properly date all extant films or even identify them if original titles are missing. Possible stop motion in lost films is even harder to trace. The principles of animation and other special effects were mostly kept a secret, not only to prevent use of such techniques by competitors, but also to keep audiences interested in the mystery of the magic tricks. Stop motion is closely related to the stop trick, in which the camera is temporarily stopped during the recording of a scene to create a change before filming is continued (or for which the cause of the change is edited out of the film). In the resulting film the change will be sudden and a logical cause of the change will be mysteriously absent or replaced with a fake cause that is suggested in the scene. The oldest known example is used for the beheading in Edison Manufacturing Company's 1895 film The Execution of Mary Stuart. The technique of stop motion can be interpreted as repeatedly applying the stop trick. In 1917 clay animation pioneer Helena Smith-Dayton referred to the principle behind her work as "stop action", a synonym of "stop motion". French trick film pioneer Georges Méliès claimed to have invented the stop-trick and popularized it by using it in many of his short films. He reportedly used stop-motion animation in 1899 to produce moving letterforms. Segundo de Chomón Spanish filmmaker Segundo de Chomón (1871–1929) made many trick films in France for Pathé. He has often been compared to Georges Méliès as he also made many fantasy films with stop tricks and other illusions (helped by his wife, Julienne Mathieu). By 1906 Chomón was using stop motion animation. Le théâtre de Bob (April 1906) features over three minutes of stop motion animation with dolls and objects to represent a fictional automated theatre owned by Bob, played by a live-action child actor. It is the oldest extant film with proper stop motion and a definite release date. Segundo de Chomón's Sculpteur moderne was released on 31 January 1908 and features heaps of clay molding itself into detailed sculptures that are capable of minor movements. The final sculpture depicts an old woman and walks around before it's picked up, squashed and molded back into a sitting old lady. Edwin S. Porter and Wallace McCutcheon Sr. American film pioneer Edwin S. Porter filmed a single-shot "lightning sculpting" film with a baker