Signals propagating from the Siple, Antarctica, VLF transmitter to the conjugate station at Roberval, Quebec, Canada (L~4.2), are generally multipath in nature. From previously reported initial observations at Roberval with a tracking receiver/direction finder (TR/DF) it was found that the directional properties of the received signals were stable for only minutes at a time, compared to the tens of minutes that had been expected from earlier dispersion analyses of whistlers. This effect was further investigated in the present study of TR/DF observations of multipath Siple signals in 1977. In a case study from May 20, 1977, the TR/DF consistently obtained directional information on the arrival bearings of multipath signals whose amplitude at the receiver was ~5 dB or more above that of other signals within the 340-Hz passband of the frequency-tracking filter. It was found that the arrival bearing of the strongest signal shifted widely within minutes. The sequence of shifts over a 1-hour period, coupled with the occasional appearance of power line radiation activity, may possibly be induced by the eastward gradient drift of low-energy (?1--2 keV) 'clouds' of electrons through a pattern of whistler ducts. This interpretation was suggested by the rapidity (~10--100 s) with which signal amplitudes rose and fell by greater than ~10 dB on individual paths. The sudden turn-ons and turn-off s are tentatively attributed to the 'threshold' effect being reported elsewhere, in which temporal growth of Siple transmitter signals suddenly occurs as the amplitude of the injected waves reaches a particular level. In the present case the phenomenon is believed to occur at constant wave level as the result of changes in particle flux associated with drifting structure in the low-energy electrons. Other effects observed in the primary case study were a slow northward movement on a time scale of about 30 min of the bearing of the stronger signals. This movement is believed to be associated with quiet-day convection. Also observed were small-scale (Δϑ~10¿-20¿) fluctuations on a time scale of several minutes in the arrival bearing of signals from a particular path. These fluctuations may be due to a temporal modulation of propagation conditions between the 'end' of magnetospheric ducts and the lower boundary of the ionosphere.