28 MARVELS OF FISH LIFE 
appears to sparkle with glittering light. Next moment 
nothing is visible, and in a minute or two similar flashes 
of light are to be observed in quite a different part of 
the water. These flashes are caused by the young fish 
simultaneously wheeling round with the precision of a 
crack regiment. 
The fact that objects seen from below appear as 
silhouettes against the sky, explains why many fish 
on the look-out for food lie near the bottom. The spin- 
ning bait, or the fly, fished just under the surface, will 
bring up the salmon, the trout or the pike from the 
bottom of the deepest hole. 
I well remember watching from the bridge above 
the fishing of a pool on the Dee. A sunk fly was fished 
past and in front of a salmon lying on a ledge of rock 
without response, but when fished right above him he 
twice came up to inspect it. I do not suggest that the 
salmon could not see the deep fished fly, but that when 
fished right above him it was much more obvious 
against the sky, and so attracted his attention. I would 
mention in passing that the most gaudy fly seen against 
the surface of the water merely appears as a grey, 
iridescent silhouette, and for this reason I do not think 
the colour of the fly matters if the size be right for the 
condition of the water and the fly be fished so as to 
suggest life. 
Having so fully considered both concealing colora- 
tion and reflection in the silvery dace, let us turn our 
attention to fish in which colour plays the greater part 
