THE INSTINCT AND SENSES OF FISH. 241 



less in either case the position and power of light above 

 are more important factors than when the object is 

 immersed. 



To the immersed human eye, when gazing upwards, 

 the surface, under certain conditions of light, appears 

 as of molten lead, impenetrable to the eye, and a some- 

 what similar effect is produced by a broken surface — 

 both tending to impede the view of fish as regards 

 matters upon or near the surface ; and old anglers may 

 be heard to remark, that " no good will be done with 

 that 'glint' on the pool/' 



A tray with glass bottom, placed upon rough water, 

 will reveal the position of any object, which previously 

 was hidden, by refraction of light. 



When resting in heavy boiling water, fish either 

 cannot see, or, being intent on other business diverting 

 their attention, do not exercise the faculty against 

 objects above water; for upon many occasions while 

 standing at the foot of a fall we have, with a crooked 

 stick, lifted a salmon half out of the water without his 

 having given any signs of alarm, but when we ad- 

 vanced a few yards away he went. 



Now, in consideration of the want of positive proof 

 as to the comparative invisibility to fish of materials of 

 various hues when immersed in water, the question 

 arises, — Had we not better be guided by hints pro- 

 vided by nature ? 



In these pages we have previously had occasion to 

 allude to the heron, and we must revert to him ; for, 



R 



