"What then?"

"Dot room behindt us contains, besides der specie, almost a ton of dynamite!"

"Great jumping wildcats!"

The exclamation dropped from Buck's lips. The others were too thunderstruck to utter a word.

"There's only one thing to do," spoke up Pete, his words fairly tumbling out of his mouth in his haste. "We must open the door and, at a signal, make a rush for it. We may never get through, but it's better than being blown up as we shall be if we remain here. The insurrectos must have left their horses somewhere near at hand. Maybe we can find them and escape."

"It's one chance in a thousand!" exclaimed Jack. "But perhaps this will be the thousandth time."

"Let us pray so!" exclaimed the professor fervently.

Buck had sprung to the door. His hand was on the bar. He knew, as did they all, that there was not an instant to lose. Their lives hung by a hair. At any moment the flames might reach the dynamite and then—annihilation, swift and terrible.

"Now!" he cried, dropping the bar. A strange light, not of fear but of determination, gleamed in his eyes.

Clang!

The bar fell to the ground, and the besieged party dashed forth, firing as they emerged.

Suddenly, from without, and just as the insurrectos espied the daring sortie, there came the shrill notes of a bugle. At the same instant a ringing cheer came over the top of the stockade.

What could it all mean? As if in a dream, the boys saw the insurrectos picking up their rifles and rushing toward the gate. But before they could reach it, a glorious sight greeted them.

A regiment of regular Mexican cavalry, the men with their carbines unslung, pouring a disastrous hail into the swarming insurrectos, suddenly swung through the shattered gateway.

Shouts and cries responded everywhere within the stockade. The terrified insurrectos dropped their rifles and ran hither and thither in mad, frenzied panic. It was every one for himself. Over the stockade they clambered, many paying toll with their lives before the carbines of Diaz's troopers.

But in the midst of the turmoil a clear, boyish voice arose.

"Back! Get back, for heaven's sake!"

The officer of the Mexican regulars heard, and wheeled his men. He recognized the thrill of warning in Jack Merrill's tones.

Stumbling forward, the suddenly relieved party of Americans darted toward the gate for their lives. On down the hillside they fled, with the cavalry surging behind and about them.

"What is it? What is the matter?" gasped the officer in English, as Jack stumbled along at his side.

The lad gasped out one word:

"Dynamite!"

Hardly had it fallen from his lips before the ground shook as if convulsed with an earthquake. A red flame shot skyward behind them, and a mighty, reverberating roar went rumbling and echoing over the countryside.

The flames had reached the explosive.

Almost at the same instant a shower of embers, debris, and odds and ends of all descriptions came showering about the retreating force. Several were cut and bruised by the shower, but none seriously.

Fortunately, also, beyond causing several of the cavalry horses to bolt in mad terror, no damage was done to the troops or our friends. The situation was rapidly explained to the wondering officer whose name was Captain Dominguez, in command of the force detailed to guard the railroad.

"We learned at Rosario that you had come to the mine," he said, in explanation of the troops' opportune arrival, "and, knowing that Madero was in the habit of raiding mines and was in the neighborhood, we made top speed to the rescue."

"And we're all mighty happy to meet you, you kin bet, captain," chimed in Buck, "but ef yer hadn't arrived when you did, we would not have had the pleasure."

"No, I can see that," rejoined the young officer, gazing off down the hillside.

In every direction could be seen Mexican troopers pursuing rebels, shooting them down, without mercy when fight was shown, in other cases, making prisoners. The rout of the insurrectos was complete and final.

Suddenly a figure on horseback was seen coming at a hard gallop toward the little group surrounding Captain Dominguez.

"It's Harding!" gasped Jack, as the figure drew closer, and indeed it was the former West Pointer. But he was in sad case. His shirt was torn almost from his back, his features blackened and seared, and a red stain showed upon his chest.

"He was in that explosion, the precious scoundrel!" grated out Buck, as his eye took in these details. "He was one of the fellers that set that fire."

Straight for the little party Harding rode. But before he reached them two Mexican troopers interposed. They raised their carbines and the next moment would have been Harding's last, but for Jack.

"Don't let them fire!" he begged.

