Die Bewegunc; dbk Kometenschweifbiatekie aue hypbrbouschen Baiinen. 55 



§ 10. Die beim Kometen 1892 I Swift beobaehtete 

 Bewegung 1 einer Sehweifverdie]ltung , . 



Der Komet 1892 I wurde von Swift in Rochester am 6. Marz 1892 entdeckt. Die 

 ersten Spuren eines Scliweifes sah Fin lay am 26. Marz. Vom 29. Marz an konnte der 

 Sckweif sckon mit dem blossen Auge beobachtet werden. William H.Pickering erhielt auf 

 dem ((Astronomical Observatory of Harvard College» am 29. Marz bis zum 8. Mai eiue 

 ganze Reihe pliotographischer Aufnahmen dieses Kometen, welche er in seinem Artikel 

 ••Swifts Comet 1892 I» l ) einer eingeheuden Besprechung unterzieht. Im gegeuwartigen 

 Falle interessieren uns nur die vom 5. bis zum 10. April 1892 erhaltenen Photographien 

 des Kometen Swift. W. H. Pickering teilt folgendes uber dieselben mit 2 ): 



«It has been said that it was in general impossible to identify any particular region of 

 the tail upon two successive days. A striking exception to this rule occurred on the dates 

 of April 6, 7 and 8. On April 6 an unusually bright detailed structure was noted in the 

 tail not far from the head. By April 7 it had increased its distance materially, and by 

 April 8 was still farther removed. Upon the better one of the two negatives taken on 

 April 10, a faint marking was detected at a considerable distance from the head of the 

 comet. It was in the right position angle, and its distance was such that it seemed possible 

 that it might be the same structure that was photographed upon the earlier dates. A careful 

 examination of the plate taken on April 5 now showed a minute bright elongated region in 

 the northern branch of the tail, not far from the nucleus, and measuring about 3' by 45 7 . 

 It was in a somewhat different position angle from the objects seen upon the other four 

 plates, but the difference was not greater than might be accounted for by the rotation of 

 the tail 3 ). The objects of April 6, 7, and 8 were, owing to their conspicuous appearance, 

 evidently identical, whether those of April 5 and 10 were also, could only be determined by 

 a computation of the theoretical places in which they should fall.» 



«The chief difficulty in measuring the distance from the bright region to the nucleus 

 upon the different negatives lay, not in the measurement itself, which was comparatively 

 simple, but rather in deciding upon the portion of the bright region from which the measure- 

 ment should be made. This was due to the fact that this region was in general irregular 

 both in shape and density. Owing to the diffused character of the markings it was quite 

 impossible to use a dividing engine, but in some cases a pocket magnifier was employed, 



1) Annales of the Astronomical Observatory of Harvard College. Vol. XXXII. — Part. II. 1900. pg. 267— 205. 



2) Loc. cit. pg. 276—277. 



3) Die hier von W. H. Pickering vorausgesetzte Drehung des Schweif.es ist, wie schon von Bredichin 

 ofters hingewiesen, vom rein mechauischen Standpunkte aus, vollig unmoglich. 



