For nearly two hundred yards they bored their way steadily into the mountain, their path gradually sloping downward. The walls and floor of the swift-forming tunnel were as smooth and hard as though glazed with a film of diamond.
Then abruptly Layroh shut the black ray projector off as the rock ahead of them ended and they broke through into another larger tunnel, dimly lighted by small globes of violet radiance set at intervals in the glassy ceiling. After thirty yards of travel along this tunnel they found their way barred by a massive door of copper-colored metal.
At Layroh's imperious gesture the men halted a dozen feet back of him in the tunnel while he brought something out of his leather belt-case. Foster was the only one of the group who was near enough to see that the object was a small tube closely resembling a pocket flashlight.
The only break in the surface of the great door was a six-inch disk over near its right-hand edge. Layroh slid this disk aside. Into the opening that was revealed he sent a series of flashes of colored light from the tube—two red, three green, and two blue. The colors were the combination to the light-activated mechanism of the lock. At the last of the blue flashes there was a whirring of hidden mechanism and the portal swung slowly and ponderously open.
Layroh beckoned to the men to follow him as he strode swiftly on into a vast room that was flooded with bluish light from scores of the radiant globes. As the men passed through the door it reached the limit of its opening swing and began automatically closing again behind them, but they were too completely engrossed in the scene before them to notice it.
They were in a great cavern whose glass-smooth floor was nearly a hundred yards square, and whose ceiling was so high that it was lost in the shadows above the maze of metal girders and cables that made a webwork some forty feet overhead. There was a feeling of almost incredible age about the place, as though it had been sealed away there in the heart of the mountain for countless centuries.
On every hand there was evidence that the cavern and all its contents were the products of a race of beings whose science was one that was utterly strange to that of the modern world. At the end of the room where they stood were row after row of different machines, great engines with bodies of dull silver metal and with stiltlike legs and jointed arms that made them look like giant metal insects. Foster could understand few of the details of the machines, but he felt that in efficiency and versatility they were far ahead of Earth's best modern efforts.
Grouped together in the center of the cavern were many assemblies of apparatus linked together by small cables that descended from main cables in the girder-crisscrossed ceiling overhead. There was a soft hissing of sparks leaping between terminals and a steady glow from oddly shaped tubes which indicated that the mechanisms were still functioning in silent and efficient performance of their unknown tasks.