This book is a monograph on the topic of double refraction, a phenomenon in optics whereby a single light ray is split into two rays of differing polarizations. The author explains the theory of French physicist Augustin-Jean Fresnel, who proposed a model to explain this phenomenon involving the existence of two rays with perpendicular polarizations. The book includes mathematical derivations and some discussion of experimental evidence. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.