.930 ` ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 
Breen, observing an occultation of the planet with the Northumberland Equatorial, 
in May, 1850, noted very little difference of color between it and the Moon. 
At its emersion from the Moon's bright limb, May 23, 1860, I could discern no dif- 
ference of tint; this, however, was in the daytime, when both objects were compara- 
tively faint. Midler considers the prevailing tint of Jupiter to be yellowish, that of 
the belts, brown and lead-color;* while the Moon is in some parts pure white, in 
others steel-gray, or tinged with green. 
Tints of brick-red or of reddish-brown, and others of a bluish cast, slate, or lead- 
color were sufficiently evident upon Jupiter in 1860. It deserves notice that the 
shades of coloring were unusually marked in the early part of this year, at a time 
when the photographic image presented a decided inequality of action in different 
parts of the disc. On January 30th, 1860, this was apparent in the formation of a 
zone between the parallels of 20° and 30° of north latitude in an exposure of two or 
three seconds, another, less strong, showing itself in the southern hemisphere; the 
intermediate equatorial zone had less intensity, and the margins of the disc were much 
fainter than the central parts. SecchiT describes the principal belt as decidedly red, 
with several bands of green and white alternating. Others mention red and blue tints, 
more particularly the former. 
The evidence is quite sufficient to show that the colors of the Moon and Jupiter are 
too nearly alike to furnish an explanation of their very unequal chemical energies. 
The distribution of light over their discs, so far as this is indicated by photography, 
presents a striking contrast. The full Moon invariably develops first at the margin, 
and Jupiter as decisively in the centre, in this particular resembling the Sun, although 
the defect of illumination at the edge of the latter is less in proportion than with 
Jupiter. The distortion of the figure generally apparent in the photographs of Ju- 
piter can only be ascribed to the unequal intensity of the rays from different parts of 
the disc. 
In a group of images taken October 8th, 1857, the light action is much more uni- 
form than in 1860 ; the narrow stripe at the equator, noticed also on the next evening, 
contrasts curiously with the images on January 30th, 1860. In both, the deficiency 
at the margin is best exhibited in the difference of size of the images at different ex- 
posures. With the Sun and Moon the contrast in this particular appears most plainly 
while the image is developing. 
For the purpose of comparing. the photographic power of sunlight with that of 
..* Populäre Astron., p. 226. t Monthly Notices Astr. Soc., Vol. XX. p. 71. 
