484 THE POPULAR SCIENCE MONTHLY. 



phenomenon of earth-shine on the lunar surface must he looked for be- 

 fore the first quarter and after the last quarter of the moon. 



The reader will find it an attractive occupation to identify, by 

 means of the map, the various " seas," " lakes," and " marshes," for 

 not only are they interesting on account of the singularity of their 

 names, but they present many remarkable differences of appearance, 

 which may be perceived with the instrument he is supposed to hi 

 using. The oval form of the Crisian Sea (A), which is the first of the 

 " seas " to come into sight at new moon, makes it a very striking ob- 

 ject. With good telescopes, and under favorable illumination, a de- 

 cidedly green tint is perceived in the Crisian Sea. It measures about 

 two hundred and eighty by three hundred and fifty-five miles in ex- 

 tent, and is, perhaps, the deepest of all the old sea-beds visible on the 

 moon. It is surrounded by mountains, which can be readily seen 

 when the sun strikes athwart them a few days after new or full 

 moon. On the southwestern border a stupendous mountain-promon- 

 tory, called Cape Agarum, projects into the Crisian Sea fifty or sixty 

 miles, the highest part rising precipitously eleven thousand feet above 

 the floor of the sea. I have seen Cape Agarum very clearly defined 

 with a field-glass. Near the eastern border is the crater-mountain 

 Proclus, which I have already mentioned as possessing great brilliancy 

 under a high sun, being in this respect second only to Aristarchus. 



From the foot of Proclus spreads away the somewhat triangular 

 region called the Marsh of Sleep (F). The term "golden-brown," 

 which has been applied to it, perhaps describes its hue well enough. 

 With a telescope it is a most interesting region, but with less power- 

 ful instruments one must be content with recognizing its outline and 

 color. 



The broad, dark-gray expanse of the Sea of Tranquillity (G) will 

 be readily recognized by the observer, and he will be interested in the 

 mottled aspect which it presents in certain regions, caused by ridges 

 and elevations, which, when this sea-bottom was covered with water, 

 may have formed shoals and islands. 



The Sea of Fertility (X) is remarkable for its irregular surface, 

 and the long, crooked bays into which its southern extremity is di- 

 vided. 



The Sea of Nectar (V) is connected with the Sea of Tranquillity 

 by a broad strait (one would naturally anticipate from their names 

 that there must be some connection between them), while between it 

 and the Sea of Fertility runs the range of the Pyrenees Mountains, 

 twelve thousand feet high, flanked by many huge volcanic mountain- 

 rings. 



The Sea of Serenity (IT), lying northeast of the Sea of Tranquillity, 

 is about four hundred and twenty miles broad by four hundred and 

 thirty miles long, being very nearly of the same area as our Caspian 

 Sea. It is deeper than the Sea of Tranquillity, and a greenish hue is 



