They finally compromised on Sacsahuaman, whose thick walls were slit here and there by narrow peep-holes and whose only entrance was by a narrow staircase of rock cut out of the cliff and guarded, like most of the entrance staircases, by rows of heavy boulders arranged along the ledge. Inside were long benches of solid stone, and, best of all, at the base of a white rock in the center of the tower trickled an ice-cold spring whose water ran through a little trough in the rock as it had run for a thousand years. Professor Ditson told them that in the old days it had always been kept guarded and munitioned as a fortress where the Incas could make a last stand if by any chance the rest of the city should ever fall into the hands of their enemies.
That night they kindled a fire within the tower, and ate their supper high above the sacred city on the battlements where the guards of the Incas had feasted a thousand years before Columbus discovered the New World. Afterward they slept, taking turns in guarding the two entrances to the city from the same watch-towers where other sentries had watched in the days of the beginning of the Inca Empire.
The next morning Will could not move. The stress and strain and exertion of the day before had left him too weak to throw off the numbing effect of the virus. Professor Ditson shook his head as he looked him over carefully.
"There is only one thing to do," he said at last. "We must send on ahead and get a horse or a burro for him. He has walked too much as it is. Any more such strain might leave him paralyzed for life. Hen," he went on, "you know the trail to Yuca. Take Joe and start at once. You ought to run across a band of vaqueros herding cattle long before you get to the valley. Bring the whole troop back with you. I'll pay them, well, and they can convoy us in case the Miranhas are still after us."
A few minutes later Hen and Joe were on their way. Leaning over the parapet of Sacsahuaman, the rest of the party watched them wind their way slowly down the precipice until they disappeared along the trail that stretched away through the depths of the cañon. All the rest of that day Jud and Pinto and the professor took turns in standing guard over the two entrances to the city, and in rubbing Will's legs and giving him alternate baths of hot and cold water, the recognized treatment for stings of the maribundi wasp.
That night it was Jud's turn to guard the staircase up which the party had come. Once, just before daybreak, he thought he heard far below him the rattle and clink of rolling stones. He strained his eyes through the dark, but could see nothing, nor did he hear any further sounds. In order, however, to discourage any night prowlers, the old trapper dropped one of the round boulders that had been placed in the watch-tower for just such a purpose, and it went rolling and crashing down the path.
Daylight showed the trail stretching away below him apparently empty and untrodden since they had used it when entering the city. Tired of waiting for Professor Ditson, Jud hurried up the steep slope to the fortress, meeting the scientist on the way to relieve him. The old trapper was just congratulating Will on being well enough to stand on his feet when a shout for help brought all three with a rush to the entrance of the tower. Up the steep slope they saw Professor Ditson running like a race-horse, while behind him showed the giant figure of Dawson, followed closely by half a hundred Miranhas. In another minute Professor Ditson was among them.
"They must have hidden during the night around a bend in the path and rushed up when we changed guards," he panted. "They were swarming into the tower just as I got there."
All further talk was stopped by the same dreadful tumult of war-cries that the travelers had learned to know so well.
"Steady, boys," said Jud, instantly taking command, as a veteran of many Indian fights. "Four against fifty is big odds, but we've got a strong position. Will, you sit by the staircase an' if any one starts to come up, roll one of them fifty-pound boulders down on him, with my compliments. I'll stay back here where I can watch the whole wall an' pick off any one that tries to climb up. Professor, you an' Pinto keep back of me, with your ax an' knife handy in case any of them get past me. Now," he went on, as the three took their stations, "how about some breakfast?"