Only the other day, May brought me a lovely branch of white coral. "Look," she said, "when baby was out for a walk, a lady gave her this." She thought it very pretty, but she was surprised when I showed it to her through a magnifying-glass, and told her that it had been made by a very tiny kind of jelly-fish; a plant-animal some people call it, of the same kind as the sea-anemone; and she wondered still more when we found in a book a picture of a coral island, and I told her that such little creatures have been busy ever since the world began, constantly building up the coral-rocks. These rocks, which are strong enough to resist the force of the waves, rise out of the sea naked and bare, but are soon covered with green, and become the resting-place of the sea-birds, until at last they are like that lovely island, fringed with tall cocoa-palms, which we saw in the picture. If it were not for the myriads of tiny jelly-fishes, who work on and on, each forming its own little bones from the lime it gets from the sea-water, dying, and leaving its skeleton behind for others to build upon, there would be none of these beautiful green isles of the sea of which sailors love to tell us. We were speaking of contrasts some time ago; now for a contrast. Beside the coral, with its lovely branching sprays, we will put a piece of coal. You think the coal very black and ugly, not fit to be put alongside the white coral; but let me tell you that there is that in the coal which was once far more beautiful than the coral--which is only a bare skeleton after all--could ever be; for, though coal and coral are alike dead now, both were once full of life. But the coal, which is certainly more useful than beautiful at present, has had a wonderful past. Besides the fossil-animals which are dug out of the earth's crust, there are also fossil-trees and ferns, and it is of them that coal, which seems only like a black stone, is made. I have read that in a part of England where there are now great coal mines, for a long time no one knew the worth of coal except some old women, who said they could make their fires burn beautifully by putting those black bits of stone upon them. How strange this seems; and what should we do now if we had not these black stones to burn? Coal is generally called a mineral, as all things which are dug from mines are called; but it is really a vegetable. You may perhaps pick up in some swampy place, a piece of wood, very black, which breaks as you handle it. Look at it well, for this wood is being turned into coal; but for what was once a forest to become a coal-mine takes a very long time indeed, with a strange history of change and decay; yet it is true that the coal dug out of mines is nothing else than trees and ferns and mosses, long ago buried by mud and sand, and so crushed together that they have become like a piece of black stone.