that the diurnal revolution was performed in 24 hours and 40 minutes, agreeing very nearly with the subsequent observation of Dr. Herschel. The belts and cloudy appearances on this planet are found to change their shape and arrangement very frequently. With regard to the bright polar spots, Dr. Herschel observes, that the poles of the planet are not exactly in the middle of them, though nearly so. From the appearance and disappearance of the bright north polar spot of the year 1781, we collect, that the circle of its motion was at some considerable distance from the pole. By calculation its latitude must have been about 76 or 77 degrees north. The south pole of Mars could not be many degrees from the centre of the large bright southern spot of 1781; though this spot was of such a magnitude as to cover all the polar regions farther than the seventieth or sixty-fifth degree. TABLE. Heliocentric longitude on the 1st of Ja nuary, 1825, 11s. 9° 33′0′′ Geocentric longitude at the same time, 10 15 39 0 Longitude of the perihelion on the 1st of January, 1801, Longitude of the ascending node, at the same time, Inclination of the orbit to the ecliptic, Eccentricity in miles, The secular motion of the apsides is 1° 49′ 52", in longitude according to the order of the signs. The place of the nodes is liable to a direct secular variation in longitude of 44' 41". The inclination of the orbit to the ecliptic is subject to a small decrease of about 11⁄2" in one hundred years. The greatest equation is subject to a small diminution of about 37" in a century. The following particulars respecting Mars are given, by Dr. Herschel, after long and accurate observations. 1. The node of the axis of Mars is in 11s. 17° 47', or 170 47' of Pisces. 2. The obliquity of the ecliptic on the globe of Mars, is 280 42. 3. The point zero (0,) or the point of the sign Aries, on the martial ecliptic, answers to our Ss 19° 28', or 19° 28' of Sagittarius. From these and some previous observations, it appears that the analogy between Mars and the Earth is greater than between the Earth and any other planet of the solar system. Their diurnal motion is nearly the same; the obliquity of their respective ecliptics, on which the seasons depend, are not very different; and of all the superior planets, the distance of Mars from the Sun is by far the nearest alike to that of the Earth; nor is the length of its year very different from ours when compared with the years of Jupiter, Saturn, and Uranus. QUESTIONS. At what rate does Mars move in its orbit? In what time does Mars perform a complete revolution on its axis ? In what proportion is the polar diameter of Mars to its equatorial? What is the inclination of the orbit of Mars to the ecliptic? How many seconds is the mean apparent diameter of Mars? What is the greatest apparent di ameter? What else is worthy of notice in this planet? CHAPTER IX. Of the New Planets, or Asteroids, Vesta, Juno, Ceres, and Pallas. 1. Vesta is the next planet, after Mars, in the order of distance from the sun; and it performs its sidereal revolution in 1335 days, 4 hours, 55 minutes, and 12 seconds, which is the length of the planet's year. Its relative mean distance from the sun is 24, that of the earth being considered as 10. The greatest distance of Vesta from the sun, in miles, is reckoned Longitude of the perihelion, 246,450,053 204,419,947 225,435,000 21,015,053 44,202 Ss. 27°25′ 1" 8 9 43 0 : 0 7 8 46 Mean longitude 1st of January, 1801, Longitude of ascending node, 2. The inclination of the orbit of Vesta to the plane of the ecliptic is 7o 8′ 46′′. The apparent diameter of this planet is not quite half a second ; and its real diameter is supposed to be 238 miles, but according to the observations of Schroeter it is much greater. In a clear evening this planet may be seen by the naked eye, like a star of the sixth magnitude, of a dusky colour, similar in appearance to Uranus. Vesta shines with a purer light than any of the minor planets. This planet was discovered by Dr. Olbers, at Bremen, on the 29th of March, 1807. 3. Juno is the next planet, after Vesta, in the order of distance from the sun, and it performs its sidereal revolution round the sun in 1590 days, 23 hours, 57 minutes, and 7 seconds, which is the length of the planet's year. Its relative mean distance from the sun is 27, that of the earth being considered as 10. The greatest distance of this planet from the sun, in miles, is Its least distance, 316,968,828 189,792,142 41,170 4. The inclination of the orbit of Juno to the plane of the ecliptic is 13° 3′ 28′′. The real diameter. of this planet, according to Schroeter, is about 1425 miles; and its apparent diameter is about 3.057". Juno is of a reddish colour, and appears sometimes very brilliant. This planet, according to the observations of Schroeter, is surrounded by an atmosphere more dense than that of any of the planets; and he also remarks, that the variation in the brilliancy of this planet is chiefly owing to certain changes in the density of its atmosphere, though he thinks it not improbable that these changes may arise from a diurnal rotation performed in 27 days. The planet Juno was discovered by Harding, at the observatory of Lilianthel, near Bremen, on the evening of the 1st of September, 1804, while he was making a catalogue of all the stars which were near the orbits of Ceres and Pallas. 5. Ceres is the next planet, after Juno, in the order of distance from the sun; and it performs its sidereal revolution in 1681 days, 12 hours, 56 minutes, and 10 seconds, which is the length of the planet's year. Its relative mean distance from the sun is 28, that of the earth being considered as 10. The greatest distance of this planet from the sun, in miles, is Its least distance, Its mean distance, Mean hourly motion, Mean longitude 1st of January, 1801, Longitude of the perihelion, 6. The inclination of the orbit of Ceres to the plane of the ecliptic is 10° 37′ 34"; its real diameter, according to Dr. Herschel, is only 163 miles, but Schroeter makes it 1624 miles; and its apparent diameter is about 1 second. Ceres is not visible to the naked eye; but when observed by a telescope, appears of a ruddy colour, and about the size of a star of the eighth magnitude. It also seems to be surrounded by an extensive and dense atmosphere; but when examined by a telescope, which magnifies it above two hundred times, its disc may be very distinctly perceived. Ceres was discovered on the 1st of January, 1801, by M. Piazzi, of Palermo in Sicily. He continued to observe the planet till the 13th of February, when he was obliged by illness to discontinue his observations. M. Piazzi then transmitted accounts of his observations to several celebrated astronomers, in order that they might calculate the orbit of the new star, and trace out its progress in the heavens; but it eluded every search that was made for it, until December 7th, when it was re-discovered by the assiduous Dr. Zach, of Saxe-Gotha; and soon after it was observed by Dr. Olbers, at Bremen; by Mechain, at Paris; by the royal astronomer, at Greenwich; by Dr. Herschel, at Slough; and by various other astronomers. 7. Pallas is the next planet, after Ceres, in the order of distance from the sun; and it performs its sidereal revolution in 1681 days, 17 hours, and 58 seconds, which is the length of the planet's year. Its relative mean distance from the sun is not much more than 28, that of the earth being considered as 10. The greatest distance of this planet from the sun, in miles, is Its least distance, Its mean distance, Eccentricity of its orbit, 327,437,913 Mean hourly motion, Mean longitude 1st of January, 1801, Longitude of the perihelion, |