Alternating Current Magnetic Curve Tracer. 109 



axis (called hereafter the I- magnetometer helix) will be de- 

 flected. The horizontal suspension being a silver unifilar 



Fig. 1. 



-Magnetometer System. 



\<\P 



torsion-wire, the angular displacements of the helix may be 

 taken proportional in magnitude to the product of the mag- 

 netic moments of the long rod and the helix, at the point in 

 the alternating current waves at which the helix becomes a 

 magnet. As will be seen on referring to curve (a), fig. 2, 



Fig. 2. — Calibration of Magnetic Curve Tracer. 





(a) Ordinates = deflexion of I-magnetometer helix. 



Abscissae = magnetic force at eentre of I-magnetometer helix, 

 (o) Ordinates = deflexion of H-magnetometer helix. 



Abscissas = current in H-deflecting coils. 



by keeping the mean strength of the intermittent current 

 constant throughout an experiment, the vertical displacements 

 of the I-magnetometer helix may be taken proportional to the 



