Spectropia: Or, Surprising Spectral Illusions, Showing Ghosts Everywhere, And Of Any Colour (1865) by J.H. Brown; is a book about Victorian ghost conjuring which allows the reader to summon, as the sub-title proclaims: “ghosts everywhere” and any color, apparently. The book has wonderfully odd color plates, with directions on how to use them, and detailed scientific descriptions about how the illusion works. Included in the forward is an explanation on how to use the book:
“One thing we hope in some measure to further in the following pages, is the extinction of the superstitious belief that apparitions are actual spirits, by showing some of the many ways in which our senses may be deceived, and that, in fact, no so-called ghost has ever appeared, without its being referable either to mental or physiological deception, or, in those instances where several persons have seen a spectre at the same time, to natural objects, as in the case mentioned by Dr. Abercrombie, in his work on ‘The Intellectual Powers’: ‘A whole ship’’ company were thrown into the utmost consternation, by the apparition of a cook who had died a few days before. He was distinctly seen walking ahead of the ship, with a peculiar gait, by which he was distinguished when alive, from having one of his legs shorter than the other. On steering the ship toward the object, it was found to be a piece of floating wreck.'”
Brown writes about an optical phenomenon known as “afterimage”, where the eye’s rods and cones adapt to over stimulation and lose sensitivity, and so retain an image when no longer focusing on it.
To see the ghosts, you look steadily at the dot, or asterisk, which is to be found on each of the plates, while counting to twenty, the plate should be well lit by either a lamp or daylight. Then turning the eyes to the ceiling, the wall, or better yet, to a white sheet hung on the wall of a dark room (not totally dark), and looking steadily at any one point, the specter will soon begin to make its appearance, increasing in intensity, and then gradually vanishing, to reappear and again vanish; it will continue to do so several times in succession, each reappearance being fainter than the one preceding. Winking the eyes, or passing a finger rapidly before them, will frequently hasten the appearance of the specter, especially if the plate has been strongly lit.
Regarding the aesthetic quality of the images in the book, Brown comments:
“As an apology for the apparent disregard of taste and fine art in the plates, such figures are selected as best serve the purpose for which they are intended.”
Which is peculiar, because I find the plates to be especially charming.
Source: Cushing/Whitney Medical Library via Public Domain Review