158 REPORTS ON INVESTIGATIONS AND PROJECTS. 



(19) Measurements of the photographs of the spectrum of the spark 

 under pressure indicate that at the same pressure the enhanced lines are dis- 

 placed considerably more than the great majority of the arc lines. 



References will be made to numerous other investigations in the course of 

 the discussion of the work now in progress. 



One of the most important of the researches of the past year, particularly 

 in its wide bearing on the future work of the 60-inch reflector, has been that 

 of Professor Kapteyn on the systematic motions of groups of stars. Per- 

 haps the greatest difficulty in the construction of an outline of work for a 

 large telescope is that of coordinating the various kinds of observations and 

 making them so far as possible lead toward the same end. By his discovery 

 of a common motion among stars of certain groups. Professor Kapteyn has 

 given to the study of the radial velocities of the fainter stars a definiteness 

 of purpose which is perhaps commensurable in importance with the value of 

 the discovery itself. 



STAFF. 



There have been few changes in the staff of the Observatory during the 

 past year. Mr. Adams has served as Acting Director during the absence of 

 the Director, and has been engaged in the organization of the stellar spectro- 

 scopic work. Prof. F. H. Scares has continued as superintendent of the 

 computing division throughout the year and has had editorial charge of the 

 Observatory publications. He has also carried on certain photometric in- 

 vestigations with the 60-inch reflector. Dr. Arthur S. King has remained in 

 charge of the physical laboratory. Prof. G. W. Ritchey has continued to 

 devote a part of his time to the design of the 100-inch reflecting telescope, 

 and part to direct photography with the 60-inch reflector. Prof. C. E. St. 

 John has been engaged in an investigation of the motion of the calcium 

 vapor in the sun's atmosphere and in a study of the radial motion in sun-spots. 

 Mr. Ferdinand Ellerman has continued the observations with the spectro- 

 heliographs of the Snow and tower telescopes, and has also taken numerous 

 photographs of spectra with the tower telescope. Mr. H. D. Babcock has 

 divided his time between spectroscopic work in the Pasadena laboratory and 

 photography of stellar spectra with the 60-inch reflector. He has also taken 

 many spectra of sun-spots with especial reference to the determination of the 

 direction of polarization of the spectrum-lines. Dr. E. A. Fath has been 

 engaged in photographing the spectra of certain spiral nebulse and star- 

 clusters, and has also secured photographs of some of the Kapteyn selected 

 areas. Dr. C. M. Olmstead resigned from the staff in October 1910. 



Prof. J. C. Kapteyn, of the University of Groningen, Research Associate 

 of the Carnegie Institution of Washington, has been at the Observatory 

 since July, engaged in making certain statistical studies of star-groups, and 

 in planning a considerable part of the work of the 60-inch reflector. Dr. 

 H. G. Gale, of the University of Chicago, Research Associate of the Car- 

 negie Institution of Washington, spent the months of April, May, and June 



