Let _S_ be the Sun, _ABCDEFGH_ Saturn’s Orbit, and _IKLMNO_ the Earth’s Orbit. Both Saturn and the Earth move according to the order of the letters, and when Saturn is at _A_ his ring is turned edgewise to the Sun _S_, and he is then seen from the Earth as if he had lost his ring, let the Earth be in any part of it’s Orbit whatever, except between _N_ and _O_; for whilst it describes that space, Saturn is apparently so near the Sun as to be hid in his beams. As Saturn goes from _A_ to _C_ his ring appears more and more open to the Earth: at _C_ the ring appears most open of all; and seems to grow narrower and narrower as Saturn goes from _C_ to _E_; and when he comes to _E_, the ring is again turned edgewise both to the Sun and Earth: and as neither of it’s sides are illuminated, it is invisible to us, because it’s edge is too thin to be perceptible: and Saturn appears again as if he had lost his ring. But as he goes from _E_ to _G_, his ring opens more and more to our view on the under side; and seems just as open at _G_ as it was at _C_; and may be seen in the night-time from the Earth in any part of it’s Orbit, except about _M_, when the Sun hides the Planet from our view. As Saturn goes from _G_ to _A_ his ring turns more and more edgewise to us, and therefore it seems to grow narrower and narrower; and at _A_ it disappears as before. Hence, while Saturn goes from _A_ to _E_ the Sun shines on the upper side of his ring, and the under side is dark; but whilst he goes from _E_ to _A_ the Sun shines on the under side of his ring, and the upper side is dark. [Sidenote: Fig. I and III.] It may perhaps be imagined that this Article might have been placed more properly after § 81 than here: but when the candid reader considers that all the various Phenomena of Saturn’s Ring depend upon a cause similar to that of our Earth’s seasons, he will readily allow that they are best explained together; and that the two Figures serve to illustrate each other. [Sidenote: PLATE VI. The Earth nearer the Sun in winter than in summer. Why the weather is coldest when the Earth is nearest the Sun.]