They tried to keep as near to one another as possible. The one danger Dick feared more than anything else was that one of the horses in this headlong gallop might set his feet in a marmot hole, and bring about disaster; for a spill in the face of the oncoming army of buffaloes would mean that the unfortunate one must be trampled under foot, whether his horse had a leg broken or not. When first seen the buffaloes had apparently been simply galloping steadily on, as though bent on changing their feeding grounds; but Dick, turning to look with each flash, believed he could detect a change coming over their method of advance. This was doubtless caused by the increasing crashes of thunder that sounded high above the steady roar of those tens of thousands of hoofs beating upon the hard turf. In other words, as the oncoming storm began to overtake the drove, their gallop was fast degenerating into a stampede, when every animal would put on its best spurt, and, wild with fear, seek to outrun the threatening gale. Already the horses were doing their best, and it was folly to dig one's heels into the sides of his straining beast, as Roger was doing, seeking to obtain a little more speed. And now both boys began to look anxiously ahead. Despite the best efforts of the horses it seemed as though the leading buffaloes were much closer to them than when the mad race had started; and this meant that, unless they could manage to gain the shelter of the trees, they were going to have a hard time of it avoiding disaster. Already Roger had learned that his comrade had guessed true when he said that the indistinct line along the horizon, seen just at sunset, must be trees. They had become much more distinct by now, so that, although but a fleeting glimpse of them could be obtained when the lightning flashed, still that was enough. And now the rain started to fall, but neither cared for that, if only it did not interfere with their striking the timber belt at its nearest point. Probably neither of those boys would ever forget that wild ride, with the thunder booming all around them; the lightning seeming to strike here, there, and everywhere; the rain falling in a deluge that soon soaked them to the skin; and, worst of all, that endless line of galloping bison gaining constantly, as they were urged on by their fright. Once Roger's horse stumbled, and the boy came near falling, only retaining his seat because he had firmly fixed himself there. His heart seemed to jump into his throat with a sudden fear lest the animal had lamed itself, and would prove unequal to the task of keeping ahead of the oncoming herd. But, so far as could be seen, the horse did not show any signs of injury. "Can we make it, Dick?" It was necessary for Roger to shout, although at the time he could not have been ten feet away from his companion. The combination of noises all around them prevented such a small thing as a human voice from being heard, unless strained to the utmost.