ASTRONOMY, PROGRESS OF, IN 1890. 



ined in the tails of comets. Prof. Searle inclines 

 to the belief that the light is sometimes variable, 

 but asserts that the delicacy of the work requires 

 independent observation by different astrono- 

 mers made simultaneously, under like atmos- 

 pheric conditions, and kept up for several years. 

 Of the Gegenschein, of which a comparatively 

 large number of observations have been obtained, 

 he says, " All are confessedly uncertain." Though 

 the writer has never seen the Gegenschein at the 

 Warner Observatory, yet he enjoyed at the Lick, 

 in January, 1889, several unmistakable views of it. 

 It appeared as a circular luminous patch of ex- 

 treme faintness, about 5 or 6 in diameter, ex- 

 actly opposite the sun, having a daily progressive 

 motion equal to the sun's apparent motion in 

 the ecliptic. 



The Sun's Motion." Gould's Astronomical 

 Journal" has an instructive paper by Prof. 

 Lewis Boss, Director of Dudley Observatory, 

 Albany, N. Y., on the proper motions of 295 

 stars and his conclusions therefrom regarding 

 the direction of the sun's motion in space. Of 

 all this number of stars, only 49 have been pre- 

 viously used by others in a similar investigation, 

 and, therefore, his determinations are independ- 

 ent of the results obtained by others. The stars 

 were divided into two groups according to mag- 

 nitude, the mean magnitude of the first group 

 6-6, and of the second 8'6. He found the mean 

 maximum motion of the sun, as viewed from the 

 mean distance of both groups of stars, to be 

 13-06" in one hundred years toward a point nearly 

 5 north of west of Alpha Lyrse, right ascension 

 280, declination + 40*. Sir William Herschel's 

 point was 260 34' + 26 17'. The mean place 

 of four determinations by Argelander, Luhn- 

 dahl, Struve, and Galloway is right ascension 

 258 + 28 7'. These results are not in very 

 near accord, yet, considering the intricate nat- 

 iire of the problem, the agreement is, perhaps, 

 as close as could be expected. It is undoubtedly 

 true that the apparent motion of these stars is 

 partly due to a relative motion of our sun, and, 

 of course, of the entire solar system toward the 

 point named, at the rate of 10 or 15 miles a sec- 

 ond ; but whether this latter movement is curvi- 

 linear or rectilinear, posterity, ages hence, must 

 determine. 



Orbits of Binary Stars. Mr. Gore, of Eng- 

 land, has recently published an orbit of Sirius, 

 and finds a period of 58'5 years, and that, with 

 Guylden's parallax ( 0-193"), the sum of the 

 masses of the star and its companion is 26*25 

 times that of our sun, and the mean distance 

 of the components from each other 44*5 times 

 that of the earth from the sun, or about one and 

 a half times the solar distance of the planet 

 Neptune. The same astronomer announces that, 

 from recent measures, the binary star Struve 228, 

 has described about 120 of its apparent orbit 

 since its discovery in 1829. A computation of 

 its orbit gives a period of 88'73 years, and its 

 time of peri-astral passage as A. D. 1906. Its 

 present distance is almost exactly one second, 

 but at peri-astron the components will probably 

 be separated by less than 0-2". It is a very in- 

 teresting binary, which in a few years but few 

 telescopes will be able to divide. Its position is 

 right ascension 2 h 6 m 59 s , declination + 46 58'4'. 

 The magnitudes of the components are 6'7 and 



7'6. He also has deduced the provisional ele- 

 ments of the orbit of Delta Cygni, and makes its 

 period 376*659 years, its peri-astral passage A. D. 

 1914, and its present distance 2-39". For the 

 binary Gamma Coronas Australis, E. B. Powell 

 has calculated an orbit, and finds a period of 

 93-338 years ; peri-astral passage A. D. 1885, -122 ; 

 distance, 2-034", with an annual retrograde mo- 

 tion = 3 51' 25". 



Astro - Photography. A beautiful photo- 

 graph of Jupiter was taken on July 12, 1890, by 

 Prof. W. H. Pickering at his temporary mount- 

 ain observatory on Wilson's Peak, California. 

 Its scale is jTmrimnnr* or 1'65"=1 millimetre 

 magnified (at 29 c.m. distance) 450 times. The 

 13-inch telescope was used. The exposure, only 

 87 seconds long, shows his system of belts with 

 surprising distinctness. At the same place, on 

 Feb. 7, 1890, the planet Saturn was exposed for 

 6 m 16% scale suTJoWn^ or 0'84" =1 millimetre 

 magnified 770 times. Both bright rings and the 

 division between them, also the dark ring and 

 the equatorial belts, are plainly visible. A re- 

 markable photograph of what he calls " an inky 

 black hole" in the Milky Way (coal sack) has 

 been made by Prof. Barnard at Lick Observa- 

 tory. This study is in Sagittarius right ascen- 

 sion 17 h 56 m , declination south 28. Much of 

 its inky blackness is undoubtedly due to con- 

 trast with its surroundings, which are very 

 bright from the mingled light of many thou- 

 sands of telescopic stars. The 16-inch objective 

 of the Warner Observatory shows but five stars 

 in it, four of these needing closest scrutiny, yet 

 the photograph shows myriads of stars, very few 

 of which are visible in the great 36-inch tele- 

 scope. The exposure was continued for 3 h 7 m . 

 The instrument employed was not a telescope, 

 but a portrait camera, the lens having an aper- 

 ture of 5-9 inches. It was mounted temporarily 

 on a rough wooden box and strapped to the tube 

 of the 6|-inch equatorial telescope, which latter 

 was used simply as a pointer. Though driven by 

 clock-work, it was necessary to keep it exactly di- 

 rected on a star by slow-motion hand-rolls, one 

 moving it when so required in right ascension, 

 the other in declination. These vacuities are 

 thickly interspersed along the Milky Way, and 

 Barnard's system of photography will probably 

 reveal countless stars in them all. In observing 

 this hole or cavity Sir William Herschel pro- 

 claimed that he had sounded the depths of the 

 Milky Way with his great telescope, and had 

 penetrated to the dark, starless regions beyond. 



W. E. Wilson, of Ireland, has invented a 

 method of recording transits by photography, 

 whereby personal errors are eliminated. A sen- 

 sitized plate is placed in the focus of a transit 

 instrument, and if a star traverse it uninterrupt- 

 edly, a continuous black line will be found on 



the development of the plate, thus ; 



but if an up-and-down motion be given it by the 

 electric clock, the result is a broken line of this 



sort , each break being equal to 



a sidereal second. With only a rough apparatus 

 the inventor found the recorded' time of transit 

 correct to within one fourth of a second. 



Andromeda Nebula. Isaac Roberts has pub- 

 lished in " Himmel und Erde," and reproduced 

 in the " Sidereal Messenger " for January, 1890, 

 a magnificent photograph of the nebula in An- 



