156 



SCIENCE 



[X. S. Vol. XXXII. Xo. 813 



more than sis thousand stars, about one third 

 of which are of telescopic faintness, while the 

 remaining two thirds constitute by far the 

 larger part of all stars visible to the unaided 

 eye. The purpose realized in these pages is set 

 forth substantially as follows : Primarily to 

 give the proper motions of the stars as they 

 result from a precise discussion of all readily 

 available observations; and secondarily, to 

 furnish a Standard Catalogue that shall be 

 practically exhaustive of available material 

 both in extent and in thoroughness of discus- 

 sion. The right ascensions of the stars are 

 freed from the effect of magnitude error and 

 for both coordinates means are furnished for 

 an estimate of the probable errors of the star 

 places at any future epoch, to which they may 

 be projected by means of the elements of their 

 motion presented in the catalogue. 



For about a century and a half a large part 

 of the working force of every generation of 

 astronomers has been given to determining 

 with minute precision the positions in the sky 

 severally occupied by the so-called fixed stars 

 and, from tiine to time, these observations 

 have been in part calculated and discussed 

 with varying degrees of thorouglmess, to de- 

 termine the changes in these positions, that 

 accrue with lapse of time. The British Asso- 

 ciation Catalogue of Stars represented in the 

 first half of the nineteenth century the high- 

 water mark of such utilization of the raw 

 material furnished by the observing astron- 

 omer and, in our own day, the catalogues of 

 Auwers and Newcomb represent in more lim- 

 ited scope but with greatly augmented pre- 

 cision, the advance achieved in this direction. 



The diminished scope of the more modern 

 compilations is doubtless due in part to the 

 growing burden of treating a greatly increased 

 body of observations, but in even greater meas- 

 ure it is due to the adoption of higher stand- 

 ards of precision, that can be met only in the 

 case of those few stars that have been longest 

 and best observed. It is therefore noteworthy 

 that the present catalogue comprising about 

 four times as many stars as its nearest rival 

 (Newcomb) is announced by its author as 

 being the first installment of a work that, 

 when complete, will furnish the positions and 



motions of some 25,000 stars observed and dis- 

 cussed with a completeness hitherto attained 

 only within the very restricted lists above 

 noted, 1,596 stars in aSTeweomb's catalogue. 

 While much of the program thus announced 

 depends for its realization upon observations 

 and discussions still to be made, the present 

 completed volume probably represents the 

 larger part of the total task, since in it theis 

 is established the fundamental system of star 

 places to which all else is to be conformed. 



It is well understood that every set of ob- 

 servations made with a given instriunent by a 

 given man, or set of men, contains minute 

 errors of a systematic character peculiar to 

 itself, and any catalogue constructed from 

 many and divers sets of such observations 

 must present a veritable mosaic of these in- 

 herent errors, that may completely mask 

 or vitiate such minute quantities as the con- 

 cluded proper motions of the stars. Tor the 

 detection and elimination of these systematic 

 errors of the data, Boss has collated the more 

 important series of observations made in the 

 nineteenth century, about eighty in number, 

 and by intercomparison, checking one against 

 another, has reached tentative conclusions 

 with regard to the corrections that must be 

 applied to each in order to adjust it to the 

 standard fixed by the combined body of data. 

 Applying these corrections and averaging the 

 results, there is obtained the system of star 

 places to which reference is above made, and 

 as a by-product the relative measure of cred- 

 ence to be assigned these several authorities, 

 i. e., their combining weights, in the forma- 

 tion of a catalogue. It is of some interest to 

 note that by comparison with the system of 

 star places less elaborately developed by the 

 late Professor Newcomb, Boss's stars in the 

 regions adjacent to the equinoxes are south 

 and west of the positions assigned them by 

 Newcomb by amounts that will average three 

 or four tenths of a second of arc, and pre- 

 sumably discordances of comparable amount 

 obtain in other regions. 



The normal type of star catalogue has be- 

 come so well established as to leave scant 

 room for variation, but a unique feature of the 



