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condensations, and that their form is determined by the velocity 
of rotation. The fact that the singular configurations of the 
central zone, though lying in the region of the greatest speed, 
showed but little trace’* of the general parallelism, may be 
explained on the supposition that the}' lay too deep for this 
disturbing force, which may naturally be most active towards the 
upper limit of the atmosphere. To this, however, it might be 
objected that, if darkness is to be held a test of depth, the north 
temperate belt, at no great distance, gave testimony of an 
action penetrating to a much lower region than that of those 
central markings, whose comparative quiescence thus remains 
unaccounted for ; and the matter seems to require further in- 
vestigation. 
As regards the decided colouring of the equatorial zone, an 
idea suggests itself of two distinct strata of clouds, of which the 
lower reflect a yellower, the upper a whiter light ; or the differ- 
ence might have been ascribed to different thicknesses of a 
yellow atmosphere, but that on this supposition the tint 
should have grown deeper towards the limbs, which I do not 
think was the case. If we may conjecture such a double arrange- 
ment, it would follow that the slight variation in warmth of 
the planet’s seasons is not very directly concerned in the dis- 
tribution of these clouds, as the north or summer hemisphere 
possessed at once the whitest of the luminous zones, and in its 
grey clearings showed a yellower tinge; to which may be added 
what the observations appear to prove, that the coloured zone 
maintained an equatorial position, notwithstanding the de- 
parture of the sun from its zenith. We may, however, suppose, 
from the comparative transparency of the polar skies, that solar 
heat in general is concerned in the production of these clouds. 
Sufficient attention has, perhaps, not been drawn to the per- 
spective of these atmospheric obscurations. In any oblique 
presentation of the luminous zones, their thickness, which we 
cannot imagine to be insensible, would so come into view as 
optically to diminish the open intervals between them ; and 
this diminution would be progressive with the approach to the 
pole ; so that we should have the appearance of such a continu- 
ous brightness in the arctic regions as does not seem to have 
been matter of observation ; and hence we may infer a com- 
parative absence of condensed vapour in those parts of the 
globe. 
I have not been able to corroborate the general assertion that 
the grey belts become much lighter towards their ends. I 
have repeatedly remarked that they faded but little towards 
the limb; and, in the fine observation of Nov. 17, I have 
noted that I hardly thought the difference would have struck 
me if I had not looked for it: the principal belts could then be 