The captain shouted an order and the troopers lowered their weapons. Straight on for the party rode Harding, toppling out of his saddle as he reached them. The fellow was badly wounded. He had been struck by a flying splinter in the explosion of the dynamite.

"Ah, a countryman of yours," remarked the captain, with a tinge of sarcasm. "You should be proud of him, senors."

But Jack was on his knees beside Harding.

"Where is my father, Harding? Tell me quick!"

"I will," gasped out the wounded man. "Madero had him tied in that grove yonder. He wished him to see the destruction of his mine, he said, and——"

The man fainted. Rascal as they knew him to be, the boys were soon applying such remedies as they could—all but Jack, that is. The boy, on Harding's pony, was off at lightning speed for the grove Harding had indicated. As he entered it, he spied Mr. Merrill tied, as Harding had said, to a tree. Of the meeting between father and son we prefer to let each reader draw his own mental picture.

"Merrill, forgive me!" breathed Harding, who had recovered from his swoon a few moments after as Jack and his father came up from the grove.

"I may forgive you, Harding," rejoined Jack, "but I can never forget."

And forgive Jack did, as he showed by interceding for the man and having him removed to a hospital near Rosario. Harding ultimately recovered and of his further movements we have no knowledge. He fared better, however, than Hickey, Divver and Rafter, who were captured by the government forces and sentenced to death by a summary court-martial.

Mr. Merrill rapidly explained that he had ridden ten miles or more from the mine with Harding before he became suspicious. He then asked Harding point blank where his son was, and the fellow's reply had been to give a peculiar whistle. Thereupon several insurrectos had leaped from the bushes and made the mine owner captive. As Harding had told Jack, Madero, with fiendish cruelty, had tied him in the grove to witness the annihilation of his own mine.

After a short pause, during which restoratives were administered to the almost exhausted Americans from the Mexican officers' field kit, they headed for the mine to ascertain what damage had been done by the explosion. Almost the first object that met their eyes as they neared the stockade was a jagged break in the structure caused by a large object that had come crashing down upon it. On closer view this proved to be the steel safe in which the gold had been placed. On opening the receptacle, everything was found intact, a fact which the makers of the safe are now using as a testimonial, as you may have noticed as you passed their Broadway store. The testimonial is signed by Conrad Geisler, who is now Mr. Merrill's partner.

Well, there is not much more to tell of this part of the Border Boys' adventures. As it may be of interest, however, to relate the further history of the underground river and the Haunted Mesa, we shall set it down here. Ramon escaped from the general disaster to the insurrectos at the Esmeralda Mine, and apparently rode straight from there to the mouth of the underground river he had long used to such good advantage. At any rate, when the boys visited it later, they found that a cunningly set explosion had completely blocked the passage for navigation, and the secret route of the forgotten race was forever closed to man. As for the Mesa, you can read all about it scientifically described in Professor Wintergreen's monograph on the subject.

The ponies and the redoubtable One Spot, Two Spot, and Three Spot were located at the Mesa, where they had been left in charge of Ramon's men. All were fat and in good condition, and Firewater was very glad to see his young master again.

By the way, Bill Whiting is now stationed in charge at the important railroad center of El Paso.

* * * * * *

"Wall," remarked Pete, as they rode toward the ranch one evening, "I guess things 'ull be quiet now fer a while."

"Hope so," rejoined Buck Bradley. "I wired Stow ter bring my show ter Maguez and you can all have free passes."

Jack thanked the genial showman on behalf of his companions, and then reminded him that Ramon was still at large, although the insurrectos were almost subjugated.

"Yes, consarn that pesky critter with the finest horse I ever set eyes on,—and while he's alive ther'll be no peace along the border."

"That's right," agreed Pete. "He's a natural born trouble-maker. But I guess so far as we are concerned we are through with him."

But Coyote Pete, accurate as were his usual judgments, was wrong in this. Black Ramon and his horse will figure again in these stories, and it will then be seen how the boys finally brought him to book for his misdeeds.

* * * * * *

The shadows are falling over the plains and the foothills are purpling in the clear twilight of the southwest. In the sunset sky the bright lone star of evening glimmers. Let us now say good night and good luck to the Border Boys till we meet them again in a new volume of their adventures to be called: "THE BORDER BOYS WITH THE MEXICAN RANGERS."

THE END