720 PROGRESS OF ASTRONOMY FOR 1891 AND 1<S92. 



j^lare of JLii)itei-, it would perhaps not be fainter than the tliirteentli 

 magnitude. 



The satellite has been seen and its position observed at the University 

 of Virginia, at Priuceton, at Ealing, and at Evanston; the 18.] inch re- 

 fractor at Evanston ])eing apparently the smallest instrument with 

 which it has thus far been seen, and it was then reported as being a 

 much more difhcnlt object than Ariel or rmbriel, the satellites of 

 Uranus, though Mr. Reed with tlie lio-inch Princeton glass found it 

 an easier object than Ariel. 



The new satellite's orbit seems to lie sensibly in the i)lane of -hipiter's 

 equator; the distance of the satellite from the center of the planet is 

 probably over ll(),()(){) miles and its [)eriod of rotation about 11'' 57'" 37\ 



Diameter of Jupiter. — An admirable series of measures of the diam- 

 eter of Jupiter, by Dr. Schur, with the (Kittiugen heliometer, is pub- 

 lished in No. 3073 of the Astronomische Wachrichfen. The effect of per- 

 sonal eqnation was eliminated by the use of a reversion prism eye- 

 piece. Dr. kSchur tinds the disk a sensibly true ellipse with diameters 

 37".4: and liry.i), a Hattening of l-15i. 



Mr. Burnham communicated to the November meeting of the Royal 

 Astronomical Society, in 1891, a paper on the spots and markings of 

 Jupiter as observed with the 12inch equatorial of the Lick Observatory. 

 Noting the decided changes of color in the different markings on tlie 

 planet's surface, he expresses the opinion that the red color is an indi- 

 cation of age, or, in other Avords, when a spot or marking other than the 

 white spots first appears it is dark or black, but after some time turns red. 

 During the year 1801 the planet was extremely interesting, owing to the 

 remarkable amount and variety of detail displayed on its surface. The 

 two hemispheres were, as usual, strongly in contrast in their individual 

 markings. In the southern hemisphere, besides the great red spot, 

 new spots api)eared, and a great number of round white spots were visi- 

 ble. These white spots are quite characteristic of the southern hemis- 

 pliere, though individual white sjiots have at rare intervals been seen 

 in the northern liemis[>here. In the latter a system of small dark spots 

 appeared, with very short periods of rotation. Mr. Burnham reports 

 that the great red spot liad regained much of its former distinctness, 

 both in color and form. 



Saturn. — On September 22, 1891, the earth ])assed through the 

 ])lane of Saturn's rings. From the 22d of the month to October 30 the 

 earth was above the plane of the rings, while the sun was below that 

 l>hine and, consequently, sliining on the southern side of the rings. 

 After October 30 the sun was again shining on the north side. Tlie 

 phenomenon of the disappearance of the rings was described by sev- 

 eral observers. 



Uranus. — A search ibr new satellites made by several observers at 

 the Lick Observatory from 1889 to 18;) L has resulted negatively. The 



