Will looked at him unflinchingly.
"Watch the stairs," he said suddenly. "I've an idea." And the boy hurried back to the little parapet that overhung the trail that ran a thousand feet below.
Beyond and above him, the rim of the setting sun was coming nearer and nearer to the snow-capped mountains that cut the sky-line of the west. Already their white crests were gleaming crimson in the dimming light. As he went, Will fumbled in his belt and pulled out a tiny round pocket-mirror, which, with a tooth-brush, a comb, and a few other light articles, he had carried all through the trip in a rubber pocket fastened to his belt.
During these happenings, miles away, concealed by the intervening range, Hen and Joe were riding at the head of a troop of hard-bitten, hard-faced vaqueros, the cow-boys of the South, whom they had met at the end of their first day's journey. Armed with Mauser rifles, and with revolvers and knives in their belts, these riders of the pampas backed their wiry little South American horses with the same ease which their brethren of the Northern prairies showed.
The leader of the troop had turned out to be an old friend of Professor Ditson, who had been with him on an expedition years before. He readily agreed to journey with Joe and Hen over the mountains to the Lost City. The men had been rounding up half a dozen hardy, tiny burros, those diminutive donkeys which can carry their own weight of freight all day long up and down steep mountain trails. It was decided to take these along for the use of the travelers. With the obstinacy of their breed, however, there was never a time throughout the day when one or more and sometimes all of the burros were not balking at this long trip away from the ranch where food and rest were awaiting them. Accordingly, it was late in the afternoon when the party reached the range behind which was hidden Machu Pichu.
Suddenly Joe, who with Hen, mounted on spare horses, was piloting the little troop, caught sight of a flicker of light across the crest of the highest peak of the range ahead of them. At first he thought that it came from the rays of the setting sun reflected from a bit of polished quartz. Suddenly he noticed, with a sudden plunge of his heart, that the light was flickering in spaced, irregular intervals. With Will and several of the other boys of his patrol, Joe had won a merit badge for signaling in his Boy Scout troop, and his tenacious Indian mind had learned forever the Morse code. As he watched now he saw the sun-rays flash the fatal S O S. Again and again came the same flashes, carrying the same silent appeal, which he knew could come from none other than Will behind the range, heliographing with the last of the sun to the chum who had stood back of him in many a desperate pinch.
As Joe glanced at the setting sun he realized how short a time was left in which to save his friends. With an inarticulate cry, he turned to Hen, who was jogging lazily beside him, and in a few quick words told him what he had read in the sky. With a shout Hen gave the alarm to the troop behind in the rolling Spanish of the pampas, and in an instant, hobbling the burros, every man was spurring his horse desperately up the steep trail. With the very last rays of the disappearing sun the message changed, and the Indian boy sobbed in his throat as he read the words.
"Good-by, dear old Joe," flickered in the sky.
As the golden rim of the sun rolled beneath the horizon, Will strained his eyes desperately, hoping against hope to see a rescue-party appear against the trail which showed like a white thread against the mountain-side. Suddenly, in the dimming light, he saw a few black dots moving against the crest of the opposite mountain. They increased in number, and, once over the ridge, grew larger and larger until Will could plainly make out a far-away troop of riders and glimpse the rush of straining horses and the stress and hurry of grim-faced men. With a shout he leaned far out over the parapet until in the distance the drumming beat of galloping hoofs sounded loud and louder.
Ten minutes later a long line of men with rifles in their hands were hurrying up the steep path that led to Sacsahuaman.