136 RECORD OF SCIENCE FOR 1886. 



Number 253, discovered by Dr. Palisa on November 15, 1885, has been 

 named Mathilde. 



The influence of phase on the brightness of the minor planets. — Dr. G. 

 Miiller, of the Potsdam Observatory, is led to believe from observations 

 of seven asteroids with a Zollner photometer, that there is a real con- 

 nection between the phase of these bodies and their apparent bright- 

 ness, and that Lambert's law of phase brightness does not apply to 

 them. The planets are separated into two classes. In the first class, 

 class,' which embraces Vesta, Iris, Massilia. and Amphitrite,the changes 

 in brightness are only perceptible as the planet approaches opposition, 

 thus resembling Mars in their behavior ; in the second, which contains 

 Ceres, Pallas, and Irene, the changes in brightness seem to be coexten- 

 sive with the changes of phase, giving a light curve, like that of the 

 the moon or Mercury. 



The asteroid ring. — M. A. Svedstrup gives in the Nachrichten, Nos. 

 2740-41, an interesting abstract of a recent investigation, for which he 

 received the gold medal of the Eoyal Danish Academy — a statistical 

 examination of the orbits of 198 of the small planets, considered as 

 part of a cosmical ring around the sun. The orbit obtained for the 

 " mean planet" shows an inclination of about 6° and a mean distance 

 of 2.64. The mass of this fictitious planet corresponds to an apparent 

 magnitude, at opposition, of 6.7.* 



Relation of the asteroid orbits to that of Jupiter. — Professor Newton 

 points out the interesting fact that the plane of Jupiter's orbit coincides 

 almost exactly with the mean plane of the orbits found for the first 251 

 asteroids, understanding by the mean plane, the plane whose pole is the 

 center of gravity of the poles of the asteroid planes ; the difference be- 

 tween the poles is, indeed, only 30'. 



Jupiter : The " red spot." — The " great red spot," some 30,000 miles 

 in length by 8,300 in width, has now been the principal object of inter- 

 est on the planet for eight years. It was faint during the last season, 

 but far more conspicuous than in 1885. Professor Young obtained, 

 from eight observations made between March 17 and June 29, 1886, a 

 rotation-time of the spot of 9^ 55°' 40».7±0«.2, showing that the 

 remarkable retardation of the period still persists. This is brought 

 out by the following figures : 



In 1879 Mr. Pratt made the period 9^ 55™ 34". 9 



1880-'81 Mr. Hough made the period. . . 37 . 2 



1882-'83 Mr. Hough made the period.. . 38 . 4 



1883-'84 Mr. Hough made the period ... 38 . 5 



1884-'85 Mr. Hough made the period.. . 40 . 1 



1886 Mr. Youug made the period... 40 .7 



Professor Young, on re-reducing Mr. Pratt's observations of 1879, ob- 

 tains 9'^ 55"^ 34^05, and he finds from a series of observations made by 

 Prof. C. W. Pritchett, in 1882, 9^' 55'" 38M5. A small round white spot 



*In the Bull, astron., 3 : 415, this is corrected to 6.0 magnitude. 



