312 The Orbit and Motion of 



curacy, the heliocentric angular motion at the three interme- 

 diate oppofitions. The angular velocities at the two extreme 

 oppofitions were determined with equal accuracy, by fuppofing, 

 that the changes of angxilar velocity followed a regular law. 

 Thus I was enabled to determine the geocentric motion for a 

 few days before and after appofition, and confequently to af- 

 fign, from each obfervation, the precife time and place where 

 the Planet would be in oppofidon to the Sun. Thefe determi- 

 nations differed from each other in no cafe i o". It is demon- 

 ftrable, that the aflumptions made for this combination of ob- 

 fervations could not produce an error of 2". I therefore, 

 with confidence, took the means of thefe determinations for 

 the places of the Planet, in its apparent oppofitions to the Sun. 



THE times and apparent longitudes and latitudes of the Planet 

 .are exprefled in the following table; 



M. T. Ed. Long. L,at. N. 



h. ' " i. ' " ' " 



1781. Dec. 21. 17.44.33 3.00.52.11 15.07 



1782. Dec. 26. 08.56156 3.05.20.29 18.56 

 .1783. Dec. 31. oo. 46. 24 3. 09. 50. 52 22. 10 

 .1785. Jan. 3. 17. 28. 56 3. 14. 23. 02 25. 40 

 1786. Jan. 8. 10.39.31 3.18.57.05 28.52 



MY manner of obferving obliged me to compare the Planet 

 with two fixed Stars which did not differ from it, or from each 

 other, more than one degree in declination. This obliged me 

 to employ fome Stars which are to be found in MAYER'S Cata- 

 logue alone. I have, therefore, always made ufe of -this Catalogue. 

 If, therefore, the following theory be confronted with an ob- 

 fervation, where the geocentric place of the Planet is deduced 

 from a comparifon of it with a Star in its neighbourhood, and if 

 the place of this Star be deduced from BRADLEY'S, or DE LA 

 CAILLE'S Catalogues, the longitude will be found about 6" too 

 fmall, or as much too great. 



THE 



