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[email protected]. ©Sigma Xi, The Scientific Research Society and other rightsholders Engineering Next Slide, Please Henry Petroski n the course of preparing lectures years—against strong opposition from Ibased on the material in my books As the Kodak some in the artistic community—that and columns, I developed during the simple projection devices were used by closing decades of the 20th century a the masters to trace in near exactness good-sized library of 35-millimeter Carousel begins its intricate images, including portraits, that slides. These show structures large and the free hand could not do with fidelity. small, ranging from bridges and build- slide into history, ings to pencils and paperclips. As re- The Magic Lantern cently as about five years ago, when I it joins a series of The most immediate antecedent of the indicated to a host that I would need modern slide projector was the magic the use of a projector during a talk, just previous devices used lantern, a device that might be thought about everyone understood that to mean of as a camera obscura in reverse. Instead a Kodak 35-mm slide projector (or its to add images to talks of squeezing a life-size image through a equivalent), and just about every venue pinhole to produce an inverted minia- had one readily available.