Delinitive Orbit of Comet 1894 IV (E. Swift). 



By Frederick II. Scares. 



1. Introductory. 



Comet i8g4lV was discovered by Kdward Swift at 

 Echo Mountain, California, on Nov. 20, 1894 at 8'' 30'" p.m. 

 The cornet was then very faint and had a short tail. The 

 first observations were obtained by Barnard with the 12 inch 

 Equatorial of the Lick Observatory on Nov. 21, 22, and 23, 

 and by Javelle at Nice on Nov, 22 and 23. 



A rapidly increasing deviation from the positions pre- 

 dicted by means of the preliminary parabolic elements gave 

 indication of decided ellipticity which was soon confirmed 

 by later elements. 



A great similarity between the elements of the new 

 comet and those of De Vico 1844 I was soon noted and the 

 possibility of identity was suggested by Berberich as early 

 as Nov. 23. On Dec. i 'I'isserand announced that Schulhof 

 had found the two comets to be identical. 



Owing to the extreme faintness of the object obser- 

 vations were obtained with the greatest difficulty as is suffi- 

 ciently evident from the notes by the various observers, and 

 in many places bad weather made observing (|uite impossible. 

 This was especially the case at Mt. Hamilton where in spite 

 of constant watchfulness on the part of Barnard the comet 

 was not seen from Nov. 30, 1894 until Jan. 25, 1895. As 

 a consecjuence the total number of positions is only 64 for 

 right ascension and 63 for declination. 



The first set of elements approximating a definitive 

 solution were by Chandler from 27 observations grouped 

 into 6 normal places. Basing himself upon this system of 

 elements Chandler undertook a preliminary investigation of 

 the question of identity with De Vico's comet, carrying the 

 jierturbations back through the conjunction with Jupiter in 



1885. It seemed useless on account of the necessary in- 

 determinateness of the value used for the mean motion to 

 carry the calculation of the perturbations farther , but 

 enough had been done to accomplish a partial adjust- 

 ment of the discrepancies between the two comets and to 

 show that the effect of the conjunctions with Jupiter in 1874 

 and 1862 would be in the right direction to produce a still 

 better agreement. Notwithstanding the definiteness of the 

 announcement concerning Schulhof's conclusions they were 

 only provisional and were derived from a consideration of 

 the perturbations of De V^ico's comet throughout a long series 

 of years. They were substantially the same as those arrived 

 it by Chandler and may be found in \. N. No. 3267. With 

 this encouragement the calculation of the definitive elements 

 of comet Swift was begun, and the results are here pre- 

 sented as a part of an investigation of the question of identity 

 with De Vico's comet which the writer has undertaken. 



2. Calculation of Ephemeris. 



The following elements by Chandler in \. J. No. 338 

 were used as the basis of the calculation. 



T == 

 CO = 



ft = 



log'/ = 



Period = 



1894 Oct. 12.18817 Gr. M. T. 

 296° 34' 35''2 I 



40 44 37> 

 2 57 53-9 

 o 1436451 

 0-57I895 

 2 141.6 days 



1 894.0 



With these was calculated an ephemeris of i day inter- 

 vals from 1894 Nov. 19.5 to 1895 Jan. 30.5 Berlin M. T. 



Ephemeris for Berlin Mean Midnight. 



i 



