The geomagnetic field variation spectra for the period range of 5 min to 4 hours were analyzed at 64 world observatories to discover systematic behavior in the spectral composition that could be associated with the time of day, season, solar cycle, activity level, component direction, and geographical location of the station. There was found no consistent frequency location for peaks in the spectral composition. Rather, the displays of spectral amplitudes A were mostly 'linear' in form, often obeying A~Tm, where T is the period. The spectral slope m was usually close to 1.0 but varied at times from 0.5 to 2.0. The amplitudes always showed a maximum at the auroral zone latitudes, a minimum near 20¿--40¿, and a minor maximum near the equator. The positions shifted equatorward with increasing activity. The relative growth in amplitude with rising activity varied with latitude. Seasonal peaks in activity were found at equinoctial months. A summertime minimum occurred at auroral zone stations; elsewhere a summertime enhancement occurred. General findings emphasizing the North American hemisphere and the year 1965 are presented in a number of tables and graphs.