OF ARTS AND SCIENCES. 



17 



3. Observations on the Comets of 1845 and 1846. 



Ohservations on the Comet of June, 1845, made at the Cambridge Ob- 

 servatory. Lat. 42° 22' 49". Long. 4'" 44™- 32'-. 



The observed differences of A. R. and Dec. were applied to the A. R. and Dec. 

 of the stars referred to the mean equinox of January 1st, 1846. 



" The comet was first seen at M""- IS""-, June 2d. The observations of 

 this morning are made with the spider-line micrometer, and under favor- 

 able circumstances. 



" June 4th. The differences of A. E.. were obtained this day from the 

 hour-circle of the equatorial, which reads to single seconds of time. 

 The comet could be seen with the naked eye after most of the stars of 

 the second magnitude had disappeared. It being somewhat cloudy, the 

 length of the tail could not be well determined. The nebulosity was 

 very much condensed and beautifully defined : near the head of the 

 comet, the tail was plainly divided into two branches. 



" June 6th, A. M. The head of the comet broad and full ; in the course 

 of six hours, it has undergone a remarkable change, becoming pointed, 

 and appearing with a spur or secondary tail (which is the brightest of 

 the two) of two degrees in length. The axes of the tails are inclined at 

 an angle of twenty degrees, though the estimation is quite uncertain. 

 The principal tail may be traced through five degrees. The observa- 

 tions are made as on the 4th. 



" On the 9th and 10th, the observations are made with the spider-line 



