1869.] 



Lieut. Elagin's Determinations of the Dip. 



285 



dip for September 1868 is 64° 10'- 9. The observed dip with the Kew 

 Circle is 64° 7' '7, being smaller by 3' '2. 



Paris. — The observations of dip at the Observatory are made with an in- 

 strument of Gambey regularly three times every day — that is, at 9 o'clock 

 in the morning, at noon, and at 4 o'clock in the afternoon. This instru- 

 ment gives only the variations of dip. To determine the absolute dip, a 

 long series of simultaneous comparisons with a Dip-circle have been made. 

 The following dip is deduced from observations with this instrument on the 

 same days as my observations : it is =65° 45 f, 3 ; the result I obtained with 

 the Kew Circle is 65° 49''85, being 4'- 5 larger. 



These were all the stations at which I was able to make satisfactory ob- 

 servations; but as at most of these stations comparative observations atadjoint 

 stations had been made before and the differences found between them, there 

 was less need to extend my observations beyond the principal observatories. 



Table II. contains the dips observed at the different stations before 

 mentioned, and the differences between the local instruments and the 

 Circle from Kew. 



Table II. 



September 1868. 

 Stations. 



Dips observed 



with local 

 instruments. 



Dips observed 

 with Circle 

 from Kew. 



Local instru- 

 ments— Kew 

 Circle. 



Royal Observatory, Greenwich ... 



68 2-19 

 67 56-15 



68 3-80 



67 58-88 



68 17-86 

 67 6-77 

 67 43-30 



63 38-80 



64 7-70 



65 49-85 



— 1-61 

 -2-73 



H-4-23 

 +4-40 

 -6-74 



-4-55 



Utrecht. Meteorol. Department ... 

 Vienna, Meteorol. Institution 



67 11-00 

 67 47-70 

 63 32 06 



65 45-30 



I will now endeavour to deduce the most probable dips at each station. 

 First I shall deduce the dip at Munich, as no observations are made there 

 specially for dip, by taking the differences between the values I found 

 at Munich and at every other station, and applying it to the result as found 

 with the local instrument at each place. Thus the dip I obtained at Kew was 

 68° 3'-80, and at Munich was 64° 7''70 ; the difference is 3° 56'- 1 ; and ap- 

 plying this to the result as found at Kew by the Kew instrument 68° 2'* 19, 

 I deduce 64° 6'' 09 as the dip for Munich ; and treating all the other sta- 

 tions in a similar way I find : — , 



Dip, from Kew =64 6'09 



„ Greenwich . . = 4*97 

 „ Norwich . . . . = 7*70 

 „ Brussels ....= 11*93 

 Utrecht ....= 12-10 



Vienna = 0"96 



„ Paris = 3-15 



Mean 64 670 



y 2f 



