My fIrst encounter with the name of William Charles Wells, over twenty years ago, was an oblique reference to his Essay upon single vision that Wheatstone (1838) made in a classical article on binocular vision. The reference was enigmatic because it stated that few had paid attention to Wells' theory of visual direction, while doing little to infonn the reader of its novelty. I was fortunate in having the excellent facility of the Rare Books and Manuscripts...