THE ANGLER AND HIS LURES 139 



below the water. If an observer under the 

 water were to look forwards and slightly up- 

 wards, he should see, on the surface, the arc of 

 his " window " and an area of total reflection 

 beyond. 



When a fly is thrown over him from behind, 

 he sees : a break in the area of total reflection 

 and a flicker of light as the fly strikes the water. 

 When the fly has settled, only the body, hackle, 

 and hook are visible, with a reflection of the same 

 from the surface. The gut from this point to 

 the edge of the " window " is difficult to detect. 

 The wings are visible above the arc of the 

 " window," in the same way as the sail of the 

 boat is seen in the lower illustration on the plate 

 opposite page 3. Across the " window," itself 

 the gut, whatever colour, shows up as a clearly 

 defined dark line. 



As the fly floats down towards the observer, 

 the image of the wings becomes larger and more 

 distinct. The body of the fly next passes 

 through the ring of rainbow colours round the 

 circular "window" and blends with the image 

 of the wings. The fly is now seen as a whole, 

 within the "window," as a dull silhouette 

 against the sky. In this position the general 



