The Thaumatrope;
being
Rounds of Amusement,
or
How to please and surprise
By Turns.
Mr. Seymour now proceeded to explain more fully the optical theory of the instrument, which neither Louisa nor Tom could, as yet, thoroughly understand.
He told them that an object was seen by the eye, in consequence of its image being delineated on the retina, or optic nerve, which is situated on the back part of the eye; and that it had been ascertained, by experiment, that the impression which the mind thus receives, lasts for about the eighth part of a second after the image is removed. “It is, therefore, sufficiently evident,” said Mr. Seymour, “that if any point, as a lighted stick, be made to revolve, so as to complete the circle in that period, we shall not see a fiery point, but a fiery circle; because the impression made by it in every point of its circuit will remain until it comes round again to the spot from which it set out;--but we will, at once, exemplify this fact by an experiment.”
Tom was accordingly directed to procure a piece of stick and a candle; and as soon as they were brought into the room, Mr. Seymour ignited the end of the stick and whirled it round, when a bright circle, without any intervals of darkness, was seen by the whole party.
“Never until this instant,” exclaimed the vicar, with an expression of high satisfaction, “did I fully appreciate the beauty of that passage in Milton, wherein the poet evidently describes the rapidity of Satan’s flight, as well as the refulgence of his appearance--