UNIFILAR MAGNETOMETER. XXV 
TABLE 2.—Determination of the Induction Coefficient for the large Deflecting Bar. 
Interpolated 
Gottingen Position of Bifilar Reading, Sum of _ | Difference Value of 2” 
a 
Mean Time. Deflector. Reading. Deflector | Deflection. | pepections. | of Deflec- 
Away. tions. 
Se. Div. Se. Div. Se. Div. 
Away 157-12 
N. Pole S:| 265-35 156-05 
N. Pole N. 42-57 154-97 
Away 153-90 
Away 154-22 
N. Pole 8. 263-60 154-95 
N. Pole N. 43-47 155-47 
Away 156-10 
Away 156-75 
N. Pole 8. 266-90 157-32 
N. Pole N. 46-75 157-72 
Away 158-20 © 
Away 150-50 
N. Pole S. 259-12 
N. Pole N. 39-57 
Away 150-27 
Away 150-75 
N. Pole 8. 259-46 
N. Pole N. 39-67 
Away 151-47 
Away 151-27 
N. Pole 8. 261-10 
N. Pole N. 40-60 
Away 151-77 
Away 152-17 
N. Pole 8. 260-97 
N. Pole N. 39-97 
Away 151-60 
27. The adopted value of °”* = 0-0112. 
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. [For the final results, see the addendum to the In- 
troduction.] . : 
BIFILAR OR HoRIzZONTAL ForcE MAGNETOMETER. 
28. This instrument was made by Gruss of Dublin, and is similar in its general 
construction to the declinometer, having two boxes, gilt internally and externally as 
in the latter instrument. The magnet a a, whose dimensions are 15 inches, Z inch, 
and { inch, is placed in a stirrup 6, which carries below it a tube c, having a lens d 
MAG. AND MET. oBs. 1845 anp 1846. g 
