THE MOON. 



It is found, on the other hand, that this boundary is everywhere rugged 

 and serrated, and brilliantly-illuminated points are seen in the dark parts of the 

 moon, at some distance from the general boundary of the illuminated part, while 

 dark shadows of considerable length appear to break into the illuminated sur- 

 face. In short, there is a continued irregularity throughout the whole extent 

 of the inner boundary of the lunar crescent. The inequalities thus apparent 

 indicate singular geographical and geological characteristics of the lunar sur- 

 face. Each of the bright points which are seen within the dark hemisphere 

 are the peaks of lofty mountains tinted with the sun's light. They are in the 

 condition with which all travellers on Alpine points are familiar ; after the sun 

 has set, and darkness has set in over the valleys at the foot of the chain, the 

 sun's light still continues to illuminate the lofty peaks above. The dark streaks 

 which break into the illuminated hemisphere of the moon are those of lofty 

 mountains within that hemisphere which project their shadows toward the 

 dark hemisphere. 



It appears, then, that the surface of the moon is a continuity of mountainous 

 regions. If we examine by means of a powerful telescope the full moon, we find 

 those features rendered larger and more conspicuous, and greatly multiplied in 

 number. What, it may be asked then, are those peculiar phenomena thus dis- 

 covered upon the full moon ? What is signified by the dark and what by the 

 lighter parts ? Elaborate telescopic research has shown us that the dark parts are 

 generally cavities into which the light of the sun penetrates imperfectly, while 

 the bright parts are eminences that catch the sun's light with great intensity. 

 Toward the sides of the full moon, also, the dark portions are caused by 

 the shadows of mountain peaks and ridges, which are more arid more 

 elongated the farther these points are removed from the centre of the full 

 moon. 



Within a recent period the moon has been subjected to extremely-elaborate 

 telescopic examinations by Beer and Madler, who have published some very 

 magnificent telescopic views of it. The telescopic map of the moon's surface, 

 published by these eminent observers, measures three feet in diameter, and may 

 truly be said to exceed in accuracy any chart of the globe of the earth. 



The lunar mountains are of various formations and arrangements : peaks 

 such as that of Teneriffe are common. Mountain ranges following straight 

 or nearly straight courses are also discoverable ; but the most frequent forma- 

 tion of the lunar mountains is that which resembles the crater of our volcano. 

 It is estimated that three fifths of the portion of the moon visible to us is cov- 

 ered with caverns penetrating to a great depth, and surrounded by a circular 

 wall of rock of a rugged and irregular character. These crater-formed cavities 

 are very various in diameter, varying from 50 or 60 miles to a few hundred feet, 

 and the number of them increases as the magnitude diminishes. The ridge 

 surrounding these craters is generally precipitous and nearly vertical on the 

 inside, but sloping more gradually on the outside. On descending to the bot- 

 tom, it is often found to arrange itself in steps or terraces. " The bottom of the 

 crater," says Professor Nichol, who has examined in detail the labors of Beer 

 and Madler, " is very often convex, and low ridges of mountains run through 

 it. We also find in it isolated conical peaks and smaller craters, whose heights, 

 however, seldom reach the level of the base of the exterior wall. These curi- 

 ous objects are on some parts of the moon so crowded that they seem to have 

 pressed on each other, and disturbed and even broken down each other's 

 boundaries, so that through the mutual interference the most oddly-shaped cav- 

 erns have arisen. It has often been observed that smaller craters are found on 

 the walls of the crater, and in many instances we can discern that the wall 

 has been shaken by force. 



