OF ARTS AND SCIENCES. 311 



the night of Jan. 5, 1881, with the twenty-two inch refractor he is now 

 constructinjf i'or the Princeton Observatory. 



On Nov. 1, 1880, the pink color of the northern portion of the equa- 

 torial belt, situated above the black spots G, which will be described 

 below, became very intense, and upon it wei-e seen many small black 

 spots and specks resembling those observed on the red spot on the 

 same day, and throughout the months of November and December of 

 the same year. 



The red spot has sometimes appeared surrounded by a white ring, 

 which varied in brightness and width. At times it became very 

 brilliant, and appeared as if mottled over by some cloudy specks. 

 This white ring was especially conspicuous in January, October, and 

 November, 1880. From its appearance and brilliancy, it would seem 

 that this luminous ring is formed by an accumulation of clouds, having 

 a higher level than the surrounding surface, and esjjecially that of the 

 red spot. It might be interesting to watch the transit of the shadow 

 of satellites across the common boundary line separating the red spot 

 from the ring, and see if the shadow is deformed by a change of level. 

 But the delicacy of such an observation would be very great, and 

 probably only large instruments could attempt it. On Aug. 2-1:, 1880, 

 I saw the shadow of Satellite I. passing on the thin, white belt separat- 

 ing the red spot from the equatorial belt, and projecting about one 

 third of its disk on the red spot ; but I was unable to detect any 

 distortion of its shape, the sight being poor at the time. On Nov. 1 

 of the same year, the shadow of Satellite II. was observed in transit 

 on the red spot ; nothing unusual in its shape was noticed. The most 

 favorable opportunity for such a delicate observation would be when 

 Jupiter is near its quadratures, and the red spot close to the limb. 

 At such a time, the shadow of a satellite crossing the extremity of 

 the red spot nearest to the limb would be seen under its greatest 

 possible distortion. If there be a change of level between the ring 

 and the red spot, it ought, it seems, to be noticeable under good 

 atmospheric definition, but transits under these conditions must neces- 

 sarily be very rare. 



While treating the subject of the red spot, I should not omit to say 

 that this object has not always been unique. While in the Paris Obser- 

 vatory, on Sept. 18 or 19, 1879, I had an opportunity of observing 

 Jupiter with an excellent refractor of eight or nine inches' aperture 

 made by MM. Henri Brothers. At the moment the observation was 

 made, the great red spot was a little to the east of the middle of the 

 disk. Right above and a little preceding it were two small, roundish 



