1 877.] Movements of Jupiter's Cloud-Masses. 201 
We cannot doubt that deep down below the visible surface 
of the planet — that is, the surface of its outermost cloud- 
layers — lies the fiery mass of the real planet. Outbursts, 
compared with which the most tremendous volcanic explo- 
sions on our earth are utterly insignificant, are continually 
taking place beneath the seemingly quiescent envelope of 
the giant planet. Mighty currents carry aloft great masses 
of heated vapour, which, as they force their way through 
the upper and cooler strata of the atmosphere, are converted 
into visible cloud. Currents of cool vapour descend towards 
the surface, after assuming no doubt vorticose motions, and 
sweeping away over wide areas the brighter cloud-masses, 
so as to form dark spots on the disc of the planet. And 
owing to the various depths to which the different cloud- 
masses belong, and whence the uprushing currents of heated 
vapour have had their origin, horizontal currents of tremen- 
dous velocity exist, by which the cloud-masses of one belt 
or of one layer are hurried swiftly past the cloud-masses of 
a neighbouring belt or of higher or low cloud-layers. The 
planet Jupiter, in facff, may justly be described as a miniature 
sun, vastly inferior in bulk to our own sun, inferior to a 
greater degree in heat, and in a greater degree yet in lustre, 
but to be compared with the sun — not with our earth — in 
size, in heat, and in lustre, and lastly in the tremendous 
energy of the processes which are at work throughout his 
cloud-laden atmospheric envelope. 
Since the above article was written news has been re- 
ceived by the Astronomical Society that Mr. Todd, a well- 
known observer of Adelaide, New South Wales, has been 
able to trace the motions of satellites behind the parts of 
the planet near the edge, or, in other words, through those 
parts of the planet’s atmosphere which have hitherto been 
regarded as belonging to the mass of the planet itself. 
