DEPARTMENT OF MERIDIAN ASTROMETRY. 12$ 



fairly approximate idea of the extent to which his conchtsions may be 

 affected by the errors arising from observation alone. There can scarcely 

 be two opinions as to the very decided value of such information in nearly 

 all researches for which the Catalog is likely to be employed. 



Very great care has been exercised to eliminate as far as possible the mis- 

 takes, large and sm.all, that are liable to creep into a work of this kind, where 

 the numbers are collated or formed from many separate series of papers in 

 the original details of computations. The greater part of the energies of 

 the working staff during the last three or four months has been expended in 

 the endeavor to secure, so far as may be, immunity from these possible errors 

 of compilation. All the data for the General Catalog of every name and 

 nature are now collected in a systematic manner upon the catalog-cards and 

 the numbers have all been subjected to repeated examination and tests. 

 From these cards the printer's sheets are to be copied, and that work is now 

 in progress. At its conclusion, in the near future, it is proposed to submit 

 the Preliminary General Catalog for publication. 



The formation of the definitive catalog, with its unusually precise values 

 of proper-motion, based upon observations from which the systematic errors 

 to an important extent have been eliminated, offers favorable opportunity 

 for the prosecution of a number of related investigations. Advantage has 

 been taken of this fact to some extent already, and efforts in this direction 

 are likely to continue for some time in the future. 



As a supplementary work of this kind the systematic errors and weights 

 of all the star-catalogs produced under the plan of the Astronomische Gesell- 

 schaft have been investigated with care. The Preliminary General Catalog 

 affords a very effective means for ascertaining these corrections and weights 

 with a fair degree of precision, so far as stars brighter than eighth magni- 

 tude are concerned. With any less extensive and efficient medium of com- 

 parison it would not have been practicable to ascertain the systematic correc- 

 tions for these narrow zones with a satisfactory degree of precision. As the 

 matter now stands a very large mass of valuable observations contained in 

 the Gesellschaft zones and elsewhere has now, for the first time, become 

 really available for use in researches of precision. The results, in condensed 

 form for practical use, will be presented in the introduction to the Catalog. 



Certain questions relating to stellar motions have already been tested here 

 since the catalog-cards have been completed. For the vast majority of stars 

 it may be assumed, with sufficient accuracy, that their motions are upon great 

 circles of the sphere with uniform velocity. But in the case of binary stars 

 this assumption may, and sometimes does, so far depart from the truth as 

 to require sensible correction on account of orbital motion, not only for the 

 fainter but also for the brighter star. In order to make this correction in a 

 given instance it is necessary to have precise knowledge both of the orbital 

 elements and of the relative masses of the components of the double star in 



