ABSTRACT
The cause of the to-and-fro movements of the wheel will be readily understood from the following considerations. If one photographs a wheel which has eight spokes at eight equal intervals in a single revolution, the pictures will be exactly alike, because the spokes are all identical as to size and shape; and such a set of pictures in the stereotrope would exhibit the wheel as absolutely stationary. If, however, as in the case of the eight pictures in question, there be six spokes in the wheel, the effect becomes more complex, some pictures of the series being alike, and others different; whereas they should all differ in a certain definite degree. This difficulty in representing wheels in movement may be overcome in the following way. Supposing that one is about to take eight consecutive pictures, the wheel are moved on between each, not one-eighth of its entire circumference, but one-eighth of the distance between any two of its spokes.
