[en] The line-centre magnetogram technique has been used to study velocities at spatial scales > approximately 5'' in several umbras without interference from light scattered from the surrounding non-magnetic photosphere. In addition, more traditional velocity observations of one sunspot were also analysed. The velocities are highly variable within any spot and from one spot to another. Rms velocities in Hα, b₁, 5233 and 5166 A were typically +-0.6, +-0.2₀, +-0.1₀, and +-0.1₇ km s^-1 during present observations, but factors of 2 smaller or larger are not uncommon. In 5166 and 5233 A these velocities are about two-thirds of those in non-magnetic photospheric regions. In Hα there are umbral intensity variations whose maxima at Δlambda=+-0.39 A occur simultaneously with downward velocity maxima measured at the same Δlambda. Intensity maxima at line centre lag by 12 s, demonstrating that there are waves propagating upwards. The corresponding height difference, 60-70 km at the velocity of sound, requires excitation of Hα at much higher levels in the umbral atmosphere than if in LTE. (Auth.)