6 
POPULAR SCIENCE REVIEW. 
more belts were generally distinguishable than in tbe southern ; 
and one of these, outlying the great equatorial zone, was always 
very plain and conspicuous. After the middle of October it 
became indeed an object of considerable interest, for it exhibited 
a series of dark spots and patches, which developed so rapidly 
and moved with such celerity as to give the most distinct evi- 
dence of phenomena of marvellous character. The first signs of 
the disturbance appear to have been noticed by Mr. Dennett, at 
Southampton, at midnight on October 17th, when two dark spots 
were seen just past the central meridian of Jupiter , and in north 
latitude about 25°. These soon became much more conspicuous, 
others formed and they spread out to such an extent that at the 
present time they extend fully half-way round the planet, 
though at the time of their discovery they were separated by an 
interval not exceeding some 20° of longitude. The writer first 
noticed the disturbed state of the belt on the night of October 
24th, at 11 J p.m., when a train of dark spots was visible on the 
west limb (see PI. I. fig. 2). They were detected again on October 
29th and subsequent nights, and the individual spots of the 
group were recorded as they crossed the central meridian of 
the planet. To show how quickly the spots extended them- 
selves along the belt, let us compare the periods occupied by 
the whole group in passing the meridian : — 
Oct. 29 . 
h m 
0 53 
Deg. of Long. 
32-0 
Nov. 2 
1 27 
52-6 
Nov. 8 . 
1 50 
66*5 
Nov. 23 
3 19 
120*3 
Nov. 27 . 
4 21 
157-8 
These spots soon gave indications of proper motion. Their 
period of rotation was about 7J minutes less than that of the great 
red spot, — in fact, between October 29th and December 2nd, a 
comparison of their positions shows them to have made a com- 
plete circuit of the planet ! They had only occupied 34 days 
in traversing the vast extent of the Jovian sphere. A further 
development of the spots in the same longitudinal direction will 
soon have the effect of entwining them completely around the 
planet ; and such appears to be the inevitable result of their 
recent behaviour. We may then expect to see their gradual 
disappearance as distinct spots, though they may possibly be 
perceptible for a long time afterwards under the character of a 
very conspicuous belt lying north of the equator. If this 
eventually proves to be the case, and the future appearances of 
the spots should be critically watched to ascertain whether it is 
so, we shall have a good instance as to how these large belts are 
formed. The inference will be that they are originated by an 
