Abstract: Windmill apparatus comprises an open framework defining a wheel having means defining a pivot axis and embodying a plurality of radially and closely spaced concentric rows of air foils. The foils in each row are connected for their conjoint movement to and from a pre-set operating position, within defined limits. The movement of each foil is about an axis which is substantially radial to the wheel and it is arranged to automatically feather when subject to impact of winds the speed of which is at a dangerous level. As oriented in the wheel the radial extremities of each foil are substantially flat and bridged by a continuous peripheral surface portion. One portion of said peripheral surface portion is flatted to define the operating face of the foil. The flatted portion is preferably comprised of two planar surface portions one of which leads the other, having regard for the facing of the foil operating surface into the prevailing wind.