210 CARNEGIE INSTITUTION OF WASHINGTON. 



These include both the relatively bright stars of the American Ephe- 

 meris and the catalogue of Boss, and the faint stars of large proper 

 motion, most of which are of intrinsically low luminosity. The pub- 

 lication of a list of 50 stars with parallaxes measured by Schlesinger, 

 and the additions to the number of trigonometrically determined par- 

 allaxes made by van Maanen and others, have aided in the caUbration 

 tion of the curves used in the spectroscopic reductions. 



A material change has been made in the method of determination 

 of the absolute magnitudes of the Cepheid variables. A study of the 

 spectra of this class of stars, to which reference will be made presently, 

 has shown that the intensities of the enhanced lines are quite abnormal 

 for stars of this spectral type and that many other characteristics are 

 peculiar. Accordingly the reduction formulae employed in the case 

 of stars of a less-advanced type of spectrum, in which the enhanced 

 lines are prominent, have been tried for stars of the Cepheid class 

 and appear to give consistent results. The general effect of this change 

 is to make the absolute magnitude of these stars somewhat brighter 

 than those obtained previously. 



A computation of the absolute motions in space of about 1,000 stars 

 with magnitudes determined by the spectroscopic method is now in 

 progress. By a statistical treatment of this large amount of material, 

 using the radial velocities, proper motions, and, so far as possible, the 

 trigonometric parallaxes, it is hoped that several criteria will be 

 obtained for further tests of the accuracy of the spectroscopic deter- 

 minations. 



Nova Aqthl^ No. 3. 



The independent discovery of this star by Mr. Joy on the night of 

 June 8 and the prevalence of favorable weather made it possible to 

 secure an extended series of observations of its spectrum from a very 

 early stage. With the exception of June 18 and 30, photographs were 

 made on every night between June 8 and July 1, and previous to Sep- 

 tember 1 a total of 176 negatives had been obtained. A considerable 

 number of these cover the less refrangible region of the spectrum 

 between Hj3 and Ha. 



The measurement and reduction of the photographs is still in 

 progress and reference can be made to only a very few of the results. 



1. Probably the most interesting feature of the spectrum is the 

 appearance on June 10 of a large number of fairly narrow and 

 well-defined dark lines. At first it did not seem possible to identify 

 these lines, but on comparison with a photograph of the spectrum of 

 a Cygni (a star with extraordinarily prominent enhanced lines) it was 

 found that nearly all of them were present in both spectra. The ele- 

 ments represented include iron, titanium, chromium, strontium, and 

 some others. Only the strongest of the arc lines appear, and these but 

 faintly. About 100 lines in the region between X 4000 and H/3 have 

 been identified with certainty. 



