BY WAY OF INTRODUCTION 23 



cealed from the fish. The structure of the eye 

 of a fish suggests that it ought to be able to 

 appreciate colour, and therefore it seems only 

 reasonable to think that fish appreciate colour 

 values. 



" Jim Jam " described in The Field a series 

 of feeding experiments by which he showed that 

 a roach could appreciate red, white and blue as 

 colours. And dry fly-fishing certainly leads one 

 to think that a fish is not colour blind. 



The question of the " window " and the area 

 of total reflection depends upon definite optical 

 laws which control the course of rays of light 

 from air into water. With the fish's eye very 

 similar in structure to the human eye, there is 

 no reason to think that the fish sees the world 

 above the water in a different manner from 

 ourselves. 



It has been experimentally proved that the 

 trout see a very large arc of the circular 

 -" window " as he lies in the water; in fact, all 

 of it except for sixty degrees immediately behind 

 him. This is quite easy to believe when one 

 thinks of the behaviour of the surface-feeding fish. 

 Keep immediately below him, and as long as 

 you throw your fly straight above the fish he will 



