abstract: It is well known that Descartes believed celestial bodies to be carried around by whirlpools of a fluid, subtle matter. In order to illustrate his vortex theory, he often compared the behavior of planets in the sky to that of bodies in water like barges carried by a river’s current or balls caught in a vortex. In my lecture I shall analyze some of Descartes’ explanatory models and pay particular attention to their mutual incompatibility.