abstracts: astronomy 79 



over the more usual one employing a zenith distance micrometer which 

 had been used with this instrument in the earlier observations. These 

 observations have not been published in journal form. 



In 1901, the demand for a catalogue of these observations for use in the 

 preparation of the Geschichte des Fixsternhimmels became so insistent 

 that Prof. W. S. Eichelberger, U.S.N. , undertook the work of forming the 

 catalogue, with such reduction as might be necessary. The plan adopted 

 was to select a catalogue rich in stars in this region, and using its posi- 

 tions as standards, to reduce these zones to the system of the selected 

 catalogue with the greatest rigor possible. The catalogue selected as 

 the standard was the Cordoba General Catalogue. The work involved 

 was very great, especially as there were an excessive number of blunders 

 of record due to the inexperience of many of the observers. To the pains- 

 taking care with which this plan has been carried out must be ascribed 

 the value of the resulting positions. 



Without the Cordoba General Catalogue, it would have been impossi- 

 ble to have made a satisfactory discussion of these zones, as no other 

 catalogue would have furnished a sufficient number of reference stars 

 to determine the peculiar errors which affect many of the zones. Fur- 

 thermore, without the assistance of the Cape Photographic Durch- 

 musterung which was published 1896-97, it would have been impossible 

 to have corrected many of the numerous errors of record of the stars too 

 faint to be in other catalogues. The column of notes bears testimony 

 to the necessity for such a check on the observations. While, therefore, 

 the formation of a catalogue of these observations may be regarded as 

 having been unduly delayed, it is in some respects fortunate that it was 

 not done until these works were available for use in its formation. 



The catalogue gives the separate positions resulting from each obser- 

 vation. The probable errors vary considerably for the three instruments, 

 the average being about ± 0?07 for a single observed right ascension and 

 =•= 173 for a single observed declination. For comparison it may be 

 stated that the corresponding probable errors for the Astronomische 

 Gesellschaft zone observed at this Observatory from 1894 to 1901 were 

 ±0?050 in right ascension and ^O'/SS in declination. A considerable 

 part of the excess in probable error of the earlier observations is undoubt- 

 edly due to the large zenith distance, averaging about 66°, at which the 

 observations were made. All things considered, it appears that the right 

 ascensions determined by the Transit Instrument and the Mural Circle, 

 and the declinations determined by the Mural Circle are fairly satisfac- 

 tory. 



