Hardly had the rumble of the falling bridge passed when Jud slipped his arm about Will's shoulders and half-led half-dragged the fainting boy around the corner of a great rock.
"Those yellin' devils shoot too straight for us to take any chances," he remarked briefly.
The same idea had come to the rest of the party, and they followed hard on the old trapper's heels. Here Professor Ditson again took the lead.
"It'll take them some time to get across that river, now the bridge is down, if they follow us," he observed with much satisfaction. "We ought to reach Machu Pichu to-day and Yuca Valley in two days more. There we'll be safe."
"What's Machu Pichu, Chief?" questioned Jud, using this title of respect for the first time; for the professor's behavior at the bridge had made an abiding impression on the old man's mind. "It was the first city that the people of the Incas built," explained Professor Ditson.
"When the Inca clan first led their followers into these mountain valleys, they were attacked by the forest-dwellers and driven back into the mountains. There they built an impregnable city called Machu Pichu. From there they spread out until they ruled half the continent. Only the forests and the wild tribes that infested them they never conquered. At the height of the Inca Empire," went on the scientist, "Machu Pichu became a sacred city inhabited mostly by the priests. After the Spanish Conquest it was lost for centuries to white men until I discovered it a few years ago."
"Where do we go from Yuca?" questioned Jud again.
"Follow the map to Eldorado," returned the Professor, striding along the path like an ostrich.
Beyond the rock, and out of sight of the cañon, gaped the mouth of a tunnel fully three hundred yards in length. Narrow slits had been chiseled through the face of the precipice for light and air, and although cut out of the living rock with only tools of hardened bronze by the subjects or captives of forgotten Incas, it ran as straight and true as the tunnels of to-day drilled by modern machinery under the supervision of skilled engineers. Through the slits the adventurers caught glimpses of the towering peak down which they had come, but there was no sign of their pursuers. In a moment they had vanished from the naked rock-face against which they had swarmed.
Joe stared long through one of the window-slits, while below sounded the hoarse, sullen voice of the hidden river.