[Optical illusion disc with somersaults and horseback riding]

In 1832, Belgian physicist Joseph Plateau and his sons introduced the phenakistoscope ("spindle viewer"). It was also invented independently in the same year by Simon von Stampfer of Vienna, Austria, who called his invention a stroboscope. The phenakistoscope consisted of two discs mounted on the same axis. The first disc had slots around the edge, and the second contained drawings of successive action, drawn around the disc in concentric circles. Unlike Faraday's Wheel, whose pair of discs spun in opposite directions, a phenakistoscope's discs spin together in the same direction. When viewed in a mirror through the first disc's slots, the pictures on the second disc will appear to move. After going to market, the phenakistoscope received other names, including Phantasmascope and Fantoscope (and phenakistiscope in Britain and many other countries). It was quite successful for two years until William George Horner invented the zoetrope, which offered two improvements on the phenakistoscope. First, the zoetrope did not require a viewing mirror. The second and most influential improvement was that more than one person could view the moving pictures at the same time.