PLATE IV. 



Moon^s age, 23 days 7 hours. July 28, 1891. Lick Observatory. 



At this stage of the waning moon the most interesting of its fields are no longer 

 visible. There are few that command attention in this plate. It may be noted that 

 the system of light bands and the central patches whence they proceed, that have 

 their center in Kepler, are still very bright. The dark mare-like floor of (jrrimaldi 

 is visible near the bright margin of the sphere. The observer may obtain something 

 of the impression, such as is afforded by good seeing with a powerful telescope, that 

 the Oceanus Procellarum is a relatively shallow sea by the number of fragments of 

 what seems to have been the more ancient surface that protrude through it. 



