extent cannot accord with the Moon, as it has been ascer tained, by eclipses of Sun and stars, that the lunar atmosphere is nearly insensible.

The Moon does not entirely disappear in its eclipse, but is still enlightened by a very faint light that comes to it by the Sun's rays, inflected through the terrestrial atmosphere; and, but for the great absorption of these rays by our atmosphere, its brightness would be more vivid than at the full Moon. We may sometimes distinguish, particularly about the time of a new Moon, that part of the lunar disk which is not enlightened by the Sun : this feeble light is the effect of the light which the illuminated hemisphere of the Earth reflects upon the Moon; what proves this is, that it is most sensible at the time of a new Moon, when the greatest part of this hemisphere is directed to the Moon; for it is clear, that to a spectator in the Moon, the Earth will present a succession of phases, similar to that which the Moon presents to us, but accompanied by a much more intense light from the greater extent of the terrestrial surface,

[To be continued.]

OF THE FOUR NEWLY-DISCOVERED PLANETARY

BODIES,

Ceres, Pallas, Juno, and Vesta,

Ir was believed, till the present century, that the planet Jupiter was next to Mars in the solar system. On the 1st of January*, 1801, the planet Ceres was discovered at Palermo, in Sicily; and since that, at different periods, three other small planetary bodies have been found to exist, whose orbits

The opinion that the immense space between the orbits of Mars and Jupiter must be accomodated with one or more planets had been recently formed by others, particularly Capel Lofft, esq. to whose scientific and literary researches society is greatly indebted.-ed.

are between those of Mars and Jupiter: of these, we shall give an account in their order, according to the dates of their discovery. The planet Ceres, when first seen, was observed to be in Taurus; the nebula, with which it was apparently surrounded, gave it the appearance of a comet ; and it was in consequence of the suggestion of Professor Bode, of Berlin, or of Zack, that Piazzi, and other astronomers, ranked it among the planetary bodies.

The planet Ceres is of a ruddy colour; and, with a proper telescope, it appears about the size of a star of the 8th magnitude. It seems to be surrounded with a large dense atmosphere, and plainly exhibits a disk, when examined with a magnifying power of about 200. This planet is situated between the orbits of Mars and Jupiter. She performs her revolution round the Sun in 4 years, 7 months, and 10 days; and her mean distance from that body is nearly 260 millions of miles. The eccentricity of her orbit is not very great, but its inclination to the ecliptic exceeds that of the old planets. The length of its diameter was thought by Dr. Herschel not to exceed 160 miles; but, according to Schroeter, it is more than ten times that length.

Pallas, the next planet in order, was discovered at Bremen, in Lower Saxony, on the 28th of March, 1802, by Dr. Olbers: the same active astronomer who rediscovered Ceres, after it had been lost to M. Piazzi, and others. Pallas is situated between the orbits of Mars and Jupiter, and is nearly of the same magnitude with Ceres; but, in colour, it is less ruddy: it is surrounded with a nebulosity of almost the same extent, and performs its annual revolution in about the same period. The planet Pallas, however, is distinguished in a remarkable manner from Ceres, and all the other primary planets, by the immense inclination of its orbit. While these bodies are revolving round the Sun, in almost circular paths, rising only a few degrees above the plane of the ecliptic, Pallas ascends above this plane, at an angle of about 35 de

grees. From the eccentricity of Pallas being greater than that of Ceres, while their mean distances are nearly equal, the orbits of these two planets mutually intersect each other, a phenomenon which is altogether without a parallel in the solar system. The diameter of Pallas has not been determined with accuracy: there is, indeed, a great discordancy in the opinions of the English and German astronomers; Herschel making it only 80 miles, while Schroeter makes it no less than 2099 miles.

