DURING the past four years numerous experiments have been carried out which had in common the fact that a person subjected to a change in direction of resultant force relative to himself experienced an illusion. This consisted partly of a feeling of being tilted and of assuming a new position in space and partly of an impression that objects in the visual field moved and occupied new positions in space. These changes accorded more or less with the change in direction of the resultant force. The visual component of this phenomenon was called the "oculogravic illusion," and time has proved the usefulness of this descriptive term. Although this illusion has been known since the time of Mach,1 it has not been the object of intensive investigation. No attempt will be made to summarize past work in this field, since this has already been reviewed adequately in other places.2