[Illustration: I _Designed by J. H. Brown, and Published Decʳ. 19ᵗʰ. 1863, by Griffith & Farran, Sᵗ. Paul’s Church Yard, London._] SPECTROPIA; OR, SURPRISING SPECTRAL ILLUSIONS. SHOWING GHOSTS EVERYWHERE, AND OF ANY COLOUR. BY J. H. BROWN. _FOURTH EDITION._ First Series. WITH SIXTEEN ILLUSTRATIONS. LONDON: GRIFFITH AND FARRAN, SUCCESSORS TO NEWBERY AND HARRIS, CORNER OF ST. PAUL’S CHURCHYARD. H. & C. TREACHER, BRIGHTON. MDCCCLXV. [_Entered at Stationers’ Hall._] INTRODUCTION. The following Illusions are founded on two well-known facts; namely, the persistency of impressions, and the production of complementary colours, on the retina. The explanations are divided into two Parts. The FIRST consists of directions for seeing the spectres. The SECOND, a brief and popular, as well as a scientific, description of the manner in which the spectres are produced, and is intended for the use of those who may wish to know more of this subject than is contained in the first Part. 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. J. H. BROWN. OLD STEYNE, BRIGHTON. DIRECTIONS. To see the spectres, it is only necessary to look _steadily_ at the dot, or asterisk, which is to be found on each of the plates, for about a _quarter_ of a minute, or while counting about twenty, the plate being well illuminated by either artificial or day light. Then turning the eyes to the ceiling, the wall, the sky, or better still to a white sheet hung on the wall of a darkened room (not totally dark), and looking rather steadily at any one point, the spectre 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 to and fro before them, will frequently hasten the appearance of the spectre, especially if the plate has been strongly illuminated. Those who use gaslight will find it convenient, after having looked at the plate as above described, to extemporise a darkened room by having the gaslight turned low; or one end of the room may be darkened by placing a screen before the gas, lamp, or candle light.