A thaumatrope is an optical toy that was popular in the 19th century. A disk with a picture on each side is attached to two pieces of string. When the strings are twirled quickly between the fingers the two pictures appear to blend into one due to the persistence of vision. Examples of common thaumatrope pictures include a bare tree on one side of the disk, and its leaves on the other, or a bird on one side and a cage on the other. Many classic thaumatropes also included riddles or short poems, with one line on each side. Thaumatropes can provide an illusion of motion with the two sides of the disc each depicting a different phase of the motion, but no examples are known to have been produced until long after the introduction of the first widespread animation device: the phénakistiscope. Thaumatropes are often seen as important antecedents of motion pictures and in particular of animation. The name translates roughly as "wonder turner", from "wonder" and τρόπος "turn". Invention A 2012 paper argues that a prehistoric bone disk found in the Laugerie-Basse rockshelter is a thaumatrope, designed to be spun using leather thongs threaded through the central perforation. The invention of the thaumatrope is usually credited to British physician John Ayrton Paris. He described the device in his 1827 educational book for children Philosophy in Sport Made Science in Earnest, with an illustration by George Cruikshank. British mathematician Charles Babbage recalled in 1864 that the thaumatrope was invented by the geologist William Henry Fitton. Babbage had told Fitton how the astronomer John Herschel had challenged him to show both sides of a shilling at once. Babbage held the coin in front of a mirror, but Herschel showed how both sides were visible when the coin was spun on the table. A few days later Fitton brought Babbage a new illustration of the principle, consisting of a round disc of card suspended between two pieces of sewing silk. This disc had a parrot on one side and a cage at the other side. Babbage and Fitton made several different designs and amused some friends with them for a short while. They forgot about it until some months later they heard about the "wonderful invention of Dr. Paris". French artist Antoine Claudet stated in 1867 that he had heard that Paris had once been present when Herschel demonstrated his rotating