ASTRONOMY. 143 



STELLAR SPECTRA. 



Photograph ic study of stellar spectra. Ilcnr}/ Draper memorial. — Pro- 

 fessor Pickering', in his annual report for 1888, presents the proj^ress 

 made iii the various investigations of steHar spectra as follows : A cata- 

 logue has been prepared of the spectra of 10,875 stars, covering the 

 entire sky north of — 25o. The Sinch Bache telescope has been used 

 for this work. Six hundred and thirty-three plates have beeu taken, 

 and 27,953 spectra have been examined. The type of spectrum is 

 given in each case, and in sibout six thousand cases additional lines are 

 visible aud have accordingly beeu described. The photographic in- 

 tensities of the spectra have also been measured, giving a photometric 

 measure of the stars by which those of difierent colors may be com- 

 pared. The first draft of a spectroscopic catalogue has been prepared, 

 including the place of each star for 1900, its designatiou and magni- 

 tude in various catalogues, its photographic brightness, aud the descrip- 

 tion of each spectrum. The photographs required for the second inves- 

 tigation on the spectra of the fainter stars are nearly completed. The 

 instruments employed in both of these investigations were prepared 

 for shipment to Pern, where the work will be continued among the 

 southern constellations. Tlie detailed study of the brighter stars with 

 the 11-inch Draper telescope has been extended by the use of plates 

 stained with erythrosin. The sodium line D in these spectra has thus 

 been i)hotogTaphed as a double line. A catalogue has been formed of 

 the lines in some of the brighter stars. In Sirius the lines, except 

 those due to hydrogen, are very faint. But nearly four hundred of 

 them have been measured in different photographs of this star ; fifteen 

 are recorded between the lines H and K. A beginning has also been 

 made of the study of the spectra of the variable stars. 



Dr. von Koukoly and his assistant, Dr. Kovesligethy, have carried 

 the spectroscopic surv^ey of the heavens begun by Vogel and Duner to 

 15 degrees south declination, aud have published their work in volume 

 8, i)art 2, of the O'dyalla observations. The instrument used was a 

 Zolluer spectroscope. Vogel's arrangement of types was followed. 

 The catalogue contains in all 2,022 stars, down to 7.5 magnitude. But 

 one bright line spectrum was suspected, a star of G. 5 magnitude 50' 

 north of C Orionis, aud this star, as well as /i, 6, aud € Orionis, is found 

 to have a variable spectrum. 



Among the peculiarities detected in stellar spectra may be noted the 

 iliscovery by Espin on August 13, 1888, of a bright line in the spectrum 

 of the variable star U Cygni; and as Duner found it in 1879-'82 of a weak 

 III type, an extraordinary change seems to have taken place. Espin's 

 bright line was apparently of a temporary character, and faded ra])idly. 



Motion of stars in the li)ie of sight. — The spectroscopic observations for 

 the determination of the motions of stars in the line of sigfht have been 

 continued at Greenwicli and at tlie Temple Observatory, Bugby, the 



