The dip needle is an instrument that has an established field of usefulness in working out the geologic structure of poorly exposed areas containing magnetic formations. However, its usefulness is decreased by the fact that the readings measure no one component of the earth's magnetic field, but reflect the combined effects of changes in both the inclination and the intensity. Thus the dip needle is not a magnetometer as ordinarily used. But, by taking two sets of readings, one may calculate from them the horizontal and vertical components of the magnetic field, and the dip needle becomes a horizontal and vertical magnetometer. This paper is an account of investigations conducted with the object of testing the practical usefulness of the dip needle as a magnetometer along the lines suggested above.