It involves the determination by experiment of--( a) the product of the magnetic moment, M, of the magnet by the horizontal component, H, of the earth's magnetism; (b) the quotient of M divided by H. Knowing these two quantities, M is given by the formula M = SquareRoot( )M * H) * (M/H) ) and if desired H is given by the formula H = SquareRoot( (M*H) / (M/H)).
M*H is determined by the method of vibrations. A very long, thin magnet suspended by a torsionfilament is caused to oscillate, and its period is determined. Calling such period T and the moment of inertia of the magnet I, we have the formula T= 2* PI * SquareRoot( I / (H*M) ) (a), whence H*M is calculated, I of coursebeing known or separately determined.
Definitions of magnetometry
