edge of the globe, and the outer edge of the ring, on one side, is 11".073, and on the other side, the interval is 11".288; consequently there is an eccentricity of the globe in the ring equal to 0".215. It is suspected that the outer ring is separated by numerous dark divisions, extremely close to each other, exhibiting such an appearance as though the ring were formed of several small rings in the same plane. These divisions, which are occasionally very distinctly seen, are at other times not to be perceived, though the various circumstances with a favorable atmosphere continue the same. This has suggested the idea, that the outer ring has a very dense yet variable atmosphere, which occasionally intercepts or affords a view of these divisions. The external ring is not so bright as the internal; and the inner edge

of the internal ring is less bright than the outer parts, and resembles the planet in color: the edges of the ring appear to be rounded.

Sphere of the Fixed Stars.

Altitudes of the stars at the Vernal Equinox at 30 min. after 8 in the evening.

Lynx in the Zenith. Leo Minor, 55°. Coma Berenices, 30°. Cor Caroli, 36°. Arcturus, 10°. Sextans Hadlieanus, 30°. Alphora in Hydra, 25°. Procyon, 44°. Monoceros, 40°. Sirius, 20°. Lepus, 15o. Rigel, 22°. Betelgeux, 41°. Belt of Orion, 31°. Star in the summit of the southern horn of Taurus, 51°. Aldebaran, 29°. Hyades, 28°. Menkar, 15°. Arietis, 12°. Musca Borealis and Triangula, 20°. Algol, 331°. Algenib, 41°. Mirach, 13°. Almaach, 25°. Capella, 65°.

TELESCOPIC OBJECTS.

Orion. This is the most splendid and interesting constellation in the heavens. Bellatrix and Betelgeux, the stars that form the shoulders of Orion, present a remarkable contrast of color,-the latter shines with a fiery scintillating light.

stars.

Double Stars. 8, 4, n, λ, p, and Rigel in the left foot of Orion; 23, 26, 32, 33, 38, 52, 59, and 68, are also double stars; west of Betelgeux are two double Between A and Betelgeux is a cluster of stars; Χ is composed of five stars; between v and is a cluster of stars; another cluster is near 73. σ and are quintuple stars. is a multiple star. A little below, in the sword of Orion, is the most remarkable nebula in the heavens.

COMETARY ASTRONOMY.

To facilitate the explanation of the phenomena of comets, it is proposed to point out those peculiarities in which they resemble, and those in which they differ from planets.

The following diagram will illustrate some of the terms employed in this branch of Astronomy.

M

S

N

The place

The ellipse is intended to represent the orbit of a comet; the sun is situated in one of the foci, S. The major axis, P A. Semi-axis major, PO. of perihelion, P. Perihelion distance, PS. of aphelion, A. Aphelion distance, A S. axis, MN. The eccentricity, O S.

Comets and Planets.

The place The minor

Planets perform an apparent revolution round the earth in twenty-four hours; this is also the case with comets during the time of their being visible. This

apparent revolution is caused by the rotation of the earth about its axis, from west to east, and this real motion occasions the sun, moon, planets, comets, fixed stars, and the whole frame of nature to appear to revolve in an opposite direction, or from east to west.

Comets perform their revolutions round the sun, as the centre of their motions, as also the planets; but the orbits of comets are very elliptical, and those of planets nearly circular.

Planets and comets both obey the same laws in pursuing their respective courses round the sun, and though the shapes of their orbits are very dissimilar, yet each revolves round the central body in an ellipse, the sun occupying one of the foci of the ellipse: also that lines drawn from the sun to the planet or comet, sweep over equal areas, in equal portions of time, and that the squares of the times of revolution are as the cubes of the mean distances of the comet or planet from the sun.

Planets and comets are opaque bodies, and shine only by the light emitted from the sun : this is evident from the phases exhibited by the moon, Venus, Mercury, and Mars, when in situations where parts of their unenlightened orbs are turned to the earth. This appearance has also been observed in comets, particularly the one which is expected in 1835. Comets, also, have been observed to transit the sun's disc, which interesting phenomenon was observed in one that appeared in 1819; its appearance, when on the disc, was that of a nebulous spot; this comet also exhibited phases; these are sufficient proofs, that comets are not self-luminous, but like the planets, shine only by reflected light.

Planets and comets have atmospheres; those of the

latter, however, are very considerable, and stream off in a direction opposite to the sun. In these, and some other particulars, there is sufficient resemblance between planets and comets to prove that they are both members of the same family, of which the centre is the sun.

In many points, however, there is a great dissimilarity between planets and comets;-a planet may be traced through the whole of its path round the sun,-through every degree of its course, without losing sight of it, excepting for a short time before and after its conjunction with the sun, and even this has been done with the planet Venus, but comets, on the contrary, enter at one part of the heavens, and disappear at a place not very remote from the first place of observation. This was the case with the comet of Encke; it was dimly recognized in Pegasus, passed through Equuleus, entered Antinous, and then became invisible in the solar rays. The longest track of any comet on record is that of 1820, observed by Captain Basil Hall at Valparaiso, for three months, in which time it described a curve equal to 300°.

Planets, as they keep through the whole of their annual courses, at nearly the same distances from the centre of the system, vary but little in their apparent magnitudes, as seen from the sun, and with the exception of Venus and Mars, not very considerably as seen from the earth :-Comets, on the contrary, at first appear very small, and gradually increase in size: the comet of 1769 will afford an example,—it appeared at first like a minute nebula, rapidly increased in size as it advanced, and when at its maximum, the coma surrounding the head was equal to a degree, or twice the apparent dia

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