TERRESTRIAL MAGNETIC INTENSITY. 



27 



the isoclinal lines would, even by this instrument, have been determined with 

 very considerable exactness. The following Table contains observations made 

 with only one needle (marked No. 11. ), the other (from having too thick an axis) 

 having been found to give much more anomalous results. 



Table X. 

 Obsei'vations of Magnetic Dip with a Three Inch Circle. 



Date. 



Station. 



Marked End 



Remarks. 



N. Pole. 



S. Pole. 



Mean. 



1832. 













April 23. 



Edinburgh. Greenbill \ 

 House, . J 

 Edinburgh, .... 

 Edinburgh, .... 



71.0' 



o / 



71.46 



O / 



71.23 



j Mean 71° 33'.2. But the two last 



April 23. 

 May 23. 



71.2G 

 71.31 



71.42 

 71.46 



71.34 

 71.38 



/ observations are the best. These ob- 

 )"servations are the only ones made in 



1 a noiicip 



May 28. 



Edinburgh .... 



71.29 



71.45 



71.87 



1 <X UULloC* 



July 11. 



Brussels Observatory, 1 

 (sameplace as intensity) f 



68.55 



69.1 



68.58 



/ 68° 49' according to M. Quetelet, 

 (.May 1832. 



July 17. 



Spa (same place as in-i 

 tensity, .... J 

 Heidelberg, 



a. On the bank of the 'I 

 Neckar, two miles > 

 above the town, . J 



b. Prof. Leonhard's \ 

 garden, ... J 



c. Terrace of the Castle, 



68.20 



68.24 



68.22 













\ Mean 66° 87'.1. I have changed 



July 27. 



66.23 



66.46 



66.34 



the leadings at the first station from 



67° to 66°, considering the former as 



[ an undoubted error. This is confirm- 



Aug. 7. 



66.20 



66.44 



66.32 



r ed by observations made at the same 

 three stations by Needle No. I., which 



Aug. 7. 



66.33 



66.59 



66.46 



gave 66° 48', 66° 18', 66° 57'— Mean 

 / 66° 41'. 



Aug. 4. 



Laach ; S.E. side of Lake, 



67.58 



68.22 



68.10 



Good observation. 



Aug. 5. 



Andernach; foot of thel 

 hill west of the town, J 



67.33 



67.45 



67.39 



{ Good. The difierence between this 

 -| and the last probably due to volcanic 

 ( influence. 



Aug. 18. 



Cologny, near Geneva,) 

 Prof. Necker's garden, J 



64.45 



65.10 



64.67 



r 65° 48.'5 in 1825 (Arago). The 



Aug. 20. 



Geneva Observatory, 



64.66 



65.14 



65.5 



< dip diminished at Paris about 27' be- 

 (.tween 1825 and 1832. 



Aug. 22. 



Mount Breven, summit. 



64.38 



65.11 



64.54 





Aug. 23. 



Chamouni (same place \ 

 as intensity), . . J 



64.45 



65.16 



65.0 





Aug. 25. 



Jardin 



64.45 



65.7 



64.58 





Aug. 29. 



Aoste (same place as in- ) 

 tensity, .... J 



64.36 



64.58 



64.47 





Aug. 81. 



St Bernard, near the Lake, 



64.43 



65.7 



64.55 



r Difficult observation. Local influ- 



Sept. 3. 



Martigny, 



64.35 



64.43 



64.39 



■^ ence being suspected, the operation 

 (.was repeated at Bex. 



Sept. 3. 



Bex ; in an orchard S. W. "| 

 of the town, . . . / 



64.47 



65.14 



65.0 



Very good observation. 



Sept. 10. 



Interlaken; sideof the Aar, 



65.13 



65.30 



65.22 





Sept. 22. 



• • • ■ • • ■ 



65.10 



65.39 



65.25 





Sept. 29. 



Hospital; St Gothard \ 

 near the old castle, J 



65.22 



65.31 



65.26 



Indifferent observation. 



Sept. 30. 



St Gothard Hospice 



64.50 



65.30 



65.10 





Oct. 2. 



Locarno (Lago Magiore) ) 

 below the convent, J 



64.48 



65.13 



65.0 





Oct. 11. 



PfefFers ; near the Bath- \ 

 house, .... J 



64.55 



65.23 



65.9 





1835. 













June 13. 



Paris Observatory; M. ) 

 Arago's cabinet, . J 



67.8 



67.26 



67.17 



67° 24' by M. Arago. July 1836. 



Remark. — The dip at Edinburgh is undoubtedly affected by being made within a house. Some observations 

 roughly made at the time in the open air confirm this; and more recently, I have found the dip by the same 

 instrument to be 71° 44'.5 (2d February 1837) and 71° 50'.5 (best, 4th February)— although the dip has been 

 diminishing every year. 



