Peter Mark Roget (1779–1869), English doctor best known for his Thesaurus of English Words and Phrases, combined his medical work with interest in the sciences. On December 9, 1824, he read, at the Royal Society, a paper called, “Explanation of an optical deception in the appearance of the spokes of a wheel seen through vertical apertures.” Roget pointed out that the phenomenon had been noted but not explained by an anonymous contributor who signed himself “J. M.” in the Quarterly Journal of December 1, 1820. “J. M.” commented on the curvature of spokes when a wheel is in motion and is viewed through a series of vertical bars. Everyone has noted the strange rotations of motor car wheels when viewed under certain conditions, as in the modern motion picture. “J. M.” pointed out that at times the wheel appeared to rotate backwards; at other times, forward and still again seem to stand still. A nod of praise should be bestowed towards “J. M.” (these are not the initials of any of the better known English scientists of the period). Ten years later the great Faraday confessed he did not know the identity of this man who had stimulated those investigations which we now know led directly to the first actual motion pictures formed from hand-drawn designs.
Roget, in 1824, noted that a certain velocity and a certain amount of light were necessary before the “wheel phenomenon” was visible—both speed of motion and bright light source are necessary for the motion picture illusion. Roget said, “It is evident from the facts above stated that the deception in the appearance of the spokes must arise from the circumstances of separate parts only of each spoke being seen at the same moment; the remaining parts being concealed from view by the bars” (equivalent to the shutters in the motion picture machine). Roget continued, “so that it is evident that the several portions of one and the same line, seen through the intervals of the bars, form on the retina the images of so many different radii.” Roget remarked that the illusion was the same as when a bright object is whirled in a circle—“an impression made by a pencil of rays on the retina, if sufficiently vivid, will remain for a certain time after the cause has ceased.”
A few weeks later, on December 24, 1824, Roget lectured on the persistence of vision with regard to moving objects, a phenomenon first recognized by the ancient scientists.
Plateau wrote in 1828 as follows:
I have made an instrument by means of which I could produce these fixed images with ease and I also could make visible the formation of changes in the curvature ... when working at my first experiments relative to sensations, I observed that while turning rapidly a wheel whose teeth were perpendicular to its axis, and placing the eye at some distance from the plane of the axis, one perceived the image of a series of perfectly immobile teeth; that also with two wheels revolving, the one behind the other, with considerable speed and in opposite directions, produced in the eye the sensation of a fixed wheel. I have remarked further that, while the two wheels are not concentric, the fixed image appears to be made up of curved lines.
Today stroboscopic machines, based on the principles of Plateau’s devices, are used to study moving objects. In this way modern scientists learn more about the nature of movement and its stresses on wheels and other objects.
Plateau received the degree of doctor of physical and mathematical sciences from the University of Liége on June 3, 1829, when he was 28. His thesis was on “Certain Properties of the Impressions Produced by Light upon the Organ of Sight.” It is strange that such a learned paper would have so much influence on what was to be the modern motion picture.
The chief points—all of importance in building motion pictures—of the Plateau thesis dated April 24, 1829, were: First, the sensation (result of the picture presented to the eye) must stay for a time to form completely—this hinted definitely at the necessity of intermittent movement for a really successful and practical motion picture machine. Second, the sensations do not disappear immediately but gradually dim—this makes motion pictures possible. If each image disappeared all at once, only individual still pictures would be recognized. The gradually dimming makes possible fusion of one image with the next which results in appearance of motion. The third point covered was the relative effect on the eye of various colors. Plateau concluded that the intensity of the chief colors decreased from white, yellow, red, blue—in that order. He also announced results of perception of various colors at different angles, studies made in the shade and in the light. It was further pointed out that two colors—as two images—changed rapidly result in only one sensation or image.
After receiving his doctor’s degree from the University, Plateau taught at the Royal College of Liége while he continued his research on vision and related matters.
