 Meanwhile, by April 1822, Fresnel accounted for the directions and polarizations of the refracted rays in birefringent crystals of the "biaxial" class — a feat that won the admiration of Pierre-Simon Laplace.At the end of a memoir on stress-induced birefringence read in September 1822, Fresnel proposed an experiment, involving a Fresnel rhomb, for the purpose of verifying that optical rotation is a form of birefringence.This experiment, like the one he had just performed on stress-induced birefringence, required a row of prisms with their refracting angles in alternating directions, with two half-prisms at the ends, making the whole assembly rectangular.