CONDITION OF THE LARGER PLANETS. 
45 
the heaviest known elements. Of course there is no sncli 
pressure, no substance exists at that density, sixty miles below 
the visible limits of Jupiter’s atmosphere, nor ten thousand 
miles lower yet. No gas could remain as such at ordinary tem- 
peratures beneath a pressure which would make it as dense even 
as water ; and if strata could and did exist in Jupiter at the 
higher pressures and densities named, he would weigh many 
thousand times as much as he actually does. But we are again 
forced to the belief that, unless his atmosphere is made of sub- 
stances altogether different from any with which we are- 
acquainted, there must he some power at work to prevent the 
compression which would otherwise inevitably result from the 
tremendous attractive energy of Jupiter’s mass. That power 
can be no other than the fierce heat with which his whole frame,, 
his atmosphere (and all hut the exterior strata outside the 
outermost cloud-layers) are instinct. 
It appears to me that a fourth argument of very great force 
can be derived from the cloud-belts in the atmosphere of Jupiter 
and his brother giant, Saturn. 
The existence of well-defined belts is proof positive of the 
existence of different rates of rotational motion. For instance, 
we cannot explain our own trade-wind zones, without taking 
into account the different velocities due to rotation near the 
equator and in high latitudes, — matter flowing towards the 
equator lags behind, matter flowing from it travels in advance, 
and in either case zones are formed. If a similar explanation 
could be given of the belts of Saturn and Jupiter doubtless they 
would be accounted for. But where are we to find the varieties 
of heat in various latitudes of either planet which could account 
for the multitudinous belts sometimes seen ? or how, if the sun’s 
slow action on these remote and large planets were in question, 
could we account for the rapid formation and dissipation of 
cloud-belts ? The largeness of these planets is a point of im- 
portance to the argument, because the larger a planet the less,. 
cceteris paribus, is the variation of temperature for any given 
difference of latitude measured as a distance in miles. If then 
we cannot look for the required differences of rotational velocity 
where we find them in our earth’s case, it is clear we must turn 
to difference of rotational velocity on account of difference of 
distance from the axis, not at places in different latitudes, but 
in places at different levels. In other words, we must conceive 
that under the action of the planet’s intense heat vaporous 
disturbances of the nature of uprush and downrush are con- 
tinually taking place. Matter rushing upwards from low levels 
to high levels, where the rate of rotation is very much greater, 
lags behind, while matter rushing downwards is carried in 
advance, and thus cloud zones are formed. 
