OBSERVATIONS OF LUNAR OBJECTS. 



65 



racter of the craterlets is no longer observed. Some put on a hazy appearance, 

 and they all assume the same aspect as those spots which have not been 

 observed as craterlets. This state of things continues until the declining 

 latitudes approach the limit at which the crater form was lost in the advan- 

 cing day, then it once more appears accompanied by a disappearance of most 

 of those spots which came into visibility as the sun rose higher. We have 

 an analogous phenomenon to this in the well-known crater Aristarchus. 

 Shortly after sunrise its outline is sharp and distinct, while its interior is 

 partly covered •with a well-marked shadow and partly glowing in strong 

 sunlight. As the sun rises above its horizon these characteristics are lost ; 

 the ridge extending from it to Herodotus becomes brighter, and to some eyes, 

 and with some instruments, it is confounded with the interior, the whole ap- 

 pearing as a very vivid brush of light. The exact solar altitude at which the 

 1871. r 



