But, as Uchatius himself said, he was asked to develop the invention as far back as 1845, at the request of Field Marshal Lieutenant von Hauslab. That general very probably thought that if moving figures of the Plateau-Stampfer magic disks could be projected on the wall there would be available a potent instrument for military instruction. In our own day the motion picture has come to be an important aid in military training all over the world. Uchatius wrote as follows: The well known illusion caused by means of the Stampfer disk arises from the fact that the eye receives on the same portion of the retina pictures succeeding one another at short intervals, which present some recurring motion in its various phases, and through this arises an effect which equals that of one picture observed in motion. The method used by Uchatius to throw a connected series of images on a wall “in any desired size” is indicated by the illustrations. Uchatius noted that the Plateau-Stampfer disk had a certain disadvantage not only because but one person could observe the effects at a time but also because the pictures were not sharp and clear. The first model developed by Uchatius was described as follows: The pictures (a), (a) ... are painted on transparent glass and mounted on a disk, (A), at equal intervals, and the lowest of the pictures was illuminated from behind by the lamp (S) and the illuminating lens (B). A second disk, (C), contained the slits (b), (b) ... (the modern shutter) to be brought before each picture. The slits correspond to those in the Stampfer disk. Both disks are mounted on the same axis, (D), and are rotated by the crank (E). The slit, (c), corresponds to the pupil opening of the eye and the achromatic lens, (F), to the crystal lens of the eye. The lens is adjustable to allow the picture to be focussed sharply. The surface, (G) (the screen) finally corresponds to the position of the retina of the eye. When the disks are turned, the successive pictures appear on the wall, (G), just as they are seen in the Stampfer disk, in intervals so short that they are not noticed by the eye. This machine was satisfactory but limited. Uchatius was a sharp critic of his own work: “The apparatus produced very good motion pictures whose size, however, could be enlarged to a maximum of only six inches in diameter, because should the wall, (G), be moved far from the projector the pictures became too dark on account of the light cut off by the slits. And an enlargement of the slits brought about greater indistinctness. However, a projected motion picture had been attained which could be viewed simultaneously by a considerable number of people. But it still remained desirable to project this picture in a suitable size on a wall and thus show it in an auditorium or theatre.”