Dick could not go to sleep for a long time. From the point where he lay he could now see two of the sentinels walking back and forth, rifle on shoulder. He did not believe that they would continue to do so many hours, and he had a vague sort of desire to prove that he was right. Having nothing else to do he watched them.
The nearer sentinel grew lazier in his walk, and his beat became shorter. At last he dropped his rifle to the ground, leaned his folded arms on its muzzle, and gazed toward the camp, where, so far as he could see, there was nothing but darkness and sleep. The other presently did the same. Then they began short walks back and forth, but soon both sat down on the ground, with their rifles between their knees, and after that they did not stir. Watching as closely as he could Dick could not observe the slightest movement on the part of either, and he knew that they were asleep. He laughed to himself, pleased, in a way, to know that he had been right, although it was only another evidence of the carelessness and indifference general throughout the train.
He fell asleep himself in another half hour, but he awoke about midnight, and he was conscious at once that he had been awakened not by a troubled mind, but by something external and unusual. He was lying with his right ear to the ground, and it seemed to him that a slight trembling motion ran through the solid earth. He did not so much hear it as feel it, and tried to persuade himself that it was mere fancy, but failed. He sat up, and he no longer observed the trembling, but when he put his ear to the ground again it was stronger.
It could not be fancy. It was something real and extraordinary. He glanced at the sentinels, but they were sound asleep. He felt a desire to rouse somebody, but if it proved to be nothing they would laugh at him, or more likely call him hard names. He tried ear to earth once more. The trembling was still growing in strength, and mixed with it was a low, groaning sound, like the swell of the sea on the shore. The sound came with the wind from the north.
Dick sprang to his feet. There, in the north was a faint light which grew with amazing rapidity. In a minutes almost it seemed to redden the whole northern heavens, and the groaning sound became a roll, like that of approaching thunder.
A shadow flitted by Dick.
"What is it, Bright Sun?? What is it?" exclaimed the boy.
"The dry grass burns, and a mighty buffalo herd flees before it."
Then Bright Sun was gone, and the full sense of their danger burst upon Dick in overwhelming tide. The flames came on, as fast as a horse's gallop, and the buffaloes, in thousands and tens of thousands, were their vanguard. The camp lay directly in the path of fire and buffalo. The awakened sentinels were on their feet now, and half-clad men were springing from the wagons.
Dick stood perfectly still for perhaps a minute, while the fire grew brighter and the thunder of a myriad hoofs grew louder. Then he remembered what he had so often read and heard, and the crisis stirred him to swift action. While the whole camp was a scene of confusion, of shouts, of oaths, and of running men, he sped to its south side, to a point twenty or thirty yards from the nearest wagon. There he knelt in the dry grass and drew his box of matches from his pocket. It happened that Conway saw.