PLATE YIII. 



Ray system about Tycho. Photographed by Ritchey. 



This, the most extensive of the ray systems of the moon, has its origin in the field 

 about Tyclio, the large vulcanoid to which the numerous bands apparently converge. 

 It appears under the high sun as a large pit with a compound central cone. The 

 rays of this system should be compared with those which have their centers in 

 Copernicus and Kepler. In these last-named groups the streaks are developed on 

 relatively level ground, while on that of Tycho they intersect a rugged surface. 



On the right hand, some of the bands may be seen crossing the Mare Nubium. 

 Two of them, of great length, are seen to be nearly parallel for a distance of some 

 hundred miles. 



A number of large vulcanoids, partly in shadow, are shown on the southeast 

 margin of the moon. Of these, the largest is Schiller. Its length, which is 112 miles, 

 will serve as a scale in estimating that of the rays. 



