Safe from all save mink and owl and trap, these sturdy muskrats spend the summer in and about the streams; and when winter shuts down hard and fast, they live lives more interesting than any of our other animals. The ground freezes their tunnels into tubes of iron,--the ice seals the surface, past all gnawing out; and yet, amid the quietly flowing water, where snow and wind never penetrate, these warm-blooded, air-breathing muskrats live the winter through, with only the trout and eels for company. Their food is the bark and pith of certain plants; their air is what leaks through the house of sticks, or what may collect at the melting-place of ice and shore. Stretched full length on the smooth ice, let us look through into that strange nether world, where the stress of storm is unknown. Far beneath us sinuous black forms undulate through the water,--from tunnel to house and back again. As we gaze down through the crystalline mass, occasional fractures play pranks with the objects below. The animate shapes seem to take unto themselves greater bulk; their tails broaden, their bodies become many times longer. For a moment the illusion is perfect; thousands of centuries have slipped back, and we are looking at the giant beavers of old. Let us give thanks that even the humble muskrat still holds his own. A century or two hence and posterity may look with wonder at his stuffed skin in a museum! NATURE'S GEOMETRICIANS Spiders form good subjects for a rainy-day study, and two hours spent in a neglected garret watching these clever little beings will often arouse such interest that we shall be glad to devote many days of sunshine to observing those species which hunt and build, and live their lives in the open fields. There is no insect in the world with more than six legs, and as a spider has eight he is therefore thrown out of the company of butterflies, beetles, and wasps and finds himself in a strange assemblage. Even to his nearest relatives he bears little resemblance, for when we realise that scorpions and horseshoe crabs must call him cousin, we perceive that his is indeed an aberrant bough on the tree of creation. Leaving behind the old-fashioned horseshoe crabs to feel their way slowly over the bottom of the sea, the spiders have won for themselves on land a place high above the mites, ticks, and daddy-long-legs, and in their high development and intricate powers of resource they yield not even to the ants and bees. Nature has provided spiders with an organ filled always with liquid which, on being exposed to the air, hardens, and can be drawn out into the slender threads we know as cobweb. The silkworm encases its body with a mile or more of gleaming silk, but there its usefulness is ended as far as the silkworm is concerned. But spiders have found a hundred uses for their cordage, some of which are startlingly similar to human inventions.