Later when scientific investigators were busy inquiring into the phenomena of visual distortions exhibited by the spokes and teeth of turning wheels when seen in contrast with certain intervening objects, a curious apparatus was contrived by Faraday the English scientist (1791-1867). This apparatus was so constructed that two disks were made to travel, by cogged gearing, in opposite directions, but at the same speed. Around the circumferences of the disks were cut narrow slots at equal distances apart and so making the solid portions between them like teeth, or spokes of a wheel.
APPARATUS ON THE ORDER OF FARADAY’S WHEEL.
With the disks moving as marked, the disk B will appear to be motionless when viewed through the passing slots of disk A.
When this machine was set in motion and the eye directed through the moving and blurred teeth of the front disk toward the far disk, this far disk appeared to be stationary. Its outline—the teeth, slots, and circumference—were distinctly seen and not blurred.
Then it was found that the same effect could be obtained with the use of one slotted disk by simply holding it in front of a mirror and viewing the reflected image through the moving slots of the disk. The reflection answered for the second disk of the instrument of the first experiment.
AN ANTECEDENT OF THE PHENAKISTOSCOPE.
When the disk is twirled the reflections of its spokes appear stationary when viewed through the moving slots.
From this type of optical toy it was but a step to the contriving of various types of instruments constructed on the pattern of a slotted disk, or some sort of a turning mechanism with a series of apertures, to use in giving the illusion of movement in connection with drawings or photographs. The best-known was the phenakistoscope, the invention of which has been credited to the Belgian physicist, Plateau (1801-1883). This toy was a large cardboard disk with pictures on one side that were to be viewed by their reflections through slots in the disk while it was held before a mirror. The pictures drawn in sequence represented some action, as a horse running, an acrobat, a juggler, or some amusing subject that could be drawn easily in a cycle of actions and that would lend itself to repetition.