when ten, twenty, and thirty minutes passed and there was no flow of molten metal hope began to die. Cliff gave a despondent motion at last and cut out the switches,
"No dice," he muttered, tugging his goggles free. They stood surveying the blackened but otherwise unharmed patch where the rays had played. "It's not even scratched, and Heaven knows how thick it is. We haven't enough heat. . . . Titanite might do it." He stood looking toward the door impatiently but there was no sign of Morton or Sparks, no sounds from beyond the cavern.
"They're the devil of a time," Townshend said uneasily.
"Say, do you think. . . ." Val put his pipe solemnly in his mouth.
All three of them swung to the entrance together and stalked through into the adjoining cavern. There was no sign of either Sparks or Morton. There was no response to Cliff's shouts. He turned quickly to the cradle and pointed to it in surprise. It was loaded with cases of titanite, but of the two men themselves there was no sign.
"Probably they're getting some more stuff, or else they—" Val shook himself. "What's the use?" he asked bitterly. "We've no time to look into it anyway. Let's get busy."
Between them they set about hauling the cases back into the cavern, stacked the long sticks of high powered explosive under the spot they had attacked with ray batteries. It took them an hour to make all the necessary fittings and connections, complete with fuses. The wire to the latter they paid out as they backed from the cavern. They took it with them to the elevator cradle and gradually unwound it from its drum as they rose upward to the higher levels once more.
Once they arrived there they solved the mystery of Sparks and Morton.
Both of them lay motionless, face down near the storage camps. They were dead, holes burned in their chests and faces.
- More photoelectrics hidden somewhere," Townshend muttered. "If we ever get out of this dump alive I'll be surprised."
HE made a final contact.
"Ready?" he asked, gripping the raised plunger rod.
Cliff caught his arm.
"Wait a minute! I just thought of something. Supposing we blow up the globe? What happens to all that stored potential energy? It won't travel to Earth—so, just where?"
"Can't you guess?" Townshend grinned almost ghoulishly.
"You mean," Val said, lighting his pipe, "that it will radiate to all parts of Mars and that we're sunk. . . ."
"Just that. Either us—or Earth. We can take our pick—maybe. Considering we had fifty men twelve hours or so ago and there are only three of us left now it doesn't take imagination to see where we go. Just the same, Cliff, you're the boss. Do I—?"
"Far as I'm concerned, ram in that plunger," Cliff replied grimly.
"Shoot!" Val thumbed down his pipe bowl, but his eyes watched the rod with a steady glitter.
Townshend rammed the plunger home. All three of them stood motionless and sweating as a titanic concussion blasted from the depths. The floor rocked under their feet; hot air came gushing up the chasm from the elevator shaft. The walls groaned and rocked under expanding forces and the floor ceased to be.
Cliff felt himself flung into space, went reeling through darkness with the shouts of Townshend and Val ringing in his ears. He landed with a force that
