ASTRONOMY — BOSS. 79 



for each star for which this work had not been previously accom- 

 plished. The comparison of observation with preliminary prediction 

 had been completed for all except a few of the less well-determined 

 star positions. During the year the equations have been formed and 

 solved for about 1,500 stars in addition to what had been accom- 

 plished in previous years. All that remains to be done in these lines 

 could be accomplished within four or five months if the entire force 

 were to be concentrated upon that task ; but it will be desirable to 

 expend a large share of our potential upon the obserx^ations, leaving a 

 safe margin for the completion of the Preliminary General Catalogue 

 during 1906. 



Work on the catalogue has been pushed forward, especially in the 

 laborious revision of the systematic corrections applied to the several 

 catalogues of observations. Great improvements in these correc- 

 tions have been effected for the most extensive and important cata- 

 logues, though these present no material deviations from the results 

 given in the Catalogue of 627 Principal vStandard Stars, published 

 in the Astronomical Journal two years ago. Much attention has 

 been given to the determinations of corrections on account of 

 " magnitude equation." The result is that we may consider this a 

 problem substantially solved, in the sense that we are able to apply 

 to the mean results for right ascension by the various observers of 

 the nineteenth century the corrections which those observations 

 require on account of the habit of the observer varying with the 

 brightness of the star observed. The importance of this correction 

 in relation to the study of sj'stematic motion in the stellar system is 

 fundamental. A great variety of special problems in relation to the 

 systematic corrections required by the several catalogues of obser- 

 vation has been met and substantially solved, so that the completion 

 of the work involves little more than routine operations, the extent 

 of which can be accurately foreseen. Delays have intervened in the 

 prosecution of this work. 



The first delay in the work was caused when it was deemed advis- 

 able to renew the circle-graduations, and to push the determination 

 of the errors to speedy completion, as a basis of all subsequent meas- 

 urement in zenith distance according to our somewhat extensive 

 program. A second and more effective cause of delay arose from 

 the voluntary and high-spirited offer of Sir David Gill, Astronomer 

 Royal at the Cape of Good Hope, to redetermine the positions of all 

 the stars of our catalogue that are south of — 33° of declination, some 

 1,200 in number, and to have the results of these determinations 

 ready for me within a year from the time of beginning the observa- 



