192 ASTRONOMY. 



FIXED STARS. 



Catalogue of stars. — "Catalogue of 12,441 stars for the epocli 1880, 

 from observations made at the Eoyal Observatory, Cape of Good Hope, 

 during the years 1871 to 1879. Edward James Stone, M. A., F. E. S., 

 etc. (London, 1881, XXXII, and 5G5, 4to)." This catalogue, published 

 by the Admiralty, is founded on observations made at the Cape Obser- 

 vatory between January, 1871, and April, 1879. The observatory dur- 

 ing the whole period was steadily directed to the object in view, the 

 formation of a catalogue of well- distributed stellar zero-points for those 

 portions of the heavens which are beyond the reach of northern obser. 

 vatories. But a considerable number of stars, north of 25° Decl., were 

 also observed at the Cape, and the results have been included in the 

 present catalogue as a check upon the existence of any systematic 

 errors in the work. Lacaille's well -distributed 9,76G stars were adapted 

 as the basis of the working hst, but as some stars of the sixth and 

 many of the seventh magnitude, in Brisbane's Catalogue of 7,385 stars, 

 had not been observed by Lacaille, the greater part of these were also 

 included in the working list. A large stereographic projection of the 

 southern hemisphere was also prepared, on which were projected the 

 places of all the stars previously observed, and whenever lacunse ap- 

 peared within the limits of X. P. D. 115^ to 180°, efforts were made to 

 fill them up by observing stars of rather a lower magnitude than the 

 seventh of Lacaille's scale. A reduced copy of this projection accom- 

 panies the catalogue. Generally each star was observed three times. 



The right ascensions of the stars observed for the determination of 

 the errors of the Transit-clock have been taken from the Greenwich 

 Standard Lists for the different years. The Eight Ascensions of Polar 

 Stars were taken from Mr. Stone's ijaper on "The mean places of eight 

 close Southern Polar Stars, 1860 to 1900." The refractions used are 

 those of the Tabulae Begiomontanse diminished in the proportion of 

 0.9988: 1, but the use of Bessel's tables unaltered would not change the 

 results of the Catalogue by 0".2. As a ijroof of the satisfactory charac- 

 ter of the adopted refractions, a comparison is given between the results 

 of the Catalogue and the places of the Nautical Almanac for 1880. As 

 might be expected from the use of the same fundamental system, there 

 is a close agreement between the Greenwich and Cape Eight Ascensions, 

 but the perfectly independent determinations of X. P. D. are also in very 

 good accordance. Arranging the corrections required by the Xautcial 

 Almanac X. P. D.'s in groups of 6 hours of E. A. and ap])lyiug the gen- 

 eral mean correction — 0".81 to them all, the following corrections re- 

 main: 



Qh_Qh 6»^ — 12»i 121^ — 18^ 18h — 24'' 



-0".24 — 0".ll +0".39 +0".0G 



The changes in these corrections are systematic, and it appears that 

 the complete reversal of the seasons at the northern and southern observ- 

 atories is not quite accurately allowed for in the refraction tables. In 



