We present accurate measurements, based on the g = 3 line at 1.5648/µm, of the field strength and longitudinal velocity in the vicinity of the magnetic neutral-line of a solar active region. We find that very close to the neutral line the field strength and the flow velocity are correlated in the sense that the magnetic polarity with the larger field strength is associated with a downflow, while the polarity with the weaker field shows an upflow. This is exactly the signal predicted by theoretical models of siphon flows, and constitutes the first reliable detection of a siphon flow on the sun.
