140 



PROCEEDINGS OF THE AMERICAN ACADEMY 



perion to the limb of Saturn through an intermediate satellite or star. 

 The presence of moonlight, or even the near proximity of Saturn, af- 

 fects its visibility in a much greater degree than is the case with Mi- 

 mas, the inner body of the system. 



" The following elements, representing somewhat roughly the above 

 places, have been computed by Mr. G. P. Bond. 

 Period of revolution, 21.18 days. 



214" at the mean distance of Saturn. 

 0.115 



97° Jan. 1st, 1849. 

 295° 



" The line of nodes and the inclination of the orbit coincide nearly 

 with those of the ring." 



4. Observations on Petersen''s Second Cornet^ made at the Cambridge 



Observatory. 

 Corrected for refraction, and referred to the Mean Equinox of Jan. 1st, 1848. 



Mean distance. 

 Eccentricity, 

 Mean anomaly, 

 Perisaturnium, 



" Nov. 26th. The comet was first seen at 6^- 30™ ; it shows a fine- 

 ly marked nucleus, with a tail of 15' or 20'. 



" At 6"- 56'"- 4P-, M. S. T., it followed a star of -the 9th magnitude by 

 0™- 25' .60, and was north of it by 2' 25". 1, by ten micrometric com- 

 parisons. The centre is so well defined that the relative places of the 

 star and comet may be found with great nicety. The A. R. and Dec. 

 on the 25th, 28lh, and 29th are from instrumental comparisons. 



" Nov. 30th. The nucleus passed within one second of arc of a 

 star of the 12th magnitude ; both appeared of the same magnitude, 

 and formed a close double star, but were not in contact ; at the time 

 of nearest approach, the comet could be seen to move. 



'■'■Dec. 18th. Tail of the comet 2° in length. There are traces of a 

 secondary tail, at an angle of 10° or 20° with the principal one. 



" Dec. I9th. The breadth of the tail in its brightest part, at 20' 

 from the nucleus, is only about one minute of arc. 



" Jan. 22d. Altitude of the comet at the observation = 8°." 



