282 
GILBERT. 
a point near its southern end it is still narrower. Its maxi- 
mum depth is more than 10,000 feet. Its trend coincides 
with that of the Imbrian sculpture in its vicinity, and it thus 
helps to unite the furrow group of the western district with 
the great sculpture system. The flatness of its bottom is 
readily explained as a result of partial flooding, but its con¬ 
striction is less easily explained.* 
Wargentin .—One of the most striking anomalies of the 
moon’s face is the plateau Wargentin. It is a smooth, cir¬ 
cular table, 54 miles wide, standing several thousand feet 
above its base, and bearing a low parapet about the greater 
part of its edge. -It is readily recognized as a crater that 
has been filled by molten rock to the level of the lowest 
point of its lofty rim, and the determination of its mode of 
filling is a problem that has occupied the attention of all 
selenologists. A solution consonant with the moonlet theory 
is suggested by the Imbrian deluge. As already noted, the 
crater of Julius Csesar is filled as high as the breach through 
its southwestern rim. The filling, however, was not even, 
as the added material was not sufficient!y fluent to acquire a 
level surface. Five hundred miles away, in a district where 
the deluge was more liquid, the crater of Posidonius shows a 
level floor at the height of the lowest point of the rim. It 
happens that the walls of Posidonius are very uneven, and 
that their lowest pass is only a little higher than the neigh¬ 
boring Mare Serenitatis. Its floor therefore does not attract 
attention as an elevated plateau, but the relation of floor to 
rim is essentially the same as in Wargentin, and community 
of origin is a natural inference. Further study will be re¬ 
quired to determine the source of the Wargentin accession, 
but clues are not wanting, for the neighborhood abounds in 
evidence of flooding. Close to Wargentin’s western base lie 
three craters, of which the nearest, Phocylides b, is partly 
* While engaged in telescopic study I did not realize the importance of 
close attention to the details of this district, and these pages will go to 
press before I have opportunity for renewed observation. 
