Harkness glanced quickly about to size up their situation. To go on was certain death; if these creatures came up to meet them on the lava-beds, the end was sure. The escarpment gave the three some slight advantage of a higher position. One vain wish for the pistol now resting in the deep grass beside a vanished ship; then he sprang for the weapon that had been thrown--it was better than nothing--and advanced cautiously to the lava's edge. No concealment there; no broken rocks, other than pieces of flint; a poor fortress, this, that they must defend! And the weapons of their civilization were denied them. Another spear hummed its shrill song, coming dangerously close. He saw women-figures that came from the jungle with supplies of weapons. Short spears, about six feet long, like the one he held. But they had others, too--long lances of slender wood with tips of flint. Thrusting spears! He had a sickening vision of those jagged stone heads ripping into their bodies while these beasts stood off in safety. It was thus that they killed their prey. And Diane--he could not even spare her--could not give her the kind oblivion of a mercy-shot! The other two were lying beside him now at the edge of the sloping cliff. The bank of shining gray was not steep; the enemy would climb it with ease. Hopeless! They had won through for this!... Harkness groaned silently in an agony of spirit at thought of the girl. "Oh, for one detonite shell to land among them!" he said between clenched teeth--then was breathless with a thought that exploded within his mind. * * * * * His fingers were clumsy with haste as he fumbled at the head of the spear. The sharp-edged stone was bound to its shaft with sinew, wound round and round. The enemy were out in the open; he spared an instant's look to see them advancing. A clattering of falling spears sounded beyond, but the weapons were overcast, thanks to the protection of the rocky edge. "A shell!" Harkness spoke with sharp intensity. "Give me a cartridge from your belt, quick!" Chet handed him one. Harkness took one look, then pulled a cartridge from his own belt. "That explains it," he was muttering as he worked, "--the big explosion when I smashed the rocks. You've got ammunition for your pistol, but you put rifle cartridges in my belt--and service ammunition at that. No wonder they raised the devil with those rocks!" His fingers were working swiftly now to bind the slender cartridge to the spear. A chipped out hollow in the flint made a seat. He gave silent thanks for Chet Bullard's mistake. Chet had slipped; he had filled Harkness' belt with ammunition that would have been useless for the pistol--but it was just what he needed here. So intent was he on his task that he hardly heard the yelling chorus from below. It swelled to a din; but his work was finished, and he looked up.