■WEBER ON A TRANSPORTABLE MAGNETOMETER. 573 



Comparison with the force m T. 



Hence the force of torsion is given in parts of m T 

 _ 5 7-295 167-69 _ 12-563 

 - "60-65 ■ 2243 ~" 178 * 



Angle of Torsion. 



The distances of the observed divisions of the scale from the 

 zero point of torsion being designated by x and y, then x is the 

 angle of torsion sought, expressed in divisions of the scale ; and 

 for determining x we have the following equations : 

 292-90 — X = 328-67 — y 

 12-563 X = y. 

 Hence the angle of torsion in divisions of the scale is found, 



X = 3-09, 

 in seconds of arc 



3-09 



2174 



206265" = 293". 



From this determination of the force and of the angle of torsion, 

 the correction on account of torsion to be applied in measuring 

 the declination is found 



= JL . 293" = l"-65. 



178 



This correction is so small that it may be wholly neglected ; the 

 more so, as, dviring the time occupied in the measurement, the 

 declination itself altered two divisions of the scale, so that the 

 angle of tor.sion for the time of this measurement almost wholly 

 disappeared. 



