The river flows away out of the lake through a broad opening in the reeds. We row in there, and then let ourselves drift, just guiding the boat with gentle strokes of the oar, until we leave the reeds behind us, and move on the running river between green banks, thick with bush and rough with rocks. Here on the banks we sometimes see the remains of a dead fish half pulled to pieces. We know what that means, "The otter," says the Imp, and we stare about with eyes wider than before, doing our best to imagine in very stir in the bushes or under the banks that we can see his dark body, like a beaver, for he can swim in the water and dive like a fish, and run along the bank as well. But we have never seen him, though we know that he is there. And otters are growing fewer and fewer. Every year men and women with dogs come to hunt them and kill them. Some day there will be no otters left at all. We wait in the river till the evening, and then set out to row the long way back again. As we row up the river into the lake again we can see the trout rising in big circles of ripples, and hear the peewits screaming on the marshland. It is odd how we seem to notice sounds at evening that we should not at other times. Everything seems so quiet that little noises seem to matter. When we hear the frogs croaking we do not think how loud they are, but only how silent is everything-else. It is evening now, when we row round the promontory at the low end of the lake, and already we are wondering if we shall get home before the owls begin to call. Long ago the Imp and the Elf should have been asleep in bed. The lake is very still, and the sky is less brilliant than it was. The sun has dropped below the hills, and their outlines are clear against the rose of the sunset. The Imp and the Elf say nothing, but listen for the night noises, and watch the sky working its miracles in colour. This evening is a new dream world for them, and they are wondering whether the water people are awake or asleep. "There never is a time when everything goes to bed, is there?" says the Elf, sleepily, as we lift her out of the boat. And as the two of them go off to bed, very happy and very, very tired, we can hear the long kr-r-r-r-r-r of the nightjar in the pinewoods up the hills, and below us in the woods at the head of the lake two owls are answering each other. V OUR OWN AQUARIUM