ASTRONOMICAL PHENOMENA AND PROGRESS. 



51 



appearances presented by Jupiter in connection 

 with the periodical increase and decrease of 

 spots on the sun, Mr. Ranyard has compared 

 together a number of sketches of Jupiter's 

 belts, made during the last twenty years, and 

 thinks that he detects peculiarities of aspect 

 among them at those times when the solar spots 

 have been at the maximum. 



Jupiter's Satellites. These have recently 

 received the careful attention of the distin- 

 guished astronomical observer, Dr. R. Engel- 

 mann, of Leipsic. He employed for the pur- 

 pose the astro-photometer of Zollner, in which 

 the light of the object examined is referred to 

 that of one or more comparison stars, by means 

 of an artificial star produced by the flame of 

 petroleum, adjustable for brightness and color 

 by a Nicol prism, aud a colorimeter or revolv- 

 ing wheel of rock-tinted crystal. Dr. Engel- 

 mann says that he found the absolute bright- 

 ness of the satellites extremely variable, as 

 all other observers had done, and, from the 

 irregularity and occasional rapidity of the 

 changes, it was impossible to decide, in the 

 case of the three interior satellites, whether 

 the periods of rotation and revolution are 

 identical. This, however, appears to be the fact 

 with regard to the outermost satellite. -At a 

 mean, No. 2 is relatively the most, and No. 4= 

 the least, luminous. The micrometrical meas- 

 urement of the four (taking the sun's parallax 

 at 8" *90) gives in miles the following diame- 

 ters: 2,498, 2,102, 3,551, and 2,962 miles. 

 These values differ but little from those given 

 by Lockyer. The "albedo," or reflecting 

 power of the surfaces of the satellites, is be- 

 tween that of marl and that of white sand- 

 stone for No. 1 ; exceeding that of white sand- 

 stone for N o. 2 ; Varying between marl and 

 quartzose porphyry for No. 3 ; and equal to 

 that of moist arable land for No. 4. 



Asteroids. Four new asteroids were dis- 

 covered during the year, bringing the known 

 number up to 117. They range from the 9th 

 to the llth magnitude. The finders, numbers, 

 and names (so far as given), of these additions 

 to the planetary system are as follows : Prof. 

 Luther, of Bilk, discovered the 113th, named 

 Amalthea ; Prof. Peters, of Clinton, the 114th, 

 Cassandra ; Prof. Watson, of Ann Arbor, the 

 115th, Sirona; Prof. Peters, the 116th, un- 

 named as yet ; and Prof. Borelly, of Marseilles, 

 the 117th, Lorina. The lllth asteroid, dis- 

 covered by Prof. Peters, in 1870, has received 

 the appellation of Ate ; and the 112th, that of 

 Iphigenia. 



According to Leverrier, the total mass of 

 the ring of asteroids does not exceed T^th 

 of that of Jupiter. Prof. Daniel Kirkwood 

 remarks, in explanation of this unparalleled 

 disproportion between two adjacent planets 

 (regarding the mass of minor planets as one 

 body for purposes of comparison), that it is 

 probable that, while the solar nebula was in 

 process of condensation, a large number of the 

 asteroids, when in perihelio, plunged into the 



solar mass and were reunited with it. The 

 powerful mass of Jupiter would produce great 

 eccentricity, in parts at least, of the primitive 

 ring, and large portions of its matter, or a con- 

 siderable number of minor planets in a state 

 of vapor, may thus have been precipitated 

 upon the sun before the latter had contracted 

 within their perihelion distance. He suggests 

 the same hypothesis to account for the small 

 mass of Mars. 



Comets. Dr. Winnecke, at Carlsruhe, dis- 

 covered a faint comet April 7th. Dr. Huggins 

 subsequently examined it on two occasions, 

 and found it a scarcely perceptible coma, with 

 an extension in the direction of the sun. When 

 observed by the spectroscope, he -ascertained 

 the light of the comet to consist almost entirely 

 of three bright bands. A fair measure was 

 obtained of the centre of the middle band, 

 which was the brightest ; giving a wave-length 

 of about 510 millionths of a millimetre. The 

 less refrangible band gave 545 millionths. The 

 comet was similar in constitution to the comet 

 examined by Dr. Huggins in 1868. 



Tuttle's comet returned in November, true 

 to the predictions of astronomers. Its mo- 

 tions were observed at several points in Europe 

 and the United States. This comet has a pe- 

 riod of about thirteen years seven months, 

 and will reappear in August or September, 

 1885. It is supposed to be the one seen by 

 the French astronomer Mechain, in 1790 ; and 

 its orbit was then believed to be parabolic, but 

 is now known to be elliptic. 



Encke's comet, returning to sight in Octo- 

 ber, after its period of forty months, was the 

 subject of interesting spectroscopic observa- 

 tions. On the evening of December 1st, its 

 spectrum was quite distinct, consisting of 

 three bright bands (Prof. Harkness, of Wash- 

 ington reports), the most refrangible one being 

 very faint, the middle one by far the bright- 

 est, and the least refrangible one having an in- 

 termediate degree of brilliancy. The positions 

 of the two brighter bands were measured, and 

 the resulting wave-lengths of the light, ex- 

 pressed in millionths of a millimetre, are ap- 

 proximately as follows : first band, less refran- 

 gible edge, 556; brightest part, 550; more 

 refrangible edge, 534 : second band, less refran- 

 gible edge, 515 ; brightest part, 510.9; more re- 

 frangible edge, 499. The position of the faint 

 band was estimated, and the resulting wave- 

 lengths are, for the less refrangible edge, 458, 

 and for the more refrangible edge, 448. At 

 times, he fancied he also saw a faint, continu- 

 ous spectrum, but could not satisfy himself 

 that it really existed. Both in appearance and 

 wave-lengths this spectrum bears such a re- 

 markable resemblance to that of the second 

 comet of 1868, that Prof. Harkness is strongly 

 inclined to think their physical constitution 

 must be identical. 



The same comet was examined carefully 

 with a double-image prism, without finding a 

 trace of polarization. 



