It has been noticed that the magnetic field observed at a house newly built often drifts several gammas in one or two years. Influence of soil on observations of the earth's magnetic field is examined at the Mizusawa Geodetic Observatory with a hope of explaining this variation by possible realignment of magnetic mineral grains contained in soil under the influenced of the earth's magnetic field and rain water. From the experiments in the past two years, the results are rather negative. Realignment effect is too small, even though it cannot be completely disregarded.