The Senses and the Nervous System 79 



the fish, and every move you make is clearly visible in the 

 round motion-picture on the screen above him. He naturally 

 eyes you and your movements with distrust, and when the 

 still, opaque, overhead mirror outside the circle is abruptly 

 cut by your line reaching out toward him it is the last straw 

 which sends him off to hide until normalcy is restored. 



If there are waves, everything is changed. The surface is 

 no longer a single refracting unit with a single round, unified 

 picture of the world above, set in a mirror-ceiling. It be- 

 comes a great number of refracting units, all at different 

 angles, and all changing all the time. Any particular part of 

 the surface is at one moment horizontal, and refracting light 

 as we have described j at the next it is tipped to one side by 

 a wave, and the refraction is exaggerated 5 at the next it is 

 tipped in the opposite direction, and the rays of light be- 

 come normal to it, and suffer no refraction at all. Every 

 object in the picture wobbles around in dizzy fashion. The 

 opaque mirror-surface surrounding the circular window be- 

 ing also in motion, the things in it are bobbing around too. 

 Further, parts of it are frequently being tipped by waves at 

 angles normal to the light from the bank, and the fish gets a 

 momentary glimpse of you as you really are — ^but entirely 

 outside the circular frame In which he sees you when the 

 water is calm. The result is that the whole ring of objects 

 around the fish's circular window, the window itself, and the 

 surrounding mirror-screen, are in an unceasing, wavering, 

 shifting dance beyond the imagination of even the rnost ex- 

 treme alcoholic among humans. The man and the tree on 

 the bank are at M and T one second, at M' and T' the next 

 (Diagram F) ; or they may be at both at the same Instant, if 

 there happen to be simultaneously a horizontal surface at X' 

 and just the right kind of a wave at Y. And the same thing 

 holds true in any stream with enough flow so that the sur- 

 face angles are constantly being changed by the currents of 

 water. 



