FebeuaEY 27, 1903.] 



SCIENCE. 



327 



locity of recession is not too great, these 

 stars thenceforth revolve around control- 

 ling centers, consisting of densely clustering 

 stars, in periods embracing many millions 

 of years. 



The attraction of a spherical mass of 

 stars, equivalent to 10,000,000 such suns as 

 ours, the aggregate extending to ten times 

 the assumed solar distance from the Gal- 

 axy, is sufficient to produce the present 

 solar velocity (20 km. per sec.) in moving 

 from rest at the outer limit, and to give 

 an oscillation from one extreme to the op- 

 posite boundary in a little over 40,000,000 

 years. With a central galactic condensa- 

 tion sufficient to turn the movement into 

 an eccentric orbital revolution, if apogalac- 

 teum is ten times as far away and peri- 

 galacteum one tenth as far from the center 

 of motion as the assiuned galactic distance, 

 the period of revolution will be shortened, 

 but can not be less than about 6,000,000 

 years for a circular orbit around a central 

 cluster. The general stellar sphere con- 

 trols the movement in an elongated orbit 

 at the greater distances, but the massive 

 central agglomerations exercise directive 

 power at the closer approach. 



There are certainly more than 10,000,000 

 stars. Hence, either their attractions are 

 largely mutually annulled through sym- 

 metrical external position, or else most of 

 the stars have masses very much less than 

 that of the sun, which miist be above the 

 average mass. 



As the true proper motions of the stars 

 show little preference for particular direc- 

 tions, the dispersals have occurred indis- 

 criminately in all directions. 



The diverse regions of space traversed 

 by the sun in its progression from peri- 

 galaeteum to apogalacteum may have very 

 different meteoric contents whose reception 

 produces secular changes in the planetary 

 atmospheres, and may influence the de- 

 velopment of living forms indirectly. 



The apex of the sim's way is now about 

 20° from the axis of the galactic stream. 

 At perigalacteum the apex will recede to 

 the galactic pole, and the direction of mo- 

 tion of the apex in the interim will deter- 

 mine the axis of the solar orbit. 



Preliminary Announcement with regard to 



the Proper Motions of Certain Faint 



Stars: Cteorge C. Comstock. 



The author has measured micrometrieally 

 the positions of 45 faint stars (ninth to 

 twelfth magnitudes) referred to brighter 

 neighboring stars whose proper motions 

 were accurately known. From a compari- 

 son of these observations with older data 

 of a similar kind, principally the measure- 

 ments made by the Struves, he has derived 

 proper motions of the faint stars, which in 

 respect of precision are quite comparable 

 with the proper motions of the fainter fun- 

 damental stars, e. g., those of the fifth and 

 sixth magTiitudes. 



These proper motions, although relatively 

 few in number, furnish a determination of 

 the sun's motion in space entirely independ- 

 ent of all previous data, and based upon 

 stars whose average distance from the solar 

 system is much greater than any hitherto 

 employed. The resulting solar motion is 

 in substantial agreement with previous de- 

 terminations, and when combined with 

 spectroscopic detei-minations of the velocity 

 of the sun's motion it furnishes as the mean 

 parallax of the stars observed (magnitude 

 10.5) the value 0".005 (40,000,000 radii of 

 the earth's orbit) which is in substantial 

 accord with the extrapolated value fur- 

 nished by Kapteyn's researches upon the 

 brighter stars. 



Other results of the present investiga- 

 tion are: (1) That the proper motions of 

 the fainter half of this list of stars do not 

 seem to be materially less than those of the 

 brighter half, i. e., the eleventh and twelfth 

 magnitude stars are not more distant than 



