them indoors and up to their roof strongholds. When the first warm days of spring sunshine strike against the southern side of the chimney, sparrows perch there and enjoy it; and again in autumn, when the general warmth of the atmosphere is declining, they still find a little pleasant heat there. They make use of the radiation of heat, as the gardener does who trains his fruit-trees to a wall. Before the autumn has thinned the leaves, the swallows gather on the highest ridge of the roof in a row and twitter to each other; they know the time is approaching when they must depart for another climate. In winter, many birds seek the thatched roofs to roost. Wrens, tits, and even blackbirds roost in the holes left by sparrows or starlings. Every crevice is the home of insects, or used by them for the deposit of their eggs--under the tiles or slates, where mortar has dropped out between the bricks, in the holes of thatch, and on the straws. The number of insects that frequent a large roof must be very great--all the robins, wrens, bats, and so on, can scarcely affect them; nor the spiders, though these, too, are numerous. Then there are the moths, and those creeping creatures that work out of sight, boring their way through the rafters and beams. Sometimes a sparrow may be seen clinging to the bare wall of the house; tits do the same thing. It is surprising how they manage to hold on. They are taking insects from the apertures of the mortar. Where the slates slope to the south, the sunshine soon heats them, and passing butterflies alight on the warm surface, and spread out their wings, as if hovering over the heat. Flies are attracted in crowds sometimes to heated slates and tiles, and wasps will occasionally pause there. Wasps are addicted to haunting houses, and, in the autumn, feed on the flies. Floating germs carried by the air must necessarily lodge in numbers against roofs; so do dust and invisible particles; and together, these make the rain-water collected in water-butts after a storm turbid and dark; and it soon becomes full of living organisms.