A distinguished English physician, John Ayrton Paris (1785-1856), was the inventor of the thaumatrope, a popular children's toy of Victorian Britain. It was conceived, not as a form of entertainment, but to demonstrate an optical phenomenon.
The thaumatrope is a simple device: a disc with a picture on each side and two pieces of attached string. The disc is rotated by hand to coil the attached strings, and then the strings are quickly pulled apart. This causes the disc to rotate rapidly, enabling the pictures on either side to be visible in quick succession; the two images are interpreted by the human eye as a single image. This phenomenon is known as persistence of vision and was demonstrated to a meeting of the Royal College of Physicians in 1824. One of Paris's exhibits featured a bird on one side of the disk and an empty birdcage on the other; when it was rotated quickly, the disk presented to the eye the image of a bird inside a cage.
The thaumatrope was certainly an important antecedent of both cinematography and animation. When we watch a film at the cinema we are experiencing the same persistence of vision that Paris demonstrated with the thaumatrope, since what we are seeing is a series of still images passing before our eyes at such a speed that they appear to be moving. Cartoon animation works on the same principle.
Paris himself showed little interest in the nonscientific applications of his invention, and continued to devote his efforts to medical research'. He would later write some of the most important medical books of his generation.
