Unifilar Magnetometer. 



xxv 



wooden beam : the deflecting bar when removed and replaced, was carried with a thick 

 cloth glove or silk handkerchief, to prevent variation of temperature in handling. 

 In reversing the magnet, the same side was always kept next the bifilar magnet.* 



Table 2. — Determination of the Induction Coefficient for the large Deflecting Bar. 



Gottingen 

 Mean Time. 



Position of 

 Deflector. 



Bifilar 

 Reading. 



Interpolated 



Reading, 



Deflector 



Away. 



Deflection. 



Sum of 

 Deflections. 



Difference 

 of Deflec- 

 tions. 



Value of — - 

 m 



d. 

 1847. 

 Nov. 5 



11 

 15 

 19 



Away 



N. Pole S. 



N. Pole N. 



Sc. Div. 



157-12 



265-35 



42-57 



Sc. Div. 



156-05 

 154-97 



Sc. Div. 



109-30 

 112-40 



Sc. Div. 



221-70 



Sc. Div. 



3-10 



00140 





23 



24 

 27i 

 30 



Away 

 Away 

 N. Pole S. 

 N. Pole N. 



153-90 



154-22 



263-60 



43-47 



154-95 

 155-47 



108-65 

 112-00 



220-65 



335 



0-0152 





33 

 36 

 40f 

 44 



Away 

 Away 

 N. Pole S. 

 N. Pole N. 



15610 

 156-75 

 266-90 



46-75 



157-32 

 157-72 



109-58 

 110-97 



220-55 



1-39 



0-0063 





48 



Away 



158-20 













Nov. 6 



1 12 

 15 

 18 



Away 

 N. Pole S. 

 N. Pole N. 



150-50 



259-12 

 39-57 



150-42 

 150-35 



108-70 

 110-78 



219-48 



2-08 



00095 





21 



1 23 



26 



29 



Away 

 Away 

 N. Pole S. 

 N. Pole N. 



150-27 



150-75 



259-46 



39-67 



150-97 

 151-18 



108-49 

 111-51 



220-00 



3-02 



0-0138 





33 



1 34 



37 



40 



Away 

 Away 

 N. Pole S. 

 N. Pole N. 



151-47 



151-27 



261-10 



40-60 



151-44 

 151-60 



109-66 

 111-00 



220-66 



1-34 



0-0061 





43 

 1 45 



48 

 50 



Away 

 Away 

 N. Pole S. 

 N. Pole N. 



151-77 



152-17 



260-97 



39-97 



151-98 

 151-85 



108-99 

 111-88 



220-87 



2-89 



0-0131 





54 



Away 



151-60 













8 m 



27. The adopted value of — = 0-0112 



1)1 



This value is very large, more than twice as great as that obtained for small 

 4-inch bars, and is evidently not to be neglected in the rudest mode of observation 

 for the horizontal intensity. 



28. In consequence of the more accurate determination of the value of K, the mo- 

 ment of inertia of the deflecting bar, and of h the bifilar coefficient, and on account of 



* It will in general be preferable to place the deflecting bar to the east or west (as hi the present 

 observations), rather than to the north or south of the bifilar magnet, since I have found that the 

 centre of figure may differ considerably from the centre of magnetism; perhaps, for the same reason, 

 when observations are made only on one side of the bifilar magnet, the deflecting bar should be in- 

 verted when it is reversed, since the magnetic axis may be nearer one side of the bar than the other. 



MAG. AND MET. OBS. 1844. g 



