ON MAPPING THE SURFACE OF THE MOON. 253 



36. A short mountain-rango nearly crossing IV A'* ^^, length of crest 

 12"*36. Not well shown by Lohrmann. 



This mountain -range Vies ijrecisely in the direction of a faint ray, IV A* ^^, 

 from IV A« 4. 



37. Two adjoining mountains on the west border of IV A* ^^. 



38. An elongated depression or valley in the north part of IV A* ^^ 

 (see IV A* '*2). Not in Lohrmann. 



39. A mountain on the west border of IV A* ^^. 



40. A mountain-range, its south end projecting into IV A* 2^. 



41. A lucid spot west of IV A^ *, probably the south slope of an emi- 

 nence on IV A* ^^. Not in Lohrmann. 



42. A line of fault extending north from IV A* ^ - which it crosses. It 

 is continued east of IV A* ^^ as far as the range IV A* *^, and re- 

 appears on the north side of IV A** ^^ in the ridge IV A* '*^. 



The surface immediately west of this fault is very greatly disturbed, ex- 

 hibiting a series of somewhat intricate formations, which are ill figured both 

 by B. & M. and Lohrmann. The most remarkable are IVA^^^, IV A* ^^j 

 and IV A* ^^. As these formations a^jpear to be intimately connected, it may 

 perhaps be better to describe them with the fault. IV A" ^^ is a consider- 

 able depression, a little east of the line joining Ehaeticus and Horrox. Its 

 west side, which is continued in a N.N.E. direction, as the west side of IV A* ^^ 

 is rather considerably elevated. It is on the " Ray from Tycho," and is 

 marked by the peaks IV A* ^^ at its south end, IV A'*37 (two) on its west 

 side, and IV A"* ^^ at its junction with IV A«* ^8^ ^nd also the cliff IV A« ^0. 

 An interior ledge on the west side is visible. The floor of IV A" ^^ is irregu- 

 lar and rough, the east interior slope being seen under a suitable illumination 

 rising from it. The most interesting feature of IV A** ^'^ is a ridge, IV A* ^^> 

 nearly but not quite crossing it from east to west. A faint ray, IV A" ^^' 

 extends between the east end of this ridge and the crater IV A* '^, and is 

 continued (IV A* ^ ^ ) in a shghtly altered direction on the opposite side of 

 IV A** *. The north part of the depression IV A* ^^ is connected with the 

 south, round the west extremity of IV A* ^^. South of IV A" ^^ jg ^be val- 

 ley IV A* ^2 ; the two, however, are not connected, although there is a par- 

 tial depression in the south wall of IV A* ^^, for IV A* '^ is much deeper 

 thanIVA«32. 



Eunning into IV A* ^^ on the north, is the depression IV A" ^^, closed at 

 its soiith end ; both the east and west sides are somewhat elevated, but the 

 north is entirely open, giving ingress to the narrow extremity of the moun- 

 tain-range IV A** ^^. All the depressions to the south of Rhteticus are very 

 unlike " craters," as a single glance at Horrox will sufficiently indicate. They 

 appear to fill the space between two ranges of mountains which diverge from 

 a point south-east of llhasticus. This space attains its greatest width in the 

 neighbourhood of the mountain-range IV A" ^^, which nearly crosses IV A* ^^, 

 and the two ranges imite at the south-west extremity of the valley IV A* ^'^• 

 The axis of the larger irregular and partially blocked valley, extending from 



