Place of his Nodes.
77. Jupiter’s Orbit is 1 degree 20 minutes inclined to the Ecliptic. His North Node is in the 7th degree of Cancer, and his South Node in the 7th degree of Capricorn.
Saturn.
Fig. I.
78. Saturn, the remotest of all the Planets, is about 777 millions of miles from the Sun; and, travelling at the rate of 18 thousand miles every hour, as in the circle marked ♄, performs his annual circuit in 29 years 167 days and 5 hours of our time; which makes only one year to that Planet. His diameter is 67,000 miles; and therefore he is near 600 times as big as the Earth.
Fig. V.
His Ring.
[PLATE I].
79. He is surrounded by a thin broad Ring, as an artificial Globe is by its Horizon. This Ring appears double when seen through a good telescope, and is represented by the figure in such an oblique view as it is generally seen. It is inclined 30 degrees to the Ecliptic, and is about 21 thousand miles in breadth; which is equal to it’s distance from Saturn on all sides. There is reason to believe that the Ring turns round it’s Axis, because, when it is almost edge-wise to us, it appears somewhat thicker on one side of the Planet than on the other; and the thickest edge has been seen on different sides at different times. But Saturn having no visible spots on his body, whereby to determine the time of his turning round his Axis, the length of his days and nights, and the position of his Axis, are unknown to us.
His five Moons.
Fig. I.
80. To Saturn, the Sun appears only 1⁄90th part so big as to us; and the light and heat he receives from the Sun are in the same proportion to ours. But to compensate for the small quantity of sun-light, he has five Moons, all going round him on the outside of his Ring, and nearly in the same plane with it. The first, or nearest Moon to Saturn, goes round him in 1 day 21 hours 19 minutes; and is 140 thousand miles from his center: The second, in two days 17 hours 40 minutes; at the distance of 187 thousand miles: The third, in 4 days 12 hours 25 minutes; at 263 thousand miles distance: The fourth, in 15 days 22 hours 41 minutes; at the distance of 600 thousand miles: And the fifth, or outermost, at one million 800 thousand miles from Saturn’s center, goes round him in 79 days 7 hours 48 minutes. Their Orbits in the Scheme of the Solar System are represented by the five small circles, marked 1. 2. 3. 4. 5. on Saturn’s Orbit; but these, like the Orbits of the other Satellites, are drawn fifty times too large in proportion to the Orbits of their Primary Planets.
His Axis probably inclined to his Ring.
81. The Sun shines almost fifteen of our years together on one side of Saturn’s Ring without setting, and as long on the other in it’s turn. So that the Ring is visible to the inhabitants of that Planet for almost fifteen of our years, and as long invisible by turns, if it’s Axis has no Inclination to it’s Ring: but if the Axis of the Planet be inclined to the Ring, suppose about 30 degrees, the Ring will appear and disappear once every natural day to all the inhabitants within 30 degrees of the Equator, on both sides, frequently eclipsing the Sun in a Saturnian day. Moreover, if Saturn’s Axis be so inclined to his Ring, it is perpendicular to his Orbit; and thereby the inconvenience of different seasons to that Planet is avoided. For considering the length of Saturn’s year, which is almost equal to thirty of ours, what a dreadful condition must the inhabitants of his Polar regions be in, if they be half of that time deprived of the light and heat of the Sun? which must not be their case alone, if the Axis of the Planet be perpendicular to the Ring, but also the Ring must hide the Sun from vast tracks of land on each side of the Equator for 13 or 14 of our years together, on the south side and north side by turns, as the Axis inclines to or from the Sun: the reverse of which inconvenience is another good presumptive proof of the Inclination of Saturn’s Axis to it’s Ring, and also of his Axis being perpendicular to his Orbit.