CHAP. VI. 



Angles of Vision in Water. 



99 



at B, the line of sight taking the course CAB. It is true this cuts both 

 ways, enabling you, as well as the fish, to see round a corner, but as 

 you neither of you should see each other, 

 it is an argument for keeping further away 

 from the bank than if you both saw in a 

 straight line. 



But I have comfort for you yet from ^ 

 the laws of refraction and reflection. A 

 fish cannot see you out of the water at 

 an angle of more than 48^, which is 

 K D E in the second diagram, KEF 

 being the surface of the water, and K D D/ 

 the perpendicular. If it tries a more 



obtuse angle, as K D F, the under surface of the water is like a mirror 

 to it, and reflects to it the bottom at B, just as you see the surface of 

 the water reflect to you the trees on the opposite bank. 



Allowing for the refraction shown in the former diagram, a fish 

 looking out at the angle D E would see you not at A but at H, so that 



if your head is below the line 

 E H it would not be visible to 

 a fish at D ; but if you are 

 wading, and within the line F B, 

 your legs would be visible by 

 reflection at D, unless the move- 

 ment of the water hid you. 

 This is the law which accounts for stooping, or lying down on the 

 bank, or getting to a lower level by wading, concealing you from a fish. 

 But in wading you must remember that water conveys sounds made 

 in the water well, and fish are surprisingly sensitive of sounds made 

 under water. It is said that in still water a stone striking the bottom, 

 or a rupee in a swimming bath, lightly though it falls, can be heard 

 a long way off by a person under the water, though he could not hear 

 his friends shouting to him above the surface of the water. So you 

 should wade quietly, not flounderingly. 



If you are not fishing, but wanting to observe the habits of fish, and 

 can afford to be perfectly motionless, that is quite another thing. Much 

 may be seen by creeping very slowly and imperceptibly up, with a rock 

 or tree-trunk for a background, and remaining perfectly motionless. It 



H 2 



K 



H 



