There is a spot by a yet more quiet bridge, where the little water-shrews play to and fro where the bank overhangs. As they dive and move under water the reddish-brown back looks of a lighter colour; when they touch the ground they thrust their tiny nostrils up just above the surface. There are many holes of water-rats, but no one would imagine how numerous these latter creatures are. One of Hilary's sons, Hugh, kept some ferrets, and in the summer was put to it to find them enough food. The bird-keepers brought in a bird occasionally, and there were cruel rumours of a cat having disappeared. Still there was not sufficient till he hit on the idea of trapping the water-rats; and this is how he did it. He took three small twigs and ran them into the bank of the brook at the mouth of the water-rat's hole and just beneath the surface of the stream. These made a platform upon which the gin was placed--the pan, and indeed all the trap, just under the water, which prevented any scent. Whether the rat came out of his hole and plunged to dive or started to swim, or whether he came swimming noiselessly round the bend and was about to enter the burrow, it made no difference; he was certain to pass over and throw the gin. The instant the teeth struck him he gave a jump which lifted the trap off the twig platform, and it immediately sank in the deep water and soon drowned him; for the water-rat, though continually diving, can only stay a short time under water. It proved a fatal contrivance, chiefly, as was supposed, because the gin, being just under the water, could not be smelt. No fewer than eleven rats were thus captured in succession at the mouth of one hole. Altogether 150 were taken in the course of that summer. Hugh kept a record of them by drawing a stroke with chalk for every rat on the red brick wall of the stable, near his ferret-hutch. He only used a few traps--one was set not at a hole, but at a sharp curve of the brook--and the whole of these rats were taken in a part of the brook about 250 or 300 yards in length, just where it ran through a single field. The great majority were water-rats, but there were fifteen or twenty house-rats among them: these were very thin though large, and seemed to be caught as they were migrating; for sometimes several were trapped the same day, and then none (of this kind) for a week or more. Three moorhens were also caught; a fourth was only held by its claw in the gin; this one, not being in the least injured, he let go again.