OF ARTS AND SCIENCES. 



313 



the times of its observed passages ou the central meridian, together 

 with those observed after the iGth. 



It is noted in the observing book, on Dec. 23, that the forward 

 motion of tlie spot seemed to have decreased. Great irregularities 

 will be found in the motion of this spot, amounting from five to 

 thirteen, and even in one case to tweuty-uine degrees in a day. It 

 may be that the mai'k observed on Jan. 17 was a different object 

 altogether, otherwise a large jump has occurred there. 



This mark, which lasted at least from the end of August, 1880, 

 seems now to have disappeared, as no traces of it have been seen for 

 over fifteen days. The mean jDcriod of rotation of this mark equals 

 9^ SI™ 8.30\ 



Mark G. 



Another very conspicuous spot, or rather a series of spots, was also 

 carefully watched from the end of October to the end of December, 

 after which it disappeared. 



On Oct. 28, 1880, great changes occurred in the equatorial belt, 

 especially on its northern half, the white, cloudy forms of the central 

 zone changing their shape. At the same time, the delicate rosy color 

 between the cloudy belt near the northern border of the equatorial 

 zone assumed an intensity of color rarely seen, and almost equal to 

 that of the red sjsot, although of a different shade. While these 

 changes were going on, a row of five black spots, some of which re- 

 sembled closely the shadows of satellites in transit, only not quite so 

 black and not so sharp in outline, was observed in the northern 

 hemisphere of the planet, forming part of the gray band nearest to the 

 equatorial belt on that side. The first spot of the series on the pre- 

 ceding side was on the central meridian at the same time that the 

 following end of the red spot crossed this line on the 28th of October. 



