PLATE XXV. 



CI.AVIUS, LONGOMONTANUS, TYCHO, ETC. PHOTOGRAPHED BY RITCHEY, NOVEMBER 2 1, 



I9OI, 7 HOURS 32 MINUTES P.M., CENTRAL STANDARD TIME. SCALE, 



THREE-FOURTHS METER TO MOON's DIAMETER. 



In this plate the large crater, only partly illuminated, on the line of the terminator and cut by 

 the upper edge of the plate, is Klaproth. Just below Klaproth is Blanchianus, which on its lower 

 margin nearly touches the' wall of Clavius, the largest structure in the field. Clavius is one hun- 

 dred and forty-two miles in diameter. North of Clavius, on the edge of the illumination, is 

 Longomontanus. Nearly in the center of the plate is Tycho, about which the great ray system, 

 visible under a very high sun, originates. This structure may be recognized by its central, sharp, 

 irregular cone. The large vulcanoid near the center of the lower part of the plate is Pitatus, 

 situated on the margin of the Mare Imbriura. It may be better identified by the " nil " on the 

 northeast part of its crater floor. 



The most noteworthy features of this plate are as follows : The abundance of relatively large 

 vulcanoids ; the difference in the nature of their floors, some being relatively smooth, others much 

 varied by pits and craters, and the association of small cones and craterlets of like horizontal sec- 

 tion, in all parts of the field where the light is favorable for their exhibition. 



The effect of the lava of the mare, when it comes in contact with the high ground, also 

 deserves attention. It appears to have more or less completely destroyed the walls of several 

 vulcanoids with which it came in contact. 



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