ASTRONOMY, PROGRESS OF, IN 1893. 



43 



eyes alternately used, but it was seen the same 

 under nil tln-sr conditions. On seven nights 

 when the satellite WM between them and Jupiter 

 a whitish spot was seen near the south pole, and 

 on two nights when the satellite was beyond the 

 planet, and shortly after passing superior con- 

 junction, the north pole appeared slightly the 

 liri^litt-r. From these and other circuinstances 

 h'- infers that it rotates on its axis synchronously 

 with its revolution around the planet, as does 

 our own moon. 



Phenomena similar though far less conspicu- 

 ous were observed on the other satellites, but the 

 dark color of the fourth failed to show tracings 

 so delicate. Several times a white spot was seen 

 near the north pole, and once near the south 

 pole. On fourteen different dates its disk was 

 seen shortened, and it was found to be circular 

 on eleven nights. 



For full details of these remarkable observa- 

 tions and their discussion the reader is referred 

 to the March, May, and June numbers of " As- 

 tronomy and Astro-Physics," published at North- 

 field, Minn. 



Jupiter's fifth satellite, which is a minute body 

 accompanying the giant planet, has been seen at 

 several observatories, and its existence confirmed 

 beyond doubt. At the publication of our last 

 annual volume but few observations had been 

 made, and, not strangely, some of the data as 

 there given are slightly erroneous. From ob- 

 servations of eastern elongations made by Dr. 

 Barnard, the discoverer, and continued to Oct. 

 21, 1892, the corrected periodic time is ll h 57 m 

 20-5'. Hourly motion in its orbit, 30 11'. The 

 distance of the satellite from the center of 

 Jupiter at eastern elongation is 48*094", which 

 corresponds to a distance of 112,510 miles. 

 Western elongations give a distance about 1" 

 less than the eastern, showing that its orbit is 

 elliptical. It is assumed to be of the thirteenth 

 magnitude. As under the most favorable con- 

 ditions the mammoth telescope of the Lick 

 Observatory fails to reveal its shadow while it is 

 crossing the planet's disk, it is inferred that the 

 satellite is not over 100 miles in diameter. 



Comets. Since Sept. 20, 1892, five comets 

 have been discovered, and one, an expected 

 periodic, has returned to perihelion, as follows : 



Comet f, 1892 (Holmes). Taking into consid- 

 eration the sudden apparition of this comet, its 

 many fluctuations in brightness, and its sub- 

 sequent change from a comet to a nebulous star, 

 it ranks as the most extraordinary one men- 

 tioned in history. So suddenly did it appear, 

 that many astronomers thought it not a comet 

 but the resultant debris from the collision of two 

 asteroids. When first discovered its limbs were 

 as sharply defined as those of the planet Jupiter, 

 and as the size rapidly expanded it was for 

 a while supposed to be approaching the earth, 

 when in reality it was rapidly receding from 

 both the sun and the earth. On Nov. 6 the dis- 

 coverer made its diameter 5' ; on the 14th. 9' ; on 

 the 17th, 12' ; and on the 26th its diameter had 

 increased to 20 . a gain in volume equal to sixty- 

 four times. Such increase of volume in a comet 

 receding from the earth is entirely unaccount- 

 able. By about the middle of December it had 

 grown too faint to be seen save with large tele- 

 scopes, and it continued to decrease until it ap- 



peared as a small, faint planetary nebula. On 

 Jan. 10 it had changed to a nebulous star of the 

 8*5 magnitude, surrounded with nebulosity alxmt 

 10" in diameter. This marvelous transformation 

 from a diffused nebula to a nebulous star must 

 have occurred at some unknown time between 

 Jan. 14 and 16. Dr. Barnard says he saw the 

 change progress from hour to hour. In a 34-inch 

 I. lr>cope the comet could not be distinguished 

 from a bright eighth-magnitude star. As the 

 Biela star shower (occurring once in seven years) 

 was soon expected, and as the comet at discovery 

 was near its radiant, it was, with much reason, 

 supposed to be the long-lost comet of Biela, which 

 since 1852 had escaped observation. 



The elements of Holmes's comet, as computed 

 by M. Schulhof, are : Time of perihelion passage, 



1892, June 13*2379, Paris mean time; longitude 

 of perihelion, 345 53' 12*2" ; longitude of node, 

 331 42' 12-1" ; inclination, 20 47' 22-9" ; peri- 

 helion distance, 2,139; daily motion, 513-548"; 

 period, 6-906 years. These elements bear a close 

 resemblance to those of La Hire of 1678, and also 

 to those of De Vico of 1844. 



Comet a, 1892 (Brooks). On the morning of 

 Nov. 19 Mr. W. R. Brooks discovered a comet 

 in right ascension 12 h 56 m 40' ; declination 

 north 12 59'. This comet possessed no marked 

 characteristics and has been quite easy to 

 observe. Its orbit is a parabola, and conse- 

 quently this was its first and last visit to our 

 system. The following parabolic elements have 

 been computed for it : 



Time of perihelion passage, 1893, Jan. 6'5355, 

 Paris mean time ; node to perihelion, 85 15' 

 05-4" ; longitude of node, 185 39' 05'6" ; inclina- 

 tion, 143 52' 16-4" ; log. perihelion distance, 

 0-077328. 



Comet a, 1893 (Finlay). This is a periodic 

 comet of short period, discovered in 1886, at the 

 Cape of Good Hope, by Mr. Finlay, whose name 

 it bears. On this its first predicted return it 

 was detected by Finlay himself on May 17 from 

 a finding ephemeris calculated from its elements 

 in 1886. It was found almost exactly in the 

 computed place for that day. 



The present elements, which differ but little 

 from those of 1886, which latter are inserted for 

 comparison, are as follow : Longitude of peri- 

 helion, in 1886, 7 34' 29-23" ; in 1893, 7 41' 34'1'. 

 Longitude of node, in 1886, 52 28' 54-06" ; in 



1893, 52 27' 42-7". Inclination, in 1886, 3 1' 

 41-18" ; in 1893, 3 2' 2-1". Mean daily motion 

 in 1886, 533-6901" ; in 1893, 535-8046". 



Comet b, 1893 (Rordame). This was dis- 

 covered with the naked eye by Mr. Alfred 

 Rordame, of Salt Lake City, Utah, on the even- 

 ing of July 8. It had when first detected a tail 

 10 or 15 in length, and was nearing both peri- 

 helion and perigee. The appended parabolic 

 elements have been computed for it by Prof. 

 Boss, but as further observations extending over 

 a longer orbital arc were necessary, they may 

 need slight revision : 



Time of perihelion passage, 1893. July 7'2830, 

 Greenwich mean time ; node to perihelion, 47 8' 

 1" : longitude of node, 337 19' 85" ; inclination, 

 159 57' 50" ; log. perihelion distance, 9-82905. 



On July 19 the comet was photographed by 

 M. F. Quenisset, of France, an independent dis- 

 coverer, with an exposure of forty minutes. 



