316 



PROCEEDINGS OF THE AMERICAN ACADEMY 



such an effect must necessarily be more powerful than on Jupiter, 

 since the jihoto.'^phere of the Sun is undoubtedly much thicker than 

 the cloudy atmosphere of Jupiter, and of a different nature. 



The following table gives the time of the passages on the central 

 meridian of the second spot described, that is, the sun-spot-like 

 mark. 



1880. h. m. h. m. o / 1880. h. m. h. m. o / 



Nov. 19 8 5 — 40 103 33.6 Dec. 3 5 52 +0 15 329 9.6 



7 34 — 42 215 20.4 



5 13 — 28 162 21.6 



6 21 — 1 6 144 32.4 



The apparent motion of this spot is still more irregular than that of 

 the passages of spot G, and varies from 2.3° to 21° a day ; and be- 

 tween Nov. 30 and Dec. 3, the motion was even retrograde at the rate 

 of 2.7° a day, which means that during these three daj-s this spot 

 had a longer period of rotation than the red spot has. The mean 

 period of rotation of Jupiter as derived from the observation of this 

 spot is d^ 47"' 30.90^ 



Mark I. 



The object to be now considered is the preceding extremity of a 

 remarkable white spot observed towards the end of November, 1880, 

 inside the equatorial belt, near its southern border, and situated at 

 about the same latitude as the mark F above described. On Nov. 

 26, at 6*^ 46™, this mark was apparently under the following end of the 

 great red spot. After Dec. 10, some changes occurred on and around 

 this spot, and from that time it was lost. 



The following are the dates and times of its passages on the centre 

 of the disk. 



The apparent motion of this mark is also irregular, and varies from 

 0.5° to 13° a day, the largest apparent motion having occurred between 

 the 3Gth of November and the 3d of December. 



The mean period of rotation of the planet as obtained from the 

 observation of this mark is 9'' 52™ 52.90'. 



