That night, after their father had gone off clanking to his furnaces, Dorcas heard her brother tapping on the partition between their rooms, as he did sometimes when they played "prisoner." She knew exactly what he meant by it and tapped back that she was ready. Everything worked out just as they had planned. They heard the strange, hollow-sounding echoes of the watchman's voice dying down the halls, as stair by stair they dropped the street lamps below them, and saw strange shadows start out of things that were perfectly harmless and familiar by day. There was no light in the gallery except faint up-and-down glimmers from the glass of the cases, and here and there the little spark of an eye. Outside there was a whole world of light, the milky way of the street with the meteor roar of the Elevated going by, processions of small moons marching below them across the park, and blazing constellations in the high windows opposite. Tucked into one of the window benches between the cases, the children seemed to swing into another world where almost anything might happen. And yet for at least a quarter of an hour nothing did. "I don't believe nothing ever does," said Dorcas Jane, who was not at all careful of her grammar. "Sh-sh!" said Oliver. They had sat down directly in front of the Buffalo Trail, though Dorcas would have preferred to be farther away from the Polar Bear. For suppose it hadn't been properly stuffed! But Oliver had eyes only for the trail. "I want to see where it begins and where it goes," he insisted. So they sat and waited, and though the great building was never allowed to grow quite cold, it was cool enough to make it pleasant for them to sit close together and for Dorcas to tuck her hand into the crook of his arm.... All at once the Bull Buffalo shook himself. [Illustration: Line Art of Mastadons] II WHAT THE BUFFALO CHIEF TOLD "_Wake! Wake!_" said the Bull Buffalo, with a roll to it, as though the word had been shouted in a deep voice down an empty barrel. He shook the dust out of his mane and stamped his fore-foot to set the herd in motion. There were thousands of them feeding as far as the eye could reach, across the prairie, yearlings and cows with their calves of that season, and here and there a bull, tossing his heavy head and sending up light puffs of dust under the pawings of his hoof as he took up the leader's signal. "Wake! Wa--ake!" It rolled along the ground like thunder. At the sound the herds gathered themselves from the prairie, they turned back from the licks, they rose up _plop_ from the wallows, trotting singly in the trails that rayed out to every part of the pastures and led up toward the high ridges. "Wa-ak--" began the old bull; then he stopped short, threw up his head, sniffing the wind, and ended with a sharp snort which changed the words to "_What? What?_" "What's this," said the Bull Buffalo, "Pale Faces?"