174 RIJPORTS ON INVESTIGATIONS AND PROJECTS. 



The difficult work of measuring and reducing the spectra, in many of 

 which the lines are exceedingly faint and ill-defined, has been carried on by 

 Mr. Adams, and Miss Lasby, Miss Waterman, and Miss Ensign, of the Com- 

 puting Division. At the present time at least one measurement of each plate 

 is available, and in most cases there are two or more. Among the results 

 obtained we may refer to the discovery of about fifty spectroscopic binaries ; 

 of seven stars in which the hydrogen lines are bright ; and of several stars, 

 among which is one of type A, having radial velocities of over lOO km. per 

 second. The application of the results to star-streams is referred to in con- 

 nection with Professor Kapteyn's investigations. 



Photographic Investigations of the Spectra of Globular Star-clusters 

 AND Spiral Nebula. 



During the year Mr. Path has obtained spectra of two spiral nebulae, N. G. 

 C. 3031 and 4736, with the low-dispersion spectrograph. The first of these 

 shows a well-defined K-type spectrum, and in this respect differs from most 

 spiral nebulae, which are of the G type. The photograph of N. G. C. 4736 

 shows a G-type spectrum, thus confirming the result obtained from a previ- 

 ous negative. Spectrograms of the three globular clusters N. G. C. 5904, 

 6093, and 6234 show all of these clusters to be of the F type, a result agree- 

 ing with that found for nine clusters during the previous year. 



This work upon spiral nebulae and star-clusters will be continued under 

 much more favorable conditions when the new cage for the 60-inch reflector 

 is available. In addition to the gain of light obtained by saving reflections 

 at two silvered surfaces, some changes will be made in the spectrograph itself 

 which will assist materially in the same direction. 



Professor Kapteyn's Investigations. 



The principal part of the work of Professor Kapteyn this year has been a 

 continuation of the investigation of the motions of the Orion stars. All of 

 the stars for which both the spectra and the proper-motions are known with 

 precision have now been included in the discussion. As a result of this addi- 

 tional material it now seems doubtful whether the conclusion arrived at last 

 year, that the Perseus and Scorpiiis-Centauriis groups might represent the 

 two great star-streams among the Orion stars, can be correct. In order to 

 settle the question, the best plan seemed to be to include in the investigation 

 the A stars, which, according to the generally accepted view at the present 

 time, represent the next step in the order of stellar evolution. The result of 

 this rather considerable extension of the work has been to show that the two 

 groups just mentioned do not represent the two great star-streams, but that 

 they must rather be considered as forming part of a single stream, in spite of 

 the fact that their directions of motion differ considerably. To this single 

 stream all, or nearly all, of the known Orion stars must belong. 



This fact might at first seem highly surprising, since, for the other spectral 

 types, the phenomenon of the two star-streams is so conspicuous a feature, 

 A discussion of the A stars, however, shows clearly how this might occur. 



