 A sheet of celluloid, measuring 2 1/2 inches by 13 5/8 inches.  Developer W.K.L. Dickson described the process in 1895: "Then  followed some experiments with drums, over which sheets of  sensitized celluloid film were drawn, the edges being pressed into a  narrow slot in the surface, similar in construction to the old  tinfoil phonograph. A starting and stopping device was also applied  . . . The pictures were then taken spirally to the number of two  hundred or so, but were limited in size owing to the rotundity of  surface, which only brought the centre of the picture into focus.  The sheet of celluloid was then developed, etc., and placed upon a  transparent drum, bristling at its outer edge with brass pins. When  the brass was rapidly turned these came into contact with the  primary current of an induction coil, and each image was lighted up  [with a Geissler tube placed inside the drum, the primary wire of  which, operated by the pins, produced a rupture of the primary  current, which in its turn, through the medium of the secondary  current, lighted the Geissler tube at the precise moment when a  picture crossed its range of view]."