380 REPORT—1868, 
The desideratum connected with spots of this nature is not so much the detec- 
tion of physical change as the ewvact determination of the value or extent of 
apparent change dependent upon variations of distance, libration, and angle of 
illumination; for until such determinations are reduced to numerical values, we 
are not in a position to decide upon the absolute fiaity of such objects ; nor can 
we be certain that there is more than apparent change until a large number of 
observations are discussed with especial reference to the elements above named. 
The Rey. T. W. Webb, in contrasting his seeings of Hratosthenes with the 
description of that crater by Beer and Miidler in ‘ Der Mond,’ has the following 
very important remarks. Speaking of the appearance which Hratosthenes pre- 
sented on the evening of Noy. 8, 1867, he says, “ Hratosthenes now all in local 
colour; from point of junction of Apennines round the E. semicircle, the out- 
side glacis of wall shows a curious dark-grey border, This is penetrated in two 
places by the streaks of Copernicus, which extend perhaps across Hratosthenes 
itself. Curious as to chronological sequence . . . It is just possible, however,” 
Mr. Webb continues, “that some process affecting the reflective power of the 
surface may at this time be working here; for B. & M. say that this crater is 
‘in full moon not very distinct’*: we only see a very undefined faint light 
spot in a vicinity almost equally luminous. No mention is made of any 
darker portions, or of their being so situated as to indicate the position of the 
ring; and the description certainly does not tally well with present appearances. 
This is a peculiarly suitable spot for examining the question whether the Full- 
moon markings are unchangeable. Fixity, of course, if established by a long 
course of observation here, or anywhere else, would be no argument for its 
universal prevalence, since a state of quiescence in this respect might be attained 
at’very different epochs in different regions; but should the reverse be clearly 
ascertained in a single well-marked, even though minute, case, it need not be 
mentioned that one distinct, incontrovertible affirmation weighs down any 
number of negative instances, and merely throws back the date of their change 
to a prehistoric period.’’—Intellectual Observer, vol. xii. pp. 435, 436. 
**38(x). A mountain-peak on the W. border of Hipparchus, the culmi- 
nating point of the mountain-mass in IV Af 15, 
The high mountain-border on which IV Af *8 is situated, extends from the 
mouth of the valley IV A” *!, in the depression IV A” *, to the N. part of the 
peak IV A? 47 (see ante, p. 22). 
*39(x). A mountain-arm lying in the shallow depression TV A* 41, which 
it scarcely fills. Its direction is N.E.-S.W.; it springs from the 8. end of 
the depression IV A 4°, between IV A*4 and IV Af ?°; its highest point is 
the N.E., from which it gradually declines in altitude to the 8.W. part of 
the depression IV A*4!, Length of crest 8'"95, breadth of base 6-25 (see 
ante, pp. 15, 16). 
40(x). A depression having somewhat of the crater character, between 
Ty Af4 and IV Af 1°, which rise to a considerable elevation on the W.N.W. 
and E.8.E. It is closed on the N. by lower hills, and on the 8. by the N.E. 
extremity of the mountain-arm IV A? 9, 
41. The shallow depression in which IY A* *9 is situated. 
42. A “fault” passing through IV A® ®, the K. foot of IV Af 74, grazing the 
E. foot of TV Af 73, along the axis of TY A*!°, and the W. mountain-border 
of IV AF 49, 
* Tt is necessary to bear in mind that Mr, Webb’s aperture is much larger than the one 
with which B. & M. observed ; it would nevertheless be important for gentlemen possessed 
of smaller apertures to examine Hratosthenes with the view of making out the details — 
recorded by Mr. Webb. 
