Zoetrope - Invented in the 1860s, the zoetrope was a small instrument which gave drawings the illusion of movement. Consecutive drawings were placed on a strip of paper, which was then placed inside a drum on which slots had been cut. When one spun the drum and looked through the slots, one got the impression that the characters in the drawings were moving. The physical concept is persistence of vision, whereby the brain is not quick enough to see the drawings speeding by, so they blur together and seem to move. It was the same concept of persistence of vision that three decades later led to the invention of motion picture film.