CHAPTER XVIII.

THE TREASURE OF THE MISSION.

The effect of their first sudden immersion into the total blackness of the tunnel was paralyzing to Ralph, the professor, and Walt Phelps. The air, too, was still oppressive and musty with the accumulation of ages.

"Has any one got a match?" was the professor's first inquiry.

"Don't know," rejoined Walt Phelps, "I most generally have, but them greasers went through me pretty thoroughly. Hold on, though; wait! Hooray! I had a hole in my pocket, and some slipped through into the lining of my coat."

"Light up," said Ralph eagerly, "and let's see what sort of a horrible hole we are in."

A sputter, a crackle, and then a blessed flood of light, as Walt Phelps lit one of the precious matches of which he had found three or four.

"Now, see how much you can take in in one match-length," urged the red-headed ranch boy, as he held the match high in the air.

Its radiance showed them that they were in a narrow, walled tunnel, into which the steps from the trap-door above had led them. Right ahead stretched blackness, behind was blackness, only in the little illuminated circle in which they stood in fact, was there any relief from the gloom. The professor uttered a sudden gleeful exclamation, and at the same instant Walt dropped the match with a loud exclamation of:

"Ouch!"

He had held on to it so long he had burned his fingers.

"Never mind," consoled the professor; "that match, Walter, has shown us one important thing."

"And what is that?" asked Ralph.

"That there is an opening to this passage somewhere."

"Why, how----"

"Simple enough. The flame flickered, as Walter held the match up. That shows there must be a draught, and where there is a draught there must be an opening."

"Then, for goodness sake, let's make for it," exclaimed Ralph, stumbling forward in the darkness "I can't stand this blackness much longer."

With his hands spread in front of him the boy started off, the others following. Walter would have lighted another match, but this the professor vetoed. He argued that, not knowing what lay ahead of them, they had better reserve their store for a real emergency. The boys agreed to this readily.

They had gone about two hundred yards when Ralph, whose hands were feeling along the walls as he went, gave a sudden exclamation. Up to this point the passage had been about six feet in height, and four or more in width. Now, however, it contracted until they had to double up, and could only just squeeze through. It grew unendurably hot, too, and as the floor had steadily declined as they went, they argued that they must have reached a considerable depth.

Ralph's exclamation had been caused by a peculiar substance with which his fingers had suddenly come in contact. Heretofore the walls had been rough, and in places rocky. Suddenly, however, his fingers encountered a rounded, smooth surface.

"What's the matter?" asked the professor, who was behind.

"I don't know. There's something odd imbedded in the wall right here. Can we spare a match?"

"I think under the circumstances we might," said the professor.

Walter accordingly kindled a fresh lucifer.

As its rays shone out, every one of the party shrank back with a cry of horror.

From the wall a grinning skull was gazing at them.

The ranch boy dropped his match with a cry of terror and startled alarm. Even the professor's nerves were shaken by this sudden apparition.

"F-f-for g-g-goodness' sake, strike another!" stuttered Ralph.

With trembling hands Walt struck another light, and this time they nerved themselves to examine the wall more carefully. The skull was imbedded in the rock, and by its side they now perceived was a skeleton hand, pointing down the tunnel. The professor also noted some marks at its side. There were five of them--short, straight lines, scratched in the wall.

"Why, boys," he said, as the match died out, "there is nothing to be alarmed at. The skull is placed there as some sort of a pointer, or indicator, as I take it. That hand shows the direction in which the treasure lies, and the five scratches mean either five feet, or five yards, in this direction."

This simple explanation nerved the boys wonderfully, and they carefully paced off five feet.

"Another match, Walter," ordered the professor.

"The last but one," said the boy, as he struck it.

Hastily they gazed about them, but not a sign could they perceive of any break in the wall or floor, which might serve as a hiding-place for the treasure indicated in the miner's invisible writing.

"Shall we try at five yards?" asked Ralph.

"We will put it to a popular vote," rejoined the professor. "It will mean burning up our last match, but on the other hand----"

"I'm willing to use it--how about you, Walt?" came from Ralph.

"Sure," responded the ranch boy.

The professor made rapid mental calculations, and then paced off the additional distance necessary to make up the five yards from the original starting-place.

"Now," he said, coming to a halt.

How carefully Walt Phelps nursed that tiny yellow flame, as it burst into being. How eagerly they glanced about them, greedy of every morsel of its light.

Suddenly the professor gave a cry.

"Look!" he sputtered out.

He was pointing downward excitedly. Almost at his feet was a mildewed iron ring. As the light died out, he grasped it.

