Spectropia: surprising spectral illusions showing ghosts everywhere and of any colour, first published by John Henry Brown in 1864.
Brown was distressed by an increased public interest in spiritualism, something which he deemed a "mental epidemic." By offering a scientific explanation on the properties of light, colour, and the structure of the eyes, he states in the section "Popular and Scientific description" that the purpose in writing Spectropia was to bring forth "the extinction of the superstitious belief that apparitions are actual spirits, by showing some of the ways our senses may be deceived."
By staring at an image in Spectropia for roughly a quarter of a minute without blinking and then looking away from the book at a wall, the reader will see the image of the spectres appear before them floating on the wall. This is due to an optical illusion called afterimage, a phenomenon where the image continues to appear in one's vision after the exposure to the original image has ceased.
24.5cm x 19.4cm. 48 Pages. Colour and other illustrations. Paperback.