MOUNT WILSON SOLAR OBSERVATORY. 289 



(27) The equatorial velocities show a progressive increase with inten- 

 sity of the lines; groups of mean intensities 1.0, 2.0, 3.6, 6.5, and 22 

 give rotation values of 1.924, 1.933, 1.937, 1.954, and 2.043 km., 

 respectively; 6 enhanced lines of mean intensity 3.2 give 1.928 km., 

 while 5 unenhanced Unes of mean intensity 3.6 give 1.937 km. The 

 relative values for lines of increasing intensities, and for enhanced and 

 unenhanced lines, are in agreement with the results of two earlier 

 investigations. 



(28) Additional long-exposure photographs of various nebulse have 

 been obtained during the year. 



(29) An extensive report on the interpretation of nebulse has been 

 prepared by Professor Chamberlin, which will be of great service in 

 planning further work on these objects. 



(30) Photographic parallax determinations, having a mean probable 

 error of 0T0055, have been completed for 17 stars. 



(31) First-epoch photographs have been secured for 66 stars having 

 proper motions exceeding 0T50, for the purpose of detecting com- 

 panions. 



(32) From the parallactic motions of 55 N stars and 35 stars the 

 mean parallaxes for these two types have been found to be 0T0022 and 

 0''005, respectively. 



(33) The investigation of standard polar magnitudes has been com- 

 pleted. 617 photographic and 339 photovisual magnitudes are now 

 available. The limits for the two scales are 20.1 and 17.5, respectively. 



(34) A detailed comparison of the Harvard and Mount Wilson inves- 

 tigations reveals the source of the discordance for the faint stars, and 

 materially reduces that for the brighter objects. 



(35) The work of determining scales of photographic magnitude in 

 the Kapteyn Selected Areas stands as follows: The observational pro- 

 gram is three-fourths finished, one-third of the measures are complete, 

 and relative magnitudes are available for 22 areas. Intercomparisons 

 for reduction to the international zero-point have been begun. 



(36) Coordinates and diameters have been derived under Professor 

 Kapteyn's direction in Groningen for the stars in 107 of the Selected 

 Areas. The measures are now being reduced to the absolute scale 

 by means of the standard magnitudes whose derivation forms a part 

 of the current photometric program. 



(37) A catalogue of the magnitudes and colors of more than a 

 thousand stars in the globular cluster Messier 13 has been completed 

 and a similar catalogue of magnitudes and colors of 300 stars has been 

 made for the open cluster Messier 67. 



(38) Nearly 11 per cent of the Messier 13 stars have negative color 

 indices, suggesting that in this direction there is no marked absorption 

 of light in space. 



(39) The average color mdex increases in a remarkable manner 

 toward the center of the cluster, averaging less than -1-0.6 mag. up to 



