Just as the inventor played with materials, he played with ideas, suspending his critical faculties during the earliest stages of invention. In an era before photocopying machines he developed an electric "pen"--really a puncturing device that rapidly punched holes in a sheet of waxed paper, which then served as a stencil for generating more copies. To make the point of the pen vibrate up and down, Robert Rosenberg, the project director, reports, Edison came up with concepts that "ranged from the practical to the absurd." Rosenberg reviewed a series of drawings showing how the point might be set in motion by a treadle mechanism reminiscent of an early Singer sewing machine, by little waterwheels attached to the end of the shaft, by air pumps, or by an electric motor tethered to the operator's wrist.
Part of the impetus for Edison's dogged search for alternative solutions to problems was his wish to cover himself with as broad a patent as possible. But the project historians emphasize that Edison also simply exulted in the challenge of inventing. It was a test of his ingenuity--almost a matter of pride--to see how many possibilities he could come up with.
Although he cast a wide net initially, Edison would gradually become more focused in his thinking. As his understanding of a problem grew, he typically devised theories, tested them, and then narrowed the range of potential solutions. Still, his inventive process at no stage resembled the linear, step-by-step progression that the scientific method is supposed to be. Just when he appeared to be putting the finishing touches on an invention, Edison would often go back and review his earlier sketches to see if, in the light of the new knowledge he had acquired, abandoned ideas could be resurrected.
A single page from Edison's notebooks beautifully captures his remarkable facility for mixing and matching concepts. It shows three different designs for recording sound, from the time Edison first displayed his phonograph. Those pictures foretell the main directions the recording industry would take throughout the first half of the twentieth century.
One sketch, illustrating the design Edison went on to market commercially, shows a stylus pressed against a cylinder resembling a rolling pin. The so-called "cylinder phonograph" derived directly from a cylinder version of his recording telegraph. A second drawing features a grooved disc not unlike an LP record; it sprang from the basic version of his telegraph recorder, the device that led to the discovery that sound could be captured on paper or foil. The third drawing foreshadows the tape recorder, with paper tape running under a stylus. The project scholars believe that Edison got this idea from his work on earlier printing and chemical telegraph systems, which had similar configurations.
A closely related observation of the scholars--one with exciting implications for school-based programs aimed at cultivating innovative minds--is that Edison employed similar problem-solving strategies across numerous technologies. Notably, he reasoned by analogy, with a distinctive repertoire of forms, models, and design solutions that he applied to invention after invention. Reese Jenkins, who assembled and until last year headed the Edison Papers Project staff, calls these repeating motifs in Edison's work "theme and variations."
To illustrate Edison's brand of logic, Jenkins holds up one of his first drawings of the kinetoscope, a prototype motion-picture camera. "Notice any similarity to his wax-cylinder phonograph?" he asks.
The resemblance is obvious. Both phonograph and kinetoscope consist of an axle supporting a cylinder that has information (either a sound recording or a sequence of still photos) wound along its length. Each device also has a long thin instrument (a stylus in the case of the phonograph and a viewing apparatus in the case of the kinetoscope) held perpendicular to the surface of the cylinder.
Not surprisingly, these forms had a common origin. While Edison was working on an improved model of the phonograph in 1888, Jenkins reports, he was paid a visit by the photographer Eadweard Muybridge, who brought with him some of his famous still photos of animals in motion. Inspired by these images, Edison began to think about developing a moving picture in tandem with his other project. Jenkins finds evidence of a conceptual link between the two inventions in a patent caveat Edison drafted later that year, in which he announced, "I am experimenting upon an instrument which does for the eye what the phonograph does for the ear." He went on to describe the parallel between the spiral of images that make up what we now call film and the spiral grooves on the phonograph record.
The motion-picture camera that evolved from Edison's kinetoscope ultimately abandoned the cylinder in favor of reels of film, thus concealing from generations of scholars its close kinship to the phonograph. "If we hadn't looked at his notebooks and draft caveats," Jenkins points out, "we'd never know what the original impetus for the idea was."