  We present radio emission, polarization, and Faraday rotation maps of the
radio jet of the galaxy 3C303.
  From this data we derive the magnetoplasma and electrodynamic parameters of
this 50 kpc long jet.
  For a {$\sim 2$} kpc segment of this jet we obtain for the first time a
direct determination of a {\it galactic}-scale electric current ($\sim 3 \times
10^{18}$ A), and its direction $-$ {\it positive} away from the AGN. Our
analysis strongly supports a model where the jet energy flow is mainly
electromagnetic.
