A survey of Renaissance lore regarding magnifying mirrors and lenses.
Reeves (Comparative Literature/Princeton Univ.) is more interested in what Galileo and his contemporaries believed about telescopic vision than in the actual process of discovery that led to his adoption of the telescope for astronomical observations. As the author shows, the idea of telescopic vision can be traced to ancient civilizations. The Pharos lighthouse in Alexandria was said to have a mirror in which the keepers could see the enemies of the city approaching from long distances. The Pharos mirror was also supposedly capable of setting ships ablaze by concentrating the sun’s rays. It was variously described as magical and simply physical, and many of its properties, notes Reeves, can be found in descriptions of other semi-mythical mirrors, built by (or for) many powerful historical figures including Julius Caesar, Virgil, Roger Bacon and John Dee. The author quotes a number of Galileo’s contemporaries or immediate predecessors who claim they had made—or were working on—mirrors with similar properties, sometimes in combination with lenses. This flood of information—some of it merely mistaken, some outright fraudulent—is largely responsible for Galileo’s delay in following up accounts of the real telescope developed by Dutch lensmakers. Reeves also argues that obscure language in several texts led Galileo and his contemporaries to believe that the Dutch telescope used mirrors, not lenses, to achieve its effect. In fact, a confusion of reports, some by Galileo’s rivals, has obscured the exact history of Galileo’s own adoption of the telescope. A satire by Ben Jonson, for example, improbably portrays the Italian astronomer as an ally of the Jesuits, using his telescope to burn attacking ships.
A bit dry, but scattered with intriguing nuggets.