I will second Will. "Standard" camera crank rate for silent films was 18 frames per second. But both cameramen and projectionists often played with film speed (projectors had a rheostat to change the running rate of films) for special effects. The earlier the film, the slower crank rate for the camera, because the earliest projectors were also hand-cranked. 24 frames per second, which we still use today (mostly--I don't know about digital films), was strictly controlled because the optical sound track was printed along the edge of the film, and speeding up or slowing down the film caused all sorts of problems with the sound.
The study of early films is absolutely fascinating.
Mike
Courtesy DPL: