The Senses cmd the Nervous System 



71 





Diagram C 



at him along the line M'XF. Neither one is in reality where 

 he appears to be to the other, and this makes it seem a real 

 achievement on the part of both fisherman and fish when 

 they succeed in connecting with one another. However, it is 

 to be noted that when the fisherman's fly is on the water it 

 is at one of those surface points X, which really are where 

 they appear to be to both man and fish j and if the bait is an 

 underwater lure, the fish sees it where it really is and it 

 does not matter whether the fisherman does or not. 



We now come to the heart of the whole matter, which is 

 that, to the fish peering upward, the surface of the water is 

 opaque except within a circle directly over its head. This 

 circle alone is transparent. In other words, the surface of 

 the water is to the fish an impenetrable ceiling with a cir- 

 cular transparent window in it. This is because of the 

 phenomenon known as total refraction. For it is a charac- 

 teristic of the refractive processes that the sharper the angle 

 at which light approaches the surface, the greater the angle 

 through which it is bent. Light going from water to air along 



