_Photographic Journal_, including the transactions of the Royal Photographic Society of Great Britain. London. _Photographic Journal of America._ Philadelphia. CHAPTER I ARISTOTLE. _Problems._ _On Dreams._ EUCLID. _The Elements of Geometrie_ translated by H. Billingsley. London, 1570. _La Prospettiva di Euclide._ Florence, 1573. LUCRETIUS, _De Rerum Natura._ PTOLEMY (CLAUDIUS PTOLEMAEUS). _Ptolemaei Mathematicae._ Wittenberg, 1549. _Almagest._ Edited by J. Baptiste Ricciolus, S. J. 1651. ALHAZEN. _Opticae Thesaurus Alhazeni Arabis._ Basel, 1572. CHAPTER II ROGER BACON. _Fr. Rogeri Bacon Opera Quaedam Hactenus Inedita._ J. S. Brewster. London, 1859. _The Opus Majus of Roger Bacon_, edited with an introduction and analytical table by John Henry Bridges. Oxford, 1897–1900. _Letter concerning the marvelous power of art and of nature, and concerning the nullity of magic._ Translated from the Latin by Tenney L. Davis. Easton, Pa., 1923. _Part of the Opus Tertium_ of Roger Bacon, including a fragment now printed for the first time, edited by A. G. Little. Aberdeen, 1912. PIERRE MAURICE MARIE DUHEM. _Le Système du monde_, histoire des doctrines cosmologiques de Platon à Copernic. Paris, 1913–1917. WITELO. _Vitellionis Turingopoloni Libri X._ Basel, 1572. _Vitellionis Mathematici Doctissimi_ Περὶ Ὀπτικῆς. Nuremberg, 1535. CHAPTER III LEONARDO DI SER PIERO DA VINCI. _A Treatise of Painting._ Translated from the original Latin. Paris, 1651. _The Life of Leonardo da Vinci_ done into English from the text of the second edition of the “Lives” (by Giorgio Vasari) with a commentary by Herbert P. Horne. London, 1903. _The Literary Works of Leonardo da Vinci_, compiled and edited from the original manuscripts by Jean Paul Rickter. London, 1880–1883. _Essai sur les ouvrages physico-mathématiques de Léonard de Vinci_, avec des fragmens tirés de ses manuscripts apportés de l’Italie. Giovanni Battista Venturi. Paris, 1797. GUILLAUME LIBRI. _Histoire des sciences mathématiques en Italie_, depuis la renaissance des lettres jusqu’à la fin du dix-septième siècle. Paris, 1838–1841. GIORGIO VASARI. _Lives of Seventy of the Most Eminent Painters, Sculptors and Architects._ Edited by E. H. and E. W. Blashfield and A. A. Hopkins. New York, 1896. FRANCESCO MAUROLICO. _Cosmographia._ Venice, 1543. _Theoremata de Lumine, et Umbra, ad Perspectivam & Radiorum Incidentiam Facientia._ Leyden, 1613. GIROLAMO CARDANO. _De Subtilitate._ Nuremberg, 1550. _Les Livres de Hierome Cardanus Médecin Milannois._ Richard Le Blanc. Paris, 1556. CHAPTER IV