112 HANDBOOK OF MAGNETIC COMPASS 



pass material found defective shall be immediately surveyed. An 

 inventory of compasses, form NBS 1107, shall be filled out and 

 sent to the Bureau of Ships on June 30 of each year, and by new 

 ships as soon as practicable after commissioning. Copies of this 

 inventory shall be pasted in the back of this Record Book. An 

 inventory of navigational instruments, form NBS 1108, shall be 

 filled out and sent to the Bureau of Ships on June 30 of each 

 year. 



"4. When a vessel is newly commissioned, all the compasses shall 

 be approximately compensated. At the first opportunity after 

 commissioning the ship shall be swung for deviations, as follows : 

 First, with all correctors removed; second, after adjusting, with 

 degaussing coils off; third, with degaussing coils on, and no de- 

 gaussing compensation coils operating; fourth, with degaussing 

 coils on and compensating coils in adjustment. A complete anal- 

 ysis of the deviations of all compasses installed shall be made, both 

 before and after adjustment, and a complete report forwarded on 

 forms NBS 1102 and NBS 1106 to the Bureau of Ships. 



"5. Similar observations and reports shall be made when on 

 or near the magnetic equator, and data for the installation of 

 Flinders bars obtained. 



"6. Similar observations and reports shall be made as soon as 

 possible after any considerable change in the magnetic state of 

 the ship which may be caused by any of the following : Flashing, 

 wiping, deperming, major alteration or repair of hull structure 

 or machinery, firing of main-battery guns, lying in the same direc- 

 tion for a period of two or more weeks, or after making a passage 

 during which the same course has been steered for a week or 

 more. In particular, for about thirty days after flashing or 

 wiping, the magnetic state of the vessel will change slowly. It 

 is, therefore, necessary not only to adjust immediately after 

 flashing or wiping, but also to obtain and record deviations at 

 approximate 10-day intervals for thirty days, and to readjust as 

 soon thereafter as possible. 



"7. All compasses shall be kept as closely adjusted as prac- 

 ticable. Every effort should be made to swing ship for residual 

 deviations of all compasses at least once in three months. The 

 results, properly recorded on forms NBS 1102 and NBS 1103, 

 shall be entered in the Compass Record. Deviation tables on 

 form NBS 1105 for the standard, battle, maneuvering and auxili- 



