PLATE I. 



Age of moon, S dai/s 4 ho)ir.'<. September 2£, 1890. Lick Observatory. 



[In accordance with the usage of selenographers, the plates are printed in the 

 reversed order in which they appear in a celestial telescope. The top of each is the 

 south, the bottom the north, the right-hand the east, and the left the west.] 



In n. I the most noteworthy features are the maria of the western half of the 

 visible portion of the si)here. Tlie rudely circular form of these fields is well shown, 

 also tlie fact tliat none of them extend to the margin or "liml)" of the moon. The 

 bright, slightly curved ridge in the lower half of the picture facing the partly illu- 

 minated mare — the Mare Imbrium — is the Apennines; the large vulcanoid at its 

 southern end is Eratosthenes. The larger pit in the ocean opposite the center of the 

 range is Archimedes; the two craters next to the north are, the nearer, Autolycus, 

 and the farther and larger, Aristillus. The larger of the two dark pits near the 

 northern end of the Apennines is Eudoxus, the smaller, Aristoteles. Southeast from 

 these iTaters lie the Alps, a group of bright peaks extending in a northeast and south- 

 west direction. A faint, dark streak shows the position of the Alpine Valley. The 

 flat, irregular area north of the range is the M. Frigoris. 



Close insi)ection of this plate will show that many of the vulcanoids" have pits or 

 cones on their floors, and that these are very often in the center of these level spaces. 



The radiating bands or streaks are beginning to appear. 



In the Mare Indjrium, near the western end of the Alps, next north of Aristillus, 

 is Cassini, of which the encircling cone appears to have been partly melted down by 

 the lava of the mare so that it shows as a faint ridge with a distinct central crater. 



flin this memoir all the features of the moon commonly termed "volcanoes" etc., 

 are designated by tlie generic term "vulcanoid." 



