Harvey was called at two o’clock in the morning, and he posted himself as sentinel under a small tree that grew near the shelter-tent. He had become somewhat accustomed to being rudely awakened and to being alone while the others slept, and now that an attack by Indians was improbable, and it was no longer necessary to strain his sense of hearing that he might note the slightest sound, the novelty of the situation appealed to him.

This night the moon in its third quarter shone from out a cloudless sky, and at the altitude of the great intermontane valley in which they rested, the rays were brighter than at points nearer the sea level, so the river bank and the open country were visible with nearly the distinctness of day.

As the boy walked a few times back and forth, a rifle on his shoulder, then paused for a short rest under the tree, he puzzled his brain to account for their not having found the second white rock. He believed implicitly in the truth of all that Huayno had said, and was confident that not far from where he stood great riches were stored in the ground.

But could they ever locate the mine? It would be a task of years to demolish all those mounds and ascertain which hid the entrance to the old workings; and should it be attempted, others must learn what they were doing on the banks of the MaraÑon, others would flock to the place with picks and shovels, and among these others some one or two might first find the store of yellow metal.

Thus cogitating he walked closer to the river and stood beneath the great white rock, which shone resplendent in the moonlight, glistening and seeming to be translucent. Studying the strange geological formation attentively, he noticed for the first time that only the side facing up stream and the side facing the woods were white; those facing down stream and the opposite shore were much darker, almost a slate color. This peculiarity had not been remarked, because no member of the party had gone farther down stream. The boy also saw that the rock was several feet from the river and that its lower portion, where the water washed, had turned this same slate color.

He paced slowly back to the tree, meditating on these observations, and endeavoring to solve the reason for the varying of the physical features of the unique landmark. In the midst of this his mind strangely reverted to the time of a dinner party that had been given at his father’s home in Chucuito about six months before, and try as he might he could think of nothing else than this entertainment and the people who were present; then of the conversation that had occurred—and the moment the mind cell that contained the impression left by that conversation opened, he had the solution of the problem which confronted them.

At this dinner Don Isaac Lawton, editor of the South Pacific Times, had been asked to explain the absence of rain on the Peruvian coast-line. He had done so in these words:—

“The absence of rain on the coast is caused by the action of the lofty uplands of the Andes on the trade-wind. The southeast trade-wind blows obliquely across the Atlantic Ocean until it reaches Brazil. By this time it is heavily laden with vapor, which it continues to bear along across the continent, depositing it and supplying the sources of the Amazon and the La Plata. Finally, the trade-wind arrives at the snow-capped Andes, and here the last particle of moisture is wrung from it that the very low temperature can extract. Coming to the summit of that range, it rushes down as a cool and dry wind on the Pacific slopes below. Meeting with no evaporating surface, and with no temperature colder than that to which it is subjected on the mountain tops, this wind joins the south trades and reaches the ocean before it becomes charged with fresh moisture.”

Harvey, recalling this conversation, for it had been imprinted upon his mind, because it was the first explanation he had heard of this Pacific coast phenomenon, began to reason that if the trade-winds blew in a certain direction over Brazil and in a certain direction on the coast, there was undoubtedly a regularity of the wind currents in this intermontane valley. He had noticed since leaving Huari that what breeze stirred, blew in their faces; therefore the general direction of the wind was up stream, or toward the southwest.

That being true, the reason why a portion of the great white rock had turned a slate color was evident—it was weather-stained, and the remaining portion, sheltered from the winds, retained its lustre. At this stage in his reflections he recalled a sentence from his geology: “Alabaster is soluble to a certain extent in water.”

This white rock was high above the river and had not been dissolved by the stream. Its northern portion had undoubtedly been worn by rains, and it was probably not so high as when old Huayno was a young man; still it had been better preserved than if the full force of the stream had been brought to bear upon it.

“What if conditions had been different and the rock had been wave-washed all these years?” Harvey asked, and then answered himself: “It would have been worn down and all sides would have been weather-stained, even as the more exposed portions are.”

In the region of the peculiar mounds they had noticed a depression, and all had agreed that it probably formed the course of a stream during the rainy season. Perhaps the second white rock had stood in this depression; it was undoubtedly not so high as that which was nearer the river, even in old Huayno’s day. What then would have been the natural result of a low rock of alabaster, washed five and six months in the year by swiftly running waters?

