74 
The spot in question is marked IV A a 17, IV A? 39 on the 
areas of the British Association Lunar Map IV A a and IV A?, 
and is situated in 2° W. long., and 5° S. lat. It is also 
situated on the S.W. side of the ridge forming the N.E. 
boundary of Hipparchus, and has been described as “ a bright 
spot S.S.W. of IV Aa 7 (Beer and Madler’s Hipparchus F). 
Its diameter is 5 //, 94! and magnitude 0 o- 37, the diameter of 
Dionysius being regarded as unity. On De La Rue’s photo- 
graph 1858, February 22, it appears as a spot of about 4° of 
brightness. It is not so bright as Linne, which is about 5°, 
In this photograph it is seen to stand upon the east edge of 
a large depression running nearly S. by W. — N. by E. This 
edge, which forms a low ridge, connects the mountainous 
boundary of Hipparchus with the mountain IV A£ 37. 
IV Aa 7, a bright spot smaller than IV Aa 17, IV A£ 39, 
stands upon the west edge of this depression, which also 
meets the mountain IV A£ 37. 
On Rutherford’s photograph 1865, March 6, this spot 
appears brighter than in De La Rue’s, viz. 5°. Linne in 
this photograph is 6°. The observations that have been 
made of this spot are as under, 
Year. 
Date. 
Authority. 
Character. 
Bright- 
ness. 
1858 
Feb. 22 
De La Rue, 
Ph. 
A bright spot. 
4° 
1865 
Mar. 6 
Rutherford, 
Ph. 
A bright spot. 
5° 
1867 
May 11 
8i 
Birt, 
Obs. 
A shallow crater. 
1867 
Oct. 7 
8i to 10. 
Williams. 
yy 
A very bright spot. 
1867 
„ 17 
Ingall, 
yy 
A faint shallow crater. 
1867 
„ 17 
m ■■■■ 
Ingall, 
Williams, 
Williams, 
yy 
Drawn as a crater. 
1867 
„ 17 
13 to 15. 
99 
A very conspicuous crater.* 
1867 
„ 18 
17 to 19. 
Crater very conspicuous, with a 
small central cone casting a 
shadow. 
1867 
Nov. 5 
9 to 10. 
Williams, 
y> 
Very bright, a streak of interior 
shadow on the west. 
7° 
1867 
„ 6 
8 to 10. 
Williams, 
” 
A bright patch of light, streak 
of shadow scarcely discern- 
ible. 
6° 
1867 
„ 15 
18 to 20. 
Williams, 
Very bright.* 
10° 
1867 
Dec. 5 
6 to 8. 
Williams, 
» 
A whitish spot, no trace of a 
crater. 
5° 
1867 
„ 6 
9 to 10. 
•Williams, 
) 
” 
A whitish spot, no crater. 
5° 
* On these occasions Mr. Williams saw a small bright point to the E., which he 
considered to be the highest point of the ridge. 
