Abstract
Non-rigid effect on the rotation of the earth is studied by a mathematical model of resonance raised in the free nutation by an assumed forced oscillation of the moments and products of inertia of the earth. It is shown that the Euler period of the rigid earth shifts to the Chandler period if the assumed oscillation has an amplitude of 10-9C. In general, however, the Chandler period changes slowly about its mean value. Corresponding to this change, the radius of the polar motion changes too.