"Never mind the darkness, now; I've got it!" he cried exultingly.

"Pull it up," urged Ralph, all else forgotten in the mystic spell of hidden treasure.

"Yes, pull," urged Walt.

"I--ugh--ugh!" grunted the professor, putting all his strength into it, but the ring never budged an inch.

"Here, give me a hand, boys!" he cried.

"How are we to find you?" asked Ralph.

"Here, extend your hands. Ah, that's it," went on the scientist, seizing hold of the boys' wrists and guiding them down to the ring.

"Now, all together," he said; "pull!"

With all their strength the three adventurers tugged with a mighty heave at the iron. At first it seemed that it was going to prove obdurate even to their combined efforts, but continued tugging resulted in a slight quiver of whatever the iron ring was fastened to.

"Now, once more--he-a-ve!"

There was a sudden give on the part of the iron ring, and its foundation gave way with a rush.

A strange, pungent odor filled the air!

"I--I--I'm choking," gasped Walt, gripping his collar with both hands and tearing it open, to relieve the terrible congestion that had suddenly seized upon his throat.

"Run, boys; run for your lives!" shouted the professor. "There's something deadly in there!"

They needed no second invitation. Forward they plunged, gasping and choking, in the grip of the unseen, destructive agent they had liberated.

The professor, as he sprang forward, felt his foot slip, and realized that he was falling backward. As he fell into what he knew must be the pit they had opened, and from which the noxious fumes were pouring, he grasped at something--it was Walt's leg.

"Hey, leggo my leg!" howled the red-headed youth, half-crazy with fear. To his excited imagination, it seemed that in the darkness some pulling arm had reached up from the pit and seized him.

"Walt! Walt!" gasped the professor. "Save me!"

The boy, in agony as he was from the horrible gases, pluckily reached round and felt about. Presently he felt the professor's bony hand grip his. A second later, the scientist had been hauled out of danger. But the suffocating fumes still filled the passage. They were choking, blinding and killing the adventurers.

"Forward, forward! It's our only chance!" cried the professor.

Suddenly he felt Walt, who was just ahead of him in the panic-stricken flight, collapse. Seizing the fainting boy in his arms, the professor bravely struggled on. In the meantime Ralph had hastened on ahead, and knew nothing of what had occurred behind him.

Rapidly he ran from the unseen peril, covering the ground swiftly. Stumbling blindly forward, he all at once felt the air grow fresh and sweet, and at the same time a sort of glow penetrated the stygian darkness of the tunnel.

The boy glanced upward and gave a cry of delight. Above him, at the mouth of a circular shaft, he saw the kindly stars blinking. Never had the sight of the sky looked so sweet to him. But even as he was congratulating himself, he looked about for his companions.

They were not there!

"Hullo, Walt--professor! Hurry," he called back into the blackness and the foul danger he had left behind him.

To his dismay, his voice echoed hollowly upon the rocks, and went booming mysteriously down the tunnel. But human reply to his call, there was none.

With a sinking heart, Ralph realized in an instant what had happened. The professor and his companion had been overcome, by whatever it was that had emanated from the trapdoor in the tunnel.

A sort of panic seized on the boy.

He shouted and shouted, again and again, regardless of his voice being heard above. But only the mockery of the echo to his frightened cries came back to him.

It is no disparagement to Ralph to say that it required some effort on his part to nerve himself for what he did then. Summoning every ounce of resolution in his body, he threw himself on his hands and knees, with a vague recollection of having heard somewhere, that deadly gases were less deadly near to the ground.

Thus extended, the Eastern boy, with a beating heart and a dread sense of disaster oppressing him, crawled back into the danger-filled darkness from which he had just emerged.

As he proceeded, the air grew more and more unbearable. His skin seemed to be on fire, and his eyes were filled with an aching, burning, smart that was maddening. But the boy kept repeating over and over to himself the words he had uttered as he plunged back over the path of danger.

"I must get them out. I must get them out!"

In the pitchy darkness, with mind and body burning, he painfully wriggled on.

"I can't keep this up much longer," was his thought; "where are they, oh, where are they?"

Suddenly he bumped into something soft. It was a human body.

"Professor!" gasped the boy in a voice which he knew must be his own, but which sounded strangely like that of another person.

A faint groan answered him.

"You must come with me. I must get you out. I must get you out," gasped Ralph. He seized the other's clothes and made a brave effort to drag him forward. But as he did so, everything seemed to race round and round in his head in a mad whirligig, and the boy collapsed in a senseless heap beside the two he had come to save.