_Craters, Craterlets, and Crater-Pits._ Usually circular in form, and severally offering distinctions as to dimensions and shape. The craters are surrounded by walls, rising abruptly to tolerable heights, and pretty regular in their contour. When the Sun is rising the shadow of the walls falls upon the interior of the craters, and many of these dark conspicuous objects are to be seen near the Moon’s terminator. With a high Sun some of the craters are extremely bright. In proof of the large number of these objects, it may be noted here that in Mädler’s lunar map (1837) 7735 craters are figured, while in Schmidt’s (1878) there are no less than 32,856! _Crater-Cones._ Conical hills or mountains, visible as small luminous spots about the period of full Moon. They are from 1/2 to 3 miles in diameter, and show deep central depressions. It is somewhat difficult to distinguish them from the ordinary mountain-peaks and white spots, and they are not unlike the cones of terrestrial volcanoes. _Rills or Clefts._ These are very curious objects. They were first discovered by Schröter in 1787, and some of them are to be traced over a considerable extent of the lunar surface, their entire length being 200 or 300 miles. They have the appearance of cuttings or canals, and are sometimes straight, sometimes bent, and not unfrequently develop branches which intersect each other. They apparently run without interruption through many varieties of lunar objects. The bottoms of these rills are nearly flat, and look not unlike dried riverbeds. Some observers have regarded them as fractures or cracks in the Moon’s surface; but their appearance and circumstances of arrangement are opposed to such a view. Our present knowledge includes more than 1000 of these rills. _Mountain-Ranges_ are chains of lofty peaks and highlands, sometimes divided by rills and numerous ravines and cross valleys. Some of these ranges are of vast magnitude, and the summits of the mountains reach altitudes between 15,000 and 20,000 feet, and sometimes even more. _Mountain-Ridges_ are to be found scattered in the greatest abundance in the most disturbed localities of the lunar surface. They sometimes connect several formations, or surmount ravines or depressions of large extent. Peaks attaining altitudes of more than 5000 feet rise from them, and they range in several cases over 100 miles. _Ray-Centres._ Systems of radiating light-streaks, having a mountain-ring as the centre of divergence, and stretching to distances of some hundreds of miles round. Tycho, Copernicus, Kepler, Anaxagoras, Aristarchus, and Olbers are pronounced examples of this class.