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THE PLANET JUPITER.

W. Herschel found that some spots gave a period differingfrom that of others by as much as five minutes. And it iscertainly in very remarkable agreement with this statementthat we read in the recent Report of the Dearborn Observatory,Chicago , by Professor Hough, dated May 1881 that the timeof rotation deduced from the Great Red Spot was 9 h 55"' 35 s ,while that obtained from certain white spots seen near to theequator varied from 9 h 50'' 06 s to 9 h 50" 9 - 8 s , a value morethan 5 minutes less than the above. On the other hand, fromsome spots nearer to the poles than the Great Red Spot theperiod obtained was as large as 9 h 55 m 39 s , or even 9 1 ' 55 m 40p.

Again, Dr. Lohse of Bothkamp, who has given great atten-tion to the determination of the comparative speed of thespots seen in various latitudes upon Jupiter , mentions onewhich, in the year 1871, appeared to go round in about 3|minutes less than the 9" 55 m 203 s assigned as the planet’srotation-period by Airy.

Professor Hough’s recent observations have been confirmed bythose of Mr. Denning, M. Terby, and others, who have watchedwith especial care one remarkable white spot, which persists inappearing from time to time in a certain latitude a little to thesouth of the equator. From Mr. Denning’s frequent observa-tions of it during the past two years Mr. Marth has obtaineda rotation-period of only 9" 50 m 6'6 8 , while some earlier obser-vations, if taken into account, would still further reduce theperiod by about 1^ seconds.

But perhaps, after all, the greatest interest at presentbelongs to the determination of the rotation-period of theGreat Red Spot, for .which the most accurate value yet de-duced from the very numerous observations of many excellentastronomers appears to be very nearly 9 h 55 m 34^ s . Thisvalue, it will be noticed, agrees very closely indeed with Pro-fessor Hough’s result.

So considerable a difference of speed in spots seen in differentlatitudes is certainly very remarkable. And Mr. Denning, towhom the credit is due of drawing special attention to theabove-mentioned equatoreal white spot by his long and accu-rate observations of it, informs us that it gains 8'1° of Jovian