[Ill.u.s.tration: As it flared up, they all three recoiled with expressions of dismay. At their very feet was a deep chasm.]
The place was a charnel house!
No mystery now as to what had become of the human remains of the grisly sacrifices of the ancient mesa dwellers. There, piled in that dark chasm beneath them, were great piles of decaying bones and gleaming skulls. Hundreds of them extended toward the surface in a ghastly pyramid. No wonder the underground place into which they had penetrated smelled musty and unpleasant.
"It is the mesa dwellers" burial ground!" exclaimed Ralph in a quavering voice, as, clinging to Jack"s arm, he bent forward.
"Yes," rejoined Walt with a shudder, "and but for Providence, we should have plunged downward into it ourselves."
"Ugh!" exclaimed Jack, in a voice filled with repulsion. "Don"t let"s think of it. See, the path takes a turn here. Come on, let"s go ahead, but follow me closely and keep in to the wall."
"Not likely to take any chances of missing the road, after seeing that," spoke up Walt, as once more the three youths, who had been so strangely plunged into this predicament, began to tread the subterranean regions once more.
As you may imagine, they went with due caution. But no more dangers menaced them, and as they progressed the path began to widen. All the time, however, the strange roaring sound had been growing louder, until now it had attained almost deafening proportions. Still they had come upon no explanation of what it could be. Jack had privately concluded it to be the sound of the wind, forcing its way into some crevice.
This theory seemed to be the more tenable as the last match which he had struck had only been kept alight with difficulty, so strong had been the draught that now puffed up toward them.
Far from alarming them, however, this gave them renewed hope. It meant that, in all probability, they were nearing an outlet of the strange underground place. Had it not been for the predicament in which they had left the professor and Coyote Pete, the three lads would have felt a real interest in exploring the cavern, now that they had grown accustomed to their surroundings. So far as they had been able to make out, the tunnel they had been treading was partially the work of human hands and partially the work of Nature. The great rift in which lay the acc.u.mulation of human remains was evidently the result of some volcanic upheaval. The path, however, was so graded and formed that there seemed no reason to doubt that it had, at one time, been made by the ancient mesa dwellers.
"Seems to me we ought to find out what that roaring sound means before we go any farther," suggested Ralph suddenly.
"That"s a fine Irish bull," laughed Jack. "How are we going to find what it is unless we do go farther?"
"That"s so," agreed Ralph, somewhat abashed. "Come on, then."
A few paces more brought them to an abrupt turn in the path, as they could feel by their constant touching of the inner wall.
"Better strike another match," said Walt.
"Yes; here goes," agreed Jack. Both boys shouted, to make themselves heard above the now thunderous roaring of the strange noise.
A shout of surprise that rose even above the mysterious roaring, followed the striking of the match. Beyond the turn the path took a steep drop downward, and beyond that--the boys could hardly believe their eyes as they gazed--was the glint of rushing water.
"The subterranean river!" was the amazed cry that broke from the lips of all three.
CHAPTER X.
A NEW MEXICAN STYX.
"The subterranean river!"
The words echoed back weirdly from the vault-like chamber into which they had now penetrated, and at the bottom of which the stream, upon which the light of the match had glistened, flowed rapidly. Within this s.p.a.cious place the noise was not nearly so loud as it had been when confined in the narrow tunnel, which, in fact, acted much as a speaking-tube would have done.
"It can"t be!" gasped Ralph, unwilling to believe his own eyes.
"But it is," cried Jack, as, all thoughts of their predicament forgotten in this strange discovery, they made lavish use of their matches on gaining the edge of the stream. The river was about twenty feet in width, and they speedily saw that the roaring sound they had heard during their progress through the tunnel was produced by a waterfall some distance above, over which the river plunged into a sort of basin at their feet.
But this was not the most astonishing thing they found in that first brief but comprehensive inspection. Affixed to the rocky wall at one side of the chamber was a large, bronze lamp. An eager overhauling of the utensil showed it to be filled with oil, and apparently it was not so very long since it had been lighted.
Hastily applying a match, Jack soon had the rocky chamber lighted, and they could now survey the place into which they had blundered, at their ease. In size it was about the same dimensions as the Council Hall of the mesa, which lay, they knew not how many feet, above them. The river roared down along one side of it, forming a deep, turbid pool just beneath the waterfall, by which it entered the place.
To their astonishment, the boys now spied in one corner of the chamber several empty boxes piled up. Remains of excelsior and sacking were within them, and they bore the stencilled marks, "Agricultural Machinery, With Care."
Instantly what Pete had related to him concerning the conversation of the men accompanying Black Ramon flashed into Jack"s mind. Could it be possible that they had stumbled upon the place utilized by the gun-runners to convey their ammunition across the border? At this instant, there came a shout from Ralph, who had been peering about the place.
"A boat!"
"A what?" The incredulous cry burst from both Jack and Walt.
"It is a kind of a boat, anyhow. Come here, and look for yourselves."
Ralph was bending over the rocky marge of the subterranean river at a part of the chamber farthest removed from the waterfall. The water here flowed comparatively slowly, most of its force having been expended in the pool beneath the fall. Sure enough, Ralph had been right. Moored to the bank by two stout ropes attached to iron bars driven into the rock, was a boat--if such a name can be given to the flat-bottomed, floating appliance, upon which the thunderstruck boys gazed.
The boat, or rather float, was about twenty feet in length and some five feet in beam. It was not unlike, in fact, one of those shallow craft used by duck hunters, only it was square at each end. Evidently it would hold a considerable quant.i.ty of freight. More excelsior and burlap litter in the bottom of it showed that whatever had been the contents of the boxes, it had apparently been used to transport them.
"Boys, we"ve tumbled over the discovery of the age!" exclaimed Jack, in what was for him, a strangely excited voice.
The others were not less moved. Their eyes were round and their jaws dropped in incredulous wonderment, as they gazed before them.
"Will somebody please pinch me?"
It was Ralph who spoke, turning a countenance solemn and startled upon his comrades.
"No need to do that, Ralph. You"re wide-awake; make no mistake about that."
"But--but I don"t understand," began Walt in a puzzled tone. "What is this place, what----"
"What is it?" echoed Jack. "It"s the gun-runners" underground railroad. Can"t you see it? This river, so the old Indian legend says, emerges across the border. In some way these Mexicans heard of it, and learned the secret of the hollow altar. No wonder the government has not been able to find out how the rebels got their arms across the border."
"Well, what are we going to do, now we"ve found it?"
Walt, the practical, propounded the query, as they stood there, half-stunned by the rapidity with which unheard-of events had happened within the last half-hour.
"Why, I--upon my word, I don"t know," laughed Jack, brought up with a round turn by the hard-headed Walt.
"I do," rejoined Walt.
"What then?"
"Escape to the open air."
"You mean it?" Somehow, in his excitement, Jack had not gone as far as this daring suggestion. And yet it was, after all, the only thing to do. But suddenly another thought occurred to the boy.
"The professor and Coyote Pete, how can we leave them?"
"Well, we can"t do them any good by remaining buried here, that"s certain," replied Walt, in his sensible way.