With the wild cry of Fret Offut and the exultant yells of the bush-raiders ringing in his ears above the thunder of the rushing train, Jack North heard the ominous crash, of the descending bowlder, and saw with a dazed look its swift approach.

The locomotive, throbbing and panting like a human being in a race for life, was fairly flying along the winding track.

It all lasted but a moment, the downward rush of the deadly body, the cries of exultation and despair, the lightning-like passing of the fatal spot by the engine, and the ordeal was over as quickly as it had come!

The descent of the ponderous missile was swift and sure until a projection on the side of the cliff was reached, when with a terrific concussion the bowlder glanced. It suddenly shot outward like a cannon ball, and was carried fairly over the engine into the gulch below.

Jack witnessed this miraculous movement with breathless eagerness bordering upon terror.

The huge rock passed so near that it scraped the top of the caboose, and the current of air it raised swept the boy engineer's cap from his head.

The train had got its length beyond the place before Jack could realize that he had escaped.

The bush-raiders reminded him of it then, if he needed any further notification, by a volley of bullets and renewed yells of rage.

Though some of the leaden missiles flew uncomfortably near his head, Jack was unharmed, and as he was borne on by the iron horse around the next curve in the track, leaving his enemies out of sight, he offered a prayer of thankfulness for his providential escape.

Fret, he was certain, must have been killed by his mad leap from the engine. As much as he would have liked to have gone back and looked for the youth, he knew such a course would have been the height of folly. Besides his own life to look after, there were the passengers who had intrusted themselves to his care.

"Poor Fret! I could do no good now, and I must remember the others. If you had only remained on the engine it would have been better for you."

To his infinite relief, Jack saw nor heard nothing further of the baffled bush-raiders, who must have been greatly surprised at the escape of the train with its rich freight.

At the first station, which was several miles away from the scene of the outlaws' attack, the young engineer told of the loss of his fireman and his own narrow escape from death, when an armed squad of men started to search for the body of the missing youth, and to rout the bush-raiders if they could be found.

Finding an assistant at this place, Jack finished his run to de la Pama and then came back to this station, which was known as Resaca.

The relief party had not returned, but Jack was told that a bridge had been found to be unsafe for the passage of the train, so he could not reach St Resa that day, while it might be a week before the road would be in a condition to resume his regular trips. But he was willingly allowed to start after the relief party with the engine and one car, accompanied by a dozen armed men.

They were approaching the bridge mentioned, when they met the others coming back, bearing in their midst the lifeless form of Fret Offut.

Jack immediately stopped to have the body of his associate put on the car, when he started on the return to Resaca.

The untimely fate of Fret Offut impressed him with the great uncertainty of life. It was true the other had never been his friend, but now that was forgotten and he felt a deep regret over the youth's sad end.

The return to Resaca was made in safety. In fact nothing had been seen of the raiders since the start, and it was uncertain what might be their next move.

The following day Jack saw that Fret's body was given burial in a little plot within sight of the low-walled church of this clustered settlement, he being the only mourner.

"If I should fall in my hazardous work, I could not expect as much as poor Fret gets in this land of strangers. The last bond between this wild country and home seems to be broken. Little did we think of this, Fret, when we anticipated that South American trip!"

The last sad duty done for Fret Offut, and finding that the bridge would not be repaired inside of a week, Jack resolved to take a little outing on his own account.

He still carried with him the paper so strangely found on Robinson Crusoe island, and he was determined to make a search for the hidden treasure which it mentioned.

Accordingly, mounted on a small but sure-footed and faithful pony, with a supply of provisions, Jack set out on his uncertain journey without telling any one his intentions, little dreaming of the result which was to come of his secret movement.

He believed the mysterious island was nearly north of Resaca, so he shaped his course in that direction, keeping a sharp lookout for any enemy that might be in his pathway.

He was in the heart of the great dry region of South America, a district of nearly a thousand miles in length, where rain seldom if ever falls, and the country is afforded sufficient moisture by the sea vapors condensed on the Andes and sent down upon the plains and lowlands. The desert of Atacama lay many miles to the south, but as he progressed he often found sections of the country without a thing growing upon the land, though sometimes these spots were bordered by the most abundant growth he had ever seen, even in that realm of grand forests and magnificent flora.

Everywhere, save on these dark patches of waste land, the vegetation was on the boldest scale imaginable, the magnitude of the trees being simply beyond the comprehension of him who had never seen them, while some of even the largest were adorned with beautiful flowers, making them seem like gardens of themselves.

On account of the density of the growth, Jack often found it difficult to advance, and many times he was obliged to make long detours in order to reach a certain point.

Zig-zagging about, always keeping his eyes open for bush-raiders, wild beasts, and, above all, for the strange island, he had spent four days in the wilderness, when he felt that it was time for him to think of returning to civilization.

He had seen no sign of the looked-for body of inland water with its treasure island, though the increasing presence of cinchona trees told him that he was already ascending into the region of the Peruvian Andes.

"I am sure it is at the foot of these mountains that the strange island exists," he thought, as he paused on the summit of one of the foothills of the snow-crowned Monarch of Mountains. "But there is no sign of water, and how can I expect to find an island where there is no water?"

The involuntary speech brought a smile to his lips. As he would explain his thoughts, he said aloud:

"Somehow I got it into my head that there was a lake in this region, and there I was to find my treasure island. But I have been a fool to look for either. Come, Juan," patting the neck of his pony, "let us go back while we have sense enough to do so."

But while he spoke he lingered around the place, as if there was some strong fascination for him. It was a beautiful scene, made up almost entirely of forest, but such a forest as only Peru, with its wonderful natural wealth, can produce.

The trees were composed largely of rosewoods in all their varied beauty, the giant quassia in all their hues and tints of foliage, with a sprinkling of cinchona, lending a happy blending of more sober coloring, while from the lowlands was wafted to him on the gentle breeze of that tropical clime the perfume of the tinga.

The finger of silence lay on the lip of Nature, even the broad leaves of the quassia rising and falling on the shifting breaths of air, without that peculiar rustling sound generally belonging to the forest domain.

It was the most beautiful scene he had ever looked upon, and as he allowed his gaze to slowly move around the encircling country, he found himself looking down upon the strangest valley or mountain pocket he had ever beheld.

The singular feature of this isolated, wood-environed retreat was its complete absence of all kinds of growth, except for a sort of silky grass which covered its uneven surface like a rich carpet of the deepest green tint. Near the centre was an oval elevation of rock and earth higher by a few feet than knobs and miniature hills which dotted it elsewhere.

It was bare of vegetation, not even the silken tasia ornamenting its sides, though a solitary tree did rise in lonely grandeur from its utmost crest.

Jack uttered a low exclamation as he saw that this tree was a pimento.

In a moment his mind reverted to the description given in the strange manuscript, but a look of disappointment succeeded his eager anticipation.

"What a fool!" he exclaimed. "That tree stood on an island--"

A rustle in the undergrowth arrested his attention at that moment, and, before he could avoid the unexpected attack, a dark lissom body shot through the air, to alight squarely upon his pony, that, with a snort of terror, started madly through the growth.