piter visible at Greenwich 1 m. past 5 in the morning of the 5th day; and one of the second satellite on the 21st, at 56 m. past 4 in the morning. This time, in both cases, refers to the immersions or commencement of the eclipse. VIEW OF THE SOLAR SYSTEM. Of Saturn. Saturn is a very conspicuous planet, though never so brilliant as Jupiter. The period of his revolution is 10,759 days, or almost 30 years. He moves from west to east nearly in the plane of the ecliptic, and exhibits many irregularities similar to those of Jupiter and Mars. He becomes retrograde both before and after his opposition, when at the distance of about 109° from the Sun. His retrograde motion continues 139 days, and, during its continuance, hè déscribes an arc of about 6o. Saturn, when viewed through a good telescope, makes a more remarkable appearance than any of the other planets. Galileo first discovered his uncommon shape, which he thought to be like two globes, one on each side a larger one. Having viewed him for two years, he was surprised to see him become quite round without these appendages, and then afterwards to assume them as before. These adjoining globes were what are now called the anse of his ring, the true shape of which was first discovered by Huygens, about forty years after Galileo. From the discoveries made by him and other astronomers, it appears that this planet is surrounded by a broad thin_ring, the edge of which reflects little or none of the Sun's light to us, but the planes of the ring reflect the light in the same manner that the planet itself does; and, if we suppose the diameter of Saturn to be divided into three equal parts, the diameter of the ring is about seven of those parts. The ring is detached from the body of Saturn in such a manner, that the distance between the innermost part of the ring and the body is equal to its breadth. Both the outward and inward rim of the ring is projected into an ellipse, more or less oblong according to the different degrees of obliquity with which it is viewed. Sometimes the eye of the observer is in the plane of the ring, and then it becomes invisible; either because the outward edge is not fitted to reflect the Sun's light, or because it is too thin to be seen at such a distance. As the plane of this ring keeps always parallel to itself, it disappears twice in every revolution of the planet; that is, once in about 15 years, and he sometimes appears quite round for nine months together. At other times, the distance between the body of the planet and the ring is very perceptible, so much so, that a star has been, seen through the opening. When Saturn appears round, if our eye be in the plane of the ring, it will seem as a dark line across the middle of the planet's disk; and, if the eye be elevated above the plane of the ring, a shadowy belt will be visible, which is caused by the shadow of the ring, as well as by the interposition of part of it between the eye and the planet. The shadow of the ring is broadest when the Sun is most elevated, but its obscure parts appear broadest when the eye is most elevated above the plane of it. When it seems to be double, the ring next the body of the planet appears brightest; when the ring appears of an elliptical form, the parts about the ends of the largest axis are called ansa, as has been already mentioned. These, a little before and after the disappearing of the ring, are of unequal magnitude: the largest ansa is longer visible before the planet's round phase, and it appears again sooner than the other. On the 1st of October, 1714, the largest ansa was on the east side, and on the 12th on the west side of the disk of the planet, which makes it probable that the ring has a rotation round an axis. Dr. Herschel has shown that it revolves in its own plane in about 10 hours. The observations of this philosopher have added greatly to our knowledge of Saturn's ring. According to him, there is one single, dark, considerable broadline, belt or zone, which he has constantly found on the north side of the ring. As this dark belt is subject to no change whatever, is is probably owing to some permanent construction of the surface of the ring this construction cannot be owing to the shadow of a chain of mountains, since it is visible all round on the ring, for there could be no shade at the ends of the ring: a similar argument will apply against the opinion of very extended caverns. It is pretty evident that this dark zone is contained between two concentric circles, for all the phenomena correspond with the projection of such a zone. The nature of the ring Dr. Herschel thinks no less solid than that of Saturn itself, and it is observed to cast a strong shadow upon the planet. The light of the ring is also generally brighter than that of the planet; for the ring appears sufficiently bright when the telescope affords scarcely light enough for Saturn. The doctor concludes that the edge of the ring is not flat, but spherical or spheroidical. The dimensions of the ring, or of the two rings with the space between them, Dr. Herschel has given as follows : ་ Inner diameter of the smaller ring Outside diameter of ditto Inner diameter of the larger ring Outside diameter of ditto Breadth of the inner ring Breadth of the outer ring Breadth of the vacant space, or dark zone Miles. 146,345 184,393 190,248 204,883 20,000 7,200 2,839 The conjectures relative to the nature of this ring have been various. Some persons have imagined that the diameter of the planet Saturn was once equal to the present diameter of the outward ring, and that it was hollow; the present body being contained within the former surface, in some such a manner as a kernel is contained within its shell. They sup pose that, in consequence of some concussion, or other cause, the outer shell fell down to the inner body, and left only the ring at the greater distance from the centre. This conjecture is, in some measure, corroborated from the consideration that both the planet and its ring perform their rotations about the same common axis, and in very nearly the same time. Dr. Herschel, from the observations he made on the planet, concludes in the following words: 'It does not appear to me that there is sufficient ground for admitting the ring of Saturn to be of a very changeable nature, and I guess that its phenomena will hereafter be so fully explained as to reconcile all observations. In the mean time, we must withhold a final judgment of its construction, till we can have more observations. Its division into two very unequal parts can admit of no doubt.' The diameters of Saturn are not equal; they are, probably, in the proportion of about 11 to 10. This form, compared with that of Jupiter, leads one to conclude that Saturn turns rapidly round his shorter axis, and that the ring moves in the plane of his equator. Huygens observed five belts upon this planet nearly parallel to the equator. Besides the ring above mentioned, Saturn has seven satellites or moons continually circulating about him. The orbits of all these satellites, except the fifth, are nearly in the same plane, which makes an angle with the plane of Saturn's orbit of about 31°; and, by reason of their being inclined at such large angles, they cannot pass across their primary, or behind it, with respect to the earth, except when very near their nodes; so that eclipses of them happen much more seldom than of the satellites of Jupiter, Till the time of Herschel, five satellites only were known as connected with this planet: this astronomer, in the years 1787 and. 1788, discovered two others these are nearer to Saturn than any of the other five, but, to prevent confusion, they were de Ff nominated the 6th and 7th satellites. The fifth satellite has been observed to turn once round its axis exactly in the time in which it revolves round Saturn; and, in this respect, it resembles our Moon. The Naturalist's Diary. Sad wears the hour! heavy and drear GLOOMY as this month usually is, yet there are some intervals of clear and pleasant weather: the mornings are, occasionally, sharp, but the hoarfrost is soon dissipated by the Sun, and a fine open day follows. Of November scenery, on the other side of the Tweed, WALTER SCOTT has drawn a pleasing picture; much of it, however, applies equally to more southern regions. November's sky is chill and drear, No longer Autumn's glowing red |