The page of history informs us, that there have been periods, when the sun has wanted of its accustomed brightness, shone with a dim and obscure light for the space of a whole year. This obscurity has been supposed to arise from his surface being at those times covered with spots. Spots have been seen that were much larger than the earth.

The sun is supposed to have an atmosphere, which occasions that appearance which is termed the zodical light. This light is seen at some seasons of the year, either a little after sun-set, or a little before sun-rise. It is faintly bright, and of a whitish colour, resembling the milky way. In the morning it becomes brighter and larger, as it rises above the horizon, till the approach of day, which diminishes its splendor, and renders it at last invisible. Its figure is that of a flat or lenticular spheroid, seen in profile. The direction of its longer axis coincides with the plane of the sun's equator. But its length is subject to great variation, so that the distance of its summit from the sun, varies from 45 to 120 degrees. It is seen to the best advantage about the solstices. It was first described and named by Cassini, in 1683; it was noticed by Mr. Childrey, about the year 1659.

OF THE INFERIOR PLANETS,

MERCURY AND

VENUS.

OF MERCURY.

Of all the planets, Mercury is the least; at the same time, it is that which is nearest the sun. It is from his proximity to this globe of light, that he is so seldom within the sphere of our observation, being lost in the splendor of the solar brightness; yet it emits a very bright white light. It is oftener seen in those parts of the world, which are more southward than that which we inhabit; and oftener to us than to those who live nearer the north pole; for the more oblique the sphere is, the less is the planet's elevation above the horizon.

Mercury never removes but a few degrees from the sun. The measure of a planet's separation, or distance, from the sun, and is called its elongation. His greatest elongation is never more than 28 degrees, or about as far as the moon appears to be from the sun, the second day after new moon. In some of its revolutions, the elongation is not more than 18 degrees.

Mercury is computed to be 37 millions of miles from the sun, and to revolve round him in 87 days, 23 hours, and nearly 16 minutes, which is the measure of its year, about one fourth of our's. As from the nearness of this planet to the sun, we neither know the time it revolves round its axis, nor the inclination of that axis to the plane of its orbit, we

are necessarily ignorant of the length of its day and night, or the variety of seasons it may be liable to. Mercury is 3000 miles in diameter. Large as Mercury, when thus considered, appears to be, it is but an atom when compared with Jupiter, whose diameter is 90,000 miles. Its apparent diameter, at a mean distance from the earth, is 20 seconds.

Mercury is supposed to move at the rate of 110,680 miles per hour. The sun is above 26,000,000 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 its disc, or face, about seven times the size we see it. As the other five planets are above Mercury, their phenomena will be nearly the same to it as to us. Venus and the earth, when in opposition to the sun, will shine with full orbs, and afford a brilliant appearance to the Mercurian spectator.

Mercury, like the moon, changes its phases, according to its several positions with respect to the sun and earth. He never appears quite round or full to us, because his enlightened side is never turned directly towards us, except when he is so near the sun as to become invisible. The times for making the most favourable observations on this planet are, when it passes before the sun, and is seen traversing his disc in the form of a black spot: this passage of a planet over the face of the sun is called a transit. It happens in its lower conjunction, at a particular situation of the 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 16' 59'; the node from which Mercury ascends northward, above the plane of the ecliptic, is 16 1' 30"; in Taurus, the opposite one, 14° 1 24"; in Sagittarius, its nodes move forward about 50 per year.

If Mercury, at his inferior conjunction, comes to either of his nodes about these times, he will appear to transit over the disc of the sun. But in all other parts of his orbit his conjunctions are invisible, because he either goes above or below the sun.

OF VENUS. 오.

Venus is the brightest and largest, to appearance, of all the planets, distinguished from them all by a superiority of lustre; her light is of a white colour, and so considerable, that in a dusky place she projects a sensible shade.

The diameter of Venus is 7,699 miles; her distance from the sun is 69,500,000 miles; she goes round the sun in 224 days, 16 hours, 49 minutes, moving at the rate of 80,995 miles per hour. Her motion round her axis has been fixed by some at 23 hours, 22 minutes; by others, at above 24 days. She, like Mercury, constantly attends the sun, never departing from him above 47 or 48 degrees. Like Mercury, she is never seen at midnight, sition to the sun, being visible only for three or four hours in the morning or evening, according as she is before or after the sun.

oppo

One would not imagine that this planet, which appears so much superior to Saturn in the heavens, is so inconsiderable when compared to it; for the diameter of Saturn is nearly 78,000 miles; while, on the other hand, one would scarce imagine that Venus, which appears but as a lucid spangle in the heavens, was so large a globe as she truly is; her diameter being 7,699 miles. It is the distance which produces these effects; which gives and takes away the magnitude of things. Her apparent size varies with her distance; at some seasons she appears near 32 times larger than at others.

When this planet is in that part of its orbit which is west of the sun, that is, from her inferior to her superior conjunction, she rises before him in the .morning, and is called phosphorus or lucipher, or the morning star. When she appears east of the sun, that is, from her superior to her inferior conjunction, she sets in the evening after him; or, in other words, shines in the evening after he sets, and is called hesperus or vesper, or the evening star.

The inhabitants of Venus see the planet Mercury always accompanying the sun; and he is to them, by turns, an evening or a morning star, as Venus is to To the same inhabitants, the sun will appear almost twice as large as he does to us.

us.

Venus, when viewed through a telescope, is seldom seen to shine with a full face; but has phases, just like the moon, from the fine thin crescent to. the enlightened hemisphere. Her illuminated part is constantly turned towards the sun; hence its