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THE PLANET JUPITER.

that the permanency of the Great Red Spot seemed to indicate,that it might he something which, while coagulating or solidi-fying, in some way caused a gap or break in the cloudy regionsabove it, or by its cooling condensed the vapours incumbentupon it, and thus increased its own visibility; in fact, thatwe might be watching in it the gradual formation of a hugecontinent upon Jupiter . But the recent observations of theequatoreal white spot and of some other sirtiilar spots tell us,that, if we see in the Red Spot a part of the body of Jupiter itself, we must find some explanation of the more rapid rota-tion of these other spots. It might not be so difficult toexplain a slower rate of rotation in their case, if they aresimply atmospheric phenomena, but it seems hard to imagineby what means they can be carried steadily round, with aspeed so much more rapid than that with which the globebelow them must be rotating, if the Red Spot is actually apart of it and by its movement indicates the true rotation-period.

If it be the case that the motion of the equatoreal whitespot, to which we have so frequently referred, is uniform, andthat any slight apparent irregularities in its movement arereally due to small errors of observation, it is doubtless possiblethat such a spot may be the summit of some snow-clad moun-tain, which from time to time is more or less clearly seen, oris occasionally altogether hidden by masses of overhangingclouds. Or possibly some volcano there placed may periodi-cally eject vast masses of vapour which may hang over it,and alternately be of such a character as to shine with specialbrightness by reflected sunlight, or to obscure and darken ourview. But if so,—if the white spot be either a permanentfeature of the surface, or originate from such a feature,—may we not well ask whether the Great Red Spot, upon theground of its long-continued regularity of rotation, may notclaim to have a similar location ? And yet this would seemto be impossible, because of its decidedly different period ofrotation. In fact, every such supposition seems to involve us insome insurmountable difficulty in one direction or in another.

We may, however, remark that the generality of observers