.332 



EEPOKT — 1893. 



because I wished to take observations in tbe east- west plane. The lamp 

 and photographic apparatus are mounted on wooden tables, and the dis- 

 tance between the pendulum mirror and the drum is a little less 

 than 2 m. The necessary preparations were made in November 1891, 

 but regular observations did not begin until April 1892. At first 

 many intei-ruptions occurred owing to the extraordinary motions of 

 the zero-point, which caused me to discontinue the observations for a few 

 days at the beginning of May. A second interruption occurred in June, 

 because it was necessary to have the mirrors resilvered ; but since July 18 

 last until now the instrument has been in good working order, and only 

 on two occasions the continuity of the observations is broken by sudden 

 motions, which caused the light- point to travel beyond the borders of the 

 paper before it could be noticed at the usual control. To finish the 

 account of the instrumental arrangement, I have to add that since 

 November paper from the manufactories of Dr. Stolze in Charlottenburg 

 has been used instead of Morgan and Kidd's paper, and that a great im- 

 provement has thus been obtained owing to its much greater sensitiveness. 



For the details respecting the first part of the observations between 

 April 4 and September 18, 1892, I refer to the ' Astronomisclie 

 Nanhrichten,' No. 3147. The discussion of the later observations, to- 

 gether with a general investigation, has been deferred until later, 

 because it is intended to continue the series up to the beginning of 

 •September. For this reason I am unable here to give definite results, 

 and shall only mention what may be of use to other observers. 



The daily period is much smaller than it was found when the pendu- 

 lum was placed in the meridian, but it is well pronounced, and, to judge 

 from the aspect of the curves alone, it decreases much in winter. 

 During the winter months it entirely disappears on some days. The 

 same fact has been communicated to me as observed at Nicclaiew by 

 Professor Kortazzi. The diagram representing the daily change is much 

 like the one which I found from one day's eye observations at Karlsruhe 

 in 1887, and forty-eight days' observations at Nicolaiew in 1892 give a 

 similar result. The following numbers I extract from the ' Astronomische 

 Nachrichten,' + denoting a deflection towards the north : — 



Thus it is seen that at Strassburg the plumb-line is in its southern 



elongation about 6 P.M. and in its northern elongation about 6 A.M. 



These epochs, however, only represent the mean of the summer months. 



-At Nicolaiew the times of these moments are each about four hours later. 



