ABSTRACT
THE ingenious and amusing invention of M. Plateau, by superadding the resources of art to those of science, has rendered an instructive experiment exceedingly popular. But neither the Professor nor any of his imitators have added anything to the mathematical principles, which remain hitherto in exactly the position in which Mr. Faraday left them nearly three years ago, in the Journal of the Royal Institution. The repose of one portion of the spectrum, the residual motion apparent in the advance or retrogression of others, and the blending of variation of action with identity of subject, have been traced to their causes, both by Mr. Faraday and Dr. Roget, most satisfactorily; nor does it appear that any phænomenon observable in the relative motions of a wheel and a system of detached bars, or of a pair of perforated disks, has escaped the notice of one or other of those gentlemen. One set of phænomena, derived from a still more simple apparatus, has, however, been left unnoticed, as far as I can discover, by all; and my design in submitting the present paper to the readers of the Philosophical Magazine and Journal of Science is to familiarize both the principle and the exhibition of an experiment involving all the interesting illusions of the phantasmascope, but capable of being performed without a 272mirror or any second instrument, and of being displayed to unlimited numbers at once.
