246 ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 
For the quantity of light, the numbers are given as computed by Herschel, by a 
process explained in the work above cited,* which gives the brightness of each indi- 
vidual star in parts of a common unit, and freed from the average of the perturbations 
common to all the stars observed on any one night. ‘Those dates only have been em- 
ployed for the purpose now in view, which afford a sufficient number of stars for a 
reliable mean value of p*; with this precaution, the peculiarities appertaining to each 
star, on any one night, ought to discover themselves. 
In the following results, the column headed “ Relative Brightness” is the ratio be- 
tween the light of the star determined at the smaller of the two distances from the 
Moon, compared with the light of the same star when at the greatest distance. 
Name of Star. Distances from Moon. Relative Brightness. Wt. 
[e] o 
6 Scorpii | 37 100 1.00 3 
48 100 0.88 
1 Scorpii 45 100 1.03 5 
e Sagittarii 40 52 0.98 1 
« Centauri Cer EE 62 1.00 8 
B Centauri 43 65 1.04 4 
a Gruis : 35 65 1.17 8 
œ Pavonis 40 72 1.04 4 
Mean by Weights 42. 78 102 + 0.011 
This result does not indicate any appreciable influence from the greater amount of 
diffused illumination of the sky in the neighborhood of the Moon, and is, therefore, 
unfavorable to the hypothesis that the abnormal variations of brightness of the stars 
relatively to the Moon, from night to night, are to be explained by an increase in the 
quantity of moonlight dispersed by reflection in the atmosphere, over the whole sky. 
We have already seen that photographic experiments indicate a peculiarity in the 
chemical action of moonlight at the several phases compared with the full, and from 
the above discussion it would seem that the visual rays are affected in an analogous 
manner, and to an extent not accounted for in Euler’s nor in Lamberts theory, — in 
other words, the brightness of the Moon increases too rapidly between the half-moon 
and the full phases. 
In order to leave no doubt as to the reality of the discrepancy between the amount of 
light actually received from the phases and that indicated by the proposed theories, and 
of its being properly referable to the Moon itself, I have compared the latter with a fixed 
* Results of Astronomical Observations, Cape of Good Hope, p. 365 
