68 The Life Story of the Fish 



We find ourselves confronted with two difficulties. The 

 first is of an objective nature. It has to do, not with what 

 the fish is capable of seeing, but with what there is to be 

 seen. To put it in one sentence, what is visible to the 

 fish? 



As long as we remain under water there is no difficulty. 

 Under water, visibility is not as good as in the air, but similar 



Diagram A 



Diagram Ai 



in its workings. Things cannot be seen at so great a distance, 

 and darkness increases with depth, but there is no distortion. 

 Light does not travel as fast or as far as in the air, but, as 

 long as it remains under water, it does travel in a straight 

 line. 



It is when it comes out of the water into the air, or when 

 it goes from air into water, that light gets into trouble, for 

 then it meets with the phenomenon known as refraction, and 

 gets bent. This is the old trick of the soap not being where 

 it appeared to be through the water in the bathtub, which 

 used to fascinate us in our childhood days before both bath- 

 tubs and the mysteries of nature became commonplaces. 



It is to be noted that it is the light passing from the soap 

 to our eye, and not from our eye to the soap, by which we see 



