382 Fly-rods and Fly-tackle. 



tion of the exterior affects the action of the muscles 

 which control the focussing power of the lens within, 

 and whose office it is to form the image upon the retina. 

 We also know that, unless these muscles duly perform 

 their appointed duty, the eye is as powerless to convey 

 to the brain a truthful image as is a telescope, the dif- 

 ferent lenses of which have not been relatively adjusted 

 to distinct vision. We have all, either in frolic or from 

 necessity, tried to see through a pair of spectacles to- 

 tally unsuited to our eyes, and we all know the result. 

 Again, though the mechanism of the eye work perfectly, 

 still so intimate is the relation of its various parts, so 

 profound their sympathy one with the other, that the 

 power of the retina to receive and transmit a perfect 

 image, even were such a one formed upon it, may well 

 be doubted under such circumstances. 



A gentleman well known in angling circles, and an ac- 

 knowledged authority, when spoken to of the intended 

 experiments, said that it was all useless ; that he had 

 tried it when in swimming ; that everything appeared 

 black, and that I would be able to see nothing. Subse- 

 quently another gentleman tried submerging himself 

 below the surface of the water, and passing gut of dif- 

 ferent colors before his eyes. He found very dark gut 

 alone was visible, and that only at a distance of twelve 

 or fifteen inches. It is clear, therefore, that in the un- 

 usual conditions in which the eyes of the gentleman first 

 mentioned were then placed, they refused to act at all; 

 and that the same was the case in the other instance, 

 though in less degree, and that the same will be the case 

 with every one's eyes to a greater or less degree, under 

 such unusual conditions, I cannot doubt. The gentleman 

 last named could distinguish only very dark gut, and at a 



