Three slender towers, of a white metal that gleamed in the moonlight with the silvery luster of aluminum, rose from the rocky peak. They supported, in a horizontal position, an enormous metal ring. It must be, Dan reckoned swiftly, at least a hundred feet in diameter, and held a hundred feet above the summit of the mountain.
The huge ring gleamed with a strange purple radiance. A shimmering mist of red-violet light surrounded it. An unknown force seemed to throb within the mighty ring, drawing the mantle of purple haze about it.
And suspended inside the ring and below it was a long, slender needle of dazzling white light. To Dan, from where he stood in the canyon, it seemed a fine, sharp line, though he knew it must be some kind of pointer, luminous with the strange force pulsing through it.
The strange needle wavered a little, with quick, uncertain motions. The brilliance of its light varied oddly; it seemed to throb with a queer, irregular rhythm.
And the gleaming needle pointed straight at the planet Mars!
Dan stood a long time, watching the purple ring upon the silver towers, with the shining white needle hanging below it. He stared at Mars, glowing like a red and sinister eye above the incredible mechanism.
His mind was in a wild storm of wonder shot with fear. What was the meaning of the gleaming ring and needle? What connection did this great device have with the signal of distress from the cliff, and the green fire that had destroyed the Virginia? And why did the glowing needle point at Mars?
e did not know when he first began to hear the sound. For a time it was merely part of the strange mystery of the island, only another element in the atmosphere of fear and wonder that surrounded him. Then it rose a little, and he became suddenly sharply conscious of it as an additional menace. The sound was not loud, but deep and vibrant. A whir or hum, like that of a powerful, muffled motor, but deeper than the sound of any motor man has ever made. It came down the gorge, from the direction of the machine on the mountain.