ABSTRACT
The thaumatrope is capable of showing that binocular vision can detect to a degree hardly conceivable the most minute difference in the distances of objects, such as the distance between the planes of the two surfaces of a card, which distance is nothing more than, the thickness of the card. The cause of the anomaly resulting from the two different experiments is entirely and positively due to a sensation of binocular vision. The angle of convergence kept on one or the other surface is no impediment to our seeing both in a sufficiently distinct manner. If the two strings are drawn so that one of their knots is as in fig. 4, the surface B will revolve round the plane of the surface A corresponding with the axis of the string, and, during the revolution, every time that it is made visible to the eyes it will appear as if it were nearer than the surface A.
