204 The Lunar Aristillus and Autohjcus. 



rows of hills; and on the S., where the ridges are boldest, 

 and fill all the space as far as Autolycus, they are entirely 

 wanting. This entire independence of hill-radiation and 

 light- divergence is a singular, but general characteristic of 

 the moon. 



A short distance S. of Aristillus, we find another grand 

 crater, Autohjcus (22), similar, but somewhat inferior to its 

 neighbour in almost every respect. Its breadth is twenty- 

 three miles ; its depth beneath the E. wall 9000f., the height 

 of the W. wall 8400f. above the cavity, 4800f. above the 

 exterior base. The latter measures are given at 8800f. and 

 OOOOf. by Schr., who observes that the great Canigou, the 

 chief of the E. Pyrenees, would stand in its interior. The 

 larger ratio of its depth, and the small dimensions of its 

 central hill show some modification of eruptive force as com- 

 pared with Aristillus, but it is surrounded in the same way, 

 though not to so great an extent, by radiating streams of 

 blocks or lava. Where these two systems approach and mingle 

 with each other in the space between the craters, might 

 it not be possible for some of the most powerful telescopes of 

 the day to detect evidence of unequal date ? The light streaks 

 which Schmidt ascribes to Autohjcus, though in a less degree 

 than to its neighbour, were neither drawn nor described by 

 his predecessors, and this is so far worthy of notice, that the 

 permanency of these uncomprehended markings has hitherto 

 been assumed rather than proved. The streaks of Aristillus, 

 he says, are best viewed in the wane. Schr. has remarked that 

 the interiors of these two craters, like those of Cl'eomedes, Endy- 

 mion, Schickha.rd, and others, grow darker under a higher angle 

 of illumination. I have seen in the decreasing moon, when 

 the terminator lay a little less than its own diameter beyond 

 Posidonius, a remarkable ledge on the interior slope of the 

 wall of Autohjcus, marked through more than a quadrant by a 

 separate shadow. 



A singular remark of B. and M. in this place must not be 

 omitted, to the effect, that such combinations of two (or even 

 more) craters are frequently met with, lying under the same 

 meridian, in which the steepness and formation of the wall 

 within and without, the relative height and reflectiveness, in 

 short, the whole character, are nearly the same, and" both are 

 equally conspicuous. If they differ in size, the smaller lies S., 

 and in that case their diameters are in the ratio of three to 

 four; they are about 18 to 36 miles apart; and connected by 

 several more or less marked ridges running from the N. to the 

 S. crater in a S.W. direction. Examples, Aristillus and Auto- 

 lycus ; Pctavius and Furnerius ; Agrippa and Godin ; Aris- 

 toteles and Eudoxus ; Ptoleniaeus, Alphonsus and Arzachel ; 



