  We present abundance measurements, based on high-resolution optical
spectroscopic data obtained with the Ultraviolet and Visual Echelle
Spectrograph mounted on Kueyen (Very Large Telescope UT2), for ten stars in the
extended blue horizontal branch of the Galactic globular cluster NGC 1904
(M79). In agreement with previous findings for other clusters, we obtain normal
abundances for stars cooler than Teff ~ 11,000 K and largely anomalous
abundances for hotter stars: large He depletions, and overabundances of Fe, Ti,
Cr, P and Mn. The abundances of Mg, Si and Ca are roughly normal, in the hot
stars as well as in the cooler ones. This abundance pattern can be attributed
to the onset of diffusion and to radiation pressure in the stable atmospheres
of hot horizontal branch stars.
