112 THE ORBIT OF URANUS. 



1. Observations at Greenwich, 1781 to 1872. 



2 Paris, 1802 to 1827, and 1837 to 1869. 



3 Kdnigsberj,^ 1813 to 1835. 



4, Vienna, 1822, and 1827 to 1839. 



5 Speier, 1827-29. 



Cambridge, 1828 to 1842. 



7 Edinburgh, 1836 to 1844. 



8 Berlin, 1838 to 1842. 



9 Pullvowa, 1841 and 1842. 



10 Washington, 1861 to 1872. 



11 Leiden, 1863 to 1871. 



12 Santiago, 1854 and 1855. 



As to the general distribution of these observations in time, Ave may remark 

 that during the first three or four years tlie planet was zealously observed at 

 Greenwich. Observations then began gradually to fall off until 1798, in which 

 year we find but one. From this time until 1814 only one or two observations 

 were made at each opposition. They become a little more numerous, until 1829, 

 when there is a sudden increase. Few interruptions have occurred since. With 

 regard to the other observatories it may be said that from 1802 until 1830 there is 

 a gradual increase in the number of observations, and that since the latter year 

 the number of observations is entirely satisfactory. 



A great number of the observations were reduced with the star places of the 

 Tahnhv EegiomontaHce, and the entire Paris series are reduced with the star 

 positions of Le Verrier, given in his "■Aji7iales de V Ohservatoire Imperial de Paris" 

 Tome II. As a preliminary to the discussion of the systematic corrections to the 

 principal published reductions, I have prepared the following table, showing the 

 corrections which must be applied to the places of the equatorial fundamental 

 stars in the above catalogues to reduce them to the adopted standard, namely, Dr. 

 Gould's coast survey list in right ascension, and Auwers' standard in declination. 



In the table of right ascensions the first column after name of the star gives the 

 annual variation of that co-ordinate for the epoch 1860.0, as derived from Le 

 Verrier's tables of right ascensions just cited. Next we have the correction to this 

 annual variation, expressed in units of the fourth place of decimals, to reduce it to 

 that given in the " Sl.ar Tahles of the American Ejthemeris," the positions in wliiili 

 are founded on Dr. Gould's Catalogue. The fourth column gives the correction to 

 the right ascensions of Le Verrier for 1860, in hundredths of a second of time. 

 Subtracting from this column sixth-tenths of the preceding, we have the corre- 

 sponding corrections for 1800. The last four columns give the corresponding num- 

 bers for the right ascensions of the Tahulce Regiomontance. 



The table of declinations shows, for different epochs, the corrections necessary to 

 reduce the tabular positions to those given by Auwers in his paper on the decima- 

 tions of the fundamental stars 



