174 CARNEGIE INSTITUTION OF WASHINGTON. 



Judging from the rapid developments of the last decade, it is ex- 

 tremely risky to predict the exact needs of the future, and therefore 

 it seems advisable to plan a program which will be at the same time 

 comprehensive and feasible. The General Catalogue will furnish 

 proper-motions of stars to the seventh magnitude. It is eminently 

 desirable to provide for proper-motions of fainter stars; the larger 

 the range of magnitude the more comprehensive the study of stellar 

 motions. As each step toward fainter magnitudes immensely 

 increases the number of stars involved, it is out of the question to deter- 

 mine the proper-motions of all the stars of any particular magnitude 

 unless we limit the study to the brighter stars. It is therefore proposed 

 to form a selected list of stars from each magnitude and to extend the 

 range of magnitude as far as possible, the size of the list being regu- 

 lated partly by present requirements and partly by our ability to 

 handle it. Thus the program is flexible and can be adjusted to meet 

 the actual conditions encountered. 



The method of attack is dictated by past experience. Since no 

 means have been devised whereby absolute positions of stars can be 

 determined photographically, it becomes necessary to base the photo- 

 graphic measures upon meridian observations. For this purpose it is 

 proposed to observe a list of comparison stars, approximately one to 

 each square degree, with a meridian-circle instrument, the meridian 

 observations to be taken simultaneously with the photographic pro- 

 gram. It is further intended to observe in broad zones, which facili- 

 tates the formation of a homogeneous system. Two photographic 

 telescopes will be required to cover the range in magnitudes desired. 

 They should be designed to photograph a large field. It is proposed 

 to cover the entire sky for the brighter stars, and for fainter stars 

 many selected areas will be taken, with special attention devoted to 

 the Galaxy. 



While the positions of only a portion of the stars will be measured, 

 there will be a permanent record of the sky as it appears to-day avail- 

 able at any time for anyone interested in a particular region or in some 

 new problem requiring additional stars. A repetition of this program 

 at intervals in the future will lay the foundations for an exhaustive 

 study of the motions of the stars. 



INVESTIGATIONS IN PROGRESS. 



STELLAR PARALLAXES. 



In order to pursue the study of the real motions of the stars in space 

 it becomes necessary to systematize, as far as possible, the results of 

 the various stellar-parallax observers, since in many cases a number of 

 determinations have been made of the parallax of an individual star. 



An important question which must be disposed of first of all is that 

 of the parallax of the comparison stars used by the observer. For 



