212 



Observations on the Comet of Halley. 



the means of several observations. The places of the stars marked 

 (A) are from the Catalogue of the Royal Astronomical Society, 

 with the exception of 1305 which is taken from the Nautical Alma- 

 nac. The places of the remaining four are from Bode's Catalogue, 

 and vseve furnished by Lalande. 



The places of the comet thus determined were corrected for re- 

 fraction, parallax and aberration ; the Right Ascensions and Decli- 

 nations, after being reduced to the same instant of time, were con- 

 verted into longitudes and latitudes ; the longitudes were referred to 

 the mean equinox of Jan. 1, 1836, and the results are given in the 

 table on page 216. Having obtained the true geocentric places of 

 the comet, I proceeded to compute the elements of its orbit. I first 

 made trial of the method of Olbers for a parabolic orbit, but it gave 

 me a result differing very much from the truth. I obtained the Ion- 



