20 LETTERS ON NATURAL MAGIC, 



retina is affected at the place where the muscles 

 are inserted, and there may be seen opposite each 

 eye, and towards the nose, two semicircles of 

 light, and other two extremely faint towards the 

 temples. At particular times, when the retina is 

 more phosphorescent than at others, these semi- 

 circles are expanded into complete circles of light. 

 In a state of indisposition, the phosphorescence 

 of the retina appears in new and more alarming 

 forms. When the stomach is under a temporary 

 derangement accompanied with headache, the 

 pressure of the blood-vessels upon the retina 

 shows itself, in total darkness, by a faint blue 

 light floating before the eye, varying in its shape, 

 and passing away at one side. This blue light 

 increases in intensity, becomes green and then 

 yellow, and sometimes rises to red, all these colours 

 being frequently seen at once, or the mass of light 

 shades off into darkness. When we consider the 

 variety of distinct forms which in a state of per- 

 fect health the imagination can conjure up when 

 looking into a burning fire, or upon an irregularly 

 shaded surface,* it is easy to conceive how the 



* A very curious example of the influence of the imagina- 

 tion in creating distinct forms out of an irregularly shaded 

 surface, is mentioned in the life of Peter Heaman, a Swede, 

 who was executed for piracy and murder at Leith in 1822. 

 We give it in his own words : 



" One remarkable thing was, one day as we mended a 

 sail, it being a very thin one, after laying it upon deck in 

 folds, I took the tar brush and tarred it over in the places 

 which I thought needed to be strengthened. But when we 

 hoisted it up, I was astonished to see that the tar I had put 

 upon it represented a gallows and a man under it without a 

 head. The head was lying beside him. He was complete, 

 body, thighs, legs, arms, and in every shape like a man. 

 Now, I oftentimes made remarks upon it, and repeated 



