ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 245 
starlight by the illumination dispersed over the sky, but may, with equal probability, be 
referred to some peculiarity in the Moon itself, which causes it to reflect light more 
freely at some inclinations of the incident and visual rays than at others. 
This result, taken in connection with the wide divergence of Euler's and Lambert's 
formula, making the Moon at quadratures, theoretically, twice as bright as it really is, 
gives a new interest to the investigation, and makes it desirable that it should be sub- 
jected to other tests. One such is afforded in the following considerations. 
If it is true that a change in the brightness of the background of the sky has the 
effect of enfeebling the impression of starlight on the eye, in so high a ratio as the ` 
square of the diffused illumination, the fact should appear on dividing the observations 
of the stars compared into two groups, one comprising those made at a large angular 
distance from the Moon, and the other, those nearest to it; the latter should afford 
results making the stars relatively fainter, in consequence of the greater intensity of 
illumination of the sky in the immediate neighborhood of the Moon. 
The following stars in Herschel's series are favorably situated for showing the influ- 
ence in question. 
Name of Star. Distance from Moon. Qu sty of Ludi. 
6 Scorpii 37 0.169 
d 48 0.150 
ez 100 0.170 
1 Scorpii 45 0.202 
« | 100 0.196 
s Sagittarii 40 0.145 
s 52 0.147 
« Centauri 40 0.930 
« 43 | 1.285 
« "o di 1.120 
pe 62 1.095 ` 
6 Centauri : 40 0.440 
« 44 0.870 
« 45 0.407 
e 65 0.400 
« 65 0.382 
a Gruis 33 0.194 
« 38 0.185 
& 65 0.163 
a Pavonis. 33 0.155 
« ; WT 0.132 
« 72 0.139 
VOL. VIII. 32 
