  We report on the direct observation of an oscillating atomic current in a
one-dimensional array of Josephson junctions realized with an atomic
Bose-Einstein condensate. The array is created by a laser standing-wave, with
the condensates trapped in the valleys of the periodic potential and weakly
coupled by the inter-well barriers. The coherence of multiple tunneling between
adjacent wells is continuously probed by atomic interference. The square of the
small-amplitude oscillation frequency is proportional to the microscopic
tunneling rate of each condensate through the barriers, and provides a direct
measurement of the Josephson critical current as a function of the intermediate
barrier heights. Our superfluid array may allow investigation of phenomena so
far inaccessible to superconducting Josephson junctions and lays a bridge
between the condensate dynamics and the physics of discrete nonlinear media.
