ORBIT ELEMENTS COMET I., 1899 (SWIFT). 179 



ing rapidly, also that the earth was approaching the line of sight 

 between the sun and comet; these facts combined would possibly 

 have some effect on the brightness. 



The publications of the Astronomical Society of the Pacific 

 contain some beautiful photographs of this comet, taken at the 

 Lick Observatory by Messrs. Coddington and Palmer. These 

 photographs seem to indicate that on May 6th the tail consisted 

 of one main branch some seven degrees in length with side 

 streamers, on the following day the streamers, also the tail, had a 

 a twisted appearance. A sharp bend in the main tail was noticed 

 on May 9th and a day later it would appear to have been longest, 

 being some nine degrees in extent. On May 19th the tail had a 

 curious unsymmetrical aspect, as if one side had been destroyed. 

 On all the dates, the axis of the main tail pointed nearly away 

 from the sun, the greatest observed deviation being about three 

 degrees. 



In the same publications Mr. Perrine gives further details of 

 the curious separation of the two portions and their subsequent 

 recession from one another. He also gives some observations 

 made to examine whether the refraction produced by the comet 

 appreciably altered the positions of the stars over which it passed; 

 the result of his inquiry is negative. 



Orbit Elements. — Preparatory to the calculation here given 

 approximate orbit elements were deduced from a combination of 

 Mr. Tebbutt's observations of March, these were kindly sent in 

 manuscript, but now published, A.N. 3579. The usual formulae 

 for the determination of the orbit elements of a celestial body 

 from three positions being employed ; the result of this calculation 

 will be found in the Astronomisehe Nachrichten, Band 149, No. 

 3575. The following remark was made by the computer, that 

 " the observations were not represented by a parabola, and that 

 the ratio of the residuals indicated some alteration to the eccen- 

 tricity." Prof. Kreutz in a footnote says, "Die aus einer grosser en 

 Zwischenzeit abgeleiteten Elemente von Dr. Stichtenoth in Nr 3567 

 ergeben keine Abweichung von der Parabel 



