SECRETS OF THE SALMON 



not all have equal intensity; when the beam 

 reaches the surface of the water it is more and more 

 reflected as the beam becomes more nearly parallel 

 to the surface of the water. I have indicated 

 some of the percentages of light which enter the 

 surface at a number of angles. These figures are 

 taken from one of Tyndall's lectures. They are 

 interesting to anglers as showing that objects near 

 the water are not as well illuminated to the fish as 

 those higher up. The small boy learns this early 

 and crawls to the edge of the trout-stream. You 

 will see from the diagram that light from above 

 on an arc of ninety degrees reaches the fish from 

 an arc of forty-one and one-half degrees; this means 

 that objects seen outside the water are flattened 

 in the fish's view. They are, of course, more 

 flattened the closer they are to the water. The 

 portraits of the author at the end of the tank, 

 taken from below, compared with some of the 

 other pictures of the same subject in the book, 

 show the flattening effect. 



This phenomenon of the window from which 

 the fish can see out is a very important one to the 

 fly fisherman, because the window is not always the 

 same size, but increases with the depth of the 

 water above the fish. In very shallow water he 



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