ON MAPPING THE SURFACE OF THE MOON. 15 
No. 4. Lat. 2° to 4° §,.—14**, 16**, 47**, 69*, 70%, 83*, 15, 18, 20, 22, 
23, 25, 26, 27, 28, 30, 31, 34, 35, 36, 37, 42, 48, 51, 62, 63, 65, 66, 72, 73, 
74, 75, 80, 84, 85, 86, 88, 89, 96, 97, 98, 76+. 
No. 5. Lat. 3° to 5° S.—16**, 19¥*, 38**, 47**, 69*, 70*, 83*, 15, 17, 
18, 20, 21, 22, 23, 24, 25, 26, 28, 31, 34, 35, 36, 37, 42, 48, 62, 63, 64, 68, 
71, 72, 74, 75, 81, 82, 84, 85, 86, 87, 88, 89, 92, 93, 94, 95, 96, 97, 76T. 
No. 6. Lat. 4° to 5° §.—16**, 19**, 38**, 69*, 70*, 17, 18, 20, 21, 24, 
25,35, 42,48, 62, 63, 64, 68, 71, 72, 81, 82, 87, 88, 89, 92, 93, 94, 95, 96, 97. 
Objects. 
Points of the First Order. None. 
Points of the Second Order, indicated thus x :— 
Xe. y*, 8. lat. W. long, 
12) ‘ Oo i 
EVAR 8 oe pce 02385 16357 1 22 9 25 
UP ABT “00000 12187 0 0 et 
BV AB YS oo cays 05379 12573 3.5 7 14 
1 ‘06976 11149 4 0 6 25 
N.B.—The Arabie numerals following the symbols of the areas, and desig- 
nating the particular objects in this and other areas, are intended to be un- 
alterable. See Report Brit. Assoc. 1865, p. 292. 
5° All measures for diameters of craters, unless otherwise expressed, are 
made at right angles to a line joining the N. edge of Dionysius and the 8. 
edge of Agrippa. See Report, 1866, p. 245. 
Mr. Slack has suggested that “ crater-row ” (see letterpress, areas ITV A“, 
IV AS, p. 23, +19, and Brit. Assoc. Report, 1866, p. 259) should be regarded 
as a *‘test object” of the state of the earth’s atmosphere, particularly with 
regard to definition; for example, if the craters, some of which are difficult, 
come out sharply and well defined, and can be seen distinctly and without 
tremor, the earth’s atmosphere is in a good state for observation. When this 
is the case, and neighbouring objects are indistinct, hazy, and ill-defined, it 
may be inferred that such indistinctness is not occasioned by the state of the 
earth’s atmosphere, but is dependent upon some other agency. In accordance 
with this suggestion, it is recommended that in the examination of the fol- 
lowing objects the state of “‘crater-row ” should be first ascertained. 
While these sheets were passing through the press, Edward Crossley, Esq., 
of Halifax, kindly lent the Committee his 7-3-inch achromatic of 12 feet focal 
length, equatorially mounted. This instrument is now in working order at 
Walthamstow, and a systematic examination of the objects in the three areas, 
IV A*, IV Af, and IV A¢, commenced. The numeral of each object thus 
examined is followed by (x), thus ** 1 (x). 
**](x). A mountain-range, forming part of the northern boundary of 
the plain ITV A®? IV A’3, Length of crest 13’-425; do. from the highest 
point westward 10!-255, from the highest point eastward 3'°170; breadth 
of base at highest point 7-645, at eastern end 6'°712, at western end 
6"-239. 
This boundary does not consist of a continuous range of mountains, but of 
detached or broken ranges. Commencing on the east, we have the mountain- 
arm IV A®*° lying in the depression TY Af 41. The mountain-arm IV A‘ *9 
* Tn the British Association Report, 1865, p. 295, will be found an explanation of the 
coordinates X and Y, with the formulz for computing them when the position of the object 
on the moon’s surface has been determined. 
