He made use of an idea which the astronomer Jannsen had applied to the photographing of astronomical processes.

Jannsen photographed, for instance, the transit of the planet Venus across the sun in December, 1874, on a circular sensitized plate which revolved in the camera.

The plate moved forward a few degrees every minute.

There was room in this way to have eighteen pictures of different phases of the transit on the marginal part of the one plate.
Marey constructed the apparatus for the revolving disk so that the intervals instead of a full minute became only one-twelfth of a second.
On the one revolving disk twenty-five views of the bird in motion could be taken.

This brings us to the time of the early eighties.