PLATE YII. 



Copernicus and Kepler. I'liotograplied }>y Bitchey with the 40-in<'h Yerkes refractor, with 

 color screen and imchromatic plate. 



The most important features exliibited here are the systems of bright rays of 

 Copernicus, Kepler, and Aristarclius. These three ray systems, though less exten- 

 sive than those of Tyrho, taken together constitute the greatest exhibition of the 

 bright bands that exist over the northern part of tlie surface. The complex branched 

 nature of these bands is particularly well shown — better, indeed, than the writer has 

 ever been able to note with the telescojae. The fact that the bright bands of each 

 system are prolongations of a central bright field is tolerably well shown. 



Although owing to the high sun and the consequent absence of shadows, Coper- 

 nicus in this view hardly appears as an elevation, it is, under favorable conditions of 

 illumination, perhaps the noblest object on the moon. The wall on the eastern side, 

 according to the estimates of Schmidt, rises to a height of 12,000 feet above the 

 adjacent plain. The outer slopes of the cone are strongly ridged as by the flow 

 from the crater of lavas which cooled on the steep slopes; some of these are faintly 

 traceable in the plate. 



