4. BRIGHT STREAKS. These radiate prominently from many of the great craters of the Moon. They are streaks of narrow width but sometimes nearly a hundred miles in length. They are perhaps the most puzzling of all the Moon's features. They have been supposed by some observers to represent lava flows whose surface reflected light more brilliantly than other portions of the Moon. It is more generally believed, however, that the streaks do not represent any independent elevations, since they run over the highest mountains as well as through the deepest craters without variation. GENERAL OBSERVATIONS. The condition of the Moon's surface as a whole indicates that it has been a theater of extraordinary volcanic activity. In size and number its vulcanoids far exceed the volcanoes of the Earth. The largest terrestrial crater known is that of Kilauea in the Hawaiian Islands which is 2½ miles in diameter. Several craters of the Moon, however, exceed 50 miles in diameter and one measures 114¼ miles. While the absolute heights of the mountains of the Moon do not greatly exceed those of the Earth, proportionally they are much higher, since the Moon's diameter is only one-fourth that of the Earth. The vulcanoids of the Moon differ in other respects from the volcanoes of our globe. "On the Earth they are usually openings on the summits or sides of mountains--on the Moon, depressions below the adjacent surface even when it is a plain or valley; on the Earth the mass of the cone usually far exceeds the capacity of the crater--on the Moon they are much nearer equality; on the Earth they are commonly the sources of long lava streams--on the Moon, traces of such outpourings are rare." (Webb.) DESCRIPTION OF INDIVIDUAL FEATURES. (Abridged from Nasmyth and Carpenter.) The numbers refer to those on the accompanying chart.