Taken from "Les situationistes et l'automation" by Asger Jorn. As the caption says in the document, this device allows to automatically trace a Gauss curve (end position of the balls that fall down). To Jorn, it can be used as a metaphor of moving in cities: the dérive [the situationiste practice of drifting through cities] can be represented as the unpredictable trajectories of the balls.