Deoeubeb 16, 1910] 



SCIENCE 



875 



son, Metcalf, Milham, D. C. Miller, S. A. Mitchell, 

 Newall, Parkhurst, Peirce, Peters, E. C. Pickering, 

 W. H. Pickering, Plaskett, J. M. Poor, Prings- 

 heim, Ricco, Roe, Rotch, Russell, Rydberg, 

 Schwarzschild, Schlesinger, Skinner, Stebbins, 

 Stetson, Turner, Updegraff, Upton, Very, Wendell, 

 Whitman, Willson, Wolfer and W. L. Wright. 



The following persons were elected to member- 

 ship: Miss Leah Brown Allen, Wellegley, Mass.; 

 Professor A. T. C. Apple, Lancaster, Pa.; Father 

 Peter Archer, S.J., Georgetown University; Dr. 

 Oskar Backlund, Pulkowa, Russia; Miss Louise 

 Brown, Wellesley, Mass.; Professor Robert E. 

 Bruce, Boston University; Mr. A. J. Champreux, 

 Berkeley, Cal.; Professor Wilbur A. Coit, Acadia 

 University, Wolfville, N. S. ; Professor A. E. 

 Douglass, University of Arizona; Dr. J. C. Dun- 

 can, Harvard University; Mr. F. W. Dyson, Royal 

 Observatory, Greenwich, England; Mr. Sturla 

 Einarsson, Berkeley, Cal.; Mr. Charles Grosjean, 

 Omaha, Nebraska; Miss Margaret Harwood, Lit- 

 tleton, Mass. ; Miss Ellen Hayes, Wellesley, Mass. ; 

 Professor Josef v. Hepperger, Vienna, Austria; 

 Mr. Charles John Hudson, Clinton, Mass.; Miss 

 Jennie B. Lasby, Pasadena, Cal.; Mr. C. A. Robert 

 Lundin, Jr., Canibridgeport, Mass. ; Mr. P. G. 

 Nutting, Washington, D. C; Mr. W. F. Meyer, 

 Berkeley, Cal.; Professor W. I. Milham, Williams- 

 town, Mass. ; IMiss Mary Proctor, New York City ; 

 Mr. R. F. Sanford, Mt. Hamilton, Cal.; Professor 

 Karl Schwarzschild, Potsdam, Germany; Mr. 

 Elihu Thomson, Swampscott, Mass.; Professor H. 

 H. Turner, Oxford, England; Mr. Percy F. Whis- 

 ler, Urbana, 111. It will be noticed that this list 

 contains the names of several foreign astronomers, 

 a gratifying innovation that is likely to prove of 

 considerable importance to the society. 



Most of the sessions were as usual devoted to 

 the reading and discussion of papers, but time was 

 found for several pleasant and instructive excur- 

 sions to points of scientific interest in the vicinity 

 of Cambridge; thus on the afternoon of the seven- 

 teenth a visit was paid to the meteorological ob- 

 servatory at Blue Hill, where Director Rotch ex- 

 hibited the equipment and explained the work of 

 the institution. On the afternoon of the eight- 

 eenth the society went in a body to the Whitin 

 Observatory of Wellesley College and on the nine- 

 teenth to the Students' Observ-atory of Harvard 

 College; these two visits were of particular in- 

 terest to those who are engaged in teaching, as 

 Professor Willson and Miss Whiting, who are in 

 charge of these observatories, have highly devel- 

 oped the " laboratory method " in astronomy. In 



addition ample opportunity was given to the mem- 

 bers to examine the equipment of Harvard Ob- 

 servatory itself, and for this purpose the whole 

 staff of the observatory very kindly put their time 

 at the disposal of the visitors. 



The following papers and reports were read at 

 the various sessions: 

 Some Preliminary Results deduced from Observed 



Radial Velocities of Stars: W. W. Campbell. 



(Read by Mr. Plaskett.) 



From the radial velocities of more than one 

 thousand stars, observed for the most part at the 

 Lick Observatory and at its southern station in 

 Chile, the following results were obtained for the 

 location of the apex of the sun's way: 

 Right ascension, 272°.0 ± 2°.5. 

 Declination + 27°.5 ± 3°.0. 

 Velocity of the sun in space, 17.77 km. 



The last is somewhat smaller than was expected 

 in view of the author's earlier value from 280 

 stars and that of Hough and Halm. The data 

 could, however, not be made to yield a sensibly 

 greater value; 330 stars of spectral types 0, B, A 

 and F (up to F4) yielded 17.69 km., while 704 

 stars of types F5 to G, K and M gave 17.96. 



The stars were tabulated with regard to spec- 

 tral types and it was found that their velocities 

 increase as the type advances, those of B type 

 having an average velocity of 9.0 km.; A type, 

 10 km.; F, 14 km.; G and K, 15 km., and M, 

 16.5 km. 



A study of 280 velocities made by the author 

 in 1900 had indicated a progressive decrease in 

 velocity with increasing brightness; a similar 

 study of the fourfold more extensive material now 

 at hand does not confirm the earlier result, which 

 seems to have been due to the larger proportion 

 of first-tj'pe spectra in the earlier data. 



The author showed that Kapteyn's discovery of 

 systematic drifting, deduced from the study of 

 proper motions, was clearly and strongly con- 

 firmed by the radial velocities. Stars in the 

 neighborhood of Kapteyn's vertex and antivertes 

 appear to have velocities about 33 per cent, greater 

 than stars that are about 90° from these points. 



A study of radial velocity in connection with 

 proper motions indicates that stars of different 

 spectral types and likewise of different magni- 

 tudes are more thoroughly mixed, that is more 

 nearly equal in distance, than has previously been 

 supposed; and that the brighter stars, down to 

 the fifth magnitude, are nearer to us than the 

 formula; for mean parallaxes would place them. 



