Optical Gliosis. 37 



Mr. J. H. Brown, acting upon another set of optical 

 principles, offers us " Ghost's Everywhere, and of any Colour."* 

 We need not stay to comment on the explanatory part of this 

 volume, but proceed to the pictures, which are drawnand coloured 

 so as to excite similar images on the retina in accidental colours. 

 Our readers have no doubt often tried the experiment of 

 sticking coloured wafers on a sheet of white paper, holding them 

 a strong light, and staring at them fixedly for a few seconds. 

 If this is done, and the eye then taken off the wafer, and 

 turned on to the white paper, the wafers' image will appear 

 sharp and distinct, but in another colour. A red wafer will 

 look green (or blue and yellow combined), a blue one orange 

 (or red and yellow combined), a yellow one purple (or blue 

 and red combined), and wafers of composite hues will be 

 affected in an analogous way. These " spectral," " acci- 

 dental," or " complementary" colours — for they are known 

 under these three appellations — appear bright to the eye in 

 proportion to its sensitiveness to the original colour, to the 

 strength of the illumination, and to the steadiness with which 

 the original object has been contemplated. Mr. Brown finds 

 the time occupied in counting twenty, or about a quarter of 

 a minute, sufficient to impress his figures upon most eyes, if 

 the plates are well lit up. His directions are to look steadily, 

 for the time specified, at a dot or asterisk to be found in each 

 plate, " the plate being well illuminated by either artificial or 

 day hght. Then turning the eyes to the ceiling, the wall, 

 or 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 one point, the spectre will soon begin to 

 make its appearance, increasing in intensity, and then gradually 

 vanishing, to reappear and again vanish." 



The Brownian spectres depend upon the tendency of 

 strong impressions to remain a little while upon the eye, and 

 to reappear in accidental colours. The plates are certainty 

 very effective, and well designed for the purpose ; but we 

 should recommend an avoidance of needless horrors in future 

 series. The grotesque and the beautiful will both work just 

 as vividly as the ghastly, and several objects in the present 

 series could not be judiciously introduced to the notice of 

 boys and girls whose disposition was nervous, or whose 

 superstitious feelings had been excited by injudicious nursery 

 tales. 



Mr. Brown's direction to enlarge the spectral appear- 

 ance by looking for it on a white sheet, or wall, some distance 



* Spectropia, or Surprising Spectral Illusions, showing Ghosts Everywhere 

 and of any Colour, by J. H. Brown. First series, with sixteen illustrations 

 Griffiths and Co. 



