Sentence:  Then followed some experiments with drums, over which sheets of sensitized <WSD>celluloid</WSD> film were drawn, the edges being pressed into a narrow slot in the surface, similar in construction to the old tin-foil phonograph. 
Meaning of the word marked with <WSD> tags:  Any of a variety of thermoplastics created from nitrocellulose and camphor, once used as photographic film.