Much of the opalized wood is very beautiful. The change brightened and intensified the former texture of the wood. In most of these stone trees and logs the annual rings show clearly. They distinctly reveal the age of the tree and its rapidity of growth. In many cases the species is readily determined. Strange stories are told by the fallen logs, in many of which old worm-holes show. The half-decayed logs were preserved in their original form, and in the process of fossilization their hollow interiors were filled with beautiful rosettes and crystals. Each of the buried forests contained some trees of different species from those in the forest just beneath it. Altogether, more than eighty kinds have been recognized. Many of these would grow only in a mild or subtropical clime, so the former climate of this region must have been warmer than at present. Among the trees were redwood, cottonwood, walnut, pine, oak, sycamore, fig, magnolia, and dogwood. Ancient Troy was nine ruined cities deep. But here in a national playground of our own country are twelve tree cities in ruins, one above another, and topped with a city of living trees. Like the excavated ruins of Pompeii, these ruined forests set one's mind to exploring the realm of imagination. Here in a subtropical clime, possibly a million years ago, was a luxuriant forest. Beneath was a crowded undergrowth of plants, of shrubbery and waving ferns. Gay butterflies may have flitted here in the golden sunshine. Trees enjoyed the storms and lifted their heads serenely into the light. Then came the tragic end. Twelve times or more was this impressive drama reënacted. Trees, like men, often rear their structures upon the ruins of those that have gone before. This is an old, old world. In the words of Omar,-- "When You and I behind the Veil are past, Oh, but the long, long while the World shall last." Is the volcanic curtain once more to fall upon the forests of this magic scene? In "Our National Parks" John Muir comments eloquently upon the fossil forests and the telling background of most Yellowstone landscapes. He says:-- Yonder is Amethyst Mountain, and other mountains hardly less rich in old forests, which now seem to spring up again in their glory; and you see the storms that buried them--the ashes and torrents laden with boulders and mud, the centuries of sunshine, and the dark, lurid nights. You see again the vast floods of lava, red-hot and white-hot, pouring out from gigantic geysers, usurping the basins of lakes and streams, absorbing or driving away their hissing, screaming waters, flowing around hills and ridges, submerging every subordinate feature. Then you see the snow and glaciers taking possession of the land, making new landscapes. How admirable it is that, after passing through so many vicissitudes of frost and fire and flood, the physiognomy and even the complexion of the landscape should still be so divinely fine!