The mechanical force on bodies of small susceptibility due to induced magnetization

The mechanical force on a body of any shape and of small susceptibility, when placed in a magnetic field, is expressed as an integral taken over the surface of the body. This principle is applied to the experimental arrangement adopted in Rankine's magnetic torsion balance, where a magnetic pole is attracted by the magnetization induced in a spherical body. The results obtained are (1) a direct proof of Rankine's formula for a point pole; (2) the correction for the earth's field; and (3) the correction for the finite spread of the poles in an actual magnet.