zest which friendly chat often imparts to the exercise of our captivating art, need never be marred by an apprehension that sport will be impaired thereby.

Sight.

Of all the senses in fish, sight is perhaps that which is of most importance to them. Their eyes are of course well adapted to the element they inhabit; indeed their subsistence seems to depend mainly upon the great sensibility of the optic nerve, and the just adaptation of the crystalline and other humours to their proper office.

A fish can perhaps frequently distinguish much more of objects which are out of his own element than it is often imagined that he can.

When Mr. A. B. (fig. 1, plate 2), for instance, situated upon a certain eminence at a given distance from a fish, C, which is near the bottom of the water, looks over the edge of a bank, D, in the direction AFZ, he might (if unacquainted with the laws of refraction) imagine, that neither the fish C, nor any other fish below the line of his direct vision, AFZ, could see him; whereas C could see A B by means of the pencil of light, AFCEB, bent, or refracted at the surface of the water, EF, and the image of AB would appear in the eye of the fish shortened and transferred to GH. The fish, in fact, could see the whole of

the man, round, or over the corner of the bank, by the aid of the water above C, if both were situated as respectively represented in the diagram; but if the surface of the water should be at IK, (i.e.) about as low as the fish's eye, then he could not see any part of the figure AB, because a straight or unrefracted pencil of light, ACB, would be obstructed by the bank.

Increased obliquity in pencils of light falling from an object upon a surface of water, is accompanied by still more rapidly increasing refraction but the distinctness with which the object is seen decreases in an inverse proportion.

The bending or refraction which a pencil of light, as NEOFM (fig. 2), falling very obliquely upon the surface of the water, undergoes before arriving at the eye of a fish, at O, is sufficient to produce very great indistinctness and distortion of the image of MP formed in his eye.

Perhaps indistinctness of vision may, on other accounts, also take place in the eye of a fish looking through air. The crystalline and various other humours may not be capable of such comprehensive adjustment as would enable him to see so distinctly through air as he can through

water.

But long before a pencil of light as, NE L, becomes horizontal, it will not enter the water at

at MP, he new posiill be very part, N L, il, NE L, he will see

water), beobstruction MP will,

o portions,

ng unsub

le theorems ovious.

lmost on a

Ivantage to

ess distinctving gravel and other Ivantageous

wn optical laws, A E f, of a ray the sine, c d, of three; and seif the angle of es, but will be

all; consequently, although the fish at O may see the upper part of the man situated at MP, he will do so very indistinctly, and in a new position, because the pencil N E OF M will be very much refracted; he will not see the part, N L, of the man at all, because the pencil, N E L, does not enter the water at all; and he will see probably his legs, L P (in the clear water), because there is neither refraction nor obstruction to prevent him. So that the figure M P will, in the eye of the fish, be cut into two portions, separated from each other by a long unsubstantial interval.1

The application of those two little theorems to the use of the fisherman is very obvious.

In the first place, a low bank, almost on a level with the water, is a great advantage to the fisher, who is there seen with less distinctness by his game: thus the shelving gravel beds which reach far into the Dove, and other Trout streams, are so many most advantageous positions for the angler. (Pl. I. K.)

1 This diagram is constructed on two well-known optical laws, viz. first, the sine a. b. of the angle of incidence, A E f, of a ray of light passing out of air into water, is always to the sine, c d, of the angle of refraction, C E e, as about four to three; and secondly, light will not pass out of air into water, if the angle of incidence, N E f (fig. 2) exceeds about 88 degrees, but will be reflected.

The old experiment of the shilling and the basin of water affords an easy practical demonstration of the first theorem in the text.