Abstract: A linkage for controlling the motion of a member reciprocated in substantially a circular arc. The linkage comprises a shaft rotatable in alternate directions between first and second positions, an arm secured to the shaft for rotation therewith and a member pivotally connected to the arm at a first location spaced from the shaft. A radius arm is mounted on the shaft for rotations relative thereto, the radius arm having a sliding connection with the member at a second location spaced from the shaft and from the first location. A stop means limits movement of the radius arm to an arc less than the arc between the first and second positions of the shaft.The linkage is particularly adapted to control the motion of a wiper blade in a wiper assembly for the rear window of a vehicle.