Detailed study of two Pc 1 hydromagnetic emission events observed at Great Whale River, Quebec; Boulder, Colorado; and College, Alaska, indicates that emission energy propagated westward in an ionospheric duct from an extended source region east of Great Whale River with duct velocities ranging from 500 to 2500 km s-1. Sources located using both triangulation direction of arrival and polarization techniques were found to be generally consistent. Autocorrelation measurements of fine structure element spacing within the events show that dispersion increased with longitudinal distance from the source.