66 RECENT CHANGES IN THE SURFACE OF JUPITER. 
one of the real difficulties that is constantly presented to the 
observer to distinguish one from the other, and so far as my 
constantly recur in the same place will be recognised as fixed, and 
we shall learn to what extent the clouds change the appearance of 
the planet’s markings. the measures given we a the 
division of the planet into zones in a general way corresponding 
ss those on the earth ; we have the equatorial belt, amt two in the 
mperate zones where the trades end; ours of course 
ends with the sun in his course 234 degrees on each side of the 
equator, but in Jupiter the sun’s change of declination is only 
three Serene so er the — — seem fixed or pein 80. 
in the given time; but this ae based as it is upon the 
possible velocity of the terrestrial winds, must be received with 
caution ; because we know that clouds are not always caused 
ut in some cases seem to form or disappear in afew mainutes 
over terrestrial areas so great that it would be impossible for aly 
wind to travel fast enough to form them. I have known 
form in five minutes over the whole of a clear sky, and disappest 
at other times with similar rapidity. Now the le 
which we can place the horizon limited by such 
so that the clouds must form over a spot 80 waa s in 
least in five minutes ; ; and for any wind to do this wo 
velocity of 960 miles in an hour, a speed which we meg 
ould mean & 
the. aes 
such causes of change act upon both planets, or cconal the | # 
peek eS is an interesting question upon W 
to make some remarks presently. 
Turning again to the principal belts eo pian 4 
some of levinigeaae ace taken, being ar 
referred in the preceding remarks. I wish they had 
some years since, but I did not foresee their impo: 
