In the winter of 1868-9 the attention of astronomers was called to the fact that rapid and extensive changes were taking place in the appearance of Jupiter’s belts, and they have consequently been watched from that time with unremitting attention by astronomers furnished with telescopes of the best quality.  The results of these observations are given in two very interesting papers, communicated to the Popular Science Review, by Mr. Webb. [Footnote:  Popular Science Review for April, 1870, and July, 1871.] Very curious markings and variations in the depth of shade have been seen, accompanied by equally curious changes of colour.  Mr. Browning compares these changes to those which are seen when a cloud of steam of varying depth and density is illuminated from behind by a strong light, as when we look through the steam escaping from the safety-valve of a locomotive at a gas-lamp immediately behind it.  This appears to be the true explanation of the phenomenon. [Footnote:  Popular Science Review, 1871, p. 307.] These belts are probably due to vast masses of steam, poured forth with great force from the body of the planet.  As the atmosphere of Jupiter is probably of enormous depth, the rotatory velocity of its upper portions would be much greater than that of the surface of the planet, hence the steam would arrange itself in belts parallel to the equator of the planet.  But this view leads us to wonderful conclusions with reference to the condition of the planet.

“Processes of the most amazing character are taking place beneath that cloudy envelope, which forms the visible surface of the planet as seen by the terrestrial observer.  The real globe of the planet would seem to be intensely heated, perhaps molten, through the fierceness of the heat which pervades it.  Masses of vapour streaming continually upward from the surface of this fiery globe would be gathered at once into zones because of their rapid change of distance from the centre.  That which is wholly unintelligible when we regard the surface of Jupiter as swept like our earth by polar and equatorial winds, is readily interpreted when we recognize the existence of rapidly uprushing streams of vapour.” [Footnote:  Mr. Proctor in Monthly Packet, October, 1870.]

Supposing then that the atmosphere of Jupiter is of very great depth, and thus laden with masses of watery vapour, the effect of a sudden current of heated, but comparatively dry, air or gas would be the immediate absorption of the whole or a large portion of the vapour, and the consequent transparency of the portion of the atmosphere affected by it.  We see this result continually on a small scale in our own atmosphere, when a heavy cloud comes in contact with a warm air current, and rapidly melts away, Many of the rapid changes which have been witnessed in Jupiter’s appearance are readily explained if this view is admitted.  Supposing such a thing to have happened near the edge of the disc, the phenomenon recorded by Admiral Smyth