The spectrum of the variation in latitude

A Fourier series analysis of the motion of the Earth's rotation axis in the frequency range 0.74 to 1.14 cycles per year, containing 9pct of the total power in the motion, shows: (1) an annual line without recognizable structure comprising about 2pct of the power in the region examined; (2) the Chandler component comprising about 7pct of the power, with band structure somewhat broader than heretofore recognized, leading to a value 9.5 yr for the amplitude decay time; (3) an annual component of excitation in agreement with previous determinations, equivalent to a root‐mean‐square displacement of the axis of inertial symmetry of 0.023″ of arc; (4) a continuous spectrum of excitation which is well determined in the Chandler region, at least roughly determined at other frequencies below annual, but not determined above the annual frequency. The magnitude of the continuous spectrum below annual frequency is consistent with the hypothesis that it, in association with the annual line, arises in the atmosphere, but lack of a determined spectrum at higher frequencies prevents examination of side‐band symmetry.