132 
TOPULAR SCIENCE REVIEW. 
which could hardly, from the rotation, have been identical 
with the little lengthened cloud in a similar situation on 
Nov. 17. 
This equatorial region, comprising the yellow zone and its 
grey borders, lay a little south of the horizontal line bisecting 
the disc. I first noticed this on Nov. 6, the day previous to the 
opposition, and have almost always recognised it when my 
attention was directed to the point. My estimates, however, 
of the relative proportion of the breadth of this central region 
to that of the parts of the disc north and south of it, from 
which the amount of obliquity would follow, were not as accord- 
ant as I could have wished ; but some allowance may be claimed 
in the case of such minute quantities. Nov. 19, assuming the 
breadth of theregion=l, I considered the north segment of 
the disc =1^, the south = 1 J. I found, however, on referring 
to my previous sketches, that this must have been in error, and 
repeating the comparison on Dec. 11 and Dec. 15, I made the 
proportions north = 2^, south = 2 £, and in these I long con- 
tinued to acquiesce. Feb. 25, however, I felt doubtful as to 
the existence of any difference, either side appearing = 2£ or 2^. 
Feb. 26, the previous estimate returned. March 5, the planet 
from its west azimuth passing almost vertically through the 
field, I gave it south = 2, north = 2^ ; and a subsequent com- 
parison of my various sketches led me to think that this must 
be nearer to the truth than and 2^, which makes the graphic 
projection of the central region too narrow for the eye. On 
March 10, I found the estimate of 2Jq-l-f2 confirmed; as- 
suming this, therefore, to be “ within blundering distance,” it 
gives the value of the optical displacement of the centre about 
0*095. That due to the inclination of the planet’s axis + his 
longitude would be 0*070: from which we may infer that the 
appearance was not deceptive, and that the centre of the coloured 
band actually coincided with the equator of the planet.* The 
agreement, though of course but a very rough approximation, 
is the more satisfactory, as I was not aware, till towards the 
last, of the direction of the axis. I do not know that the 
obliquity of the planet’s equator, as indicated by the unequal 
division of the disc, has been previously matter of direct obser- 
vation. The belts had always been considered straight by me 
till March 10, when I fancied the equatorial region curved : an 
instance probably of the influence which previous knowledge 
has upon the eye. 
We now leave this region of singular configuration, and pro- 
* For this determination I am chiefly indebted to the kindness of Mr. 
Proctor. The direction of Jupiter’s axis is not given in ordinary astrono- 
mical treatises. 
