THE PLANET JUPITER.

313

longitude on the Red Spot in 24 terrestrial hours ; so that inrather less than 44 d 10f h , it performs one more revolutionround the planet than is achieved by the Great Red Spot.Between 29 m past 9" on November 19th, 1880, and 43“ past9 h on December 24th, 1881, he finds that the latter wentround 967, and the former 976 times.

But even this rate of rotation has been exceeded in the caseof a series of small black spots, which appeared some distanceto the north of the planet’s equator in October 1880. Hefound that these travelled once round in so short a time as9 1 ' 48 m ; so that in 117 of our days they completed one morerevolution than the previously mentioned white spot per-formed.

This speed was so exceptional that we may probably attri-bute it to some extraordinarily violent current in which theywere involved; although it is, of course, quite possible, thatthe increased rapidity of rotation in question may simplyhave been due to the fact that these spots were at a lowerlevel than those which we most often behold. If so, it maybe, that the globe or central portion of Jupiter is rotating, ata still lower level, faster than any such spots.

We believe, however, that Mr. Denning, whose opinion withregard to the equatoreal white spot which he has observedwith so much perseverance and skill has a special claim uponour attention, is, upon the whole, rather disposed to regard it,either as a permanent feature of the planet, or as in some wayconnected with some such feature which may be situatedbeneath it, notwithstanding that its rate of rotation is slowerthan that of the last mentioned small black spots.

For our own part, we feel that the greatest possible difficultyis involved in any attempt to formulate a theory of what may bethe physical condition of Jupiter , or of the relation of its spotsand belts to that condition, and to the regions upon which theyare superimposed. So much is doubtful, so much apparentlycontradictory, so much inexplicable, that we fear that the wholeproblem must be considered to be one for future solution,rather than one which can at present be solved.

We must confess that we were at one time inclined to think