170 REPORTS ON INVESTIGATIONS AND PROJECTS. 



ferent state of affairs from that encountered by the meridian observers. 

 Consequently the program has constantly been in jeopardy. Some observa- 

 tions have been taken on bright moonlight nights, or before it was entirely 

 dark, more or less as an experiment. These observations will not be used 

 unless they accord well with the well-determined magnitudes. The indica- 

 tions thus far seem to indicate that the illumination of the sky has but very 

 little effect, as it seems to offset the star and the artificial light in the same 

 way. 



A rough comparison of the difference between two observations according 

 to the preliminary reductions shows a mean difference between two observa- 

 tions of o*f 16. The final reduction may decrease this. 



Mr. Meade L. Zimmer has continued in charge of the expedition. 



On November 19, 191 1, Mr. William Hunt, who had accompanied the 

 expedition to San Luis as assistant, was accidentally drowned. Not only 

 was his sudden death a great shock to us, but we felt that we had lost a very 

 promising astronomer. 



Mr. Heroy Jenkins sailed on January 4, 1912, to fill the position left 

 vacant by Mr. Hunt's death. 



From present indications it is probable that the photometric expedition 

 will terminate early in 1913. 



STUDIES UPON STELLAR MOTION. 



The investigations upon stellar motions have continued during the last 

 year. A group of stars moving at the high true velocity of about 80 km. per 

 second has been discovered (Astronomical Journal, 629, 633-634), moving 

 toward a convergent at right ascension = 99° 9,' declination = +o°5. 

 Other investigators have added members to this group. The group motion 

 is directed toward a point only about 7° distant from the vertex of preferen- 

 tial motion. The peculiarity of this group is that it contains stars from 

 every quarter of the sky. Most of the stars in this group belong to the later 

 types. 



A very interesting investigation (Astronomical Journal, 635-636) was 

 made of the proper motions of the stars arranged according to type. Some 

 of the most important results of this investigation are : 



(i) The tracing of group motion to the B-type stars. 



(2) The visible effects of preferential motion practically originate and 

 end in the A-type stars, accounting for the rapid acceleration of the motions 

 of the A stars which is not continued in later types. 



(3) In addition to the so-called preferential motion of Kapteyn, there are 

 other tendencies of motion of the stars. 



(4) With increase of galactic latitude there is an increase in the amount 

 of acceleration between groups of A stars representing the preferential 

 motions. 



