The causes of various traits of the polar motion are still unknown or uncertain. For exploring these the Chandler nutation has the advantage of being readily observable and it should be independent of external torques. This nutation shows a prograde motion of the earth’s axes of rotation and of excitation about each other. For simplicity the positions of the poles of rotation P and excitation ψ (Munk & MacDonald, 1960) are given in terms of dimensionless excitation functions which apply in principle whether they come from distributions of mass, relative motions or torques. Let O be the pole of zero excitation and R be the angular distance between P and ψ.