but we can obferve the inftant of his coming to the meridian, and his meridional altitude; we can also compute what point of the starry heaven comes to the fame meridian, at the fame time, and with the fame altitude. The fun muft be at that point of the ftarry heavens thus difcovered. Or we can observe that point in the heavens, which comes to the meridian at midnight, with a declination as far from the equator on one fide, as the fun's is on the other fide; and it is evident, the fun must be in that part of the heavens, which is diametrically oppofite to this point. By either of these methods we can ascertain a series of points in the heavens, through which the fun paffes, forming a circle called the ECLIPTIC.*

OF THE APPARENT PHENOMENA OF THE MOON.

The motion of the moon through the heavens, and her appearance therein, are still more remarkable than thofe of the fun.

At the new moon, or when fhe firft becomes visible, she is seen in the western part of the heavens, at no great distance from the fun. She increases

* The conformity of this definition of the ecliptic, with that given in page 19, will be seen hereafter.

increases every night in fize, and removes to a greater distance from the fun, till at last fhe she appears in the eastern part of the horizon, when the fun is disappearing in the western. After this, the gradually removes further and further eastward, till at laft she feems to approach the fun as nearly in the east as fhe did before in the west, and rises a little before him in the morning; whereas in the first part of her course fhe fet in the weft, long after him. All these different appearances happen in the space of a month; after which they re-commence in the fame manner.

There is fometimes an irregularity in thefe appearances, particularly in harvest-time, when the moon appears for feveral days to be ftationary in the heavens, and to preferve nearly the fame distance from the fun; in confequence of which, fhe rifes at that feason of the year nearly at the ame hour for feveral nights.

OF THE APPARENT MOTION OF THE STARS.

In contemplating the stars, it is obferved that fome among them have the fingular property of neither rifing in the east, nor fetting in the weft; but seem to turn round one immoveable point,

near

near which is placed a single star, called the POLE,

or POLE STAR.

This point is more or less elevated, according to the part of the earth from which it is viewed. Thus to the inhabitants of Lapland it is much more vertical, or elevated above the horizon, than with us: we fee it more elevated than the inhabitants of Spain: and these again fee it more elevated than thofe of Barbary. By continually travelling fouthward, we fhould at last fee the pole star depreffed to the horizon, and the other pole would appear in the fouth part of the horizon, round which the stars in that part would revolve. There is, however, no ftar in the fouthern hemisphere so near the pole, as that in the northern hemifphere. Supposing us ftill to travel southward, the north pole would entirely disappear, and the whole hemifphere would feem to turn round a single point in the south, as the northern hemisphere appears to turn round the pole ftar.

The general appearance, therefore, of the ftarry heavens, is that of a vast concave sphere turning round two fixed points (diametrically oppofite to each other, the one in the north, the other in the fouth) once in twenty-four hours.

Hence

Hence it is that the stars, though they keep the fame relative places with respect to each other, yet change their fituation very sensibly with respect to the horizon; fome rifing above, others defcending below it; fome that were invisible, now becoming visible; while, on the other hand, many are disappearing. Some never defcend below the horizon; although as they turn round, they are sometimes nearer to, at others further from it, describing whole circles about a point above it. If the observer turns himself round, he will find fome stars rife only as it were to fet again; many defcribing small arcs, and others larger ones.

THE APPEARANCES OF THE PLANETS.

Befides the fixed stars, there are other bodies in the heavens, which are continually changing their places, both with respect to the stars, and one another; these are called PLANETS.

They move among the figns of the zodiac, never departing far from the ecliptic.

Their apparent motion is very irregular, confufed, and perplexed; fometimes they appear as

going forwards, fometimes backwards, and at others are flationary.

MERCURY emits a bright white light, but keeps fo near the fun, that he is very feldom vifible; and when he does make his appearance, his motion towards the fun is fo fwift, that he He can only be difcerned for a fhort time. appears a little after fun-fet, and again a little before fun-rife.

VENUS is the most beautiful star in the heavens, known by the names of the morning and evening ftar. She also, like Mercury, keeps near the fun, though the recedes from him much further. She, like him, is never feen in the eastern quarter of the heavens, when the fun is in the western; but always either attends him in the evening, or gives notice of his approach in the morning.

MARS is of a red fiery colour, giving a much duller light than Venus, though he fometimes appears almoft equal to her in fize. He is not fubject to the fame limitations in his motions as Venus and Mercury, but appears fometimes very near the fun, at others at a greater diftance from

him,