PLATE V. 



MOON'S AGE IO DAYS, 12 HOURS. LICK OBSERVATORY, l8gO. 



The moon as delineated in this plate is thirty-eight hours older than as shown in the preceding 

 plate. The most noteworthy changes are the great advance in the development of the fields of 

 very bright hue, and in the bands radiating from them. These are most evident in the system of 

 Copernicus. The system of Tycho also begins to be evident. This vulcanoid may be identified 

 as the deep large crater with a central cone near the border of the illuminated area. The general 

 irregularity of these light bands is well shown in those about Copernicus. So, too, the fact that 

 they are projections from an illuminated or lucent field about the vulcanoid. 



On the shores of the Oceanus Procellarum, east of Plato, near the margin of the sun-lit area, 

 is the Sinus Iridum. This is probably a large vulcanoid which has had the part of its wall next 

 the mare melted down by the lava of that field. (See p. 17.) 



The relative absence of large vulcanoids on the maria is noteworthy. Those which exist lie 

 nearly, if not altogether, on fields of high ground which appear to have risen above the floors of 

 the maria and so escaped melting. 



The problematical crater Linn now appears as a small white patch near the middle of the 

 eastern side of the M. Serenitatis. (See p. 70.) 



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