ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 259 
To reduce our results to the same epoch, we have for the change of phase and dis- 
tance from the Earth, using Lambert's formula, 
Venus at A’ = 0.5394 + — 0.7233 
5 = 0.139. 
8 Venus at Ai = 1.0000 r = 0.7238 
We have also, 
Venus at A’ — 1.0000, »/ — 0.7283, v = 11122 qua 
Log. i > = log. — = 0.556 
TË: Jupiter at A" — 4.2028, ri — 5.2028, v^ 1691 ^ ga 
which must be diminished by 0.008, to refer the phase of J upiter to the opposition 
value, v — 180°; hence, 
Venus at greatest brightness 
Jupiter at mean opposition 
= 0.556 + 0.139 — 0.008 = 0.687 ; 
differing from Seidel's by only 0.013. The agreement is the more satisfactory, on 
account of the dissimilarity of the methods used. 
In Herschel’s * Outlines of Astronomy" * the mean quantity of light sent to the 
Earth by the full Moon is stated to exceed that sent by a Centauri in the proportion 
21408 to 1. This is the result of eleven comparisons made at the Cape of Good Hope 
after correction for the amount lost by transmission through the photometer; the high 
altitude of the Moon makes the correction for atmospheric extinction scarcely sensible. 
As Herschel has apparently used the formula 
AM, = RA sin.? ; v 
to reduce the moonlight at the several phases to the mean full Moon, in order to find 
the above proportion when this reduction is accomplished by means of the formula (29), 
I have computed the following quantities for the eleven dates of observation: — 
Mean value log. M, = 9.962 
« & ^ = 9.769 
dal 
« “ T = 0.026 
D “ D = 0.012 
where s represents the correction for extinction. We shall then have 
* « Outlines,” (817). 
