242 POOR 



20. Comparison Stars. — The positions of the comparison stars 

 were carefully redetermined by S. Alfred Mitchell while at the 

 Yerkes Observatory. This work was carried out in a most 

 thorough and painstaking manner, entailing a great amount of 

 labor, as some 508 stars were determined. The positions were 

 taken from the various catalogues in the Naval Observatory, the 

 Johns Hopkins University, and the Yerkes Observatory, in all 

 some 65 catalogues being used. For each star the annual pre- 

 cession and the secular variation were computed, using the con- 

 stants of Struve and Peters, and each catalogue position was 

 brought up to 1900.0. 



The systematic corrections to each catalogue, as determined 

 by Newcomb,^ were applied and the weighted mean of the results 

 taken. Wherever the catalogue places indicated proper motion, 

 the tabular results were solved by the method of least squares 

 and a definite determination of the proper motion made. The 

 proper motions of some 70 stars were thus obtained. 



Besides the various catalogues many numbers of the A.N. 

 and the A.J. w^ere consulted for meridian observations of the 

 fainter stars. Full use was also made of the published researches 

 of Bauschinger which appeared while this portion of my work 

 was nearing completion. These researches contained the posi- 

 tions of many stars which had been reobserved by Bauschinger 

 himself, and such positions were of the greatest value. In fact, 

 Bauschinger's investigations are so complete and satisfactory as 

 to make mine all but superfluous. My work was so far advanced, 

 however, that it seemed advisable to complete it, and to avail 

 myself of the data which appeared so opportunely. 



21. Bauschinger's star places were reduced to the system of 

 the Astronomische Gesellschaft ; mine, as I have already stated, 

 to that of Newcomb. There will, therefore, be a systematic 

 difference in our determination of the star places, and this syste- 

 matic difference will be represented by the corrections to be ap- 

 plied to reduce Newcomb to A.G.C., and are as follows : 



' Papers of the American Epheineris, Vol. VIII, Part II. 



