308 PROCEEDINGS OF THE AMERICAN ACADEMY 



Following. 



1880 



1881 



12 18.0 



By comparing the time of the passages of the red spot on the merid- 

 ian, given in the first part of the abo.ve table, with that given by Mr. 

 A. Marth in the Monthly Notices, Vol. XL., No. 8, p. 496, a dis- 

 crepancy will be found in the time of passage of Sept. 30, Oct. 2, and 

 Dec. 16. I am unaware how this occurred, possibly through an error 

 of mine ; but the time should be corrected, that here recorded being 

 right. 



I have shown elsewhere * that the red spot must have disappeared 

 in 1878, in the same manner as did the angular mark D iu 1877. 

 Tills spot, seen by different observers in July, August, and September, 

 was not seen by me on Sept. 20 ; although, at the time my observa- 

 tion was made, it should have been very near the centre of the disk, 

 and consequently in the best position to be observed. The very place 

 where -the red spot was seen five days later, was occupied by a dark 

 irregular, gray band, commencing near the mark D, and extending 

 east as far as the limb. As the sight was good at the time this obser- 

 vation was made, it cannot be supposed for a moment that it escaped 

 my notice. If it had been there, it must certainly have been seen. 



At the time of this observation, the red spot might have been con- 

 cealed by the dark, irregular band already described, or it might have 

 closed up, as the great variations observed in its size and form during 

 the first year after its appearance would seem to suggest. At first the 

 changes of form of the red sjiot were great and very frequent, and 

 slowly and gradually it acquired the regular and comparatively 6tea<1y 

 shape it has shown for over a year. 



* " On the Recurrence of some of the Markings on Jupiter." The Observa- 

 tory, No. 24, April, 1879, p. 411. 



