Mr ROTHMAN-S OBSERVATIONS OF HALLEY'S COMET. 



505 



APPARENT GEOCENTRIC PLACES OF THE COMET. 



I think that no reliance is to be placed on the places for the Snd 

 and 4th of October. It has already been noticed how difficult and 

 uncertain the observations of the latter day were: those of the former 

 present an anomaly for which I am at a loss to account. Though they 

 appear to agree with each other, they indicate a retrograde instead of 

 a direct motion in right ascension. The cause of this error I cannot 

 assign. Excluding these two places, I have compared the others with 

 Mr Stratford's Ephemeris in the N.A. for 1839, in which the pertur- 

 bations are taken into account. I have obtained the following results 

 for the diffijrences in right ascension and declination; where it will 

 be observed that + indicates that the observed right ascension or decli- 

 nation exceeds that found by ccdadut'ion, and also that the differences 

 in right ascension have been reduced from the equator to the pandlel 

 of the Comet. 



