ADVISORY committee; ON ASTRONOMY 1 27 



systematic errors — errors which, though they are not important in 

 the determination of the motion of one star, are vital when masses 

 of motions are treated to determine the general drift of stars. To 

 arrive as closely as possible to freedom from systematic error, we 

 must multiply fundamental determinations of position. 



For the study of the mechanism of the sidereal universe we need 

 to know the motions of the stars upon the basis of all the observations 

 which have been made, correcting these, so far as possible, for their 

 systematic errors. Then we shall be able to arrive at a better de- 

 termination of the solar motion than has been thought of up to the 

 present time, and we shall develop new ideas as to the drift of stars 

 in various regions of sky. 



This research, associated with determination of stellar parallax 

 and with the measurement of motion in the line of sight, makes a 

 strong combination for solving the problems that concern the distri- 

 bution of the brighter stars in space which is relatively near to the 

 solar system. 



Determination of more accurate constants of aberration and pre- 

 cession are so interwoven with this problem that they must be con- 

 sidered an integral part of it. The same, in a modified degree, is 

 true of the measurements of variation of latitude. 



Without prejudice to other important lines of astronomical re- 

 search, these investigations seem to offer a peculiarly favorable 

 opportunity for concerted effort toward a highly important end to 

 be pursued for several years to come. With the aid which the Car- 

 negie Institution might be able to render, this program could be 

 pushed forward with great certainty to a successful stage of devel- 

 opment. This programme offers the advantage of a distinct pur- 

 pose toward which many lines of research converge, each important 

 in itself and all deriving greater importance from their intimate 

 association. 



Respectfully submitted. 



Lewis Boss. 



