8 THE SCIENTIFIC ANGLER. 



at a depth of eight or ten feet of water, can distinguish 

 a small speck of a midge, invisible almost to the human 

 eye, is often a matter of comment and surprise. All 

 fish, however, are not equally well endowed in this re- 

 spect; but it may be safely affirmed that their organs of 

 sight are quite as well adapted to their native element 

 water as are those of birds and respiratory animals 

 generally to the atmosphere. But, on the other hand, 

 experience tends to prove that the more suited the eye of 

 the fish may be to his particular element, the more in- 

 distinct is his vision beyond it. We have an instance of 

 this in the grayling, which, although more cautious and 

 timid, and possessed of keener visual organs than the 

 trout, will rise much nearer the rodster, and is not so 

 easily disturbed and affrighted. The inferiority of a 

 fish's perception of objects in the air, as compared with 

 what is in or upon the surface of the water, partly arises 

 from the fact that the eye adapts itself to the medium 

 through which the rays of light are transmitted. We 

 have frequently observed the pupil of a fish's eye con- 

 tract considerably in the course of a second or two after 

 it has been taken from the water, from the same princi- 

 ple which causes the pupil of the eye of the domestic cat 

 to expand or contract as the light diminishes or increases. 

 Observation shows that it is the moving object that 

 frightens the fish.* We have seen trout suddenly cease 

 feeding and return to their accustomed retreat upon our 

 merely raising an arm; and when their "holt" has 

 proved to be near the opposite bank, and we have been 



* Fish are startled by shadows to a degree hardly understood or 

 valued, as cause and effect, by the angler in his search for a successful 

 score. A moving dark line reflected by an uplifted arm, or by an 

 overhanging rod, or the dense and sharply-cut shadow cast by the 

 pier of a bridge, will cause them to sheer off affrighted ; especially in 

 the latter instance, when shad, in their upward swim to their spawning 

 grounds, have been seen to turn tail-fin and dart down stream pell-mell, 

 as if a demon shark was among them. 



