Page:The Life of the Fields, Jefferies, 1884.djvu/174

160 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 reason-