POWER OF VISION. 3 



object that may be even a yard from the water's 

 surface. We have stood over the centre of a stream, 

 upon a narrow plank, placed within a few inches 

 of the surface of the water, perfectly motionless, 

 just as the fish have turned out of their usual haunts 

 to poise near the surface to feed on the flies which 

 have suddenly become plentiful. So long as our per- 

 pendicular position was maintained the fish rose fear- 

 lessly all around to our very feet, but the least 

 movement had the effect of affrighting all the fish 

 in the immediate vicinity. 



But, notwithstanding all this, it must not be for- 

 gotten that the organ of sight is the most important 

 in their possession, and not only their food supply, 

 but their very existence is dependent upon its proper 

 exercise. True it is that constant practice, in a 

 measure, develops their ocular faculties ; and as acute- 

 ness of vision increases the natural timidity of the 

 trout, so surely does he gradually decline surface 

 feeding, preying upon fry and the smaller yearling 

 fish, as also upon the larvae of aquatic insects, etc., 

 thus showing reliance on his greater powers of dis- 

 cernment in his own element. In comparatively clear 

 and still water, the old corpulent denizens of the 

 limpid depths thus exhibit the most provoking dis- 

 cretion, defying frequently the rodster's best efforts 

 to allure. 



The superior power of vision the fish has in. its 

 own element is partly due to the fact that light, like 

 sound, on penetrating water suffers an alteration both 

 of the rate of progress and the direction of the 



