  We report on what is to our knowledge the first scattering experiment of
surface waves on an accelerating transcritical flow, which in the Analogue
Gravity context is described by an effective spacetime with a black-hole
horizon. This spacetime has been probed by an incident co-current wave, which
partially scatters into an outgoing counter-current wave on each side of the
horizon. The measured scattering amplitudes are compatible with the predictions
of the hydrodynamical theory, where the kinematical description in terms of the
effective metric is exact.
