For this very movie it would be presumeable quite trivial to correct the varying frame rate caused by the hand cranked camera with the help of the quite stable

For this very movie it would be presumeable quite trivial to correct the varying frame rate caused by the hand cranked camera with the help of the quite stable deceleration of the train and it's position to determine a corrected timestamp for each frame and then interpolate from there. It's fair to assumem that at the time, a skilled presenter knowing the material was able to compensate for that too to some extent, since the Cinematograph was camera and projector in one, both manually operated. Stable frame rates were simply not a thing in earliest film. https://en.wikipedia.org/wiki/Cinematograph https://en.wikipedia.org/wiki/Cinematograph