Doctor Wood. Modern Wizard of the Laboratory: The Story of an American Small Boy Who Became the Most Daring and Original Experimental Physicist of Our Day-but Never Grew Up

With sodium vapor, and also with iodine and mercury vapor, Wood was soon getting hitherto unknown types of spectra. His results gave the theoretical physicists immediate sharp pain and anguish. Without having asked their permission, this troublesome young experimenter had increased the number of spectrum lines in the principal series of sodium from the eight previously known to forty-eight, and had found a band of continuous absorption in the ultraviolet region. On the theory current at the close of the nineteenth century, each spectrum line was supposed to be emitted by a separate “vibrator” in the atom; or, as Darrow expressed it, an atom was regarded as being analogous to a clarion of bells. Rowland himself once said that the iron atom must be regarded as more complicated than a grand piano. Wood’s results made a further complication, and it was not until Niels Bohr in 1913 formulated our present theory of the nature of the atom that Wood’s results could be explained; and in Bohr’s first paper on the subject he cited Wood’s work on sodium as the most perfect confirmation of his theory of atomic radiation.

It was in Madison that Wood started another line of special interest in his field that was to stick with him for life. He became interested in the construction and uses of diffraction gratings. These are plates of glass or metal upon which have been ruled a large number of fine lines (sometimes as many as thirty thousand to the inch). Diffraction gratings perform the same function as prisms, dispersing light into its components, and for many kinds of spectroscopic work are greatly superior to prisms. Naturally their construction is a delicate task. The great Rowland made the finest gratings of his time in his laboratory at Johns Hopkins, and Wood was later to carry on and improve Rowland’s process at that institution. And as I write this he is getting ready to go to California with his chef d’œuvre!

Wood’s work with diffraction gratings had one immediate by-product that gave him wide attention while he was still in Madison — the invention of a new process of color photography which no one had previously dreamed of. It came about in a curious way. Wood had been invited by Professor Snow to a meeting of the Town and Gown Club, a select group of local potentates and faculty members which met once a month and listened patiently to an hour’s dull lecture. Membership was considered the highest honor in Madison, and it was deemed a distinction even to be invited as a guest. Apparently Wood was insensible to this honor, and smoked throughout the lecture and thought his own thoughts.

On the way home, as he and Snow were tramping through the deep snow, Wood suddenly said: “I’ve worked out all the details of a radically new process of color photography. If you take a diffraction grating, put it in front of a lens before a light, and put your eye in the green of the spectrum, the whole surface appears green. If another grating with a coarser spacing is put beside it, this grating will shine with a red light”. And all the way home through the snowstorm Wood proceeded to describe in detail the whole process, which he had thought out completely during the Town and Gown lecture.

In the spring of 1899 Wood conceived the idea of studying light waves through their analogy with sound waves — and of projecting drawings of the latter on a cinematographic screen. There were, properly speaking, no motion pictures in those days, but the primitive machine had already been invented, and Wood was the first to foresee its possibilities in connection with animated drawings[5].