Again he answered himself, to the effect that under such circumstances a rock of this description would have been worn down in the eighty years, perhaps almost to a level with the country, and its entire surface would be slate-colored, like the weather-beaten sides of the landmark on the MaraÑon.

Five minutes later Harvey entered the shelter-tent and awakened Ferguson.

“My turn to stand guard, eh?” said the elder American, as he threw off the blankets and commenced putting on his clothing.

The boy made no answer until he was joined on the outside by the young man; then he said:—

“No, it isn’t your turn, and it won’t be for an hour, but I would like to go into the woods for a little while and don’t wish to leave the camp unguarded.”

“Go into the woods! Are you crazy, lad? Has the moon affected you?”

“I have an idea that I can find the second rock.”

“You have, have you?”

“Yes.” And then he explained his chain of reasoning.

“Now I call that clever,” said Ferguson, “and I believe you have hit the nail on the head. Don’t you want somebody to go with you?”

“No. There’s no danger. I shall carry my shot-gun. Besides, the camp must be guarded, and I don’t want to awaken the other two.”

“Why not?”

“They’ve had their watch; and besides, if I fail, there won’t be so many persons disappointed.”

“Sensible precaution, that.”

“I wish I had Mr. Hope-Jones’s compass.”

“Here it is. He gave it to me in the woods because his pocket is torn.”

“Let me have it, please. Mr. Ferguson, 5280 feet make a mile, do they not?”

“Yes.”

“And one-half of 5280 is 2640?”

“Certainly.”

“I cover about two feet at every step through this broken country, do I not?”

“About that. But what are you driving at? You are the greatest boy to fire questions at one that I ever met.”

“Why, I want to go in the direction old Huayno gave for exactly a half mile, or as near that as possible, and then investigate.”

“Well, take care of yourself, and if anything happens fire a shot and I will hurry to your aid.”

“Good-by.”

“Good luck.”

And the boy disappeared in the timber. “One, two, three, four, five, six, seven, eight, nine, ten,” Harvey counted, and then into the twenties and into the hundreds, thus numbering the steps as he took them in a north direction, guided by the compass needle. He soon lost sight of the camp and of the white rock and was well in the region of the tall trees. He had carried only his shot-gun, the little iron hammer, and the compass. The early morning was cool, the air bracing, and as the moon’s rays gave plenty of light, he made quick progress; but from the start he so regulated his steps that they would not be much over two feet each in length. Whatever addition there might be to that measure he thought would in the total correspond with old Huayno’s idea of a half mile, for the Indian’s estimate had invariably been less than the actual distance.

He had counted one thousand before he stopped to rest; and then the halt was but momentary, more to tighten his belt and shift his shot-gun from one shoulder to the other, than because he was tired. Soon after starting again, he noticed to his satisfaction that he had entered the slight depression which they had observed in the afternoon, and through which it was believed a river ran during the rainy season. Its course there was north to south, where it entered the MaraÑon. Thus the strength of one link in his theoretical chain had been proven; if the second white rock was directly north from the main river, it undoubtedly stood in the bed of this periodical waterway.

About this time he entered the region of the curious mounds and was able to remain in the little valley, for the waters had washed a way around each, not so deep as the channel, however, proving that a portion of the flow had soaked through the strangely formed hillocks.

At his two-thousandth step the boy noticed that the mounds had increased in size and were closer together. A hundred yards farther they appeared to be merged into one, which was several hundred feet in circumference, and which appeared to be a little table-land, indented by the depression across its surface. At the opposite end from where he had entered the table-land, or rather on the opposite side of the circle, the river-bed swept in an angle to the east.

Perspiration stood in beads on his forehead; his heart beat wildly. Was he right? Was this little table-land, this mound larger than all the others, an elevation at the mouth of the mine? Was the decomposed wood under his feet the remains of trees which had been felled in the greatest number by the Ayulis, because of proximity to the treasure? If these facts were true, then where had the white rock stood? Why, at the point where the river of winter changed its course to the east; that was the most probable point, if the pillar that marked the mine opening bore north from the MaraÑon, as old Huayno had said.

