In 1864, James G. Gregory published Spectropia: Surprising spectral illusions showing ghosts everywhere and of any colour (possibly the world’s longest book title?) which aimed to debunk spiritualism and the existence of ghosts by putting forward a scientific explanation for “spectral illusions”:
“It is a curious fact that, in this age of scientific research, the absurd follies of spiritualism should find an increase of supporters; but mental epidemics seem at certain seasons to affect our minds, and of the oldest of those moral afflictions–witchcraft–is once more prevalent in this nineteenth century, under the contemptible forms of spirit-wrapping and table-turning…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…”
Gregory explains how the optical nerve can be tricked to create a ghostly vision:
“A lady assures us that she saw the ghost of her husband as she was going downstairs with a lighted candle in her hand. The spot k, Fig. 4, when seen against a wall a few feet distant appears about the size of a human head, and wants very little to furnish it with features. Figured paper on the wall, and a host of other things, may supply them, or even the retinal artery, which often lends body and limbs.”
Spectropia features 16 creepy illustrations, which are designed to trick your eyes and bring these ghostly images to life. We are instructed to look steadily at the dot or asterisk in each image (which should be well-lit) for about 20 seconds. Then, we must turn our eyes away–to the ceiling, the wall, etc.–and then back to stare at one point on the image. The spectre is supposed to increase in its intensity, then start to vanish. Gregory promises: “All the spectres will appear life-sized if the observer is about sixteen feet from the surface against which they are seen. If much further, they will appear colossal.”
I didn’t see any ghosts–but perhaps you need to do this trick after drinking large amounts of spirits (of the liquid variety).
Spectropia is a wonderful read, and the entire volume is available on-line for free here by archive.org.
Happy haunting everyone!