368 REPORT— 1866. 



Between IV A« 1 ' and the " ray from Tycho " is a dark strip interrupted by 

 the slope of IV A* ^^. This dark strip passes over the west of Ehscticus and 

 extends south from Ehreticus to IVA'^'". It is resumed in the depression 

 IV A" ''^ it crosses IV A" ^^, and part of the valley IV A* ^s, traverses the 

 ■western interior of IV A"'", crosses the middle of the valley IV A" •'^, the 

 south-west part of the depression IV A" '^, and is continued east of the bright 

 ray from Tycho into the area IV A^. 



The interior of lieanmur is dark in the full moon. The south-west part 

 is crossed by a strip somewhat lighter than the general surface ; the west and 

 north-west mountain border is also somewhat lighter. 



From the mountain IV A" ^ on the border of Reaumur the tint character- 

 izing the mountain border extends as far as the spot IV A* ^', and includes 

 the mountain IV A* ^8. The crater-row? IV A«^ IVA«22^ and IV A« 23, 



with the spot IV A* '", IV A^'^^j appear as a large bright spot, from which a 

 portion of a line of disturbance from Tycho appears as a ray which extends 

 to IV A^ '^^ This bright ray is skirted by a dark strip, which is very promi- 

 nent, in consequence of a light-ray parallel with that which extends from 

 jY^a7 ^Q lYA^^^. This parallel light-ray appears to take its rise from 

 IV A"*, and crosses IV A" 21, between IV A«'* and IV A" 2"; it is narrow, 

 but from IV A'' 2 ' it becomes broader and brighter as it traverses the surface 

 between IV A* 21 and IV A" ^^ : it is continued along the east side of the 

 mountain-arm IV A^ '*^ in area IV A^, 



IV A?. Full-Moon Aspect. 



This area is crossed from N'.N.W. to S.S.E. at the time of full moon 

 by a portion of a "ray from Tycho" sensibly parallel with the "fault" 

 IV A" 2^*, which is just cast of, and thus nearly coincident with, the next 

 westerly "ray from Tycho." Both rays traverse uneven ground of the 

 nature of cliffs, having their slopes towards the west. In passing over the 

 broken ground of IV A^ ^'^ the east ray is much broken, but it recovers its 

 brightness in traversing the uneven rocky interior of the north-east wall of 

 Albategnius. A lucid arm from the crater Hallcy traverses the south-west 

 slope of IV A^ 26 jjjjjj jjj(j ci-ater-rill IVA^^S in which IV A^^'' is conspi- 

 cuous as a bright spot ; it joins the " ray from Tycho " at the bright spot or 

 crater IV A^^'', which appears to be the most elevated point of the north- 

 east border of Albategnius. The crater IV A^*" appears as a bright spot 

 just east of the "ray from Tycho," while the group of craters IV A^ '^^, IV A.^^^, 

 IV A^'^*, IV A^'^", IV A^'", IVA^^°, IVA^'52 ^^ ^^^ north-west angle of 

 Albategnius presents a tint intermediate between the darker portions of the 

 siirface of this area and the bright rays. East of the " ray from Tycho" pass- 

 ing over IV A^, both the high land in the angle between Ptolemseus and 

 Albategnius, and the surface east of the cliff IV A^ ^^ on the floor of Hippar- 

 chus, present the darkest tint, as well as a strip which, from the west of 

 IV A^"*", extends to the west border of Ptolcmoeus. The east part of the 

 mountain-arm IV A^ ^'^ is bright in full moon. Between the dark spaces just 

 mentioned we have bright spaces intermingled -with middle tints ; a bright 



