Many machines that were merely developments of the old zoetrope were brought out both in the United States and Europe, but the greatest obstacle to their success was that they were peep-hole machines of the kind that flourished in penny arcades a few years ago, rather than devices for throwing pictures on a screen so that a large number of persons could see at the same time. In general, these old-fashioned "moving-picture" machines were simply cabinets in which were mounted a series of transparencies made from pictures representing the stages of some simple animation. An electric light illuminated the transparencies and they were rotated so that one picture at a time was seen. In some of the more improved "wheels of life," such as were shown in this country, the transparencies in consecutive order were mounted on a hub like the spokes of a wheel and were rotated so that one was seen at a time, very much like the way Muybridge riffled his horse pictures over his thumb. All this time two American inventors had been at work on the two most perplexing problems in animated photography at that time, and it was through their achievements that the first practical motion-picture machine was given to the world, just as it was through the achievements of the Wright brothers that the first practical aeroplane was given to the world. These two men were Thomas A. Edison and George Eastman. Mr. Edison had been working for several years on a motion-picture machine, but was handicapped by the lack of a practical film. Mr. Eastman, after years of experiment, produced the film that made cinematography possible, in 1889. With a strong transparent film, flexible, and compressible, to take the place of the clumsy glass plate, Edison was ready to go ahead with his work, started years before, and in 1893 the crowds at the World's Fair in Chicago saw the first motion-picture machine. It was called a Kinetoscope. [Illustration: Courtesy of Thomas A. Edison, Inc. THE CORSICAN BROTHERS--A FAMOUS TRICK FILM The parts of the twin brothers in this film were acted by the same man, the illusion being accomplished by the double exposure trick.] [Illustration: Courtesy of the Vitagraph Company of America THE GUILLOTINE Famous scene from the photoplay based on Dickens's great novel, "A Tale of Two Cities."]