He not only photographed the successive stages, but printed them on a long strip which was laid around a horizontal wheel.

This wheel is in a dark box and the eye can see the pictures on the paper strip only at the moment when the light of a Geissler's tube flashes up.

The wheel itself has such electric contacts that the intervals between two flashes correspond to the time which is necessary to move the wheel from one picture to the next.

However quickly the wheel may be revolved the lights follow one another with the same rapidity with which the pictures replace one another.

During the movement when one picture moves away and another approaches the center of vision all is dark.