March 23, 1906.] 



SCIENCE. 



447 



Results for the photographic wedge were 

 derived from five observations upon each 

 pair, measured on three nights. The re- 

 sults are: P.E. of a single observation of 

 four comparisons, ± 0.078 mag. ; average 

 deviation from the Miiller and Kempf mag- 

 nitude diif erenee, 0.12 mag. ; scale differ- 

 ence, — 0.073 mag. The two scales can 

 be brought into agreement by multiplying 

 the ordinates of the absorption curve of the 

 photographic wedge by the factor 0.961. 



The photographic wedge has been dis- 

 carded in favor of that of shade glass. 



Details of the investigation are to be 

 found in Laws Observatory Bulletin No. 7. 



Some Peculiar Spectra: Mrs. W. P. Flem- 

 ing. 



The examination of stellar spectrum pho- 

 tographs at Harvard College Observatory, 

 forming part of the work of the Henry 

 Draper Memorial, has enabled us to follow 

 new stars until they became gaseous nebulae, 

 too faint for observation. Since we can 

 pass from gaseous nebula to stars of class 

 0, or type V., in which characteristic bright 

 lines extend from wave-length 4600 to 4800, 

 thence to stars having several hydrogen 

 lines bright with dark lines of helium also 

 present, and from the latter through classes 

 B, A, F, G, K and M, we may assume that 

 we have a key to the formation of the 

 stellar universe. 



In putting together results from an ex- 

 amination of variable stars whose spectra 

 are of class Md it was found that a few 

 stars were assigned to several subdivisions 

 extending from Md 1 to Md 10, the most 

 marked case being 8 Carinae. Further 

 examination showed actual changes in the 

 spectrum, which probably (as in the case 

 of /? Lyra) follow closely the variations in 

 light. B. Scuti also shows changes, and 

 quite recently B Cygni, another long period 

 variable, has been added to this list. 

 The spectrum of the star (now known 



to be a gaseous nebula) — 12° 1172, mag. 

 9.2, when found on Harvard photographs, 

 has always led to an examination of the 

 list of novffi before that of nebulae, since in 

 this spectrum the bright nebular lines at 

 wave-lengths 5003 and 5007 are quite faint, 

 the hydrogen lines, H|, He, H8, Hy, and 

 H^ are bright and of normal intensity, 

 while the most marked feature is the broad 

 bright line at wave-length 3724. This is 

 not generally well defined in photographic 

 spectra of gaseous nebulas, in which the 

 strong line in the violet end is 3868, of 

 slightly shorter wave-length than H|. 



The star Z.C. 18'' 1935, mag. 9, shows a 

 peculiar form of spectrum not yet assigned 

 to its class. The continuous spectrum con- 

 tains strong, dark bands of which the most 

 marked extend from 4650 to 4710. This 

 agrees closely with the strong character- 

 istic bright line in spectra of the fifth type. 

 A few other stars with similar spectra have 

 been announced in Harvard Circulars. The 

 variable star— Crwcis, R.A. = 12'^ 50°>.7, 

 Dec. = — 57°21' (1900), has a spectrum 

 similar to that of Z.C. ISi^ 1935, but in it 

 the hydrogen lines Hy and H/i are bright, 

 as in variables of the earlier subdivisions 

 of class Md. 



No other spectrum has yet been found 

 on these photographs like that of ir' Grids, 

 but that of B Cygni, as photographed on 

 December 2, 1890, bears a closer resem- 

 blance to it than any other spectrum yet 

 photographed here. 



Burnham's Forthcoming General Catalogue 

 of JDoiihle Stars: Edwin B. Frost. 

 With Professor Burnham's permission a 

 brief statement is made here regarding 

 this important undertaking, the basis for 

 which has existed in manuscript for many 

 years. A grant from the Carnegie Insti- 

 tution in 1903 made publication possible, 

 and rather more than four fifths of the 

 work has now been set up and eleetrotyped. 



