Our Present State of our Knowledge of Stellar Motion. 147 



have been or are to be reobserved in the great zones now 

 going on under the auspices of the Astronomische Gesell- 

 schaft, an international association having its seat at Leip- 

 zig. This reobservation is certainly sufficiently accurate to 

 compare with Lalande, whose single observations were 

 made with less accurate instruments than would now be 

 employed; and whose mistakes are many. His zones have 

 been fairly well reduced; and the lamented von Asten has 

 computed new tables of reduction for most of them. 



Piazzi's Palermo catalogue of 7,646 stars for 1800 needs a 

 new reduction. This would, however, be an enormous labor; 

 there are nearly 100,000 observations. Ten years' labor of a 

 skillful computer would at least be needed; and probably 

 this is a very low estimate. The stars do not now need reob- 

 servation owing to the great zones just mentioned. 



(jroombridge's catalogue for 1810 of 4,343 stars needs also 

 a revision. But this would be much easier, as the original 

 manuscript calculations are preserved; and are probably 

 very free from mistakes. What is chiefly needed here is a 

 careful study of the azimuth correction of Groombridge's 

 meridian circle. 



William von Struve published a catalogue of right ascen- 

 sions for 1814 and 1815 in the first volume of the Dorpat 

 observations. This, probably, needs some little revision, 

 owing to its early date; and the same eminent observer con- 

 tinued this work during 1818 and 1819; but these latter 

 observations are unreduced. 



Years' work might readily be spent upon these right ascen- 

 sions of Struve; and would be important for the revision of 

 Groombridge, as the latter would be for that of Piazzi. 



I have myself in progress a careful reobservation of the 

 stars observed by Struve, especially for the difficult region 

 within 10° of the north pole. 



From the Greenwich observations of Bliss and Maskelyne, 

 not much can be obtained for the stars' places. The plan- 

 ets, sun and moon, were the main subjects of Maskeljme's 

 attention. S. Hertzsprung has reduced some of Maskelyne's 

 work upon small stars, and I am myself calculating some 

 more of it for another purpose. 



