ADJUSTMENT PROCEDURE 59 



card at this time. Chapter IX discusses these many sources of error 

 in detail. 



If the Flinders bar adjustment is not based on accurate data, as with 

 a new ship, it would be well to exercise particular care in recording the 

 conventional Daily Gompass Log data during the first cruise on which 

 a considerable change of magnetic latitude occurs. 



90. In order to have a reliable and up-to-date deviation card at all 

 times it is suggested that the ship be swung to check compass deviations 

 and to make readjustments, if necessary, after : 



(1) Eadical changes in magnetic latitude. 



(2) Deperming, flashing, or wiping. (Delay adjustment sev- 

 eral days, if possible, after such treatment.) 



(3) Structural changes. 



(4) Long cruises or docking on the same heading such that the 

 permanent magnetic condition of the vessel has changed. 



(5) Magnetic equipment near the binnacle has been altered. 



(6) Reaching the magnetic equator, in order to acquire Flinders 

 bar data. (See ch. VIII.) 



(7) Every 3 months, to account for magnetic decay, etc. 



(8) Appreciable change of heeling magnet position if Flinders 

 bar is present. 



(9) Readjustment of any corrector. 



(10) Change of magnetic cargo. 



(11) Commissioning. 



With such reasonable care, the compass should be a reliable instru- 

 ment requiring little attention except for occasional refinements of the 

 heeling magnet position as the ship changes magnetic latitude. 



