we were to compare the drawing of Jupiter made on July 9, 

 1878, by Professor Pritchett with one made by ourselves at the 

 present time, it would be difficult to imagine that it was one 

 and the same object. But I cannot help thinking that the 

 drawing published in the Observatory scarcely does justice to 

 the subject. The drawing shows scarcely any sign of Jupiter's 

 two well-known dark belts on either side of the equator, 

 although Professor Pritchett makes constant reference to them. 

 However, from our own remarks made about July, 1878, it is 

 evident that there has been no enormous change in Jupiter's 

 physical appearance. The most noteworthy alterations in the 

 immediate neighbourhood of the red spot have been, first, the 

 formation of that angularity in the southern dark belt imme- 

 diately west of the spot, then the formation of an indentation 

 in the south edge of the belt, and lastly, the evident super- 

 position of that white cloud streak along the portion of the 

 belt west of the spot, which has gradually widened until the 

 belt is now reduced to a mere streak. In 18S3 and 1884, how- 

 ever, the red spot became very faint indeed, and when the 

 definition was unsteady could not be seen at all, even when at 

 mid-transit. During periods of good definition we could just 

 faintly glimpse it, but on most occasions we could only see its 

 northern edge, which merged into a faint coloured streak a 

 little south of the dark belt. The Director of the Dearborn 

 Observatory (Mr. G. W. Hough) seems to have observed this 

 spot all through 1883 and 1884. In his annual report for 1884 

 he says : — " It was seen on various occasions, with the Chicago 

 telescope, entirely separate and distinct from any belt, and 

 presenting the same outline that it did in 1879. The most 

 marked change has been in its visibility. During the latter 

 portion of the previous opposition it became very faint, and 

 was announced to have disappeared, but observations were 

 made on it at the Dearborn Observatory as long as the planet 

 was visible." 



The period of Jupiter's rotation has for a long time been, 

 and is now, a qucestio vexata among astronomers. As early as 

 Cassini's time the period was fixed at 9h. 55m. 80s., and ever 

 since then various observers have deduced periods ranging from 

 9h. 55m. to 9h. 56m. Most of these have been obtained from 

 well-defined dark markings, situated on or to the polar side of 

 the two principal dark belts. 



In 1871, however, Dr. Lohse took some observations of a 

 bright spot near Jupiter's equator, and found the period of 

 rotation of this spot to be less than 9h. 52m. In the "Ephemeris 

 for the Physical Observations of Jupiter," Mr. Marth has 

 until quite recently adopted 9h. 55m. 4s. ; but in the 

 Supplement to the monthly notices of, the "E.A.S.," vol. 



