“Do we not daily read footprints in sand in this fashion? As we came here we crossed the road lying deep in summer dust. There in the dust were the prints of a three-toed foot. We recognized the size and shape; it was the track of a hen’s foot; a large fat hen we judged, because the prints were large and deeply indented. Around her tracks were the small delicate marks of the feet of young chicks. There were many of them; evidently the hen had a large brood with her. Here she had scratched in the dust where some grain or meal had been scattered: here was a deep hollow where the dust was flirted about on all sides; the hen had been taking a dust-bath. Here were some much larger marks of three-toed feet, their distance apart showing a longer stride: we felt quite certain that a big rooster had marched that way. We knew about the hen, the chicks, the cock, the feeding, the wallowing, as well as if we had watched the birds themselves and their performances. But we had only seen footprints in the sand. Has any one of us wondered at Robinson Crusoe’s conclusions when on the beach he found the print of a naked human foot?” The pupils admitted the justice of this reasoning. “What else have you read?” they questioned. “Shortly after the shower an animal passed this way; a two-legged animal with three-toed feet, and a stride six feet in length. Such a creature would make an ostrich seem small. Whether it was a bird or a lizard I cannot tell, at all events it has neither kindred nor descendants in the modern era. If a bird, it was of that antique type which had teeth and no feathers and wore a lizard’s tail. It was probably a wader of some kind, and ate mollusks and fish. I say that it passed this way about the time of the shower, because I find its footprints near the rain-marks, and on the same level of rock, and because they seem to have been covered up about the same time, and in the same manner.” “Do you suppose if we broke up some of this rock we should find remains of the living creatures that moved over it?” “No; sandstone is not rich in fossils. Perhaps the oxide of iron that frequently accompanies the sand has destroyed plant and animal organisms, or it may be that when the heavy quartz grains dropped out of the water, the plant and animal remains were carried off by tides or currents. Still, in some parts of the world fossils are found in sandstones.” “Do all the strata of sandstone tell this same story?” “Each varies the story somewhat to suit its own circumstances. Some tell us which way the tides flowed and the rivers ran that brought them to their resting places long ago.” “Are all sandstones alike, except in color?”