194 Idle Days in Patagonia. 



some time, as they will when an owl is confronted 

 with strong sunlight ; and this gave me the im- 

 pression that the fiery, flashing appearance was 

 accompanied with, or followed by, a burning or 

 smarting sensation. I will here quote a very 

 suggestive passage from a letter on this subject 

 written to me by a gentleman of great attainments 

 in science : " Eyes certainly do shine in the dark 

 some eyes, e.g. those of cats and owls; and the 

 scintillation you speak of is probably another form 

 of the phenomenon. It probably depends upon 

 some extra-sensibility of the retina analogous to 

 what exists in the molecular constitution of sulphide 

 of calcium and other phosphorescent substances. 

 The difficulty is in the scintillation. We know that 

 light of this character has its source in the heat 

 vibrations of molecules at the temperature of in- 

 candescence, and the electric light is no exception 

 to the rule. A possible explanation is that supra- 

 sensitive retinas in times of excitement become 

 increasedly phosphorescent, and the same excite- 

 ment causes a change in the curvature of the lens, 

 so that the light is focussed, and pro tanto 

 brightened into sparks. Seeing how little we know 

 of natural forces, it may be that what we call light 

 in such a case is eye speaking to eye an emanation 

 from the window of one brain into the window of 

 another." 



Probably all those cases one hears and reads 

 about some historical of human eyes flashing fire 

 and blazing with wrath, are mere poetic exaggera- 



