  Capillary waves excited by the vertical oscillations of a thin elongated
plate below an air-water interface are analyzed using time-resolved
measurements of the surface topography. A parametric instability is observed
above a well defined acceleration threshold, resulting in a so-called
cross-wave, a staggered wave pattern localized near the wavemaker and
oscillating at half the forcing frequency. This cross-wave, which is stationary
along the wavemaker but propagative away from it, is described as the
superposition of two almost anti-parallel propagating parametric waves making a
small angle of the order of $20^\mathrm{o}$ with the wavemaker edge. This
contrasts with the classical Faraday parametric waves, which are exactly
stationnary because of the homogeneity of the forcing. Our observations suggest
that the selection of the cross-wave angle results from a resonant mechanism
between the two parametric waves and a characteristic length of the surface
deformation above the wavemaker.

Pattern Formation and Solitons;Other Condensed Matter