Bowled over by a huge sloth, Gridley scrambled to his feet, and, passing in front of a fleeing mastodon, reached the tree just as the main body of the stampeding herd closed about it. Its great bole gave him momentary protection and an instant later he had scrambled among its branches. Instantly his first thought was for his fellows, but where they had been a moment before was now only a solid mass of leaping, plunging, terrified beasts. No sign of a human being was anywhere to be seen and Gridley knew that no living thing could have survived the trampling of those incalculable tons of terrified flesh. Some of them, he knew, must have reached the forest, but he doubted that all had come through in safety and he feared particularly for Von Horst, who had been some little distance in rear of the Waziri. The eyes of the American swept back over the clearing to observe such a scene as probably in all the history of the world had never before been vouchsafed to the eyes of man. Literally thousands of creatures, large and small, were following their leaders in a break for life and liberty, while upon their flanks and at their rear hundreds of savage saber-tooth tigers leaped upon them, dragging down the weaker, battling with the stronger, leaving the maimed and crippled behind that they might charge into the herd again and drag down others. The mad rush of the leaders across the clearing had been checked as they entered the forest, and now those in the rear were forced to move more slowly, but in their terror they sought to clamber over the backs of those ahead. Red deer leaped upon the backs of mastodons and fled across the heaving bodies beneath them, as a mountain goat might leap from rock to rock. Mammoths raised their huge bulks upon lesser animals and crushed them to the ground. Tusks and horns were red with gore as the maddened beasts battled for their lives. The scene was sickening in its horror, and yet fascinating in its primitive strength and savagery--and everywhere were the great, savage cats. Slowly they were cutting into the herd from both sides in an effort to encircle a portion of it and at last they were successful, though within the circle there remained but a few scattered beasts that were still unmaimed or uncrippled. And then the great tigers turned upon these, closing in and drawing tighter their hideous band of savage fury. In twos and threes and scores they leaped upon the remaining beasts and dragged them down until the sole creature remaining alive within their circle was a gigantic bull mammoth. His shaggy coat was splashed with blood and his tusks were red with gore. Trumpeting, he stood at bay, a magnificent picture of primordial power, of sagacity, of courage. The heart of the American went out to that lone warrior trumpeting his challenge to overwhelming odds in the face of certain doom.