The evidence for the existence of winds in the ionosphere is now manifold. It is partly directly visual, from the motion of luminous meteor trails and high luminous night clouds and patchiness in the night airglow. It is partly based on inference from indirect observations, such as the geomagnetic variations at the earth's surface; these are ascribed to electric currents partly flowing in the ionosphere, which are explained by dynamo action of ionospheric motions. Another type of indirect observational evidence is provided by the scintillation of radio stars. The most abundant and varied evidence, however, is afforded by inference from observations in which human experiment also plays a vital part, namely by the transmission of radio beams to the ionosphere and their reception after they have been modified by passage through that region, either solely by the influence of ionospheric motion, or by the fleeting presence there of ionized meteor trails.