Transformations

Transformations were invented by Ernest Nister and there are two different types of books. The one type, sometimes referred to as "revolving picture books", consists of two seperate circular cards, each illustrated, cut halway through so they overlap. Both cards are mounted on a center axis between two pages sealed around the edges. The face page has a circular viewing opening with a frame. A ribbon pull loop at the bottom of the page may be pulled around the perimeter of the circular opening to reveal the illustration on the inner card. In the other type of transformations, sometimes called dissolving picture books, pulling a tab causes an illustration to change completely into a different scene. In this mechanism, both picures are printed on slats which slide over each other when the tab is pulled.