488604 Roger Bacon (litho) by Bayard, Emile Antoine (1837-91); Private Collection; (add.info.: Roger Bacon (c.1214-94) English philosopher and Franciscan friar; emphasized the need to study nature through empirical methods; critic of the Julian calendar system and is considered the first European to describe the elements contained in gunpowder; his study of optics in \'Opus Maius\' owes much to the work of Claudius Ptolemy and the Islamic scientists, Alkindus and Alhazen; also wrote on alchemy; after his death his learning led to his being called \'Doctor Mirabilis\' (\'Wonderful Doctor\');); French, out of copyright.