The correction of ships´ magnetic compasses for the effects of degaussing

The necessity for compass-corrector equipment is explained, and it is shown how this was developed after it had been ascertained that D.G. coils produced a linear effect at the compass position. The correction was applied by means of air-cored coils attached to the compass binnacle, and supplied with voltage proportional to the current in each D.G. coil. The corrector coils were arranged to correct three mutually perpendicular components of magnetic field. A brief indication is given of the methods adopted for minimizing compass troubles caused by ¿wiping¿ and ¿flashing.¿