OBSERVATIONS ON JUPITER IN 1870-71. 
277 
spheric conditions were on the whole inferior to those of the 
preceding season, and to this cause we may refer a general 
feebleness in the markings of the disc, which contrasted disad- 
vantageously with some of the former views. A suspicion, 
however, does exist that the cause may have lain in the planet’s 
own atmosphere. 
The colouring of different regions of the disc has con- 
tinued relatively unchanged ; on the whole, however, it has 
usually appeared less intense and marked by less contrast 
than previously. It must be borne in mind that the memory 
of the eye is no adequate substitute for actual comparison; 
yet it seems probable that some amount of equalisation has 
taken place, and from several observations it may be inferred 
that some sides of the globe present more plainly than others 
the remains of the contrast so fully developed in 1869, between 
the brownish yellow of the equatoreal zone and the grey purple 
of the North temperate belt. The North polar region has been 
sometimes noted of an iron-grey hue. If we now proceed to 
refer to other details, commencing from North, we find this cap, 
or clearing, which, divested of its foreshortening, must be of 
very considerable extent, little varied in appearance. Its 
streakiness is once only expressly recorded ; on another occasion 
it is referred to as barely, if at all, perceptible, and was always 
very inconspicuous. The South edge of this region, however, 
exhibited many changes, in part physical, in part merely op- 
tical, from the various presentations of the globe. Towards the 
North temperate belt there was always a lighter tract, some- 
times only an undefined greyish space, at others a sharp white 
zone. Dec. 14, this zone was of considerable breadth, and 
divided, nearer to its North edge, by a narrow belt, darkest in 
the centre of the disc, and diverging towards North in its East 
half, which was also somewhat wavy or ragged. This streak, 
a feebler companion to the great North belt, was frequently 
seen, but seldom in such perfection, and sometimes could not 
be detected ; traces of its irregular form returned once or twice, 
but much less distinctly : it evidently occupied in strength but 
a small portion of the circumference, and as the season went on 
this region became less strongly marked. 
The North Temperate Belt , though still a prominent fea- 
ture, was repeatedly noted as considerably feebler than for- 
merly, or approximating to the two torrid belts in colour 
and depth. Its character in these respects varied either 
actually, or from optical causes, or both. On some occa- 
sions, especially Jan. 7, I thought it had a yellowish fringe 
on the South side, as I had remarked more than a year before, 
and on Jan. 16 I fancied such an appendage on either edge. 
Two or three times it seemed to thin off a little towards the East 
VOL x. — NO. XL. u 
