6th last, was 178° 29′ right ascension, and 18° 10' north declination.

On the 28th of March, 1802, a remarkable discovery of another new planetary body was made by Dr. Olbers, of Bremen, in Germany; it is of small apparent magnitude, and then formed an equilateral triangle with the stars 20 and 19 of Virgo; he found it had a perceptible change of place, and the following observations were communicated by him of it, to an astronomer, Dr. Schroeter.

1802. March 28d 9h 25′ 10′′ mean time

App. R. Ascen. 184° 56′ 49′′

App. Declin.

29 8 49′ 14′′ M. T. App. R. A. 184

App. Declin.

46 36

Dr. Olbers did not observe any sensible disc; in comparison to Ceres, its light was pale and white, and less bright than the Georgium Sidus; he has given it the name of Pallas. From calculations made by Dr. Gauss, founded upon a set of observations by Baron de Zuch, it appears that it is a planetary body moving between the orbits of Mars and Jupiter, with a very great eccentricity and inclination, and whose orbit comes very near to the orbit of the planet Ceres. Dr. Herschel, from his observations upon this planetary body, judges the apparent diameter to be rather less than Ceres, about 13" or 17", and its diameter in English miles 93 or 71, and that of Ceres 163, to have a colour less ruddy than Pallas; both this and Ceres, to have generally comas or haziness about them, he thinks

OF CERES, PALLAS, JUNO, AND VESTA. 57

great

that they both differ from the general character of planets in their diminutive dimensions, in their inclination of their orbits, in the comas surrounding them, and in their mutual proximity of their orbits; that they differ from comets in their defect of eccentricity, and of a considerable nebularity.

Pallas, like Ceres, will not be sufficiently apparent till January next (1803). Baron de Zuch has given us the positions for the 29th of June last (1802) as follows, 188° 32′ right ascension, and 19°6′ N. declination, and observes that it may be difficult to find Pallas next year; for the elements of an orbit calculated upon so small an arc as 71⁄2o, may give an error of several degrees in January, 1803.

10

Dr. Herschel, from his observations of these two bodies, considers them as holding a middle rank between planets and comets, and has denominated them Asteroids. Philosophical Transactions, 1802. On this account, I shall forbear the insertion of the several published tables of the motions of these two planets, as calculated upon the elements computed by various ingenious astronomers.

Mr. Harding, of Libenthal, in Bremen, discovered, on the 1st of September, 1804, another kind of planet, which has been named Juno, with an appearance like a star of the eighth magnitude. This and the preceding two have been judged to be nearly equidistant from the sun.

Dr. Olbers, on the evening of the 29th of March, 1807, discovered another planet, which has been named Vesta. Its right ascension then was 184 8',

and declination 11° 47′ W. similar to a star of the 5th magnitude, and not ascertained to be at a distance different from the three others.

The places of the Georgium planet, only, are annually published in the Nautical Ephemeris, and that of White's; and it can only be from a continued series of accurate observations for a length of time, that proper data can be obtained to construct true elements from.

AN

EXPLANATION

OF VARIOUS

PHENOMENA,

AGREEABLE TO THE COPERNICAN SYSTEM.

Having given a general idea of the Copernican system, and the bodies of which it is composed, it will be necessary to enlarge these ideas by a more minute description of the particular parts which form this great whole; and to strengthen them by the force of that evidence, on which the system is founded.

OF THE FIGURE AND MAGNITUDE OF THE EARTH.

The places of the heavenly bodies could not be settled with accuracy from observations made on the surface of the earth, unless its figure and magnitude were previously known; and, without this knowledge, computations from the observations of the heavenly bodies, for ascertaining the situation of places on the earth, could not be depended on.

I have already observed, that the appearance of the heavenly bodies is not the same to the inhabitants of various parts of the earth; that the sun, the moon, and the stars, rise and set in Greenland in a manner very different from what they do in the East Indies, and in both places very different to what they do in England: and, as it was natural to attribute the cause of this change in the apparent face of the heavens to the figure of the earth (for appearances must ever answer to the form and structure of the things), the nature of this figure was, therefore, one of the first objects of inquiry among philosophers and astronomers.

Some of the sages of antiquity concluded, that the earth must necessarily be of a spherical figure, because that figure was, on many accounts, the most convenient for the earth, as an habitable world: they also argued, that this figure was the most natural; because any body exposed to forces, which tend to one common centre, as is the case with the earth, would necessarily assume a round figure. The assent, however, of the modern philosopher to this truth, was not determined by speculative reasoning, but on evidence derived from facts and actual observation. From these I shall select those arguments, that I think will have the greatest weight with young minds.

It is known, from the laws of optics and perspective, that if any body, in all situations, and under all circumstances, project a circular shadow, that body must be a globe.

It is also known, that eclipses of the moon are caused by the shadow of the earth.

And we find that, whether the shadow be projected towards the east or west, the north or the south, under every circumstance it is circular: the body, therefore, that casts the shadow, which is the earth, must be of a globular figure.

We shall obtain another convincing proof of the globular shape of the earth, by inquiring in what manner a person standing upon the coast of the sea, and waiting for a vessel, which he knows is to arrive, sees that vessel. We shall find that he, first of all, and at the greatest distance, sees the top of the mast rising out of the water; and the appearance is as if the ship was swallowed up in the water. As he continues to observe the object, more and more of the mast appears; at length he begins to see the top of the deck, and by degrees the whole body of the vessel. On the other hand, if the ship be departing from us, we first lose sight of the hull, at a greater distance the main-sails disappear, at a still greater the top-sails. But if the surface of the sea were a plane, the body of the ship, being the largest part of it, would be seen first, and from the greatest distance, and the masts would not be visible till it came

nearer.

To render this, if possible, still clearer, let us consider two ships meeting at sea, the top-mast of each are the parts first discovered by both, the hull, &c. being concealed by the convexity of the globe which rises between them. The ships may, in this instance,