202 iSNYDER — A NEW METHOD OF TRANSITING STARS. [April 4, 



personal equation. Even the averaging secured by the great 

 number of electrical contacts does not certainly eliminate the pe- 

 culiarities of a given habit of twirling. At any rate the great 

 number of signals to be read from the chronographic sheet consti- 

 tutes a very serious infliction on time and patience. Finally, the 

 Repsold method does not, during any given star transit, offer a 

 ready and direct means of comparison with the ordinary methods 

 of observation. 



The difficulties experienced in acquiring reliable observing 

 habits with the Repsold transit micrometer are evident from the 

 reports of Becker,^ Kowalski,* and Flint. ^ The latter is, it seems, 

 the only American observer who has tried the Repsold device to any 

 extent, and he says that '^ after considerable practice" he obtained 

 the same probable error by the method for *' a signal under good 

 conditions as for a single thread when observing with a fixed 

 reticule and chronograph." 



And yet it is not surprising that among European obser\»ers 

 engaged in longicude work, the Repsold method should after pro- 

 longed discipline yield excellent results. Albrecht,^ in an extended 

 paper on its application to longitude work, points with enthusiasm 

 to the superior results obtained. He considers the former indiffer- 

 ent results to be due to lack of practice and insists that the highest 

 effectiveness, by this method, is attained only after a long season 

 of active experience. '' Man erlangt das Maximum der Leis- 

 tungsfahigkeit doch auch bei dieser Method e erst nach langer 

 Uebungszeit." 



These experiences of practiced observers, while pointing to the 

 value of the plan of micrometer thread motion in eliminating per- 

 sonal equation and its variations, confirm the anticipations of the 

 writer as to the inherent defects of the Repsold method. It is 

 therefore interesting to note that experiments for relieving some of 

 the imperfections of the method have been going on at the Konis- 



1 Loc cit. 



2 Ueber das neue selbstregistrirende Mikrometer von Repsold, Petersburg, 

 1897. 



3 Albert S. Flint," The Repsold Micrometer of the Washburn Observatory," 

 Astron. Jour., No. 470, 1899, September. 



* Prof. Th. Albrecht, « Die Beobachtungsmethode mittelst des Repsold'schen 

 Registrirmikrometers in ihrer Anwendung auf Langenbestimmungen," Astron. 

 Nach., 3699, 1 90 1, Marz. 