It took him but a minute to reach this point, and once there he put down his rifle, then commenced to crawl on all fours over the little hillocks with which the big mound was dotted, striking the ground hard blows with his hammer. After having done this for a quarter of an hour or so he stopped, for he was almost out of breath, then when rested he moved to the other side of the depression, at a point a few yards beyond, where it turned east at right angles. There his foot encountered something hard, and throwing himself down, he commenced feverishly to tear aside the vines and creepers that formed a covering. When they were removed he saw a dark brown rock that was covered over with decayed vegetable matter. Scraping this off, the lad made use of his little hammer, and after three or four blows a wonderful thing happened.

As the dirty brown shells of an oyster open and reveal an interior of pearly white, so the breaking of the rock showed a seam that was the color of milk.

Ferguson, standing guard near the MaraÑon, was wondering what kept Harvey so long and was blaming himself for permitting the lad to enter the woods unaccompanied at such an hour, when his attention was attracted by the crackling of underbrush some distance away, and then the sound of footfalls nearing him rapidly.

“Harvey’s on the run!” he ejaculated. “Wonder if it’s a puma this time, or what?” and swinging his rifle on his shoulder, he started at a double quick to the forest, where he met the boy, hatless and minus his shot-gun, just beyond the first line of trees.

He had no opportunity to make inquiries, for the lad waved a piece of rock the instant he caught sight of him and screamed:—

“I’ve found it! I’ve found it! Look at this! will you?”

It happened that the shelter-tent had not been erected in a very secure manner the evening before, for all hands had been too tired and discouraged; they had used a very thin piece of wood for a centre-pole. Therefore the result of a wild rush under the canvas by Ferguson and Harvey, both anxious to tell the cheering news, was the collapse of the cloth structure, and in the entangling folds three men and a boy were soon struggling. To add to the confusion, Hope-Jones, who had been dreaming of the Majeronas, imagined an attack was on, and reaching out for the fancied opponent nearest him, he commenced pommelling Ferguson lustily. The elder American, who was so imprisoned by the canvas that he could not defend himself, might have been seriously injured had not SeÑor Cisneros rolled himself free, and dragged the bellicose Englishman away. He then freed the others, and as Harvey was still breathing heavily, after the wild dash through the woods, he drew the boy to him, believing he had been injured.

“No, I’m not hurt,” exclaimed the lad, panting. “Look, I have found the white rock over there in the woods! Here’s a piece that I chipped off,” and he exhibited the specimen of alabaster, to which he had held firmly.

Hope-Jones, who by this time had come to his senses, gave a yell of joy, and the captain, jumping to his feet, caught Harvey by the shoulders in an embrace, then urged him to relate the details of his exploration.

Of course there was no thought of attempting to sleep again that night; they did not even straighten up the shelter-tent. Hope-Jones and Ferguson favored starting at once in search of the treasure, but the captain said it would be wiser first to eat breakfast. “Besides,” he added, “Harvey needs some rest.”

So they built a fire and soon were enjoying tin cups of hot coffee and some broiled duck’s meat—for the captain had snared wild fowl the evening before and had prepared it while on watch.

Although the moon was setting when the start was made from the camp, they pushed on quickly, for their watches told them that in another half hour dawn would come; and when at last they reached the large centre mound and the point where Harvey had found the second white rock, a gray light was penetrating the woods.

Three happy men, and a boy who was even happier, sat around the camp-fire on the banks of the river MaraÑon that evening.

“You say the quartz is the richest you ever saw?” asked Harvey.

“Yes, it is,” and the captain lifted one of the many pieces they had brought from the mine as samples, and all looked at it for perhaps the hundredth time that day.

“How long do you think we had better remain here?” Ferguson inquired.

“Perhaps a fortnight. That will give us ample time in which to explore the property and stake it off.”

Another member of the camp was a friendly Ayuli Indian, who had appeared on the bank as they emerged from the wood. He with others had been driven far from his village by the marauding band of Majeronas before the latter’s encounter with the white men, and he was making a long detour on his return. They had detained him over night and on the morrow intended sending him with letters to Huari, from where they would be forwarded to Chicla and then to Callao.