ON MAPPING THE SURFACE OF THE MOON. 263 



may probably be connected with the easternmost of the two " Eay-contres" 

 in the neighboui'hood of Furnerius. This System of liays appears almost to 

 rival that from Tycho in magnificence, but as it is nearer the Umb than 

 Tycho, the rays which issue from the centre are not so apparent. There is 

 also this peculiarity: a ray, which may be regarded as central, passes in a 

 nearly rectiliueal direction towards the central part of the visible hemisphere, 

 passing the north of Fracastorius and between Theophilus and CyriUus to 

 Alfraganus, and is lost apparently in the light ground that surrounds 

 Alfraganus ; but many of the irregularities of the smface, even as far as the 

 rocky land bordering the smoother surface on which Triesnecker is opened, 

 partake of the same direction, /. e. mountains and ridges in the neighbom-- 

 hood of Godin and Agri2)pa are directed towards this ray-centre, and even 

 the lateral valleys of the Apennines manifest the same general arrangement. 



The rays issuing from the ray-centre above-mentioned towards the north 

 and south bend so as to form branches of parabolic curves, and it is this 

 feature which constitutes the peculiarity before alluded to. 



The paraUeUsm of the vaUeys IV A*/ '^ lY A^ ^^, and III A^ 2 appears to 

 connect them with this system ; for although the general direction of these 

 valleys is not immediately towards the ray-centre, yet they appear to form 

 portions of the prolongations of rays that converge to it. 



iy^254 coincides with and is prolonged in a line of upheaval j»assing 

 through IV A^^ IV A^l (east side), IV A^^s^ IV A^49, ni A«2 (^est side), 

 and the east boundary of Eeaumur. See IV. S.S.W.-N.N.E., p. 272. 



*55. A craterlet on the floor of Ptolemeeus, between the mountains 



IV A^ 1', IV A^ 16 3"-33, mag. 0-19. Well shown by Lohrmann. 

 *o6. A mountain on the S.E. side of IV A^ 2^, length SSW-NNE 

 9"-79. 



57. A mountain near the N.E. extremity of IVA^^^ leno-fh S S W- 

 N-.N.E. 5"-23. ■ ' ■ 



These mountains, with the N.E. spur of IVA^^D^ ^^^^ ^^^ ^-^ boundary 

 of the valley IV A^-'' ; it is uncertain if the mountains be isolated or con- 

 nected by low ridges, but it appears probable that the surfaces of the valley 

 IV A^27 and the depression IVA^^S ^^,^ ^^ ^j^^ ^^^^ j^^^^^ ^^^ ^^^^ ^^^^_ 



ther they form the lowest portion of Hipparchus, the levels of Ptolem^us 

 and Albategnius being considerably lower. 



*58. A curved mountain-chain on the floor of Hipparchus, west of the 



chff IV A^ ^^. It is concentric with the S.W. border of Hipparchus 



Diameter N.W. to S.E. 20"-45. 



There is great reason to believe that this formation is an ancient and partly 



fined crater with a very broken Avail, as under an oblique illumination its 



surface is seen to be depressed, and it presents the crater character. The 



craterlet IV A? l"" appears to form a point in the line of ancient wall. 



59. A craterlet at the S.W. extremity of the mountain-arm enclosing 

 the plain IV A^ ^4^ jjj ^? 14 ^^ ^^^ gQ^|.}^_ Diameter east to west 

 4"-76,_ north to south 2"85, mag. 0-23. It requires further ob- 

 servation. 



*60, The mountain-range between IV A^ ^^ and III A^ ^ jgngth S.S W - 

 N.N.E. 13"-31. 



*61. A mountain north of IV A? '^ 8"-08. Lohrmann 34, Sec. I. 



IV A^ 3' and IV A^^^ are two conspicuous mountains, with the valley 



