About 1867 Marey started to study the attitudes of animals in movement through the aid of a Plateau magic disk and drawings made with the aid of Mathias Duval, professor of anatomy at the School of Beaux Arts. Some of the designs used by Marey in the Wheel of Life and a magic lantern projector were drawn by Col. Duhousset, a great horseman and artist, from very early and imperfect instantaneous photographs. Prior to Marey there had been a number of attempts to record motion by photography. The most successful was by the French astronomer, Pierre Jules César Janssen (1824–1907) who used a photogun, _Revolver Photographique_, to record the transit of Venus in Japan in 1874. Janssen may have been influenced by Marey’s earliest work. Dr. R. L. Maddox in 1871 had developed in England dry plate photography, based on Scott Archer’s wet plate process. This helped to make instantaneous photography, or Chronophotography, as it was called, possible. Janssen perfected the first workable motion picture camera. But it was a large, stationary piece of apparatus, limited in scope and sensitiveness. The device was described by a French astronomer, C. Flammarion, in the magazine _La Nature_ of May 8, 1875, and by Janssen himself in the _Bulletin of the French Photographic Societies_ of April 7, 1876. Janssen’s device took forty-eight pictures on a simple revolving plate but he said the number could easily be doubled or tripled. A time clock mechanism controlled the revolutions of the photographic plate but it was so arranged that it could also be rotated by hand. An electrical hook-up also was possible. The influence of Plateau’s magic disk is clear and so acknowledged by Janssen. The device simply reversed the old Plateau disk which showed motion pictures through two revolving disks, one with the pictures and the other with the shutter slits. In the Janssen astronomical gun the one disk was coated with photographic chemicals and the other had the usual slits; the necessary intermittent movement was provided by the gear driven mechanism which rotated the disks. Janssen pointed out that the apparatus could be used for physiological purposes--to study walking, running, flight and the movement of animals; but he never had time to develop the device for physiological uses, which was not in his immediate field. He was, however, interested in Marey’s later refinements and applications.