Changes in the phase delay of a ducted whistler mode signal from the Siple Station VLF transmitter to a receiver at Roberval, Quebec, are compared to variations in the horizontal components of the Earth's magnetic field measured nearby at La Tuque, Quebec. The VLF transmission contains 10.5 min of two distinct tones with 30-Hz separation. Each tone suppresses the cyclotron-resonance growth of the other, eliminating growth-associated phase effects, and allows phase changes due to radial duct motion to be observed. Spectrograms of the VLF phase delay and variations in the components of the geomagnetic field show similar features, with phase features preceding magnetic features by 20 to 30 s. A cross-correlation plot of VLF phase delay and variations in the east-west component shows a bipolar signature which is interpreted as evidence of transient hydromagnetic waves in the 20--45 s band (Pc 3 band) moving from equator to ground. Previous studies have noted correlations between VLF Doppler shifts and resonant hydromagnetic waves, but this is the first report where the VLF phase delay is used directly, and where resolution is sufficient to observe a transient hydromagnetic wave which has a parallel wavelength shorter than the length of the field line. ¿ American Geophysical Union 1990