American Scientist the Magazine of Sigma Xi, the Scientific Research Society

A reprint from American Scientist the magazine of Sigma Xi, The Scientific Research Society This reprint is provided for personal and noncommercial use. For any other use, please send a request to Permissions, American Scientist, P.O. Box 13975, Research Triangle Park, NC, 27709, U.S.A., or by electronic mail to [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. Nowadays, ture, the magic lantern employed optics when I say I will be showing slides and to project through a lens system an en- will need a projector, just about everyone ry of the cave, in which prisoners could largement of an image painted on a glass assumes that I will employ a PowerPoint view only shadows cast on the wall that slide. The device’s origins are as fuzzy presentation, and that what I need is a they were constrained to view, can be as its first images must have been, but digital projector. Indeed, the conversion taken as a paradigm of the captive audi- primitive magic lanterns were employed from physical to digital “slides” has been ence. In Plato’s cave, the source of illu- as early as the 15th or 16th century. so rapid and complete that the Eastman mination was a simple fire strategically Giambattista della Porta, whose Magiae Kodak Company ceased manufacturing placed behind a bridge that served as a Naturalis first appeared in the mid-16th its classic projectors late last year and has stage over which actors crossed to cast century, described the process of using let it be known that it cannot guarantee the shadows that became the extent of a convex lens to focus the projected im- that parts or service will remain available the prisoners’ external reality. ages of transparent drawings. Further- after 2011. Thus, the once-ubiquitous 35- Natural phenomena also provided more, “To these drawings he attached mm slide projector will soon become a precursors to controlled projection. A movable parts, and thus produced as- museum piece. rainbow is just the sunlight behind us tonishing effects, which the unlearned refracted into its component colors by ascribed to magic, a term connected with Obligatory Obsolescence the spherical lenses of raindrops. The the lantern ever since.” (In the mid-19th Technology and its artifacts are always right natural conditions can also result century, when the magic lantern would being superseded, and the demise of the in the phenomenon of pinhole projec- reach a high level of sophistication, one Kodak slide projector signals the begin- tion, as when light rays cross as they lecturer would wish “that some more ning of the end of yet another chapter in pass through the chinks in tree cover scientific, if not so familiar, a name for the long history of using images to sup- to cast on the ground an image of the our instrument were recognised.”) plement words. Arguably, the earliest sun. Viewers of solar eclipses exploit the As is typical of a new technology, illustrated lecture was in effect a game same phenomenon, employing a pierced incremental improvements were soon of charades, with ideas communicated card, to view the celestial drama indi- made, and by the 17th century the de- through gestures. Hand shadows added rectly, so as not to endanger the human vice had been developed sufficiently illusion and broadened the repertory of eye. The camera obscura (a “dark cham- to be employed in scientific lectures to the hands themselves. Prehistoric cave ber” fitted with a small aperture through project microscopic and other images. painting may have been but an early which light can throw an outside im- Among scientists who were instrumen- means of illustrating lectures about bat- age onto an opposite wall), known at tal in such endeavors were Johannes tle and hunting strategies. Plato’s allego- least since ancient times, domesticated Kepler and Christiaan Huygens, who is the natural phenomenon and captured sometimes identified as the inventor of Henry Petroski is the Aleksandar S. Vesic Professor images of landscapes that artists could the modern magic lantern. The typical of Civil Engineering and a professor of history at trace. The contemporary artist David lantern of the time consisted of a cham- Duke University. Address: Box 90287, Durham, Hockney, joined later by the optical sci- ber that contained a light source, such NC 27708-0287 entist Charles Falco, has argued in recent as an oil lamp, whose heat and fumes © 2005 Sigma Xi, The Scientific Research Society. Reproduction 400 American Scientist, Volume 93 with permission only. Contact [email protected]. were dispersed through a chimney. The “limelight.” Image diameters of the or- ing such slides at Wellesley College dur- light was directed through a telescope- der of 60 feet dwarfed the lecturer, who ing the 1953–54 academic year.) like cylinder, which by the end of the often stood on the stage and used an Kodachrome film had been intro- 17th century typically held, in receding enormous wooden pointer to direct the duced in the mid-1930s, making pos- order from the light source, a condens- gaze of thousands of eyes to a detail. sible the 35-mm “color transparency” ing lens, a fixture by means of which By the end of the 19th century, magic slide. This was a lighter, more compact glass slides could be slid in and out of lanterns had in their own right become (2-inch square) and shatterproof alter- the light path, and a native to the 3-1/4-inch moveable objective lens square British and the 3- for focus. The size of the 1/4-by-4-inch American image was controlled glass lantern slide, but it by the distance of the was also a more expen- lantern from the surface sive one. Still, some art on which it was to be historians insisted that projected. the smaller slides simply The use of the in- did not provide as sharp strument for popular an image as glass lantern entertainment grew in slides, and so they, like the the late 18th century, Wellesley instructor, con- when it began to be tinued to use the old but employed to produce arguably superior technol- shows known as phan- ogy. With the introduction tasmagoria (literally, “a of Kodachrome II film and gathering of ghosts”). To then the Kodak Carousel maximize its effective- projector in 1961, howev- ness, the phantasmago- er, the days of the magic ria lantern was often a lantern and its glass slides lightweight model made were numbered. of tin painted black and with a crooked chimney. Projecting Overhead These features enabled Not all lectures or presen- the handheld lantern tations require high-qual- to be moved about a ity photographic slides. totally darkened room Especially for situations without being readily that relied more on pic- seen, whereby the pro- tures as diagrams and jected ghostly images freehand sketches, the appeared to hover and development of the over- move by themselves. By V&A Images/Alamy head projector provided the middle of the 19th The magic lantern was developed in the 15th or 16th century and evolved con- a quick and easy alterna- century, magic lantern siderably over subsequent centuries. This one was made in Germany in the tive to slides. An early 19th century. shows of all kinds had version of the overhead become popular sources of education, objects of beauty and complexity, fash- projector (in the form of a reconfigured edification and entertainment to which ioned out of brass and glass that shined magic lantern) existed around the turn admission was charged. The develop- and glittered. At the same time, a new of the 20th century, but more modern ment of photography led to the print- technology began to be introduced, that ones date from the mid-1940s, when ing of photographic images directly onto of the motion picture, which would re- they were introduced as an aid in po- glass plates, which when sandwiched place the public lecture as a means of lice work. They soon found their way together with a second glass plate bound mass entertainment. At first, magic lan- into bowling alleys and schools, where to the first produced durable slides. Itin- terns continued to be used in conjunction they were used to project scores and erant lecturers, who traveled with their with the movie projector, to show titles lessons as they were written down in magic lanterns the way magicians do and advertisements while reels were be- real time.

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