The thud, thud of a horse's hoof does not alarm fish. Basking in the sun under the bank, a jack or pike lying close to the surface of the water will remain unmoved, however heavy the sound may be. The vibrations reach the fish in several ways. There is what we should ourselves call the noise as conveyed by the air, and which in the case of a jack actually at the surface may be supposed to reach him direct. Next there is the vibration passing through the water, which is usually pronounced to be a good medium. Lastly, there is the bodily movement of the substance of the water. When the bank is hard and dry this latter amounts only to a slight shaking, but it frequently happens that the side of a brook or pond is soft, and "gives" under a heavy weight. Sometimes the edge is even pushed into the water, and the brook in a manner squeezed. You can see this when cattle walk by the margin the grassy edge is pushed out, and in a minute way they may be said to contract the stream. It is in too small a degree to have the least apparent effect upon the water, but it is different with the sense of hearing, which is so delicate that the bodily movement thus caused may be reasonably believed to be very audible indeed to the jack. The wire fences which are now so much used round shrubberies and across parks give a very good illustration of the conveyance of sound. Strung tight by a spanner, the strands of twisted wire resemble a stringed instrument. If you place your hand on one of the wires and get a friend to strike it with his stick, say, thirty or forty yards away, you will distinctly feel it vibrate. If the ear is held close enough you will hear it, vibration and sound being practically convertible terms. To the basking jack three such wires extend, and when the cart-horse in the meadow puts down his heavy hoof he strikes them all at once. Yet, though fish are so sensitive to sound, the jack is not in the least alarmed, and there can be little doubt that he knows what it is. A whole herd of cattle feeding and walking about does not disturb him, but if the light step--light in comparison--of a man approach, away he goes. Poachers, therefore, unable to disguise their footsteps, endeavour to conceal them, and by moving slowly to avoid vibrating the earth, and through it the water.