Continuous series of tide records from 1905 to 1956 at San Francisco and Honolulu were reduced to smoothed values at 32-hour intervals. The cross spectrum of the resulting seri es was computed by the Tukey method for 750 narrow-frequency bands at intervals of 0.0005 cycles per day. The curves of spectral-energy density vary smoothly with frequency; the only significant peaks occur at tidal frequencies....