MERIDIAN ASTROMETRY — BOSS. 209 



nishing of material for construction of the Preliminary General Catalog is 

 of an importance which can scarcely be overestimated. Without the Cape 

 results the Catalog would have been very imperfect for all that part of the 

 sky that is south of — 36°. As it is now there will be no blanks in the 

 columns for proper motion. For every star of more than 6,000 to be included 

 in the Preliminary General Catalog it is now possible to compute a value of 

 its motion that will be a fair approximation to the truth, while the Catalog 

 will also furnish, m nearly every instance, reliable values of right ascension 

 and declination for 1900, with trustworthy means of bringing the positions 

 forward for several years to come. While the primary object of this Catalog 

 is to furnish computed motions that shall be as free as possible from sys- 

 tematic error, it seems probable that it will prove of considerable immediate 

 use to practical astronomers who, for any reason, have occasion to desire 

 accurate positions of the brighter stars at the present time. To illustrate 

 this use, it may be mentioned that the positions for 202 stars have been fur- 

 nished since the date of my last report to the United States Coast and Geo- 

 detic Survey for use in determination of latitudes. Several other requests 

 for data concerning the motions of stars have also been received. 



In accord with the estimate contained in my last report, it seems proba- 

 ble that the Preliminary General Catalog can be made ready for publica- 

 tion during the coming winter of 1906-7. The necessary computations 

 should easily be completed before the close of the present year. The 

 checks and scrutiny required, insuring accuracy in combination of results 

 to produce the numbers to be printed in the catalog, will occupy an amount 

 of time that can not be very safely predicted, especially when the duties 

 of the staff upon other operations in the main program are considered. 

 But it seems highly probable that the complete manuscript for the catalog 

 can be prepared within the period already mentioned. 



During the observational activity of the past year there have developed 

 two points that have an important bearing upon an estimate of the proba- 

 ble quality of our current and future work of observation. 



In the report of last year I called attention to two essential prerequisites 

 for the successful combination of observations to be made in two hemi- 

 spheres with the same instrument. One is that the error of graduation 

 should be well investigated. The measurements to determine the errors of 

 the new graduations of our meridian circle were completed a year ago, as 

 described in the report of last year. A few months later the definitive 

 computations were completed, and the results are available in a table of 

 corrections giving, at intervals of 10' for each circle, the observed correc- 

 tions to bs applied to the mean reading of four microscopes, in order to free 

 that mean from the small error of graduation. Usually such determina- 

 tions are carried to degrees only, sometimes to intervals of five degrees 



14 — YB 



