elipses they describe in their circuit round it. But, although the sun always keeps nearly in the same place, yet it is observed to move round its own axis in about 25 days, 15 hours, and 16 minutes. The principal planets are, MERCURY, VENUS, the EARTH, MARS, JUPITER, SATURN, and the GEORGIUM SIDUS. These all move round the sun in the order just named; Mercury being the nearest to the sun, and the Georgium Sidus, farthest from it. Some of these planets have attendants, called satellites or moons, moving round them. The Earth has one, Jupiter four, Saturn seven, and the Georgium Sidus six. It MERCURY is the smallest planet, but emits a very bright light; though on account of its keeping always near the sun, it is seldom to be seen, and when it does appear, its motion towards the sun is so very swift, that it can only be discerned for a short time. appears a little after sunset, and again a little before sunrise. When this planet is viewed through a good telescope, it appears equally luminous throughout the whole surface. It has different phases like the moon, sometimes horned, sometimes gibbous, and sometimes almost full, but never entirely so; the enlightened side is never turned directly towards us. It makes a revolution round the sun in about 37 days, 23 hours, 14 minutes, and 34 seconds. VENUS is the most beautiful star in the firmament, and is known by the name of the morning and evening star; it is never seen in the eastern quarter of the heavens, when the sun is in the western; it has phases like the moon, and turns round on its own axis, in 23 hours, and 20 minutes : making a revolution round the sun in 224 days, 16 hours, 41 minutes, and 30 seconds. The EARTH, or planet we inhabit, is about 7940 miles in diameter, and 81,000,000 of miles from the sun; it performs a revolution round the sun in 365 days, 5 hours, 48 minutes, and 57 seconds, and revolves round its axis in 23 hours, 56 minutes, and 4 seconds. MARS is of a red fiery colour, and always gives a much duller light than Venus, though sometimes it is equal in size. It appears sometimes near the sun, and at other times at a great distance from it. Mars revolves round its axis in 24 hours and 40 minutes; and performs its revolution round the sun in 321 days, 22 hours, 18 minutes, and 19 seconds. |