d. h. m. s. Mercury 0.85 4.72 0.43 6.91 6.67 88 (?) 0.14 Venus 0.89 4.94 0.82 13.19 1.91 23 21 23 (?) 0.76 Earth 1.00 5.55 1.00 16.08 1.00 23 56 4 0.50 (?) Mars 0.71 3.92 0.38 6.11 0.43 24 37 23 0.22 h. m. Jupiter 0.24 1.32 2.65 42.61 0.037 9 55 ± 0.62 Saturn 0.13 0.72 1.18 18.97 0.011 10 14 ± 0.72 Uranus 0.22 1.22 0.90 14.47 0.003 9 30 (?) 0.60 Neptune 0.20 1.11 0.89 14.31 0.001 (?) 0.52 {59} Danish astronomer, "Tycho," and is one of the most conspicuous objects of the full Moon. The contrasts of the Moon are much more pronounced when she is only partly lit up. Then the mountains and valleys stand out in the strongest relief, and it becomes clear that the general type of formation on the Moon is that of rings--rings of every conceivable size, from the smallest point that the telescope can detect up to some of the great dusky plains themselves, hundreds of miles in diameter. These rings are so numerous that Galileo described the Moon as looking as full of "eyes" as a peacock's tail. The "right eye" of the moonface, as we see it in the sky, is formed by a vast dusky plain, nearly as large as France and Germany put together, to which has been given the name of the "Sea of Rains" (_Mare Imbrium_), and just below this (as seen in the telescope) is one of the most perfect and beautiful of all the lunar rings--a great ring-plain, 56 miles in diameter, called after the thinker who revolutionised men's ideas of the solar system, "Copernicus." "Copernicus," like "Tycho," is the centre of a set of bright streaks; and a neighbouring but smaller ring, bearing the great name of "Kepler," stands in a like relation to another set. The most elevated region of the Moon is immediately in the neighbourhood of the great "stalk of the orange," "Tycho." Here the rings are crowded together as closely as they can be packed; more closely in many places, for they intrude upon and overlap each other in the most intricate manner. A long chain of fine rings stretches from this disturbed region nearly to the centre of the disc, where the great Alexandrian astronomer is commemorated by a vast walled plain, {60} considerably larger than the whole of Wales, and known as "Ptolemæus."