ASTRONOMY WITH AN OPERA-GLASS. 



483 



terial of which this mountain is formed, would seem to possess a higher 

 reflective power than that of any other portion of the moon's surface. 

 One is irresistibly reminded of the crystallized mountains described in 

 the celebrated " Moon Hoax " of Richard Adams Locke. With an 

 opera-glass, you can readily recognize Aristarchus as a bright point at 

 full moon. With a field-glass it is better seen, and some of the short, 

 light rays surrounding it are perceived, while, when the sun is rising 

 upon it, about four days after first quarter, its crateriform shape can 

 be detected with such a glass. 



Fig. 2. Sunrise on the Sea op Serenity, and Theophiltjs and other Craters. 



The visibility of Aristarchus on the dark side of the moon leads us 

 to a brief consideration of the illumination by the earth of that por- 

 tion of the moon's surface which is not touched directly by sunlight at 

 new and old moon. This phenomenon is shown in our second illus- 

 tration. Not only can the outlines of the dark part of the moon be 

 seen under such circumstances, but even the distinction in color be- 

 tween the dusky " seas " and the more brilliant table-lands and mount- 

 ain-regions can be perceived, and with powerful telescopes many 

 minor features come into sight. A little consideration must convince 

 any one, as it convinced Galileo more than two hundred and seventy- 

 five years ago, that the light reflected from the earth upon the moon 

 is sufficient to produce this faint illumination of the lunar landscapes. 

 We have only to recall the splendors of a night that is lighted by a 

 full moon, and then to recollect that at new or old moon the earth 

 is "full" as seen from our satellite, and that a full earth must give 

 some fourteen times as much light as a full moon, in order to realize 

 the brilliancy of an earth-lit night upon the moon. As the moon 

 waxes to us, the earth wanes to the moon, and vice versa, and so the 



