But Marey himself improved the method. 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. Marey remained indefatigable in improving the means for quick successive snapshots with the same camera. Human beings were photographed by him in white clothes on a black background. When ten pictures were taken in a second the subtlest motions in their jumping or running could be disentangled. The leading aim was still decidedly a scientific understanding of the motions, and the combination of the pictures into a unified impression of movement was not the purpose. Least of all was mere amusement intended. About that time Anschuetz in Germany followed the Muybridge suggestions with much success and gave to this art of photographing the movement of animals and men a new turn. 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. Hence the eye does not see the changes but gets an impression as if the picture remained at the same spot, only moving. The bird flaps its wings and the horse trots. It was really a perfect kinetoscopic instrument. Yet its limitations were evident. No movements could be presented but simple rhythmical ones, inasmuch as after one revolution of the wheel the old pictures returned. The marching men appeared very lifelike; yet they could not do anything but march on and on, the circumference of the wheel not allowing more room than was needed for about forty stages of the moving legs from the beginning to the end of the step.