100 FACTOR IN FAVOUR 



is possible. Wading, again, for this reason, will be the 

 most advantageous position for the fly fisherman. 



It may be argued that the appearance of the waders 

 below the surface, when within the zone of the lateral 

 vision of the trout (see the unshaded portion of 

 Diagram 7), will scare the fish more than the appear- 

 ance of the fisherman above the water. This is not 

 so, however, for the rays of light from the fisherman on 

 the bank, say at 40 feet distance, would lose nothing 

 in passing through the air until they strike and enter 

 the water (as at b B, Diagram 9) ; they will then only 

 have some 3 to 6 feet of water to pass through before 

 reaching the fish. A certain amount of light will be 

 undoubtedly lost, even in this small distance, owing 

 to the density of the water, but the vertical depth of 

 the fish below the surface of any trout stream will 

 never be sufficiently great to prevent all rays reaching 

 it. This density of the water will cause a very rapid 

 diminution of the rays from any sub-aqueous object, 

 as horizontal or vertical distance is attained ; and 

 while objects may, in favourable circumstances, be 

 still visible to the fish 25 feet away in any horizontal 

 direction within the zone of its horizontal light, they 

 may in calm, still waters be taken as being unnotice- 

 able in ordinary circumstances at a distance of about 

 30 feet. In rapid running water the rays from any 

 object will be still further lost or deflected by the 

 eddies, etc. 



From my own experience in a diving-dress in the 

 clear waters of the Torres Straits, which were undis- 



