ILLUSTRATIONS 



Part I.— MAGNETIC ADJUSTMENT 



Figure Title I'age 



1. Mechanics of magnetic compass adjustment 5 



2. Lines of magnetic force about a magnet 7 



3. Terrestrial magnetism 9 



4. Earth's horizontal magnetic field zones 10 



5. Earth's vertical magnetic field zones 11 



6. Earth's magnetic variation chart 13 



7. Components of permanent magnetic field at the compass 15 



8. Permanent magnetic deviation effects 16 



9. Force diagrams for fore-and-aft permanent B magnetic field 17 



10. Force diagrams for athwartship permanent C magnetic field 17 



11. General force diagram 18 



12. Ship's vertical induced magnetism i 19 



13. Induced magnetic deviation effects 20 



14. Symmetrical arrangements of horizontal soft iron 20 



15. Effects of symmetrical horizontal D induced magnetism 21 



16. Unsymmetrical arrangements of horizontal soft iron 21 



17. Effects of unsymmetrical horizontal E induced magnetism 22 



18. Binnacle with compass and correctors 23 



19. Summary of compass errors and adjustment • 25 



20. Uncompensated deviation curve 26 



21. Typical deviation curve and its individual components 29 



22. Comparison of deviation curves (magnetic heading versus compass 



heading) 32 



23. Napier's diagram— Form NBS 1103 33 



24. Heading relationships (variation, deviation, and headings) 36 



25. Azimuth circle set-ups 39 



26. B, C, and D deviation effects 53 



27. A and B deviation effects 54 



28. Tabulating anticipated deviations — Analysis method 55 



29. Tabulating anticipated deviations — One-swing method 56 



30 Deviation table— Form NBS 1104 58 



31. Quadrantal sphere correction curves 61 



32. Quadrantal error introduced by Flinders bar 62 



33 Sphere slewing chart . 63 



34. Flinders bar correction curves 66 



35. Heeling magnet induction of Flinders bar 68 



36. Magnetic fields across compass needle arrays 69 



37. Arrangements of corrector magnets 70 



VI 



