98 The Lunar Clefts — Mare Vaporum. 



was applied by Mm to the whole dark hill- country N. of the 

 small crater now so called : and his first cleft commences there 

 as a flat valley : he did not notice any of the minuter craters 

 in its course, but places upon it, as interrupting it, the Hyginus 

 of B. and M., of which he remarks, in a subsequent observation 

 with the 27 f. reflector, that it has certainly no ring : at the 

 same time he found that the W. end of the cleft, which he had 

 previously carried right up to the wall of Agripjpa, is lost about 

 one diameter of that crater 1ST. of it. The second cleft he 

 brings, not out of B. and M/s small crater, which he does not 

 notice, but from a point further E., the end of his Hyginus ; 

 and originally drew it as dividing a flat bright crater (his D), 

 about half as large as Agrvppa, which has on its S.W. side a 

 smaller crater, q, and another flat, crater-like depression v, 

 between q and the cleft. Of these objects q is the Silberschlag 

 of B. and M., but D and v cannot be identified in their Map ; 

 the ridges, however, about their a, N.E. of Silberschlag , and 

 those N. of that crater, in some states of illumination assume 

 a ring-like aspect : a source of deception well known to lunar 

 observers. Schr. also shows the crater which B. and M. place 

 on the N. bank of the cleft ; but in two separate designs he 

 has made the cleft pass further S., about equidistant between 

 this lesser crater and Silberschlag . From all this it will be 

 seen how difficult it is to reconcile representations by different 

 hands, or even to account for their discrepancy. Further W. 

 Schr. places two mountains in the course of the cleft ; the first 

 of these, a, seems to be the a of B. and M. ; the second, p, 

 is their /3. What struck him greatly was, that he saw, 1794, 

 Mar. 8, with a 7 f . Newtonian, the ring of his D on both 

 sides, and the mountains a and /jl, all split by the cleft : Sept. 1, 

 with his 27 f. reflector he found the ring of D and the moun- 

 tain /ub undivided (agreeing in this last with B. and M.). 1796, 

 Feb. 15, /j, was divided, with a four-inch Dollond : Mar. 15, 

 with his 13 f. reflector, D had its ring incomplete and open on 

 the N.E., where the cleft enters it ; but the other side of the 

 ring' (namely, the very narrow gorge at a, B. and M.) was 

 undivided, as well as the mountains a and /i : 1798, July 19, he 

 and Olb ers, with the 13 f., both saw /u, undivided, and the 

 latter noticed the slight bend in the cleft shown by B and M. 

 a little W. of this spot. Schr. also found at the S. end of the 

 chain of which /u, is the centi'al portion, a mountain which he 

 had never seen before, though the highest of all, casting a 

 long spire of shadow while the rest had none, and measuring 

 3200 f. From this he was induced to infer former atmospheric 

 obscuration ; and he could not resist a very cautious sugges- 

 tion, that the singular alternately open and closed aspect of 

 the mountains above the cleft might point to some artificial 



