OF ARTS AND SCIENCES. 317 



Mark J. 



The mark of which the passages on the central meridian are here 

 tabulated is the preceding end of a conspicuous white cloudy form 

 belonging to the southern side of the equatorial belt. This mark occu- 

 pied very nearly the same parallel of latitude as did the marks F and 

 I. already described. On Nov. 8, at 10** 35"" it was on the central 

 meridian with the centre of the great red spot. After Nov. 18, 

 this mark changed so much that it could no longer be recognized 

 among the other forms of the cloudy belt of the equator. 



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



Nov. 8 10 35 On meridian. 335 49.2 



" . 9 5 52 + 28 315 28.8 



" 11 7 10 — 10 303 57.6 



The considerable apparent motion between the 8th and 9th of No- 

 vember must be very nearly correct, as both observations were carefully 

 made, and while the mark was on the central meridian. The jump 

 made on that day was over 20° ; after that, the mean forward motion 

 was only about 3° daily. 



The mean period of rotation of Jupiter as obtained from this mark 

 would be Q"* 52" 15.0'. 



Mark K. 



Towards the beginning of October, 1 880, the red spot was preceded 

 by a long grajush band, cut sharply and obliquely at its preceding end, 

 and from there extending to within a few degrees of the preceding end 

 of the red spot. As this band was situated only a few degrees more to 

 the south than the red spot, I thought it worth while to study its 

 behavior. After Oct. 13, this band contracted rapidly, both of its 

 extremities either retreating towards each other or dissolving ; but 

 after the 25th it expanded again lengthwise until the 31st, and was 

 lost entirely the following day. 



The passages here given are those of the preceding extremity of 

 this band. 



1880. li. m. h. m. o j 1880. h. m. h. m. a j 



Oct. 25 7 6 On meridian. 260 52.8 

 " 31 11 42 +10 251 49.2 



Oct. 3 8 57 + 28 252 21.6 

 " 12 11 25 on meridian 258 21.6 

 " 15 8 59 " " 202 12.0 



Contrary to the behavior of all the other markings, the apparent 

 motion of this object, when compared with that of the red spot, was 

 retrograde at first, and direct at last. 



The rotation period obtained from this object equals 9'' 55" 22.5". 



