272 



NA TURE 



[January 21, 189: 



corresponding to the sun-spot minimum in 1878 may, perhaps, 

 be connected, as in the case of the four months' curve, with the 

 rainfall. A smoothed curve of humidity for September rises, 

 I find, to a high maximum in 1880. The June humidity curve 

 does the same, and if it be therefore asked, why we should not 

 have a similar failure in that month's curve, I would invite 

 attention to the fact that the rise to the maximum in the humi- 

 dity curve for June is a rapid one from the absolute minimum 

 (reckoning from 1858) in 1876 ; while the rise in September is 



predicted time, given in Marth's ephemeris {Monthly Notices, 



March 1891), is 5h. 32'6m., so that the spot was io'4m. late, 



and this means a decided slackening in its motion of rotation 



during the present apparition. On August 7, 1891, I saw the 



i spot pass the central meridian at iih. 32m., or only 2'3m. after 



i the time indicated in Marth's ephemeris. In the interval of 



! 5 months, during which 362 rotations were performed, the mean 



I period has been 9h. 55m. 42s., which is nearly i second greater 



j than the rotation period of this marking as observed here during 



more gradual from an absolute minimum in 1870. Thus, the 

 wave in June corresponding to the sun-spot minimum in 1878 

 might be regarded as but partially formed, the growing humidity, I 

 or rainfall, presenting its normal culmination. ] 



However this may be (and I do not press these suggestions), ' 

 it has seemed to me desirable to submit the coincidences pre- i 

 sented in the diagram (which I have difficulty in thinking wholly j 

 fortuitous, and which are quite in harmony with the general view | 

 enunciated by Kbppen) to minds more competent to estimate j 

 their nature rightly. A. B. M. i 



any previous opposition. In 1890 I determined the period as 

 9h. 55m. 40"2s., which differed very slightly from that derived 

 from my observations in 1887, 1888, and 1889. It now appears, 

 however, that a marked retardation has occurred, and it remains 

 to be seen whether this will be maintained until the close of the 

 apparition. 



The spot continues to be a fairly conspicuous object, and it 

 retains its oval outlines, but it is not nearly so dark and definite 

 as it was in the years from 1878 to 1881. 



Bristol, January 10. W. F. Denning. 



The Red Spot on Jupiter. 



The Implications of Science. 



On January 4 last, at 5h. 43m., the red spot on Jupiter was j Dr. Mivart complains that in my last letter I merely 

 estimated to be on the central meridian of the planet. The ' affirmed without arguing. This is in a measure true as, to 



NO. II 60, VOL. 45] 



