260 



CARNEGIE INSTITUTION OF WASHINGTON. 



STELLAR PHOTOMETRY. 



The observational part of the investigations in stellar photometry 

 by Mr. Seares and Mr. Shapley includes 614 photographs, all made 

 with the 60-inch reflector and distributed as follows: 



RS Bootis 91 



XZ Cygni 44 



XX Cygni 58 



S Cygni 18 



X Cephei 19 



R Piscium 28 



N. G. C. 1647 11 



N. P., faint stars 12 



N. P., bright stars 229 



Selected Areas 88 



Miscellaneous 16 



Magnitudes of Polar Stars. 



The investigation of the magnitudes of stars near the Pole, including 

 those of the North Polar Sequence, is now nearing completion. The 

 photographic scale has been established from the second to the twen- 

 tieth magnitude, and results for about 600 stars have been derived. 

 From the eleventh magnitude downward, two series of plates, taken 

 mostly with diaphragms and screens, were available; one with a maxi- 

 mum exposure of 11" and a limiting magnitude of 17.8, the other with 

 exposures ranging from 30"" to 5'', and a limiting magnitude of about 

 20.1 (International Scale). About 3,000 magnitudes were obtained 

 for the 66 stars appearing on both series. The numerous individual 

 values greatly facilitated the discussion of the results for systematic 

 errors and permitted, for the first time, a satisfactory determination of 

 the distance correction for very faint stars and an evaluation of the 

 irregularities affecting the glass scale used for the measurement of the 

 images. Each series of plates gave several independent determinations 

 of the magnitude scale, and the agreement of the mean scales for long 

 and short exposure is indicated by the second column of the accom- 

 panying table. 



A comparison of the mean scale for the two series with that of Harvard 

 Circular No. 170 is given in the last column. The result for the 



