214 



Observations on the Comet of Halley. 



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than might perhaps be fairly ascribed to errors of observation. I 

 therefore computed an ephemeris of the comet, for the months of 

 January, February and March, and waited for additional observa- 

 tions, to enable me to correct still further the elements. The com- 

 et was rediscovered by Prof. Olmsted on the morning of Dec. 31st. 

 Yet, it was then almost immediately lost in the morning twilight, 

 and there was no opportunity for locating it with accuracy. The 

 entire month of January was remarkably unfavorable for observa- 

 tions. Besides the uncomfortable severity of the weather, there was 

 scarcely a clear morning during the month ; so that, although I saw 

 the comet repeatedly, I was yet unable to obtain a single satisfacto- 

 ry observation. On the morning of January 29, Prof. Olmsted saw 

 the comet distinctly with his naked eye ; and during the months of 

 February and March, I saw the comet with my naked eye, about a 

 dozen different mornings. The last of these was Monday morning, 

 March 21st. About the middle of February, the comet passed the 

 meridian at five o'clock in the morning ; and from this time, I made 

 my observations with a small transit instrument of twenty inches fo- 

 cus. The instrument was carefully adjusted to the meridian by the 



The comet would bear no illumina- 



t 



tion, and it was necessary to sit in the dark for five or ten minutes 

 before the comet entered the field. The wires were entirely useless. 

 I therefore contented myself with noting the time, when as I judged 

 the comet was in the middle of the field, and also the instant of 



The altitudes were measured at the same time by a gradu- 

 ated circle which read by a vernier to minutes. Immediately after- 

 wards, I observed in the same w T ay, the passage of two or three stars 

 with which the comet was to be compared. I thus obtained six 

 transit observations about the middle of February, and five about the 

 middle of March. The mean of all the observations made the com- 

 et's Right Ascension in February, 35.9 seconds greater than by my 

 ephemeris, and the Declination P 13" greater; for March the Right 

 Ascension was 55.1 seconds greater, and the Declination 5' 14 

 Having applied these corrections to the computed places for Feb- 

 ruary 18, and March 16, I converted the places thus found into lat- 

 itudes and longitudes. Taking these in connection with the obser- 

 vations of September 24, October 10th and 19th, I determined by 

 means of them, to obtain the final correction of the elements. Pro- 

 ceeding again as in the former case, I varied the perihelion dis- 



method of high and low stars. 



egress. 



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