HEYL & BRIGGS— THE EARTH INDUCTOR COMPASS. 29 



one quadrant, or R ; hence the total current coming from the armature 

 is i.^E/{R-\-r). 



Laboratory tests fail to show such an error, which, in fact, is non- 

 existent. Though the current output of the armature varies, the 

 distribution of the current in the armature varies also, so that its 



Fig. II 



Coi9 



SiNQ —Cos e 



Sin e -I- Cose 



Sin + Cose 



SjN0 — CO50 



Tin. '^ 



Fi 



g. 1^ 



integrated cross-field reaction is constant. This is readily shown by 

 considering the case of a Gramme ring, of which the compass arma- 

 ture is a special and degenerate case. 



Fig. II represents such a ring, H being the direction of the 

 earth's field. Current will flow as shown by the arrows, producing 

 a cross-field horizontally directed. 



