ON MAPPING THE SURFACE OF THE MOON, 35 
*69. A shallow depression E. of TV Af 7, probably 58 of Lohrmann’s 
Sec. I. 
Lohrmann appears not to have made the distinction between this depres- 
sion and the plain that extends eastward from it, as far as the mountains 
TV Af, TV Af %, and IV AS35, but has given between IV Af” and these 
mountains a smooth plain, The depression IV A®® is well marked in 
Rutherford’s photogram. 
*70, A mountain-range in the chain that extends from the junction of 
Ptolemeus and Alphonsus to and beyond IV Af*!, This range “forks” 
into two small branches at the 8. end. Length of crest from N. end to fork 
6°71, from fork to 8.E. end 4:01, from fork to S.W. end 7’"18. 
71. The depression enclosed by IV A®19, TV Af, TV A835, TV AP 36, 
TY Af 18, TV AP 38, and TV A8?!, It is not shown by Lohrmann as a de- 
pression. 
This depression is situated in so very interesting a group of objects, the 
S. part of which occurs in area LV A", that, anticipating to some extent a 
notice of the objects in that area, it may be well to describe the group 
in this place. 
This group consists of IV A’®, TV A", IV A"8, IV A"2l, the partly 
enclosed surface IV A”*’, with the valley IVA", and the mountains 
Ty A”, TV A”, TV A" 33, and IV A"*4, Were these objects in a level 
portion of the moon, IV A” *? would present the aspect of a depression partly 
surrounded by mountains. As it is, it has greatly the appearance of one of 
those partially destroyed craters which are met with on the borders of the 
Maria ; and it is not a little remarkable that the mountainous boundary ends 
abruptly both on the 8.H, and N.W. at the line of cliffs in the chain from 
the junction of Ptolemeus and Alphonsus to and beyond IV A®*!, the por- 
tion §.E, of the valley IV A”!! facing the depressed surface of Hipparchus. 
There is not the slightest indication of a complete boundary haying existed 
at any anterior epoch similar to ITV A¢*® (see letterpress, areas IV A*, IV AS, 
p- 27, and Report Brit. Assoc. 1866, p. 263); indeed the mountains are 
scarcely disposed in the segment of a ring. The object which presents 
the nearest analogy to IV A" is [V A*10; and it is noteworthy that the 
southern mountainous boundaries of both are curved, the convexities being 
towards the 8.; and both are traversed by valleys running in the same 
direction. IV A”*, as itis seen on Rutherford’s photogram, and also on the 
moon, is very individualized ; it forms, however, only part of a larger forma- 
tion, which is not the less well and distinctly marked. Among the remaining 
objects are LV Af“, TV AS, and TV Af3%, three mountains in a line with 
Ty A’, TV A” 18, and IV A"?!, but separated from them by the plateau or 
slope [V A®*. Together these mountains form the W. wall of the larger 
formation, the N. boundary of which consists of the low N.N.W. wall of the 
depression IV Af 18, and the N.E. foot of the mountain IV Af 47; the E.S.E. 
boundary consists of the cliffs bordering Hipparchus on the W:N.W., of 
which the highest point is IV Af 38, 
The striking peculiarities of this formation are the depression IV A” 2 at 
its $8. end, and the elevated boss filling IV A*15 at its N. end; so that there 
is a gradual slope from N. to 8. Two craters are opened upon it, IV Aé 19 
and [VY A**!, TV Af?! is peculiarly situated, as if the northern mass had 
been heaved forwards towards the S.E. The faults TV A" TV Af 2 Ty At7 
and [IV A"*8 TY AF ® include a great portion of this formation, which is 
traversed by the “ray from Tycho” on which Bessel is situated. This 
“ray” passes close to IV Af 19, which is situated on its E.N.E. slope, 
