110 



THE ORBIT OF URANUS. 



Mr. Brcen remarks : " The right ascensions are very accurate. It has been 

 assumed that the N. P. D., on 1750, September 13, is identical with (i Capricorni, 

 with which it was compared. The first observation was by the transit instrument, 

 and the second by the quadrant." 



No ground is given for the above assumption respecting the N. P. D. for the 

 second observation ; it may, therefore, be omitted as valueless. 



In the year 1750 we have also two observations by Le Monnier at Paris. For 

 these, and all the other observations by the same observer, 1 shall adopt the results 

 given by Bouvard in the Connaissance dts Temps, for 1821, p. 341, with the cor- 

 rections indicated by Le Verrier, in Connaissance des Temps, for 1849, pp. 125 and 

 126. The necessary uncertainty of the observations is such that, considering that 

 Bouvard reduced them with the star positions of the " Fundamental scarcely 

 anything will be gained by a new reduction. 



1753, December 3, we have another observation of right ascension by Bradley. 

 I adopt the result kindly communicated by my distinguished friend, Dr. Auwers. 



1753, December 3, 



h. m. h. m. s. 



5 33. R. A. = 22 23 21.59 



1756, September 25. Observation by Mayer, at Gottingen. I adopt the result 

 given by Bessel, in Fundamenta Astronomic, p. 284. 



1756, September 25, 



h. m. o i ii 



10 12. E. A. = 348 54.5 



Dec. =61 49.4 



The following is a tabular summary of the preceding results, with their com- 

 parison with the provisional theory. In the computation of the geocentric place 

 the places of the sun were derived from Hansen's Tables. I am indebted to Pro- 

 fessor Coffin for a duplicate computation of the geocentric places from the pro- 

 visional ephemeris, which was executed by Mr. Joseph A. Rogers. 



