"Yes, but where is he?" commented Frank. Then: "Leland! Leland!" he called.
His voice echoed through the huge vault and re-echoed hollowly. But there was no reply save renewed flickerings from the dome.
Leaving the vicinity of the gravity disc, the two men advanced in the direction of the shining dome, which was about a quarter-mile from where they stood. Both perspired freely, for the air was very close and the temperature high. But the light of the dome was as cold as the light of a firefly and they had no hesitancy in drawing near. It was a beautiful sight, this dome of silver with its flickering lights and perfect contour.
"By George, I believe it _is_ silver," exclaimed Frank, when they were within a few feet of the dome. "No other metal has that precise color. And look! There is a wheelbarrow and some mining tools. Leland has been cutting away some of the material."
Sure enough, there was indisputable evidence of the truth of his statement. And the material was undoubtedly silver!
"Silver Dome," breathed Tommy, holding a lump of the metal in his hand. "A solid dome of pure silver--fifty feet high and a hundred in diameter. How much does that figure in dollars and cents, Frank?"
"Maybe it isn't solid," said Frank dryly, "though it's worth a sizeable fortune even if it is hollow. And we haven't found Leland."
They circled the dome twice and looked into every corner of the great cavern, but there was no sign of the man for whom they searched. The wheelbarrow was half filled with lumps of the heavy metal, and maul and drill lay where they had been dropped by the lone miner. A cavity three feet across, and as many deep, appeared in the side of the dome to show that considerably more than one wheelbarrow load had been removed.
"Funny," grunted Tommy. "Seems almost like the old dome had swallowed him up."
At his words there came the terrific vibration. The light of the dome died out, leaving them in utter darkness, and from its interior there rose the mounting scream that had frightened old Thomas away. From so close by it was hideous, devastating; and the two men clung to each other in fright, expecting momentarily that the earth would give way beneath their feet and precipitate them into some terrible depth from which there could be no return.