INTRODUCTION 21 



away. We are, however, for practical 

 purposes concerned rather with how fishes 

 see an object dropped on the surface of 

 the water, between their eye, that is to 

 say, and the source of all natural light. 

 This may be a very different matter, and 

 some measure of concealment is presum- 

 ably afforded by either of the extreme 

 conditions of an overcast sky or a dazzling 

 sun. The vision of the fish may, that is, 

 be equally handicapped by too little or too 

 much light. For this reason, there is an 

 old-fashioned prejudice in favour of a dark 

 fly for bright days and a bright one for 

 dull weather, but the practical application 

 of this rule is subject to many exceptions. 

 The portion of his tackle which most 

 betrays the wiles of the fisherman is his 

 gut, the apparently indestructible glint of 

 which must always be fatal to perfect 

 concealment. Beside the conspicuous 

 apparition of the gut, the mere colour 

 of the fly, as seen against a well-lighted 

 background, may, though its size be all- 

 important, amount to a negligible quantity. 



