The velocity of a steady, low-pressure ( ~0.1 Torr) plasma jet is measured by analyzing the local response of the medium to the action of an external magnetic field set up by two Helmholtz coils placed at the edge of the jet, yielding a field of 0.92 G/A. The induced electric field is measured by two floating-potential electrostatic probes. The mean velocity of the electrons (between 1000 and 5000 m s-t) is found from the generalized Ohm's law.