Presently he became conscious of torturing thirst. He retired through the brush, along the rocky wall of the canyon. By sunset he came upon a little natural basin in a rock, half full of rain water. It was none too clean, but he drank his fill of it, and felt relief. Looking up the canyon, he could see the great mechanism on the peak, gleaming in the dusk. Intensely-glowing purple mist clung about the great metal ring, and the slender, delicate needle swung below it, still vibrating, still throbbing with brilliant, white radiance. It pointed at the red eye of Mars, which had just winked into view. Dan stared at it a long time. "It all sounds crazy," he muttered, "but it isn't! The Master Intelligence of Mars, she said, is controlling the mechanical things through that! The doom of the Earth is coming through that white needle! If only I could smash it, somehow!" He looked down at the white folds of the sheet that draped him, and clenched his hands impotently. "No gun! Not even a pocket-knife. Nothing but my bare hands!" He bit his lip. * * * * * Still he stared challengingly at the gleaming mechanism on the peak. An idea slowly took form in his mind; an exclamation abruptly escaped him. Narrowly he eyed the trussed girders of the silver towers which supported the great ring, muttering to himself. "Yes, I can do it! If I don't get caught! I can climb it, well enough. The needle looks a bit frail. I should be able to smash it! I'd like to see Helen again, though." He gathered the sheet around him, and began picking a cautious way up the canyon, staying always in the cover of boulders or brush. A few times he disturbed a rock, or snapped a twig beneath his foot. Then he waited out of sight for long minutes, though he had no reason to believe that the metal monsters were on the alert for him. "I've got to do it! The world depends on it!" he kept saying again and again in his mind. The quick darkness of the tropics had fallen almost before he started. But he welcomed the night, for, if it made his own silent progress more difficult, it reduced the hazard that he would be discovered. Gauging the time by the slow wheeling of the diamond-like stars across the velvet sky, he thought that two hours had passed when he reached the head of the canyon. He stood up cautiously to survey the little plateau at the summit of the hill. It was several acres in extent, quite level, and almost clear of vegetation. At the farther side was a pile of wreckage, which, he supposed, had been the quarters of Dr. Hunter's party, before they had been destroyed. Many huge machines stood about the plateau, vast, dark masses looming in the starlight. Mostly they were either not running or very silent in operation; but a very deep, vibrant humming sound came from one near him. Smaller shapes were moving about them, with long easy leaps. These, he knew, were the mechanical monsters, though it was too dark to distinguish them.