The water of a fall, which sets in motion a miller's wheel, zigzags gently down through a gutter between two towers till it reaches the point from which it drops down again. The miller can keep it in perpetual motion by adding a bucket of water now and then to compensate for evaporation. The towers are equally high, yet the left one is a story higher than the other. The polyhedrons on their top have no special significance. I have put them there simply because I like them so much: to the left, three intersecting cubes, to the right, three octahebrons.
The background is a southern Italian terraced landscape, and the lower left corner is filled with greatly enlarged moss plants. The cups are, in reality, only about a tenth of an inch high.
The theme of this self-supporting waterfall is based upon the triangle ... of Roger Penrose, a son of the inventor of the "continuous stair" in "Ascending and Descending". It is perhaps worth-while to quote his article in "The British Journal of Psychology", February 1958: "Here is a perspective drawing, each part of which is accepted as representing a three-dimensional, rectangular structure. The lines of the drawing are, however, connected in such a manner as to reproduce an impossibility. As the eye pursues the lines of the figure, sudden changes in the interpretation of distance of the object from the observer are necessary" [M.C. Escher]
