246 



CARNEGIE INSTITUTION OF WASHINGTON. 



motions of the nebulous points relatively to the stars for the proper 

 motion of the nebula, which was found to be +0''005 and — 0''013, 

 the residuals gave strong evidence of internal motion. The values 

 for individual points were resolved into components parallel to and 

 perpendicular to the radius vector connecting them with the center; 

 78 rotational components are left-handed and 9 right-handed; 58 

 appear to be moving outward and 28 inward. The mean annual 

 components are 0''022 left-handed for the rotation, at a point 5' from 

 the center, and 0''007 outward for the radial motion. The mean 

 resultant motion deviates but a few degrees from the direction of the 

 branches of the spirals. Interpreted as a motion of rotation, the period 

 would be about 85,000 years. 



An improved proper motion was derived for the double cluster h 

 and X Persei with the aid of 25 cluster stars whose common radial 

 velocity, as determined with the Cassegrain spectrograph, is about 

 — 40 km. per second. The resulting proper motion of the cluster is 

 exceedingly small, namely, +0''003 in both right ascension and dec- 

 lination. 



STELLAR PHOTOMETRY. 



The observational part of the investigations in stellar photometry 

 by Mr. Scares and Mr. Shapley includes 767 photographs, all made 

 with the 60-inch reflector and distributed as follows : 



Selected Areas 314 Color photograhs of neliulae. ... 45 



Clusters 99 Color photographs of stars 181 



Variable stars 98 Miscellaneous 30 



Photographic Magnitudes for the Selected Areas. 



The observational part of this investigation, which is in the hands of 

 Mr. Scares, is now approaching completion. The program for the 

 determination of relative magnitudes on an absolute scale has been 

 described in previous reports. As indicated by the first three columns 

 of the accompanying table, only 30 of the magnitude-scale plates are 

 still to be obtained. Most of the photographs required for the reduc- 

 tion of the relative magnitudes to a unifonn zero-point have also been 

 secured. These consist of two groups, one a series of zonal intercom- 



