Abstract
As well known, a ship's compass has an error known as the deviation of the compass, which arrises from the effect exerted upon it permanently or transiently by masses of magnetic metal within the shipitself. The deviation changes with change in latitudes, concretely the values of coefficients B and C changes except the case when the ship is heeling. When Oshoromaru, the training-ship of Hokkaido university went to the southern fishing grounds January 1955, we measured the change of the deviation about her standard compss. We obtained the variations 5.73° and 2.04° for coefficients B and C respectively, with change in latitudes, namely from magnetic laltitude 56°N to magnetic equator. From thesse measured values next most probable values for several important coefficients were got. P=-0.107±0.001 c=+0.037±0.004 Q=-0.010±0.005 f=-0.009±0.001
