688 PROGRESS OF ASTRONOMY FOR 1891 AND 1892. . 



+0."10 with a probable error of 0."01. As the annual proper motion 

 is 3", this parallax implies that the star is moving through space at a 

 rate of 88 miles a second. Dr. Franz's result is considerably smaller 

 than that obtained by Prof. Geelmuydeu from transit observations, 

 7r=0."27 from differences of right ascension, and O."24froin differences 

 of declination. 



DOUBLE AND MULTIPLE STARS. 



Gore's catalogue of binary stars. — Mr. Gore has compiled a useful 

 catalogue of binary stars, for which orbits have been computed, giving^ 

 besides the elements, date of computation, etc., the magnitudes, colors, 

 spectra, hypothetical parallax, observed parallax, relative brightness, 

 and the constants A and B for use in Mr. Rambaut's method of com- 

 puting the parallax from the orbital motion of the star in the line of 

 sight. The more recent measures are given in a series of notes. The 

 catalogue was originally comumnicated to the Royal Irish Academy, in 

 June, 1890, and has been reprinted from the Proceedings. 



Prof. Asaph Hall has made a further discussion of the relative motion 

 of the two components of 61 Oygni and the question whether there is 

 anything in the nature of a physical connection between the two. His 

 conclusion is in favor of such connection, but although accurate obser- 

 vations of the mutual distances and angles of position date from 1825, 

 and Prof. Hall includes in the discussion those made by himself up to 

 1801, it is not possible to reach any result with regard to the period of 

 revolution, except that it is long. 



Two lists of double stars discovered by Mr. Burnham, most of them 

 with the 36-inch refractor, have appeared during 1802, bringing Mr. 

 Burnham's double star discoveries up to 1264. Most of his measures are 

 of the more difficult or interesting doubles, a measurement of 0".l being 

 apiiarently quite a simple matter. Mr. Burnham has also published a 

 number of investigations of double star orbits, and collected lists of 

 measures. 



Among lists of recently published measures of double stars should 

 be mentioned the series of observations of 050 stars by Prof. Hall made 

 from 1880 to 1801, with the 26-inch equatorial, of the United States 

 Naval Observatory. With reference to the reduction and discussion 

 of double star measures, Prof. Hall says: "The formuhie and corrections 

 for personal equation of observation seem to me of doubtful utility, and 

 a better way is to compare the measurements of the same star by 

 different observers. " 



Discovery of double stars by means of their spectra. — In the review 

 of astronomy for 1889-'00 attention was called to Prof. E. C. Picker- 

 ing's discovery of the dui)licity of C Ursi? Majoris and fJ Aurigie 

 through pecularities in their spectra which indicated differences in the 

 motions of supjiosed components, , 