The planet Juno, the third of the newly-discovered planets, was observed first by Mr. Harding, at the observatory of Lilienthal, near Bremen, on the evening of the 1st of September, 1804. While this astronomer was forming an atlas of all the stars which are near the orbits of Ceres and Pallas, he observed, in the constellation of Pisces, a small star of the 8th magnitude, which was not mentioned in the Histoire Celeste of La Lande; and, being ignorant of its longitude and latitude, he put it down in his chart as nearly as he could estimate with his eye. Two days afterwards, the star disappeared; but he perceived another which he had not seen before, resembling the first in size and colour, and situated a little to the south-west of its place. He observed it again, on the 5th of September; and, finding that it had moved a little farther to the south-west, he concluded, that this star belonged to the planetary system. The planet Juno is of a reddish colour, and is free from that nebulosity which surrounds Pallas: it is situated between the orbits of Mars and Jupiter, like the others just described. Its diameter is less, and its distance greater, than those of the other new planets. It is distinguished from all the other new planets, by the great eccentricity of its orbit; and the effect of this is so very sensible, that it passes over that half of its orbit which is bisected by its perihelion in half the time that it employs in describing the other half, which is farther from the Sun. From the same cause, its greatest distance from the Sun is

double the least distance; the difference between the two distances being about 127 millions of miles. Its mean distance from the Sun is 275 millions of English miles.

It was a century and half ago conjectured, that there must be a planet between the orbits of Jupiter and Mars, on account of the distance subsisting between those two planets. The discovery of Ceres confirmed this happy conjecture; but the opinion which it seemed to establish, respecting the harmony of the solar system, appeared to be completely overturned by the discovery of Pallas and Juno. Dr. Olbers, willing to find a theory that should account for the facts `newly ascertained, imagined, that these small celestial bodies were merely the fragments of a larger planet, which had been burst asunder by some internal convulsion, and that several more might be yet discovered between the orbits of Mars and Jupiter. He, therefore, concluded, that though the orbits of all these fragments might be differently inclined to the ecliptic, yet, as they must have all diverged from the same point, they ought to have two common points of re-union, or two nodes in opposite regions of the heavens, through which all the planetary fragments must sooner or later pass. One of these nodes Dr. Olbers found to be in Virgo, and the other in the Whale; and it was actually in the latter of these regions that Mr. Harding discovered the planet Juno. With the intention, therefore, of detecting other fragments of the supposed planet, Dr. Olbers examined, thrice every year, all the little stars in the opposite constellations of the Virgin and the Whale, till his labours were crowned with success, on the 29th of March, 1807, by the discovery of a new planet, in the constellation of Virgo, to which he gave the name of Vesta.

As soon as this discovery was made known in England, the planet was observed at Blackheath, on the 26th of April, 1807, by Mr. Groombridge, an active astronomer, who continued to observe it, with an excellent astronomical circle,

till the 20th of May, when, from its having ceased to become visible on the meridian, he had recourse to other instruments. He resumed his meridional observations in the month of August, and had the good fortune, on the 8th of September, to observe the ecliptic opposition of the planet.

Accord

The planet Vesta, is of the 5th or 6th magnitude, and may be seen, in a clear evening, by the naked eye. Its light is more intense, pure, and white, than any of the other three. It is not surrounded with any nebulosity, and has no visible disk. The orbit of Vesta cuts the orbits of Pallas, but not in the same place where it is cut by that of Ceres. ing to the observations of Schroeter, the apparent diameter of Vesta is only half of what he found to be the apparent diameter of the 4th satellite of Saturn; and yet, it is very remarkable, that its light was so intense, that Mr. Schroeter saw it several times with the naked eye. The period of its revolution about the Sun, is 1 year and 66 days.

[To be continued.]

SIR,

To the Editor of the Monthly Correspondent.

I CANNOT help expressing much satisfaction at the announce-` ment of your MONTHLY CORRESPONDENT, or a plan so truly liberal, and to shew my gratitude, which every effort made for the promotion of knowledge and happiness merits, I beg your acceptance of something regarding Botany; but, at this time, I shall offer only what must be considered as introductory matter, because I intend to pursue the subject regularly, or, at least, I hope some other person, better qualified than I am, will contribute to so desirable an end. Exertions, united in the way your work opens to every one, cannot fail `of doing infinite service, and attaining the object of natural investigation. I am, Sir, yours, STUDIOSUS.