20 



handboob: of magnetic compass 



26. The deviations resulting from the earth's field induction of these 

 unsymmetrical arrangements of horizontal soft iron are illustrated by 

 the sketches in figure 17, showing the ship on a few different compass 

 headings. The other heading effects may be similarly studied. 



Such an E deviation curve is one of the several curves indicated 

 in figure 13. It will be observed that these E deviations are 'maxi- 

 mwm on cardinal headings and zero on the intercardinal headings. 



Easterly 



Degrees of 



CeHqpasB 

 Deviation 



Westerly 



(-) 



"B" Deviations 



from Induction 



in the Unsynimet- 



rioal Horizontal 



Soft Iron 



Vertical Induced 

 Magnetic "B" Deviations 



"D" Deviations from Induction 



in the Synmetrioal Horitontal 



Soft Iron. 



"A" Deviations from Unsymmetrical 

 Horiiontal Soft Iron 



Ship's Compass Headlr^ - Degrees 

 Figure 13. — Induced magnetic deviation effects. 



FiGtJEH 14. — Symmetrical arrangements of borizontal soft iron. 



27. It is pointed out that these quadrantal deviations will not vary 

 with latitude changes, because the horizontal induction varies pro- 

 portionally with the directive force, H. 



28. The earth's field induction in certain other unsymmetrical ar- 

 rangements of horizontal soft iron create a constant A deviation 

 curve. The magnetic A and E errors are of smaller magnitude than 

 the other errors, but, when encountered, are generally found to- 

 gether, since they both result from unsymmetrical arrangements of 



