Within two years after da Vinci’s death two other Italians, Maurolico and Cesariano, advanced the magic shadow art-science by writing scientific and experimental discussions of the subject. Somewhat later another Italian, Cardano, made another contribution. Francesco Maurolico (Maurolycus), 1494–1575, a mathematician of Messina, and the great astronomer of his day, wrote _De Subtilitate_, about 1520, in which Pliny, Albertus Magnus, and Leonardo da Vinci are mentioned. The material included a mathematical, rather than experimental, discussion of light, mirrors and light theatres. This last subject shows that the use of light and shadow for theatrical purposes was being rapidly advanced. In 1521, Maurolico was said to have finished _Theoremata de lumine et umbra ad perspectivam et radiorum incidentiam facientia_, which was published in 1611 at Naples and in 1613 at Leyden. This book explained how a compound microscope could be fashioned. Men were now learning how to use lenses and how to make better ones so necessary for satisfactory projection of images. [Illustration: Ars Magna Lucis et Umbrae, 1646 _BURNING GLASSES of Archimedes were ancient optical devices. They were used in the defense of Syracuse in 212 B. C. Some type of glass or lens is required in every camera or projector._] Proposition 20 of the book was entitled “An object’s shadow can be converted and projected.” The author pointed out that if an object between a light and an opening is moved one way its shadow appears to move the other. He then went on to explain the reasons for Aristotle’s square hole and round sun. He also showed accurately the relation of images and objects which was fundamental for understanding how to focus lenses and mirrors. [Illustration: Self portrait. Royal Palace, Turin _LEONARDO DA VINCI, famed Renaissance painter and sculptor, explained how to use the camera and described its relationship to the human eye._] Later astronomers credit Maurolico with having described the application of the _camera obscura_ method to an observation of eclipses (but this was done for the first recorded time by Bacon or his contemporaries). Maurolico knew the works of Bacon and John Peckham, another English Franciscan monk of the 13th century, and studied both carefully. In 1535 he wrote _Cosmographia_ and in later life studied the rays of light that make the phenomenon of the images appearing in a _camera obscura_, or any camera, possible without mentioning the apparatus or device or describing it. Being a mathematician primarily he was interested in that side of the problem and was not a practical demonstrator or showman.