344 KRETZ. 



employed in the reduction of the plate-measurements. I de- 

 cided, therefore, to obtain the positions of as many stars as pos- 

 sible from all the catalogues available to me, and to use these 

 as standards, that being the method commonly regarded as 

 leading to the most accurate results. How this assumption was 

 borne out in the progress of the work will be shown later (Part 

 II, Sect. IV). The list of catalogues examined includes all 

 that may claim any confidence mentioned in Knobel's memoir,' 

 besides all important modern ones, and I have attempted to 

 make it practically complete. Twelve stars were thus found 

 sufficiently well determined to warrant their reduction. One of 

 these was subsequently rejected as standard, the remaining 

 eleven being finally retained. I shall give, however, a record 

 of all observations of stars in my zone which I found in the 

 catalogues. 



List of Catalogues Used. — Of the catalogues examined, the 



following contained observations of stars present on the plates : 



(i) BRADLEY, 1755. Neue Reduction des Brad- 



ley'schen Beobachtungen aus den Jahren 1750 bis 1762 



von Arthur Auwers. St. Petersburg, 1888. 



(2) PIAZZI, 1800. Praecipuarum Stellarum inerran- 

 tium Positiones Mediae * =)= * ex observationibus habitis 

 * * * ab anno 1792 ad annum 1813. Panormi, 1814. 



The dates were obtained from the original observations in the 

 Storia Celeste ; they are however very doubtful, as in almost every 

 case more observations were found than agreed with the number 

 given in the catalogue, with no way to determine which were ex- 

 cluded from the final reduction. The mean date of all observations 

 was therefore taken ; but in assigning weights the argument used was 

 the number of observations as given in the catalogue. 



(3) LALANDE, 1800. Histoire Celeste Frangaise, 

 Tome I. Paris, 1801. 



Baily's " Lalande," published by the British Association in 1847, 

 was used only as an index to the zone observations, which were re- 



iKnobel, " The Chronology of Star Catalogues," in Memoirs of the Royal Ast. 

 Soc, Vol. 43, p. I. 



