314 Mr. Bowditch on the Comet of 1811. 
about the 2d of October, and at its greatest north latitude the 16th of 
the same month. 
The geocentric longitudes and latitudes were deduced from dis- 
tances of the comet from several fixed stars, observed by a sextant of 
reflection, Lyra, Arcturus, and Dubhe were first used ; then the Po- 
lar Star, Benetnash, Etanin, Deneb, Atair, and Markab ; making 
choice of those stars best adapted to the purpose from their situation 
and brightness. The observations were made by Professor Farrar at 
Cambridge, Hon. Walter Folger jun. at Nantucket and Boston, and 
Mr. John Carlton assisted me in the observations at Salem. In gen- 
eral the same stars were used by all the observers, without any previ- 
ous concert, and the observations agreed as well as was to be expect- 
ed. When any difference was found, the mean of the results was 
used, For greater accuracy the mean of several distances from the 
same star was frequently taken. Too render these observations simul- 
taneous, asmall correction, depending on the daily variation of the dis- 
tances of the comet from the stars, was found and applied to the ob- 
served distances. ‘The correction for refraction was estimated. by ad- 
ding to the observed distance twenty times the correction in the col 
umn Var. of Shepherd’s Tables, corresponding to the observed distance 
and the altitudes. The whole calculation being made in the same man- 
ner as in my memoir on the comet of 1807. 
The calculation of the first approximate values of the elements of 
the orbit, was made by the elegant method of La Place, using the ob- 
servations of September 6, 9, 12, 15, 18, and 23, which gave for the 
Perihelion Distance 1-043, the mean distance of the earth from the 
sun being unity, and the time of passing the Perihelion September 
7d:375 mean time at Nantucket. These were corrected by the ob- 
servations of September 6, 15, and 23, in the manner taught by La 
Place, in page 229, vol. 1, of his Mécanique Céleste, and the result 
