The Rotary Demisphere is one of Marcel Duchamp’s experiments in optical devices, designed to create sensational illusions. The rotating disk could have any number of spiraling plates attached to it, and rotated at high speed to create a variety of effects. The copper ring around the dome’s circumference is engraved a French phrase, chosen for the way their sounds echo one another: Rose Selavy et moi esquivons les ecchymoses des esquimaux aux mots exquis (Rose Selavy and I dodge the Eskimos’s bruises with exquisite words).
