which have been discovered since July 1844'. 415 



constellation Perseus. During the first half of the month it 

 was distinctly visible to the naked eye. The nucleus was very 

 bright, equal to a star of the third magnitude, and a tail 2° in 

 length was seen until moonlight interfered. On June 9, with 

 a low power on Mr. Bishop's refractor, the tail was evidently 

 bifid ; one well-defined branch extended to a distance of about 

 2^° from the nucleus, the other train was much shorter and 

 very ill-defined. The tail was far brighter on the preceding 

 than on the following side. In about a week from this time, 

 a coma formed round the nucleus, and the tail assumed a fan- 

 like form, somewhat diminishing in length. Prof. Santirii ob- 

 served the comet at Padua until the end of June, but it was 

 not generally seen after the 20th. 



The most rigorous investigation on the elements of this 

 comet is one recently published by M. d'Arrest. From fifty- 

 two right ascensions and fifty-four declinations he deduced 

 seven normal positions between June 7 and 17. From these, 

 by the method of equations of condition with least squares, 

 M. d'Arrest computed the most probable parabolic elements, 

 and by a direct solution of the equations (a term depending 

 on a small variation in the eccentricity being introduced), he 

 found that the resulting elements were hyperbolic, with an ec- 

 centricity = I •0025942. It appears, however, that the result 

 of my calculations relating to the comet of 1596, undertaken 

 at the suggestion of Prof. Schumacher, induced M. d'Arrest 

 to ascertain how the observations would be represented by an 

 ellipse, with a period of 249 years; and he finds elements 

 agreeing in the most satisfactory manner with his normal 

 places. It is therefore extremely probable that the comet of 

 1596, observed by Tycho, is identical with the great comet of 

 June 1845. 



M. d'Arrest's elliptical elements are as follows : — 



T 1845. June 571064. Mean time at Berlin. 



O / // 



^ 337 48 56-l}^^^"^q-^'^^^'^- 



i 48 4158-7 

 »in-ie = (p= 81 50 22-3 

 Log. «= 1-598394. 



Motion retrograde. 



The details of my investigation on the comet of 1596 will 

 be found in the Astronomische Nachrichten. The tempestuous 

 state of the weather only permitted Tycho to observe the 

 comet on three days, but the observations were made at very 

 convenient intervals for the determination of the elements. 

 The copy of Tycho's observations, from which I calculated the 



