150 REPORTS ON INVESTIGATIONS AND PROJECTS. 



standard stars for 1910" was prepared by me, was published by the Dudley 

 Observatory, and a few copies were circulated in January 1910. This list 

 of standard stars is the result of a careful selection from a much larger list 

 of standard stars which we have been using in observations with our 

 meridian-circle, both at Albany and San Luis. In giving the positions and 

 motions for 1910, we have used the Preliminary General Catalogue for 1900 

 as the basis. The object was to prepare a larger list of the standard stars 

 homogeneous in character, which can most rapidly and economically be per- 

 fected by further observation. Nearly all of these south of — 20° have 

 already been observed at least 12 times at San Luis. In making these selec- 

 tions the requirements of safe prediction have been specially regarded. 



STUDIES UPON STELLAR MOTION. 



The position of the apex of solar motion, the general parallactic drift of 

 the stars, the probable value of the precession, and the probable amount of 

 the motion of the equinox are all problems concerned in the apparent system- 

 atic motions of the stars. These had first to be considered and eliminated 

 before we could proceed to a closer study of special forms of systematic 

 drift should such exist. 



In my report for 1909 I gave an outline of the results of our studies upon 

 the general systematic motions, or drift. These points have been subjected 

 to further examination, analysis, and extension during the past year, and an 

 outline of processes employed and of results attained have been published in 

 Nos. 612 and 614 of the Astronomical Journal. The preliminary result has 

 been reached that the general systematic motions of the stars, as we find 

 them to be in our Preliminary General Catalogue, are not inconsistent with 

 the hypothesis of random motion of the individual stars, or at least with a 

 symmetrical distribution of the motions around a conventional origin. 



In the course of discussion, however, it was found that the mean of ap- 

 parent stellar motions distinctly varies with distance from the Galactic plane, 

 and increases decidedly with Galactic latitude. This result completely estab- 

 lishes the results of previous researches of a less comprehensive scope. 



It is also shown (Ast. Jour., 614, p. 122) that the parallactic drift in the 

 plane of the Galaxy is probably greater, in proportion to the mean motion of 

 the stars therein, than it is in the higher Galactic latitudes. One explana- 

 tion of this phenomenon was naturally suggested at once. The mean mo- 

 tions peculiar to the stars themselves, for a part of those in the vicinity of 

 the plane of the Milky Way (Galaxy), might be smaller in linear velocity 

 than those in the higher Galactic latitudes. It was, in fact, pointed out, 

 some eight years ago, by Professor Frost (Publ. Yerkes Observatory, vol. 11, 

 Radial Velocities of Twenty Stars, p. 105) that the radial velocities of 20 

 stars of the Orion type are in the mean only 7.0 km. This is much less than 

 half of the means for all types. Additional testimony to the same effect has 

 accumulated since. Our Catalogue contains 525 stars of the Orion type 



