Chapter 10

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 spacious 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 quantity 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.

Jack and Ralph nodded agreement.

"On the other hand, if this river really leads out into Mexico, we can take the subway to freedom and then, when we emerge, find out the best thing to do. Maybe we can fall in with some government troops or authorities of some kind."

"But suppose the insurrectos are in power wherever this river comes out?"

The question came from Ralph.

"We'll have to take chances on that, I suppose."

"Hark!" came suddenly from Jack.

Far back somewhere in the tunnels they had threaded they could hear loud shouts and cries. The sound of the pursuit boomed out even above the noise of the waterfall.

"They're after us!" exclaimed Jack.

"Shall we take the boat?" Walt's usually calm voice shook a little as he asked the question.

"It's our only chance. Come on, in with you, Ralph."

Ralph hesitated no longer, but jumped into the little contrivance. A sort of oar lay in the bottom. He thrust it over the side.

"The water's only about three feet deep," he announced.

"So much the less chance of our being drowned," rejoined Jack.

The lad had his knife out--a heavy-bladed hunting weapon. As soon as all was ready he would cut the ropes and set the boat free on the turbulent current.

"All right!" cried Walt, as he clambered in and took his place by Ralph.

Jack gave a hasty look around, and the next instant made a flying leap into the little craft. So fast had Black Ramon and his followers taken up the trail after they had discovered that the boys had found the secret of the hollow altar, that they were already entering the chamber.

Ramon was in the lead. The glare of the lamp fell full on his parchment-like features, as with a roar of recognition, he sighted the boys.

Ping!

Something whizzed past Jack's ear, and, chipping the rock above, showered the occupants of the boat with fragments. The sharp report of the Mexican's revolver filled the place. With a quick movement, Jack slashed the rope nearest him. If he had not been in such a hurry, he would have seen that the other should have been severed first. As it was, he had cut the one that held the boat's bow to the stream. Instantly the flat-bottomed craft swung dizzily around, and still held by her stern mooring, dashed against the bank.

For a minute the boys feared she was stove in, but there was no time to waste on an examination.

Slash!

One stroke of the knife severed the remaining rope, already drawn as taut as a piano wire. But, as Jack's knife fell, the place became filled with shouts and confusion.

Ramon had been a little in advance of his men, and now they were all in the place. A second's glance showed them what had happened. Not only were the boys about to escape, but if they did not stop them the secret of their underground route across the border would be discovered, and its usefulness at an end.

No wonder they strained every nerve to reach the boys. Ramon himself had bounded to the side of the subterranean river as the boat swung round. As her gunwale had struck the bank, he had leaped aboard. But before he could use his revolver, Walt's powerful arm knocked the weapon out of his hand, and it fell on the bottom of the boat. With a snarl of rage, Ramon flashed round on the boy. But whatever the Mexican might have been able to do with knife or pistol, he was no match for the muscles of the American lad.

Walt fairly picked the lithe form of the gun-runner from the floor of the boat as Jack's knife fell across the remaining rope. With a splash and a loud cry, Ramon pitched overside into the stream. As he fell, though, he managed to clutch the side of the craft and he hung on, desperately endeavoring to draw himself up into the boat.

His followers, seeing what had happened, rushed down on them. A tempest of bullets rattled about the boys' heads as they felt the rope part. It was no moment for sentimental hesitation. Walt raised his foot, and the next instant brought his heavy boot down with crushing force on Ramon's clinging fingers.

With a yelp of pain, the fellow let go and was rolled over and over in the river, while half a dozen of his men waded in to rescue him.

"Yip-ee-ee-ee! We're off!" yelled Jack, with a true cowboy yell. The lad was carried away by the excitement and thrill of the adventure.

With a lurch and a bump, the frail craft carrying our three young friends shot forward. The lamp-lit panorama as Ramon, dripping and cursing, was hauled out of the water by his band, flashed before their eyes for a brief moment. The next instant dense darkness fell about them.

At what seemed to be a mile-a-minute pace they were hurried forward into the unknown.