ON MAPPING THE SURFACE OF THE MOON. 255 



59. A ridge between IV A**^ and the north end of IVA««58_ ^his 

 ridge is ou the line of cliffs between Ptolemaeus and the S.W. end 

 of the rill of Hyginus, 



60. A craterlet north by east of IV A« ^^. 3"-5, mag. 0-21. 



61. A ray from IVA**> extending in a N.E. direction as far as the 

 range of clifPs N.W. of Reaumur. Schmidt's riU, No. 365, N.W.- 

 S.E., discovered by him in 1853, May 14, with the Berlin refractor, 

 is near this ray. I do not find the riU on the photographs. 



62. A low ridge from IV A" ^ ^ to IV A* ^^, forming a depressed portion 

 of the Hne of cliife from Ptolemaeus to the S.W. end of the rill of 

 Hyginus. 



63. A mountain on IV A** ^^. Probably shown by Lohrmann. 



64. A curved mountain-range between IV A* ^^ and IV A* ^^. 



65. A curved mountain-range N.W. of IV A" ^^. 



66. A low ridge connecting IV A* ^^ with IV A* ^^. 



This low ridge is nearly parallel with the depressed portion between 

 IV A'* 16 and IVA'«58 of the line of cliffs from Ptolemaeus to the rill of 

 Hyginus. 



67. The S.W. border of Reaumur. 



68. A dark spot east of IV A** ^^, 



69. A dark spot north of Reaumur. 



70. A Hght spot north of IV A« 68. 



IY^a68^ IVA«69, and IV A« 'o form part of a Hne of cliffs north and 

 N.W. of Reaumur. It is shown by Lohrmaim. 



71. A bright spot between IV A/^ 16 (Horros) and IVA« 17. 



72. Part of the "Fault" IV A*? n, IV A^ 20. 



This interesting " Fault," which is of considerable extent, takes its rise in 

 the crater IV A" ^, the north border of which is cracked by it. The fault 

 has dislocated the S.E. end of the mountain-chain TV A" i^, and produced 

 the long narrow vaUey IV A" 1 1. About the middle of IV A" 1 1 it is inter- 

 sected by the faiilt IV A*' ^^, which taking its rise on the east border of Hind, 

 can be traced nearly as far as Godin. This fault, IV A" ^^, is coincident with 

 the " Ray from Tycho" which passes through or along the west border of 

 Albategnius, and also crosses the Mare Sereuitatis. It is on this Ray that 

 Bessel is situated. Just north of the point of intersection of the two faults 

 the ground rises, the crater IV A'^ i^ being included in the angle formed by 

 the intersection. If ear the point of intersection the fault IV A" 1 1 enters the 

 area IV A'^, in which it is designated as IV A'' ^^. On the extreme edges of 

 the chffs formed by IV A/^ 20^ the smaU craters IVA/^^i and IV A/3 1^ have 

 been opened. From IV A'^ 1 ^ the fault proceeds directly to the west border 

 of Rhceticus, having dislocated IV Ai^ ^^, the west portion of IV A"' '^^. The 

 west and north borders of Rhseticus have suffered very marked dislocations 

 by this fault. Its effects are 7iot visible on the smooth surface south of 

 Triesnecker, which — as well as the crater Uliert — has suffered by it, and 

 much disturbance occurs in the same line as far as the Apennines. 



An interesting question as to priority of epoch suggests itself in coniiexion 

 Avith these faults. The neighbourhood of IV A^ ^6 indicates that of the two 



