486 THE POPULAR SCIENCE MONTHLY. 



trasted with the dusky semicircle at their feet, and have been able to 

 detect the presence of the low ridges that cross the front of the bay 

 like shoals, separating it from the " sea " outside. Two or three days 

 after first quarter, the shadows of the peaks about the Bay of Rain- 

 bows may be seen. The Bay of Dew (R) above the Bay of Rain- 

 bows, and the Sea of Cold (C), are the northernmost of the dark levels 

 visible. It was in keeping with the supposed character of this region 

 of the moon that Riccioli named two portions of it the Land of Hoar 

 Frost and the Land of Drought. 



Extending along the eastern side of the disk is the great Ocean of 

 Storms (Q), while between the Ocean of Storms and the middle of the 

 moon lies the Sea of Clouds (S). Both of these are very irregular in 

 outline, and much broken by ridges and mountains. The Sea of Hu- 

 mors (T), although comparatively small, is one of the most easily seen 

 of all the lunar plains. To the naked eye it looks like a dark, oval 

 patch on the moon. With a telescope it is seen, under favorable con- 

 ditions, to possess a decided green tint. Humboldt Sea (B) and the 

 South Sea (Z) belong principally to that part of the moon which is 

 always turned away from the earth, and only their edges project into 

 the visible hemisphere, although under favorable librations, their fur- 

 ther borders, lined as usual with mountain-peaks, may be detected. 

 For our purposes they possess little interest. 



Let us now glance at some of the mountains and " craters." The 

 dark oval called Grimaldi (1) can be detected by the naked eye, or at 

 least it has been thus seen, although it requires a sharp eye ; and per- 

 haps a shade of London smoke-glass, to take off the glare of the moon, 

 should be used in looking for it. It is simply a plain, containing some 

 fourteen thousand square miles, remarkable for its dark color, and sur- 

 rounded by mountains. Schickhard (7) is another similar plain, nearly 

 as large, but not possessing the same dark tint in the interior. The 

 huge mountains around Schickhard make a fine spectacle when the sun 

 is rising upon them shortly before full moon. 



Tycho (9) is the most famous of the crater-mountains, though not 

 the largest. It is about fifty-four miles across and three miles deep, 

 In its center is a peak five or six thousand feet high. Tycho is the 

 radial point of the great light-streaks that, as I have already re- 

 marked, cause the southern half of the moon to be likened to a peeled 

 orange. It is a tough problem in selenography to account for these 

 streaks. They are best seen at full moon. They can not be seen at 

 all until the sun has risen to a certain elevation above them, 25 ac- 

 cording to Neison ; but, when they once become visible, they dominate 

 everything. They turn aside for neither mountains nor plains, but 

 pass straight on their courses over the ruggedest regions of the moon, 

 retaining their brilliancy undiminished, and pouring back such a flood 

 of reflected light that they completely conceal some of the most stu- 

 pendous mountain-masses across which they lie. They clearly consist 



