26,109,963 times as big as Mercury; so that it would appear to the inhabitants of Mercury nearly three times larger than it does to us; and it's difk, or face, about feven times the fize we fee it. As the other five planets are above Mercury, their phænomena will be nearly the fame to it as to us. Venus and the earth, when in oppofition to the fun, will fhine with full orbs, and afford a brilliant appearance to the Mercurian spectator.

Mercury, like the moon, changes it's phases, according to it's feveral pofitions with respect to the fun and earth. He never appears quite round or full to us, because his enlightened fide is never turned directly towards us, except when he is fo near the fun, as to become invifible. The times for making the most favourable observations on this planet, are, when it paffes before the fun, and is feen traverfing his difk, in the form of a black spot. This happens in it's lower conjunction, at a particular fituation of it's nodes; which leads us to mention their place in the ecliptic.

The angle formed by the inclination of the orbit of Mercury with the plane of the ecliptic, is 6o 54 min.; the node from which Mercury afcends northward, above the plane of the eclip

tic, is in the 14th degree of Taurus; the oppofite one in the 14th degree of Scorpio. The earth is in these points on the 6th of November, and the 4th of May. If Mercury, at his inferior conjunction, comes to either of his nodes about these times, he will appear to TRANSIT over the difk of the fun. But in all other parts of his orbit his conjunctions are invifible, because he either goes above or below the fun.

OF VENUS. Q

Venus is the brightest and largest, to appearance, of all the planets, diftinguished from them all by a fuperiority of luftre; her light is of a white colour, and so confiderable, that in a dusky place fhe projects a fenfible fhade. Milton takes notice of her fuperior luftre, in defcribing his evening in Paradife, thus:

"Now came ftill Ev'ning on, and Twilight grey Had in her sober liv'ry all things clad ;

Silence was pleas'd: NOW GLOW'D THE FIRMA

MENT

WITH LIVING SAPHIRES: HESPERUS, THAT LED

THE STARRY HOST, RODE BRIGHTEST; till the

moon,

Rifing in clouded majefty, at length,

Apparent

Apparent queen, unveil'd her peerless light,
And o'er the dark her filver mantle threw."

The diameter of Venus is 9330 miles; the contains 273,472,824 fquare miles; her distance from the fun is 68,891,486 miles; fhe goes round the fun in 224 days, 17 hours, moving at the rate of 80,295,24 miles per hour. It's axis iş inclined to the plane of it's orbit, in an angle of 75 degrees. Her orbit makes an angle of 3° 20 min. with the ecliptic; one node is at the 14th degree of Gemini, the other in Sagittarius. Her motion round her axis has been fixed by fome at 23 hours; by others at above 24 days. She, like Mercury, constantly attends the fun, never departing from him above 47 or 48 degrees. Like Mercury, fhe is never feen at midnight, or in oppofition to the fun, being visible only for three or four hours in the morning, or evening, according as the is before or after the fun.

One would not imagine that this planet, which appears fo much fuperior to Saturn in the heavens, is fo inconfiderable when compared to it; for the diameter of Saturn is 78,000 miles; while, on the other hand, one would scarce imagine

that

that Venus, which appears but as a lucid fpangle in the heavens, was fo large a globe as fhe truly is, her diameter being 9330 miles. It is the distance which produces thefe effects; which gives and takes away the magnitude of things.

When the

When this planet is in that part of it's orbit which is weft of the fun, that is, from her inferior conjunction to her fuperior, fhe rifes before him in the morning, and is called PHOSPHORUS, or LUCIFER, or the MORNING STAR. appears east of the fun, that is, from her superior conjunction to her inferior, fhe fets in the evening after him; or in other words, fhines in the evening after he fets, and is called HESPERUS, or VESPER, or the EVENING STAR,

The inhabitants of Venus will fee the planet Mercury always accompanying the fun; and he will be to them, by turns, an evening or a morning ftar, as Venus is to us. To the fame inhabitants, the fun will appear almost twice as large as he does to us.

Venus, when viewed through a telescope, is feldom feen to fhine with a full face; but has phafes, juft like the moon, from the fine thin crefcent to the enlightened hemifphere.

Her

illuminated part is conftantly turned towards the fun; hence it's horns are turned towards the east when it is a morning ftar, and towards the west when it is an evening star.

We are told, that, when Copernicus first publifhed his account of the folar fyftem, it was objected to him that it could not be true, because if it was, the inferior planets must have different phases, according to their different fituation with respect to the fun and earth; whereas they always appear round to us. The anfwer faid to be made by him, is, that they appear round to the eye by reason of their distance; but if we could have a nearer, or more diftinct view of them, we fhould fee in them the faine phafes we do in the moon. The invention of telescopes is faid to have verified this prediction of Copernicus.

'But it is neither probable, that a defender of the Ptolemaic fyftem fhould make fuch an objection, or Copernicus fuch an anfwer; fince in, the Ptolemaic, as well as in the Copernican fyftem, the fhape of these planets ought to change, juft as the moon does; confequently, the mere change of fhape in the inferior planets is an argument, which, in the common way of urging