All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

326 All About Inventions picture machine ; but by whatever name it may be called, it succeeded in its essential purpose—it con- veyed life-like photographic representations. What is more, it represented the first proved illustration of synchronising movement with sound. Those were the days before the flexible celluloid film, and when the wet process still prevailed in the art of photography. Consequently Heyl’s achieve- ment was somewhat remarkable, and was a wonderful example of unremitting patience, skill, and persever- ance. Each picture was reproduced separately upon a glass plate from which a glass positive, somewhat reminiscent of the lantern slide, was prepared. But the pictures were taken at such brief intervals that when thrown upon the screen at the accurate speed, rhythmic animation was secured. The audience was moved by one series which portrayed two accomplished waltzers, and the perfection of the production was brought home by the fact that their actions syn- chronised absolutely with the tempo of the waltz music played by the orchestra. Heyl’s apparatus was somewhat complicated. It comprised the lantern set within a revolving frame wheel placed in a horizontal position. The rim of this drum was so divided into spaces that each would receive one of the glass plates or slides. The wheel was charged to its full capacity with these slides disposed in correct sequence, and then revolved at the speed necessary to secure the illusion of move- ment. When a slide came before the lens of the projector it was held stationary for the fraction of a second. Then it moved forward as the light was obscured by a shutter which, moving to and fro,