OPTICS OF FISHES. 153 



the " Flj-Fisher's Entomology," that by the 

 refraction of the rays of light passing through 

 the water, a fish lying under a bank, which inter- 

 venes and almost prevents you seeing the surface 

 even of the water immediately over him, can per- 

 ceive you most distinctly. This is too well known 

 to require me to explain " the why and where- 

 fore ;" so if you are afraid of exposing your 

 ignorance by asking me more concerning it, look 

 at Mr. Ronalds' work, and there you will learn all 

 you need ; or else, any popular work on optics, 

 will tell you. 



Herb. — Now, my friend, let one of us begin 

 fishing ; for I long to see a salmon ashore. 



Theoph. — Patience, patience ! Don't you see 

 the " sun shines high and bright." It would be 

 most imprudent to make even one cast just now : 

 especially as there are clouds coming up, which 

 will, every now and then, screen his rays. As a 

 general rule, no " surface fish " will rise at a fly 

 during sunshine. Some suppose (and perhaps 

 very properly) that this is because they see the 

 angler, or his rod and line, too plainly, or are, by 

 the superior light, able to detect that the bait 

 offered is merely artificial. But I am not quite 

 satisfied that this is the true or sole reason, though 

 scarcely quite prepared to offer a better ; since 

 these phenomena are still occupying my deepest 

 attention. The rays of the sun, or the absence 



