. 270 ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 
Applied a new diaphragm to the lamp. Aperture 0.021: 
I: An: n m 
s Centre of bulb to focus, 8 7.9 To lamp, 22 8.0 
m 
10 39 " « 8 110 «. 23 0.0 
1860, March 27th. Adjustments and lamp as on March 24th. 
h m ft. ft. 
9 59 Sid. time. Centre of bulb to focus, 3.70 To lamp, 25.80 ` 
ài 
10 3 - = Se 8.60 vs 
1860, March 30th. A thin, red haze in the sky. Moon 8} days old 
with lamp S, aperture Z, by means of the photometer bulb. 
h m y i ft. i ; ft. 
8 41 Sid. time. Jupiter. Centre of bulb to focus, 2.75 To lamp, 19.5 
8 45 « s ee D E 19.5 
848  « « - E ai 958 "er 195 
8 54 “ Li me LU A RS M ep 1o M PC 
Focus diaphragm applied, admitting pencil from Moon, 32”.47 diameter. 
h m ft. s 
9 4 Sid. time. Bright part of Moon, south of Mare Orisium. - Bulb to focus, 2.90 
y Centre of southern half of Mare Crisium. } a 
ike z Sun's alt. 75°. S Mi 2.42 
9 16 e Brightest part, where Sun is vertical. Boe Share 2.95 - 
Dark part of Mare Tranquillitatis, 9' or 4’) ` = 
9 19 & from Mare Crísium in a line towards the “ 243" 
centre of Moon. . Sun's alt. 50°. SE 
Brightest part as it appears to the naked} - ; 
9 26 a eye, north of Mare Crisium. : oe 2.70 
9 34 « Near centre, 1^ from dark edge. Quid o e “ 1.10 
i A smooth area 30" from dark edge, not Md 
9 39 me specially brighter than other parts simi- “ 0.95 
larly situated. 
25.80 
| (v — GEN 
and distant but a few degrees from Jupiter. 23-foot refractor, with aperture 14", 94 set 
on the planet; eye-piece removed, and the focal image ( without diaphragm), compared 
19.5 
c e lamp, 
EE 
Di 
ft. - 
18.0 
17.5 
16.2 
18.0 
14.2 
20.3 
20.3 
The haze in the air probably obstructed a sensible amount of light, but a the ob- 
jects were near each other, and at a high altitude, it is likely that the relative quan- 
tities of light will be correctly given. 
As the focus diaphragm was not used on this occasion for the planet, it was thought 
advisable to try whether the diffused illumination of the Earth's atmosphere by moon- 
light was sufficient to affect the experiments, but no image from the sky alone could be 
