46 



THE OKBIT OF NEPTUNE. 



column. They were made with the large mural quadrant of the observatory 

 attached to the Military School. The Histoire Celeste does not seem to contain 

 any definite information as to the observer or observers by whom the observa- 

 tions were made. 



The stars of comparison which I shall select for the determination of the errors 

 of the instrument and clock are the following : 



May 10. 



a Virginis, 



1 Virginis, 

 /I Virginis, 



2 Librae, 

 f.i Libra 1 , 

 ' Librae. 



May8. 



/? Virginis, 

 $ Corvi, 

 q Virginis, 

 $/ Virginis, 

 a Virginis, 

 h Virginis, 

 x Virginis, 

 X Virginis, 

 2 Librae, 

 s Libra?. 



These lists, I believe, include all of Bradley 's stars observed by Lalande on 

 the dates in question within the zone of the planet, for which reliable modern 

 positions can readily be obtained. Their positions for the year 1795 were obtained 

 as follows. The positions given by Bessel in the Fundamenta Astronomic were 

 reduced by the precessions there given to the mean equinox and equator of ITU"). (I. 

 The modern positions were obtained from the Greenwich Twelve Year Catalogue, 

 the Greenwich observations, or Eumker's Catalogue, and were also reduced to 

 1795.0 with Bessel's precessions. The difference of the results, being supposed 

 due to proper motion, was divided proportionally to the time, and the concluded 

 true position for 1795 obtained. As Lalande's observations arc subject to errors 

 of several seconds, any farther refinement in investigating the positions of the 

 stars would be a waste of labor. In the following table is exhibited the position 

 of the star at the two epochs, referred to the mean equinox and equator of 1795.0, 

 with the modern authorities, and the concluded mean positions for 1795.0 : 



